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Fall 2018 > Geology 101 Quiz 8 > Flashcards

Geology 101 Quiz 8 Flashcards

1
Q

metamorphic rocks definition

A

rocks that have been altered in composition or texture by heat or pressure

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2
Q

high-grade rocks form at

A

high temperature and/or pressure

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3
Q

low-grade rocks form at

A

lower temperature and/or pressure

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4
Q

if the temperature rises still higher,

A

the rock melts

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5
Q

regional metamorphism

A

occurs over a very large area

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6
Q

regional metamorphism is typically associated with

A

convergent plate boundaries

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7
Q

examples of regional metamorphism

A

subduction zones (high temp from friction) and continental collisions (high pressures from colliding plates)

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8
Q

contact metamorphism

A

high temperature metamorphism where magma heats up but does not melt adjacent rock

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9
Q

aureole

A

the halo of altered rock around the igneous intrusion formed by metamorphism

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10
Q

right next to the igneous intrusion will typically be

A

high grade metamorphic rock

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11
Q

rock farther away from the igneous intrusion that heats up will be

A

lower grade

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12
Q

cataclastic metamorphism

A

crushing and smearing of rock along fault zones

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13
Q

examples of cataclastic metamorphism

A

subduction zones, transform fault boundaries

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14
Q

hydrothermal metamorphism

A

metamorphism caused by interaction with hot water (usually involves exchange of some ions)

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15
Q

examples of hydrothermal metamorphism

A

mid-ocean ridges (Mid-Atlantic Ridge, East Pacific Rise)

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16
Q

what happens during hydrothermal metamorphism?

A

water in the pores in the ridge gets heated, the hot water thermally alters the rock and dissolves some of the minerals, the heated water is less dense and rises

when the hot water hits the cooler ocean water, some of the dissolved minerals precipitate (creates “black smokers”), cooler seawater enters from the sides to replace the rising hot water, continuing the cycle

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17
Q

burial metamorphism

A

heat and pressure caused by deep burial

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18
Q

example of burial metamorphism

A

sedimentary basins

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19
Q

what do sedimentary basins do?

A

collect eroded sediment from nearby mountains - as the sediment layers accumulate, the weight causes the crust to sink deeper in the mantle; over time, deposits can become buried under thousands of feet of sediment

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20
Q

the earth gets ? with depth by how much

A

hotter; about 30*C per km

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21
Q

shock metamorphism

A

caused by large meteorite impact

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22
Q

example of shock metamorphism

A

Meteor Crater, Arizona

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23
Q

at low temperature and high pressure, expect

A

cataclastic and regional metamorphism

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24
Q

at localized high temperature and pressure, expect

A

impact metamorphism

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25
Q

at intermediate temperature and pressure, expect

A

burial metamorphism

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26
Q

at high temperature and low pressure, expect

A

contact and hydrothermal metamorphism

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27
Q

metamorphism can produce both ? and ? alterations

A

mineral and textural

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28
Q

mineral alteration is achieved by

A

changing either the arrangement of atoms, or swapping some atoms for others

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29
Q

structural alteration

A

the chemical formula is the same, but the arrangement of atoms changes (usually more compact arrangement due to high pressure)

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30
Q

graphite turned to diamond is an example of

A

structural alteration (both are pure C, but the C atoms in diamond are much more closely arranged)

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31
Q

element substitution

A

one atom is exchanged for another resulting in a new mineral

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32
Q

exchange an Fe atom for a Mg atom is an example of

A

element substitution

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33
Q

textural alteration is caused by

A

either recrystallizing or by stretching or smearing

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34
Q

recrystallize

A

under high temperature and pressure, atoms within minerals can migrate to make larger crystals, or crystals oriented due to high differential pressures (i.e. more pressure in one direction)

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35
Q

when the pressure is the same in all directions, crystals will have a(n) ? alignment

A

random

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36
Q

if the pressure is greater in one direction (like from two plates colliding), crystals tend to align ? to the greater force

A

perpendicular

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37
Q

if differential pressure results in movement, minerals may be

A

smeared, stretched, or folded

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38
Q

alteration, both mineral and textural, can cause ?

A

foliation

39
Q

foliation

A

flat or wavy lines created by oriented mineral grains

40
Q

foliated rocks are metamorphic rocks with

A

oriented mineral grains

41
Q

low grade foliated rocks will often exhibit

A

cleavage

42
Q

cleavage

A

tendency to break along parallel planes (into flat slabs)

43
Q

fine grained rocks and coarse grained rocks - which way does not work?

A

fine grained CAN become coarse grained, but coarse grained CANNOT become fine grained

44
Q

non-foliated rocks

A

no oriented minerals; often products of burial, contact, and hydrothermal metamorphism (uniform pressure in all directions)

45
Q

examples of foliated rocks

A

slate, phyllite, schist, gneiss

46
Q

examples of non-foliated rocks

A

quartzite, marble, greenstone

47
Q

quartz rich sandstone with sand grains fused together

A

quartzite

48
Q

metamorphosed limestone

A

marble

49
Q

basalt plus hot seawater (hydrothermal alteration)

A

greenstone

50
Q

greenstone sometimes looks green, but sometimes it doesn’t - the green color comes from

A

chlorite

51
Q

porphryoblasts

A

large crystals developed in a fine grained matrix

52
Q

example of porphryoblast

A

garnet schist

53
Q

deformational texture

A

stretched rocks in which the original texture is still recognizable

54
Q

example of rock with deformational texture

A

stretched pebble conglomerate

55
Q

folding (aka ?)

A

bending without breaking (aka plastic deformation)

56
Q

faulting

A

breaking and moving rock on at least one side of the rupture

57
Q

a break without any movement is referred to as a

A

joint

58
Q

folding or faulting happen when

A

forces acting on the rock are greater in one direction than another, and the primary force exceeds the rock’s ability to resist deformation

59
Q

brittle

A

breaks rather than bend (like a stick of chalk)

60
Q

ductile

A

bends rather than break (like a copper sheet)

61
Q

confining pressure means

A

the pressure is high in all directions - if a rock is put in a vertical press, the slightest crack formed in a mineral will tend to propagate and the rock will abruptly break

62
Q

rock is more likely to fold under high ? pressure

A

confining

63
Q

raising the temperature will make a rock

A

softer and more easily folded

64
Q

strain rate: if rock movement is initiated rapidly, ? is likely; if the rock is allowed to move slowly, ? is more likely

A

faulting; folding

65
Q

three types of stress

A

compression, tension, shear

66
Q

compression

A

forces push toward the middle ->

67
Q

tension

A

forces pull apart

68
Q

shear

A

forces push one side parallel but opposite the other ^ v

69
Q

compression: starting with horizontal layers, compression results in ?

A

shortening by folding

70
Q

compression is common at

A

convergent boundaries

71
Q

tensional forces pull apart, resulting in

A

stretching and thinning (like plastic stretched beyond its elastic capacity)

72
Q

tension is common at

A

divergent boundaries

73
Q

shear: lateral forces ?

A

stretch and smear

74
Q

shear is common at

A

transform fault boundaries

75
Q

limbs

A

the layers pointing upward or downward from the bottom or top of a fold

76
Q

syncline

A

bottom of a fold (limbs pointing upward) - memory tip: we fall into sin

77
Q

anticline

A

top of a fold (limbs pointing downward)

78
Q

the youngest layers are exposed in the center of

A

eroded synclines (or in the center of a basin/outside of a dome)

79
Q

the oldest layers are exposed at the center of

A

an anticline (or in the center of a dome/outside of a basin)

80
Q

compressional forces can also cause rock layers to form ? instead of simple folds

A

domes and basins

81
Q

dome

A

limbs point in all directions (analogous to anticline)

82
Q

basin

A

limbs point upward in all directions (analagous to syncline)

83
Q

footwall vs hanging wall

A

hanging wall: could hang a lantern from - on the outside

footwall: could stand on (or at least put your foot on) - closer to the break

84
Q

reverse fault

A

hanging wall moves upward relative to footwall

85
Q

if the rising block ends up entirely on top of the underlying block, a reverse fault is called a

A

thrust fault

86
Q

normal fault

A

hanging wall moves downward relative to footwall

87
Q

normal fault is caused by

A

tension

88
Q

reverse fault and thrust fault are caused by

A

compression

89
Q

strike slip fault is caused by

A

strike slip

90
Q

forced apart

A

normal fault

91
Q

forced to overlap

A

reverse fault

92
Q

how can the knowledge of faulting help us deduce tectonic history

A

the type of faulting can tell us if a plate was compressed, stretched, or split laterally

93
Q

how can the knowledge of faulting help us map hazards

A

earthquake awareness - where there are faults, there have been earthquakes
a normal or reverse fault underwater can generate tsunamis

94
Q

how can the knowledge of faulting help us drill for oil

A

thrusted fault block doesn’t mean there’s no more oil - you can find sedimentary rocks under that igneous rock

Fall 2018 (24 decks)

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