EES 21 Final (5/18)
karst topography
A type of landscape in rainy regions where there is limestone near the surface, characterized by caverns, sinkholes, and valleys
lithification of sediment: compaction
A type of lithification in which the weight of overlying material compresses more deeply buried sediment. It is most important in the fine-grained sedimentary rocks such as shale.> pores get smaller
flow
A type of movement common to mass-wasting processes in which water-saturated material moves downslope as a viscous fluid.
fall
A type of movement common to mass-wasting processes that refers to the free falling of detached individual pieces of any size.
amphibian
A vertebrate that lives part of its life on land and part of its life in water.
Stratovolcano-composite cone
A volcano composed of both lava flows and pyroclastic material
accretionary prism
A wedge-shaped mass of sediment and rock scraped off the top of a downgoing plate and accreted onto the overriding plate at a convergent plate margin.
Living on the Floodplain
Advantages It creates recreational opportunities. Such as Kayaking and fishing. Live near a good supply of water. The land where the floodplain is rich and fertile. Disadvantages No buildings or roads will be built in a floodplain area, so it restricts development. High risk of flooding.
Atmospheric structure and air pressure
Air molecules colliding with a surface cause atmospheric pressure. ... Atmospheric pressure decreases as the height of a surface above ground level increases. This is because, as the altitude increases: the number of air molecules decreases.
some of the small exoplanets recently discovered using the Kepler space telescope
All of these planets are located in the habitable zone of one of three types of stars. G-type stars are Sun-like, yellow stars having masses about 0.8 to 1.2 times the mass of the Sun, with surface temperatures of about 5800°C (about 10,000°F). Somewhat smaller, the K-type stars are orange stars with masses between 0.45 and 0.8 that of the Sun and surface temperatures of about 4000°C (about 7000°F). These stars are thought to be likely candidates to host habitable planets because they have longer life spans than Sun-like stars and emit less ultraviolet radiation, which is harmful to an organism's DNA. M-type stars are reddish in color and less than half the size of the Sun. For various reasons, they were once thought to be unlikely candidates to host habitable planets. However, because they are by far the most common type of star, they might actually be a common home for life.
The acceptance of the concept of uniformitarianism, however, meant the acceptance of a very long history for Earth.
Although Earth's processes vary in their intensity, they still take a long time to create or destroy major landscape features. For example, geologists have established that mountains once existed in portions of present-day Minnesota, Wisconsin, Michigan, and Manitoba—a region that today consists of low hills and plains. Erosion (processes that wear away land) gradually destroyed those peaks. The rock record contains evidence showing that Earth has experienced many cycles of mountain building and erosion.
early Jurassic
During the Early Jurassic, animals and plants living both on land and in the seas recovered from one of the largest mass extinctions in Earth history. On land, dinosaurs and flying pterosaurs dominated the ecosystems, and birds made their first appearance.
period
Each era of the Phanerozoic eon is further divided into time units
epochs
Each of the periods is divided into still smaller units. The epochs of other periods usually are simply termed early, middle, and late.
Earth Science IS Environmental Science
Earth Science is an environmental science that explores many important relationships btwn and the natural environment
star dunes
Dunes that are isolated hills of sand that exhibit a complex, star like form. Develop where wind patterns are changing.
parabolic dunes
Dunes that resemble barchans, except that their tips point into the wind; they often form along coasts that have strong onshore winds, abundant sand, and vegetation that partly covers the sand.
Occluded Front
a front where a warm air mass is caught between two colder air masses and brings cool temperatures and large amounts of rain and snow
Warm Front
a front where warm air moves over cold air and brings drizzly rain and then are followed by warm and clear weather
nonrenewable
any resource that forms or accumulates over such long time spans that it must be considered as fixed in total quantity
Benioff-Wadati Zones
are common to convergent plate boundaries where one plate is subducted beneath another. such dipping seismic zones indicate the angle of plate descent along a convergent plate boundary **earthquakes define a plunging plane (rigid + brittle) **materials are hot + plastic on side
Characteristics of Minerals: Generally Inorganic
inorganic crystalline solids, such as ordinary table salt (halite), that are found naturally in the ground are considered minerals
radar altimeters
bounces microwaves off sea surface from space to measure surface irregularities
Seismic discontinuities
boundaries where the velocity of seismic wave travel changes suddenly, rather than smoothly **When an earthquake occurs the seismic waves (P and S waves) spread out in all directions through the Earth's interior Sudden jumps!
coastline
boundary between shore and coast
gullies
deep ditches formed after heavy rainfall
What affects the environment of deposition?
deep v. shallow water, currents, wind, sub-aerial
submarine canyons
deep, steep-sided valleys cut into the continental slope
loess
deposits of windblown silt, lacking visible layers, generally light yellow, and capable of maintaining a nearly vertical cliff
Mineral Strength: Tenacity
describes how a mineral responds to stress—for instance, whether it tends to break in a brittle fashion or bend elastically → nonmetallic minerals such as quartz and minerals that are ionically bonded, such as fluorite and halite, tend to be brittle and fracture or exhibit cleavage when struck → native metals, such as copper and gold, are malleable, which means they can be hammered without breaking → minerals that can be cut into thin shavings, including gypsum and talc, are described as sectile → the micas, are elastic and bend and snap back to their original shape after stress is released
spheres
many separate but interacting parts that is a part of our planet's dynamic body: 1) atmosphere 2) biosphere 3) hydrosphere 4) geosphere = not isolated
Slump
mass of rock sliding down a curved surface
Erosion
material being moved or transported physically
humus
material formed from decaying leaves and other organic matter
Parent Material
material on which soil develops
Two common types of alluvial channels
meandering channels and braided channels
optical properties of minerals: Streak
streak = The color of a mineral in powdered form → A mineral's streak is obtained by rubbing it across a streak plate (a piece of unglazed porcelain) and observing the color of the mark it leaves → Streak can also help distinguish between minerals with metallic luster and those with nonmetallic luster. Metallic minerals generally have a dense, dark streak, whereas minerals with nonmetallic luster typically have a light-colored streak
Creep
slow downhill movement of weathered rock material
Solifluction
slow, downslope flow of water-saturated materials (common to permafrost areas)
foreshocks
small earthquakes that often precede a major earthquake
drumlins
streamlined asymmetrical hills composed of till
Geology
study of Earth: the study of the origin, history, and structure of Earth → traditionally divided into two broad areas: physical and historically
Why was climate warmer in Cretaceous?-
superplume increases atmospheric CO2
Soil taxonomy
system for classifying soils: There are six hierarchical categories of classification, ranging from order, the broadest category, to series, the most specific category
shale
soft, finely stratified sedimentary rock that formed from consolidated mud or clay and can be split easily into fragile slabs
residual soils
soils form from the underlying bedrock
transported soils
soils that form in place from unconsolidated sediment
Solstices and equinoxes
solctices are the longest and shortest day of the year and equinoxes are when the daylight and nightime hours are equal
crystals
solids whose particles are arranged in a lattice structure
barchan dunes
solitary, crescent-shaped, tips point downwind, limited sand supply, little vegetation, constant wind direction
stratified drift
sorted according to the size and weight of the particles. Ice is not capable of sorting the way running water can, and therefore these materials are not deposited directly by the glacier as till is but instead reflect the sorting action of glacial meltwater.
nuclear decay
spontaneous decay of certain atoms with the release of alpha, beta, or gamma particles. As time goes by, more and more of the unstable atoms decay, producing an ever-growing number of stable isotopes. Not all isotopes are unstable—there are stable isotopes, too—but here we focus on the unstable isotopes and the stable isotopes they produce.
Axial Geocentric Dipole
states that — aside from during geomagnetic reversals — the time-averaged position of the geomagnetic poles has always coincided with the geographic poles
Angle of repose
steepest stable angle
Scientific Method
the process in which researchers gather facts through observations and formulate scientific hypotheses and theories
List of sciences that collectively make up Earth Science
Geology, Oceanography, Meteorology, and Astronomy
Resources examples
water + soil, a great variety of metallic and nonmetallic minerals and energy → together they form the very foundation of modern civilization
some rocks are composed almost entirely of one mineral
A common example is the sedimentary rock limestone, which is an impure mass of the mineral calcite
Laws of thermodynamics
According to C.P Snow (British physicist): -1. you cannot win (you can't get something for nothing because matter and energy are conserved). -2. you cannot break even (you cannot return to the same energy state because entropy always increases) -3. you cannot get out of the game (because absolute zero is not attainable)
Mineral
Any naturally occurring inorganic solid that possesses an orderly crystalline structure and a definite chemical composition that allows for some variation
Rock
Any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet
Octet Rule
Atoms tend to gain, lose, or share electrons until they are surrounded by eight valence electrons
Atomic structure
Atoms, in turn, contain even smaller particles—protons and neutrons located in a central nucleus that is surrounded by electrons
What are the 3 layers of the Earth?
Core, mantle, and crust
What does the Geologic Time Scale do?
It divides the 4.6-billion-year history of Earth into many different units and provides a meaningful time frame within which the events of the geologic past are arranged.
electrons
Negatively charged particles
Atom
The smallest particle that constitute specific elements and cannot be split by chemical means • Nucleus-protons and neutrons • Atomic number (number of protons) • Electrons (in shells and orbitals) • Ions (missing or gaining electrons-net charge) • Isotopes (missing or gaining neutrons) • Atomic weight (neutrons and protons)
Mineralogy
The study of minerals
Most rocks are aggregates of several minerals
The term aggregate implies that the minerals are joined in such a way that their individual properties are retained
some rocks are composed of nonmineral matter
These include the volcanic rocks obsidian and pumice, which are noncrystalline glassy substances, and coal, which consists of solid organic debris
the compositions of some minerals can vary within specific, well-defined limits
This occurs because certain elements can substitute for others of similar size without changing the mineral's internal structure
chemical bond
a transfer or sharing of electrons that allows each atom to attain a full valence shell of electrons → Some atoms do this by transferring all their valence electrons to other atoms so that an inner shell becomes the full valence shell.
Crust
a very thin and light outer skin of Earth
Biosphere
consists of all life on Earth and all parts of the Earth in which life exists, including land, water, and the atmosphere • ocean life → includes all the life on Earth • most life on land → near the surface (tree roots)
Two Principal Divisions of Earth's Surface
continents and ocean basins
protons and neutrons
found in the nucleus & are very dense particles with almost identical masses
Resources
having a focus that is of great practical value to people (water, soil, etc.)
Sources of Energy for the Earth
• Total energy into the Earth - 174,000 x 1012 watts (terrawatts) • Largest source=solar energy - 99.967% of total - Drives all surficial processes • Geothermal - Only 32 x 1012 watts (0.018%) - Drives internal processes (earthquakes etc.) • Tidal - Only 27 x 1012 watts (0.015%)
coastal desert
cool dry air blows in from the ocean and evaporates occurs as it warms
Mass movement
gravity pulling rock and soil downhill
What happens to precipitation once it has fallen on land?
infiltration
hardpan
layer of hard material just below surface preventing good drainage
stromatolites
layered rocks that form when certain prokaryotes bind thin films of sediment together
floodways
levees are moved back and portions of floodplains are returned to wetlands or other natural habitats
near-shore zone
lies between the low-tide shoreline and the line where waves break at low tide
frontal wedging
lifting of air resulting when cool air acts as a barrier over which warmer, lighter air will rise
Lava
liquid magma that reaches the surface
Atoll formation
list the stages in the formation of an atoll 1. fringing reef develops on island 2. barrier reef forms 3. island subsides/sinks 4. atoll forms
Depositional Environments
locations where sediment accumulates
longitudinal dunes
long ridges of sand oriented parallel to the prevailing wind; these dunes form where sand supplies are limited
Deep-ocean trenches
long, relatively narrow troughs that are the deepest parts of the ocean
O horizon
loose and partly decayed organic matter
low grade metamorphism
low temperatures and low pressures
barrier islands
low, narrow, sandy islands that form offshore from a coastline •Occur along East Coast and Gulf Coast •Origin controversial -Erosional -Depositional -Post-ice age sea level rise •Suffer from flooding during large storms
zeolites
lowest temperatures and pressures
Earthquakes occur at plate boundaries
many plate boundaries do not coincide with coastlines
flowing artesian well
pressure surface is above the ground
nonflowing artesian well
pressure surface is below ground level
fractional crystallization
process in which different minerals crystallize from magma at different temperatures, removing elements from magma
soil texture
proportion of sand, silt, and clay
element
pure substance that consists entirely of one type of atom
Density stratification:
pycnocline
Chain Silicates
pyroxene, amphibole
beta decay
radioactive decay of an atomic nucleus that is accompanied by the emission of a beta particle
Monsoon
rainy season in southern Asia when the southwestern monsoon blows, bringing heavy rains
eskers
sinuous ridges of sand and gravel - deposited by glacial meltwater flowing beneath ice
Salt crystal growth
rocks split by the growth of mini crystals
Heat as a Metamorphic Agent
rocks that formed at Earth's surface experience a gradual increase in temperature and pressure as they are taken to greater depths
Migmatites (evidence of melting)
rocks that have been partially melted
Alpine-Himalayan belt
runs through the mountainous regions that flank the Mediterranean Sea and extends past the Himalaya Mountains, Tectonic activity in this region is mainly attributed to collisions of the African plate and the Indian subcontinent with the vast Eurasian plate. These plate interactions created many thrust and strike-slip faults that remain active.
methods of science
scientific knowledge is acquired thru several avenues, so it's best to describe the nature of scientific inquiry as the methods of science rather as the scientific method
Hydrogenous Sediment
seafloor sediment consisting of minerals that crystallize from seawater
regional floods
seasonal floods that typically result from spring rains or rapid melting of snow. In April 2011, unrelenting storms brought record rains to the Mississippi watershed. The Ohio Valley, which makes up the eastern portion of the Mississippi's drainage basin, received nearly 300 percent of its normal springtime precipitation. When that rainfall combined with water from the past winter's extensive and rapidly melting snowpack, the Mississippi River and many of its tributaries began to swell to record levels by early May. The resulting floods were among the largest and most damaging in nearly a century.
Archean
second oldest interval of geologic time
trunk streams
sections of the river channel network where sediment is transported **When trunk streams are in balance, the amount of sediment eroded from their banks equals the amount deposited elsewhere in the channel. Although trunk streams rework their channels over time, they are not sources of sediment, nor do they accumulate or store it.
Chemical Sedimentary Rocks: Evaporites
sediments formed by precipitation due to evaporation of water (evaporation > amount of water added) **Ex: Gypsum, Anhydrite, Halite, and Sylvite
secondary waves
seismic waves that move rock particles at right angles to the direction of the wave
surface waves
seismic waves that travel along the Earth's surface
body waves
seismic waves that travel through the Earth's interior
Dark silicate minerals: Garnet
similar to olivine in that its structure is composed of individual tetrahedra linked by metallic ions. Also like olivine, garnet has a glassy luster, lacks cleavage, and exhibits conchoidal fracture
Paleoseismology
the study of the timing, location, and size of prehistoric earthquakes
Astronomy
the study of the universe is very useful in probing the orgins of our environment
elastic rebound
the sudden release of stored strain in rocks that results in movement along a fault
wave period
the time interval between the passage of successive crests at a stationary point
Last Glacial Maximum
the time that the last major continental glacial advance in the northern hemisphere reached it maximum height 18,000 years ago
drainage basin
the total area that contributes water to a stream (aka watershed)
Slaty Cleavage
the type of foliation characteristic of slates in which there is a parallel arrangement of fine-grained metamorphic minerals
Earth System Science
the understanding of how Earth's individual components (land, water, air, and life-forms) are interconnected; the study of Earth as a system composed of subsystems (interacting parts)
zone of fracture
the upper portion of a glacier consisting of brittle ice
frost heave
the upward push caused by the expansion of freezing water
earthquake
the vibration of Earth produced by the rapid release of energy: •Earth vibration caused by rapid release of energy •Seismic waves radiate from the focus •Energy created by blocks slipping on faults •Plate tectonics explains the location of major fault zones and seismic activity
Strombolian eruption
the volcano flings globs of hot lava into the air, where they harden into volcanic bombs; noisy but mild eruptions that occur repeatedly (intermittent explosion and fountaining)
Factors Affecting Flow Velocity: Discharge
the volume of water flowing past a certain point in a given unit of time. Discharge, usually measured in cubic meters per second or cubic feet per second, is determined by multiplying a stream's cross-sectional area by its velocity. The discharge of a river system changes over time because of variations in the amount of precipitation received by the watershed. Studies show that when discharge increases, the width, depth, and flow velocity of the channel all increase predictably. As we saw earlier, when the size of the channel increases, proportionally less water is in contact with the bed and banks of the channel. Thus, friction, which acts to retard the flow, is reduced, resulting in an increase in the rate of flow.
Hydrosphere
the water portion → dynamic mass of water that is continually on the move, evaporating from the oceans to the atmosphere, precipitating to the land, and running back to the ocean again (e.g. freshwater found underground streams, lakes, and glaciers)
Rossby Waves
upper troposphere waves that play a large part in the formation of cyclones and anticyclones
Mammals
vertebrates that live on land, fur or hair covers body, live birth, warm blooded
Soil profile
vertical sequence of soil layers
metasedimentary rocks: slate
very fine-grained foliated rock composed of minute mica flakes that are too small to be visible to the unaided eye **different minerals will grow under different temps + pressures
abyssal plain
very level area of the deep-ocean floor, usually lying at the foot of the continental rise
water balance
volume of water that passes through each part of the cycle annually
Eluviation
washing out of fine soil components
Deep Water Waves
waves that move in water deeper than one-half their wavelength
triangulation
we can determine the location of an epicenter if we know the distance to it from two or more additional seismic stations. On a map or globe, we draw a circle around each seismic station with a radius equal to the distance from that station to the epicenter. The point where the three circles intersect is the approximate epicenter of the quake.
Debris flow (mudflow)
weathered debris and water flowing down a slope
angiosperms
A flowering plant which forms seeds inside a protective chamber called an ovary.
travertine
A form of limestone that is deposited by hot springs or as a cave deposit
Cold front
A front where cold air moves in under a warm air mass.
extrusive rocks (volcanic rocks)
Igneous rocks that form when lava cools on Earth's surface
process of subduction
Ocean floor sinks beneath a deep ocean trench and back into the mantle
glacial striations
Scratches and grooves on bedrock caused by glacial abrasion
ultimate base level
Sea level; the lowest level to which stream erosion could lower the land.
Terrigenous Sediment
Sediment derived from the land and transported to the ocean by wind and flowing water.
biogenous sediment
Sediment that is made up of the skeletons and shells of marine organisms.
Saltation
Small pebbles and stones are bounced along the river bed
aftershocks
Smaller earthquakes that follow a major earthquake.
3 major regions of the Ocean Floor
1) continental margins 2) deep-ocean basins 3) oceanic (mid ocean) ridges
Stages in Ocean Basin Formation
(1) The upper crust is deformed by ductile stretching while the lower crust is broken along normal faults (2) tension pulls apart the crusts and crust slab sink in the middle, forming a rift valley (3) continued spreading creates a narrow sea (4) after continued spreading, an ocean and ridge system are created.
Geologists divide glacial drift into two distinct types:
(1) materials deposited directly by the glacier, which are known as till, and (2) sediments laid down by glacial meltwater, called stratified drift.
The amount of damage to human-made structures attributable to the vibrations depends on several factors
(1) the intensity and (2) duration of the vibrations as well as (3) the nature of the material on which structures rest and (4) the building materials and construction practices of the region
The amount of water that runs off rather than soaking into the ground depends on several factors:
(1) the intensity and duration of rainfall, (2) the amount of water already in the soil, (3) the nature of the surface material, (4) the slope of the land, and (5) the extent and type of vegetation.
Natural resources are typically grouped into broad categories according to....
(1) their ability to be regenerated (renewable or nonrenewable) or (2) their origin or type
The height, length, and period that are eventually achieved by a wave depend on three factors:
(1) wind speed, (2) length of time the wind has blown (duration), and (3) fetch, the distance that wind has traveled across open water
terrestrial planets
(Earth-like planets) that orbit within the habitable zone, with conditions roughly comparable to those of Earth and, thus, favorable to supporting Earth-like life. The planet Venus offers a sobering view of the importance of the habitability zone. In terms of size, mass, and composition, Venus is nearly Earth's twin. However, it orbits a little closer to the Sun than does Earth—and its atmosphere has evolved into a thick blanket that keeps temperatures at the surface hot enough to melt lead and, therefore, most certainly too hot to sustain life.
Igneous rock: basaltic composition
(aka mafic) a compositional group of igneous rocks indicating that the rock contains substantial dark silicate minerals and calcium-rich plagioclase feldspar
Density
(an important property of matter) mass per unit volume
Carbonic acid
(in rain) breaks down chemical composition of rocks
The first organisms to inhabit Earth came into existence roughly 3.8 billion years ago. From that point in Earth's history, innumerable changes occurred: Life-forms came and went, and the physical environment of our planet was transformed in many ways. Consider two of the many timely Earth-altering events:
- Earth's atmosphere has developed over time. Earth's primitive atmosphere is thought to have been composed mostly of nitrogen, water vapor, methane, and carbon dioxide—but no free oxygen, that is, oxygen not combined with other elements. Fortunately, microorganisms evolved that released oxygen into the atmosphere through the process of photosynthesis. About 2.5 billion years ago, an atmosphere with free oxygen came into existence. The result was the evolution of the ancestors of the vast array of multicellular organisms that we find on Earth today. - About 66 million years ago, our planet was struck by an asteroid 10 kilometers (6 miles) in diameter. This impact contributed to a mass extinction that obliterated nearly three-quarters of all plant and animal species—including dinosaurs (Figure 12.2).† Although it may not seem lucky, the extinction of dinosaurs opened new habitats for small mammals that survived the impact. These habitats, along with evolutionary forces, led to the development of the many large mammals that occupy our modern world. Without this event, mammals might have remained mostly small and inconspicuous.
A primary factor that determines whether a planet is habitable is its location with respect to its host star. The following scenarios substantiate Earth's advantageous position:
- If Earth were about 10 percent closer to the Sun, our atmosphere would be more like that of Venus and consist mainly of the greenhouse gas carbon dioxide. Earth's surface temperature would then be too hot to support higher life-forms. - If Earth were about 10 percent farther from the Sun, the problem would be reversed: It would be too cold. The oceans would freeze over, and Earth's active water cycle would not exist. Without liquid water, all life would perish. - Earth is near a star of modest size. Stars like the Sun have a life span of roughly 10 billion years and emit radiant energy at a fairly constant level during most of this time. Giant stars, on the other hand, consume their nuclear fuel at very high rates and "burn out" in a few hundred million years. Therefore, Earth's proximity to a modest-sized star allowed enough time for the evolution of humans, who first appeared on this planet only a few million years ago.
Some of the most common types of hydrogenous sediment include the following:
- Manganese nodules are rounded, hard lumps of manganese, iron, and other metals that precipitate in concentric layers around a central object (such as a volcanic pebble or a grain of sand). The nodules can be up to 20 centimeters (8 inches) in diameter and are often littered across large areas of the deep seafloor (Figure 13.19A). - Calcium carbonates form by precipitating directly from seawater in warm climates. If this material is buried and hardened, it forms limestone. Most limestone, however, is composed of biogenous sediment. - Metal sulfides are usually precipitated as coatings on rocks near black smokers associated with the crest of a mid-ocean ridge (Figure 13.19B). These deposits contain iron, nickel, copper, zinc, silver, and other metals in varying proportions. - Evaporites form where evaporation rates are high and there is restricted open-ocean circulation. As water evaporates from such areas, the remaining seawater becomes saturated with dissolved minerals, which then begin to precipitate. Heavier than seawater, these crystals sink to the bottom or form a characteristic white crust of evaporite minerals around the edges of these areas. Evaporites are collectively termed salts; some evaporite minerals taste salty, such as halite (common table salt, NaCl), and some do not, such as the calcium sulfate minerals anhydrite (CaSO4) and gypsum (CaSO4 · 2H2O)
These all add together to control timing of glaciations and interglacials
- Precession of the Equinoxes (when the equinoxes occur during a year -Tilt of Earth's axis to orbital plane -Eccentricity of Earth's orbit around the sun
How do we know the properties of the geomagnetic field in the past?
- Rocks record past magnetic fields! *Paleomagnetism*- when igneous/metapmorphic rocks cool below their "Curie" temperature, they lock in the prevailing geomagnetic field at that TIME and LOCATION
Silicate Structures
- single chain - double chain - sheet - 3-D networks
Laws of Thermodynamics
-1st law: • energy is neither created nor destroyed-just changed from one type to another -2nd law: • entropy (disorder) increases-that is, energy always changes from more concentrated form (more useful) to less concentrated form (less useful) - 3rd law: •entropy of a system approaches a constant as temperature gets toward absolute zero
Four Interacting Reservoirs
-Atmosphere -Hydrosphere -Biosphere -Geosphere
hurricanes
-Big low pressure areas -Cyclones -Need high sea surface temperature to form -Latent heat gives energy
hornfels facies
-High increase of temperature due to contact metamorphism -The mineralogical composition depends of the parent material
Types of systems
-Isolated (no energy or matter in or out) -Closed (no matter exchange, but energy can) -Open (what happens for Earth systems we study....but not planet as a whole)
Basin and Range
-This extreme landscape of short, parallel mountain ranges and desert basins extends along the eastern border of California ---The northern section is part of a lava plateau ---The southern section is generally dry. The Mojave Desert is the major geographical feature in the south. -The Northwest and Southwest Great Basin, the Northwestern Sonoran Desert, and the Salton Sea Trough are significant areas in this region -Death Valley (in the Mojave Desert), the lowest point in the U.S., was formed by faulting (not erosion) -The system extends in to Nevada and Utah -Irrigation with water from the Colorado River has allowed large-scale farming in the Imperial and Coachella valleys
Mountain and Valley Winds
-valley gains heat rapidly during day -mountain air cools rapidly at night *warm air rises during day and cool air subsides downslope at night
Formation of sand dunes
1) A large amount of loose sand in an area with little vegetation 2) A wind or breeze to transport grains of sand 3) Obstacle that cause the sand to lose momentum and settle: Sand dunes are created when wind deposits sand on top of each other until a small mound starts to form. Once that first mound forms, sand piles up on the windward side more and more until the edge of the dune collapses under its own weight.
Acquiring Paleomagnetic Data
1) Drilling paleomagnetic cores 2) Orienting Cores 3) Measurement (direction of magnetism) 4) Demagnetization
East African Rift Valley
1) Plumes of magma enter crust Weaken Rock strata Tension created as it pulls apart Fault lines 2) Land subsided (form largest rift valley in the world) Flat floor ... steep sides... steep scarps Some places - 150 m below sea level
The world ocean can be divided into four main ocean basins
1) The Pacific Ocean, which is the largest ocean and the largest single geographic feature on the planet, accounts for more than one-third of all surface area on Earth and over half of the ocean surface area of Earth. In fact, the Pacific Ocean is so large that all the continents could fit into the space occupied by it—and have room left over! It is also the world's deepest ocean, with an average depth of 3940 meters (13,000 feet, or about 2.5 miles). 2) The Atlantic Ocean is about half the size of the Pacific Ocean and is not quite as deep. It is a relatively narrow ocean compared to the Pacific and is bounded by nearly parallel continental margins. 3) The Indian Ocean is slightly smaller than the Atlantic Ocean but has about the same average depth. Unlike the Pacific and Atlantic Oceans, it is largely a Southern Hemisphere water body. 4) The Arctic Ocean is about 7 percent the size of the Pacific Ocean and is only a little more than one-quarter as deep as the rest of the oceans.
Any theory that attempts to explain the causes of ice ages must successfully answer two basic questions:
1)What causes the onset of glacial conditions? For continental ice sheets to have formed, average temperature must have been somewhat lower than at present and perhaps substantially lower than throughout much of geologic time. Thus, a successful theory would have to account for the cooling that finally leads to glacial conditions. 2)What caused the alternating glacial and interglacial stages that have been documented for the Quaternary period? Whereas the first question deals with long-term trends in temperature on a scale of millions of years, this question relates to much shorter-term changes
Three mechanisms of heat transfer
1. Conduction 2. Convection 3. Radiation
Characteristics of Minerals
1. Naturally occurring 2. Generally inorganic 3.Solid substance 4.Orderly crystalline structure 5.Definite chemical composition that allows for some variation
Formation of the Solar System
1. The young solar begins to collapse 2. The solar nebula rotates, flattens, and becomes warmer in the center 3. Planetesimals begin to form within the swirling disk 4. As the largest planetesimals grow in size, their gravity attracts more gas and dust 5. Smaller planetesimals collide with the larger ones and planets begin to grow 6. A Star is born and the remaining gas and dust blown out of the new solar system
Measuring relative humidity
1.Wet bulb and dry bulb thermometers 2.Evaporation from wet bulb will cool that thermometer 3.Amount of cooling (evaporation) will determine temperature diff. 4.The greater the temp. diff between thermometers the lower the relative humidity.
sandy clay
40% clay, 5% silt, and 55% sand.
What happens when unstable atoms break apart?
> Alpha particles (α particles) may be emitted from the nucleus. An alpha particle is composed of 2 protons and 2 neutrons. Thus, the emission of an alpha particle means that the mass number of the isotope is reduced by 4, and the atomic number is lowered by 2. >When an electron (often confusingly referred to as a "beta particle," or β particle), is emitted from a nucleus, the mass number remains unchanged because electrons have practically no mass. However, the electron is produced when a neutron (which has no charge) decays to produce the electron plus a proton. Because the nucleus now contains one more proton than before, the atomic number increases by 1. It's no longer the same element! >Sometimes an electron is captured by the nucleus. The electron combines with a proton and forms an additional neutron. As in the last example, the mass number remains unchanged. However, because the nucleus now contains one fewer proton, the atomic number decreases by 1.
seawall
A barrier constructed to prevent waves from reaching the area behind the wall. Its purpose is to defend property from the force of breaking waves.
transform plate boundary
A boundary in which two plates slide past one another without creating or destroying lithosphere.
Cambrian explosion
A burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history; recorded in the fossil record about 545 to 525 million years ago.
collapse caldera
A caldera formed primarily as a result of collapse due to withdrawal of magmatic support.
Pater noster lakes
A chain of small lakes in a glacial trough that occupies basins created by glacial erosion.
How a hot spot track is formed
A chain of volcanoes (hotspot track) forms as a tectonic plate moves over a plume of hot mantle material (hotspot) rising from deep within the Earth **Hot spot tracks are due to mantle plumes
covalent bond
A chemical bond formed by the sharing of one or more valence electrons between a pair of atoms
Emergent coasts
A coast where the land is rising relative to sea level or sea level is falling relative to the land.
trilobites
A common animal that lived in Earth's oceans during the Paleozoic Era. They are most closely related to the modern Horseshoe Crab.
Igneous rock: andesitic composition (intermediate composition)
A compositional group of igneous rocks that contains at least 25 percent dark silicate minerals. The other dominant mineral is plagioclase feldspar.
economic minerals
A concentration of a mineral resource or reserve that can be profitably extracted from Earth
stalagmite
A cone-shaped calcite deposit that builds up from the floor of a cave
alluvial fan
A fan-shaped deposit of sediment formed when a stream's slope is abruptly reduced
rock flour
A fine sediment of pulverized rock produced by glacial erosion
banded iron formations
A finely layered iron and silica-rich (chert) layer deposited mainly during the Precambrian
stream terraces
A flat, benchlike structure produced by a stream, which was left elevated as the stream cut downward.
spring
A flow of groundwater that emerges naturally at the ground surface
environment of deposition
A geographic setting where sediment accumulates. Each site is characterized by a particular combination of geologic processes and environmental conditions.
What is a geomagnetic reversal?
A geomagnetic reversal is a change in Earth's magnetic field such that the positions of magnetic north and magnetic south are interchanged. The cause is still UNKNOWN but it comes from the outer core
tsunami
A giant wave usually caused by an earthquake beneath the ocean floor.
Retreating glacier
A glacier where the edge moves back in a year because more snow has melted than been added.
sand dune
A hill of sand, made and shaped by wind
Supercontinent
A large landmass that contains all, or nearly all, of the existing continents.
gyres
A large-scale pattern of water circulation that moves clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere
desert pavement
A layer of coarse pebbles and gravel created when wind removed the finer material.
terminal end moraine
A long hill of glacial till, left by a glacier at the point of its farthest advance.
rift valley
A long, narrow trough bounded by normal faults. It represents a region where divergence is taking place.
Comparing the Oceans to the Continents
A major difference between continents and ocean basins is their relative levels. The average elevation of the continents above sea level is about 840 meters (2756 feet), whereas the average depth of the oceans is nearly four and a half times this amount—3729 meters (12,234 feet, or about 2.5 miles). The volume of ocean water is so large that if Earth's solid mass were perfectly smooth (level) and spherical, the oceans would cover Earth's entire rocky surface to a uniform depth of more than 2000 meters (1.2 miles)!
San Andreas Fault
A major geological fault in California formed by a sliding transform boundary.
Meta-Igneous Rocks: Granulite
A medium- to coarse-grained granoblastic rock formed under conditions of relatively high pressure and temperature.
Cephalopods
A member of a group of molluscs that include squids and octopus
placoderms
A member of an extinct group of fishlike vertebrates that had jaws and were enclosed in a tough outer armor.
zeolite facies
A metamorphic facies formed at relatively low temperature and pressure where zeolite minerals are stable.
blueschist
A metamorphic rock formed under high pressures and moderate temperatures, often containing glaucophane, a blue amphibole
Metasomatic Rock
A metamorphic rock whose whole bulk chemical composition was altered during interaction with fluids
Seismic Tomography
A method that uses the seismic waves from earthquakes recorded on thousands of seismographs all over the world to sweep Earth's interior in many different directions and construct a three-dimensional image of what's inside.
loam
A mixture of gravel, sand, silt, clay, and organic matter
moraines
A mound, ridge, or mass of material that were left on the ground by a receding glacier.
slides
A movement common to mass-wasting processes in which the material moving downslope remains fairly coherent and moves along a well-defined surface.
alpha decay
A nuclear reaction in which an atom emits an alpha particle consisting of two protons and two neutrons. This increases the atomic number by 2 and the mass number by 4.
Jetties
A pair of structures extending into the ocean at the entrance to a harbor or river that are built for the purpose of protection against storm waves and sediment deposition.
Thermoremanent magnetization: TRM-igneous rocks
A permanent magnetization acquired by minerals in igneous rocks when groups of atoms of the mineral align themselves in the direction of the magnetic field that existed when the material was hot. When the material has cooled, these atoms are locked in place and therefore are always magnetized in the same direction.
Triple junction
A point where three lithosphere plate boundaries intersect
Principle of Fossil Succession
A principle by which fossil organisms succeed one another in a definite and determinable order, and any time period can be recognized by its fossil content. Based on Smith's classic observations and the findings of many later geologists, one of the most important and basic principles in historical geology was formulated: Fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content
Principle of Original Horizontality
A principle by which layers of sediment are generally deposited in a horizontal or nearly horizontal position. Thus, if we observe rock layers that are flat, we know that they have not been disturbed and still have their original horizontality. The layers in the Grand Canyon illustrate this. Thus, if we observe rock layers that are flat, we know that they have not been disturbed and still have their original horizontality. The layers in the Grand Canyon illustrate this. Thus, if we observe rock layers that are flat, we know that they have not been disturbed and still have their original horizontality. The layers in the Grand Canyon illustrate this
Carbonization and Impressions
A type of fossilization called carbonization is particularly effective at preserving leaves and delicate animal forms. It occurs when fine sediment encases the remains of an organism. As time passes, pressure squeezes out the liquid and gaseous components and leaves behind a thin residue of carbon. Black shale deposited as organic-rich mud in oxygen-poor environments often contains abundant carbonized remains. If the film of carbon is lost from a fossil preserved in fine-grained sediment, a replica of the surface, called an impression, may still show considerable detail
Principle of Lateral Continuity
A principle which states that sedimentary beds originate as continuous layers that extend in all directions until they grade into a different type of sediment or thin out at the edge of a sedimentary basin. For example, when a river creates a canyon, we can assume that identical or similar strata on opposite sides once spanned the canyon. Although rock outcrops may be separated by a considerable distance, the principle of lateral continuity tells us that those outcrops once formed a continuous layer. This principle allows geologists to relate rocks in isolated outcrops to one another. Combining the principles of lateral continuity and superposition lets us extend relative age relationships over broad areas. This process, called correlation
Internal process
A process such as mountain building or volcanism that derives its energy from Earth's interior and elevates Earth's surface.
external processes
A process such as weathering, mass wasting, or erosion that is powered by the Sun and transforms solid rock into sediment.
horns
A pyramid-like peak formed by glacial action in three or more cirques surrounding a mountain summit. A famous example is the Matterhorn in the Swiss Alps.
Geomagnetic Polarity Time Scale
A record of the onset and duration of the multitude of episodes of reversal of the Earth's magnetic polarity, or geomagnetic polarity reversals. The time scale has been accurately extended back to the Upper Jurassic, the age of oldest existing oceanic crust.
circular orbital motion
A reference to the movement of water in a wave. As a wave travels, energy is passed along by moving in a circle. The waveform advances but the water does not advance appreciably.
Glaciated terrain
A region that once bore great masses of glacial ice; a distinguishing feature is marks of glaciation.
tombolo
A ridge of sand that connects an island to the mainland or to another island
wave-cut cliffs
A seaward-facing cliff along a steep shoreline formed by wave erosion at its base and mass wasting.
conglomerate
A sedimentary rock composed of rounded gravel-size particles.
transverse dunes
A series of long ridges oriented at right angles to the prevailing wind; these dunes form where vegetation is sparse and sand is very plentiful.
Vulcanian Eruption
A short, violent, relatively small eruption of lava; can propel pyroclastic material 800 mph and 10 miles in the air; can have a violent, cannon-like expulsion of the "plug" (very explosive)
light silicate minerals
A silicate mineral that lacks iron and/or magnesium. Light silicates are generally lighter in color and have lower specific gravities than dark silicates.
Cenozoic Era
A span on the geologic time scale beginning about 65 million years ago following the Mesozoic era.
Mesozoic Era
A span on the geologic time scale between the Paleozoic and Cenozoic eras from about 248 million to 65 million years ago.
Paleozoic era
A span on the geologic time scale between the eons of the Precambrian and Mesozoic era from about 540 million to 248 million years ago.
cinder cone
A steep, cone-shaped hill or small mountain made of volcanic ash, cinders, and bombs piled up around a volcano's opening
Factors Affecting Flow Velocity: Channel Shape, Size, and Roughness
A stream's channel is a conduit that guides the flow of water, but the water encounters friction as it flows. The shape, size, and roughness of the channel affect the amount of friction. Larger channels have more efficient flow because a smaller proportion of water is in contact with the channel. A smooth channel promotes a more uniform flow, whereas an irregular channel filled with boulders creates enough turbulence to slow the stream significantly.
breakwater
A structure protecting a nearshore area from breaking waves.
Rodinia
A supercontinent older than Pangaea that formed about 1.1 billion years ago and began to break up about 750 million years ago.
Pannotia
A supercontinent that existed during the Neoproterozoic.
playa lake
A temporary lake that forms on a playa from runoff after a rainstorm or during a wet season.
Igneous rock: fine-grained texture
A texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished with the unaided eye.
Theory of Plate Tectonics
A theory stating that Earth's lithosphere is broken into huge plates that move and change in size over time.
diurnal tide
A tidal cycle of one high tide and one low tide per day.
Great Oxygenation Event
A time about 2.5 billion years ago, when a significant amount of oxygen appeared in the atmosphere. One positive benefit of the Great Oxygenation Event is that, when struck by sunlight, oxygen molecules form a compound called ozone (O3), a type of oxygen molecule composed of three oxygen atoms. Ozone, which absorbs much of the Sun's harmful ultraviolet radiation before it reaches Earth's surface, is concentrated between 10 and 50 kilometers (6 and 30 miles) above Earth's surface, in a layer called the stratosphere.
rills
A tiny groove in soil made by flowing water
outlet glaciers
A tongue of ice normally flowing rapidly outward from an ice cap or ice sheet, usually through mountainous terrain to the sea.
Fracture zones and transform faults
A transform fault may occur in the portion of a fracture zone that exists between different offset. Oceanic ridges offset by transform faults and fracture zones
Normal Fault (Tensional Stress)
A type of fault where the hanging wall slides downward; caused by tension in the crust
optical properties of minerals: Color
Although color is generally the most conspicuous characteristic of any mineral, it is considered a diagnostic property of only a few minerals. Slight impurities in the common minerals fluorite and quartz, for example, give them a variety of tints, including pink, purple, yellow, white, gray, and even black. → the use of color as a means of identification is often ambiguous or even misleading
invertebrate
An animal without a backbone. All major invertebrate (animals lacking backbones) groups became widespread during the Cambrian, including jellyfish, sponges, worms, mollusks (such as clams and snails), and arthropods (such as insects and crabs)
bajada
An apron of sediment along a mountain front created by the coalescence of alluvial fans.
Stress changes caused by earthquake
An earthquake alters the shear and normal stress on surrounding faults. New evidence strengthens the hypothesis that such small, sudden stress changes cause large changes in seismicity rate. Rates climb where the stress increases (aftershocks) and fall where the stress drops.
glacial erratics
An ice-transported boulder that was not derived from the bedrock near its present site.
Igneous rock: porphyritic texture
An igneous rock texture consisting of large crystals embedded in a matrix of much smaller crystals
Igneous rock: coarse-grained texture
An igneous rock texture in which the crystals are roughly equal in size and large enough so that individual minerals can be identified with the unaided eye.
sea stack
An isolated mass of rock standing just offshore, produced by wave erosion of a headland.
till
An unsorted and unstratified accumulation of glacial sediment, deposited directly by glacier ice.
the parent atom
An unstable (radioactive) isotope
hard stabilization
Any form of artificial structure built to protect a coast or to prevent the movement of sand along a beach. Examples include groins, jetties, breakwaters, and seawalls.
foliation
Any nearly flat arrangement of mineral grains or structural features within a rock
country rock
Any rock that was older than and intruded by an igneous body.
Spheroidal weathering
Any weathering process that tends to produce a spherical shape from an initially blocky shape
Formation of Ayers Rock (Uluru)
Around 500 million years ago, the whole area became covered in sea. Sand and mud fell to the bottom and covered the seabed, including these fans. The weight of the new seabed turned the fans into rock. The sandy fan became sandstone (Uluru) while the rocky fan became conglomerate rock (Kata Tjuta).
Asperities on fault surface cause "stick-slip" behavior
As a fault repeatedly ruptures, the asperities can be worn down, creating fault gouge and smoothing the fault. The gouge material often decomposes to a fine clay and forms a thin layer which "greases" the fault for easier sliding.
Grade of metamorphism
As a rock is buried to greater depths it is subject to greater temperatures and pressures causing recrystallization into higher grade rocks.
unloading
As igneous bodies cool and are uplifted, overlying pressure decreases and the body expands
Evolution of the Atmosphere
As it has developed: -CO2 levels have decreased because: Fossil fuels store them, oceans absorb them, photosynthesis. -Oxygen levels have increased: Photosynthesis.
How to make a collapse caldera
As more magma was erupted, cracks opened up around the summit, which began to collapse. Fountains of pumice and ash surrounded the collapsing summit, and pyroclastic flows raced down all sides of the volcano.
NASA's Kepler telescope
As of 2016, this space telescope had identified more than 2000 exoplanets and numerous planetary candidates. One goal of the Kepler mission is to survey nearby sections of the Milky Way in search of Earth-size planets orbiting in or near the habitable zone of planetary systems.
Abrasion
As the ice and its load of rock fragments slide over bedrock, they function like sandpaper, smoothing and polishing the surface below.
Goldilocks scenario
As various observers have noted, Earth developed under "just right" conditions to support higher life-forms. Astronomers refer to this as the Goldilocks scenario. Like the classic "Goldilocks and the Three Bears" fable, Venus is too hot (Papa Bear's porridge), and Mars is too cold (Mama Bear's porridge), but Earth is just right (Baby Bear's porridge).
Mt. Denali
At 20,310 feet above sea level, it is the highest point in North America and experiences some of the most severe weather in the world. Many consider Denali to be the world's coldest mountain because of its combination of high elevation and its subarctic location at 63 degrees north latitude.(valley glaciers)
Headward erosion: Canyonlands National Park, Utah
At Canyonlands National Park in Utah, sheets of water flow across the plains and enter the canyons. As they do so, the top edge of the canyon erodes back into the plain above, both lengthening and widening the canyon.
Formation of angular unconformity
At an angular unconformity, the older rock layers are deformed, tilted, and usually slightly eroded before the deposition of a new rock layer.
Sedimentary Structures: channels
Caused by stream meandering across floodplain
Atmospheric structure and Temperature
Atmospheric layers are characterized by variations in temperature resulting primarily from the absorption of solar radiation; visible light at the surface, near ultraviolet radiation in the middle atmosphere, and far ultraviolet radiation in the upper atmosphere.
How rapidly does glacial ice move?
Average rates vary considerably from one glacier to another. Some glaciers move so slowly that trees and other vegetation may become well established in the debris that accumulates on the glacier's surface. Others advance up to several meters each day.
Sedimentary Structures: Varves
Bands of alternating light and dark colored sediments of sand, clay, and silt: • Rhythmic, annual layering • Clay winter, silt summer **formed in lakes, cold climates
Fresh groundwater floats on saline groundwater
Because fresh water is less dense than salt water it floats on top. ... Under normal conditions fresh water flows from inland aquifers and recharge areas to coastal discharge areas to the sea. In general, groundwater flows from areas with higher groundwater levels (hydraulic head) to areas with lower groundwater levels.
Asthenosphere and Lithosphere
Because the asthenosphere and lithosphere are mechanically detached from each other, the lithosphere is able to move independently of the asthenosphere.
Marine record of glaciations
Because the latter is directly related to the volume of ice on land, the marine oxygen isotope record is primarily a record of past glaciations on the continents. An isotopic record from the North Atlantic suggests the first major glaciation in that region occurred about 2,400,000 years ago.
the hydrologic cycle is balanced
Because the total amount of water vapor in the atmosphere remains about the same, the average annual precipitation worldwide must be equal to the quantity of water evaporated. However, for all the continents taken together, precipitation exceeds evaporation. Conversely, over the oceans, evaporation exceeds precipitation. Because the level of the world ocean is not dropping, the system must be in balance. Balance is achieved because 36,000 cubic kilometers (8600 cubic miles) of water annually makes its way from the land back to the ocean.
belemnite marls
Belemnites are probably the most common fossils found on the beaches, especially around Charmouth. When the animal was alive, the pencil or bullet-shaped shell was surrounded by a soft body, and the creature looked very like a squid. Like ammonites, belemnites belong to the group known as cephalopods.
Distribution of land and water
Between latitudes 45° north and 70° north, there is actually more land than water, whereas between 40° south and 65° south, there is almost no land to interrupt oceanic and atmospheric circulation.
The most prominent features of a V-shaped valley are rapids and waterfalls.
Both occur where the stream's gradient increases significantly, a situation usually caused by variations in the erodibility of the bedrock into which a stream channel is cutting. Resistant beds create rapids by acting as a temporary base level upstream while allowing downcutting to continue downstream. In time, erosion usually eliminates the resistant rock. Waterfalls are places where the stream makes an abrupt vertical drop.
Brittle and Ductile Behavior
Brittle deformation: Irreversible strain when rocks break in pieces in response to stress. Any material that breaks into pieces exhibits brittle behavior. Ductile deformation: when rocks flow or bend in response to stress (ex. clay)
Confining Pressure and Differential Stress as Metamorphic Agents
Buried rocks are subjected to confining pressure—similar to water pressure in that the forces are equally applied in all directions (Figure 3.28A). The deeper you go in the ocean, the greater the confining pressure. The same is true for buried rock. Confining pressure causes the spaces between mineral grains to close, producing a more compact rock that has greater density. Further, at great depths, confining pressure may cause minerals to recrystallize into new minerals that display more compact crystalline forms.
the path from parent to daughter atom
But the path from parent to daughter isn't always direct. Uranium-238, one of the most important isotopes for geologic dating, provides an example of the complexity. When the radioactive parent, uranium-238 (atomic number 92, mass number 238) decays, it follows a number of steps, emitting a total of 8 alpha particles and 6 electrons before finally becoming the stable daughter product lead-206 (atomic number 82, mass number 206).
Glacial striations-Lake Superior
By about 2 millions years B.P. it was cold enough for glaciers to form in North America. The shorelines of modern Lake Superior started to develop almost 10,000 years (B.P.) ... 9,500 Years Ago, The glaciers towered several kilometres above the ground, and the massive weight of the ice pushed the earth's crust down.
Sonar and bathymetry (post WWII)
By conducting a multibeam sonar survey similar to a medical ultrasound, scientists are able to image the sea-bottom. Bathymetric data can be applied in several ways, from water transportation or biological oceanography to the study of climate change.
Extent of Ice Age Glaciation
By the beginning of the twentieth century, geologists had largely determined the extent of Ice Age glaciation. Further, they discovered that many glaciated regions had not one but several layers of drift. Close examination of these older deposits showed well-developed zones of chemical weathering and soil formation, as well as the remains of plants that require warm temperatures. The evidence was clear: There had not been just one glacial advance but several, each separated by an extended period when climates were as warm as or warmer than at present. The Ice Age was not simply a time when the ice advanced over the land, lingered for a while, and then receded. Rather, it was a complex period characterized by a number of advances and withdrawals of glacial ice. The glacial record on land is punctuated by many erosional gaps. This makes it difficult to reconstruct the episodes of the Ice Age.
First motion studies
Can determine movement direction if fault orientation is known
burgess shale
Canadian fossil formation that contains Cambrian soft-bodied organisms as well as organisms with hard parts.
Sedimentary Structures: turbidites
Caused by turbidity flows in marine or lake settings **graded layers of terrigeneous sand interbedded with finer pelagic sediments of the deep sea floor
prokaryotes
Cells that do not contain nuclei
types of glaciers
Cirque, Valley, Ice Cap, Fjord, Piedmont
Rock characteristics: climate
Climate elements, particularly temperature and precipitation, are crucial to the rate of rock weathering. For example, the frequency of freeze-thaw cycles greatly affects the amount of frost wedging. Temperature and precipitation also exert a strong influence on the rates of chemical weathering and on the kind and amount of vegetation present. Regions with lush vegetation generally have a thick mantle of soil rich in decayed organic matter from which carbonic and other acids are derived.
soil formation: climate
Climate is the most influential control of soil formation. Temperature and precipitation are the elements that exert the strongest impact on soil formation. Variations in temperature and precipitation determine whether chemical or mechanical predominates. They also greatly influence the rate and depth of weathering. The amount of precipitation influences the degree to which various materials are removed from the soil, thereby affecting soil fertility. Climate conditions are important factors controlling the type of plant and animal life present.
Altostratus
Clouds at mid-level that form a light sheet that lets the sun or moon show as a bright spot.
Nimbostratus
Clouds that are low-level, uniform layer, usually very dark, that bring strong precipitation
shield volcano v. composite volcano
Composite volcanoes are tall, steep cones that produce explosive eruptions. Shield volcanoes form very large, gently sloped mounds from effusive eruption
Controls and Triggers of Mass Movement: Earthquakes as Triggers
Conditions favoring mass movement can exist in an area for a long time without movement occurring. An additional factor is sometimes necessary to trigger the movement. Among the most important and dramatic triggers are earthquakes. An earthquake and its aftershocks can dislodge enormous volumes of rock and unconsolidated material.
What are some of the characteristics that make Earth unique among the planets of our solar system?
Consider the following: - If Earth were considerably larger (more massive), its force of gravity would be proportionately greater. Like the giant planets, Earth might have retained a thick, hostile atmosphere consisting of ammonia and methane, and possibly hydrogen and helium. - If Earth were significantly smaller, oxygen, water vapor, and other volatiles would escape to space and be lost forever. Thus, like the Moon and Mercury, both of which lack appreciable atmospheres, Earth would be devoid of life. - If Earth did not have a rigid lithosphere overlaying a weak asthenosphere, plate tectonics would not operate. The continental crust (Earth's "highlands") would not have formed without the recycling of plates. Consequently, the entire planet would likely be covered by an ocean a few kilometers deep. As author Bill Bryson so aptly stated, "There might be life in that lonesome ocean, but there certainly wouldn't be baseball."* - Most surprising, perhaps, is the fact that if our planet did not have a molten metallic outer core, most of the life-forms on Earth would not exist. Fundamentally, without the flow of iron in the core, Earth could not support a magnetic field. It is the magnetic field that prevents lethal cosmic rays from showering Earth's surface and stripping away our atmosphere.
fault breccia
Created from crushing rocks near the surface to create angular fragments
Formation of cross beds
Cross beds form through the continual shifting of sands. Wind erodes one side of a bedform to deposit it on the other side. Gravity also plays a part as it pulls sediment down the slip face. The slip face determines the shape of the cross bed.
Layering in the Earth
Crust, mantle, core, lithosphere, asthenosphere, mesosphere, outer core, inner core.
Snell's Law
Curving ray paths due to refraction - The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for a given frequency.
How do we know the structure of oceanic lithosphere?
Cyprus and East African Rift Valley
Rock Deformation
Deformation can be: •Brittle •Ductile •Factors that effect type of deformation: •Confining pressure •Temperature •Time (strain rate) •Rock type
Amber
Delicate organisms, such as insects, are difficult to preserve, and consequently they are relatively rare in the fossil record. However, amber—the hardened resin of ancient trees—can preserve them in exquisite three-dimensional detail. Resin sealed off the insect from the atmosphere and protected the remains from damage by water and air. As the resin hardened, a protective pressure-resistant case was formed.
Geologic Processes in Arid Climates: the role of water
Deserts have scant precipitation and few major rivers. Nevertheless, water plays an important role in shaping landscapes in dry regions. Permanent streams are normal in humid regions, but almost all desert streams are dry most of the time.
Sedimentary Structures: mudcracks
Dessication on mudflats (when puddle dries and contracts, it forms hexagonal structures) **subaerial exposure + shallow water
Silica-intermediate
Diorite and Andesite
freshwater
Does not contain any saltwater and can be rivers, lakes, streams, ponds, and wetlands
drumlin fields
Drumlins are not found singly but rather occur in clusters
What type of system is Earth?
Earth in space is a closed system -Little exchange of matter from without -Sun provides energy from outside the Earth -If changes are made in one part of a closed system other parts of the system will be affected -In the closed system of the Earth-the reservoirs are all connected and matter and energy is exchanged between them
Atmosphere
Earth's gaseous envelope → a life-giving gaseous envelope that surrounds the Earth = It protects us from the Sun's heat and ultraviolet rays, and provides us with the air that we breathe • the energy exchanges that continually occur btwn the atmosphere & Earth's surface and btwn the atmosphere and space the effects we call weather and climate
natural leeves
Elevated ridges along a river's bank that are formed by the deposition of the river's sediment load. Natural levees are built by successive floods over many years. When a stream overflows its banks, its velocity immediately diminishes, leaving coarse sediment deposited in strips bordering the channel. As the water spreads out over the valley, a thin layer of fine sediment is deposited over the valley floor. This uneven distribution of material produces the very gentle slope of the natural levee.
Electromagnetic radiation spectrum
Energy measured in wavelengths and frequency, arranged on a spectrum
Proterozoic
Era between 2.5 million to 544 million years ago. An oxygen-rich early atmosphere formed, sparking the Cambrian explosion of biodiversity.
Stream channel in floodplain
Erosion carves the sides of stream channels, contributing sediments to streams and allowing the channel to migrate over time. Sediments are moved by streams in different ways. Fine grained particles and dissolved components are carried in suspension (called the suspended load)
The Racetrack in Death Valley-sliding stones
Erosional forces cause rocks from the surrounding mountains to tumble to the surface of the Racetrack. Once on the floor of the playa the rocks move across the level surface leaving trails as records of their movements. Some of the moving rocks are large and have traveled as far as 1,500 feet.
Volcanic Eruptions
Eruptive styles: 1) Non-explosive •Low silica •Low gas content •Basaltic lava flows 2)Explosive •High silica •High gas content •Pyroclastic andesitic
mechanical weathering and deserts
Even mechanical weathering is slowed, because of a lack of runoff and even a lack of moisture to perform ice wedging.
Dynamic Interactions between Systems
Example is a negative feedback system with a thermostat and furnace
Some atoms bond to form ionic compounds, some form molecules, and still others form metallic substances. Why does this happen?
Experiments show that electrical forces hold atoms together and bond them to each other. These electrical attractions lower the total energy of the bonded atoms, and this, in turn, generally makes them more stable. Consequently, atoms that are bonded in compounds tend to be more stable than atoms that are free (not bonded).
alluvial fans
Fan-shaped deposits of sediments dropped by streams flowing out of mountains. Alluvial fans form in response to the abrupt drop in gradient combined with the change from a narrow channel of a mountain stream to less confined channels at the base of the mountains. The sudden drop in velocity causes the stream to dump its load of sediment quickly in a distinctive cone- or fan-shaped accumulation
Listric Normal Faults
Faults concave upward, with dip decreasing with depth.
Common Light Silicate Minerals: Felspar minerals
Feldspar minerals are by far the most plentiful silicate group in Earth's crust, comprising about 51 percent of the crust (Figure 2.25). Their abundance can be partially explained by the fact that they can form under a wide range of temperatures and pressures.
Parent material influences soils in two ways
First, the type of parent material influences the rate of weathering and thus the rate of soil formation. (Consider the weathering rates of granite and limestone.) Also, because sediments are already partly weathered and provide more surface area for chemical weathering, soil development on such material usually progresses more rapidly. Second, the chemical makeup of the parent material affects the soil's fertility. This influences the character of the natural vegetation the soil can support.
lobe-finned fishes
Fish species characterized by two pairs of sturdy lobe-shaped fins on the underside of the body.
towfish
Fixed transducer that emits frequency burst of acoustic energy
Flat-lying strata and desert terrain
Flat-lying Strata. Sediments are laid down layer upon layer with the oldest on the bottom and the youngest on top. Desert terrain exists in warm, temperate, and cold climates, but all deserts share one common trait: little rain.
Chemically Active Fluids as Metamorphic Agents
Fluids that surround mineral grains act as catalysts that promote recrystallization by enhancing ion migration. In progressively hotter environments, these ion-rich fluids become correspondingly more reactive. Chemically active fluids can produce two types of metamorphism. Minerals tend to recrystallize and grow longer in a direction perpendicular to compressional stresses.
Principle of Fossil Succession (example)
For example, an Age of Trilobites is recognized quite early in the fossil record. Then, in succession, paleontologists recognize an Age of Fishes, an Age of Coal Swamps, an Age of Reptiles, and an Age of Mammals. These "ages" pertain to groups that were especially plentiful and characteristic during particular time periods. Within each of the "ages" are many subdivisions, based, for example, on certain species of trilobites and certain types of fish, reptiles, and so on. This same succession of dominant organisms, never out of order, is found on every continent.
Evidence: Rock Types and Geologic Features (continental drift)
For instance, highly deformed igneous rocks in Brazil closely resemble similar rocks of the same age in Africa. Also, the mountain belt that includes the Appalachians trends northeastward through the eastern United States and disappears off the coast of Newfoundland. Mountains of comparable age and structure are found in the British Isles and Scandinavia. When these landmasses are positioned as Wegener proposed, the mountain chains form a nearly continuous bel
Strain rate and temperature
For most materials, an increase of strain rate raises flow stress. The effect of strain rate to the flow stress is mostly negligible near room temperature (e.g., ca. only 1 or 2% increase), but becomes pronounced at elevated temperatures (e.g., becomes 10-50% increase in flow stress).
reptile
Fossil evidence indicates that about 310 million years ago, the first reptiles evolved from an ancestor common to both reptiles and amphibians. The earliest known reptiles resembled lizards with small sharp teeth. The reptile group includes snakes, turtles, lizards, and crocodiles, as well as extinct groups such as dinosaurs, ichthyosaurs, and plesiosaurs. (Birds, which are descendants of one group of dinosaurs, can also be considered reptiles, depending on the classification system used.)
Types of Fossils
Fossils are preserved in many ways. The remains of relatively recent organisms may not have been altered at all. Objects such as teeth, bones, and shells are common examples. Far less common are entire animals, flesh included, that have been preserved because of rather unusual circumstances. Remains of prehistoric elephant relatives called mammoths that were frozen in the Arctic tundra of Siberia and Alaska are examples, as are the mummified remains of sloths preserved in a dry cave in Nevada.
Ediacaran Fauna
Fossils of multicellular, varied organisms lacking a mouth, anus, and gut that were widely distributed in the shallow oceans of the late Proterozoic and flourished between 570 and 670 million years ago.
HMS Challenger
From December 1872 to May 1876, the Challenger expedition made the first comprehensive study of the global ocean. During the 127,500-kilometer (79,200-mile) voyage, the ship and its crew of scientists traveled to every ocean except the Arctic. Throughout the voyage, they sampled a multitude of ocean properties, including water depth, which was accomplished by laboriously lowering a long, weighted line overboard and then retrieving it. Using this process, the Challenger made the first recording of the deepest-known point on the ocean floor in 1875. This spot, on the floor of the western Pacific, was later named the Challenger Deep.
Silica-poor
Gabbro and Basalt
Overpumping causes saltwater intrusion
Generally, saltwater intrusion into coastal aquifers is caused by two mechanisms: Lateral encroachment from the ocean due to excessive water withdrawals from coastal aquifers, or. Upward movement from deeper saline zones due to upconing near coastal discharge/pumping wells
Geologic Importance of Groundwater
Geologically, groundwater is important as an erosional agent. The dissolving action of groundwater slowly removes soluble rock such as limestone, causing surface depressions known as sinkholes to form and creating subterranean caverns. Groundwater is thus a form of storage that sustains streams during periods when rain does not fall. When we see water flowing in a river during a dry period, it is water from rain that fell at some earlier time and was stored underground.
Dating with Fossils
Geologists get a wide range of information from fossils. They help us to understand evolution and life in general; they provide critical information for understanding depositional environments and changes in Earth's climate; and, of course, they can be used to date rocks.
Advancing Glacier
Glacier with a positive budget, so that accumulation results in the lower edges being pushed outward and downward.
Cyanobacteria (blue-green algae)
Gram-negative cell walls Extensive thylakoids with photosynthetic chlorophyll pigments and gas inclusions
Silica-rich
Granite and Rhyolite
Glaciers form exclusively on land, and in the Northern Hemisphere, Greenland supports an ice sheet
Greenland extends between about 60° and 80° north latitude. This largest island on Earth is covered by an imposing ice sheet that occupies 1.7 million square kilometers (663,000 square miles), or about 80 percent of the island. Averaging nearly 1500 meters (5000 feet) thick, the ice extends 3000 meters (10,000 feet) above the island's bedrock floor in some places.
Two groups of seed plants exist, gymnosperms and angiosperms
Gymnosperms produce "naked seeds" that develop on modified leaves, usually scale-like structures that form a con
valley walls
High ground on both sides that are its boundaries.
Dark silicate minerals: Amphibole Group
Hornblende = usually dark green to black in color, and except for its cleavage angles, which are about 60 degrees and 120 degrees, it is very similar in appearance to augite. In a rock, hornblende often forms elongated crystals
Mineral Strength
How easily minerals break or deform under stress is determined by the type and strength of the chemical bonds that hold the crystals together
Snowball Earth
Hypothesis that proposes that the Earth was entirely covered by ice in part of the Cryogenian period of the Proterozoic eon, and perhaps at other times in the history of Earth
Other Effects of Ice Age Glaciers: Ice Dams Create Proglacial Lakes
Ice sheets and alpine glaciers can act as dams and create lakes by trapping glacial meltwater and blocking the flow of rivers. Some of these lakes are relatively small, short-lived impoundments. Others can be large and exist for hundreds or thousands of years. With the retreat of the ice sheet came enormous volumes of meltwater. The Great Plains generally slope upward to the west. As the terminus of the ice sheet receded northeastward, meltwater was trapped between the ice on one side and the sloping land on the other, causing Lake Agassiz to deepen and spread across the landscape.
soil formation: time
If weathering has been going on for a comparatively short time, the parent material strongly influences the characteristics of the soil. As weathering processes continue, the influence of parent material on soil is overshadowed by the other soil-forming factors, especially the climate. As a rule, the longer a soil has been forming, the thicker it becomes and the less it resembles the parent material
Applying Relative Dating Principles
If you apply the principles of relative dating to the hypothetical geologic cross section, you can place in proper sequence the rocks and the events they represent.
intrusive rocks(plutonic rocks)
Igneous rocks that form as magma cools underground
Siccar Point, Scotland
In 1788, James Hutton first discovered Siccar Point, and understood its significance. It is by far the most spectacular of several unconformities that he discovered in Scotland, and very important in helping Hutton to explain his ideas about the processes of the Earth.. Non-horizontal layers- something has happened there- present is key to the past. Proved point of uniformitarianism > location where scientists first recognized the rock cycle
Environmental Indicators for fossils
In addition to being important, and often essential, tools for correlation, fossils are important environmental indicators. Although we can deduce much about past environments by studying the nature and characteristics of sedimentary rocks, a close examination of the fossils present can usually provide a great deal more information. For example, when the remains of certain clam shells are found in limestone, a geologist quite reasonably assumes that the region was once covered by a shallow sea. Fossils can also at times be used to identify the approximate position of an ancient shoreline. Given what we know of living organisms, we can conclude that fossil animals with thick shells, capable of withstanding pounding and surging waves, inhabited shorelines. On the other hand, animals with thin, delicate shells probably indicate deep, calm offshore waters. Fossils also can be used to indicate the former temperature of the water. Certain kinds of present-day corals must live in warm and shallow tropical seas like those around Florida and The Bahamas. When similar types of coral are found in ancient limestones, they indicate the marine environment that must have existed when they were alive. These examples illustrate how fossils can help unravel the complex story of Earth history.
Trace Fossils
In addition to the fossils already mentioned, there are numerous other types, many of them only traces of prehistoric life. Examples of such indirect evidence include: > Tracks—animal footprints made in soft sediment that later turned into sedimentary rock. > Burrows—tubes in sediment, wood, or rock made by an animal. These holes may later become filled with mineral matter and preserved. Some of the oldest-known fossils are believed to be worm burrows. > Coprolites—fossil dung can provide useful information pertaining to the size and food habits of organisms > Gastroliths—highly polished stomach stones that were used in the grinding of food by some dinosaurs and other organisms.
Other Effects of Ice Age Glaciers: Crustal Subsidence and Rebound
In areas that were major centers of ice accumulation, such as Scandinavia and northern Canada, the land has been slowly rising for the past several thousand years. The land had downwarped under the tremendous weight of 3-kilometer- (almost 2-mile-) thick ice sheets.
Overpumping causes subsidence
In cases where the aquitards are soft and unconsolidated, for example, composed of clays and silts, overpumping can cause these layers to fail structurally, expel much of their water, and literally collapse. When this happens, the overlying ground level can be lowered as a consequence, a process known as subsidence(ex: San Joaquin Valley, tower of pisa, and venice)
Treating Groundwater as a Nonrenewable Resource
In many places the water available to recharge the aquifer falls significantly short of the amount being withdrawn
In the Southern Hemisphere, the huge Antarctic Ice Sheet....
In the Southern Hemisphere, the huge Antarctic Ice Sheet attains a maximum thickness of about 4300 meters (14,000 feet) and covers an area of more than 13.9 million square kilometers (5.4 million square miles)—nearly the entire continent
interior drainage example
In the United States, the dry Basin and Range region provides an excellent example. The region includes southern Oregon, all of Nevada, western Utah, southeastern California, southern Arizona, and southern New Mexico. The name Basin and Range is an apt description for this almost 800,000-square-kilometer (312,000-square-mile) region, which is characterized by more than 200 relatively small mountain ranges that rise 900 to 1500 meters (3000-5000 feet) above the basins that separate them.
Mineral Strength: Cleavage
In the crystal structure of many minerals, some atomic bonds are weaker than others. It is along these weak bonds that minerals tend to break when they are stressed → cleavage = the tendency of a mineral to break (cleave) along planes of weak bonding
Arroyo after flash flood
In the desert, storms can come on quickly, and because desert sands don't readily soak up water, heavy rains can rapidly lead to flash floods. While rainfall over farmland can seep into the ground, sidewalks and pavement are impervious to moisture, causing heavy rains to run off to low spots very quickly.J
The weathering of the potassium feldspar component of granite
In this reaction, the hydrogen ions (H+) attack and replace potassium ions (K+) in the feldspar structure, thereby disrupting the crystalline network. Once removed, the potassium is available as a nutrient for plants or becomes the soluble salt potassium bicarbonate (KHCO3), which may be incorporated into other minerals or carried to the ocean in dissolved form by groundwater and streams
Indian Plate
Indian plate as parted from the Australian plate and moved north towards Eurasian plate 130 million years ago. The Indian plate moved northwards as continents drifts so it collided with Eurasian plate which was already present in the north.
flood recurrence
Intervals and probabilities of flood occurrences
Isostasy: Erosion and uplift
Isostasy is the key mechanism that links a mountains tectonic, or internal, evolution to its geomorphic, or external, development. When erosion at the surface removes mass, isostasy responds by lifting the entire mountain range up to replace about 80 percent of the mass removed.
Glacier moves fastest near center, near surface
It can move by basal sliding Or it can move by plastic deformation of the ice. Ice near surface doesn't deform plastically, but is brittle
Angular Unconformity
It consists of tilted or folded sedimentary rocks that are overlain by younger, more flat-lying strata. An angular unconformity indicates that during a pause in deposition, a period of deformation (folding or tilting) and erosion occurred
Crystallization
The process by which atoms are arranged to form a material with a crystal structure
West Wind Drift
It flows around the ice-covered continent of Antarctica, where no large landmasses are in the way, so its cold surface waters circulate in a continuous loop. It moves in response to the Southern Hemisphere prevailing westerly winds, and portions of it split off into the adjoining southern ocean basins. Its strong flow also helps define the Southern Ocean or Antarctic Ocean, which is really the portions of the Pacific, Atlantic, and Indian Oceans south of about 50° south latitude.
Paleontology
It is an interdisciplinary science that blends geology and biology in an attempt to understand all aspects of the evolution of life over the vast expanse of geologic time. Knowing the nature of the life-forms that existed at a particular time helps researchers understand past environmental conditions. Further, fossils are important time indicators and play a key role in correlating rocks of similar ages that are from different places.
Jointing aids physical weathering
Joints are regularly spaced fractures or cracks in rocks that show no offset across the fracture (fractures that show an offset are called faults). Joints form as a result of expansion due to cooling or relief of pressure as overlying rocks are removed by erosion. Igneous plutons crack in onion like "exfoliation" layers. These layers break off as sheets that slide off of a pluton. Over time, this process creates domed remnants. Joints form free space in rock by which other agents of chemical or physical weathering can enter.
pluvial lakes
Lake formed in a cooler, wetter climate in arid and semi-arid areas. Example - Utah's Great Salt Lake.
Sheeting
Large bodies of rocks exposed through erosion and pieces peeled off
Proximity to ocean modifies temperature range
Large bodies of water, such as oceans, seas and large lakes, can affect the climate of an area. Water heats and cools more slowly than landmasses. Therefore, the coastal regions will stay cooler in summer and warmer in winter, thus creating a more moderate climate with a narrower temperature range.
Shield Volcano-Mauna Loa
Largest volcano on earth
Earth's Primitive Atmosphere
Late in Earth's formative period, its atmosphere probably consisted of gases most common in the early solar system: hydrogen, helium, methane, ammonia, carbon dioxide, and water vapor. The lightest of these—hydrogen and helium—likely escaped into space because Earth's gravity was too weak to hold them. The gases that remained—methane, ammonia, carbon dioxide, and water vapor—contain the basic ingredients of life: carbon, hydrogen, oxygen, and nitrogen.
Medial and Lateral Moraines
Lateral and medial moraines consist of glacially-transported rock and debris. They form on the sides of glaciers (lateral moraines) or at the boundary between two tributary glaciers (medial moraines). Either way, they often mark the edges of an ice body
pillow lava
Lava that cools underwater, taking on a distinctive pillow-like shape as it hardens
plateau basalts
Layers of basalt flows that have built up to great thicknesses.
Soil horizons
Layers of soil
Evidence: The Continental Jigsaw Puzzle (continental drift)
Like a few others before him, Wegener suspected that the continents might once have been joined when he noticed the remarkable similarity between the coastlines on opposite sides of the Atlantic Ocean
Seafloor Magnetic anomalies
Linear belts of alternating high and low magnetic field strength **magnetic fields stronger or weaker than expected
valley floor
Lower, flatter area that is partially or totally occupied by the stream channel
downcut
Lowering a stream's base level will cause the stream to __________________
Emplacement of Intrusive Igneous Rocks
Magmas move in the crust owing to the influence of gravity, tectonic forces, or pressures from within the magmas themselves. Their movement necessitates displacements of the surrounding crustal rocks and accordingly their mode of emplacement is often controlled by structures within these rocks.
Circum-Pacific Belt
Major belt around the edge of the Pacific Ocean on which most composite volcanoes are located and where many earthquakes occur (encompasses the coastal regions of Chile, Central America, Indonesia, Japan, and Alaska, including the Aleutian Island)
eras
Major divisions of geologic time that are divided into periods and further subdivided into epochs
What are 3 ways to prevent soil erosion by protecting the soil?
Manage crops, reduce erosion on slopes, reduce erosion at construction sites.
examples of deltas
Many large rivers have deltas extending over thousands of square kilometers. The delta of the Mississippi River is one example. It resulted from the accumulation of huge quantities of sediment derived from the vast region drained by the river and its tributaries (see Figure 9.3). Today, New Orleans rests where there was ocean less than 5000 years ago. Figure 9.24 shows that portion of the Mississippi delta that has been built over the past 6000 years. As you can see, the delta is actually a series of seven coalescing subdeltas. Each formed when the river left its existing channel in favor of a shorter, more direct path to the Gulf of Mexico. The individual subdeltas interfinger and partially cover one another, producing a very complex structure. The present subdelta, called a bird-foot delta because of the configuration of its distributaries, has been built by the Mississippi in the past 500 years.
Other Effects of Ice Age Glaciers: Changing Rivers
Many present-day stream courses bear little resemblance to their preglacial routes. The Missouri River once flowed northward toward Hudson Bay in Canada. The Mississippi River followed a path through central Illinois, and the head of the Ohio River reached only as far as Indiana
By about 160 million years ago, a group of feathered dinosaurs gave rise to modern birds
Many researches consider Archaeopteryx to be the first known bird. Archaeopteryx had feathered wings but retained teeth, clawed digits in its wings, and a long tail with many vertebrae. A recent study concluded that Archaeopteryx flew well at high speeds, but unlike most modern birds, it could not take off from a standing position. Rather, these descendants of bird-like dinosaurs took flight by running and leaping into the air.
how glacial movement was first investigated during the nineteenth century
Markers were placed in a straight line across an alpine glacier (in this example, Rhône Glacier in the Swiss Alps), and the original position of the line was marked on the valley walls. The positions of the markers were noted periodically, revealing the nature of the movement described above. In this particular study, investigators also mapped the position of the glacier's terminus, demonstrating that the terminus could retreat even as the ice within the glacier moved forward.
Controls and Triggers of Mass Movement: The Role of Water
Mass movement is sometimes triggered when heavy rains or melting snow saturate surface materials. The water does not transport the material. Rather, it allows gravity to more easily set the material in motion.
Classifying Mass Movements: type of Material
Mass movement processes can be classified based on the material involved. If soil and regolith dominate, terms such as debris, mud, or earth are used in the description. In contrast, when a mass of bedrock breaks loose and moves downslope, the term rock may be part of the description.
uluru
Massive rock in the Great Sandy Desert also known as Ayer's Rock. [Australia]
Growth of a Meander
Meandering rivers erode sediment from the outer curve of each meander bend and deposit it on an inner curve further down stream. This causes individual meanders to grow larger and larger over time.
Altocumulus
Medium level cumulus cloud that is higher than regular cumulus clouds. Lead to precipitation.
Evidence of fluids: Metasomatism
Metamorphism coupled with the introduction of ions from an external source
Mineral Properties
Mineral properties can be used to identify minerals -Physical properties • Hardness • Cleavage • Fracture • Streak (color) • Luster • Density
Classification of Sedimentary Rocks: Mineralogy
Mineralogy is also important: • Presence of quartz, clay, feldspars etc indicates the degree of chemical weathering and distance transported from the source (provenance) area • Feldspars and mafics (pyroxenes and amphiboles) are easily weathered chemically • Clay is the product of that weathering • Graywacke is an "immature" sandstone with quartz, feldspars, and clay
Characteristics of Minerals: Orderly Crystalline Structure
Minerals are crystalline substances, made up of atoms (or ions) that are arranged in an orderly, repetitive manner
Characteristics of Minerals: Naturally Occurring
Minerals form by natural geologic processes
how minerals grow
Minerals grow by adding atoms one by one (from the edge) & in the space available
optical properties of minerals: Luster - metallic luster
Minerals that are shiny like a metal, regardless of color
Theory of the Earth
Modern geology began in the late 1700s, when James Hutton, a Scottish physician and gentleman farmer, published his Theory of the Earthublished his important work Theory of the Earth. Prior to Hutton's Theory of the Earth, no one had effectively demonstrated that geologic processes occur over extremely long periods of time. However, Hutton persuasively argued that processes that appear to be weak and slow acting can, over long spans of time, produce effects that are just as great as those resulting from sudden catastrophic events. Unlike his predecessors, Hutton cited verifiable observations to support his ideas.
Characteristics of Minerals: Definite Chemical Composition That Allows For Some Variation.
Most minerals are chemical compounds having compositions that can be expressed by a chemical formula
optical properties of minerals: Luster - nonmetallic luster
Most minerals have a nonmetallic luster and are described using various adjectives. For example, some minerals are described as being vitreous, or glassy.
Formation of ventifacts
Mostly, ventifacts are formed from hard rocks with fine grains such as quartz, chert and obsidian. As the wind blows towards a rock while carrying its load of sand grains, the rock outcropping acts as a windbreaker. This side becomes abraded over time by the sand particles, which leads to the formation of a ventifact.
thermohaline (thermo = heat, haline = salt) circulation
Movement of ocean water caused by density difference brought about by variations in temperature and salinity. As ocean water freezes at the poles it concentrates salt, and the colder, denser water sinks.
Precambrian
Name for the time in earths early history that accounts for ninety percent of earth's time, but only cellular organi•Precambrian plate tectonics -Governed by hot thin crust (high heat flow) •Precambrian shields -Continental growth by accretion •Life Forms -Single-celled prokaryotes -Stromatolites •Banded Iron Formations (BIFs) •Ore deposits, but no oil (petroleum) •Rodinia Snowball Earthsms lived.
Greenhouse effect
Natural situation in which heat is retained in Earth's atmosphere by carbon dioxide, methane, water vapor, and other gases
Cambrian North America
North American Paleogeography: Fossil evidence tells us that Laurentia was centered on the Equator and rotated so that in present-day terms, Canada was east, instead of north, of the United States. As with most of the continents, the majority of North America was underwater throughout the Cambrian Period.
Solum
O A B ("true soil")
Offset on Fault
Oblique faults cause an offset in the sequence, which is associated with either a gap or an overlap depending upon the downthrow direction.
optical properties of minerals
Of the many diagnostic properties of minerals, their optical characteristics such as luster, color, streak, and ability to transmit light are most frequently used for mineral identification
Isolated Tetrahedra
Olivine
Dark silicate minerals: Olivine Group
Olivine = a family of high-temperature silicate minerals, are black to olive green in color and have a glassy luster and a conchoidal fracture
Valley Widening
Once a stream has cut its channel closer to base level, downward erosion becomes less dominant. At this point, the stream's channel takes on a meandering pattern, and more of the stream's energy is directed from side to side. The result is a widening of the valley as the river cuts away first at one bank and then the other
What happens in the (basic) rock cycle?
Once formed, a magma body rises toward the surface because it is less dense than the surrounding rock → Eventually, molten rock cools and solidifies (crystallization or solidification) → the resulting rocks are called igneous rocks → If igneous rocks are exposed at the surface, they undergo weathering → the loose materials that result are often moved downslope by gravity and then picked up and transported by one or more erosional agents—running water, glaciers, wind, or waves → These rock particles and dissolved substances(sediment) are eventually deposited → the sediments undergo lithification → Sediment is usually lithified into sedimentary rock when compacted by the weight of overlying materials or when cemented by percolating groundwater that fills the pores with mineral matter→ If the resulting sedimentary rock becomes deeply buried or is involved in the dynamics of mountain building, it will be subjected to great pressures and intense heat. The sedimentary rock may react to the changing environment by turning into the third rock type, metamorphic rock → If metamorphic rock is subjected to still higher temperatures, it may melt, creating magma, and the cycle begins again.
ionic bond
One atom gives up one or more valence electrons to another atom to form ions
hot spring
One frequently used definition is that the water in a hot spring is 6° to 9°C (10° to 15°F) warmer than the average annual air temperature for the locality where it occurs.
Some reptiles evolved with specialized characteristics that allowed them to inhabit drastically different habitats
One group, the pterosaurs, became airborne. How the largest pterosaurs—some of which had wing spans greater than 11 meters (35 feet) and weighed more than 90 kilograms (200 pounds)—took flight is still unknown. Other reptiles returned to the sea, including fish-eating plesiosaurs and ichthyosaurs
Several factors contribute to the irregular surface of the water table.
One important influence is the fact that groundwater moves very slowly. Because of this, water tends to "pile up" beneath high areas between stream valleys. If rainfall were to cease completely, these water "hills" would slowly subside and gradually approach the level of the adjacent valleys. However, new supplies of rainwater are usually added often enough to prevent this. Nevertheless, in times of extended drought, the water table may drop enough to dry up shallow wells. Other causes of the uneven water table are variations in rainfall and in the permeability of Earth materials from place to place.
Other Effects of Ice Age Glaciers: Sea-Level Changes
One of the most interesting and perhaps dramatic effects of the Ice Age was the fall and rise of sea level that accompanied the advance and retreat of the glaciers. Although the total volume of glacial ice today is great, exceeding 25 million cubic kilometers, during the Last Glacial Maximum the volume of glacial ice amounted to about 70 million cubic kilometers, or 45 million cubic kilometers more than at present.
two types of surface waves
One type causes Earth's surface and anything resting on it to move up and down, much as ocean swells toss a ship. The second type of surface wave causes Earth's surface to move from side to side. This motion is particularly damaging to the foundations of structures 1) Love Wave -Horizontal shear wave at surface 2) Rayleigh Wave -Vertical P-S wave at surface
lithification of sediment: cementation
One way in which sedimentary rocks are lithified. As material precipitates from water that percolates through the sediment, open spaces are filled and particles are joined into a solid mass.
Stratovolcano-Mt. St. Helens 1980
Only 57 killed. It had an *unexpected landslide* and a *lateral blast* of ash plume. The landslide slid in 3 parts 2nd failure exposed magma chamber. Huge ash plume over much of USA. Pyroclastic flow and mud flows affected climate. Lessons learned: Now the volcano has extensive monitoring. After the fact hazards map created. By 2004 the new dome being created looks like Peles.
Characteristics of Minerals: Solid Substance
Only solid crystalline substances are considered minerals
Ambiguous Properties
Other properties of more than one mineral (example: color)
Controls and Triggers of Mass Movement: Oversteepened Slopes
Oversteepening of slopes is another common trigger of mass movements. As a slope becomes steeper, the forces that resist the downward pull of gravity get weaker.
oversteepened slopes
Oversteepening of slopes is another common trigger of mass movements. As a slope becomes steeper, the forces that resist the downward pull of gravity get weaker. Many situations result in oversteepening
Supai Group
Oxidized sediment from the overlying Pennsylvanian Supai Group turns the Redwall Limestone 'red'
Evidence: Ancient Climates (continental drift)
Paleoclimatic evidence for continental drift: Wegener suggested a more plausible explanation for the late Paleozoic glaciation: The southern continents were joined together in the supercontinent of Pangaea and located near the South Pole. This would account for the polar conditions required to generate extensive expanses of glacial ice over much of these landmasses. At the same time, this geography places today's northern continents nearer the equator and accounts for the tropical swamps that generated the vast coal deposits.
The formation of Pangaea
Pangaea formed through a gradual process spanning a few hundred million years. Beginning about 480 million years ago, a continent called Laurentia, which includes parts of North America, merged with several other micro-continents to form Euramerica.
Evidence: Fossils Matching Across the Seas (continental drift)
Pangea distribution of fossils: Fossils of identical organisms have been discovered in rocks of similar age in Australia, Africa, South America, Antarctica, and India—continents that are currently widely separated by ocean barriers. Wegener accounted for these occurrences by placing these continents in their pre-drift locations.
estuaries
Partially enclosed coastal area at the mouth of a river where its freshwater, carrying fertile silt and runoff from the land, mixes with salty seawater.
Younger Dryas
Period of global cooling that occurred 12,000 years ago
Physical weathering helps chemical weathering by reducing fragment size
Physical and chemical weathering degrade rocks in different ways. While physical weathering breaks down a rock's physical structure, chemical weathering alters a rock's chemical composition.
eutherians
Placental mammal; mammal whose young complete their embryonic development within the uterus, joined to the mother by the placenta.
Controls and Triggers of Mass Movement: Removal of Vegetation
Plants protect against erosion and contribute to the stability of slopes because their root systems bind soil and regolith together. In addition, plants shield the soil surface from the erosional effects of raindrop impact (see Figure 8.18). Where plants are lacking, mass movement is enhanced, especially if slopes are steep and water is plentiful.
Example of a Theory
Plate tectonics → evolution of the continents and the ocean basins thru time
Industrial waste pollutes groundwater
Plume of pollutants flows with groundwater
Common Light Silicate Minerals: Two different feldspar structures exist
Potassium & plagioclase
Hadean
Pre Cambrian. Before Archezoic. Rockless, formation of Earth, solidifying crust. The name Hadean is derived from the Greek word Hades, meaning "the underworld," referring to the "hellish" conditions on Earth at the time.
Chemical Sedimentary Rocks: Carbonates
Primarily composed of calcite and/or dolomite 1) Limestone - calcite clay (micrite) and shellsa) coquina, oolitic limestone, fossiliferous limestone, micrite, biomicrite, etc. 2) Dolostone - composed of dolomite Ca, Mg (Co3)2a) Formed by alteration of limestone 3)Travertine - cave deposits 4) Tufa - Formed in and near springs and streams
Carbon 14 Dating
Process of estimating age of once living material by measuring the amount of radioactive isotope of carbon present in material.
Diagnostic Properties
Properties that help in identifying an unknown mineral
Dark silicate minerals: Pyroxene Group
Pyroxenes = a group of diverse minerals that are important components of dark-colored igneous rocks Augite = a black, opaque mineral with two directions of cleavage that meet at nearly a 90-degree angle
Major groups of silicate minerals
Quartz & feldspars etc
weathering of quartz
Quartz, the other main component of granite, is very resistant to chemical weathering; it remains substantially unaltered by weakly acidic solutions. As a result, when granite weathers, the feldspar crystals dull and slowly turn to clay, releasing the once-interlocked quartz grains, which still retain their fresh, glassy appearance. Although some quartz remains in the soil, much is transported to the sea or to other sites of deposition, where it becomes the main constituent of such features as sandy beaches and sand dunes. In time it may become lithified to form the sedimentary rock sandstone.
Earth's Oldest Rocks
Radiometric dating has produced literally thousands of dates for events in Earth history. Rocks exceeding 3.5 billion years in age are found on all of the continents. Earth's oldest rocks (so far) may be as old as 4.28 billion years (b.y.). Discovered in northern Quebec, Canada, on the shores of Hudson Bay, these rocks may be remnants of Earth's earliest crust. Rocks from western Greenland have been dated at 3.7 to 3.8 b.y., and rocks nearly as old are found in the Minnesota River valley and northern Michigan (3.5 to 3.7 b.y.), in southern Africa (3.4 to 3.5 b.y.), and in western Australia (3.4 to 3.6 b.y.). Tiny crystals of the mineral zircon having radiometric ages as old as 4.3 b.y. have been found in younger sedimentary rocks in western Australia. The source rocks for these tiny durable grains either no longer exist or have not yet been found.
What differentiates continental crust from oceanic crust?
Recall that oceanic crust is a relatively dense (3.0 g/cm3) homogeneous layer of basaltic rocks derived from partial melting of the rocky upper mantle. In addition, oceanic crust is thin, averaging only 7 kilometers (4 miles) thick. Continental crust, on the other hand, is composed of a variety of rock types, has an average thickness of nearly 40 kilometers (25 miles), and contains a large percentage of low-density (2.7 g/cm3) silica-rich rocks such as granite.
Recharge areas and Discharge areas
Recharge involves the downward movement and influx of groundwater to an aquifer; discharge involves the upward movement and outflux of groundwater from an aquifer. Recharge and discharge activities are usually spatially limited to a small portion of an aquifer.
Zone of wastage (ablation)
Region in lower part of glacier where more snow/ice melts than accumulates resulting in loss of glacial ice.
Fold and thrust belt
Regions where the upper crust is shortened and in return is packed with a system of faults and folds
Rock characteristics
Rock characteristics encompass all the chemical traits of rocks, including mineral composition and solubility. In addition, physical features such as joints (cracks) can be important because they influence the ability of water to penetrate rock (see Figure 8.8). The variations in weathering rates due to mineral constituents can be demonstrated by examining the inscriptions on old headstones made from different rock types (Figure 8.10). Headstones of granite, which are composed of silicate minerals, are relatively resistant to chemical weathering. On the other hand, the marble headstone shows signs of extensive chemical alteration over a relatively short period. Marble is composed of calcite (calcium carbonate), which readily dissolves even in a weakly acidic solution.
Gros Ventre rockslide
Sometimes an earthquake triggers a rockslide. On other occasions, a rockslide is triggered when rain or melting snow lubricates the underlying surface to the point that friction is no longer sufficient to hold the rock unit in place. As a result, rockslides tend to be most common during spring, when heavy rains and melting snow are most prevalent.
Mesozoic History
Spanning about 186 million years, the Mesozoic era is divided into three periods: the Triassic, Jurassic, and Cretaceous. Major geologic events of the Mesozoic include the breakup of Pangaea and the evolution of our modern ocean basins.
Weathering causes rounded blocks
Spheroidal weathering
Mountain Building- Steps
Step one: Passive continental margin Step two: Ocean-continental convergence (Andean margin) Step three: Continental arc develops Step four: Ocean basin closes Step five: Culmination: continent-continent collision
Steep bedrock channels often develop a sequence of steps and pools.
Steps are steep segments where bedrock is exposed. These steep areas contain rapids or, occasionally, waterfalls. Pools are relatively flat segments where alluvium tends to accumulate.
Examples of exfoliation domes
Stone Mountain in Georgia and Half Dome in Yosemite National Park
intermittent streams
Streams that exhibit flow only during wet periods
Meandering Streams
Streams that have channels with many curves. These streams flow in relatively deep, smooth channels and transport mainly mud (silt and clay), sand, and occasionally fine gravel. The lower Mississippi River exhibits a channel of this type.
Stress and Strain
Stress can cause strain, if it is sufficient to overcome the strength of the object that is under stress. Strain is a change in shape or size resulting from applied forces (deformation). Rocks only strain when placed under stress
cross beds
Structure in which relatively thin layers are inclined at an angle to the main bedding. Formed by currents of wind or water.
Cross section of oceanic lithosphere
Structure: pillow lavas, vertical dikes, Gabbroic Magma Chambers
Global Distribution of Deserts
Subtropical: Sahara Continental: Takla Makan Coastal: Atacama Arctic: northern Canada Rainshadow: Lee of Sierras
2 energy sources that power the Earth
Sun and Earth's Interior
Surface Expression of Groundwater-Springs and seeps
Surface Expression of Groundwater-Springs and seeps
Ocean Currents Influence Climate
Surface-ocean currents have an important effect on climate. When Earth is considered as a whole, the energy gained from incoming solar radiation is equal to the energy radiated back out to space. However, that is not true for most individual latitudes. Low latitudes gain more solar energy than they radiate to space; the reverse is true for high latitudes. Because the tropics are not heating up, nor the polar regions getting colder, there must be a large-scale transfer of heat from areas of excess to areas of deficit. This is indeed the case. The transfer of heat by winds and ocean currents equalizes these latitudinal energy imbalances. Ocean water movements account for about one-quarter of this total heat transport, and winds account for the remaining three-quarters.
Talus-fragmented rocks
Talus deposits consist of angular, irregular rock fragments with a wide range of sizes. The nature of the debris depends to a large extent on the lithology(ies) exposed in the cliff as joint and bedding characteristics are primary determinants of the shape and size of rockfalls and therefore talus particles.
Internal Temperature and Glaciers
Temperature has a big impact on glaciers, with warmer annual temperatures equaling smaller glaciers.
Antarctica-Continental Ice Sheet
The Antarctic ice sheet is the largest single mass of ice on Earth. It covers an area of almost 14 million square km and contains 30 million cubic km of ice. Around 90 percent of the fresh water on the Earth's surface is held in the ice sheet, an amount equivalent to 70 m of water in the world's oceans.
Dendritic pattern of side canyons to the Grand Canyon
The Grand Canyon's basic appearance is what geologists call a dendritic drainage pattern. This pattern is usually produced by a medium to high altitude mountain river valley, which descends relatively rapidly, resulting in a fast flow rate and vigorous cutting downward into the terrain. **Stream terraces show episodes of downcutting
Himalayan fold and thrust belt
The Himalayas formed by collision.
Indian Ocean Currents
The Indian Ocean exists mostly in the Southern Hemisphere, so it follows a surface circulation pattern similar to other Southern Hemisphere ocean basins. The small portion of the Indian Ocean in the Northern Hemisphere, however, is influenced by the seasonal wind shifts known as the summer and winter monsoons (mausim = season). When the winds change direction, the surface currents also reverse direction. During the summer, winds blow from the Indian Ocean toward the Asian landmass. In the winter, the winds reverse and blow out from Asia over the Indian Ocean. When the winds change direction, the surface currents also reverse direction.
Iron Catastrophe and Differentiation of the Earth
The Iron Catastrophe is considered as one of the most crucial geomorphic moments in Earth's history. Nickel and iron began to move to the center of our planet and formed the first core. This process is known as planetary differentiation. The Earth's core is still boiling, when compared to her exterior geo layers
milankovitch periodicities
The Milankovitch cycles include: The shape of Earth's orbit, known as eccentricity; The angle Earth's axis is tilted with respect to Earth's orbital plane, known as obliquity; and. The direction Earth's axis of rotation is pointed, known as precession.
beach nourishment
The process by which large quantities of sand are added to the beach system to offset losses caused by wave erosion.
the Devonian period
The Paleozoic age of fishes. The Devonian landscape included abundant coastal wetlands, which were home to a wide range of lobe-fins. Like some modern fishes, such as the African lungfish, when lobe-fins occupied oxygen-poor water, they would use their primitive lungs for breathing. Some lobe-finned fishes also no doubt used their stout bony fins to move from one pond to another. By the late Devonian, the fins of one group of lobe-finned fishes had evolved into four limbs and feet with digits
Permian (0.26 Ga) Pangea
The Permian period, which ended in the largest mass extinction the Earth has ever known, began about 299 million years ago. The emerging supercontinent of Pangaea presented severe extremes of climate and environment due to its vast size.
Foliation Caused by Differential Stress
The alignment of grains results in a layered texture. This means that differential stress related to different pressure in different directions is required to form foliated metamorphic rocks.
Coriolis force
The apparent force, resulting from the rotation of the Earth, that deflects air or water movement.
North American continental accretion
The appearance of our continent has been continuously changed by this complicated sequence of mountain building, erosion, and deposition of sediment in slowly sinking troughs, followed by more crustal movement.
optical properties of minerals: Luster
The appearance or quality of light reflected from the surface of a mineral
unsaturated zone
The area above the water table where openings in soil, sediment, and rock are not saturated but filled mainly with air.
Geography of the Oceans
The area of Earth is about 510 million square kilometers (197 million square miles). Of this total, approximately 360 million square kilometers (140 million square miles), or 71 percent, is represented by oceans and marginal seas (meaning seas around the ocean's margin, like the Mediterranean Sea and Caribbean Sea). Continents and islands comprise the remaining 29 percent, or 150 million square kilometers (58 million square miles).
soil formation: Plants and animals
The biosphere plays a vital role in soil formation. The types and abundance of organisms present have a strong influence on the physical and chemical properties of a soil. Soil fertility depends in part on the amount of organic matter present.
footwall
The block of rock that forms the lower half of a fault
Changes from Upstream to Downstream
The change in slope observed on most stream profiles is usually accompanied by an increase in discharge and channel size, as well as a reduction in sediment particle size. Along most rivers in humid regions, discharge increases toward the mouth because as we move downstream, more and more tributaries contribute water to the main channel. In order to accommodate the growing volume of water, channel size typically increases downstream as well. Recall that flow velocities are higher in large channels than in small channels. Observations also show a general decline in sediment size downstream, making the channel smoother and more efficient (with less friction).
Effects of urbanization on flooding
The changes in land use associated with urban development affect flooding in many ways. Removing vegetation and soil, grading the land surface, and constructing drainage networks increase runoff to streams from rainfall and snowmelt
proteins
The class of nutrients that contain nitrogen as well as carbon, hydrogen, and oxygen; besides being a source of energy, proteins play an important role in the growth and repair body tissues.
Evapotranspiration
The combined amount of evaporation and transpiration
Crystal Shape, or Habit
The common or characteristic shape of individual crystals or aggregates of crystals
Magnetostratigraphy
The comparison of the pattern of magnetic reversals in a sequence of strata, with a reference column showing the succession of reversals through time.
Magnetostratigraphy
The comparison of the pattern of magnetic reversals in a sequence of strata, with a reference column showing the succession of reversals through time. **sedimentary rocks (magnetism N or S?)
planetesimals
The composition of planetesimals was largely determined by their proximity to the protosun. As you might expect, temperatures were highest in the inner solar system and decreased toward the outer edge of the disk. Therefore, between the present orbits of Mercury and Mars, the planetesimals were composed mainly of materials with high melting temperatures—metals and rocky substances. The planetesimals that formed beyond the orbit of Mars, where temperatures are low, contained high percentages of ices—water, carbon dioxide, ammonia, and methane—as well as smaller amounts of rocky and metallic debris.
Catastrophism
The concept that Earth was shaped by catastrophic events of a short-term nature. Briefly stated, catastrophists believed that Earth's varied landscapes had been fashioned primarily by great catastrophes. Features such as mountains and canyons, which today we know take great periods of time to form, were explained as having been produced by sudden and often worldwide disasters of unknowable causes that no longer operate. This philosophy was an attempt to fit the rate of Earth's processes to the prevailing ideas about Earth's age.
Uniformitarianism
The concept that the processes that have shaped Earth in the geologic past are essentially the same as those operating today. It simply states that the physical, chemical, and biological laws that operate today have also operated in the geologic past.
Geometry and cause of Geomagnetic Field
The magnetic field of Earth is caused by currents of electricity that flow in the molten core. These currents are hundreds of miles wide and flow at thousands of miles per hour as the earth rotates. • wobbles around axis • convection outer core
Permineralization
The process by which mineral crystals replace the original living tissue of a fossil
shelf valleys
The continental shelf tends to be relatively featureless; however, some areas are mantled by extensive glacial deposits and thus are quite rugged. In addition, some continental shelves are dissected by large valleys that run from the coastline into deeper waters. Many of these shelf valleys are the seaward extensions of river valleys on the adjacent landmass. They were eroded during the most recent Ice Age (Quaternary period), when enormous quantities of water were stored in vast ice sheets on the continents, causing sea level to drop at least 100 meters (330 feet). Because of this sea-level drop, rivers extended their valleys, and land-dwelling plants and animals migrated to the newly exposed portions of the continents. Dredging off the coast of North America has retrieved the ancient remains of numerous land dwellers, such as mammoths, mastodons, and horses, providing further evidence that portions of the continental shelves were once above sea level.
Facies in delta sediments (dip greatly exaggerated)
The deltaic facies type is primarily governed by the type of delta, whether it is dominated by tide, river, or wave. But generally deltaic facies is represented by progradational lobes with alternating transgressive deposits. The progradational facies are terminated by abandonment facies or flooding surfaces.
wave base
The depth below the surface where the circular orbits become so small that movement is negligible. It is equal to one-half the wavelength
dikes and sills
The difference between a dike and a sill is that dykes are formed across or vertical to the rock while sill are on horizontal cracks
Mantle characteristics
The dominant rock type in the uppermost mantle is peridotite, which is richer in the metals iron and magnesium than are the rocks found in either the continental or oceanic crust.
Coriolis Effect
The effect of Earth's rotation on the direction of winds and currents.
How do silicate minerals form?
The environment during crystallization and the chemical composition of the molten rock mainly determine which minerals are produced →Each silicate mineral, therefore, has a structure and a chemical composition that indicate the conditions under which it formed.
Isostasy
The equilibrium between continental crust and the denser mantle below it
A fascinating assortment of shoreline features can be observed along the world's coastal regions. Although the same processes cause change along every coast, not all coasts respond in the same way. Interactions among different processes and the relative importance of each process depend on local factors.
The factors include (1) the proximity of a coast to sediment-laden rivers, (2) the degree of tectonic activity, (3) the topography and composition of the land, (4) prevailing winds and weather patterns, and (5) the configuration of the coastline and near-shore areas. Features that originate primarily because of erosion are called erosional features, whereas accumulations of sediment produce depositional features.
The way in which ice moves is complex, and there are two basic types of ice movement:
The first of these, plastic flow, involves movement within the ice. Ice behaves as a brittle solid until the pressure on it is equivalent to the weight of about 50 meters (165 feet) of ice. Once that load is surpassed, ice behaves as a plastic material, and flow begins. Such flow occurs due to the molecular structure of ice. Glacial ice consists of layers of molecules stacked one upon the other. The bonds between layers are weaker than those within each layer. Therefore, when a stress exceeds the strength of the bonds between the layers, the layers remain intact and slide over one another. A second and often equally important mechanism of glacial movement occurs when an entire ice mass slips along the ground. The lowest portions of most glaciers probably move by this sliding process.
What was the source of the basic organic molecules that became Earth's first life?
The first organic molecules may have been synthesized from carbon dioxide and nitrogen, both of which were plentiful in Earth's primitive atmosphere. Some scientists suggest that these gases could have been easily reorganized into amino acids by ultraviolet light
Making Continental Crust
The formation of continental crust is a continuation of the gravitational segregation of Earth materials that began during the final stage of our planet's formation. Dense metallic material, mainly iron and nickel, sank to form Earth's core, leaving behind the less dense rocky material that forms the mantle. It is from Earth's rocky mantle that low-density, silica-rich minerals were gradually distilled to form continental crust.
North Pacific Currents
The four main currents that comprise the North Pacific Gyre are the North Equatorial Current, the Kuroshio Current, the North Pacific Current, and the California Current. Tracking of floating objects that are released intentionally or accidentally into the ocean reveals that it takes an average of about 6 years for the objects to go all the way around the gyre.
The formation of continents
The growth of larger continental masses was accomplished through collision and accretion of many thin, highly mobile crustal fragments, as illustrated in Figure 12.10. This type of collisional tectonics deformed and metamorphosed sediments caught between converging crustal fragments, thereby shortening and thickening the developing crust. In the deepest regions of these collision zones, partial melting of the thickened crust generated silica-rich magmas that ascended and intruded the rocks above. This led to the formation of large crustal provinces that, in turn, accreted with others to form even larger crustal blocks called cratons
land hemisphere
The half of the globe containing the greatest amount of land surface, centered on western Europe - Northern Hemisphere
continental drift hypothesis
The idea that continents have moved and are still moving slowly across the Earth's surface.
Gondwana
The large southern land mass that existed from the Cambrian (540 mya) to the Jurassic (138 mya). Present-day remnants are South America, Africa, India, Australia, and Antarctica.
eons
The largest division of time on the geological scale, next in order of magnitude above era
Neap and Spring Tides
The lowest and highest tides in a lunar cycle.
base level
The lowest point to which a stream can erode
eclogite facies
The metamorphic facies at which rocks containing garnet and omphacite become stable; rocks in this facies are usually unfoliated and form under conditions of extremely high pressure and moderate temperature; usually associated with subduction zones.
granulite facies
The metamorphic facies in which gneisses become common; rocks in this facies are usually foliated and consist of minerals that form under conditions of high temperature and pressure.
The three major lineages of living mammals, the monotremes (egg-laying mammals), marsupials (mammals with a pouch), and placentals (the group to which humans belong), emerged during the Mesozoic. The groups differ principally in their modes of reproduction
The monotremes lay hard-shelled eggs, an ancestral characteristic retained in this group as well as by most modern reptiles. The platypus, which is native to Australia and Tasmania, is one of only a handful of monotreme species remaining.
nile delta
The most fertile area of land in Egypt located end of the Nile River where it empties into the Mediterranean Sea
blowouts
The most noticeable results of deflation in some places are shallow depressions. In the Great Plains region, from Texas north to Montana, thousands of blowouts can be seen. They range from small dimples less than 1 meter (3 feet) deep and 3 meters (10 feet) wide to depressions that are over 45 meters (50 feet) deep and several kilometers across.
Many factors determine the degree of destruction that accompanies an earthquake
The most obvious is the magnitude of the earthquake and its proximity to a populated area.
Supercontinents and Climate
The movement of continents changes the patterns of ocean currents and global winds, which influences the global distribution of temperature and precipitation. The formation of the Antarctic's vast ice sheet is one example of how the movement of a continent is thought to have contributed to climate change.
turbulent flow
The movement of water in an erratic fashion, often characterized by swirling, whirlpool-like eddies. Most streamflow is of this type. Strong turbulent behavior occurs in whirlpools and eddies, as well as in roiling whitewater rapids. Even streams that appear smooth on the surface often exhibit turbulent flow near the bottom and sides of the channel, where flow resistance is greatest. Turbulence contributes to a stream's ability to erode its channel because it acts to lift sediment from the streambed.
laminar flow
The movement of water particles in straight-line paths that are parallel to the channel. The water particles move downstream without mixing.
Laurasia
The northernmost of the two large continents produced by the breakup of Pangaea.
Southern Hemisphere Currents
The ocean basins in the Southern Hemisphere exhibit a similar pattern of flow as in the Northern Hemisphere basins, with surface currents that are influenced by wind belts, the positions of continents, and the Coriolis effect. In the South Atlantic and South Pacific, for example, surface-ocean circulation is very much the same as in their Northern Hemisphere counterparts except that the direction of flow is counterclockwise
fossil assemblage
The overlapping ranges of a group of fossils (assemblage) collected from a layer. By examining such an assemblage, the age of the sedimentary layer can be established.
Stratospheric Ozone Hole
The ozone hole is not technically a "hole" where no ozone is present, but is actually a region of exceptionally depleted ozone in the stratosphere over the Antarctic that happens at the beginning of Southern Hemisphere spring
zone of accumulation
The part of a glacier characterized by snow accumulation and ice formation. Its outer limit is the snowline.
Phanerozoic eon
The part of geologic time that is represented by rocks containing abundant fossil evidence. The eon extending from the end of the Proterozoic eon (540 million years ago) to the present.
tide
The periodic rise and fall of the level of water in the ocean
Permeability
The permeability of a material indicates its ability to transmit a fluid. Groundwater moves by twisting and turning through interconnected small openings. The smaller the pore spaces, the slower the groundwater moves. If the spaces between particles are too small, or if these spaces are not connected to each other, water cannot move at all. For example, clay's ability to store water can be great due to its high porosity, but its pore spaces are so small that water is unable to move through it. Thus, we say that clay is impermeable.
continental divide
The place on a continent that separates river systems flowing in opposite directions
megathrust fault
The plate boundary separating a subducting slab of oceanic lithosphere and the overlying plate.
Dating with Tephra
The premise of the technique is that each volcanic event produces ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout. Thus, once the volcanic event has been independently dated, the tephra horizon will act as time marker
difficulty of dating
The primary difficulty in assigning numerical dates to units of time is that not all rocks can be dated by using radiometric methods. For a radiometric date to be useful, all the minerals in the rock must have formed at about the same time. For this reason, unstable isotopes can be used to determine when minerals in an igneous rock crystallized and when pressure and heat created new minerals in a metamorphic rock. However, samples of sedimentary rock can only rarely be dated directly by radiometric means. Although a detrital sedimentary rock may include particles that contain unstable isotopes, the rock's age cannot be accurately determined because the grains composing the rock are not the same age as the rock in which they occur. Rather, the sediments have been weathered from rocks of diverse ages. Radiometric dates obtained from metamorphic rocks may also be difficult to interpret because the age of a particular mineral in a metamorphic rock does not necessarily represent the time when the rock initially formed. Instead, the date might indicate any one of a number of subsequent metamorphic phases.
Liquefaction
The process by which an earthquake's violent movement suddenly turns loose soil into liquid mud
partial melting
The process by which most igneous rocks melt. Since individual minerals have different melting points, most igneous rocks melt over a temperature range of a few hundred degrees. If the liquid is squeezed out after some melting has occurred, a melt with a higher silica content results.
stream piracy
The process by which one stream captures the headwaters of another stream
Hess's Seafloor spreading
The process of producing new seafloor between two diverging plates.
lithification of sediment
The process that converts sediments into solid rock by compaction or cementation.
offshore zone
The relatively flat submerged zone that extends from the breaker line to the edge of the continental shelf.
North Atlantic Currents
The relatively warm waters of the North Atlantic Drift are responsible for moderating the climate of western Europe, so that winters are less cold than would otherwise be expected at its latitude. Without the warm North Atlantic Drift, the UK and other places in Europe would be as cold as Canada, at the same latitude.
lithosphere
The rigid outer layer of Earth, including the crust and upper mantle.
Unconformities in the Grand Canyon
The rocks exposed in the Grand Canyon of the Colorado River represent a tremendous span of geologic history. It is a wonderful place to take a trip through time. The canyon's colorful strata record a long history of sedimentation in a variety of environments—advancing seas, rivers and deltas, tidal flats and sand dunes. But the record is not continuous. Unconformities represent vast amounts of time that have not been recorded in the canyon's layers.
water hemisphere
The roughly one-half of the Earth that contains most of the surface water; the opposite of the land hemisphere - southern hemisphere
P and S wave shadow zones
The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves. The shadow zone results from S waves being stopped entirely by the liquid core and P waves being bent (refracted) by the liquid core.
Factors Affecting Flow Velocity: Gradient
The slope of a stream channel expressed as the vertical drop of a stream over a specified distance. By contrast, some mountain stream channels decrease in elevation at a rate of more than 40 meters per kilometer, a gradient 400 times steeper than the lower Mississippi. Gradient also varies along the length of a particular channel. When the gradient is steeper, more gravitational energy is available to drive channel flow.
Hydraulic gradient
The slope of the water table. It is determined by finding the height difference between two points on the water table and dividing by the horizontal distance between the two points.
wave-cut platform
The smooth, level terrace sometimes found on erosional coasts that marks the submerged limit of rapid marine erosion.
slip face
The steep, leeward slope of a sand dune; it maintains an angle of about 34 degrees.
Supercontinents and Sea-Level Changes
The supercontinent cycle and sea-level changes are directly related to rates of seafloor spreading. When the rate of spreading is rapid, as it is along the East Pacific Rise today, the production of warm oceanic crust is also high. Because new, warm oceanic crust is less dense (takes up more space) than cold crust, fast-spreading ridges occupy more volume in the ocean basins than do slow-spreading centers. (Think of getting into a tub filled with water.) As a result, when rates of seafloor spreading increase, more seawater is displaced, which results in the sea level rising. This, in turn, causes shallow seas to advance onto the low-lying portions of the continents.
half-life
The time required for one half of the atoms of a radioisotope to emit radiation an decay products. When the quantities of parent and daughter are equal (ratio 1:1), we know that one half-life has transpired. When one-quarter of the original parent atoms remain and three-quarters have decayed to the daughter product, the parent/daughter ratio is 1:3, and we know that two half-lives have passed. After three half-lives, the ratio of parent atoms to daughter atoms is 1:7 (one parent atom for every seven daughter atoms). If the half-life of a radioactive isotope is known and the parent/daughter ratio can be determined, the age of the sample can be calculated. For example, assume that the half-life of a hypothetical unstable isotope is 1 million years, and the parent/daughter ratio in a sample is 1:15. This ratio indicates that four half-lives have passed and that the sample must be 4 million years old. Notice that the percentage of radioactive atoms that decay during one half-life is always the same: 50 percent. However, the actual number of atoms that decay with the passing of each half-life continually decreases. Thus, as the percentage of radioactive parent atoms declines, the proportion of stable daughter atoms rises, with the increase in daughter atoms just matching the drop in parent atoms. This fact is the key to radiometric dating.
Plate Tectonic setting for volcanism
The two types of plate boundaries that are most likely to produce volcanic activity are divergent plate boundaries and convergent plate boundaries. Non-explosive found at spreading centers and hotspots Explosive found at convergent plate boundary (subduction zone)
hydrologic cycle
The unending circulation of Earth's water supply. The cycle is powered by energy from the Sun and is characterized by continuous exchanges of water among the oceans, the atmosphere, and the continents. •Evaporation from oceans forms clouds •Precipitation from clouds over oceans and continents •Infiltration to form groundwater •Runoff to form streams -Groundwater and streams eventually travel back to oceans •Transpiration by plants
wave height
The vertical distance between trough and crest
Height of water table varies seasonally
The water table level can vary in different areas and even within the same area. Fluctuations in the water table level are caused by changes in precipitation between seasons and years. During late winter and spring, when snow melts and precipitation is high, the water table rises.
ionic compounds
When one ion is attracted to and joins one another ion of the opposite charged
Global Atmospheric Circulation
The worldwide system of winds, which transports heat from tropical to polar latitudes. In each hemisphere, air also circulates through the entire depth of the troposphere which extends up to 15 km.
Quaternary Period
The youngest geologic period; includes the present time.
Elastic Rebound on Fault
Then they separate with a rupture along the fault; the sudden movement releases accumulated energy, and the rocks snap back almost to their original shape
Putting together geologic history of an area
There are two important tools that geologists use to portray the history of the Earth: the geologic time scale and paleogeographic maps.
A river system includes not only its network of stream channels but its entire drainage basin. It can be divided into three zones, based on the process that dominates in each.
These are the zones of sediment production (where erosion dominates), sediment transport, and sediment deposition **It is important to recognize that sediment is being eroded, transported, and deposited along the entire length of a stream, regardless of which process is dominant within each zone.
Formation of Glacial Deposits
These deposits, known collectively as drift , are made up of crushed and mixed rock fragments picked up by the ice along its path. During the final stages of ice movement and especially upon stagnation and decay of the glacier, the sediments carried by the ice are deposited on the land surface.
Factors Affecting Flow Velocity
These factors include (1) channel slope, or gradient, (2) channel size and cross-sectional shape, (3) channel roughness, and (4) the amount of water flowing in the channel: - Velocity greatest in center - Inertia moves high velocity to outside of bend
textural categories
These have been established because soild rarely consist of particles of only one size
In addition to sand and gravel bars, streams also create other depositional features that have somewhat longer life spans
These include deltas, natural levees, and alluvial fans.
high-resolution multibeam sonar
These systems use hull-mounted sound sources that send out a fan of sound and then record reflections from the seafloor through a set of narrowly focused receivers aimed at different angles.
Global earthquake belts
These zones of earthquake activity are located along fault surfaces where tectonic plates interact along one of the three types of plate boundaries—convergent, divergent, and transform plate boundaries.
dendritic pattern
This pattern of irregularly branching tributary streams resembles the branching pattern of a deciduous tree. In fact, the word dendritic means "treelike." The dendritic pattern forms where the underlying material is relatively uniform. Because the surface material is essentially uniform in its resistance to erosion, it does not control the pattern of streamflow. Rather, the pattern is determined chiefly by the direction of slope of the land.
As is the case with other agents of erosion, the rate of glacial erosion is highly variable.
This rate is largely controlled by four factors: (1) speed of glacier movement; (2) ice thickness; (3) shape, abundance, and hardness of the rock fragments in the ice at the base of the glacier; and (4) erodibility of the surface beneath the glacier. These factors can all vary from place to place and from one time to another, with resulting variation in the degree of landscape modification.
Semidiurnal
This type of tidal cycle is found commonly in the Atlantic and Pacific Oceans.
About one-quarter of global precipitation falls on land and flows on and below the surface
This water is the most important force sculpturing Earth's land surface.
Daily variation in relative humidity
Thus, the relative humidity increases as the temperature falls toward the dew point and decreases as it rises. The humidity drops during the day as the temperature rises and usually reaches its lowest value in the middle or late afternoon when the day's maximum temperature is recorded.
The properties of a chemical compound are dramatically different from the properties of the various elements comprising it.
Thus, when elements combine to form compounds, their properties change significantly.
Variations in Earth's Orbit
Today, many scientists strongly suspect that the climatic oscillations that characterized the Quaternary may be linked to changes in Earth's orbit. This hypothesis was first developed and strongly advocated by Serbian scientist Milutin Milankovitch and is based on the premise that variations in incoming solar radiation are a principal factor in controlling Earth's climate. Milankovitch formulated a comprehensive mathematical model based on the following elements : - Variations in the shape (eccentricity) of Earth's orbit about the Sun - Changes in obliquity—that is, changes in the angle that Earth's axis makes with the plane of its orbit - The wobbling of Earth's axis, called precession
Seafloor topography (from sonar)
Topographic (bathymetric) features •Continental shelf •Continental slope •Continental rise •Abyssal plain •Mid-Ocean ridge •Seamounts •Guyots •Deep sea trenches •Atolls •Submarine canyons •Deep sea fans
Conditions Favoring Preservation
Two special conditions favor fossilization: rapid burial and the possession of hard parts. When an organism perishes, its soft parts usually are quickly eaten by scavengers or decomposed by bacteria. Occasionally, however, the remains are buried by sediment. When this occurs, the remains are protected from the surface environment, where destructive processes operate. Rapid burial, therefore, is an important condition favoring preservation. In addition, animals and plants have a much better chance of being preserved as part of the fossil record if they have hard parts. Although traces and imprints of soft-bodied animals such as jellyfish, worms, and insects exist, they are not common. Flesh usually decays so rapidly that preservation is exceedingly unlikely. Hard parts such as shells, bones, and teeth predominate in the record of past life. Because preservation is contingent on special conditions, the record of life in the geologic past is biased. The fossil record of those organisms with hard parts that lived in areas of sedimentation is quite abundant. However, we get only an occasional glimpse of the vast array of other life-forms that did not meet the special conditions favoring preservation.
Groundwater flow paths
Under natural conditions, ground water moves along flow paths from areas of recharge to areas of discharge at springs or along streams, lakes, and wetlands. Discharge also occurs as seepage to bays or the ocean in coastal areas, and as transpiration by plants whose roots extend to near the water table.
If samples of sedimentary rocks rarely yield reliable radiometric ages, how can numerical dates be assigned to sedimentary layers?
Usually geologists must relate the strata to datable igneous masses. For example, radiometric dating has determined the ages of the volcanic ash bed in the Morrison Formation and the dike cutting the Mancos Shale and Mesaverde Formation. The sedimentary beds below the ash are obviously older than the ash, and all the layers above the ash are younger (based on the principle of superposition). The dike is younger than the Mancos Shale and the Mesaverde Formation but older than the Wasatch Formation because the dike does not intrude this topmost layer (based on the principle of cross-cutting relationships).
Mass Balance through the Year
Usually, the net mass balance over the balance year is plotted on a graph. There are several projects monitoring glaciers all over the world, and these analyses show that glacier mass balance is generally decreasing (becoming more negative) over time.
soil formation: topography
Variations in topography can lead to the development of a variety of localized soil types. Many of the differences exist because the length and steepness of slopes have a significant impact on the amount of erosion and the water content of soil. The optimum terrain for soil development is a flat-to-undulating upland surface, where there is good drainage, minimum erosion, and sufficient infiltration of water into the soil. Slope orientation, or the direction a slope is facing, also is significant
Temperature and salinity affect seawater density-causes a vertical stratification
Vertical Stratification •Surface mixed zone (100-500 m) •Transition zone and deep zone •Stratification seen in thermocline, halocline, and pycnocline •Stratification important to deep water circulation patterns
rock avalanches
Very rapid downslope movement of rock and debris. These rapid movements may be aided by a layer of air trapped beneath the debris, and they have been known to reach speeds of over 200 kilometers (125 miles) per hour.
Natural Processes Examples
Volcanic Eruptions, Floods, Tsunamis, Earthquakes, Landslides, and Hurricanes
calving
Wastage of a glacier that occurs when large pieces of ice break into the water.
stream develops
Water from some source like a spring, snow melt, or a lake starts at this high point and begins to flow down to lower points. As the water flows down, it may pick up more water from other small streams, springs or or from rain or snow melt. These streams may slowly join together to form a larger stream or river.
Water changes of state
Water is a liquid at room temperature, but becomes a solid (called ice) if it is cooled down. The same water turns into a gas (called water vapor) if it is heated up. The changes only happen when the substance reaches a particular temperature. Water turns to ice at 32ºF (0ºC).
Water Table follows topography
Water tables often (but not always) follow the topography, or upward and downward tilts, of the land above them. Sometimes, a water table runs intersects with the land surface.
runoff
Water that moves across the land surface and into streams and rivers
Soil as an interface
When Earth is viewed as a system, soil is referred to as an interface -- a common boundary where different parts of a system interact. Soil forms where the geosphere, the atmosphere, the hydrosphere, and the biosphere meet. Over time, soil gradually evolves to a state of equilibrium w/ the environment.
Tight fold
When a fold has a small angle between folds
Sediment Deposition
When a river reaches a large body of water, the energy decreases and the river deposits sediments **When a river reaches the ocean or another large body of water, it slows, and the energy to transport sediment is greatly reduced. Most of the sediment either accumulates at the mouth of the river to form a delta, is reconfigured by wave action to form a variety of coastal features, or is moved far offshore by ocean currents. Because coarse sediment tends to be deposited upstream, it is primarily the fine sediment (clay, silt, and fine sand) that eventually reaches the ocean. Taken together, erosion, transportation, and deposition are the processes by which rivers move Earth's surface materials and sculpt landscapes.
Molds and Casts
When a shell or another structure is buried in sediment and then dissolved by underground water, a mold is created. The mold faithfully reflects the shape and surface marking of the organism; however, it does not reveal any information concerning its internal structure. If these hollow spaces are subsequently filled with mineral matter, casts are created
Valley Deepening
When a stream's gradient is steep and the channel is well above base level, downcutting is the dominant activity. Abrasion caused by bed load sliding and rolling along the bottom and the hydraulic power of fast-moving water slowly lower the streambed. The result is usually a V-shaped valley with steep sides. A classic example of a V-shaped valley is the section of the Yellowstone River
Classifying Mass Movements: Type of Motion
When mass movement involves the free falling of detached individual pieces of any size, it is termed a fall. Falls are common on slopes that are too steep for loose material to remain on the surface. Many falls result when freeze-thaw cycles and/or the action of plant roots loosen rock and then gravity takes over. Rockfall is the primary way in which talus slopes are built and maintained (see Figure 8.5). Sometimes falls may trigger other forms of downslope movement.
optical properties of minerals: Ability to Transmit Light
When no light is transmitted through a mineral sample, that mineral is described as opaque; when light, but not an image, is transmitted, the mineral is said to be translucent. When both light and an image are visible through the sample, the mineral is described as transparent.
Earth's water as storage in glaciers
When precipitation falls in very cold places—at high elevations or high latitudes—the water may not immediately soak in, run off, or evaporate. Instead, it may become part of a snowfield or glacier. In this way, glaciers store large quantities of water on land
Evaporative Salts
When seawater evaporates, the salts increase in concentration until they can no longer remain dissolved; they then precipitate out of solution and form salt deposits, which can then be harvested. The most economically important salt is halite (common table salt). Halite is widely used for seasoning, curing, and preserving foods. It is also used in water conditioners, in agriculture, in the clothing industry for dying fabric, and to de-ice roads. Since ancient times, the ocean has been an important source of salt for human consumption, and the sea remains a significant supplier
radial
When streams diverge from a central area like spokes from the hub of a wheel **This pattern typically develops on isolated volcanic cones and domal uplifts
Oceanic-Continental Convergence
When the leading edge of a plate capped with continental crust converges with a slab of oceanic lithosphere, the buoyant continental block remains "floating," while the denser oceanic slab sinks into the mantle. When a descending oceanic slab reaches a depth of about 100 kilometers (60 miles), melting is triggered within the wedge of hot asthenosphere that lies above it
Changes in Sun's angle changes amount of energy on surface
When the sun's rays strike Earth's surface near the equator, the incoming solar radiation is more direct (nearly perpendicular or closer to a 90˚ angle). ... At higher latitudes, the angle of solar radiation is smaller, causing energy to be spread over a larger area of the surface and cooler temperatures
conformable
When we observe layers of rock that have been deposited essentially without interruption. Particular sites exhibit conformable beds representing certain spans of geologic time. However, no place on Earth has a complete set of conformable strata that represents the entire history of Earth.
sequence of formation for rocks
When we place rocks in their proper sequence of formation—indicating which formed first, second, third, and so on—we are establishing relative dates
Paired metamorphic belts
When you see greenschist running parallel to blueschist in PAIRED BELTS. -You know there must have been a subduction zone there.
Oceanic-Oceanic Convergence
Where two oceanic slabs converge, one descends beneath the other, initiating volcanic activity by the same mechanism that operates at all subduction zones. Water released from the subducting slab of oceanic lithosphere triggers melting in the hot wedge of mantle rock above. In this setting, volcanoes grow up from the ocean floor rather than upon a continental platform. Sustained subduction eventually results in a chain of volcanic structures large enough to emerge as islands.
wind abrasion
Wind sandblasts rock in dry, arid climates and rounds out the rock
Wind-transport of sediment
Wind transports small particles, such as silt and clay, over great distances, even halfway across a continent or an entire ocean basin. Particles may be suspended for days. Wind more easily picks up particles on ground that has been disturbed, such as a construction site or a sand dune.
Cirrus
Wispy, feathery clouds made of ice crystals that form at high levels.
Because glaciers are sensitive to changes in temperature and precipitation, they provide clues about changes in climate.
With few exceptions, valley glaciers around the world have been retreating at unprecedented rates over the past century. Many valley glaciers have disappeared altogether. For example, 150 years ago, there were 147 glaciers in Montana's Glacier National Park. Today only 37 remain. Greenland's ice sheet and portions of Antarctica's ice are also shrinking.
Correlation Within Limited Areas
Within a limited area, geologists can correlate rocks of one locality with those of another by simply walking along the outcropping edges, but this may not be possible when the rocks are mostly concealed by soil and vegetation. Correlation over short distances is often achieved by noting the position of a bed in a sequence of strata. Or a layer may be identified in another location if it is composed of distinctive or uncommon minerals. However, when correlation between widely separated areas or between continents is the objective, geologists must rely on fossils.
nuclear fusion
Within the cores of these early stars, heating triggered the process of nuclear fusion, in which hydrogen nuclei combine to form helium nuclei, releasing enormous amounts of radiant energy (heat, light, and cosmic rays).
Ogallala aquifer
World's largest aquifer; under parts of Wyoming, South Dakota, Nebraska, Kansas, Colorado, Oklahoma, New Mexico, and Texas (the Midwest). Holds enough water to cover the U.S. with 1.5 feet of water. Being depleted for agricultural and urban use.
Surging Yanert Glacier-Alaska
Yanert is experiencing the complexion problems characteristic of surging glaciers, which differ from most glaciers in Alaska. After grinding along for decades, surging glaciers suddenly move with unexpected speed.
seismic waves
a form of energy that travels through the lithosphere and Earth's interior
index fossils
a fossil that is associated with a particular span of geologic time
Deep time
a framework for considering the span of human history within the much larger age of the universe and planet earth
groin
a barrier built at a right angle to the beach to trap sand that is moving parallel to the shore. Groins are usually constructed of large rocks but may also be composed of wood. These structures often do their job so effectively that the longshore current beyond the groin becomes sand-starved. As a result, the current erodes sand from the beach on the downstream side of the groin.
aquifers
a body of permeable rock that can contain or transmit groundwater.
proglacial lakes
a body of water impounded in front of a glacier.
subduction zones
a boundary where ocean-ocean or continent-ocean plates are pushed down into the mantle; causes volcanoes and earthquakes
contact zone
a boundary which separates one rock body from another
fault
a break in a rock mass caused by a shifting of the earth's crust
Joints
a brittle-fracture surface in rocks along which little or no displacement has occurred. Present in nearly all surface rocks, joints extend in various directions, generally more toward the vertical than to the horizontal.
volcanic island arc
a chain of volcanic islands generally located a few hundred kilometers from a trench where there is active subduction of one oceanic plate beneath another
Reversals of the Geomagnetic field
a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged (not to be confused with geographic north and geographic south).
Atmospheric effects on radiation
a change in the spectral content of the solar radiation due to greater absorption or scattering of some wavelengths; the introduction of a diffuse or indirect component into the solar radiation
Shuram C-isotope excursion
a change in δ13C, or in the ratio of carbon-13 to carbon-12, starting around 551 million years ago
radiocarbon dating
a chemical analysis used to determine the age of organic materials based on their content of the radioisotope carbon-14
sinkhole
a circular depression formed when the roof of a cave collapses
dry climate
a climate in which yearly precipitation is less than the potential loss of water by evaporation
Rainshadow Desert
a climate region that forms on the side of a mountain range sheltered from the prevailing winds
Cirrocumulus
a cloud at a high altitude consisting of a series of regularly arranged small clouds resembling ripples
metasedimentary rocks: marble
a coarse, crystalline rock whose parent rock is limestone
submergent coasts
a coast at which the land is sinking relative to sea level
lithospheric plates
a coherent unit of Earth's rigid outer layer that includes the crust and the upper mantle
Chemical Sedimentary Rocks: Coal
a combustible black or dark brown rock consisting mainly of carbonized plant matter, found mainly in underground deposits and widely used as fuel.
interface
a common boundary where different parts of a system interact. This is certainly an appropriate designation for the coastal zone. Here we can see the rhythmic rise and fall of tides and observe waves rolling in and breaking. Sometimes the waves are low and gentle. At other times they pound the shore with awesome fury.
Common Light Silicate Minerals: Muscovite
a common member of the mica family. It is light in color and has a pearly luster
the Earth System
a complex and continuously changing interacting whole
deep-sea fan
a cone-shaped deposit at the base of the continental slope. the sediment is transported to the fan by turbidity currents that follow submarine canyons
cone of depression
a cone-shaped depression in the water table immediately surrounding a well
point bar
a crescent-shaped accumulation of sand and gravel deposited on the inside of a meander
longitudinal profile
a cross-sectional view of a stream from its source area (called the head or headwaters) to its mouth, the point downstream where the river empties into another water body—a river, a lake, or an ocean
oxbow lake
a curved lake that is created when a stream cuts off a meander
Dark silicate minerals: Biotite
a dark, iron-rich member of the mica family & like other micas, biotite possesses a sheet structure that gives it excellent cleavage in one direction
relative date
a date that results from placing rocks in their proper sequence or order to determine the chronological order of events•Steno's Law of Superposition •Steno's Law of Original Horizontality •Steno's Law of Original Continuity -Sedimentary facies •Cross-cutting relationships •Unconformities -Angular unconformity (like Siccar Point) -Disconformity -Nonconformity
numerical date
a date that specifies that actual number of years that have passed since an event occurred. Such dates specify the actual number of years that have passed since an event occurred. Today, our understanding of radioactivity allows us to accurately determine numerical dates for rocks that represent important events in Earth's distant past.
crevasses
a deep crack in the brittle surface of a glacier
Core
a dense inner sphere
interior drainage
a discontinuous pattern of intermittent streams that do not flow to the ocean
Disconformity
a gap in the rock record that represents a period during which erosion rather than deposition occurred. Imagine that a series of sedimentary layers is deposited in a shallow marine setting. Following this period of deposition, sea level falls or the land rises, exposing some the sedimentary layers. During this span, when the sedimentary beds are above sea level, no new sediment accumulates, and some of the existing layers are eroded away. Later, sea level rises or the land subsides, submerging the landscape. Now the surface is again below sea level, and a new series of sedimentary beds is deposited. The boundary separating the two sets of beds is a disconformity—a span for which there is no rock record. Because the layers above and below a disconformity are parallel, these features are sometimes difficult to identify unless you notice evidence of erosion such as a buried stream channel.
Pediment
a gently sloping erosion surface or plain of low relief formed by running water in arid or semiarid region at the base of a receding mountain front. A pediment is underlain by bedrock that is typically covered by a thin, discontinuous veneer of soil and alluvium derived from upland areas
continental shelf
a gently sloping, submerged surface that extends from the shoreline toward the deep-ocean basin. It consists mainly of continental crust capped with sedimentary rocks and sediments eroded from adjacent landmasses.
valley glaciers
a glacier confined to a mountain valley, which in most instances had previously been a stream valley; also known as an alpine glacier
piedmont glacier
a glacier that forms when one or more valley glaciers emerge from the confining walls of mountain valleys and spread out to create a broad sheet in the lowlands at the base of the mountains. The advancing ice spreads out to form a broad sheet. The size of individual piedmont glaciers varies greatly. Among the largest is the broad Malaspina Glacier, along the coast of southern Alaska. It covers more than 5000 square kilometers (2000 square miles) of the flat coastal plain at the foot of the lofty St. Elias range
System
a group of interacting, interrelated, or interdependent elements or parts that function together as a whole to accomplish a goal
geysers
a hot spring in which water intermittently boils, sending a tall column of water and steam into the air.
lava fountain
a jet of lava sprayed into the air by the rapid formation and expansion of gas bubbles in the molten rock (Low viscosity)
kettle lake
a lake that forms when a block of ice falls off of the glacial front, is buried by glacial drift, and then melts, forming a depression that fills with water.
protoplanets
a large body of matter in orbit around the sun or a star and thought to be developing into a planet
solar nebula
a large rotating cloud of interstellar dust and gas
accretionary wedge
a large wedge-shaped mass of sediment that accumulates in subduction zones; Here sediment is scraped from the subducting oceanic plate and accreted to the overriding crustal block
shields
a large, relatively flat expanse of ancient metamorphic rock within the stable continental interior
cratons
a large, stable block of the earth's crust forming the nucleus of a continent.
Sedimentary Structures: graded beds
a layer of sediment in which grain size varies from coarse at the bottom to fine at the top **end of the continent
iceberg
a mass of floating ice that has broken away from a calving glacier. Along the margins of Antarctica's ice shelves, calving is the primary means by which the ice shelves lose mass. The relatively flat icebergs produced here can be several kilometers across and 600 meters (2000 feet) thick. By comparison, thousands of irregularly shaped icebergs are produced by outlet glaciers flowing from the margins of the Greenland Ice Sheet. Many drift southward and find their way into the North Atlantic, where they can be hazardous to navigation.
ice caps
a mass of glacial ice covering a high upland or plateau and spreading out radially
mudslide
a mass of mud and other earthy material that is falling or has fallen down a hillside or other slope.
slab pull
a mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and "pulls" the trailing lithosphere along
ridge push
a mechanism that may contribute to plate motion; it involves the oceanic lithosphere sliding down the oceanic ridge under the pull of gravity
glacial trough
a mountain valley that has been widened, deepened, and straightened by a glacier
lahars
a mudflow that results from a volcanic eruption
arêtes
a narrow, knifelike ridge separating two adjacent glaciated valleys
Exoplanet
a planet that orbits a star outside the solar system
back swamps
a poorly drained area on a flood-plain resulting when natural levees are present
Principle of Cross-Cutting Relationships
a principle of relative dating; a rock or fault is younger than any rock or fault through which it cuts. The magmatic heat from igneous intrusions often creates a narrow "baked" zone of contact metamorphism on the adjacent rock, also indicating that the intrusion occurred after the surrounding rocks were in place.
subduction erosion
a process in subduction zones in which sediment and rock are scraped off the bottom of the overriding plate and transported into the mantle
inertia
a property of matter that resists a change in its motion
electrical charge
a property of matter that tells whether something has a positive or negative charge (Protons have an electrical charge of +1, and electrons have a charge of −1. Neutrons, as the name suggests, have no charge)
geologic time scale
a record of the geologic events and life forms in Earth's history
trellis pattern
a rectangular drainage pattern in which tributary streams are nearly parallel to one another and have the appearance of a garden trellis. This pattern forms in areas underlain by alternating bands of resistant and less-resistant rock.
mantle convection
a recurring current in the mantle that occurs when hotter, less dense material rises, cools, and then sinks again. This current is believed to be one of the driving forces behind tectonic plate movement.
divergent plate boundaries
a region where the rigid plates are moving apart, typified by the mid-ocean ridges (aka spreading center) •Seafloor spreading •Mid-ocean ridge •Rifts and rift valleys •Ophiolites •Structure of seafloor -Pillow lavas -Vertical dikes -Gabbroic magma chambers
The High Plains
a relatively dry region that extends from South Dakota to western Texas, is one example of an extensive agricultural economy that is largely dependent on irrigation using groundwater (Figure 9.37). Underlying about 111 million acres (450,000 square kilometers [174,000 square miles]) in parts of eight states, the High Plains aquifer is one of the largest and most agriculturally significant aquifers in the United States. It accounts for about 30 percent of all groundwater withdrawn for irrigation in the country. In the southern part of this region, which includes the Texas panhandle, the natural recharge of the aquifer is very slow, and the problem of declining groundwater levels is acute. In fact, in years of average or below-average precipitation, recharge is negligible because all or nearly all of the meager rainfall is returned to the atmosphere by evaporation and transpiration.
outwash plain
a relatively flat, gently sloping plain consisting of materials deposited by meltwater streams in front of the margin of an ice sheet
valley train
a relatively narrow body of stratified drift deposited on a valley floor by meltwater streams that issue from a valley glacier
debris flow/mudflows
a relatively rapid type of mass wasting that involves a flow of soil and regolith containing a large amount of water
continental slope
a relatively steep zone that marks the boundary between continental crust and oceanic crust. Although the inclination of the continental slope varies greatly from place to place, it averages about 5 degrees and in places exceeds 25 degrees.
renewable
a resource that is virtually inexhaustible or that can be replenished over relatively short time spans
thrust fault (compressional)
a reverse fault in which the hanging wall slides over to the foot wall
lateral moraines
a ridge of till along the sides of an alpine glacier composed primarily of debris that fell to the glacier from the valley walls
end moraines
a ridge of till that forms at the terminus of a glacier or ice sheet whenever the terminus is stationary. That is, the end moraine forms when the ice is wasting away near the end of the glacier at a rate equal to the forward advance of the glacier
Igneous rock: granitic composition
a rock composed almost entirely of light-colored silicates (aka felsic comp)
Rip current
a rush of water that flows rapidly back to sea through a narrow opening
Baymouth Bar
a sandbar that completely crosses a bay, sealing it off from the open ocean
baymouth bar
a sandbar that completely crosses a bay, sealing it off from the open ocean
distributaries
a section of a stream that leaves the main flow
Ophiolites
a section of the Earth's oceanic crust and the underlying upper mantle that has been uplifted or emplaced to be exposed within continental crustal rocks
turbidites
a sediment or rock deposited by a turbidity current.
tillite
a sedimentary rock formed when glacial till becomes lithified
seismic gap
a segment of an active fault known to produce significant earthquakes that has not slipped in an unusually long time, compared with other segments along the same structure.
Bowen's Reaction Series/fractional crystallization
a sequence that tells you what mineral to expect from magma according at temp it cools at
Mineral Strength: Hardness - Mohs scale of hardness
a series of 10 minerals arranged in order from 1 (softest) to 10 (hardest)
cutoff
a short channel segment created when a river erodes through the narrow neck of land between meanders
Concordant-Sill
a slab of volcanic rock formed when magma squeezes between layers of rock
landslide
a slide of a large mass of dirt and rock down a mountain or cliff
tarn
a small mountain lake or pool, especially one in a cirque.
artesian spring
a spring whose water flows from a crack in the cap rock over the aquifer
fiord
a steep-sided inlet of the sea that formed when a glacial trough was partially submerged. Norway, British Columbia, Greenland, New Zealand, Chile, and Alaska all have coastlines characterized by fiords. They are glacial troughs that became submerged as the ice left the valleys and sea level rose following the Ice Age.
kames
a steep-sided mound of sand and gravel deposited by a melting ice sheet.
mineral resources
all discovered and undiscovered deposits of a useful mineral that can be extracted now or at some time in the future
braided channels
a stream consisting of numerous intertwining channels. One setting in which braided streams form is at the end of glaciers, where there is a large seasonal variation in discharge. During the summer, large amounts of ice-eroded sediment are dumped into the meltwater streams flowing away from the glacier. However, when flow is sluggish, the stream deposits the coarsest material as elongated structures called bars. The flow then splits into several paths around the bars. During the next period of high flow, the laterally shifting channels erode and redeposit much of this coarse sediment, thereby transforming the entire streambed. In some braided streams, the bars have built semipermanent islands anchored by vegetation. •Braided streams occur when the sediment load is so high, that sediments are deposited in stream channels •Typically streams that carry meltwater from glaciers have such a high sediment load they are braided
silicon-oxygen tetrahedron
a structure composed of four oxygen atoms surrounding a silicon atom that constitutes the basic building block of silicate minerals
chemical compounds
a substance formed from two or more elements chemically united in fixed proportions
Explosive eruption-nuee ardente
a superheated, incandescent cloud of gas and volcanic ash that flows swiftly down a volcanic slope as an avalanche.
Sonar
a system for the detection of objects under water and for measuring the water's depth by emitting sound pulses and detecting or measuring their return after being reflected.
stalactites
a tapering structure hanging like an icicle from the roof of a cave, formed of calcium salts deposited by dripping water.
X ray diffraction (XRD)
a technique for determining the arrangement of atoms or ions in a crystal by analyzing the pattern that results when X-rays are scattered after bombarding the crystal
Hypothesis
a tentative (or untested) explanation of why something occurs → a hypothesis must fit observations other than those used to formulate them in the first place → before a hypothesis can become an accepted part of scientific knowledge, it must repeatedly pass objective testing + analysis
Common Light Silicate Minerals: Clay Minerals/Clay
a term used to describe a category of complex minerals that, like the micas, have a sheet structure. Unlike other common silicates, most clay minerals originate as products of the chemical breakdown (chemical weathering) of other silicate minerals
Bergeron Process
a theory that relates the formation of precipitation to supercooled clouds, freezing nuclei, and the different saturation levels of ice and liquid water
continental drift
a theory which originally proposed that the continents are rafted about •Proposed by Wegener in 1915 •Evidence -Fit of continents -Match of fossils -Match of structures and rock types -Ancient glaciations •Not accepted by geologic community -Lack of driving mechanism
glacier
a thick ice mass that forms over hundreds or thousands of years •Ice as a Rock •Types of Glaciers -Valley (Alpine) -Continental Ice Sheet -Ice Caps -Piedmont
Common Light Silicate Minerals: Quartz
a three-dimensional framework is developed through the complete sharing of oxygen by adjacent silicon atoms; all the bonds in quartz are of the strong silicon-oxygen type; is hard, resists weathering, and does not have cleavage
spring tides
a tide just after a new or full moon, when there is the greatest difference between high and low water.
periodic table
a tool scientists use to organize the known elements
yazoo tributary
a tributary that flows parallel to the main stream because a natural levee is present
hanging valleys
a tributary valley that enters a glacial trough at a considerable height above the floor of the trough
Strike Slip Fault (shear)
a type of fault where rocks on either side move past each other sideways with little up or down motion
reverse fault (compressional)
a type of fault where the hanging wall slides upward; caused by compression in the crust
primary waves
a type of seismic wave that compresses and expands the ground. also called a P wave.
Greenland-Continental Ice Sheet
a vast body of ice covering 1,710,000 square kilometres (660,000 sq mi), roughly 79% of the surface of Greenland.
soil profile
a vertical section through a soil showing its succession of horizons and the underlying parent material •Soil processes act from top down to form soils •Mainly due to percolation of water •O horizon-organics •A horizon-mainly mineral, but humus important •O and A are topsoil •E horizon-eluviation, leaching •B horizon-zone of accumulation, subsoil, rich in clay •C horizon-partly weathered parent material
metasedimentary rocks: quartzite
a very hard metamorphic rock most often formed from quartz sandstone
ice sheets
a very large, thick mass of glacial ice flowing outward in all directions from one or more accumulation center(s). Presently, each of Earth's polar regions supports an ice sheet: on Greenland in the Northern Hemisphere and on Antarctica in the Southern Hemisphere
marine terrace
a wave-cut platform that has been exposed above sea level
artesian well
a well created by drilling a hole into a confined aquifer
Theory
a well-tested and widely accepted view that is agreed to best explain certain observable facts
importance of rock cycle
allows us to see many of the interactions among the components and processes of the Earth system. It helps us understand the origins of igneous, sedimentary, and metamorphic rocks and how these rocks are connected. In addition, the rock cycle demonstrates that any rock type, given the right sequence of events, can be transformed into any other type.
Sandstone
an abundant, durable sedimentary rock primarily composed of sand sized grains.
beach
an accumulation of sediment found along the landward margin of an ocean or a lake. Along straight coasts, beaches may extend for tens or hundreds of kilometers. Where coasts are irregular, beach formation may be confined to the relatively quiet waters of bays.
glacial drift
an all-embracing term for sediments of glacial origin, no matter how, where, or in what form they were deposited
cirque
an amphitheater-shaped basin at the head of a glaciated valley produced by frost wedging and plucking
confined aquifer
an aquifer surrounded by a layer of impermeable rock or clay that impedes water flow
sea arch
an arch formed by wave erosion when caves on opposite sides of a headland unite
floodplain
an area along a river that forms from sediments deposited when the river overflows its banks
coast
an area of land near the ocean
asperity
an area on a fault that is stuck or locked
deep-ocean trench
an elongated depression in the seafloor produced by bending of oceanic crust during subduction
spit
an elongated ridge of sand that projects from the land into the mouth of an adjacent bay. Often the end in the water hooks landward in response to the dominant direction of the longshore current.
seed
an embryo packaged with a supply of nutrients inside a protective coating
electron shells
an energy level of electrons at a characteristic average distance from the nucleus of an atom → further away from nucleus = more energy the electrons have
fissure eruptions
an eruption in which lava is extruded from narrow fractures or cracks in the crust
trigger
an event, such as an earthquake or heavy rainfall, that initiates a mass movement process
Green River Formation
an example of a massive graveyard in southwestern Wyoming, a lot of fish have been found here embedded in beds of fossils
supernova
an exploding star that increases in brightness many thousands of times
oceanic plateaus
an extensive region on the ocean floor composed of thick accumulation of pillow basalts and other mafic rocks.
divide
an imaginary line that separates the drainage of two streams; often found along a ridge
Potentiometric Surface
an imaginary surface that defines the level to which water in a confined aquifer would rise were it completely pierced with wells
Seismograph
an instrument that records earthquake waves •Seismometer measures ground motion due to passing seismic waves •A mass (weight) provides an inertial reference while body of seismometer is anchored to bedrock •Complete seismometer station measures two horizontal components and vertical component
echo sounders
an instrument used to determine the depth of water by measuring the time interval between emission of a sound signal and the return of its echo from the bottom
lava skylight
an opening in the roof of an underground lava tube (Low viscosity)
flood
an overflowing of a large amount of water beyond its normal confines, especially over what is normally dry land. •Stream overflows banks •Flows onto floodplain •Natural levee formation •Periodicity of flooding -Bankfull stage 1-2 years filled channel -Small flood 2-3 years local splays -10 year flood 10 years 1.2-2x m.a.fl. -50 year flood 50 years 2x 10 yr fl.
vertebrates
animals with backbones. In the ocean, the vertebrates (animals with backbones), began to thrive—primarily the ancestors of modern fish. An important derived characteristic of these early vertebrates was jaws, which enabled them to grab, pry, or bite off a chunk of flesh.
silicates
any one of numerous minerals that have the silicon-oxygen tetrahedron as their basic structure
Passive continental margins
are geologically inactive regions located a great distance from the closest plate boundary. As a result, they are not associated with strong earthquakes or volcanic activity. Passive continental margins develop when continental blocks rift apart and are separated by continued seafloor spreading.
active continental margins
are located along convergent plate boundaries where oceanic lithosphere is being subducted beneath the leading edge of a continent. Active continental margins are characterized by having a narrow continental shelf, a steep continental slope, and a deep ocean trench just offshore. Deep-ocean trenches are the major topographic expression at convergent plate boundaries. These deep, narrow furrows surround most of the Pacific Rim.
Time and Space Scales
are spatial scales
river floodplain
area of flat land adjacent to river. Full of nutrients for farming.
Two Principal Divisions of Earth's Surface: 1) Ocean Basins
area of the sea floor consisting of mountain ranges, ocean ridges , deep valleys, trenches, and wide plains, abyssal plains
subtropical highs
at equator, high surface pressure resulting from air convergence, cool air sinks and warms to cause clear skies and major deserts. . These pressure systems are characterized by subsiding air currents. When air sinks, it is compressed and warmed. Such conditions are just the opposite of what is needed to produce clouds and precipitation. Consequently, these regions are known for their clear skies, sunshine, and dryness
pillow basalts
basaltic lava that solidifies in an underwater environment and develops a structure that resembles a pile of pillows
Chemical Weathering
breaking down rocks by chemical processes: •Illustrate with chemical weathering of feldspar •Most common mineral in crust •Important in granites-so typical of crustal composition •So understanding chemical weathering of feldspar important to understanding chemical weathering in general
Mechanical Weathering
breaking down rocks with physical force
Flood Control: flood-control dams
built to store floodwater and then let it out slowly. This action lowers the flood crest by spreading it out over a longer time span
Types of Metamorphism
burial, contact(igneous intruding), regional, dynamic or caraclastic(localized)
dripstone
calcium carbonate deposited by water droplets
calcite
calcium carbonate one of the most common carbonate minerals
dolomite
calcium/magnesium carbonate one of the most common carbonate minerals
Biological activity
caused by plants, animals, or humans
Contact Metamorphism
changes in rock caused by the heat from a nearby magma body
Dry-Region Weathering
chemical weathering processes are not as prominent in dry regions as in humid regions. In humid regions, relatively well-developed soils support an almost continuous cover of vegetation. Here the slopes and rock edges are rounded. Such a landscape reflects the strong influence of chemical weathering in a humid climate. By contrast, much of the weathered debris in deserts consists of unaltered rock and mineral fragments—the result of mechanical weathering processes. In dry lands rock weathering of any type is greatly reduced because of the lack of moisture and the scarcity of organic acids from decaying plants. Chemical weathering, however, is not completely lacking in deserts. Over long spans of time, clays and thin soils do form, and many iron-bearing silicate minerals oxidize, producing the rust-colored stain that tints some desert landscapes.
B horizon (subsoil)
clay transported from above
Sheet Silicates
clays
When minerals break evenly in more than one direction...
cleavage is described by the number of cleavage directions and the angle(s) at which they meet
Orographic lifting
cloud formation that occurs when warm moist air is forced to rise up the side of a mountain
cumulus
clouds that look like fluffy, rounded piles of cotton
vascular system
collection of specialized tissues in some plants that transports mineral nutrients up from the roots and brings sugars down from the leaves
bars
common term for sand and gravel deposits in a stream channel
Chemical Sedimentary Rocks: Siliceous oozes
composed of skeletons of diatoms and radiolarians
Chemical Sedimentary Rocks: Sulfides
compounds that consist of one or more elements combined with sulfur
continental characteristics
consists of many rock types. Although the upper crust has an average composition of a granitic rock called granodiorite, its composition and structure vary considerably from place to place.
Drainage Types
consquent, subsequent, antecedent, and superposed
Dark silicate minerals
contain ions of iron and/or magnesium in their structure. Because of their iron content, these silicates are dark in color and have a greater specific gravity than the light silicates.
plagioclase feldspar
contains both sodium and calcium ions that freely substitute for one another
Oceanographers studying the topography of the ocean floor recognize three major units:
continental margins, the deep-ocean basin, and the oceanic (mid-ocean) ridge.
Within these water-deficient regions, two climatic types are commonly recognized:
desert, or arid, and steppe, or semiarid. The two categories have many features in common; their differences are primarily a matter of degree. The steppe is a marginal and more humid variant of the desert and represents a transition zone that surrounds the desert and separates it from bordering humid climates. Maps showing the distribution of desert and steppe regions reveal that dry lands are concentrated in the subtropics and in the middle latitudes
Glacial Landforms
develop because of erosion and a glacier's great weight; different types of glaciers erode differently
Scientific Inquiry
different procedures used to make observations and create explanations
Sea and land breezes
differential solar heating is due to different heat capacities of land and water
flood discharge
discharge of the stream at the point where water overflows the channel banks
fault creep
displacement along a fault that is so slow and gradual that little seismic activity occurs
Energy Sources that power Earth: The Sun
drives external processes that occur in the atmosphere, in the hydrosphere , and at the earth's surface → drives weather + climate, ocean circulation, and erosional processes
Barchanoid Dunes
dunes forming scalloped rows of sand oriented at right angles to the wind. This form is intermediate between isolated barchans and extensive waves of transverse dunes
Meta-Igneous Rocks: Serpentine
green, glassy mineral-found in metamorphosed sea floor basalts
Flood Control: Artificial Levees
earthen mounds built on the banks of a river to increase the volume of water the channel can hold
intraplate earthquakes
earthquakes that occur away from plate boundaries
E horizon
eluviation and leaching
recessional end moraine
end moraines that form as the ice front occasionally stabilizes during retreat
Energy Cycles
energy can't be recycled endlessly because of laws of thermodynamics
Turbidity currents
episodic downslope movements of dense, sediment-laden water. They are created when rock debris, sand, and mud on the continental shelf and slope are dislodged and form a slurry. The mud-thickened mass is denser than seawater and moves downslope, eroding and accumulating more sediment as it goes, similar to a flash flood in stream channels on land. The erosional work repeatedly carried on by these muddy torrents is the major force in the excavation of most submarine canyons.
Long-Range Forecasts
estimates of the likelihood that an earthquake of a certain magnitude will occur in a given place on a time scale of 30 to 100 years or more. Although long-range forecasts are not as informative as we might like, these data provide important guides for building codes so that buildings, dams, and roadways are constructed to withstand expected levels of ground shaking. Most long-range forecasting strategies are based on the observation that large faults often break in a cyclical manner, producing similar quakes at roughly similar intervals.
mass extinction
event in which many types of living things become extinct at the same time
precursors
events or changes that precede an earthquake and thus might provide a warning
Physical Geology
examination of materials composing Earth and seeks to understand the many processes that operate beneath and upon its surface → the study of physical geology logically precedes the study of Earth history bc we must first understand how Earth works before we attempt to unravel its past
California's Death Valley
exhibit evidence of extensive subsidence. In addition to these vertical displacements, offsets in fences, roads, and other structures indicate that horizontal movements between blocks of Earth's crust are also common
rectangular pattern
exhibits many right-angle bends. This pattern develops when the bedrock is crisscrossed by a series of joints and/or faults. Because these structures are eroded more easily than unbroken rock, their geometric pattern guides the directions of valleys.
Pahoehoe
fast-moving, hot lava that has low viscosity
siltstone
fine-grained sedimentary rock generally composed of very small quartz grains
tidal flats
flat, marshy, sandy or muddy areas exposed at low tide and under water at high tide
guyots
flattened seamounts caused by erosion from waves and currents
Earthflow
flow of soil full of clay and water breaking off and moving down slope
amniotic eggs
fluid-filled, have waterproof shells, and enclose the developing embryo
plunging folds
folds in which the hinge lines are not horizontal
focus
for an earthquake, the location within Earth where slippage begins
differential stress
forces that are unequal in different directions
the shore is divided into the........
foreshore and the backshore
slot canyons
form when vertical uplift of the surrounding terrain is so fast that mass wasting can't remove the walls fast enough to keep up
Collision-coalescence process
formation of precipitation, where tiny droplets accumulate, fall, and collide with other small droplets until rain drops form and fall.
Sedimentary Structures: cross bedding
formed as inclined layers of sediment are deposited across a horizontal surface
delta
forms where a sediment-laden stream enters the relatively still waters of a lake, an inland sea, or the ocean. As the stream's forward motion slows, sediments are deposited by the dying current. As the delta grows outward, the stream's gradient continually lessens. This circumstance eventually causes the channel to become choked with sediment deposited from the slowing water. As a consequence, the river seeks a shorter, higher-gradient route to base level •Form at base level •Streams lose identity and drop load •Delta in plan view like Greek letter Δ •In cross section -Topset (coarsest) -Foreset (next finest) -Bottomset (finest) •Delta has distributaries -Move around and try to maintain longitudinal profile as deposition occurs
Mineral Strength: Fracture
fracture = Any break or rupture in rock along which no appreciable movement has taken place. → When minerals fracture, most produce uneven surfaces and are described as exhibiting irregular fracture → some minerals, including quartz, sometimes break into smooth, curved surfaces resembling broken glass. Such breaks are called conchoidal fractures → other minerals exhibit fractures that produce splinters or fibers referred to as splintery fracture and fibrous fracture, respectively
Frost Wedging
freezing and thawing of water within the cracks
Wave Characteristics
frequency, amplitude, wavelength, speed, energy
Metamorphic Facies
groupings of metamorphic rocks of various mineral compositions formed under different grades of metamorphism from different parent rocks: • Metamorphic facies are used to indicate a given T and P of formation for a rock • Grades indicates levels of metamorphism -Index minerals are used to identify grades • Applies to regionally metamorphosed rocks -Example of low grade facies-zeolites Example of high grade facies-amphiboles
Two other nonsilicate minerals frequently found in sedimentary rocks:
halite and gypsum
Vertical stratification:
halocline and thermocline
Manganese Nodules
hard lumps of manganese and other metals that precipitate around a smaller object
Mineralogists use what terms to describe mineral strength and how minerals break when stress is applied?
hardness, cleavage, fracture, and tenacity
Ocean crust characteristics
has a density of about 3.0 g/cm³ and is composed of the dark igneous rocks basalt and gabbro
Tower Karst Landscapes
have isolated, steep-sided hills
optical properties of minerals: Luster - submetallic luster
have similar luster to metal, but are duller and less reflective
Formation of desert pavement
hey form through the gradual removal of sand, dust and other fine-grained material by the wind and intermittent rain, leaving the larger fragments behind.
high grade metamorphism
high temperatures and high pressures
dunes
hills of sand formed by the wind
well
hole drilled into the zone of saturation. Wells serve as small reservoirs into which groundwater migrates and from which it can be pumped to the surface.
sea ice
ice formed by the freezing of the surface of the sea
laccoliths
igneous intrusion that has been injected between two layers of sedimentary rock.
aquitards
impermeable layers such as clay that hinder or prevent water movement
ephemeral streams
in arid climates, many streams carry water only occasionally, after a heavy rainstorm
Seven Systems of Crystal Symmetry (Rene Hauy)
in increasing symmetry: • Triclinic • Monoclinic • Orthorhombic • Trigonal • Hexagonal • Tetragonal • Isometric
Nonconformity
in which younger sedimentary strata overlie older metamorphic or intrusive igneous rocks Just as angular unconformities and some disconformities imply crustal movements, so too do nonconformities. Intrusive igneous masses and metamorphic rocks originate far below the surface. Thus, for a nonconformity to develop, there must be a period of uplift and erosion of overlying rocks. Once exposed at the surface, the igneous or metamorphic rocks are subjected to weathering and erosion and then undergo subsidence and renewed sedimentation.
agents of metamorphism
include heat, confining pressure, differential stress, and chemically active fluids
Framework silicates
includes Quartz and Feldspars
Seismic waves do not travel along straight paths
instead, they are reflected, refracted, and diffracted as they pass through our planet. They reflect off boundaries between different layers, they refract (change direction) when passing from one layer to another layer, and they diffract (follow a curved path) around some obstacles they encounter.
drainage patterns
interconnected networks of streams that form a variety of patterns
Flood Control: Channelization
involves altering a stream channel in order to speed the flow of water and prevent it from reaching flood height. This may simply involve clearing a channel of obstructions or dredging a channel to make it wider and deeper
The formation of petrified wood
involves permineralization with silica, often from a volcanic source such as a surrounding layer of volcanic ash. The wood is gradually transformed into chert, sometimes with colorful bands from impurities such as iron or carbon
The Kaibab Limestone in the Grand Canyon
is an example of a biochemical sedimentary rock. Such biochemical sedimentary rocks can be recognized by:
Oolitic limestone
is formed into small pearl-like spheres, constructed as concentric layers. This is a chemical rock, precipitated from warm, supersaturated marine water.
Principle of Inclusions
is logical and straightforward: The rock mass adjacent to the one containing the inclusions must have been there first in order to provide the rock fragments. Therefore, the rock mass that contains inclusions is the younger of the two. For example, when magma intrudes into surrounding rock, blocks of the surrounding rock may become dislodged and incorporated into the magma. If these pieces do not melt, they remain as inclusions, known as xenoliths. In another example, when sediment is deposited atop a weathered mass of bedrock, pieces of the weathered rock become incorporated into the younger sedimentary layer
Alleghanian Orogeny
is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains.
inselbergs
isolated, steep-sided erosional remnants that rise above desert plains
Roche moutonnee
known as sheep rocks, this glacier feature is formed when glacial ice advances over outcrops of bedrock. The side facing the glacier may be polished and smooth, but the downward side is left steep and jagged due to glacial plucking action.
temporary base level
lakes, resistant layers of rock, and main streams that act as base level for their tributaries
backshore
landward of the high-tide shoreline. It is usually dry, affected by waves only during storms
Pyroclastics-volcanic bomb
large almond or teardrop shaped pieces of ejecta formed when lava solidifies
Uplift of batholith
large bodies of intrusive igneous rock . Formed when magma cools and crystallizes beneath Earth's surface, batholiths are the largest type of pluton
Polymerization
large compounds are built by joining smaller ones together
Plinian: explosive eruption
large gas clouds into stratosphere
kettles
large holes left from the melting of huge chunks of glacial ice lodged in till or outwash
continental ice sheets
large ice sheet covering a portion of a continental area
Supercontinents
large landmasses that contain all, or nearly all, the existing continents. Pangaea was the most recent, but certainly not the only, supercontinent to exist in the geologic past. The earliest well-documented supercontinent, Rodinia, formed during the Proterozoic eon, about 1.1 billion years ago
Exfoliation Domes
large, dome-shaped structure from sheeting
incised meanders
meandering channels that flow in steep, narrow, valleys. How do these features form? Originally the meanders probably developed on the floodplain of a stream that was in balance with its base level. Then, a change in base level caused the stream to begin downcutting. Such a change can be caused either by a drop in a downstream base level or by uplift of the land on which the river is flowing. For example, regional uplifting of the Colorado Plateau in the southwestern United States generated incised meanders on several rivers. As the plateau gradually rose, meandering rivers began downcutting because of their steepening gradient.
Satellite Altimetry
measures the sea surface height from orbit using radar pulses
metasedimentary rocks: gneiss
medium to coarse-grained banded metamorphic rocks in which granular and elongated minerals dominate.
metasedimentary rocks: schist
medium- to coarse-grained metamorphic rocks having a foliated texture, in which platy minerals dominate
decompression melting
melting that occurs as rock ascends due to a drop in confining pressure
Air pressure measurement
mercury barometer and aneroid barometer
Nonsilicates
mineral groups that lack silicas in their structures and account for less than 10% of the earth crust
A horizon
mineral matter and humus
Soil
mineral, organic material, water, air, regolith
immature soils
missing horizons
continental volcanic arc
mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent
jointing
natural cracks that form in rocks due to removal of overburden or due to cooling
Natural Hazards
natural events in the physical environment that are destructive, such as volcanoes and hurricanes
Belt of soil moisture
near surface zone where water is held in place by molecular attraction as a film on soil particles
anions
negatively charged ions
doldrums and horse latitudes
no wind blows because air is rising or sinking
Meta-Igneous Rocks: Amphibolite
nonfoliated metamorphic rock; metamorphism of mafic rocks (basalt and gabbro) can't produce quartz and muscovite when metamorphosed, for these rocks don't contain the right mix of chemicals to yield such minerals. They transform into this dark-colored rock containing hornblende and plagioclase.
hermit shale
nonresistant unit that is composed of slope-forming reddish brown siltstone, mudstone, and very fine-grained sandstone
How did scientists know igneous rocks were cooled from magma?
observations - inferred from intergrown crystals in thin sections →thin section= magnified Field relationships also indicate cooling from magma
Differential weathering
occurs at different rates due to different compositions or resistance of the rock (ex: new mexico's bisti badlands)
plucking
occurs when meltwater penetrates the cracks and joints along the rock floor of the glacier and freezes. Because water expands when it freezes, it exerts tremendous leverage that pries the rock loose. In this manner, sediment of all sizes becomes part of the glacier's load.
Three types of convergent plate boundaries
oceanic-continental, oceanic-oceanic, continental-continental
Cretaceous
of, relating to, or denoting the last period of the Mesozoic era, between the Jurassic and Tertiary periods.
flash floods
often occur with little warning and are potentially deadly because they produce rapid rises in water levels and can have devastating flow velocities
bedrock channel
one in which the stream is actively cutting into solid rock. typically form in the headwaters of river systems where streams have steep slopes. The energetic flow tends to transport coarse particles that actively abrade the bedrock channel. Potholes are often visible evidence of the erosional forces at work.
eukaryotes
organisms made up of one or more cells that have a nucleus and membrane-bound organelles
C horizon
partially altered parent material
Two types of continental margin have been identified:
passive and active
Pyroclastics-Lapilli
pebble like bits of magma that cool in the air
Milankovitch cycles
periodic changes in Earth's rotation and orbit around the sun
plastic deformation of the ice
permanent deformation caused by strain when stress exceeds a certain value
Permafrost
permanently frozen ground
hot spots
places where molten material from the mantle reaches the lithosphere
How Glaciers Erode
plucking and abrasion
The nature of subsurface materials strongly influences the rate of groundwater movement and the amount of groundwater that can be stored. Two factors are especially important:
porosity and permeability
ions
positively and negatively charged atoms → The atom that loses electrons becomes a positive ion, and the atom that gains electrons becomes a negative ion.
cations
positively charged ions
artesian system
refers to a situation in which groundwater rises in a well above the level where it was initially encountered. For such a situation to occur, two conditions must exist: (1) Water must be confined to an aquifer that is inclined so that one end is exposed at the surface, where it can receive water; and (2) aquitards both above and below the aquifer must be present to prevent the water from escaping
Metamorphic Foliation
refers to the repetitions of planar surfaces or layers in a metamorphic rock. Can give a metamorphic rock a striped or streaked appearance in an outcrop, and/or give them the ability to split into thin sheets
Horst and graben
regions that lie between normal faults and are either higher or lower than the area beyond the faults
Principal Shells (energy levels)
regions where individual electrons move around the nucleus, hold specific number of electrons
the Morrison Formation
regression of Sundance Sea due to Nevadan Orogeny shallow water; sea disappearing 70 species of dinosaurs terrestrial deposits flood plain environment layers of dinosaur fossils biggest ever vegetation plentiful good environment to live riverbed deposits. Included are the fossilized bones of massive dinosaurs such as Apatosaurus, Brachiosaurus, and Stegosaurus.
Mississippian (0.33 Ga)
relating to or denoting the early part of the Carboniferous period in North America from about 363 to 323 million years ago, following the Devonian and preceding the Pennsylvanian.
berms
relatively flat platforms often composed of sand that are adjacent to coastal dunes or cliffs and marked by a change in slope at the seaward edge
Two Principal Divisions of Earth's Surface: 2) Continents
remarkably flat features that have the appearance of plateaus protruding above sea level
Leaching
removal of dissolved materials from soil by water moving downwards
leaching
removal of dissolved materials from soil by water moving downwards
Internal structure of atoms example
repeating pattern of lead sulfate →repeating pattern leads to external symmetry
metasedimentary rocks: phyllite
represents a degree of metamorphism between slate and schist. Its constituent platy minerals, mainly muscovite and chlorite, are larger than those in slate but not large enough to be readily identifiable with the unaided eye
unconformity
represents a long period during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed. In each case, uplift and erosion are followed by subsidence and renewed sedimentation. Unconformities are important features because they represent significant geologic events in Earth history. There are three basic types of unconformities, and their recognition helps geologists identify what intervals of time are not represented by strata and thus are missing from the geologic record.
Potassium felspar
rich in potassium ions
yardangs
ridges that are sculpted and streamlined by wind abrasion and deflation
Regolith
rock and mineral fragments (from weathering
Toroweap Formation
rock layers of the Grand Canyon deposited during the Permian Period
Weathering
rocks being broken down into smaller pieces
Chemical Sedimentary Rocks
rocks formed from minerals precipitated from a solution or left behind by evaporation • Evaporites • Carbonates • Siliceous oozes • Sulfides • Coal
ventifacts
rocks shaped by wind blown sediments
discordant - dikes
tabular or sheet-like bodies of magma that cut through and across the layering of adjacent rocks. They form when magma rises into an existing fracture, or creates a new crack by forcing its way through existing rock, and then solidifies
sidescan sonar
technique that directs sound waves toward the ocean floor at an angle to map its topographic features
Relative humidity and temperature
temperature increases, RH decreases temperature decreases, RH increases
Seafloor sediments can be classified according to their origin into three broad categories:
terrigenous ("derived from land"), biogenous ("derived from organisms"), and hydrogenous
the world's five main gyres
the North Pacific Gyre, the South Pacific Gyre, the North Atlantic Gyre, the South Atlantic Gyre, and the Indian Ocean Gyre (which exists mostly within the Southern Hemisphere).
pore spaces
the amount of space in the soil that could be filled with air or water. Voids most often are spaces between sedimentary particles; also common are joints, faults, cavities formed by the dissolving of soluble rock such as limestone, and vesicles (voids left by gases escaping from lava).
foreshore
the area exposed when the tide is out (low tide) and submerged when the tide is in (high tide)
cut bank
the area of active erosion on the outside of a meander
shore
the area that extends between the lowest tide level and the highest elevation on land that is affected by storm waves
glacial budget
the balance or lack of balance between accumulation at the upper end of a glacier and loss at the lower end. If ice accumulation exceeds wastage, the glacial front advances until the two factors balance. At this point, the terminus of the glacier becomes stationary.
Wave Refraction
the bending of waves so that they move nearly parallel to the shoreline
hanging wall
the block of rock that lies above an inclined fault or an ore body.
Mohorovicic discontinuity
the boundary between the earth's crust and the upper part of the Asthenosphere; seismic waves change speed at this boundary
Some of the most common nonsilicate minerals belong to one of three classes of minerals:
the carbonates (CO32−), the sulfates (SO42−), and the halides (Cl1−, F1−, Br1−). The
Metamorphism
the change in form that happens in Earth's crustal rocks in response to changes in temperature (T) and pressure (P) **morphing
stream valley
the channel, valley floor, and sloping valley walls of a stream
Late jurassic
the continents had started to split and the Atlantic Ocean was forming
hydrologic cycle
the cycle through which water in the hydrosphere moves; includes such processes as evaporation, precipitation, and surface and groundwater runoff
drawdown
the difference in height between the bottom of a cone of depression and the original height of the water table
slope orientation
the direction a slope is facing
geologic time scale
the division of Earth history into blocks of time--eons, eras, periods, and epochs. The time scale was created using relative dating principles.
mass movement
the downslope movement of rock, regolith, and soil under the direct influence of gravity
Rapid Forms of Mass Movement: slump
the downward slipping of a mass of rock or unconsolidated material moving as a unit along a curved surface
plate boundaries
the edges of tectonic plates.
groups
the elements with similar properties line up in columns
snowline (equilibrium line)
the elevation at which the accumulation and wasting of glacial ice is equal. The elevation of this boundary varies greatly, from sea level in polar regions to altitudes approaching 5000 meters (16,000 feet) near the equator. Above the snowline, in the zone of accumulation, the addition of snow thickens the glacier and promotes movement
headward erosion
the extension upslope of the head of a valley due to erosion
"Stick-slip" behavior in faulting
the fast movement that occurs between two sides of a fault when the two sides of the fault become unstuck. The rock becomes distorted, or bent, but holds its position until the earthquake occurs.
Evidence of fluids: quartz veining
the filling of an already present crack in rocks. The crack might form during folding of the rock in mountain-building processes, by shattering during tectonic events, by a decrease in pressure during the uplift of a rock, or because a rock cools down and shrinks
Pyroclastic flow
the flow of ash, cinders, bombs, and gases down the side of a volcano during an explosive eruption (ex: Mayon Volcano, Philippines)
Ridges and fracture zones
the fracture zone along the ocean bottom where molten mantle material comes to the surface, thus creating new crust. This fracture can be seen beneath the ocean as a line of ridges that form as molten rock reaches the ocean bottom and solidifies.
silicate tetrahedron
the fundamental building block of all silicate minerals, a pyramid-shaped structure of silicon ion bonded to four oxygen ions
continental rise
the gently sloping surface at the base of the continental slope. The continental rise consists of a thick accumulation of sediment that has moved down the continental slope and onto deep-ocean floor. Most of the sediments are delivered to the seafloor by turbidity currents that periodically flow down submarine canyons
geothermal gradient
the gradual increase in temperature with depth in the crust
Exfoliation-Sierra Nevada granites
the granite developed exfoliating joints and began to leak
wavelengths
the horizontal distance between successive crests or successive troughs
Glaciers are part of two important cycles in the Earth system
the hydrologic cycle and the rock cycle
Vine-Matthews-Morley hypothesis
the hypothesis that if seafloor spreading is occuring, then we should symmetric patterns of magnetic reversals in the oceanic crust
metamorphic grade
the intensity of metamorphism that formed the rock
Energy Sources that power Earth: Earth's Interior
the internal processes that produce volcanoes, earthquakes, and mountains are powered by heat remaining from where our planet formed & heat that is continuously generated by radioactive decay
Hadean period of chemical differentiation established the three major divisions of Earth's interior—
the iron-rich core; the thin primitive crust; and Earth's thickest layer, the mantle, located between the core and the crust. In addition, the lightest materials—including water vapor, carbon dioxide, and other gases—escaped to form a primitive atmosphere and, shortly thereafter, the oceans
the daughter products
the isotopes resulting from the decay of the parent
Mantle
the layer of hot, solid material between Earth's crust and core → less dense than the Core
deflation
the lifting and removal of loose material
shoreline
the line that marks the contact between land and sea. Each day, as tides rise and fall, the position of the shoreline migrates. Over longer time spans, the average position of the shoreline gradually shifts as sea level rises or falls.
rock cycle
the loop that involves processes by which one rock changes to another
bathymetry
the measurement of ocean depths and the charting of the shape or topography of the ocean floor
basal sliding
the movement of a glacier that depends on the pull of gravity and on a thin layer of water between glacier and land
sediment transport
the movement of eroded materials from one place to another by water, wind, and/or glaciers.
infiltration
the movement of surface water into rock or soil through cracks and pore spaces
tidal current
the movement of water toward and away from the coast as a result of the rise and fall of the tides
Drifting
the name for all material of glacial origin found anywhere on land or at sea, including sediment and large rocks (glacial erratic). Glacial origin refers to erosion, transportation and deposition by glaciers.
Earth Science
the name for the sciences that collectively seek to understand Earth and its neighbors in space
atomic number
the number of protons in the nucleus of an atom
fracture zones
the ocean floor is diced up by narrow bands of vertical fractures. Lie roughly at right angles to mid-ocean ridges, effectively segmenting the ridges into small pieces.
deep-ocean basin
the part of the ocean floor that is under deep water beyond the continent margin and that is composed of oceanic crust and a thin layer of sediment
epicenter
the point on Earth's surface directly above the hypocenter **One method used for locating an earthquake's epicenter relies on the fact that P waves travel faster than S waves.
striations
the presence of a multitude of fine parallel lines
Rifting
the process by which Earth's crust breaks apart; can occur within continental crust or oceanic crust
Fractional (partial) melting
the process by which different minerals in rock melt at different temperatures
supercontinent cycle
the process by which supercontinents form and break apart over millions of years
sheet erosion
the process by which water flows over a layer of soil and removes the topsoil
electron capture
the process in which an inner orbital electron is captured by the nucleus of the atom that contains the electron
correlation
the process of establishing the equivalence of rocks of similar age in different areas. Correlating the rocks from one place to another makes possible a more comprehensive view of the geologic history of a region. For example, shows the correlation of strata at three sites on the Colorado Plateau in southern Utah and northern Arizona. No single locale exhibits the entire sequence, but correlation reveals a more complete picture of the sedimentary rock record.
radiometric dating
the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products. Radiometric dating is reliable because the rates of decay for many isotopes have been precisely measured and do not vary under the physical conditions that exist in Earth's outer layers. Therefore, each unstable isotope used for dating has been decaying at a fixed rate since the formation of the mineral crystals in which we find it, and the products of its decay have been accumulating in that crystal at a corresponding rate. For example, some minerals are able to incorporate uranium atoms in their crystal lattice. When such a mineral crystallizes from magma, it contains no lead (the stable daughter product) from previous decay. The radiometric "clock" starts at this point. As the uranium in this newly formed mineral decays, atoms of the daughter product accumulate, trapped in the crystal, and eventually build up to measurable levels. Similarly, when a crystal of feldspar forms, some of the potassium atoms incorporated into its lattice will be the unstable isotope potassium-40. These atoms will decay at a steady rate by electron capture to produce the daughter argon-40. Over time, there is less and less of the parent potassium and more and more of the daughter argon.
outgassing
the process of releasing gases from a planetary interior, usually through volcanic eruptions. These eruptions release mainly water vapor, carbon dioxide, and sulfur dioxide, with minor amounts of other gases.
evaporation
the process of turning from liquid into vapor
Photosynthesis
the production of energy-rich molecules of sugar from molecules of carbon dioxide (CO2) and water (H2O), using sunlight as the energy source. The sugars (glucose and other sugars) generated by photosynthesis are used in metabolic processes by living things, and the by-product of photosynthesis is molecular oxygen.
Coconino Sandstone
the prominent white band near the rim of the Grand Canyon - deposited in sand dunes
Pangaea
the proposed supercontinent that 200 million years ago began to break apart and form the present landmasses
Big Bang
the rapid expansion of matter from a state of extremely high density and temperature that according to current cosmological theories marked the origin of the universe
Rapid Forms of Mass Movement: rockslides
the rapid slide of a mass of rock downslope along planes of weakness
seismograms
the record made by a seismograph = it records the arrival times of P, S, and surface waves
Apparent Polar Wander Path
the record of paleomagnetism revealed that the location of Earth's magnetic poles had been changing through geologic time. This 'wandering' meant that Earth's magnetic poles do not move with respect to fixed continents. Rather, continents move relative to each other while the Earth's magnetic poles stay roughly fixed.
habitable zone
the region around a host star where a planet with sufficient atmospheric pressure can maintain liquid water on its surface
Transpiration
the release of water vapor by plants through their leaves
Fossils
the remains or traces of prehistoric life, are important inclusions in sediment and sedimentary rocks. . They are basic and important tools for interpreting the geologic past.
Mylonite
the resulting rock from dynamic metamorphism; has a foliation that parallels the fault.
Lithosphere
the rigid outer layer that includes the crust and the uppermost mantle
Upwelling
the rising of cold water from deeper layers to replace warmer surface water, is a common wind-induced vertical movement. One type of upwelling, called coastal upwelling, is most characteristic along the west coasts of continents, most notably along California, western South America, and West Africa.
Asthenosphere
the rocks under the lithosphere; they are weak and able to slowly flow in response to the uneven distribution of the heat deep within the Earth
oceanography
the scientific study of the oceans. It is an interdisciplinary science that draws on the methods and knowledge of geology, chemistry, physics, and biology to study all aspects of the world ocean.
rock-forming minerals
the set if minerals that make most of the rocks of Earth's crust
Precession of the Equinoxes(when the equinoxes occur during a year)
the slow westward motion of the equinoxes along the ecliptic because of Earth's precession
Nucleus
the small heavy core of an atom that contains all of its all of its positive charge and most of its mass
Geosphere
the solid Earth that lies beneath the atmosphere and the ocean; extends from the surface to the center of the planet
Geologic Time
the span of time since the formation of Earth
Cyclostratigraphy
the study of astronomically forced climate cycles within sedimentary successions
Seismology
the study of earthquake waves
Meteorology
the study of the atmosphere and the processes that produce weather and climate → involves the application of the sciences in the integrated study of the thin layer of air that surrounds Earth
Oceanography
the study of the ocean: integrates chem, physics, geology and bio(e.g. the study of the composition and movements of seawater, as well as costal processes, seafloor topography, and marine life) → involves the application of all sciences in a comphrensive and interrelated study of the oceans in all their aspects + relationships
beach face
the wet sloping surface that extends from the berm to the shoreline
Nebular Theory
theory that proposes that the bodies of our solar system evolved from an enormous rotating cloud called the solar nebula; mostly hydrogen and helium
ice shelves
these are large, relatively flat masses of floating ice that extend seaward from the coast but remain attached to the land along one or more sides. The shelves are thickest on their landward sides, and they become thinner seaward. They are sustained by ice from the adjacent ice sheet and are also nourished by snowfall and the freezing of seawater to their bases. Antarctica's ice shelves extend over approximately 1.4 million square kilometers (600,000 square miles). The Ross and Ronne-Filchner Ice Shelves are the largest; the Ross Ice Shelf covers an area approximately the size of Texas
valence electrons
these electrons can be transferred to or shared with other atoms to form chemical bonds
Far-travelled terranes
these regions are typified by shallow water depth, thick crust, low upper crustal velocities, lack of clear magnetic lineations, and steep margins. They cover about 10% of the present-day ocean floor, with particular concentrations in the western Pacific and the Indian Oceans, as shown in Fig. 1. Typically these regions are well embedded within their plates and show no evidence for relative motions. Such relative motions can occur, however, when the plateaus move into the subduction zones where oceanic plates are consumed.
greenschist facies
this metamorphic facies develops under regional metamorphism with moderate temp and pressures, form low-grade metamorphic rocks such as slate, phyllite
Principle of Superposition
this principle simply states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below. Although it may seem obvious that a rock layer could not be deposited with nothing beneath it for support, it was not until 1669 that Steno clearly stated this principle. This rule also applies to other surface-deposited materials, such as lava flows and beds of ash from volcanic eruptions. Applying the principle of superposition to the beds exposed in the upper portion of the Grand Canyon, we can easily place the layers in their proper order.
Mineral Strength: Hardness
this property is determined by rubbing a mineral of unknown hardness against one of known hardness or vice versa
neap tides
tides with minimum daily tidal range that occur during the first and third quarters of the moon
Geomagnetic Polarity Time Scale
time scale composed of the sequence of paleomagnetic orientations of sediments through time
Pyroclastics-volcanic ash
tiny particles of pulverized volcanic rock and glass
Seafloor Bathymetry
topography of the sea floor; highly variable; three kinds of landscape
mixed tidal pattern
two high and two low waters each day with large inequalities in high water heights, low water heights, or both
Brachiopod
two-shelled creature with two "arms" inside with which to bring in food
graded bedding
type of bedding in which particle sizes become progressively heavier and coarser toward the bottom layers
Important Nonsilicate Minerals
typically divided into groups based on the negatively charged ion or complex ion that the members have in common. For example, the oxides contain negative oxygen ions (O2−), which bond to one or more kinds of positive ions.
Historical Geology
understanding the origin of Earth and the development of the planet through its history → this type of geology strices to establish an orderly chronological arrangement of the multitude of physical biological changes that have occurred in the geological past
Sedimentary Structures: deep sea fans
underwater geological structures associated with large-scale sediment deposition and formed by turbidity currents
ground moraine
unsorted material left beneath a glacier when the ice melts
Gas hydrates
unusually compact chemical structures made of water and natural gas. The most common type of natural gas is methane, which produces methane hydrate. Gas hydrates occur beneath permafrost areas on land and under the ocean floor at depths below 525 meters (1720 feet).
Continental-Continental Convergence
when one landmass moves toward the margin of another because of subduction of the intervening seafloor. Whereas oceanic lithosphere tends to be dense and readily sinks into the mantle, the buoyancy of continental material generally inhibits it from being subducted, at least to any great depth. Consequently, a collision between two converging continental fragments ensues. This process folds and deforms the accumulation of sediments and sedimentary rocks along the continental margins as if they had been placed in a gigantic vise. The result is the formation of a new mountain belt composed of deformed sedimentary and metamorphic rocks that often contain slivers of oceanic lithosphere.
alluvial channel
when the bed and banks are composed mainly of unconsolidated sediment. The major factors affecting the shapes of these channels are the average size of the sediment being transported, the channel gradient, and the discharge. Alluvial channel patterns reflect a stream's ability to transport its load at a uniform rate, while expending the least amount of energy. Thus, the size and type of sediment being carried help determine the nature of the stream channel.
perched water table
where an aquitard creates a local zone of saturation above the main water table
Deep earthquakes occur in subduction zones
where one of the tectonic plates floating on the surface of the Earth dives under another and is "subducted" into the mantle. Within the sinking slabs of crust, earthquakes cluster at some depths and are sparse in others
convergent plate boundary
where two plates move toward each other and the leading edge of one is bent downward as it slides beneath the other = collide
endothermic
which means mammals are capable of maintaining a constant body temperature thorough metabolic activity, and they have large brains for their size compared to other vertebrate groups.
zone of saturation
zone where all open spaces in sediment and rock are completely filled with water
Burial Metamorphism
• Also known as low grade metamorphism • T and P limited to those found due to burial in deep sedimentary basins - Typically T = 100˚C to 200˚C - Depths of about 8 km - Zeolites are formed **heating up+elevated pressures
Minerals' Internal structure
• Based on observations • Steno (1669) law of constancy of interfacial angles: the crystal faces of a given species are constant, whatever the lateral extension of these faces and the origin of the crystal, and are characteristic of that species (e.g. quartz) → External Forms of crystals showed many different types of symmetry
Silicate Tetrahedra (summary)
• Basic building blocks of the rock-forming minerals • Composed of small Si cation and surrounded by 4 O anions • Tetrahedra polymerize into different structures - Isolated, rings, single chains, double chains, sheets, and framework
atomic bonding
• Bonding between atoms depends on exchange and sharing of electrons •Types of bonding: - Ionic - Covalent
Sedimentary Structures: Load Casts
• Bottom of stratum sinks into lower layer • Due to differential compaction • Indicates which way is "up" **compacting in different ways laterally
Origin of Igneous Rocks
• Bowen's Reaction Series (fractional crystallization) • Fractional (partial) melting • Decompression melting
Physical Weathering
• Breaking apart of rocks • Types of physical weathering -Fragmentation -Exfoliation -Spheroidal weathering -Frost wedging • Synergy of chemical and physical weathering • Climate controls which one dominates -Humid, warm climates have relatively more chemical weathering -Cold, dry climates have relatively more physical weathering
Surface waves cause damage
• Buildings crash together • Highway supports collapse • Gas lines ruptured
Eruptions and climate
• Carbon dioxide and sulfur dioxide from eruptions can effect global climate - CO2 causes greenhouse effect - Sulfur dioxide can cool climate • Dust thrown into atmosphere by violent eruption can cool climate
Classification of Igneous Rocks
• Classification based on composition and texture • Composition: - Three types-basaltic, andesitic, and rhyolitic (silica increasing) 1. Basaltic → Olivine, pyroxene, feldspar (no free quartz) 2. Rhyolitic → Free quartz, plagioclase, and biotite 3. Andesitic → Intermediate between rhyolite and basalt → Plagioclases, some pyroxenes, and some free quartz • Texture: → Ranges from fine-grained (aphanitic) to coarse-grained (porphyritic) → Controlled by cooling rate → Cooling rate indicates mode of emplacement (extrusive vs. intrusive)
Classification of Sedimentary Rocks
• Classification based on grain size and composition • Classification tells us something about environment of deposition • Classification also tells us something about source (provenance) of sediment • Two basic types of sedimentary rocks -clastic and chemical
Classification of Magmas
• Classification of magmas will be the same as classification of igneous rocks • Main parameter is silica content: • Lowest silica content (50%) basaltic magma (lowest gas content) • Intermediate silica content (60%) andesitic magma • Highest silica content (70%) rhyolitic magma (highest gas content)
Types of Drainage Networks
•Dendritic -Flat-lying bedrock •Radial -Around a volcano or similar topography •Trellis -Ridges of erosionally resistant bedrock •Rectangular -Due to regular joint pattern in rock
Clastic Sedimentary Rocks
• Composed of fragments (clasts) of eroded rocks • Classification - texture (grain size) • Texture - environment of deposition - distance transported • Clastic rocks (in order of decreasing grain size): - Conglomerate - Sandstone - Siltstone - Shale **mixture of grain sizes
Textures of Sedimentary Rocks: Examples
• Conglomerate-poorly sorted • Breccia-angular grains • Poorly sorted cobble-pebble gravel • Well-sorted and well-rounded pebble gravel-Columbia River • Well-sorted, well-rounded sandstone-St. Peters SS. • Poorly sorted till-western Washington
Magma
• Definition: - High temperature, molten rock material with a range of compositions but silica always present • Composition: - elemental composition reflects common crustal elements (Si, O, Fe, Al, Mg, Ca, Na) - Gasses-mainly CO2 and H2O - SiO2 content important to classification and volcanic eruptive style - Viscosity depends on silica content - Temperature: 1000˚C to 1200˚C
Classification of Rocks
• Depends on their properties -Texture (fine or coarse grained) -Color (light or dark) -Mineral content -How they were formed (origin) •Most basic, fundamental classification depends on how they were formed -Igneous -Sedimentary -Metamorphic •Further subdivisions based on: -Texture -Minerals •Both tell us something about conditions of rock formation (temperature and pressure)
Plate Tectonics
• Earth's surface is divided into rigid plates that move with respect to each other - Plates are lithosphere-100 km thick - Spherical caps • Three types of plate boundaries -Divergent -Convergent -Transform • Relative motions typically 5-10 cm/year
Silicate Minerals
• Every silicate mineral contains oxygen and silicon atoms • Except for a few silicate minerals such as quartz, most silicate minerals also contain one or more additional elements in their crystalline structure. These elements give rise to the great variety of silicate minerals and their varied properties.
Igneous Rocks
• Formed by volcanic processes • Impact on atmosphere, biosphere, climate • Give information about geosphere processes • Definition of igneous rocks: - Rock cooled from a magma - Formed of intergrown crystals
Sedimentary Structures: ripple marks
• Formed in shallow water due to currents • Indicates direction of currents
Textures of Clastic Rocks
• Grain size- - velocity of water in environment of deposition = ctrls grain size • Stoke's Law: -w=[((ps-r)g)/18m]d^2 -where: ps sediment density r fluid density g acceleration due to gravity d diameter of grain m viscosity of fluid w settling velocity **need fast moving water for big grains **big grains settle faster than little grains **still water for little grains to settle
metasedimentary rocks
• In regional metamorphism have typical sequence with increasing T and P -Slate -Phyllite -Schist -Gneiss • These rocks typically have a foliation • Marble and quartzite are non-foliated metasedimentary rocks(no minerals in it)
Cations in Silicates
• In silicates cations fit into the interstices between tetrahedra or polymerized tetrahedra • Typical cations: -K+, Ca++, Mg++, Fe++, Fe+++ • These cations are bonded into the structure by their charge---Si tetrahedra have a 4- charge
Metamorphic Rocks
• Increased T and P cause new mineral assemblages to form - chemical composition important controlling factor - length of time of elevated T and P important, as is the direction of T and P change (increasing vs. decreasing) • Fluids important in mediating reactions - dissolve and transports ions - presence speeds up metamorphic reactions • Differential stress causes characteristic texture - foliation •Metamorphic rocks are classified by: - their mineralogy and texture • Plate tectonics helps us understand tectonic environment for metamorphism
Stilbite-a zeolite mineral
• Indicator of low grade metamorphism • Framework silicate with holes in crystal structure • Used for filtering, water softeners, odor removal, etc. **didn't see elevated pressures and that's why holes
Scientific Method steps
• Make observations • Formulate hypothesis • Test hypothesis with more observations • Accept, modify, or reject hypothesis • Etc. (iterative process)
Stability to Chemical Weathering
• Minerals formed at T and P conditions much different than surface T and P will be chemically unstable at Earth's surface -Hence more susceptible to chemical weathering • stability comes from Bowen's Reaction series -Olivine (crystallizes at high T)-less stable -Quartz (crystallizes at lower T)-more stable
Mineral Chemical Composition
• Native elements (Ag, Au, Cu) • Sulfides (FeS2, CuS) • Halides (NaCl) • Oxides and hydroxides (H20) • Carbonates (CaCO3) • Sulfates (BaSO4) • Phosphates (Ca5(PO4)3(F,Cl,OH) • Silicates (SiO2)
Cataclastic (Dynamic) Metamorphism
• Occurs when rocks deformed in fault zones • Causes shearing and breaking of rocks -Fault breccia (shallow crustal) > sharp edges+angles -Mylonites (deep crustal, ductile deformation) > exposed to high temps+pressures **elevated temps+pressures
basic "rules" of plate tectonics
• Oceanic lithosphere is denser than the continental lithosphere • The crust is divided into different plates and there are 3 types of boundaries at these plates: divergent = two plates move away from each other, convergent = Two plates move towards each other, transform= two plates grind past each other • The three types of boundaries go into the rule that the plates only move if they are pushed not pulled. The three types of boundaries are the different types of ways the plates are moved or pushed.
Most Abundant Elements in the Earth's Crust
• Oxygen (45%) • Silicon (27%) • Aluminum (8%) • Iron (6%) • Calcium (5%) • Magnesium (3%) • Sodium (2%) • Potassium (2%) • All others (2%)
Applications of Paleomagnetic Data
• Paleogeographic Reconstructions (Apparent Polar Wander Path) • reversals of the geomagnetic field • Magnetostratigraphy
Waves in shallow water
•Depth<wave base •Waves slow down in shallow water ("feel bottom") •Water piles up-wave height increases •Breaker zone occurs at a depth of 1.3 x wave height (becomes wave of translation) •Swash and backwash on beach •Build-up of water between breaker zone and beach leads to rip tides and undertow
Sedimentary Structures
• Sed. structures indicate depositional processes • Examples of Sedimentary Structure: • Cross-bedding - Ripples in streams or sand dunes - Indicates direction of fluid flow - Also used to tell geologists which way is "up" (fold + tilted) - Larger cross beds indicate eolian deposition(deposited from air) **fluid is usually air or water
Textures of Sedimentary Rocks
• Sorting - grains different or same sizes - indicates distance to source area = tell you abou the environmental deposition (finer = further and more sorted & bigger =closer) • Angularity of clasts - roundedness of clasts - indicates distance to source area = further = rounded =closer = sharper
Meta-Igneous Rocks
• Start with seafloor (basalt) and metamorphose it-get different sequence -Greenschist > Chlorite and epidote -Amphibolite > Chlorite changes to amphibole -Granulite > Amphibole changes to pyroxene -(Bowen's Reaction series in reverse) -No foliation because no sheet silicates
Seafloor Magnetic "Stripes"
• Stripes of normal polarity and reversed polarity alternate across the ocean bottom. • Stripes form mirror images on either side of the mid-ocean ridges • Stripes end abruptly at the edges of continents, sometimes at a deep sea trench
Units of Energy
• Watt is a unit of power -1 horsepower = 746 watts -1 human power? (about 100 watts.... • Power=work/time • Work=force x distance • Units of work? -Joule (work needed to raise the temperature of one gram of water by 1˚C)
External symmetry to crystals
• Why? • First piece of evidence came from x-ray diffraction-evidence of internal order • Order at the atomic level-atoms order themselves in 3D
sediment production
• Zone where most sediment is derived • Located in the headwater region of a river system • Sediment generated by - Bedrock broken into smaller pieces - Bank erosion - Scouring of the channel bed **Much of the sediment carried by streams begins as bedrock that is subsequently broken down by weathering and then transported downslope by mass wasting and overland flow. Bank erosion can also contribute significant amounts of sediment. In addition, scouring of the channel bed deepens the channel and adds to the stream's sediment load.
Plate tectonic framework for igneous rocks
• volcanism forming sea floor • seafloor sinks back into mantle of earth • heats as the seafloor goes back down to earth(lithosphere)
Sedimentary Rocks
• ~ 5% of Earth's crust • Continuous record of Earth history • Where biosphere, hydrosphere, atmosphere, and geosphere all interact • Formed by weathering, transport, and either deposition of detrital particles or precipitation chemically
Mid-Latitude Cyclone
•Affects our weather •Moves from west to east across continent •Life Cycle -Front between cP and mT air masses -Establishes a low pressure (cyclone) with warm and cold fronts extending outwards -Cold front overtakes warm front -Occluded front forms and storm then dissipates
Air Pressure
•Air pressure=weight of column of air in the atmosphere •At sea level air pressure is 760 mm of mercury -Use mercury-why not a more common fluid like water? -Air pressure decreases with altitude -The decrease with altitude is not linear
flood control
•Artificial levees -Channel built up-no deposition on floodplain -Need to keep moving levee higher •Flood control dams -Sedimentation over time reduces effectiveness •Channelization -Increase gradient to increase velocity -River still wants to meander •Nonstructural approach -Minimize development in flood prone areas
Frequency and energy of earthquakes
•As size of earthquake increases, there is a decrease in their frequency •As Richter magnitude increases, nonlinear increase in energy released
Global Atmospheric Circulation
•Atmosphere moves to transfer heat by convection •Heat transfer from equator to poles also affected by Coriolis force •Basic pattern -Hadley Cell •Winds flow toward equatorial low (Intertropical Convergence Zone) •Air sinks down at 30˚N and S-highs occur here and have dry air and deserts •As surface air moves toward equator deflected to move east to west-Trade Winds •Air descending at subtropical highs (30˚N and S) also flows north-leads to mid-latitude cell (Ferrell Cell) •Ferrell Cell -Mid-latitude -Air moves from subtropical high to polar front (where jet stream is) -As wind moves toward the poles it is deflected from west to east (Prevailing Westerlies) •Polar Cell -Cold, heavy air sinks from the poles toward the Ferrell cell and the polar front -These are called the Polar Easterlies
Energy and the Atmosphere
•Atmosphere receives energy from the Sun •Temperature vs. Energy >T is the average kinetic energy of atoms >Heat is the total amount of energy •Heat transfer >Radiation, convection, conduction •Solar insolation >Energy that reaches Earth's surface >Less than that coming from Sun >Radiation is electromagnetic >Reflected by clouds, absorbed by gasses >Scattering causes blue sky •Albedo >surfaces reflecting solar energy >High albedo reflects more solar energy
Factors affecting the Earth's Climate System
•Atmospheric composition •Industrial pollutants •Volcanic gasses (water, carbon dioxide, sulfuric acid) •Aerosols •Incoming solar radiation •Clouds •Orbital changes •Oceans •Sea surface temperature (affects evaporation) •Extent of ocean (plate tectonics) •Continent-ocean distribution (plate tectonics) •Heat exchange with atmosphere •Salinity of ocean water •Continents •Distribution affects ocean currents •Orographic affects winds •Albedo
Elastic Rebound Theory
•Based on study of 1906 San Francisco earthquake by Reid •Major points: •Strain slowly builds up across fault •Stress released when potential energy overcomes static friction •Stress is released by slip on fault •Rapid release of elastic energy (seismic waves)
deserts
•Different causes and types of deserts •Subtropical (20˚-30˚N and S latitude) •Continental (deep in continental interiors) •Rainshadow (lee side of mountain ranges) •Coastal (cold upwelling seawater) •Polar (cold, dry air descends) •Deserts don't always have sand •Subtropical deserts caused by global wind circulation -They are the largest, globally
Rock Deformation: Faulting (brittle behavior)
•Dip-slip faulting -Normal -Reverse -Thrust •Strike-slip faulting -Right lateral -Left lateral •Evidence of past faulting (slickensides) •Jointing (brittle) -Joint sets
Formation of Clouds
•Basic Concepts •Adiabatic heating and cooling >no heat added or removed from the system >due to expansion or contraction of a gas •Convection in the atmosphere >Warm air less dense - rises (and expands) >Cold air more dense - sinks (and contracts) •Adiabatic lapse rate •Dry adiabatic lapse rate (for unsaturated air) >Air rises therefore cools adiabatically (1˚C/100m) >Air sinks, therefore heats adiabatically •Moist adiabatic lapse rate (for saturated air) >Air rises, cools adiabatically >But condensation releases latent heat of condensation >MALR=0.6˚C/100m •Air is lifted (by some process) •It expands and cools adiabatically •Relative humidity increases •Humidity increases until air saturated and condensation occurs -Water droplets nucleate on aerosols -Water droplets grow by collisions -When large enough they fall as precipitation
Precipitation formation
•Bergeron process -Rain droplets start as ice particles -Supercooled water droplets freeze easily onto frozen nuclei •Collision-Coalescence process -Warm clouds-need aerosol or other nuclei -Collide with other drops to coalesce
floodplain
•Built up over time by meandering river •Broad river valleys that will periodically be covered by flood waters •Natural levees are built up along the banks of the river channel during the periodic flooding •Yazoo streams flow parallel to main channel because of natural levees
Atmospheric structure
•By air pressure -Atmosphere is 1000 mbars at sea level -90% of atmosphere below 16 km (10 miles) •By temperature •Troposphere (0-16 km) •T decreases with elevation 20˚C to -60˚C •Heated by Earth's surface (greenhouse effect) •Stratosphere (16-50 km) •T increases with elevation •Ozone absorbs UV radiation •Mesosphere (50-80 km) •T decreases with elevation •Thermosphere (80-500 km) •T increases due to absorption of radiation and solar wind
Chemical weathering of feldspar
•CO2 in atmosphere dissolves in rainwater •Makes weak acid, carbonic acid -H2O + CO2 = H2CO3 = H+ + (HCO3)- •Chemical reaction: -K Feldspar + carbonic acid + water = kaolinite + dissolved SiO2 + dissolved K + dissolved bicarbonate •So carbonic acid causes feldspar to be converted to clay and dissolved silica, K, and bicarbonate
Climate Models
•Called GCMs-general circulation models •3D models of global climate-attempt to link processes in atmosphere, hydrosphere, and biosphere •Need boundary conditions for the modeling -Solar radiation reaching Earth -Distribution of oceans and continents -Concentration of atmospheric greenhouse gasses -Sea surface temperature, etc. •CO2 is projected to double by 2100 •It if does, GCMs suggest global temperature increases of 1.5˚C to 4.5˚C •But temperature increases will not be evenly distributed over globe •Greater increases at higher latitudes, where polar ice sheets exist
Chemical weathering of carbonates
•Carbonates another important crustal rock •Chemical weathering of carbonates very important in humid climates •Carbonic acid important -Calcite (CaCO3) + carbonic acid = dissolved Ca++ + bicarbonate ion •So no residue in this reaction, rock is all dissolved
El Nino - teleconnections
•Causes changes in weather all over world •Drought in eastern Pacific -Also no upwelling, so no anchovies, no fish, no birds... -Greater than normal rain in western SA •Sub-tropical jet stream shifted south -decreases Atlantic hurricane activity -Increased rain in SE US •Sub-polar jet stream shifted north -Warmer winter west of Rockies
Budget (Mass Balance) of a Glacier
•Changes in the budget of glacier is why it advances or retreats •Zone of accumulation •Zone of ablation •When net accumulation > net ablation=advance •When net accumulation< net ablation=retreats •Snowline is the boundary between zones of accumulation and ablation
Moisture in the Atmosphere
•Changes of State •Water occurs in all three states at Earth's surface •Changing from one state to another requires either a loss or gain of energy •Latent heat: the amount of heat lost or gained during a change of state •Latent heats of evaporation and condensation are the same amount of energy=2260 J/gm
stream channels
•Channelized flow downhill •When it rains -First, sheetwash -Then, small rills and gullies -Then, tributaries into trunk stream -Headward erosion as stream channel develops •The gradient of a stream channel is how far it drops in elevation per change in horizontal distance •The longitudinal profile of a stream is its characteristic gradient downstream -Longitudinal profile is concave upwards (gradient decreases downstream) •The base level of a stream is the elevation where stream loses its identity -Lake or ocean
Chemical Sed Rx
•Chert-deep sea siliceous oozes
Features of a Valley Glacier
•Cirque-"headwaters" of glacier •U-shaped valley •Moraines -Medial -Lateral -Terminal
Types of clouds
•Cirrus -Clouds high, white, and thin -Feathery appearance •Cumulus -Globular individual cloud masses -Flat base •Stratus -Layered -No distinct separate clouds
water wells
•Cone of depression •Effects of bedrock permeability •Perched water tables •Contamination Problems -Overpumping -Salt water -Purification -Limestone bedrock Dissolved ions
Driving Mechanisms of plate tectonics
•Convection currents in the mantle •Plates are part of the convective cell -Slab pull -Ridge push •Hot plumes
World Ocean
•Covers 70.8% of Earth's surface •Not evenly distributed on surface •Average depth 3800 m •Trenches deepest part at 11,000 m
Climate change over past 100 my
•Cretaceous (ended 65 million years ago) -Warm -Inland seas (sea level high) -No ice caps -CO2 six to eight times greater than presently •Climate starts to cool in Eocene (50 my) •Glaciers form in Antarctic about 35 my •Antarctic ice sheet forms about 10 my •Northern hemisphere ice ages start about 2 my
Ocean water currents
•Deep water currents •North Atlantic Deepwater formation •Global "conveyer belt" and global climate •Aka thermohaline circulation
Streams
•Definition: a body of water that flows downslope in a clearly defined passageway and transports particles and dissolved material •Streams are part of the hydrologic cycle •A stream runs in its channel and the sediment it carries is its load •A stream drains its catchment area (its drainage basin) •Drainage basins are separated by divides
Dynamics of Streamflow
•Discharge-the volume of water passing a point in a given time •As a stream flows down its profile it changes its behavior -Gradient decreases (concave upward profile) -Velocity increases -Discharge increases (cross sectional area x vel) -Channel width and depth increase •Stream velocity greatest in center of channel
drainage networks
•Drainage networks are the patterns of streams and tributaries that drain an area •Drainage networks separated by divides •Characteristics: -One way -Smaller streams flow into larger streams -Tributaries of same order are same length -Even spacing of tributary mouths downstream
El Nino
•El Nino/Southern Oscillation (ENSO) -Flip-flop of high/low pressure areas in equatorial Pacific •Normal Times -Trade winds blow east to west at low latitudes -Upwelling in east-due to Peruvian cold current -Warm water piles up in west (by up to 30 cm) -Low pressure in western Pacific •El Nino (every 2 to 7 years) -High pressure increases in western Pacific -Trade winds slacken or even reverse -Warm water pool moves east -Upwelling off South America stops -Rainfall in western Pacific stops
Seismic waves
•Elastic waves through rock •Body Waves: •P wave -First arrival -Compressional wave •S wave -Secondary arrival -Shear wave
Shoreline Features
•Erosional features -Wave-cut cliffs -Wave-cut platforms -Arches -stacks
Early Paleozoic (0.5 Ga-0.36 Ga)
•Explosion of life forms -Snowball Earth -Hard Parts Developed -Multicellular animals •Continents around the South Pole •Life Forms -Trilobites -Brachiopods -Cephalopods
Winds
•Factors affecting wind speed and direction •Air pressure gradient •Drives winds •Ultimately comes from solar energy •Coriolis effect •Only affects moving objects •To the right in NH •To the left in SH •Friction •Affects winds lower than about 1 kilometer
Near surface atmospheric temperatures
•Factors controlling average temperature of atmosphere -Land vs. Water -Altitude -Geographic position -Albedo and cloud cover
Mountain Belt Types
•Fold and Thrust Belts -Due to convergence -Sedimentary and volcanic rocks -Deep and shallow marine rocks •Fault Block Mountains -Due to extension -Basin and Range, Nevada (eg.) -Listric normal faults -Horsts and grabens •Upwarps -Arching -mid-continent
Rock Deformation: Folding (ductile behavior)
•Folding (ductile behavior) -Syncline -Anticline -Recumbent (overturned) folds •Plunging folds -Syncline (youngest in center) -Anticline (oldest in center) •Symmetrical and Asymmetrical folds
Where glaciers form
•Form anywhere with snow accumulating over a year •High latitudes (arctic and antarctic regions) •High elevations (can form in tropics at high elevations) •Snowline -Elevation above which is permanent snowfields
Stratigraphic Correlation
•Fossils •Lithology •Magnetostratigraphy Tephra (volcanic ash layers)
Glacial Deposits
•Glacial drift -Till -Stratified drift •Loess -Windblown dust •Glacial erratics •Moraines -Lateral, medial, and terminal (end) -Ground moraine •Outwash plain -Kettles -Drumlins -Eskers -Kames
Past Glaciations and Climate
•Glaciations and Interglacials in recent past -We are currently in an interglacial -Interglacials last about 10,000 years -Glaciations last about 100,000 years -There have been 30 glaciations in the past 2 million years -Most recent glaciation ended 10,000 years ago •Older records of glaciations (and climate) -Glacial periods (interglacials and glaciations) every 200-300 million years -Cretaceous was particularly warm period
Temperate and Polar Glaciers
•Glaciers classified by internal temperature as well as size and shape •Temperate glacier -Ice is near pressure melting point •Polar Glacier -Always below pressure melting point
Geostrophic Winds
•High altitude winds/no friction with ground •Direction only affected by balance between Coriolis force and air pressure gradient •Geostrophic winds blow parallel to isobars
Recent Global Change
•Historic records of global average temperature only go back to about 1850 •They show a steady rise in average global temperature during the past 150 years •See about a 0.8˚C rise since the late 19th century
Evidence of climate change
•How do we know climate has changed in the past? -Historical records •Past hundreds of years •Proxies (wheat prices, dates of ice out, etc.) -Geologic records •Geologic time periods •Proxies for climate (e.g. oxygen isotope record of global ice volume) •Important to study, so we can get a better sense of how climate may change in the future
Desert Landscape Characteristics
•Interior Drainage •Playa Lakes •Alluvial Fans
Desert Landscape Evolution
•Interior Drainage and playa lakes •Alluvial fans coalesce along mountain front to form bajada •Mountains eventually worn down to inselbergs with pediments •Each of these stages can be observed in the Basin and Range (initiated by tectonics)
How groundwater flows
•It flows from recharge area to discharge area (generally downhill) •It can be discharged faster than it is recharged (it can be mined) •Darcy's Law controls the flow rate: -Q/A = k x h/l -Q=discharge, A=cross-sectional area of flow k=permeability, h/l=hydraulic gradient (head)
The Jet Stream
•It is 1000s kms long •It is several kilometers thick •Winds in jet stream blow at 100-200 mph •It is located at high elevations, at the tropopause (6-9 miles high) •The undulations in the jet stream are called Rossby waves, they affect the position of the jet stream-which affects weather at mid-latitudes
Relative Humidity
•It is a percentage •=(water in air/total amount of water the air could hold) x 100 •The amount of water the air could hold is dependent on temperature •The hotter the air the more water the air could hold.
Formation of Groundwater
•It is formed as part of the hydrologic cycle •It is formed by infiltration of rainwater into the ground •It moves slowly downhill to join runoff in streams and ponds and swamps
groundwater
•It is the water in spaces within bedrock and regolith •0.6% of all water on Earth •94% of all freshwater on Earth •40 times the water in lakes and ponds •Provides 50% of the world's drinking water
Karst
•Karst topography or landscape occurs when limestone bedrock is eroded (dissolved) by groundwater •Causes hummocky topography •Causes sinkholes and caves •Pollution can go a long distance in groundwater (underground rivers)
Air Masses
•Large body of air with similar temperature and moisture conditions -1000 miles across -Several kilometers thick •It affects weather as it moves into an area •Gets its characteristics from its source area -cP continental polar (cold, dry) -mP maritime polar (cold,wet) -cT continental tropical (dry, warm) -mT maritime tropical (wet, warm) •cP and mT affect our mid-latitude weather the most
Chemical Weathering-Climate
•Long term negative feedback cycle between chemical weathering and climate •Warmer climate from more CO2 leads to increased chemical weathering •More chemical weathering pulls CO2 out of atmosphere puts it into dissolved carbonate which becomes limestone •Has time scale of millions of years
Longshore Current
•Longshore current occurs between breaker zone and beach •It flows parallel to the beach •Caused by waves hitting the beach at a slight angle
Convergent and Divergent Flow
•Lows/Convergent Flow/Cyclones -Winds flow toward the center -Coriolis force drives to right (in NH) causes CCW spiral -Winds diverge aloft -Leads to cloud formation and precipitation •Highs/Divergent Flow/Anticyclones -Winds blow outward (away from center) -Winds spiral CW due to Coriolis force -Convergence occurs aloft -Clear, cloudless skies (air descends-heats adiabatically)
Chemical Weathering of Mafic Minerals
•Mafic minerals also completely dissolve in chemical weathering •Example: pyroxene will completely dissolve •Fe++ will go into solution •If comes in contact with O2, it will change to Fe+++ and precipitate as iron oxide (rust) •Causes red color on some rock surfaces
ocean tides
•Marine tides-every 12 hours •Gravitational force of Moon and Sun -Moon's effect predominates -Causes two tidal bulges (near and far side of Earth) -Affects ocean and solid Earth -Drag slowly decreases Earth's rotation rate •Neap and Spring Tides -Spring tides-exceptionally high (moon and sun aligned) -Neap tides-little difference between high and low (moon and sun at right angles)
meanders
•Meanders are one aspect of downstream stream behavior •This looping behavior is also seen in straight channels and in ocean currents •Meanders will grow and change •Meander parts: -Point bar -Cut bank
absolute ages
•Mesozoic-Cenozoic Boundary (66 Ma) •Paleozoic-Mesozoic Boundary (252.2 Ma) •Precambrian-Paleozoic Boundary (541 Ma) •Earth forms: 4, 600 Ma
Geologic (Deep) Time
•Modern Geology and Deep Time •James Hutton -Founder of modern geology -Siccar Point (one of locations that clarified his thinking) •Uniformitarianism -The present is the key to the past -vs. Catastrophism •(we will talk about modern catastrophism (impacts), later)
How a Glacier Moves
•Moves downhill due to gravity (cms/day) •Moves faster in center •Moves faster near its surface •Moves by various internal processes -Basal sliding -Plastic deformation •Sudden fast movement called surges (km/yr)
formation of glaciers
•Must accumulate more snow in winter than melts in summer •Pressure of burial transforms snow to glacial ice -Permanent snowfields -Firn -Glacial Ice -Can take anywhere from 10 years to 1000s of years
Mountain Building- Convergence Zones
•Ocean basin closes •First, ocean-continent convergence (Andes) •Allochthonous terranes collide •Final, continent-continent collision (Himalayas, Appalachians)
Soil Types
•Old Terms for Soils: -Pedalfers -Pedocals -Laterites •Modern Terms for Soils -Aridisol: in desert conditions -Alfisol: Al and Fe and clay horizons -Ultisol: soil that is heavily leached
Early Earth History
•Origin of the Earth •Nebular Hypothesis •Chemical condensation model of solar system formation •Iron catastrophe and differentiation of Earth •Early Atmosphere of Earth •Volcanic outgassing -Carbon dioxide -Water -Nitrogen •Oxygen from photosynthesis -Didn't see big increase until beginning of Paleozoic
Metamorphism and Subduction Zones
•Paired metamorphic belts and subduction zones - Blueschists (high P, low T) - Greenschists and amphibolites (low P, high T)
Post-WWII supporting evidence(plate tectonics)
•Paleomagnetism -Apparent polar wander -Seafloor spreading and geomagnetic reversals •Seismology -Patterns of global seismicity (earthquakes) -Benioff-Wadati zones -Transform faults •Deep sea drilling of marine sediments •Seafloor bathymetry (depth)
Late Paleozoic (0.36 Ga- 0.248 Ga)
•Pangea assembled -Continent-continent collision •Life Forms -Devonian fishes -Amphibians -Ferns -Gymnosperms •Mass extinction event at end of Paleozoic -Climate change? -Bolide?
Mesozoic (0.248 Ga-.065 Ga
•Pangea leads to dry climate •Atlantic Ocean forms •Subduction in western NA •Life Forms -Dinosaurs •Hard-shelled eggs -Gymnosperms dominate -Flowering plants (angiosperms) develop •K-T extinction event -Iridium layer -Bolide Volcanism
Factors affecting Soil Formation
•Parent material (what soil is derived from) •Residual soils-bedrock •Transported soils-unconsolidated material •Easily weathered material aids soil formation •Time -Thicker the soil, the longer it took to develop-can be 1000s to 10,000s of years •Climate -Most important factor in soil formation -Hot, humid climates make soil faster •Plants and animals -Furnish organics to soil -Vegetation defines soil types •Slope -Steep slope-soils are thin -Bottom lands-thick and dark soils
Continental Margins
•Passive continental margin •Active continental margin •Submarine canyons and turbidity currents -Turbidites -Graded bedding -Deep sea fans
Evolution of a continental margin: illustrates Wilson Cycle
•Passive margin forms by rifting •Ocean basin closes •Tectonostratigraphic terranes accreted •Continent-Continent collision -Causes orogeny -Folding and faulting -Deep marine sedimentary rocks deform first -Continental shelf sedimentary rocks deform next •All this illustrates the Wilson Cycle
Glacial Erosional Features
•Plucking and abrasion •Glacial striations •U-shaped valleys and hanging valleys •Horns and aretes •Cirques •Pater noster lakes •Roche moutonee
Polar Front
•Polar Front is the boundary between the polar cell and the mid-latitude (Ferrell) cell •At the polar front there are temperature gradients and storms •At the polar front the troposphere thins •There is steep gradient in air pressure at high elevations-therefore a strong geostrophic wind-THE JET STREAM
Porosity and permeability
•Porosity is the volume of rock with pore spaces •Permeability is the interconnectedness of the pore spaces (allows flow through the rock) •Aquifer has high permeability (and porosity) (e.g. sandstone) •Aquiclude or aquitard has low permeability (e.g. shale)
Remembering the Time Scale
•Queens- Quaternary •Two- Tertiary •Calls- Cretaceous •Jacks- Jurassic •Three- Triassic •Poker- Permian •Play- Pennsylvanian •Maybe- Mississippian •Day- Devonian •Some- Silurian •Over- Ordovician •Come- Cambrian
Geologic Time-Absolute Dating
•Radioactive Decay: •Isotopes •Alpha particles •Beta particles •Electron capture •Half life •Radiometric Dating: •Parent and daughter isotopes •14C dating •K-Ar dating, Ar-Ar dating •U-Pb dating •Rb-Sr dating
Earthquake Magnitude
•Richter magnitude is based on the amplitude of ground motion •Richter magnitude is logarithmic -Measure changes in ground motion 10 fold -M=log(X/T) + Y •Energy released with each Richter magnitude increases 30 fold •Magnitude related to size of fault rupture •Mercalli scale is best on qualitative observations
Appalachian Mountains
•Rifting (600 ma) -Iapetus Ocean •Taconic Orogeny (500-450 Ma: Ordovician) -Island arc collision •Acadian Orogeny (400-350 Ma: Devonian) -Micro-continent collision •Alleghanian Orogeny (300-250 Ma: Permo-Carboniferous) -Africa collides (continent-continent collision)
Composition of Seawater
•Salinity averages 35 ppt •4 most common salts: -NaCl -MgCl2 -Na2SO4 -CaCl2 •Source of ions: -chemical weathering of rocks on land (cations) -Anions from volcanic eruptions •Steady state equilibrium between supply and removal -By biological processes and adsorbtion on clay particles
Local Wind Systems
•Sea and Land Breezes -Due to different heat capacties of land and water -Day-sea breeze -Night-land breeze •Mountain and Valley Winds -Driven by mountains heating and cooling quicker than valleys •Chinooks -Warm, dry air was heated adiabatically as it descends -Also called The Foehn or the Santa Anas •Katabatic Winds -Cold mountain air flows down to lower area
Longshore drift
•Sediment movement along beach caused by continual swash and backwash •Caused by waves hitting the beach at a slight angle
Destruction from Earthquakes
•Seismic vibrations -Damage depends on nature of ground •Soft sediments amplify •Tsunami -Seismic sea waves -Caused by seabed faulting (or submarine landslides) •Landslides and Subsidence •Fire -Big factor in 1906 San Francisco
Earth's internal structure
•Seismic waves allow delineation of internal structure •Faster seismic velocities mean denser rocks •Seismic waves are refracted at seismic velocity boundaries •Discontinuities -Moho -Mantle-outer core •Compositional layering -Crust -Mantle -Inner and outer core •Rheological layering -Lithosphere -Asthenosphere -Mesosphere -Inner and outer core
Types of Volcanoes
•Shield Volcanoes •Stratovolcanoes (composite) •Cinder (tephra) cones •Also: -Collapse calderas -Fissure eruptions
Earthquake Prediction
•Short Term -Precursors •Uplift •Subsidence •Strain •Electromagnetic -China-Haicheng, Feb. 4, 1975-M=7.3 (predicted, low loss of life) vs. Tangshan, July 28, 1976-M=7.8(high death toll, > 255,000) •Long Range -Statistical probability of earthquakes -Seismic gaps
Soils
•Soil is the interface between Earth subsystems •Soil is the bridge between the animate and inanimate worlds (biosphere and geosphere) •Soil is a combination of mineral, organics, water, and air •Regolith is term for rock and mineral fragments produced by weathering -It is not soil
Soil Erosion
•Soils are critical to the survival of our species •Soil eroded by natural processes -Sheet erosion -Rills and gullies -Soil will become sediment •Human activity has increased the rate of soil erosion •Estimate: 1/3 of the world's cropland topsoils are being eroded faster than they are replenished naturally
La Nina
•Sometimes the "normal conditions" during ENSO flip-flop are "over normal"-overshoots on return from El Nino to normal conditions •Have colder than average surface conditions in eastern Pacific •Teleconnections -Colder than normal air over Pacific NW and northern Great Plains -Warmer than average conditions in rest of US -Greater Atlantic hurricane activity
Shoreline Depositional Features
•Spits •Hooks •Baymouth bar •Tombolo
stream load
•Stream load can be divided into three parts -Bed load •Too heavy to be kept in suspension -Suspended load •Settling velocity of particles is less than stream velocity •Kept in suspension by turbulent flow -Dissolved load •Ions come from chemical weathering •eg., HCO3, Ca, SO4, Cl, Na, Mg, K •Grain size of load decreases downstream -Even though velocity greater, abrasion during transport reduces grainsize •Competence-largest grains carried •Capacity-how much load can carry •Saltation-bouncing transport of grains
Ocean Currents
•Surface currents •Driven by atmospheric circulation •Gyres •Coriolis Force -CW in northern hemisphere, CCW in southern hemisphere -Conservation of angular momentum
Vertical Stratification of Seawater
•Surface salinity is a function of evaporation vs freshwater supply •Sea Surface Temperature (SST) is important to global climate -It affects evaporation -Seawater has a high heat capacity
marine Sediment Types
•Terrigenous -Clays (red) and other land derived •Biogenous -Calcareous ooze -Siliceous ooze •Hydrogenous -Manganese nodules •Climate change and sediment record
Soil Texture
•Texture depends on grain size distribution of particles •Texture important because it controls ability to hold water •Describe texture with ternary diagram (see next slide)
Fronts
•They separate air masses of different densities •The boundary of the front slopes so that warm air overlies cool air •Warm Fronts -Warm air moves over and advances on cool air -Boundary has low slope -Air rises and forms clouds/precipitation -Slow movement means rain over extended period\ •Cold Fronts -Cold air advances/pushes warm air out of the way -Boundary has steep slope -They move rapidly/air rises more quickly than for warm front/stormier than warm front •Cold Fronts -High gusts/downpours -Clearing occurs soon after they pass -Cooler air after they pass •Stationary Front -Air moves parallel to the boundary •Occluded Front -Cold front overtakes a warm front
Severe Weather
•Thunderstorms -Associated with cold fronts -Violent storms -Updrafts caused by warm air and latent heat of condensation -Downdrafts occur when updrafts can't maintain air up-tends to eventually dissipate the storm
Severe Storms
•Tornadoes -Intense lows -Funnels of high winds -Associated with cold fronts -Formed from mesocyclones in thunderstorms -Move typically, SW to NE, because they form along cold front in a zone of SW winds (see MLC)
Transform faults
•Transform faults have "strike slip" motion -Offset of active spreading ridge -Not passive feature •Transform fault transforms motion of other plate boundaries
Regional metamorphism
•Typically occurs during mountain building •In plate tectonics this occurs in collision of continents •Also called dynamothermal metamorphism •Occurs deep in crust under rising mountains -See increasing metamorphic grade of rocks as T and P are increased by burial
Magma characteristics
•Viscosity: - How easily the magma flows controlled by silica content - High silica, high viscosity • Temperature: - High temperature magmas are less viscous - Lower temperature magmas are more viscous **Example: Basaltic magma - high temperature, low viscosity
Weather changes associated with Mid Latitude Cyclone
•Warm front passes -Light precipitation -Wind from E-SE then from W-SW -Clearing •Cold front passes -Walls of clouds -Heavy precipitation -Winds from SW to W-NW
water table
•Water table is the top of the saturated zone in bedrock or regolith •Surface between the saturated and aerated zones •It follows the general surface topography •In humid environments, it intersects the surface at lakes and streams •In arid environments, the water table is below streams and lakes •Water table depth depends on the balance between recharge and discharge
Wave erosion and sediment transport
•Wave refraction •Waves are refracted (bent) to approach beach nearly head on -First part of wave to "feel bottom" slows down -Part of wave in deeper water "catches up" •Wave refraction causes wave energy to be focused on headlands (wears them down preferentially) •Wave refraction reduces wave energy to embayments (fills with deposition of sediment)
Ocean Waves
•Waves in deep water •Motion is circular •Wave velocity=wavelength/wave period •Wave base depth is 1/2 of wavelength •Wave base in deep water typically 300 m •Driven by winds across fetch
Atmosphere
•Weather vs. climate -Weather is short term -Climate is long term average weather •Composition of the Atmosphere •Major components of dry air >Nitrogen-78.08% >Oxygen-20.95% >Argon-0.93% >Carbon dioxide-0.036% •Minor components (variable) >Water vapor (carries latent heat) 0-4% >Methane >Nitrous oxide aerosols •Greenhouse effect •Greenhouse gasses -Water vapor -Carbon dioxide -Methane •Ultraviolet light -Screening effect of ozone -UV effects on life •Aerosols -Condensation of precipitation -Screen incoming radiation
Geologic Processes in Arid Climates
•Weathering -Chemical weathering occurs, but less important than mechanical weathering -Soils are thinner and have soluble minerals -Not much decaying organic matter •Role of water -Water is an important erosional agent -Wind is important in arid climate, but not as important as water -Streams are ephemeral
Weathering and Soils
•Weathering is the surficial process that produces material for sediments and sed rx. •All three rock types subject to weathering •Two types of weathering -Chemical and physical -Work together to break down rocks
streams and drainage systems
•When it rains, 2 things can happen: -Infiltration: water seeps into the ground and becomes groundwater -Runoff: water runs downhill and becomes streams and rivers •This is part of the hydrologic cycle
wind erosion
•Wind erosion is important in arid regions -No moisture to bind dust particles •Wind erodes by deflation •Sculpts rocks -Ventifacts •Blowout -Depression in landscape caused by wind •Desert pavement- -Caused by wind erosion •Wind also erodes by abrasion
Intrusive Igneous Rocks
•aka plutonic rocks (Pluto-god of underworld) •Types of plutonic rocks: -Dike -Sill -Laccolith -Stock -Batholith
