Geology 1005 Test 1 - SK
Properties of minerals
-Color -Streak -Hardness -Cleavage -Fracture -Luster -Specific gravity -Special Properties
What is the difference between a hypothesis and a theory? (p. 8)
1) can take many forms, ranging from a general conceptual framework or model describing the functioning of a natural system, to a very precise mathematical formula relating several kinds of numerical data. 2)is a generally accepted explanation for a set of data or observations.
What drives plate motion?
1) convection cell model 2) ridge-push force 2) slab-pull force
What is the difference between a conglomerate, a sandstone, and a shale? (pp. 34-36)
1) is coarse to very coarse grained (>2mm) (Rounded clasts) 2) is medium to coarse grained(.06 - 2mm) (mostly quartz) 3) is very fine grained (<.004 mm) (breaks into platy sheets)
Given that the mantle of the Earth is 99% solid, how does magma (liquid, molten rock) form?
1. A reduction in pressure When material rises from the lower mantle into shallower regions, such as at hot spots or spreading centers, the corresponding reduction in pressure promotes melting of the rock, creating a magma. Recall that normally rock in the asthenosphere is mostly solid: the high temperatures promote a slight degree of melting, creating a fluid environment, but the normally high pressures also keep the rock mostly solid and prevent complete melting from occurring. 2. The addition of fluids (such as water) A subducting plate carries a lot of seawater embedded with it. As the plate descends, the water warms up and rises back up into the overlying rocks. The heated water promotes melting of those rocks, creating magma.
What are the three general categorical terms used by geologists to describe a volcano's activity?
1. Active: erupting, or erupted recently, or likely to erupt soon. 2. Dormant: has not erupted for hundreds to thousands of years but may erupt again in the future. 3. Extinct: was active in the geologic past but is not likely to erupt again due to changes in the underlying geology.
What are the two general categories of sedimentary rock? Within each category, how are the rocks organized / classified?
1. Clastic: consist of cemented together clasts (clasts = grains, fragments of other rock that have broken off of pre-existing rock through either physical or chemical weathering) In general, clastics are classified by the average grain size that makes up the rock. 2. Chemical: form from precipitated crystals or grow from solution.
What are the three main types of stress?
1. Compressive stress 2. Tensile stress (extension) 3. Shear stress
What are the three kinds of plate boundaries?
1. Divergent boundary 2. Convergent boundary 3. Transform boundary
What is the difference between the three different kinds of plate boundaries? (pp. 50-55)
1. Divergent boundary: two plates move apart from one another (e.g. mid-ocean ridge, continental rift). A type of tensile or extensional stress. 2. Convergent boundary: two plates move toward one another (e.g. subduction zone, continent-continent collision). A type of compressive stress. 3. Transform boundary: two plates slide past one another. A type of shear stress.
What are some of the precursors to a volcanic eruption?
1. Earthquake activity 2. Changes in heat flow 3. Changes in shape 4. Increases in gas and steam emission
two ways limestone can be formed
1. Marine invertebrates (e.g., coral, snails, clams, lobsters: invertebrate organisms that live in the oceans) extract dissolved ions from seawater and incorporate those ions to form their shells. When these organisms die, their shells remain, and can consolidate and lithify into a carbonate sedimentary rock called limestone 2. Limestone can grow directly from solution (no fossil precursor involved) via the precipitation of calcite (in waters that are saturated with calcite).
What are the three differentiated layers of the Earth?
1. Outer crust 2. Mantle 3. Core - inner and outer
What is each layer of the earth composed of?
1. Outer crust = oxygen and silicon 2. Mantle = iron, magnesium, silicon, and oxygen 3. Core = iron and nickel
Which areas of the US are at highest risk for major earthquakes? What is an intra-plate earthquake and how does this differ from that along the edge of a plate? (pp. 86-87)
1. Southern Alaska: sits above a subduction zone and a strike-slip fault. 2. California: San Andreas fault runs directly through San Francisco, as well as most of southern and central California (Los Angeles is also affected by off-shoots of this fault) 3. Missouri: the strongest earthquake in the US occurred along the New Madrid fault in Missouri in 1811-1812. Aftershocks continued over the next ten years. 12 million people now live in this area. 4. Charleston, South Carolina: magnitude 6.9-7.3 earthquake took place in 1886 5. Virginia: magnitude 5.8 earthquake in 2011, damaged the Washington Monument and National Cathedral. 6. Pacific Northwest: Portland, Seattle overlie a subduction zone to the west. Note that #3, 4, and 5 are all examples of intra-plate earthquakes: i.e., earthquakes that occur within a lithospheric plate, as opposed to at the border of two tectonic plates. Intra-plate earthquakes are far less common an event, but no less deadly in their impact.
Building codes for areas afflicted by earthquakes typically fall into one of three categories:
1. Substantial life safety 2. Damage control: 3. continued operation
In what three different types of plate tectonic settings are magmas created?
1. divergent plate boundaries (e.g. mid-ocean ridge) 2. subduction zones (e.g. off the west coast of South America) 3. hot spots (e.g. the island of Hawaii)
What is the difference between a plutonic and volcanic igneous rock with regard to i) their origin and ii) the size of their mineral grains? is the difference between a basalt and a granite? A granite and a rhyolite? (p. 34)
1. rocks that form from magma, a molten (hot) liquid that exists underground, found either in i) the belly of a volcano -the magma chamber - or ii) intruded underground between other rocks (as dikes and sills, terms to be defined later).are called intrusive, because they form within the Earth, underground. The magma in magma chambers can take thousands of years to cool down and solidify into rock. Because the cooling process is slow, crystals have time to form and can grow large enough to be seen with the naked eye: plutonic rocks are typically coarse-grained. Granite is an example of a plutonic igneous rock: it contains viewable crystals of silicate minerals such as quartz, feldspar, as well as ferromagnesian minerals like mica and amphibole. 2. molten igneous rocks created at or above the Earth's surface, usually extruded from a volcano in the form of lava. Igneous rocks that form above ground are called extrusive. Because volcanic rocks cool quickly, there is less time for large crystals to form, so volcanic rocks are typically fine-grained, most crystals cannot be seen with the naked eye. Basalt, a rock that makes up the ocean floor; and obsidian, a dark, glassy rock, are two examples of volcanic igneous rocks.
What two factors influence viscosity?
1. temperature: the higher the temperature, the lower the viscosity of the magma or lava. Fluids with a low viscosity flow more easily. 2. silica (SiO2) content: the higher the silica content, the higher the viscosity of the magma or lava. Recall that fluids with a high viscosity flow more slowly. The reason silica imparts a high viscosity is because the silica- oxygen tetrahedra (the molecular shape of SiO2) in the magma are thought to bind together more strongly, increasing resistance to movement.
What are the three major minerals that influence a magma's composition?
1. the material(s) from which the melt is derived, i.e., what elements are rising up from the mantle 2. the extent of melting of that source material 3. the tectonic setting (see above), which controls #1 & #2
What is the difference between the (1)focus and the (2)epicenter of an earthquake? (p. 64)
1. the point on the fault, within the Earth (i.e., underground), from which the earthquake energy propagates. The source of the quake. Also called the hypocenter. 2. the point on the Earth's surface directly above the focus (this can be marked on a surface map).
What is the difference between a foliated and non-foliated metamorphic rock?
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active margin
A continental margin that is colliding with another plate and as a result is geologically active where volcanoes occur
mafic magma
A mafic lava has a low silica content and a high mafic mineral content (the high mafic mineral content gives basalt its black or dark grey color). It has a low viscosity for a lava and flows relatively easily. The ocean floor is lined by basalt, which has all derived from a mafic lava extruded at a mid-ocean ridge. Basaltic lavas erupt at temperatures above 950°C (> 1700°F).
rock cycle
A series of processes on the surface and inside Earth that slowly changes rocks from one kind to another 1. this rock can be eroded bit by bit, ultimately forming a sediment that would form a sedimentary rock; or 2. further metamorphism could transform it into a gneiss; or 3. high temperatures could cause it to melt into a magma, turning it back into an igneous rock.
Mineral
A solid inorganic substance of natural occurrence.
Electrons
A subatomic particle with an electrical charge of -1; generally found orbiting an atomic nucleus
Where can examples be found, both within the continental US and within the oceans?
An example of a hotspot within the continental US is the Yellowstone hotspot, responsible for the geothermal features and volcanoes in the Yellowstone National Park area. In the oceans, one well-known hotspot is the Hawaiian hotspot, which has created the Hawaiian Islands, with the Big Island of Hawaii being the most recent and active volcano in the chain. These hotspot tracks demonstrate the motion of the Pacific Plate over the stationary hotspot, providing strong evidence for the theory of plate tectonics.
Curie temperature
As igneous rocks cool from a molten magma, the rocks cool below a specific temperature called the Curie temperature
ridge-push model
As new lithosphere is created at mid-ocean ridges, the older material is pushed away from both sides of the midocean ridge axis. MORs have a slope to them, and gravity is thought to play a role in pushing the older basaltic crust further away from the ridge
Why is the age of the seafloor no older than 200 million years old, whereas continental crust has been discovered that is over 4 billion years in age? (pp. 46-47)
As seafloor spreading progresses, previously formed rocks are continually spread apart and moved further from the ridge, while fresh magma rises to form new sea floor at the ridge
Limestone chemical formula
CaCO3 (calcium carbonate)
What were five different lines of evidence Wegener provided to show that the continents moved?
Coastlines. Glacial activity Fossil evidence: plants Fossil evidence: animals. Rock assemblages.
how are the three kinds of rocks related
Crystallization, erosion and sedimentation, and metamorphism transform one rock type into another or change sediments into rock.
Was Wegener's idea of continental drift accepted by the geologic community? Why or why not? (p. 43)
Despite all this evidence, Wegener lacked a mechanism to explain how the continents actually moved. It was this lack of a mechanism that caused his idea to be discredited, until its revival in the 1960s, when Wegener's theory of continental drift became incorporated as part of a larger theory called plate tectonics: the large-scale movement and deformation of the earth's outer layers.
displacement
Distance and direction of an object's change in position from the starting point.
What is a mid-ocean ridge (seafloor ridge)? (p. 45)
Divergent boundaries in the ocean
What is liquefaction and what hazard does it play when designing buildings to withstand earthquakes?
Earthquake vibrations can cause beds of wet sand or silt to lose their cohesion (the soil particles separate from one another) and become a slurry, like quicksand, unable to support whatever it on top of it (e.g., a building). The soil undergoes liquefaction as a result of the intense shaking, and the buildings tip over.
Where are earthquakes more likely to occur: in the lithosphere or the asthenosphere? Why?
Earthquakes are more likely to occur in the lithosphere because it's solid, brittle, and where tectonic plates interact. The asthenosphere, being partially molten and soft, doesn't experience earthquakes like the lithosphere does.
passive margin
Edge of a continent along which there is no tectonic activity areas within a plate that mark the boundary between a continent and an ocean
Cleavage
For many minerals, when they are broken into smaller pieces, the manner in which they break is not random. When a mineral breaks to form smooth flat surfaces that have a specific orientation in relation to the overall crystal structure, those planar surfaces are called cleavage planes. You will see examples in lab. Minerals may have 1, 2, or 3 sets of cleavage planes depending on the strength of the bonds holding the atoms together. Mica, which breaks off in thin sheets, has one plane of cleavage. So does graphite (discussed above). Halite (salt), which resembles small cubes when it breaks apart, has three cleavage planes.
What is the general chemical formula of a silicate mineral?
General chemical formula: SiO2
What are some of the major hazards related to earthquakes? (e.g. aftershocks, tsunamis, etc.) (pp. 70-80)
Ground motion, aftershocks, ground failure, tsunamis, fire
What are hot spots?
Hotspots are places where hot magma from deep within the Earth creates volcanoes. They form when a hot rock column rises through the Earth's surface. Hotspots provide evidence for plate movement because as the plates move, they create a chain of volcanoes or islands.
What is a strain?
If the object is deformed as a result of that stress, causing a change in the object's shape, the resulting deformation is called strain.
If the entirety of Earth's history were laid out in a 24-hour day, when does our species, Homo sapiens, arrive? (p. 7).
It is not until 36 minutes before midnight do Homo Sapiens show up for this Earth party
What does an exponential growth curve look like?
J-shaped curve
What is the difference between magma and lava?
Magma is molten rock located below the surface; lava is molten rock erupted above ground.
What is a transform plate boundary, what type of plate motion is involved, and what type of geological features result from them? Where can examples of these be found? (p. 55)
Mid-ocean ridges are not long, continuous, uninterrupted undersea volcanic mountain chains, but rather short segments that are appear to be offset by fracture zones. It was originally thought that the entire length of the fracture zone - which can extend miles beyond the width of the mid-ocean ridge, was made by a type of fault called a transform fault, but it was later discovered that only the area of the fracture zone within the mid-ocean ridge itself showed any earthquake activity (and hence, movement). The area where the active movement of the fracture zone occurs is called a transform fault: in a transform fault, two plates slide past one another in opposite directions (one plate moves left, the other right), in a shearing motion. As a result of this shearing motion, earthquakes - commonly associated with transform faults - can occur.
Fracture
Not all minerals break smoothly along cleavage planes. Minerals that have no cleavage at all break to form irregular surfaces called fractures, or they may form a smoothly curving, clamshell-shaped surface called a conchoidal fracture. The minerals quartz and obsidian both display conchoidal fracture, as does glass. In fact, Stone Age tools such as flint (a variety of quartz) were made using minerals that expressed this property: the conchoidal fracture gave the rock a razor-sharp edge for hunting and slicing meat.
What are some common ferromagnesian minerals
Olivine (#1 in the silicate list above), for example, is called "olivine" because it is green in color: its formula is (Mg, Fe)2SiO4, and it is abundant in the Earth's mantle (the middle layer of the Earth).
Coastlines
On appearance alone, many continents look like they could fit back together: e.g., South America and Africa.
What did Wegener name his supercontinent? What happened to it? (see also lecture notes, Ch. 3, p. 1)
Pangea. It split.
chemical sedimentary rock
Sedimentary rock that forms when minerals precipitate from a solution or settle from a suspension limestone
How are earthquakes and their associated ground movement recorded?
Seismometers measure and record ground movement in vertical and horizontal directions
inclination
The angle of the magnetic field line relative to the Earth's surface
what is deformation
The bending, tilting, and breaking of Earth's crust.
What is the best-known silicate and what is its formula?
The best known is quartz, whose chemical formula is SiO2.
magnetic declination
The difference in angle between the geographic north pole and the magnetic north pole is called the magnetic declination. Declination varies depending on what latitude and longitude you live at. The current declination for our region is about 10°.
magentic pole
The ends of a magnetic object, where the magnetic force is strongest.
What happens to the growth of a population as it reaches its carrying capacity?
The growth rate should slow down as it is reached.
How does viscosity affect / influence the extent of lava flow, the type of volcanic eruption, and the shape of the overall volcano?
The higher the viscosity of a fluid, the more resistant it is to flow
What is the seafloor spreading hypothesis? Who proposed the idea?
The hypothesis proposed that new seafloor (new oceanic crust) was created at the mid-ocean ridges which then pushed the older crust away from the mid-ocean ridge on either side. The new seafloor produced at the mid-ocean ridge rose in the form of magma from deep within the Earth's mantle. Upon reaching the surface, the magma quickly cooled into rock, passing the Curie point as it did so, and so acquired the Earth's present magnetic field polarity (normal or reversed). As more magma rose up, the older materials were pushed apart on either side, and very, very gradually, on an pace of a few mm / year, the ocean floor slowly widened with time.
What is a lithospheric plate? What is a plate boundary?
The lithosphere is broken up into ~20 lithospheric plates. The contacts between the plates are called plate boundaries: of which 12 are major plates (large in size) and the rest are microplates (smaller in size). Some plates consist entirely of oceanic lithosphere, some have both continental and oceanic lithosphere. Plate boundaries are identified by the location of earthquakes, which occur in relatively narrow, distinct belts called seismic belts.
What specific layer within the Earth generates the Earth's magnetic field?
The magnetic poles are created by the Earth's magnetic field. The Earth's magnetic field is generated in the Earth's outer core.
folliation
The metamorphic rock texture in which mineral grains are arranged in planes or bands.
Cementation
The process by which dissolved minerals crystallize and glue particles of sediment together into one mass.
evidence for seafloor spreading
The rate at which new seafloor is created and the older seafloor is pushed away from the spreading center can give geologists an idea as to how quickly plates move. E.g., a 10 Ma section of oceanic lithosphere found 100 km away from the mid-ocean ridge has moved about 1 cm / year.
Paleomagnetism
The study of the alignment of magnetic minerals in rock, specifically as it relates to the reversal of Earth's magnetic poles; also the magnetic properties that rock requires during formation
How do hot spots provide evidence for plate tectonics?
This chain of volcanic islands can provide evidence for plate tectonics because it shows the movement of lithospheric plates over time.
How is the epicenter of an earthquake determined? (pp. 68-69)
To determine where the exact epicenter is on a map (direction), S-P arrival times from at least three different seismic stations are recorded, a method called triangulation (see p. 69, Fig. 4.9).
Rock Assemblages
Wegener found similar assemblages of rock formations across different continents matched those of a similar assemblage off the west coast of Africa, two continents currently separated by an ocean. - If the continents had once been together, these matching rock groups would have been adjacent to one another and formed a continuous band of rock. - Wegener proposed that not only did the coastlines of these continents match, but also their fossil and rock assemblages.
Fossil evidence: plants
Wegener mapped the occurrences of three species of fossil plant from the late Mesozoic (~100 Ma) and found that these fossils appeared over several - currently unconnected - southern continents. Wegener argued that the only way this could occur was if the continents were once all joined together: otherwise how could the plants have migrated across the sea?
Fossil evidence: animals
Wegener mapped the occurrences of various fossil animals, including a small, extinct, aquatic reptile called Mesosaurus, and found a distribution similar to that of the plants
Glacial activity
Wegener, who was a meteorologist, observed i) glacial striations ii) till deposits Wegener plotted the orientation of the striations and realized that i) the pattern would only make sense if the above continents were once all joined together (thus forming a single continental ice sheet), and that ii) part of Pangaea had to be at polar latitudes for the glacial ice sheet to develop in the first place.
What is the difference between geographic north and magnetic north?
When a compass needle points north-south, it does not point to the geographic north and south poles! Rather ,it points to the magnetic poles, which are (currently) roughly 10° off from the geographic pole. So, geologists define two "norths" and two "souths": geographic north versus magnetic north, and geographic south versus magnetic south
how do hotspots form?
When the lava hits the ocean, it cools and forms new rock. This continually builds - can become an island if it goes above the level of the ocean; since the plate is moving above this spot, it forms an island chain
volcanic arc
When the subducting plate slides under the overriding plate, a chain of volcanic mountains forms on the surface of the overriding plate: this volcanic chain is called a volcanic arc.
What is a subduction zone? What happens to the sinking plate? How is it determined which plate sinks?
When two plates collide, the denser plate bends and slides under down the overriding plate, forming a _______ Keep in mind the following: 1. Oceanic crust is composed of basalt, continental crust is composed of granite 2. Basalt is a denser rock than granite (basalt is composed of denser elements than granite) 3. Thus, oceanic crust is denser than continental crust.
Who was Alfred Wegener and what was continental drift? (pp.41-43)
a German geophysicist and meteorologist. In 1915, he published a book entitled "The Origin of the Continents and Oceans." The book hypothesized that the Earth's continents moved gradually over time and that, millions of years ago, the continents once fit together into a large supercontinent which was Pangaea. his theory was continental drift
Deep-ocean trenches
a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle These regions are called volcanic arcs and they form chains of active volcanoes
Hardness
a mineral's ability to resist scratching. We use a metric called the Mohs Hardness Scale to help identify minerals (see p. 27, Table 2.1). The scale lists the relative hardness of 10 standard minerals, with talc (a soft mineral) at #1 and diamond (a hard mineral) at #10. On this scale, your fingernail has a hardness of 2.5, glass has a hardness of 5.5, and quartz has a hardness of 7.
What is a rock? (p. 32)
a naturally occurring solid that is made up of one or more minerals, or mineral materials (e.g., glass, which forms from volcanoes).
How is the magnitude of an earthquake determined and (in general) what is the difference between the Richter scale(1) and the Mercalli intensity scale(2)? What is the difference between magnitude, amplitude, and intensity, in reference to earthquakes? What is the difference between an earthquake of magnitude 4 vs one of, say, magnitude 3 with regard to ground movement? ...with regard to energy released? (pp. 68-71)
a quantitative (objective) scale [quantitative refers to a numerical term, e.g. "It's 32.0°F outside," or "This dinosaur humerus is 2.2 m long."]. E.g. 1 The amount of ground motion is related to the magnitude of the earthquake. The current system, called the ___, was first developed by American seismologist Charles Richter in 1935 (and since modified), and based on the amplitude recorded by the seismometer at seismic station ideally 100 km from the epicenter. Amplitude refers to amount of back-and-forth or up-and-down motion of the ground. The larger the motion, the higher the amplitude recorded by the seismometer pen. The Richter scale typically goes from 1.0 (mild) to 10.0 (severe). (1) is logarithmic: each increase in number represents a 10-fold increase in the maximum ground motion, and a ~30-fold increase in energy. A magnitude 8 quake is 10x stronger than a magnitude 7 quake, and 1,000x greater than a magnitude 5 quake. A magnitude 8 quake releases 30x more energy than a magnitude 7 quake, and ~1 million times more energy than a magnitude 4 quake. There are about 100,000 magnitude 3 quakes each year, but only 1-2 magnitude 8 quakes annually. Intensity: a qualitative (subjective) scale [qualitative refers a descriptive term, e.g. "It's cold outside."]. E.g. 2 2 is based on the impact of the earthquake
thrust fault
a special type of reverse fault where the fault angle slope is 30° or less. A thrust fault is also called a low-angle reverse fault.
What is the difference in composition between the inner core and outer core?
a. Outer core - liquid b. Inner core - solid
What is the difference between oceanic and continental lithosphere? (p. 50)
a. is thin under the oceans, where it reaches a depth of 50 km (30 mi). b. is thicker under the continents, where it reaches a depth of 250 km (150 mi).
types of faults
a. normal fault b. reverse fault c. thrust fault d. Strike-slip faults 1) Right lateral strike-slip fault 2) Left lateral strike-slip fault e. oblique fault -
Inorganic
almost all minerals are not organic chemicals, with some exceptions, e.g., bat guano (apparently crystals grow in ancient deposits of bat guano). Technically speaking, coal is also not a mineral, since it is largely composed of organic matter. Also, minerals are crystalline, and keep their shape indefinitely, due to their crystalline atomic structure (see #4, below). This is as opposed to glass and plastic, which, while solid, are not crystalline. The arrangement of atoms in glass and plastic is disordered.
Neutrons
an electrically neutral subatomic particle with a mass approximately equal to one atomic mass unit; generally found within an atomic nucleus
anions
an ion with a net negative charge
Cations
an ion with a net positive charge
What is a fault?
are fractures (breaks) in beds of rock where sliding (movement) has occurred
Naturally occurring
as opposed to being formed synthetically, or manufactured
Lahars
ash flows that combine with water can turn into fast-moving mudflows called lahars. Victims get trapped in and die from super-heated mud. Lahars tend to follow stream channels. The water arrives from either rain or snow that was resting on the volcano's slope
Ions
atom that has gained or lost electrons, so it has a net electrical charge
Isotopes
atoms of a given chemical element having the same atomic number but different atomic mass numbers
examples of volcanic igneous rocks
basalt and obsidian
plastic deformation
beyond the elastic limit, the object can be deformed (undergoes strain) but does not return to its original shape. These changes are permanent (e.g., a glass blower folding hot glass; a rock layer undergoing folding)
ionic bonds
bonding due attraction between oppositely charged ions. Table salt, whose chemical formula is NaCl (read as "sodium chloride"), is an example of an ionic bond, where Na+ is the cation, and Cl- is the anion. The mineral version of salt is called halite.
covalent bonds
bonding involving sharing of electrons between atoms Water (formula: H2O) and hydrochloric acid (formula: HCl)
brittle deformation
break without taking on any change in shape (strain): e.g., a glass or plate that falls and shatters on the floor. The break occurs because the bonds that hold the atoms of that substance together rupture. Brittle deformation is characteristic of rocks at or near the Earth's surface (i.e., low temperatures and low pressures), leading to fractures and faults
Nonsilicates include the following
carbonates, sulfates, oxides, native elements
Color
certain minerals have a consistent color (e.g. the mineral malachite is green, the mineral azurite is blue, and gold is, well, gold); while others display a spectrum to due impurities that may be in the crystal structure (e.g. pure quartz is glassy, but a variety called rose quartz is pink, and amethyst is a quartz tinted purple). The mineral corundum is colorless in its pure form, but various impurities can turn it into gems such as rubies and sapphires.
Two types of sedimentary rocks
clastic and chemical
Tempature
colder rocks are brittle, warmer rocks deform plastically. The temperature of the Earth's interior increases with depth.
oblique fault
combo of dip slip and strike slip faults. Occurs on diagonal plane
What are feldspars? (p. 29)
composed of silicon, oxygen, aluminum, et al., are the most abundant silicate mineral in the Earth's crust (the thin outer layer of the Earth).
P-waves
compressional body waves. These are the fastest waves and can pass through both solid and liquid media. As they pass through the Earth, the material is alternately compressed and expanded. P stands for primary
clastic sedimentary rock
consist of cemented together clast
What are carbonate rocks? Provide an example. Where are they typically found / formed?
contain 1 atom of carbon bound to 3 atoms of oxygen (written as CO3). The most common carbonate mineral is calcite (CaCO3, also called calcium carbonate), which forms the rock limestone. Limestone forms by precipitating out of seawater, and is the major component of coral reefs (calcite also forms the mineral component your own skeleton). useful for building materials and manufacturing
sulfates
contain 1 atom of sulfur bound to 4 atoms of oxygen (written as SO4 2- ). Form by precipitation out of water, e.g., gypsum (CaSO4*2H2O), used in plaster of Paris and drywall construction. When sulfur is present without oxygen, the mineral is called a sulfide. Examples of sulfides include pyrite (fool's gold, FeS2, an iron sulfide) and galena (PbS, a lead sulfide): these minerals will crop up again when we talk about strip-mining run-off (sulfuric acid).
What are ferromagnesian minerals?
contain some amount of iron and/or magnesium, two other common elements found in the Earth's crust. These minerals are collectively termed and are usually darker in color (black, brown, green).
Definable chemical composition
contains a chemical formula, of one or more elements. Examples of minerals containing just one element are the minerals diamond and graphite - each consists solely of the element carbon. Some minerals contain over ten elements.
The individual minerals in a rock often form
crystals
Abyssal plains
deep, wide, flat regions of the ocean floor that lay 4-5 km below sea level.
What is stress?
defined as a force acting on an object per unit area (the amount of force acting on a specific area of an object).
displacement leads to
differentiation into three concentric zones
what are the three types of deformation
elastic, plastic, brittle
right lateral strike slip fault
f you are facing the fault and looking across at the other side, if the block across the fault slipped to your right, it is a right lateral strike-slip fault.
brittle deformation example
faulting
felsic lava
felsic lava has a high viscosity and flows slowly: the lava looks "thicker" or "goopie" Because their high viscosity also trap gases under pressure, felsic magmas can sometimes plug up the vents of volcanoes, causing the eventual eruption to be much higher in pressure and thus more explosive.
plastic deformation example
folding
extrusive rock
form above ground
igneous rock
form by crystallizing (cooling) from molten material (e.g., magma in a volcano) at very high temperatures.
metamorphic rock
form from the transformation of pre-existing igneous, sedimentary, or metamorphic rocks
intrusive rocks
form within the Earth, underground
pyroclastic flows
fragments of hot rock and spattering lava that erupt explosively out of the volcano. The largest blocks are called volcanic bombs and pose a threat simply due to their size and weight. Most larger pieces fall near the volcano's vent, but finer ash and dust particles can blanket a wider area and even circle their way across the globe and poses hazards both on the ground and to air travel
What is the concept behind paleomagnetism?
geologists realized that once a rock cools down, the magnetic minerals remain fixed in place and do not realign / reorient themselves if the rock formation drifts elsewhere over time. The rock thus preserves a record of the Earth's past magnetic field
clasts
grains, fragments of other rock that have broken off of pre-existing rock through either physical or chemical weathering
Lithification
he process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock.
Convection cell model
hot mantle material rises up at spreading centers (MORs), then spreads outward, pulling along the overlying lithosphere with it. Once the mantle material cools, it sinks at subduction zones, pulling the overlying lithosphere with it. The mantle material then rises back up again at the spreading center, creating a circular convection cell (in a typical convection cell, warm fluids rise, cold fluids sink).
What are convection cells and how does they play a role in plate tectonics?
hot mantle material rises up at spreading centers (MORs), then spreads outward, pulling along the overlying lithosphere with it. Once the mantle material cools, it sinks at subduction zones, pulling the overlying lithosphere with it. The mantle material then rises back up again at the spreading center, creating a circular convection cell (in a typical convection cell, warm fluids rise, cold fluids sink).
What is a caldera?
huge hole left by the collapse of a volcanic mountain
Left lateral strike-slip fault
if you are facing the fault and looking across at the other side, if the block across the fault slipped to your left, it is a left lateral strike-slip fault.
summary of three kinds of rocks
igneous rocks are formed from melted rock deep inside the Earth. Sedimentary rocks are formed from layers of sand, silt, dead plants, and animal skeletons. Metamorphic rocks formed from other rocks that are changed by heat and pressure underground.
plutonic igneous rocks
igneous rocks that form from magma, a molten (hot) liquid that exists underground, found either in i) the belly of a volcano -the magma chamber - or ii) intruded underground between other rocks (as dikes and sills, terms to be defined later) intrusive
What are the general three categories of rock
igneous, sedimentary, metamorphic
What are the four most common chemical elements in the Earth?
iron, oxygen, silicon, magnesium
What is doubling time? (pp. 13-14)
is the length of time required for a population to double in size.
sediments
loose, unconsolidated accumulations of mineral or rock particles that have been transported by wind, water, or ice, and redeposited elsewhere. Most sediment forms from the weathering (breakdown, erosion) of preexisting rocks, or by precipitating crystals out of solution. When the sediment is compacted or cemented together, it undergoes lithification and turns into a sedimentary rock
reverse polarity
magnetic north and magnetic south switch places: magnetic south lies near the north geographic north pole, and magnetic north lies near the geographic south pole. During a reversal, a compass pointing "north" would point to the southern hemisphere. Rocks that crystallized when the Earth's magnetic field had a reversed polarity are said to be reversely magnetized.
Solid
means that the mineral maintains its shape, and unlike liquids and gases, does not conform to the shape of its container (glacial ice is technically a mineral, but liquid water is not).
oxides
metal cations that bond to oxygen anions. Examples include iron oxides such as hematite (Fe2O3), and magnetite (Fe3O4, formerly called lodestone and amongst the world's first compasses) iron oxide, and iron oxides are also responsible for the reddish surface of the planet Mars (and the reddish color in most rocks, generally).
What are native elements? Provide an example. (p. 31)
mineral consists of a single element. The metal atoms are bonded by metallic bonds. E.g., copper (Cu), gold (Au), silver (Ag), tin (Sn), iron (Fe), platinum (Pt), etc.
What are silicates?
minerals containing silica
Luster
minerals that have a metal shine to them are called metallic, those that do not are called nonmetallic (aka glassy, earthy, silky).
volcanic rock
molten igneous rocks created at or above the Earth's surface, usually extruded from a volcano in the form of lava. - because volcanic rocks cool quickly, there is less time for large crystals to form, so volcanic rocks are typically fine-grained, most crystals cannot be seen with the naked eye
how sedimentary rocks form
multiple ways 1. by the cementing together of loose clasts (fragments or grains) that had been produced by physical or chemical weathering of pre-existing rock 2. by the growth of shell or by the cementing together of shells and shell fragments 3. by the accumulation and alteration of organic matter derived from living organisms 4. by the precipitation of minerals directly from surface-water solutions
5 components of "What is a Mineral"
naturally occurring, inorganic, solid, definable chemical composition, crystalline structure, formed by geological processes
Are the magnetic poles fixed?
no - they are constantly moving
Is carrying capacity a fixed number? Why or why not? (p. 15. also see lecture notes, p. 5)
not a fixed number - math equation thing ???
What is a convergent plate boundary, how many different types are there and how are they distinguished? Where can examples of each be found? What landforms do they produce? (pp. 52-54)
occur when two plates collide with one another. There are three kinds, depending on the type of lithosphere that makes up each plate: 1. Ocean-ocean: a plate of oceanic lithosphere collides with another plate of oceanic lithosphere 2. Ocean-continent: a plate of oceanic lithosphere collides with a plate of continental lithosphere 3. Continent-continent: a plate of continental lithosphere collides with another plate of continental lithosphere
shear stress
one part of a rock moves sideways past another across a plane, similar to how a deck of cards slide past one another when shuffled. Geologically, this occurs with transform (strike-slip) faults (see below).
What is the definition of a metamorphic rock?
one that forms when a pre-existing rock (called a protolith) undergoes a solid-state (does not melt) change in response to being buried and subjected to high temperatures, pressures, and/or reacts with hydrothermal fluids. The process is called metamorphism. The temperatures are typically high, but not high enough to cause the rock to completely melt. Because the rock remains in a solid state, what happens during metamorphism is that the rock recrystallizes internally: the atomic crystal lattice that makes up the rock reconfigures itself into a different - usually stronger - shape.
Where is the Earth's magnetic field generated?
outer core
What are the four most common elements in the Earth's crust?
oxygen, silicon, aluminum, iron
Cyanobacteria
photosynthetic bacteria that introduced oxygen to earth
grain
piece of mineral
two categories of igneous rock
plutonic and volcanic
accretion
process by which earth and other rocky planets were created, gravity collected the particles of dust, debris, ice, and metals into a homogenous mass that grew bigger with time. As it got hotter bc of impacts of collisions, radioactive elements, and pressure of the overlying materials, the denser minerals (like iron) began to sink toward the center of the planet, while the lighter minerals (like silicon) were displaced upwards.
differentiation
process by which the materials within a planet become separated and distributed into distinct layers or zones based on their composition and density.
Formed by geologic processes
produced in one of two methods a. solidification of molten rock (e.g. magma basalt), or direct precipitation from a water solution (e.g., halite); b. precipitated by organisms (e.g. limestone can form from the animal coral): aka biogenic minerals
What is the importance of cyanobacteria to origin and evolution of life on Earth?
raised oxygen levels, allowed for ability to support other forms of life
offset
refers to how much the ground has moved on either side of a fault. During an earthquake, the amount of offset can range from a few cm to several meters.
elastic deformation
region where the material will return to its original shape when the stress is removed
what is a foot wall?
rock surface below the fault
porphyry
rock that begins as a plutonic igneous rock but is erupted out of the volcano before completely cooling, and instead finishes its cooling quickly as a volcanic rock.
pressure
rocks are brittle at lower pressures; at higher pressures, rocks deform plastically. The pressure of the Earth's interior also increases with depth
Time (or, rate of deformation)
rocks are brittle when deformation rates are fast; under slow rates of deformation, rocks deform plastically.
sedimentary rock
rocks that form at or near the surface of the Earth in one of several ways:
How do sedimentary rocks form?
rocks that form at or near the surface of the Earth in one of several ways: 1. by the cementing together of loose clasts (fragments or grains) that had been produced by physical or chemical weathering of pre-existing rock 2. by the growth of shell or by the cementing together of shells and shell fragments 3. by the accumulation and alteration of organic matter derived from living organisms 4. by the precipitation of minerals directly from surface-water solutions.
limestone
seawater is precipitated (evaporated) until calcium is left. Calcium crystallizes into limestone which can be used to build or manufacture and is also a major component of coral reefs.
induced seismicity
seismic events caused by the actions of people
Seismologists classify earthquakes by the depth at which they occur within the Earth
shallow, intermediate, and deep earthquakes
S-waves
shear body waves. These waves arrive second and cannot pass through liquids. the material is moved side-to-side. S stands for secondary
What is the difference between "slab-pull" and "ridge-push"?
slab pull = the dense, down-going slab of lithosphere in the subduction zone pulls the rest of the trailing plate along with it, further opening up the spreading center at the mid-ocean ridge. Recall that older oceanic lithosphere (> 10 Ma, e.g.) sinks due to its density. As it does so, it pulls the rest of the plate along behind it, like an anchor pulling an anchor line. ridge push =As new lithosphere is created at mid-ocean ridges, the older material is pushed away from both sides of the midocean ridge axis. MORs have a slope to them, and gravity is thought to play a role in pushing the older basaltic crust further away from the ridge.
what are faults classified by
slope/dip - horiztonal or vertical displacement - the distance and direction that material on one side of the fault moves relative to material on the other side
Special properties
some minerals have properties that are unique and distinctive: e.g., calcite (CaCO3) effervesces (it forms bubbles) in hydrochloric acid (HCl); halite (NaCl) tastes salty; the mineral magnetite is magnetic, etc.
Roughly, how fast do plates move? (p. 57)
speed ~1 cm/year to ~10 cm/year. The speed is different from plate to plate, and can depend on how much active the plate currently is.
Protons
subatomic particle with a charge of +1 and a mass of approximately one atomic mass unit; generally found within an atomic nucleus
L waves
surface waves that cause the ground to ripple side-toside like a snake (L stands for Love, named after a seismologist)
R waves
surface waves that cause the ground to ripple up and down. (R stands for Raleigh, a physicist)
Within the depths of the Earth, rocks may behave elastically, plastically, or brittlely depending on the following:
temperature pressure strength (composition) time (rate of deformation)
What is carrying capacity?
the ability to sustain population at a basic, healthy, moderately comfortable standard of living.
Crystalline structure
the atoms in a mineral are arranged in a specific, repeating, orderly pattern (similar to a wallpaper or textile pattern, but in 3-dimensions): this is also known as a crystalline solid. The pattern that the framework of atoms composes is called a crystal lattice. (Other texts also include #6, below, in their definition)
Nucleus
the center of an atom, containing protons and neutrons
Streak
the color of a powder produced by pulverizing the mineral, usually obtained by scraping the mineral against a ceramic plate. The color of a mineral's streak of a mineral is not always the same as the color of the mineral itself. E.g., pyrite (fool's gold) appears gold, but its streak is black.
normal fault
the hanging wall slides down relative to the foot wall. This type of fault motion is observed during an extensional tectonic event, such as continental rifting and mid-ocean ocean rifts.
reverse fault
the hanging-wall slides up relative to the foot wall. This type of fault motion is characteristic of tectonic compression of the crust (convergent plate boundaries), as happens when two tectonic plates collide.
Which type of lava flow has the lowest viscosity: silica-poor or silica-rich? Which kind has the highest: silicapoor or silica-rich?
the higher the silica content, the higher the viscosity of the magma or lava.
normal polarity
the northern magnetic pole (where a compass arrow points to when pointing "north") lies near the northern geographic pole (the axis around which the Earth spins). Rocks that crystallize when the Earth's magnetic field has a normal polarity are said to be normally magnetized.
atomic number
the number of protons in an atomic nucleus; characteristic of a particular element
What is the lithosphere? Is it the same thing as continental crust?
the outer "shell" of the Earth, 100-150 km thick), this layer is "rigid," it does not flow: it is brittle, its materials bend or break. The thickness of the lithosphere varies:
Strike-slip faults
the plates slide past one another along the fault horizontally; there is no up-or-down motion, and no deformation may be involved.
What is the asthenosphere? How does it differ from the lithosphere? (p. 50)
the portion of the mantle that flows, this layer is "plastic". It lies directly under the lithosphere, and extends to a depth of 300 km (200 mi) into the mantle. While it is mostly solid, as it is part of the mantle, its high temperatures and pressures allow the rocks within it to flow plastically under stress: grains of rock within it have "partially melted".
Compaction
the process by which sediments are pressed together under their own weight
slap pull
the pulling of a tectonic plate as its edge subducts deep into the mantle
Specific gravity
the ratio of a mineral's density (mass/volume) relative to the density of water. Water is 1.0.
Atom
the smallest particle into which a chemical element can be subdivided
atomic mass number
the sum of the number of protons and the number of neutrons in an atomic nucleus
What is the Curie temperature?
the temperature above with a metal is no longer magnetized. The Curie temperature is unique for different types of metals
What is an earthquake?
the vibration of Earth produced by the rapid release of energy That energy is released when the stress exceeds the rupture strength of the rock, resulting in sudden movemen
slab pull model
the weight of the dense, down-going slab of lithosphere in the subduction zone pulls the rest of the trailing plate along with it, further opening up the spreading center at the mid-ocean ridge. Recall that older oceanic lithosphere sinks due to its density. As it does so, it pulls the rest of the plate along behind it, like an anchor pulling an anchor line.
What is a magnetic reversal?
this occurs when the Magnetic poles reverse. Magnetic North would become Magnetic South on a compass
What is a divergent plate boundary, what does it form, and what happens at this boundary? Where is such a boundary found? (p. 52)
two lithospheric plates move apart. Mafic magma rises up from the mantle to fill in the space, often erupting out through volcanoes that form in divergent boundaries (earthquakes are also common here). As the magma cools, it forms new crust (the new crust can be either oceanic or continental, depending on where the spreading center has formed).
coal
type of organic sediment that, similar to biochemical limestone in some ways, consists of many layers of carbon-rich (mostly plant) material that once thrived in swamps
strength (composition)
under similar conditions, hard rocks deform more brittlely, whereas softer rocks deform plastically
Mid-ocean ridges (MORs)
undersea volcanic mountain ranges that stretched for several thousand km, and whose peaks rose 2-2.5 km below sea level. - MORs were noted for being roughly symmetrical: the profile on one side of the ridge was roughly a mirror image of the other - they all turned out to be linked across the globe and they were active both volcanically (erupting) and seismically (i.e., produced earthquakes)
Compressive stress
when a rock is squeezed (like the walls of the trash compactor). Geologically, this occurs when two tectonic plates collide
Tensile stress (extension)
when a rock is stretched or pulled apart, tension is produced. Geologically, this occurs at mid-ocean ridges (which are a type of spreading center) as oceanic crust is pulled apart.
ridge push
when the force of gravity moves a plate downward and away from a ridge
In reference to population growth, what is exponential growth?
when the population growth rate is constant, and the individuals added per unit of time increases over time.
seismic belt
where earthquakes occur, relatively narrow, distinct belts
The Earth's lithosphere is broken up into
~20 lithospheric plates. The contacts between the plates - the lines where the plates meet - are called plate boundariesfdiv