Geo 101

Front 1

atmosphere

Back 1

mixture of gases, predominantly nitrogen, oxygen, carbon dioxide, and water vapor, that surrounds Earth

Front 2

Biosphere

Back 2

the totality of Earth's organisms and, in addition, organic matter that has not yet been completely decomposed

Front 3

Closed system

Back 3

any system with a boundary that allows the passage in or out of energy but not of matter

Front 4

Earth system

Back 4

atmosphere, hydrosphere,
biosphere, and the geosphere

Front 5

Evaporation

Back 5

The changing of a liquid into a gas, often under the influence of heat (as in the boiling of water)

Front 6

Geology

Back 6

the science of our planet

Front 7

Geosphere

Back 7

the solid portion of the Earth

Front 8

Hydrologic cycle

Back 8

the day-to-day and longterm cyclic changes in the hydropshere

Front 9

Hydrosphere

Back 9

totality of Earth's water, incl oceans, lakes, streams, water underground, and all the snow and ice, incl glaciers

Front 10

Igneous rock

Back 10

rock formed by the cooling and consolidation of magma

Front 11

Infiltration

Back 11

the movement of liquid water
downward from the land surface into and through the soil and rock

Front 12

Isolated system

Back 12

any system that has a boundary that prevents the passage in or out of energy and matter

Front 13

Metamorphic rock

Back 13

rock whose original compounds or textures, or both, have been transformed to new compounds and new textures by reactions in the solid state as a result of high temperature, high pressure or both

Front 14

Open system

Back 14

any system that has a boundary that allows the passage in or out of both energy and matter

Front 15

Precipitation

Back 15

the change of atmospheric water vapor to liquid (rain) or solid (snow).

Front 16

Rock cycle

Back 16

cyclic movement of rock material, in the course of which rock is created, destroyed, and altered through the operation of internal and external Earth processes

Front 17

Sedimentary rock

Back 17

any rock formed by chemical precipitation or by sedimentation and cementation of mineral grains transported to a site of deposition by water, wind, ice, or gravity

Front 18

System

Back 18

primary unit in a time-stratigraphic sequence of rocks

Front 19

Tectonic cycle

Back 19

model that describes the movement and interactions of lithospheric plates, the internal processes that drive plate motion, and the types of rock and rock formations that develop as a result of tectonic movement and interactions

Front 20

Transpiration

Back 20

the release of water into the atmosphere by plants and animal cells

Front 21

Accretion

Back 21

process by which solid bodies gather together to form a planet or a continent

Front 22

Differentiation

Back 22

process in which in a molten state, the Earth segregated into layers of different composition on the basis of density

Front 23

Crust

Back 23

outermost and thinnest of Earth's compositional layers, which consists of rocky matter that is less dense than the rocks of the mantle below

Front 24

Mantle

Back 24

thick shell of dense, rocky matter that surrounds the core

Front 25

Core

Back 25

spherical mass, largely metallic iron, at the center of the Earth

Front 26

Lithosphere

Back 26

outer 100 km of solid Earth, where rocks are harder and more rigid than those int he plastic asthenosphere

Front 27

Asthenosphere

Back 27

layer of the mantle where rocks are relatively ductile and are easily deformed, it lies at a depth of 100 to 350 km below the surface

Front 28

Mesosphere

Back 28

region between the base of the asthenosphere and the core-mantle boundary

Front 29

Inner core

Back 29

central, solid portion of Earth's core

Front 30

Outer core

Back 30

the outer portion of Earth's core, which is molten

Front 31

Oceanic crust

Back 31

crust under the ocean

Front 32

Convection

Back 32

process by which hot, less dense materials rise upward, being replaced by cold, more dense, downward-flowing material to create a convection current

Front 33

Isostasy

Back 33

ideal property of flotational balance among segments of the lithosphere

Front 34

P-waves

Back 34

seismic body waves transmitted by alternating pulses of compression and expansion; pass through solids, liquids, and gases

Front 35

S-waves

Back 35

seismic body waves transmitted by an alternating series of sideways (shear) movements in a solid. Cause a change of shape and cannot be transmitted through liquids and gases

Front 36

Banded iron formation

Back 36

are deep water deposits of alternating layers of iron-rich minerals and iron-poor layers

Front 37

Red beds

Back 37

are not found in rocks older than 2.3 billion years old because there was not sufficient oxygen to produce hematite until 2.3 billion years ago; are another type of iron-rich rock formation and are colored red because of the mineral
hematite (which forms in the process of oxidation of other iron materials)

Front 38

Continental crust

Back 38

part of the Earth's crust that comprises the continents, which has an average thickness of 45 km

Front 39

abyssal floor

Back 39

broad flat expanses of seafloor, 3 to 6 km deep. young oceanic plate grows dense and subsides as it cools, floors form after an oceanic plate has cooled enough for heat rising from the deep mantle to balance heat loss through the seafloor

Front 40

active margin

Back 40

a continental coastline that is coincident with a convergent plate boundary

Front 41

adiabatic expansion

Back 41

tendency of a substance to decrease in temp, without loss of heat to its surroundings, as it expands in response to decreasing pressure. conversely, a substance tends to experience an increase in temp, without a gain of heat from its surroundings, as it contracts in response to inc pressure

Front 42

brittle deformation

Back 42

any response of a substance to stress that involves internal breakage and the formation of fractures

Front 43

carbon cycle

Back 43

continuous transfer of the element carbon between different parts of the Earth system, mediated by photosynthesis, rainfall, rock weathering, secretion of calcium carbonate, sedimentation, subductions and volcanism

Front 44

collision zone

Back 44

a convergent plate margin where two plates collide

Front 45

continental drift

Back 45

the slow, lateral movements of continents across Earth's surface

Front 46

continental rise

Back 46

a region of gently changing slope where the floor of the ocean basin meets the margin of a continent

Front 47

continental shelf

Back 47

a submerged platform of variable width that forms a fringe around a continent

Front 48

continental slope

Back 48

pronounces slope beyond the seaward margin of the continental shelf

Front 49

convergent margin

Back 49

zone where plates met as they move toward each other, also subduction zone

Front 50

coronae

Back 50

ring like structural features on a planetary surface. Many coronae are found on venus

Front 51

divergent margin

Back 51

fracture in the lithosphere where two plates move apart also called a spreading center

Front 52

ductile deformation

Back 52

irreversible deformation induced in a solid that is stressed beyond its elastic limit but before rupture occurs

Front 53

elastic deformation

Back 53

reversible or nonpermanent deformation that occurs when an elastic solid is stretched and squeezed and the force is then removed

Front 54

fault

Back 54

fracture in a rock along which movement occurs

Front 55

friction

Back 55

slab friction which drags the top, the bottom, and the leading edge of descending lithosphere in the subduction zone, and plate friction, which drags elsewhere at the base of the plate

Front 56

geodesy

Back 56

science of measuring Earth's shape and its gravity, including small changes in position induced by deformation of Earth's interior

Front 57

geothermal gradient

Back 57

rate of increase of temperature downward in Earth

Front 58

Global Positioning System

Back 58

network of satellites whose orbits form a reference frame for precise determination of position on Earth

Front 59

heat conduction

Back 59

transport of heat through a substance, on a microscopic scale the heat energy moves via the exchange of kinetic energy between atoms and molecules

Front 60

heat convection

Back 60

occurs when the rocks actually start moving to transport their heat

Front 61

hot spot

Back 61

fixed point on the Earth's surface defined by long-lived volcanism

Front 62

Isostasy, principle of

Back 62

ideal property of flotational balance among segments of the lithosphere

Front 63

mantle convection

Back 63

of earth's mantle, driven both by the thermal buoyancy of hot rock rising from the depth and by sinking of cooler, denser lithosphere

Front 64

midocean ridge

Back 64

continuous rocky ridges on the ocean floor, many hundreds to a few thousand kilometers wide with a relief of more than .6 km, also called oceanic ridge and oceanic rise

Front 65

normal fault

Back 65

generally steeply inclined, along which the hanging-wall block has moved relatively downward

Front 66

passive margin

Back 66

a continental margin in a plate interior

Front 67

plate friction

Back 67

frictional resistance to lateral drift encountered by lithosphere at its bottom boundary with the underlying asthenosphere

Front 68

Rayleigh number

Back 68

ratio of physical factors that govern the transport of heat in a system, factors that tend to favor convection are divided by factors that discourage convection

Front 69

ridge push

Back 69

tendency for young oceanic lithosphere to slide laterally down the slope of a midocean ridge under the influence of gravity, thereby pushing the rest of the plate away from the ridge

Front 70

seamount

Back 70

isolated submerged volcanic mountain standing more than 1000m above the seafloor

Front 71

slab friction

Back 71

frictional resistance encountered by lithosphere as it sinks into Earth's interior

Front 72

slab pull

Back 72

tendency for sinking lithosphere at a convergent plate boundary to pull the rest of the plate laterally into the convergent zone

Front 73

spreading centers

Back 73

new growing edge of a plate, coincident with a midocean ridge

Front 74

strike-slip fault

Back 74

fault on which displacement has been horizontal and parallel to the strike of the fault

Front 75

subduction

Back 75

process by which old, cold lithosphere sinks into the asthenosphere

Front 76

subduction zone

Back 76

linear zone along which a plate of lithosphere sinks down into the asthenosphere

Front 77

thermal expansion

Back 77

tendency of a substance to expand as its temperature rises, and to contract as it cools

Front 78

thrust fault

Back 78

low angle reverse faults with dips less than 45

Front 79

transform fault margin

Back 79

fracture in the lithosphere along which two plates slide past each other

Front 80

trenches (oceanic)

Back 80

long, narrow, very deep, and arcuate basins in the seafloor

Front 81

scientific method

Back 81

the use of evidence that can be seen and tested by anyone who has the means to do so, consisting often of observation, formation of a hypothesis, testing of that hypothesis and formation of a law, and continued reexamination

Front 82

hypothesis

Back 82

an unproved explanation for the way things happen

Front 83

theory

Back 83

a hypothesis that has been examined and found to withstand numerous tests

Front 84

continental drift

Back 84

slow lateral movements of continents across Earth's surface

Front 85

seafloor spreading

Back 85

(theory of) lateral movement of the oceanic crust away from midocean ridges was postulated

Front 86

subduction

Back 86

process by which old, cold lithosphere sinks into the asthenosphere

Front 87

pangaea

Back 87

name given to a supercontinent that formed by collision of all the continental crust during the late paleozoic

Front 88

magnetic field

Back 88

magnetic lines of force surrounding Earth

Front 89

polarity

Back 89

the relative orientation of poles; the direction of a magnetic or electric field

Front 90

inclination

Back 90

the angle (dip) of the magnetic field lines with respect to the surface of the Earth and
varies from 0o (horizontal) at the magnetic equator to 90o (vertical) at the magnetic poles.

Front 91

magnetic reversal

Back 91

magnetic field flips direction

Front 92

normal polarity

Back 92

Rocks indicating a field direction the same
as today’s (magnetic north pole near the geographic North Pole)

Front 93

reversed polarity

Back 93

Rocks indicating the opposite field (magnetic north pole near the geographic South Pole)

Front 94

apparent polar wander

Back 94

apparent motions of the magnetic poles derived from measurements of pole positions using paleomagnetism

Front 95

true polar wander

Back 95

Although the magnetic pole
does move, it remains within a few degrees of the geographic pole because the magnetic field is
generated by the earth’s rotation.

Front 96

mid-ocean ridge

Back 96

continuous rocky ridges on the ocean floor, many hundreds to a few km wide with relief of more than .6 km (ocean ridge/oceanic rise)

Front 97

trench

Back 97

long, narrow, very deep, and arcuate (curved) basins in the seafloor

Front 98

subduction zone

Back 98

(convergent margin) linear zone along which a plate of lithosphere sinks down into the asthenosphere

Front 99

plate tectonics

Back 99

special branch of tectonics that deals with the processes by which the lithosphere is moved laterally over the asthenosphere

Front 100

plate

Back 100

The earth’s lithosphere is broken into about a dozen major pieces and numerous
smaller fragments

Front 101

divergent plate boundary

Back 101

where two plates pull away from each other and new oceanic crust is created; occurs at mid ocean ridges; assoc with extensional stress, shallow earthquakes, and basaltic volcanism

Front 102

continental rift valley

Back 102

the new divergent created where a continent is being pulled apart

Front 103

convergent plate boundary

Back 103

between two oceanic plates. The older, denser plate is subducted by the younger, more
buoyant plate. A trench marks the subduction zone at the surface. As the subducted plate descends into the mantle
and melts, rising magma creates a volcanic island arc.

Front 104

transform plate boundary

Back 104

where two plates are sliding past each other. The boundary is marked by a system of faults

Front 105

volcanic arc

Back 105

formed on the overriding plate above the depth where the subducted oceanic plates begin to melt and produce magma, which rises to the surface

Front 106

hot spot track

Back 106

a chain of volcanoes is produced as the plate moves over the stationary hot spot.

Front 107

tectonic setting

Back 107

describes the geologic environment of an area relative to any nearby plate boundaries
or hot spots.

Front 108

craton

Back 108

a core of ancient rock in the continental crust that has attained tectonic and isostatic stability

Front 109

orogen

Back 109

elongate regions of the crust that have been intensively folded, faulted, and thickened as a result of continental collisions

Front 110

continental shield

Back 110

assemblage of cratons and orogens that has reached isostatic equilibrium

Front 111

continental rifting

Back 111

process that occurs as plate motions tear continents apart

Front 112

passive margin

Back 112

a continental margin in a plate interior

Front 113

abyssal plain

Back 113

large flat area of the deep seafloor having slopes less than about 1 m/km and ranging in depth below sea level from 3 to 6 km

Front 114

continental slope

Back 114

pronounced slope beyond the seaward margin of the continental shelf

Front 115

continental shelf

Back 115

submerged platform of variable width that forms a fringe around a continent

Front 116

element

Back 116

most fundamental substances into which matter can be separated by chemical means

Front 117

atom

Back 117

smallest individual particle that retains the distinctive properties of a given chemical element

Front 118

nucleus

Back 118

assemblage of protons and neutrons in the core of an atom

Front 119

proton

Back 119

positively charged particle with a mass 1832 times greater than the mass of an electron

Front 120

neutron

Back 120

electrically neutral particle with a mass 1833 times greater than that of an electron

Front 121

electron

Back 121

negatively charged atomic particles

Front 122

orbital

Back 122

path that electrons follow with varying energy levels (shells)

Front 123

shell

Back 123

energy levels surrounding an atom

Front 124

atomic number

Back 124

number of protons in the nucleus of an atom

Front 125

atomic mass number

Back 125

the total number of protons and neutrons in an atom

Front 126

isotope

Back 126

atoms of an element having the same atomic number but differing mass numbers

Front 127

ion

Back 127

atom that has excess positive or negative charges caused by electron transfer

Front 128

cation

Back 128

a positive ion

Front 129

periodic table

Back 129

The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic number (number of protons in the nucleus), electron configurations, and recurring chemical properties.

Front 130

chemical compound

Back 130

form when atoms of different elements combine in a specific ratio

Front 131

molecule

Back 131

smallest unit that retains the distinctive properties of a compound

Front 132

ionic bond

Back 132

cations and anions are attracted to each other due to their opposite charges

Front 133

covalent bond

Back 133

atoms share electrons rather than transferring them, creating a strong bond

Front 134

metallic bond

Back 134

closely packed atoms share electrons in higher energy-level shells among several atoms

Front 135

Van der Waals bond

Back 135

weak secondary attraction between certain molecules formed by transferring electrons; much weaker than other bonds

Front 136

mineral

Back 136

any naturally formed, crystalline solid with a definite chemical composition and a characteristic crystal structure

Front 137

crystal structure

Back 137

the geometric pattern that atoms assume in a solid

Front 138

crystal habit

Back 138

characteristic crystal form or shape of each mineral

Front 139

polymorphism

Back 139

compound that occurs in more than one crystal structure

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luster

Back 140

quality and intensity of light reflected from a mineral

Front 141

streak

Back 141

thin layer of powdered mineral made by rubbing a specimen on a nonglazed porcelain plate

Front 142

cleavage

Back 142

tendency of a mineral to break in preferred directions along bright, reflective plane surfaces

Front 143

fracture

Back 143

irreversible deformation of a rock in which the limits of both elastic and ductile deformation have been exceeded

Front 144

conchoidal fracture

Back 144

breakage resulting in smooth, curved surfaces

Front 145

silicate

Back 145

a mineral that contains the silicate anion

Front 146

silicate ion

Back 146

siO4, makes up more than 70% of the continental crust with a four sided shape called a tetrahedron

Front 147

silicate tetrahedra

Back 147

that are not linked in any way; Olivine and garnet are examples of silicate minerals in which the crystal structures consist of isolated silicate tetrahedra

Front 148

chain

Back 148

two silicate tetrahedra sharing an oxygen atom produces a chain

Front 149

sheet

Back 149

include the group of minerals called micas; display perfect cleavage in one direction

Front 150

framework

Back 150

every oxygen atom in a silicate tetrahedra is shared with another silicate tetrahedra, linking the tetrahedra in a complex 3d network; exam is feldspar group and quartz

Front 151

carbonate

Back 151

anion (CO3)2- forms calcite, aragonite, and dolomite

Front 152

oxide

Back 152

iron oxides, magnetite (Fe3O4) and hematite (Fe2O3) are two most common, most important economically because used to make steel

Front 153

sulfide

Back 153

group of minerals containing sulfur; also economically important; incl copper, lead, cobalt, mercury, and silver

Front 154

halide

Back 154

principle anions are halogens (need one electron to have a full outer shell and so form anions with a negative one charge by gaining an electron); soft, transparent, not very dense, good cleavage, and bright colors

Front 155

magma

Back 155

molten rock, together with any suspended mineral grains and dissolved gases, that forms when temp rise and melting occurs in the mantle or crust

Front 156

lava

Back 156

magma that reaches earths surface through a volcanic vent

Front 157

decompression melting

Back 157

lowering the pressure at which melting occurs; occurs when mantle material migrates upwards to areas of lower pressure; common at divergent plate boundaries and hot spots

Front 158

basaltic magma

Back 158

contains about 50% SiO2 by weight; low in Na, K but high in Fe, Mg, and Ca

Front 159

andesitic

Back 159

has intermediate silica content (55-65%) and intermediate amounts of Fe, Mg, Ca, Na, and K

Front 160

rhyolitic

Back 160

high silica content (65-75%), high in Na, K and low in Fe, Mg, and Ca

Front 161

partial melting

Back 161

The process of forming magma through the incomplete melting of rock

Front 162

fractional crystallization

Back 162

crystallizing minerals are separated from the residual magma during cooling changing the magma composition

Front 163

Bowen's reaction series

Back 163

a schematic description of the order in which different minerals crystallize during the cooling and progressive crystallization of a magma

Front 164

felsic

Back 164

high in silica Na, K, and Al; a group of light-colored minerals including feldspar, feldspathoids, quartz, and muscovite; rhyolitic magma

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mafic

Back 165

rich in Fe and Mg, low in SiO2; basaltic magma

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contamination

Back 166

occurs as rising magma assimilates surrounding rock

Front 167

magma mixing

Back 167

heat from rising magma melts surrounding rock creating another form of magma that can mix with the contaminated magma forming a new composition

Front 168

batholith

Back 168

largest kind of pluton; very large igneous body of irregular shape that cuts across the layering of the rock it intrudes

Front 169

dike

Back 169

tabular, parallel-sided sheets of intrusive igneous rock that cut across the layering of the intruded rock

Front 170

laccolith

Back 170

lenticular pluton introduced parallel to the layering of the surrounding rock, above which the layers of the invaded country rock have been bent upward to form a dome

Front 171

pluton

Back 171

any body of intrusive igneous rock, regardless of shape or size

Front 172

sill

Back 172

tabular, parallel-sided sheets of intrusive igneous rock that are parallel to the layering of the intruded rock

Front 173

stock

Back 173

small irregular-shaped intrusions no larger than 10 km in maximum dimension

Front 174

xenolith

Back 174

any rock fragment still enclosed in a magmatic body when it solidifies; produced from rising magma dislodging fragments of the overlying rock and since they are cooler they sink through the magma

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composition

Back 175

proportions of the various chemical elements in a mineral

Front 176

texture

Back 176

overall appearance that a rock has because of the size, shape, and arrangement of its constituent mineral grains

Front 177

intrusive

Back 177

any igneous rock formed by solidification of magma below Earth's surface; large crystals; coarse grained

Front 178

extrusive

Back 178

rock formed by the solidification of magma poured out onto Earth's surface; small crystals; fine grained

Front 179

phaneritic

Back 179

igneous rock in which the constituent mineral grains are readily visible to the unaided eye

Front 180

apahnitic

Back 180

igneous rock in which the constituent mineral grains are so small they can only be seen clearly by suing some kind of magnification

Front 181

porphyritic

Back 181

igneous rock consisting of coarse mineral grains scattered through a mixture of fine mineral grains

Front 182

phenocryst

Back 182

isolated large mineral grains in a porphyry

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vesicular

Back 183

small opening in extrusive igneous rock, made by escaping gas originally held in solution under high pressure while the parent magma was underground

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pyroclastic

Back 184

fragment of rock ejected during a volcanic eruption

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tephra

Back 185

loose assemblage of pyroclasts

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tuff

Back 186

pyroclastic rock consisting of ash or lapilli-sized tephra, hens ash tuff and lapilli tuff

Front 187

vitreous

Back 187

all igneous rocks with this texture are obsidian; formed by very rapid cooling on the surface; no crystal structure because atoms lack time to organize themselves into minerals

Front 188

granite

Back 188

coare grained igneous rock containing quartz and feldspar, with potassium feldspar being more abundant than plagioclase (a form of feldspar consisting of aluminosilicates of sodium and/or calcium, common in igneous rocks and typically white)

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diorite

Back 189

coarse grained igneous rock consisting mainly of plagioclase and ferromagnesian (containing iron and magnesium as major components) minerals; quartz is sparse or absent

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gabbro

Back 190

coarse grained igneous rock in which olivine and pyroxene are the predominant minerals and plagioclase is the feldspar present; quartz is absent

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periodotite

Back 191

coarse grained igenous rock consisting largely of olivine, with or without pyroxene

Front 192

rhyolite

Back 192

fine-grained extrusive igneous rock with the composition of a granite

Front 193

andesite

Back 193

fine-grained igneous rock with the composition of a diorite

Front 194

basalt

Back 194

fine grained igneous rock with the composition of a gabbro (coarse grained igneous rock in which olivine and pyroxene are the predominant minerals and plagioclase is the feldspar present; quartz is absent)

Front 195

komatite

Back 195

extrusive equivalent of peridotite; rare; all known are older than 2 billion years indicating that the processes responsible for eruption of ultramafic magmas at the surface no longer occur on Earth

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obsidian

Back 196

extrusive igneous rock that is wholly or largely glass

Front 197

pumice

Back 197

natural glassy froth made by gases escaping through a viscous magma

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felsic

Back 198

high in silica Na, K, and Al; a group of light-colored minerals including feldspar, feldspathoids, quartz, and muscovite; rhyolitic magma

Front 199

intermediate

Back 199

andesitic igneous rocks are produced by melting water rich subducted oceanic crust

Front 200

mafic

Back 200

rich in Fe and Mg, low in SiO2; basaltic magma

Front 201

ultramafic

Back 201

relating to or denoting igneous rocks composed chiefly of mafic minerals; kimberlite is an extrusive ultramafic rock that originates from material at great depths and high pressures

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viscosity

Back 202

internal property of a substance that offers resistance to flow

Front 203

pahoehoe

Back 203

smooth ropy surfaced lava flow, usually basaltic in composition

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Aa

Back 204

rubbly, rough-looking form of lava, usually basaltic in composition

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effusive

Back 205

(of igneous rock) poured out when molten and later solidified; from higher temp, lower viscosity magma that has lower gas contents so produces gentler eruptions

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explosive

Back 206

lower temp, high viscosity magmas tend to have higher gas contents and violent eruptions

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shield volcano

Back 207

that emits fluid lava and builds up a broad dome-shaped edifice with a surface slope of only a few degrees

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cinder cone

Back 208

steep conical hill created from gases accumulating at the top of a magma chamber prior to eruption and when it erupts it is a frothy ejection of material; the cone forms from pyroclastic (hot rock) fragments accumulating around and downwind of the vent; have a glassy texture; produced from basaltic magma

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composite volcano

Back 209

composed of alternating layers of lava flows and pyroclastic deposits; steep sides, conical shape, only found at subduction zones; erupt andesitic magma; periods of explosive activity (stratovolcano)

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stratovolcano

Back 210

emits both tephra and viscous lava and that builds up steep conical mounds; andesitic magma (composite volcano)

Front 211

dome volcano

Back 211

steep sided; high viscosity; produced from rhyolitic and dacite magmas

Front 212

lava dome

Back 212

dome-shaped mass of sticky, gas-poor lava erupted from a volcanic vent following a major eruption

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vent

Back 213

opening through which lava reaches the surface

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fissure

Back 214

rifts where weaknesses in the crust provide a path for molten rock to reach the surface; largest system is mid-ocean ridge

Front 215

flood basalt

Back 215

regional fissure systems that feed voluminous outpourings of basalts; cover large areas of the ocean floor

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caldera

Back 216

roughly, circular steep-walled volcanic basin several kilometers or more in diameter

Front 217

pillow basalt

Back 217

discontinuous pillow-shaped masses of basalt, ranging in size from few cm to a m or more in greatest dimension

Front 218

pyroclastic flow

Back 218

high-density mixtures of hot, dry rock fragments and hot gases that move away from the vent that erupted them at high speeds; 2 parts - basal flow of coarse fragements and turbulent cloud of ash

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tephra

Back 219

general term for fragments of volcanic rock and lava regardless of size that are blasted into the air by explosions or carried upward by hot gases in eruption columns or lava fountains

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plinian eruption

Back 220

very explosive style characteristic of larger eruptions or composite volcanoes

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lava flow

Back 221

effusive eruptions of magma from a vent or fissure

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pahoehoe

Back 222

higher temp, lower viscosity, smooth ropy surface texture

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Aa

Back 223

lower temp, higher viscosity, blocky surface texture

Front 224

accreted terranes

Back 224

small pieces of crust too buoyant to be subducted that are carried along by oceanic plates and added to the edge of a continent

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Weathering

Back 225

chemical alteration and mechanical breakdown of rock materials during exposure to air, moisture, and organic matter

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Erosion

Back 226

complex group of related processes by which rock is broken down physically and chemically and the products are moved

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Physical weathering

Back 227

spalling off of successive shells around a solid rock core

Front 228

frost wedging

Back 228

decomposition of rocks through chemical reactions such as hydration and oxidation

Front 229

exfoliation

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irregular blanket of loose, noncemented rock particles that covers Earth's surface

Front 230

chemical weathering

Back 230

regolith that has been transported by any of the external processes

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regolith

Back 231

parent material from whcih the sediment was derived (granite, basalt, etc) as indicated by mineralogy

Front 232

sediment

Back 232

regolith that has been transported by any of the external processes

Front 233

provenance

Back 233

of clastic sediment refers to the parent material from which the sediment was derived (granite, basalt, etc) as indicated by mineralogy

Front 234

clastic

Back 234

loose fragmented debris produced by the mechanical breakdown of older rocks

Front 235

chemical sediment

Back 235

water-soluble products of chemical weathering carried as dissolved ions in chemical solution

Front 236

biogenic sediment

Back 236

consists of dead remains of plants and animals

Front 237

deposition

Back 237

occurs when the transporting agent is no longer capable of moving the sediment

Front 238

precipitation

Back 238

opposite of dissolution; occurs by inc concentration of dissolved materials by evaporating some of the water, changing ambient conditions, or by biological processes

Front 239

sedimentary structures

Back 239

provide clues to the type of environment the sediment was deposited in

Front 240

stratification

Back 240

layered arrangements of sediments, sedimentary rocks, or extrusive igneous rocks

Front 241

strata

Back 241

distinct layer of sediment that accumulated at Earth's surface

Front 242

bedding

Back 242

layered arrangement of strata in a body of sediment or sedimentary rock

Front 243

cross-bedding

Back 243

beds that are inclined with respect to a thicker stratum within which they occur

Front 244

graded bedding

Back 244

develops where a transporting agent loses velocity; coarser particles deposited first then finer particles as agent slows

Front 245

lithification

Back 245

process that converts a sediment into a sedimentary rock

Front 246

compaction

Back 246

decrease in porosity and bulk of a body of sediment as additional sediment is deposited above it, or due to pressures resulting from deformation

Front 247

cementation

Back 247

diagenetic process by which clastic sediments are converted to rock through deposition or precipitation of minerals in the spaces between the grains

Front 248

recyrstallization

Back 248

formation of new crystalline minerals within a rock

Front 249

shale

Back 249

fine grained, clastic sedimentary rock

Front 250

siltstone

Back 250

sedimentary rock composed of mainly silt-sized mineral fragments

Front 251

sandstone

Back 251

medium-grained clastic sedimentary rock composed chiefly of sandsized grains

Front 252

conglomerate

Back 252

sedimentary rock composed of clasts of rounded gravel set in a finer grained matrix

Front 253

breccia

Back 253

coarse-grained rock composed of cemented angular fragments

Front 254

limestone

Back 254

sedimentary rock consisting chiefly of calcium carbonate, mainly in the form of the mineral calcite

Front 255

chert

Back 255

hard, compact sedimentary rock composed almost entirely of very fine-grained, interlocking quartz crystals that occurs as extensive continuous layers or as nodules in carbonate rocks

Front 256

evaporite

Back 256

sedimentary rock composed of minerals precipitated from a saline solution through evaporation

Front 257

coal

Back 257

black combustible sedimentary or metamorphic rock consisting of decomposed plant matter and containing more than 50% organic matter

Front 258

fossil

Back 258

naturally preserved remains or traces of an animal or plant

Front 259

depositional environment

Back 259

where sedimentary rocks formed

Front 260

alluvial fans

Back 260

stream deposits from fast-flowing water

Front 261

meandering stream

Back 261

loop-like bend of a stream

Front 262

braided stream

Back 262

channel system consisting of a tangled network of two or more smaller branching and reuniting channels that are separated by island or bars

Front 263

aeolian deposits

Back 263

sediment transported and deposited by wind

Front 264

till

Back 264

nonsorted sediment deposited directly from a glacier ice

Front 265

lacustrine

Back 265

pertaining to, produced by, or formed in a lake

Front 266

delta

Back 266

body of sediment deposited by a stream where it flows into standing water

Front 267

beach

Back 267

wave-washed sediment along a coast, extending through the surf zone

Front 268

reef

Back 268

generally ridge-like structure composed of calcareous remains of sedentary marine organisms IE limestone

Front 269

turbidite

Back 269

graded layer of sediment deposited by a turbidity current

Front 270

metamorphic rocks

Back 270

rock whose original compounds or textures have been transformed to new compounds and new textures by reactions in the solid state as a result of high temp, pressure or both

Front 271

metamorphism

Back 271

all changes in mineral assemblage and rock texture that take place in sedimentary and igenous rocks in the solid state within the earth's crusta as a result of changes in temp and pressure

Front 272

foliation

Back 272

planar texture of mineral grains, principally micas, produced by metamorphism

Front 273

protolith

Back 273

parent rock

Front 274

metamorphic facies

Back 274

contrasting assemblages of minerals that reach equilibrium during metamorphism within a specific range of physical conditions belonging to the same metamorphic facies

Front 275

metamorphic grade

Back 275

temperature and pressure

Front 276

slate

Back 276

low-grade metamorphic rock with a pronounced slaty-cleavage

Front 277

phyllite

Back 277

well-foliated metamorphic rock in which the component platy minerals are just visible

Front 278

schist

Back 278

well-foliated metamorphic rock in which the component platy minerals are clearly visible

Front 279

gneiss

Back 279

high-grade metamorphic rock always course-grained and foliated, with marked compositional layering but with imperfect cleavage

Front 280

quartzite

Back 280

metamorphic rock consisting largely of quartz, and derived from a sandstone

Front 281

marble

Back 281

metamorphic rock derived from limestone and consisting largely of calcite

Front 282

blueschist

Back 282

metamorphic rock formed under conditions of high pressure and low temp containing blue-colored amphiboles

Front 283

eclogite

Back 283

metamorphic rock containing garnet and jadeitic pyroxene

Front 284

greenschist

Back 284

low-grade metamorphic rock rich in chlorite

Front 285

amphibolite

Back 285

metamorphic rock of intermediate grade, generally coarse-grained, containing abundant amphibole

Front 286

granulite

Back 286

high-grade metamorphic rock usually coarse-grained and indistinctly foliated, containing pyroxenes as a major mineral

Front 287

low-grade metamorphism

Back 287

under conditions of low temp and pressure

Front 288

high-grade metamorphism

Back 288

under conditions of high temp and pressure

Front 289

slatey cleavage

Back 289

property by which a rock breaks into platelike fragments along flat planes

Front 290

schistosity

Back 290

parallel arrangement of coarse grains of the sheet-structure minerals, like mica and chlorite formed during metamorphism under conditions of differential stress

Front 291

gneissic banding

Back 291

at higher pressure and temp micas (hydrous minerals) are replaced by anhydrous minerals (amphibles and pyroxenes) which become segregated into mafic and felsic domains; develops because most dark minerals have elongate/platy habits and continue to get crowded out by blocky quartz and feldspar crystals which do not have preferred organization

Front 292

thermal metamorphism

Back 292

metamorphism adjacent to an intrusive igneous rock

Front 293

hornfels

Back 293

hard, fine-grained rock developed during contact metamorphism of a shale

Front 294

geothermometry

Back 294

using minerals to estimate the temp of metamorphism

Front 295

geobarometry

Back 295

using minerals to estimate the pressure of metamorphism

Front 296

geothermal gradient

Back 296

rate of increase of temp downward in Earth

Front 297

cataclastic metamorphism

Back 297

involves change of texture caused by mechanical effects such as crushing and shearing but no change in mineral assemblage

Front 298

burial metamorphism

Back 298

caused solely by the burial of sedimentary or pyroclastic rocks

Front 299

contact metamorphism

Back 299

aka thermal; adjacent to an intrusive igneous rock

Front 300

metamorphic aureole

Back 300

shell of metamorphic rock, produced by contact metamorphism, surrounding an igneous intrusion

Front 301

regional metamorphism

Back 301

affecting large volumes of crust and involving both mechanical and chemical changes

Front 302

index minerals

Back 302

mineral whose first appearance marks the outer limits of a specific zone of metamorphism

Front 303

orogeny

Back 303

process by which large regions oft he crust are deformed and uplifted to form mountains

Front 304

stress

Back 304

magnitude and direction of a deforming force exerted on a surface

Front 305

uniform stress

Back 305

equal in all directions aka confining or homogeneous stress

Front 306

differential stress

Back 306

in a solid that is not equal in all directions

Front 307

confining stress

Back 307

uniform stress; equal on all sides

Front 308

compressional stress

Back 308

differential stress that squeezes and compresses a body

Front 309

tensional stress

Back 309

differential stress on a body that causes stretching and elongation

Front 310

shear stress

Back 310

force acting on a body that causes slippage or translation

Front 311

strain

Back 311

measure of changes in length, volume, and shape in a stressed material

Front 312

deformation

Back 312

change in size, shape, or orientation of rocks that were once in orderly horizontal layers

Front 313

elastic deformation

Back 313

reversible deformation that occurs when an elastic solid is stretched and squeezed and the force is then removed

Front 314

recoverable strain

Back 314

when stress is removed, rock returns to its original size and shape

Front 315

elastic limit

Back 315

limiting stress beyond which a body suffers irreversible deformation

Front 316

ductile deformation

Back 316

irreversible deformation induced in a solid that is stressed beyond its elastic limit but before rupture occurs

Front 317

permanent

Back 317

deformation beyond the elastic limit

Front 318

fracture

Back 318

irreversible deformation of a rock in which the limits of both elastic and ductile deformation have been exceeded; breakage

Front 319

brittle material

Back 319

small region of ductile behavior before they fracture; low temp and low confining pressure with a high strain rate

Front 320

ductile material

Back 320

large region of ductile behavior before they fracture; deforms by a change in shape; material is more ductile with high confining pressure and low strain rate

Front 321

strain rate

Back 321

rate at which a rock is forced to change its shape or volume

Front 322

outcrop

Back 322

aka exposure; place where rock or sediment is exposed at Earth's surface

Front 323

strike

Back 323

compass direction of a horizontal line that marks the intersection of an inclined plane with Earth's surface

Front 324

dip

Back 324

angle in degrees between a horizontal plane and an inclined plane, measured down from horizontal in a plane perpendicular to the strike

Front 325

fold

Back 325

individual bend or warp in layered rock

Front 326

monocline

Back 326

local steepening in an otherwise uniformly dipping pile of strata

Front 327

anticline

Back 327

upfold in the form of an arch

Front 328

syncline

Back 328

downfold with a troughlike form

Front 329

open fold

Back 329

in which two limbs dip gently and equally, and away from the axis

Front 330

closed fold

Back 330

paired anticlines and synclines in ductile strata; produced by shearing forces that create strike-slip faults

Front 331

dome

Back 331

circular anticline with the oldest rocks in the center

Front 332

basin

Back 332

circular syncline with youngest rocks in the center

Front 333

joint

Back 333

fractures in a rock on which no observable movement has occurred

Front 334

axis

Back 334

(of a fold) median lien between the limbs, along the crest of an anticline or the trough of a syncline

Front 335

limbs

Back 335

(of a fold) sides of a fold

Front 336

trend

Back 336

compass direction of the fold axis

Front 337

plunge

Back 337

angle between a fold axis and the horizontal

Front 338

plunging fold

Back 338

fold with an inclined axis

Front 339

fault

Back 339

fracture in a rock along which movement occurs

Front 340

hanging-wall block

Back 340

block of rock above an inclined fault

Front 341

footwall block

Back 341

block of rock below an inclined fault

Front 342

dip-slip fault

Back 342

normal or reverse fault on which the only component of movement lies in a plane normal tot he strike of the fault surface

Front 343

strike-slip fault

Back 343

fault on which displacement has been horizontal and parallel to the strike of the fault

Front 344

normal faults

Back 344

generally steeply inclined, along which the hanging-wall block has moved relatively downward

Front 345

reverse fault

Back 345

generally steeply inclined, along which the hanging-wall block has moved relatively upward

Front 346

thrust fault

Back 346

low angle reverse faults with dips less than 45 degrees

Front 347

left-lateral fault

Back 347

strike-slip fault in which relative motion is such that to an observer looking directly at the fault, the motion of the block on the opposite side of the fault is to the left

Front 348

right-lateral fault

Back 348

strike-slip fault in which relative motion is such that to an observer looking directly at the fault, the motion of the block on the opposite side is to the right

Front 349

graben

Back 349

trench-like structure bounded by parallel normal faults

Front 350

horst

Back 350

elevated elongate block of crust bounded by parallel normal faults

Front 351

Earthquake

Back 351

violent ground-shaking caused by sudden release of strain energy stored in rocks

Front 352

earthquake magnitude

Back 352

amount of energy released by the earthquake

Front 353

frequency

Back 353

how often an earthquake occurs

Front 354

intraplate earthquake

Back 354

earthquakes that occur far from active plate boundaries; areas of weak lithosphere stretched by failed rifts

Front 355

fault

Back 355

fracture in a rock along which movement occurs

Front 356

stress

Back 356

the magnitude and direction of a deforming force exerted on a surface

Front 357

strain

Back 357

deformation such as change in their size, shape, or orientation

Front 358

rupture

Back 358

break caused by amount of strain along the fault exceeding the strength of the rocks

Front 359

seismic waves

Back 359

elastic disturbances spreading outward from an earthquake focus

Front 360

elastic rebound theory

Back 360

that earthquakes result from the release of stored elastic energy by slippage on faults

Front 361

displacement

Back 361

replaces strain after the earthquake; offset of rocks along the fault

Front 362

focus

Back 362

site of first movement along the fault where rupture of rock begins

Front 363

epicenter

Back 363

that point on Earth's surface that lies vertically above the focus of an earthquake

Front 364

body waves

Back 364

seismic waves that travel outward from an earthquake focus and pass deeply through Earth's interior

Front 365

P-waves

Back 365

seismic body waves transmitted by alternating pulses of compression and expansion; passes through solids, liquids, and gases

Front 366

S-waves

Back 366

seismic body waves transmitted by an alternating series of sideways (shear) movements in a solid; cause a change of shape and cannot be transmitted through liquid or gases

Front 367

surface waves

Back 367

guided by the Earth's waves and do not pass through the body of the Earth

Front 368

seismograph

Back 368

instrument that measures and records vibrational motions caused by earthquakes, explosions and similar disturbances

Front 369

Richter magnitude

Back 369

a scale, based on the recorded amplitudes of seismic waves, for comparing the amounts of energy released by earthquakes

Front 370

logarithmic scale

Back 370

an increase of 1 is a tenfold increase in magnitude

Front 371

moment magnitude

Back 371

true measure of the energy released by an earthquake and is based on the geophysical measurements of the amount of displacement along the fault, the strength of the rocks that ruptured, and the area of the fault that ruptured

Front 372

earthquake intensity

Back 372

measure of effects of an earthquake and is based on ground observations incl people's perceptions and reactions to the earthquake and the damage caused by it

Front 373

material amplification

Back 373

intensity of ground shaking is more severe in less dense or unconsolidated materials such as mud and other sediments than in solid bedrock

Front 374

earthquake forecasting

Back 374

est the long-term likelihood of a damaging earthquake in a particular region, in order to develop cost-effective building codes and emergency-response plans

Front 375

earthquake prediction

Back 375

est the short-term likelihood of a damaging earthquake in a particular region, in order to warn local authorities and thereby minimize casualties and property damage

Front 376

liquefaction

Back 376

sudden loss of cohesion in water-saturated material from shaking

Front 377

tsunami

Back 377

impulsively generated seismic sea waves produced by abrupt vertical displacement of ocean water due to sudden movement of the seafloor

Front 378

seismic gaps

Back 378

sections of a fault where no earthquakes have occurred recently, but it is known that elastic strain is building in the rocks

Front 379

subduction zone earthquake

Back 379

can generate a tsunami

Front 380

deep intraplate earthquake

Back 380

occurring at depths below 18 miles on fractures in the subducting plate

Front 381

shallow crustal earthquake

Back 381

less than 7.5 M result from movement in the crust

Front 382

turbidite

Back 382

debris flows

Front 383

stratigraphy

Back 383

study of sequence and age of rock strata or layers

Front 384

lateral continuity

Back 384

fact that sediments are deposited in layers that are often continuous across broad regions

Front 385

original horizontality

Back 385

sediments are initially deposited in horizontal layers

Front 386

superposition

Back 386

sedimentary rock layers are deposited in order rom the bottom (oldest) to the top (youngest)

Front 387

cross-cutting relationships

Back 387

igneous intrusions or faults must be younger than the rocks they intrude or offset because the host rock must be there first in order to be intruded or offset

Front 388

unconformity

Back 388

gaps in the stratigraphic record representing periods of time in which sediments were either not deposited or have been eroded

Front 389

disconformity

Back 389

ancient erosional surface between parallel strata; recognized by an irregular contact between adjacent strata and sometimes weathered fragments of the lower strata inc within the upper strata

Front 390

angular unconformity

Back 390

horizontal strata overly tilted strata; contact between tilted strata and strata still in their original horizontal position represents a period of time in which the older strata were uplifted, disturbed by tectonic uplift, and beveled by erosion before additional sediments were deposited

Front 391

nonconformity

Back 391

sedimentary strata is directly over igneous or metamorphic rocks; must be a gap of time between igneous activity or metamorphism

Front 392

stratigraphic section

Back 392

sequence of rocks

Front 393

fossil succession

Back 393

observation that different types of plants and animals are found in rocks of different ages

Front 394

index fossil

Back 394

certain types of fossils are widely distributed spatially but restricted in age; well define, and often short, age range

Front 395

range fossil

Back 395

similarly well defined age range of existence as an index fossil but for a much longer time

Front 396

relative age

Back 396

places events in chronological order

Front 397

absolute age

Back 397

numerical ages in years determined using the principles of radioactive decay; assigns dates to ages

Front 398

half-life

Back 398

specific rate of decay of an isotope; time req for half of the atoms to decay

Front 399

geologic time scale

Back 399

divides Earth history into eons, eras, periods, and epochs on the basis of major geologic events, similar rock types and similar types of fossils; uses relative and absolute age-dating techniques

Front 400

eon

Back 400

largest interval into which geologic time is divided; Hadean (no rocks on earth here), Archean, and Proterozoic, and Phanerozoic Eon

Front 401

era

Back 401

shorter time units of the Phanerozoic eon; paleozoic, mesozoic, and cenozoic

Front 402

period

Back 402

subdivisions of eras based on fossil record

Front 403

epoch

Back 403

shortest subunit of geologic time but still span millions of years

Front 404

correlation

Back 404

uses similarities between geologic units to extend info about geologic sequences over large geographic areas; involves determining the relative ages of units exposed within a local area being studied and est the ages of the local rock units relative to a standard scale of geologic time

Front 405

radioactive decay

Back 405

if the ration of the number of neutrons to the number of protons is too high or too low, the atomic nucleus of a radioactive isotope will transform spontaneously to a nucleus of a more stable isotope of a different chemical element

Front 406

prokaryotes

Back 406

single cells with anarobic metabolism and no cell nucleus because the early atmosphere contained no free oxygen

Front 407

anaerobic metabolism

Back 407

organisms used this process (fermentation) to derive energy before the environment became oxygenated

Front 408

banded iron formations

Back 408

areas of extensive sedimentary marine rocks rich in iron oxide deposited during the early Proterozoic Eon which began 2.5 bya

Front 409

eukaryotes

Back 409

formed after the environment became oxygenated; have specialized organelles such as a cell nucleus and more efficient aerobic metabolism evolved 1.4 bya

Front 410

aerobic metabolism

Back 410

evolutionary advantage over anaerobic metabolism because the oxidation of organic matter by respiration releases more energy than anaerobic fermentation

Front 411

greenhouse effect

Back 411

is the trapping of heat energy in the atmosphere by certain gases such as water vapor and carbon dioxide

Front 412

snowball earth hypothesis

Back 412

many lines of evidence support a theory that the entire Earth was ice-covered for long periods in the late proterozioc esp 600-700 mya

Front 413

edicarian fauna

Back 413

first multi-celled animals after the snowball earth; jelly-like creatures with no hard parts 600 million years ago

Front 414

cambrian explosion

Back 414

huge increase in diversity of marine invertebrates, inc 9 phyla that still exist today and marks the beg of the cambrian period of the paleozoic era

Front 415

chordates

Back 415

animals with a spinal cord from which all vertebrate descend; arrived in the cambrian

Front 416

arthropods

Back 416

first land creatures; appeared in Cambrian seas and colonized the land during the Silurian period; invertebrate animals with jointed legs such as crabs, spiders, insects, and trilobites

Front 417

gymnosperms

Back 417

first plants with seeds to develop inc gingkoes and conifers

Front 418

lobe-finned fishes

Back 418

the first fish to venture on land; appeared in the devonian period; fins evolved into legs and gave rise to the first amphibians

Front 419

paleography

Back 419

understanding the past positions of the continents; reconstructed from rock records using 3 lines of evidence

Front 420

gondwanaland

Back 420

southern supercontinent; set the stage for the next glacial period in Earth's history

Front 421

carboniferous

Back 421

mississippian period; the northern continents were being assembled into another supercontinent called Euramerica

Front 422

pangaea

Back 422

the mother of all supercontinents; collision of Euramerica and Gondwanaland; created central pangaea mnt range; remnants are the appalachians and urals which have continued coal production

Front 423

amniotic egg

Back 423

hard-shelled eggs

Front 424

archosaurs

Back 424

ruling reptiles; came from the triassic period and are distinguished by legs undernearth their bodies rather than to their sides incl dinosaurs, marine reptiles, and flying reptiles; today birds still exist from this group

Front 425

mass extinctions

Back 425

entire groups of plants and animals die out

Front 426

angiosperms

Back 426

flowering plants that rely on insects for pollination by offering food

Front 427

K/T extinction

Back 427

most famous extinction which marks the end of the mesozoic era; extinction of dinosaurs, marine reptiles, flying reptiles, and 50% of marine invertebrate genera; may have been caused by extra-terrestrial impact