GEO401 Concepts

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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minerals crystallize at different temperatures, the composition of magma changes as it cools and various minerals are withdrawn by crystallization.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


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