GEO401 Concepts
The Climate System
involves interactions among the atmosphere, hydrosphere, biosphere, cryosphere, and lithosphere
igneous rock
rocks formed by the solidification of molten rock (basalt and granite)
crater
A bowl-shaped area that forms around a volcano's central opening
spreading center
A divergent boundary, marked by a rift at the crest of a mid-ocean ridge, where new oceanic crust is formed by seafloor spreading
diatreme
A structure formed when a volcanic vent and the feeder channel below it are left full of breccia as an explosive eruption wanes
rodinia
A supercontinent older than Pangaea that formed about 1.1 billion years ago and began to break up about 750 million years ago.
What is the theory of plate tectonics?
According to the theory of plate tectonics, the lithosphere is broken into about a dozen rigid plates that move over Earth's surface. Three types of plate boundaries are defined by the direction of the movements of plates in relation to each other.: divergent, convergent, and transform-fault boundaries. Earth's surface area does not change over time; therefore, the area of new lithosphere created at divergent boundaries equals the area of lithosphere recycled at convergent boundaries by subduction into the mantle.
Biosphere
All organic matter related to life near Earth's surface
mid-ocean ridge
An undersea mountain chain at a divergent boundary, characterized by earthquakes, volcanism, and rifting, all caused by the tensional forces of mantle convection that are pulling the two plates apart.
How does magmatic differentiation account for the variety of igneous rocks?
Because different minerals crystallize at different temperatures, the composition of magma changes as it cools and various minerals are withdrawn by crystallization.
How is the climate system energized?
By the solar radiation
Why is Earth not a perfect sphere?
Daily rotation causes slight bulges at equator and squashing at poles Mountains and valleys (topography)
How are igneous rocks classified?
Igneous rocks can be divided into two broad textural classes: coarse-grained rocks, which are intrusive and therefore cooled slowly; and fine-grained rocks, which are extrusive and cooled rapidly. Igneous rocks can also be classified on the basis of their silica content using a scale that runs from felsic (rich in silica) to ultramafic (poor in silica)
Inner Core
Inner sphere composed primarily of solid iron, extending from about 5150 km deep to the Earth's center at 6370 km solid metallic sphere suspended within the liquid outer core - "a planet within a planet"
What are the forms of igneous intrusions?
Large intrusive igneous bodies are called plutons. The largest plutons are batholiths, which are thick horizontal masses extending from a funnel-shaped central region. Stocks are smaller plutons. Less massive than plutons are sills, which lie parallel to the layers of bedded country rock, and dikes, which cut across those layers. Veins form where water is abundant, either in the magma or in the surrounding country rock.
Outer Core
Liquid shell composed primarily of molten iron, extending from about 2900 km to 5150 km in depth
How do plate tectonic processes affect magma production?
Magmas are produced at two types of plate boundaries. At spreading centers, peridotite rises from the mantle and undergoes decompression melting to form basaltic magma. At subduction zones, subducting oceanic lithosphere undergoes fluid-induced melting to generate magmas of varying composition. Mantle plumes within lithospheric plates are also sites of decompression melting that produce basaltic magmas.
How and where do magmas form?
Magmas form at places in the lower crust and mantle where temperatures are high enough for partial melting of rock. Because the minerals within a rock melt at different temperatures, the composition of magmas varies with temperature. Pressure raises the melting temperature of rock, and the presence of water lowers it. Because melted rock is less dense than solid rock, magma rises through the surrounding rock, and drops of magma come together to form magma chambers.
Deep Mantle
Mantle beneath the atmosphere, extending from about 400 km deep to the core-mantle boundary (about 2900 km deep)
What are some of the geologic characteristics of plate boundaries?
Many geologic features develop at plate boundaries, Divergent boundaries are typically marked by volcanism and earthquakes at the crest of a mid-ocean ridge. Convergent boundaries are marked by deep-sea trenches, earthquakes, mountain building, and volcanism. Transform faults, along which plates slide horizontally past each other, can be recognized by earthquake activity and offsets in geologic features.
Convection
Mechanical transfer of heat energy that occurs as a heated material expands, rises, and displaces cooler material, which is itself heated and rises to continue the cycle.
magnetic anomaly
One in a pattern of long, narrow bands of high or low magnetic intensity on the seafloor that are parallel to and almost perfectly symmetrical with respect to the crest of a mid-ocean ridge
Cyrosphere
Polar ice caps, glaciers, and other surface ice and snow
Lithosphere
Strong, rocky outer shell of the solid Earth that comprises the crust and uppermost mantle to an average depth of about 100 km; forms the tectonic plates
Hydrosphere
Surface waters comprising all oceans, lakes, rivers, and groundwaters
How are volcanic landforms shaped?
The chemical composition and gas content of magma are important factors in a volcano's eruptive style and in the shape of the landforms it creates. A shield volcano grows from repeated eruptions of basaltic lava from a central vent. Andesitic and rhyolitic lavas tend to erupt explosively. The erupted pyroclasts may pile up into a cinder cone. A stratovolcano is built of alternating layers of lava flows and pyroclastic deposits. The rapid ejection of magma from a large magma chamber, followed by collapse of the chamber's roof, results in a large depression, or caldera. Basaltic lavas can erupt from fissures along mid-ocean ridges as well as on continents, where they flow over the landscape in sheets to form flood basalts. Pyroclastic eruptions from fissures can cover an extensive area with ash-flow deposits.
magnetic time scale
The detailed history of Earth's magnetic field reversals as determined by measuring the thermoremanent magnetization of rock samples whose ages are known
How is the global pattern of volcanism related to plate tectonics?
The huge volumes of basaltic magma that form from oceanic crust are produced by decompression melting and erupted at spreading centers on mid-ocean ridges. Andesitic lavas are the most common lava type in the volcanic mountain belts of ocean-continent subduction zones. Rhyolitic lavas are produced by the melting of felsic continental crust. Within plates, basaltic volcanism occurs above hot spots, which are manifestations of rising plumes of hot mantle material.
continental drift
The large-scale movements of continents across Earth's surface driven by the plate tectonic system
seafloor spreading
The mechanism by which new oceanic crust is formed at a spreading center on the crest of a mid-ocean ridge. As two plates move apart, magma wells up into the rift between them to form new crust, which spreads laterally away from the rift and is replaced continually by newer crust.
intermediate igneous rock
are neither as rich in silica as feslic, nor as poor in silica as mafic
How can the age of the seafloor be determined?
Using thermoremanent magnetization. Magnetic anomaly patterns mapped on the seafloor can be compared with a magnetic time scale that was established using the magnetic anomalies of lavas of known ages on land. Seafloor ages have been verified through dating of rock samples obtained by deepsea drilling. Geologists can now draw isochron maps for most of the world's oceans, which allow them to reconstruct the history of seafloor spreading over the past 200 million years. using this method and other geologic data, geologists have developed a detailed model of how pangea broke apart and the continents drifted into their present configuration.
What are some hazards and beneficial effects of volcanism?
Volcanic hazards that can kill people and damage property include pyroclastic flows, tsunamis, lahars, flank collapses, caldera collapses, eruption clouds, and ash falls. Volcanic eruptions have killed about 250,000 people in the past 500 years. On the positive side, volcanic materials produce nutrient-rich soils, and hydrothermal processes are important in the formation of many economically valuable mineral ores. Geothermal heat drawn from areas of hydrothermal activity is a useful source of energy in some regions.
Asthenosphere
Weak, ductile layer of mantle beneath the lithosphere that deforms to accommodate the horizontal and vertical motions of plate tectonics
convergent boundary
a boundary between lithospheric plates where the plates move toward each other and one plate is recycled into the mantle
divergent boundary
a boundary between lithospheric plates where two plates move apart and new lithosphere is created
shield volcano
a broad, shield volcano many tens of kilometers in circumference and more than 2 km high, built by successive flows of basaltic lava from a central vent
island arc
a chain of volcanic islands formed on the overriding plate at a convergent boundary by magma that rises from the mantle as water released from the subducting lithospheric slab causes fluid-induced melting
peridotite
a coarse-grained dark greenish gray rock made up primarily of olivine with smaller amounts of pyroxene -dominant rocks in the earth's mantle, source of the basaltic magmas that form rocks at mid-ocean ridges
gabbro
a coarse-grained, dark gray intrusive igneous rock has an abundance of mafic minerals, especially pyroxenes, contains no quartz and only moderate amount of calcium-rich plagioclase feldspar
isochron
a countour that connects rocks of equal age
grain
a crystalline particle of a mineral
decompression melting
a decrease in pressure can make rock melt, given a sufficiently high temperature. because of convection currents in the mantle, mantle materials rises to Earth's surface at mid-ocean at a more or less constant temperature. as material rises and the pressure on it decreases below a critical point, the solid rock melts spontaneously, without the introduction of additional heat
pumice
a frothy mass of volcanic glass in which a great number of spaces remain after trapped gas has escaped from the solidifying melt
What are the characteristics of an economically valuable ore deposit?
a high concentration factor
volcano
a hill or mountain constructed from the accumulation of lava and other erupted materials
caldera
a large crater caused by the violent explosion of a volcano that collapses into a depression "supervolcanoes"
magma
a mass of hot, molten liquid rock
hardness
a measure of the ease with which the surface of a mineral can be scratched
mantle plume
a narrow, cylindrical jet of hot, solid material rising from deep within the mantle, thought to be responsible for intraplate volcanism
mineral
a naturally occurring, solid crystalline substance, usually inorganic, with a specific chemical composition homogenous (cannot be divided into smaller components)
transform fault
a plate boundary at which the plates slide horizontally past each other and lithosphere is neither created nor destroyed
magmatic differentiation
a process by which rocks of varying composition can arise from a uniform parent magma occurs because different minerals crystallize at different temperatures
hot spot
a region of intense, localized volcanism found far from a plate boundary; hypothesized to be the surface expression of a mantle plume
sill
a sheetlike body formed by the injection of magma between parallel layers of bedded country rock - concordant intrusions - range in thickness from a single centimeter to hundreds of meters, and they can extend over considerable areas
Mantle
a shell of silicate-rich rock
Mohs scale of hardness
a simple relative hardness scale of 1-10 and scratch test (ability of one mineral to scratch another)to help tell the difference between minerals
precipitate
a solid that forms and settles out of a liquid mixture
pangea
a supercontinent that coalesced in the late paleozoic era and comprised all present continents, then began to break up in the mesozoic era
lahar
a torrential mudflow of wet volcanic debris -can occur when a pyroclastic flow meets a river or a snowbank, when the wall of water-filled crater breaks, when a lava flow melts glacial ice, or when heavy rainfall transforms new ash deposits into mud
metallic bond
a type of covalent bond in which freely mobile electrons are shared and dispersed among ions of metallic elements, which have the tendency to lose electrons and pack together as atoms
stratovolcano
a volcano emits lavas as well as pyroclasts, alternating lava flows and beds of pyroclasts build a concave-shaped composite volcano lava that solidifies in the central feeder channel and in radiating dikes strengthens the cone structure.
sedimentary rock
all rocks formed as the burial products of layers of sediments , whether they were laid down on land or under the sea
weathering
all the chemical and physical processes that break up and decay rocks into fragments and dissolved substances of various sizes
fibrous/splintery fracture
an appearance like split wood
discordant intrusion
an igneous intrusion that cuts across the layers of the country rock it intrudes
porphyry
an igneous rock that has a mixed texture in which large crystals "float" in a predominantly fine-grained matrix
Geodesy
an old branch of Earth science that studies Earth's shape and surface
partial melting
as temperatures rise, some minerals melt and others remain solid
isotope
atoms of the same element with different numbers of neutrons
concordant intrusion
boundaries lie parallel to the country rock layers, whether or not those layers are horizontal
How are the geodynamo and plate tectonic system energized?
by Earth's internal heat
Weather vs. climate
climate - average conditions of earth's surface environment and their variation weather - conditions of earth at a specific time in a specific location
disseminated deposit
deposits of ore minerals that are scattered through volumes of rock much larger than veins
sulfide
compounds of sulfide anion (S^2-) and metallic cations, (ex: mineral pyrite, iron sulfide)
oxides
compounds of the oxygen anion (O^2-) and metallic cations, (ex: the mineral hermatite, iron oxide)
sulfate
compounds of the sulfate anion (S^2-) and metallic cations, (ex: mineral anhydrite, calcium sulfate)
ultramafic rock
consist primarily of mafic minerals and contain less than 10% feldspar rarely found as extrusives bc they solidify at high temps
mafic rock
contain large proportions of pyroxenes and olivines. relatively poor in silica but are rich in magnesium and iron, from which they get their characteristic dark colors melt at higher temperatures than felsic crystallize at higher temperatures than felsic
How can Earth's outer core be liquid while the mantle is solid?
contains less iron and more silicon and oxygen than the core
diorite
contains less silica and is dominated by plagioclase feldspar, with little or no quartz contain a moderate amount of the mafic minerals biotite, amphibole, and pyroxene, tend to be darker than granite
Crust
contains more silica than the mantle composed of low-density silicates (rich in aluminum and potassium) 46% oxygen, 28% silicon, + calcium, magnesium, Iron and other
obsidian
contains only tiny vesicles and so is solid and dense
how does fractional crystallization lead to magmatic differentiation?
crystals formed early are segregated from the remaining magma
geothermal energy
depends on the heating of water as it passes through a region of hot rock that may be hundreds or thousands of meters beneath Earth's surface
vein
deposits of minerals found within a rock fracture that are foreign to the country rock
trace element
elements that make up less than 0.01 percent of a mineral
ash-flow deposit
extensive sheets of hard volcanic tuffs caused by eruptions of pyroclasts on continents
rhyolite
extrusive equivalent of granite, light brown to gray, has same felsic composition and light coloration as granite, but is much more fine-grained many are formed largely/entirely of volcanic glass
pyroclast
form when fragments of lava are thrown high into the air
extrusive igneous rock
formed from material that erupts from volcanoes
Atmosphere
gaseous envelope extending from the Earth's surface to an altitude of about 100 km
hydrothermal solution
hot water solutions
How is a mineral ore deposit created by hydrothermal activity?
hot water solutions are formed around bodies of molten rock when circulating groundwater or seawater comes into contact with a magmatic intrusion, reacts with it, and carries off significant quantities of elements and ions released by the reaction. these elements and ions then interact with one another to form ore minerals, usually as the solution cools
rock cycle
how each type of rock is transformed into one of the other two types result of interactions between plate tectonic system and climate system
crystallization
how minerals are formed, the atoms of a gas or liquid come together in the proper chemical proportions and in the proper arrangement to form a solid substance
Which families of rock form at Earth's surface?
igneous, sedimentary
color
imparted by light, either transmitted through or reflected by crystals or irregular masses of mineral (some minerals have a range of colors)
granodiorite
intermediate igneous rock, light colored and looks something like granite, has abundant quartz, its predominant feldspar is plagioclase
What are the differences between intrusive and extrusive igneous rocks?
intrusive - from when magma intrudes into unmelted rock and cools slowly extrusive - when lava erupts at the surface and cools rapidly
The plate tectonic system
involves interactions among the lithosphere, asthenosphere, and deep mantle
The geodynamo system
involves interactions between the inner and outer cores
pluton
large igneous bodies formed deep in Earth's crust. They range in size from a cubic kilometer to hundreds of cubic kilometers
bomb
large particles hurled from volcano and streamlined by the air as they hurtle through it
magma chamber
large pools of molten rock form in the lithosphere as rising magmas melt and push aside surrounding solid rock contract as they expel magma to the surface in volcanic eruptions
large igneous province
large volumes of predominantly mafic extrusive and intrusive igneous rock whose origins lie in processes other than normal seafloor spreading (continental flood basalts, oceanic basalt plateaus, aseismic ridges produced by hot spots)
fissure eruption
largest volcanic eruptions, coming through large , nearly vertical cracks in earth's surface (sometimes tens of kilometers long) - main style of volcanism along mid-ocean ridges, where new crust is formed
What are the major types of volcanic deposits?
lavas are classified as basaltic (mafic), andesitic (intermediate), or rhyolitic (felsic) on the basis of their content of silica and other minerals. Basaltic lavas are relatively fluid and flow freely; andesitic and rhyolitic lavas are more viscous. Lavas differ from pyroclasts, which are formed by explosive eruptions and vary in size from fine ash particles to house-sized bombs.
rhyolitic lava
light in color, usually pink, produced in zones where heat from the mantle has melted large volumes of continental crust (ex: yellowstone volcano produces huge amounts) -lower melting point than andesite, most viscous, moves slowly and piles up rhyolitic volcanoes produce the most explosive of all volcanic eruptions
how do minerals form?
lowering temperature of a liquid below its freezing point is one way to begin crystallization (magma) also, as liquids evaporate from a solution (salt water)
volcanic ash
made up of extremely small fragments, usually of glass, that form when escaping gases force a fine spray of magma from a volcano.
siliciclastic sediment
made up of physically deposited particles, such as grains of quartz and feldspar derived from weathered granite. laid down by running water, wind, ice
basaltic lava
mafic, most common magma type, produced along mid-ocean ridges and at hot spots within plates, Hawaii is primarily basaltic lava basaltic eruptions are rarely explosive, occur when volcano is full and lava leaks out when cool - black/dark gray extremely fluid
lava
magma flowing out onto earth's surface
What is the engine that drives tectonic plates?
mantle convection, the energy for which comes from Earth's internal heat. gravitational forces act on the cooling lithosphere as it slides downhill from spreading centers and sinks into the mantle at subduction zones. subducted lithosphere extends as deep as the core-mantle boundary, indicating that the whole mantle is involved in the convection system that recycles the plates. Rising convection currents may include mantle plumes, intense jets of material from the deep mantle that cause localized volcanism at hot spots in the middle of plates.
density
mass per unit volume g/cm^3
fluid-induced melting
melting of rock induced by the presence of water that lowers its melting point
Which families of rock form in Earth's interior?
metamorphic
where on the ocean floor would you find basaltic magmas being extruded?
mid-ocean ridges
carbonate
minerals composed of carbon and oxygen, in form of carbonate anion CO3^2-, in combination with calcium and magnesium (ex:calcite)
polymorph
minerals with alternative structures formed from the same chemical element or compound (diamond and graphite are both from carbon, but graphite is less loosely packed)
basalt
most abundant igneous rock of the crust, underlies virtually the entire seafloor, dark gray to black, fine-grained extrusive equivalent of gabbro
rock
naturally occurring solid aggregate of minerals or nonmineral solid matter
biological sediment
new chemical substances formed by precipitation. ex: calcite forming when organisms die
chemical sediment
new chemical substances that form by precipitation (ex: halite forming from seawater evaporation)
pyroclastic flow
occur when a volcano ejects hot ash and gases in a glowing cloud that rolls downhill at high speeds
granite
one of the most abundant intrusive igneous rocks, contains abut 70% silica, contains quartz and orthoclase feldspar
intrusive igneous rock
one that has forced its way into the surrounding rock and solidified without reaching Earth's surface
crystal
orderly, three-dimensional arrays of atoms in which the basic arrangement is repeated in all directions
flood basalt
piles of immense basalt plateaus causes by eruption from fissures on continents that spread out in sheats over flat terrain
felsic rock
poor in iron and magnesium and rich in felsic minerals that are high in silica (quartz, orthoclase felspar, plagioclase feldspar)
sediment
precursors of sedimentary rocks, found at earth's surface as layers of loose particles, such as sand, silt, an the shells of organisms
lithification
process that converts sediments into solid rock by compaction (particles squeezed together by weight of overlying sediments into a mass denser than original), or cementation (minerals precipitate around deposited particles and bind them together)
andesitic lava
produced mainly in the volcanic mountain belts above subduction zones. (ex:andes) lower temperatures than basaltic, flow slower and lump
pegmatite
veins of extremely coarse grained granite cutting across much finer grained country rock
what kinds of minerals would you find in a mafic igneous rock?
pyroxenes and olivines
ore
rich deposits of minerals from which valuable metals can be recovered profitably
tuff
rocks created from small fragments (pyroclasts falling to earth and sticking together)
metamorphic rock
rocks formed by the transformation of preexisting solid rock under the influence of high temperatures and pressures
breccia
rocks formed from larger fragments of pyroclasts that fall to the Earth and weld together
geodesy
science of measuring the shape of earth and locating points on its surface
conchoidal fracture
showing smooth, curved surfaces
stock
smaller plutons, discordant intrusion
country rock
surrounding rock that magma intrudes
vein
tabular (sheetlike) deposits of precipitated minerals in the fractures hydrothermal vein deposits are the most important sources of metallic ores
fracture
tendency of a crystal to break along irregular surfaces other than cleavage planes, related to how bond strengths are distributed in directions that cut across cleavage planes
mineralogy
the branch of geology that studies the composition, structure, appearance, stability, occurrence, and associations of minerals
hydrothermal activity
the circulation of water through hot volcanic rocks and magmas
streak
the color of the fine deposit of mineral powder left on an abrasive surface when a mineral is scraped across it
why are intrusive rocks coarse-grained and extrusive rocks fine-grained?
the cooling time
bedding
the formation of parallel layers of sediment as particles are deposited
batholith
the largest plutons, great irregular masses of coarse-grained igneous rock that, by definition, cover at least 100 km^2 thick, horizontal, sheetlike or lobe-shaped bodies extending from a funnel-shaped central region, their bottoms may extend 10 to 15 km deep, and a few are estimated to go even deeper the coarse grain of batholiths results from slow cooling at great depths
dike
the major route of magma transport in the crust. sheetlike igneous bodies, cut across the layers in bedded country rock, discordant intrusions -sometimes form by forcing open existing fractures in the country rock, but more often they create channels through new cracks opened by the pressure of rising magma
viscosity
the measure of a liquid's resistance to flow -increases as silica content increases
silicate
the most abundant class of minerals in Earth's crust, composed of oxygen and silicon (2 most abundant elements in the crust), mostly in combination with cations of other elements
fractional crystallization
the process by which the crystals formed in a cooling magma are segregated from the remaining liquid rock
Uniformitarianism
the processes we see in action on Earth today have worked in much the same way throughout the geologic past. "the present is the key to the past"
volcanic geosystem
the rocks, magmas, and processes needed to describe the entire sequence of events from melting to eruption
erosion
the set of processes that loosen soil and rock and move them downhill or downstream to the spot where they are deposited as layers of sediment
crystal habit
the shape in which individual crystals or aggregates of crystals grow, depends on the planes of a mineral's crystal structure and the typical speed and direction of crystal growth
subduction
the sinking of oceanic lithosphere beneath overriding oceanic or continental lithosphere at a convergent plate boundary
texture
the sizes and shapes of a rock's mineral crystals or grains and the way they are put together
cleavage
the tendency of a crystal to split along planar surfaces, also the geometric pattern produced by such breakage. varies inversely with bond strength; strong bonds produce poor cleavage, weak bonds produce good cleavage, covalent bonds generally produce poor/no cleavage w ionic bonds producing good cleavage
plate tectonics
the theory that describes and explains the creation and destruction of earth's lithospheric plates and their movement over earth's surface
relative plate velocity
the velocity at which one lithospheric plate moves relative to another
andesite
the volcanic equivalent of diorite
dacite
the volcanic equivalent of granodiorite
luster
the way the surface of a mineral reflects light (metallic, vitreous, resinous, greasy, pearly, silky, adamantine)
specific gravity
the weight of a mineral divided by the weight of an equal volume of pure water at 4 degrees celsius
ophiolite suite
unusual assemblages of rocks that were characteristic of the seafloor but were found on land -consist of deep sea sediments, submarine basaltic lavas, mafic igneous intrusions -fragments of oceanic lithosphere that were transported by seafloor spreading and then raised above sea level and thrust onto a continent in a later episode of plate collision
regional metamorphism
where high pressures and temperatures extend over large regions (where plates collide), accompanies plate collisions that result in mountain building and the folding and breaking of sedimentary layers. many of these rocks have "folding" characterisitc
contact metamorphism
where high temperatures are restricted to smaller areas, as in the rocks near and in contact with a magmatic intrusion
