Geology 101 Quiz 8

Question 1

metamorphic rocks definition

Answer 1

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

Question 2

high-grade rocks form at

Answer 2

high temperature and/or pressure

Question 3

low-grade rocks form at

Answer 3

lower temperature and/or pressure

Question 4

if the temperature rises still higher,

Answer 4

the rock melts

Question 5

regional metamorphism

Answer 5

occurs over a very large area

Question 6

regional metamorphism is typically associated with

Answer 6

convergent plate boundaries

Question 7

examples of regional metamorphism

Answer 7

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

Question 8

contact metamorphism

Answer 8

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

Question 9

aureole

Answer 9

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

Question 10

right next to the igneous intrusion will typically be

Answer 10

high grade metamorphic rock

Question 11

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

Answer 11

lower grade

Question 12

cataclastic metamorphism

Answer 12

crushing and smearing of rock along fault zones

Question 13

examples of cataclastic metamorphism

Answer 13

subduction zones, transform fault boundaries

Question 14

hydrothermal metamorphism

Answer 14

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

Question 15

examples of hydrothermal metamorphism

Answer 15

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

Question 16

what happens during hydrothermal metamorphism?

Answer 16

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

Question 17

burial metamorphism

Answer 17

heat and pressure caused by deep burial

Question 18

example of burial metamorphism

Answer 18

sedimentary basins

Question 19

what do sedimentary basins do?

Answer 19

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

Question 20

the earth gets ? with depth by how much

Answer 20

hotter; about 30*C per km

Question 21

shock metamorphism

Answer 21

caused by large meteorite impact

Question 22

example of shock metamorphism

Answer 22

Meteor Crater, Arizona

Question 23

at low temperature and high pressure, expect

Answer 23

cataclastic and regional metamorphism

Question 24

at localized high temperature and pressure, expect

Answer 24

impact metamorphism

Question 25

at intermediate temperature and pressure, expect

Answer 25

burial metamorphism

Question 26

at high temperature and low pressure, expect

Answer 26

contact and hydrothermal metamorphism

Question 27

metamorphism can produce both ? and ? alterations

Answer 27

mineral and textural

Question 28

mineral alteration is achieved by

Answer 28

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

Question 29

structural alteration

Answer 29

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

Question 30

graphite turned to diamond is an example of

Answer 30

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

Question 31

element substitution

Answer 31

one atom is exchanged for another resulting in a new mineral

Question 32

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

Answer 32

element substitution

Question 33

textural alteration is caused by

Answer 33

either recrystallizing or by stretching or smearing

Question 34

recrystallize

Answer 34

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)

Question 35

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

Answer 35

random

Question 36

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

Answer 36

perpendicular

Question 37

if differential pressure results in movement, minerals may be

Answer 37

smeared, stretched, or folded

Question 38

alteration, both mineral and textural, can cause ?

Answer 38

foliation

Question 39

foliation

Answer 39

flat or wavy lines created by oriented mineral grains

Question 40

foliated rocks are metamorphic rocks with

Answer 40

oriented mineral grains

Question 41

low grade foliated rocks will often exhibit

Answer 41

cleavage

Question 42

cleavage

Answer 42

tendency to break along parallel planes (into flat slabs)

Question 43

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

Answer 43

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

Question 44

non-foliated rocks

Answer 44

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

Question 45

examples of foliated rocks

Answer 45

slate, phyllite, schist, gneiss

Question 46

examples of non-foliated rocks

Answer 46

quartzite, marble, greenstone

Question 47

quartz rich sandstone with sand grains fused together

Answer 47

quartzite

Question 48

metamorphosed limestone

Answer 48

marble

Question 49

basalt plus hot seawater (hydrothermal alteration)

Answer 49

greenstone

Question 50

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

Answer 50

chlorite

Question 51

porphryoblasts

Answer 51

large crystals developed in a fine grained matrix

Question 52

example of porphryoblast

Answer 52

garnet schist

Question 53

deformational texture

Answer 53

stretched rocks in which the original texture is still recognizable

Question 54

example of rock with deformational texture

Answer 54

stretched pebble conglomerate

Question 55

folding (aka ?)

Answer 55

bending without breaking (aka plastic deformation)

Question 56

faulting

Answer 56

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

Question 57

a break without any movement is referred to as a

Answer 57

joint

Question 58

folding or faulting happen when

Answer 58

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

Question 59

brittle

Answer 59

breaks rather than bend (like a stick of chalk)

Question 60

ductile

Answer 60

bends rather than break (like a copper sheet)

Question 61

confining pressure means

Answer 61

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

Question 62

rock is more likely to fold under high ? pressure

Answer 62

confining

Question 63

raising the temperature will make a rock

Answer 63

softer and more easily folded

Question 64

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

Answer 64

faulting; folding

Question 65

three types of stress

Answer 65

compression, tension, shear

Question 66

compression

Answer 66

forces push toward the middle ->

Question 67

tension

Answer 67

forces pull apart

Question 68

shear

Answer 68

forces push one side parallel but opposite the other ^ v

Question 69

compression: starting with horizontal layers, compression results in ?

Answer 69

shortening by folding

Question 70

compression is common at

Answer 70

convergent boundaries

Question 71

tensional forces pull apart, resulting in

Answer 71

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

Question 72

tension is common at

Answer 72

divergent boundaries

Question 73

shear: lateral forces ?

Answer 73

stretch and smear

Question 74

shear is common at

Answer 74

transform fault boundaries

Question 75

limbs

Answer 75

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

Question 76

syncline

Answer 76

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

Question 77

anticline

Answer 77

top of a fold (limbs pointing downward)

Question 78

the youngest layers are exposed in the center of

Answer 78

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

Question 79

the oldest layers are exposed at the center of

Answer 79

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

Question 80

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

Answer 80

domes and basins

Question 81

dome

Answer 81

limbs point in all directions (analogous to anticline)

Question 82

basin

Answer 82

limbs point upward in all directions (analagous to syncline)

Question 83

footwall vs hanging wall

Answer 83

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

Question 84

reverse fault

Answer 84

hanging wall moves upward relative to footwall

Question 85

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

Answer 85

thrust fault

Question 86

normal fault

Answer 86

hanging wall moves downward relative to footwall

Question 87

normal fault is caused by

Answer 87

tension

Question 88

reverse fault and thrust fault are caused by

Answer 88

compression

Question 89

strike slip fault is caused by

Answer 89

strike slip

Question 90

forced apart

Answer 90

normal fault

Question 91

forced to overlap

Answer 91

reverse fault

Question 92

how can the knowledge of faulting help us deduce tectonic history

Answer 92

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

Question 93

how can the knowledge of faulting help us map hazards

Answer 93

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

Question 94

how can the knowledge of faulting help us drill for oil

Answer 94

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