Geology Final Exam

Front 1

Plate Tectonic motions result in large horizontal forces called ______ ______

Back 1

tectonic forces

Front 2

Force per unit area

Back 2

stress

Front 3

3 types of stress:

Back 3

compressional, tensional, shear

Front 4

Stress where plates are squeezing together

Back 4

compressional

Front 5

Stress where plates are pulling apart

Back 5

tensional

Front 6

Stress where plates are sliding past each other

Back 6

shear

Front 7

Non-permanent deformation, rock returns to pre-stressed state once stress is removed

Back 7

elastic deformation

Front 8

Rocks can only deform elastically until they reach their _______ _______

Back 8

elastic limit

Front 9

Deformation involving breaking of the rock (joints and faults)

Back 9

brittle deformation

Front 10

Deformation in which the rock deforms plastically (folds)

Back 10

ductile deformation

Front 11

Rapid strain rates tend to result in ______ deformation

Back 11

brittle

Front 12

Slower strain rates can result in ______ deformation

Back 12

ductile

Front 13

Warmer temperatures can lead to more ________ deformation

Back 13

ductile

Front 14

Transform boundaries produce ________ faults

Back 14

strike-slip

Front 15

Convergent boundaries produce ________ faults

Back 15

reverse faults

Front 16

Divergent boundaries yield ________ faults

Back 16

normal

Front 17

A major right-lateral strike-slip fault system that makes up transform boundary between Pacific and North American plates

Back 17

San Andreas fault

Front 18

_______ is the azimuth of a horizontal line in a plane

Back 18

strike

Front 19

_______ is measured at 90 degrees to strike

Back 19

dip

Front 20

A planar surface containing containing the hinge lines for each layer of the fold

Back 20

axial plane

Front 21

The point of maximum curvature of the fold.

Back 21

hinge

Front 22

The sides of the fold

Back 22

limbs

Front 23

Upward arching folds with older rocks near the core of the fold

Back 23

anticlines

Front 24

Downward arching folds with younger rocks near the core of the fold

Back 24

synclines

Front 25

Circular upwarped structures

Back 25

domes

Front 26

Circular downward structures

Back 26

basins

Front 27

Fractures across which there has been little displacement

Back 27

joints

Front 28

Fractures across which there has been displacement

Back 28

faults

Front 29

Slip in the direction of dip

Back 29

dip-slip

Front 30

The block above the fault

Back 30

hanging wall

Front 31

The block below the fault plane

Back 31

footwall

Front 32

Faults where the hanging wall moves down relative to the footwall

Back 32

normal faults

Front 33

Faults where the hanging wall moves up relative to the footwall

Back 33

reverse faults

Front 34

Low angle reverse faults

Back 34

thrust faults

Front 35

Slip in the direction of strike; slip is mostly horizontal

Back 35

strike-slip

Front 36

Relative motion between blocks moves fault block on the opposite side of the fault either to the right or left

Back 36

right or left-lateral

Front 37

Components of both dip-slip and strike-slip motion

Back 37

oblique-slip

Front 38

Cause of earthquakes

Back 38

sudden release of energy accumulated in deformed rock

Front 39

Stresses along plate boundaries from plate motion

Back 39

tectonic stress

Front 40

Rock deforms elastically in response to stress

Back 40

strain accumulation

Front 41

Slip along fault releases energy from strain accumulation

Back 41

rupture during earthquake

Front 42

Point within the earth where rupture occurs

Back 42

focus or hypocenter

Front 43

Point on Earth's surface directly above the focus

Back 43

epicenter

Front 44

2 types of waves

Back 44

body waves, surface waves

Front 45

Waves that travel through earth's interior

Back 45

body waves

Front 46

2 types of seismic waves

Back 46

p waves and s waves

Front 47

Fastest body waves, arrive first at seismic stations, travel through solids and fluids

Back 47

P waves (primary, compressional)

Front 48

Slower body waves, arrive second at seismic stations, only travel through solids

Back 48

S waves (secondary, shear)

Front 49

Waves that travel along the Earth's away from the epicenter

Back 49

Surface waves

Front 50

Surface waves with horizontal shear

Back 50

love waves

Front 51

Surface waves with vertical displacement (rolling type of motion)

Back 51

Rayleigh waves

Front 52

Instruments that detect seismic waves

Back 52

Seismometers

Front 53

Paper or digital records of seismic waves

Back 53

Seismograms

Front 54

_______ waves have higher amplitudes and result in more damage

Back 54

Surface

Front 55

distance from seismic station to earthquake epicenter can be estimated from time difference arrivals of ___ and ___ waves

Back 55

P and S

Front 56

using records from three or more seismic stations, we can determine the location of the ____ by the intersection of circle with radii equal to the distance of the seismic station from the epicenter

Back 56

epicenter

Front 57

scales used to estimate the amount of energy released in an earthquake

Back 57

magnitude scales

Front 58

type of magnitude scale; older open-ended scale, found by measuring the amplitude of different types of seismic waves

Back 58

richter scale

Front 59

type of magnitude scale; newer method of determining amount of energy released in an earthquake based on the amount of slip along a fault, the rupture area of the fault, and the rock strength

Back 59

moment scale

Front 60

2 types of magnitude scales

Back 60

-richter scale
-moment scale

Front 61

a measure of an earthquake's effect on people buildings

Back 61

intensity scale

Front 62

most commonly used intensity scale; used when instrumental records are not available (mostly for historic earthquakes)

Back 62

modified mercalli

Front 63

largest earthquakes occur along ____ zones and occur over a range of focal depths from shallow to deep

Back 63

subduction

Front 64

smaller, shallow focus earthquakes occur on ___ ___ boundaries and along ____ ____ boundaries

Back 64

-transform fault boundaries
-divergent plate boundaries

Front 65

determined by looking at past seismicity along with possible impact on people (population)

Back 65

seismic hazard

Front 66

earthquake effects

Back 66

- ground rupture/permanent displacement
- aftershocks
- liquefaction
- landslides
- tsunamis

Front 67

smaller earthquakes that happen after an earthquake

Back 67

aftershocks

Front 68

when water saturated soils or sediments lose their strength and flow due to the shaking

Back 68

liquefaction

Front 69

can be triggered by earthquakes

Back 69

landslides

Front 70

harbor waves

Back 70

tsunamis

Front 71

tsunamis- caused by ___ in ___ ____ due to earthquake (or submarine landslides)

Back 71

offset in sea floor

Front 72

large subduction zone earthquakes that could produce tsunamis occur around the Pacific "Ring of Fire"

Back 72

Pacific Rim hazard

Front 73

tsunamis travel at ___ of km/hr

Back 73

100's

Front 74

time between earthquakes of a given magnitude for a particular region

Back 74

recurrence intervals

Front 75

like digging trenches across faults

Back 75

paleoseismology

Front 76

some of the energy of seismic body waves are reflected when they encounter layers with different densities; travel time to arrive at a seismic station can be used to determine the depth of the reflecting layer

Back 76

seismic reflection

Front 77

some of the energy of seismic body waves are refracted when they encounter layers with different densities (and therefore different seismic wave velocities); can be used to determine the depth to the refracting layer

Back 77

seismic refraction

Front 78

density is generally increasing with depth in the earth, which results in shallowing of ___ paths by seismic refraction

Back 78

ray paths

Front 79

thin outermost layer of the solid earth

Back 79

crust

Front 80

___ ___ has an average thickness of 7 km, average density of 3 g/cm3, P wave velocity of 7 km/sec, and is composed of basalt and gabbro

Back 80

oceanic crust

Front 81

____ ____ has an average thickness of 20-70 km, an average density of 2.7 g/cm3, P wave velocity of 6km/sec, and is composed of granitic and other plutonic and metamorphic rocks with sedimentary rock cover

Back 81

Continental crust

Front 82

extends from beneath the crust to the core-mantle boundary at a depth of approx. 2900 km; composed of solid ultramafic silicate rocks

Back 82

mantle

Front 83

extends from the core-mantle boundary to the center of the earth at a depth of approx. 6370 km; composed of iron with some nickel and perhaps some sulfur or other lighter element

Back 83

core

Front 84

the outer part of the core is ___

Back 84

liquid

Front 85

the inner part of the core is ___

Back 85

solid

Front 86

the boundary between the crust and the mantle; discontinuity is due to the chemical change in composition between the crust and the mantle

Back 86

mohorovicic discontinuity

Front 87

the layer in the upper mantle beneath the rigidly deforming lithosphere is known as ___

Back 87

athenosphere (low velocity zone)

Front 88

radial average velocity structure

Back 88

reference earth model

Front 89

density generally ____ with depth

Back 89

increases

Front 90

P waves entering the outer core are refracted to a steeper angle, resulting in a __ ___ ____ that extends from 103 degrees to 142 degrees in angular distance from the earthquake scourse

Back 90

p wave shadow zone

Front 91

P wave shadow tells us the depth to the ___ ___ ___

Back 91

core mantle boundary

Front 92

S waves do not travel through the outer core, and thus there is a __ ____ ____ beyond an angular distance of 103 degrees; this indicates that the outer core is liquid, as S-waves do not travel through a fluid

Back 92

S wave shadow zone

Front 93

refers to gravitational equilibrium between adjacent part of the earth's lithosphere that includes crust of different densities and thicknesses "floating" on the asthenosphere which can flow

Back 93

isostasy

Front 94

composed of low-density continental material

Back 94

deep roots beneath mountains

Front 95

____ scale glaciers load the crust, depressing it, forcing the mantle beneath to flow outward; melting of the glaciers results in inward mantle flow and uplift

Back 95

continental scale glaciers

Front 96

regions in ___ ___ will not produce a gravity anomaly

Back 96

isostatic equilibrium

Front 97

regions not in ____ ____ will produce positive or negative gravity anomalies

Back 97

isostatic equilibrium

Front 98

earth's magnetic polarity ___ over time

Back 98

flips

Front 99

temperature below which a mineral locks in the magnetic signature of the field in which it forms

Back 99

curie point

Front 100

magnetic field in the geologic past

Back 100

paleomagnetism

Front 101

correlation of magnetic polarity reversals isotopic ages

Back 101

magnetic polarity time scale

Front 102

temperatures increase with increasing depth

Back 102

geothermal gradient

Front 103

__ ___ gradients are related to the presence of magmas or from decay of radioactive elements such as uranium which are concentrated in the continental crust

Back 103

high crustal gradients

Front 104

greatest heat flow associated with ___ ___ ridges

Back 104

mid-ocean

Front 105

continental ___ are gently sloping regions next to continents

Back 105

shelves

Front 106

continental ___ are more steeply sloping regions seaward of the shelves

Back 106

slopes

Front 107

continental ___ are gently sloping wedge shaped regions at the base of the slopes

Back 107

continental rises

Front 108

the flattest regions on earth, abyssal plains make up the deep sea floors and are blanketed by sediments deposited by turbidity currents and pelagic sediments

Back 108

abyssal plain

Front 109

the deepest parts of the seal floor-- associated with subduction zones (convergent plate boundaries)

Back 109

oceanic trench

Front 110

extensive global underwater "mountain range" extending approximately 80,000 km found in the centers of ocean basins

Back 110

mid-oceanic ridges and rift valleys

Front 111

volcanoes that are found on the sea floor, they sometimes rise above sea level; they are often found in chains known as aseismic ridges that are associated with hot spots

Back 111

seamounts

Front 112

____ continental margins are located at plate boundaries (subduction zones)

Back 112

active

Front 113

____ continental margins are found at the edges of continents where there isn't a plate boundary (the oceanic crust and continental crust are part of the same tectonic plate)

Back 113

passive

Front 114

features include oceanic trenches, Waditi-Benioff Zones, where earthquakes occur at shallow depths near trenches and at increasing depths landward from trenches; and chains of volcanoes

Back 114

active margin

Front 115

features include continental shelves, slopes, and rises; submarine canyons that cut across the shelves and slopes; and Abyssal plains at the base of the rise

Back 115

passive margin

Front 116

____ faults occur between offset mid-ocean ridge segments, are seismically active, and are boundaries between two plates

Back 116

transform

Front 117

____ zones continue outside of the offsets, but are not seismically active, and separate different age parts of the same plate

Back 117

fracture

Front 118

fine grained deposits that settle through the water column; consists of wind blown clay sized particles and the remains of siliceous and carbonaceous organisms; thin near ridge crests where the oceanic crust is young and they have not had time to accumulate; get thicker with increasing distance from the ridge crest

Back 118

pelagic sediments

Front 119

sourced from land-- sand, silt, and clay sized sediments; thick deposits near continents- thinner away from continents

Back 119

terrigenous sediments

Front 120

layer __ of oceanic crust; consists of sediments that accumulate on the sea floor

Back 120

1

Front 121

layer __ consists of pillow basalts underlain by basaltic dikes and is approx. 1.5 to 2 km thick

Back 121

2

Front 122

layer 3 of oceanic crust consists of gabbro and is approx. 5 km thick

Back 122

3

Front 123

type of boundary; plates spread apart, new oceanic crust is generated

Back 123

divergent

Front 124

type of boundary; plates converge, oceanic crust is subducted into the mantle

Back 124

convergent

Front 125

type of boundary; plates slide past each other

Back 125

transform

Front 126

there are no oceanic crust older than ____ million years

Back 126

160

Front 127

average plate rates __ to __ cm/yr

Back 127

1-10

Front 128

basic types of transform boundaries

Back 128

ridge-ridge, ridge-trench, trench-trench

Front 129

right-lateral (strike slip) transform fault boundary

Back 129

San Andreas fault system

Front 130

types of convergent boundaries

Back 130

- ocean-ocean
- ocean-continent
- continent-continent

Front 131

type of convergent boundary; oceanic crust caps both subducting and overriding plates, deep sea trench, accretionary wedge and forearc basin, volcanic island arc, backarc basin (Lesser Antilles, Marianas)

Back 131

ocean-ocean

Front 132

type of convergent boundary; oceanic crust caps subducting plate, deep sea trench off coast, accretionary wedge and forearc basin, magmatic arc, backarc thrust belt, sedimentary basin (Andes, Cascades)

Back 132

ocean-continent

Front 133

type of convergent boundary; suture zone, opposing thrust belt zones, and basins on either side of high alpine zone (Himalaya, Appalachian)

Back 133

continent-continent

Front 134

causes of plate motion

Back 134

-ridge push
-slab pull