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Earth Dynamics > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Types of sediments

A

clastic, chemical, bioclastic debris

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2
Q

clastic sediments

A

cemented together clasts, solid fragments and grains of broken off preexisting rock; formed by physical and chemical weathering processes

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3
Q

bioclastic debris

A

consists of shells from organisms; processes mediated by life. EX: Coral reefs, Chalk cliffs

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4
Q

chemical sediments

A

made up of minerals directly precipitated from water; do to change in temperature and flow (when it is removed from water through evaporation)-when water is hot it can hold more minerals

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5
Q

sinter

A

chemically precipitated silica

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6
Q

sinter example: Yellowstone

A

formed on top of a hot spot; water infilitrates from surface, heats up, goes to surface and it forms geysers

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7
Q

travertine

A

chemically precipitated calcium carbonate (gets to the surface, cools, can’t carry the carbonate so it falls out)

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8
Q

diatoms

A

silica skeletons

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9
Q

Why do you get bioclastic build ups deep in the ocean?

A

Plankton shed, and it falls to the bottom; not much else accumulating here

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10
Q

organic sediments

A

consist of carbon-rich relicts of plants or other organisms

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11
Q

What is the most common organic sediment?

A

Coal

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12
Q

beds/strata

A

packets of sediment that formed from particular sediment that was deposited in a particular way

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13
Q

package

A

a bed or stratum; then collected into a set of strata

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14
Q

How do packages form?

A

Related to environmental conditions, storms carry heavy sediments, for example.

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15
Q

How are ripples formed?

A

formed by currents that pick up stuff and move it down stream

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16
Q

What is cross-bedding and how is it formed?

A

“Mega ripples” formed by winf and water flowing in a constant direction over a long period of time; can create dunes

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17
Q

turbidites

A

Deep water deposits formed by density currents resulting from underwater landslides; a sign you moved from strong currents to deeper water

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18
Q

density current

A

a submarine landslide; moves sediments from the continental shelf, builds up, becomes unstable and falls to the deep ocean.

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19
Q

What are graded beds due to?

A

larger and heavier particles settling forst at faster, current speeds

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20
Q

What happens when a surface loses water?

A

It stretches, breaks the surface (you get mud cracks)

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21
Q

sorting

A

how a conglomerate is made up (all same grain size, mixture of large and small grains); shows the distance from the source

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22
Q

sedimentary basin

A

a hole created by plate tectonics; lowered topography where sediments collect; makes an archive of Earth’s history

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23
Q

What is a broad area of subsiding crust that allows thick sequences of sediment to accumulate?

A

sedimentary basin

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24
Q

What is a foreland basin?

A

When a mountain range forms, the crust around it bows down

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25
Q

What is a rift basin?

A

Crust stretches out and gets thinner in the middle, sinking down

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26
Q

What is an oceanic basin?

A

Started as a rift basin with a passive margin which isn’t currently active

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27
Q

What is an intra-continental basin?

A

a basin away from the plate boundary related to what is going on in the mantle. The mantle is dragging it downward. Subsidence is slow, but it keeps going

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28
Q

What alters sedimentary environments?

A

Tectonic uplift and sea level changes change accomodation space

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29
Q

What tells you what kind of sediment deposits you will get?

A

accomodation space (terrestrial, shallow marine, deep marine)

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30
Q

metamorphism

A

changes in rocks; always forming and destroying igneous and sedimentary rocks; plate tectonics will bury rocks, heat them up and squash them (recycling)

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31
Q

What is a preexisting rock called?

A

protolith

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32
Q

What happens when something metamorphoses?

A

Rock stays solid, but gets a change in minerality due to temperatures and pressures; only matters beneath the Earth’s surface

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33
Q

What rock has compositional bands?

A

gneiss

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34
Q

What are textural changes in rock linked to?

A

recrystallization and new mineral growth

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35
Q

What is mechanical realignment and deformation?

A

When forces change rocks (Get squashed or elongated clasts)

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36
Q

Can you see the results of chemical changes and deformation on rocks?

A

Yes

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37
Q

What are some causes of deformation?

A
  • high pressures due to deep burial (sedimentary basins, subduction zones)
  • stresses due to tectonic deformation
  • high temperatures foe to deep burial or contact with magma
  • **Plate tectonics are almost always the ultimate driver
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38
Q

What is foliation?

A

the planar fabric due to metamorphic processes; can be compositional (gneiss) or mechanical (cleavage)

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39
Q

What is gneiss?

A
  • light and dark bands
  • usually made up of quartz, mica
  • cuts through rock and something where a rock will break
  • from the basement of stable continental shields, or craters; the interior of deforming organic belts
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40
Q

Metamorphic rocks depend on what?

A

the protolith and the conditions and time

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41
Q

Which is older oceanic or continental crust?

A

continental crust

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42
Q

recrystallization

A

changing the mineral fabric, not changing the mineral compostions

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43
Q

necrystallization

A

new minerals form from the old; protoliths become unstable and undergo reactions and reform in new ways (recycling)

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44
Q

pressure solution (physical processes)

A

mineral grains dissolve where surfaces press together (spherical to elliptical grains); reprecipitates, which requires a small amount of water

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45
Q

What is plastic deformation?

A

squashing or stretching the individual grains; change shape without breaking; depends on temperature, pressure, and mineralogy

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46
Q

What is shearing in fault zones caused by?

A

strike-slip motion

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47
Q

Do chemical formulas change with phase changes? If not, what does change?

A

No. They have the same chemical formula. The crystal structure changes, so new minerals form

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48
Q

diogenesis

A

changes that happen at low temperatures, not usually considered metamorphism

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49
Q

How is blue schist formed?

A

through subduction metamorphism

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50
Q

What do you call the intensity of metamorphism?

A

grade

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51
Q

What is the first grade of foliation?

A

slate: mineral growth along bedding planes, making it easier to break

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52
Q

What is the second grade of foliation?

A

phyllite: start to see new mineral growths, rocks look less like original

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53
Q

What is the third grade of foliation?

A

schist: strong foliation, not necessarily associated with bedding plane, dominates how it breaks

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54
Q

What is the fourth grade of foliation?

A

gneiss: distinct compositional layering, not just structural layering

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55
Q

facies

A

distinctive mineralogy formed in distinctive conditions

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56
Q

What is thermal/contact metamorphism?

A
  • heat from magma invades host rock

- zoned bands of alteration zoned from high grade near pluton to low grade away from the pluton

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57
Q

Subduction metamorphism

A
  • unique low temp, high pressure minerals

- forms rare blue schist, only found at subduction zones

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58
Q

Organic metamorphism

A
  • compression smashes rocks and buries them deeply where they are heated
  • creates huge volumes of metamorphic rocks
  • probably the most important process
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59
Q

What causes an earthquake?

A

Stress is stored in the earth due to plate motions. When plates stretch and deform, earthquakes occur

60
Q

What is an earthquake?

A

Shaking of the earth due to sudden motion of crust

61
Q

What are planes of weakness that generate earthquakes?

A

faults

62
Q

Can volcanic eruptions and magma movement cause earthquakes?

A

Yes

63
Q

How do earthquakes happen?

A

Strain is built up over years and if you keep applying stress, it will fail

64
Q

What waves cause the most shaking?

A

Surface waves

65
Q

compressional waves

A

back and forth motion in the direction of propogation

66
Q

What are compressional body waves called?

A

primary waves

67
Q

What are compressional surface waves called?

A

Rayleigh waves

68
Q

shear/transverse waves

A

back and forth motion at right angles to propogation

69
Q

What are transverse body waves called?

A

secondary waves

70
Q

What are transverse surface waves called?

A

love waves

71
Q

How do seismometers work?

A

A heavy weight has great inertia. When the earth shakes, it does not, but the frame holding it does. A pencil attached to the weight draws on a paper to register the activity

72
Q

How are modern seismometers different?

A

use a coil to generate a current rather than drawing on paper

73
Q

Which travels faster, compressional p-waves or transverse s-waves?

A

compressional p-waves

74
Q

What does the delay between the p-waves and s-waves indicate?

A

The distance from the earthquake

75
Q

How can you pin point a source of an earthquake?

A

By getting several readings from several stations and triangulating it

76
Q

hypocenter

A

The 3D location of an earthquake

77
Q

epicenter

A

The location of an earthquake projected to the earth’s surface

78
Q

Do shallow earthquakes shake more than deeper earthquakes?

A

Yes

79
Q

magnitude of an earthquake

A

Based on the amplitude of shaking recorded on a seismometer corrected for distance

80
Q

earthquake intensity

A

a measure of the local shaking (high close to rupture, smaller further away from it)

81
Q

main shock

A

the largest quake in a sequence

82
Q

fore/after shocks

A

before/after the main shock

83
Q

Are definitions of fore shocks and after shocks post hoc?

A

Yes. We can’t identify a foreshock until the main shock occurs

84
Q

How are earthquakes related to plate tectonics?

A

Earthquakes are how relative motions between plates are detected

85
Q

trace

A

where a fault meets the surface

86
Q

scarp

A

a developed ridge line

87
Q

blind fault

A

cannot see the blind fault on the surface

88
Q

footwall

A

the higher wall in a fault situation

89
Q

hanging wall

A

the lower wall in a fault situation

90
Q

Where are earthquakes concentrated?

A

on faults and plate boundaries

91
Q

What causes smooth plate motions to turn into jerks and earthquakes?

A

friction at faults

92
Q

Thrust/Reverse/Compressional faults

A

compression, uplift; hanging wall up, footwall down; thrust faults are shallow, reverse faults are steep

93
Q

deformational boundary

A

find old rocks on top of young rocks due to thrusting

94
Q

Normal/Extensional faults

A

due to stretching/subsidence; hanging wall down; footwall up; block in the middle drops down

95
Q

marine terraces

A

waves cut notches, then earth uplifted, more notches cut, uplifted again (forms a stair structure)

96
Q

Strike Slip

A

due to lateral, translational motions; plates moving past eachother

97
Q

What are some effects of seismic waves?

A
  • shaking of buildings
  • landslide
  • liquefaction
98
Q

What is an intraplate earthquake?

A

A quake that happens away from a plate boundary; continental crust is old, and there may have been a plate boundary thre in the past

99
Q

How do we assess seismic hazards?

A
  • plate tectonics context (how much deformation is going on)
  • seismic history of the region
  • instrumental records
100
Q

paleoseismology

A

looking for the record of ancient of earthquakes to extend the records and better understand geological behavior of faults

101
Q

How can we protect people?

A

through building codes and the resiliency of buildings; should consider the worst case scenarios

102
Q

Does the smallest earthquake mean the smallest risk?

A

No

103
Q

Strategies in case of an earthquake

A
  • understand earthquake behavior
  • understand region specific risks
  • warning and mitigation strategies
104
Q

Are short term, precise prediction of earthquakes possible?

A

No. Only long term forecasts

105
Q

What are some “precursors”?

A
  • animal behaviors
  • foreshocks
  • low frequency radio signals
106
Q

What is seismology?

A

Uses the seismic waves earthquakes generate to determine the earth’s structure

107
Q

Can s-waves travel through liquids? Can p-waves travel through solids?

A
  • No. S-waves can only travel through solids

- Yes. P-waves can travel through solids, liquids and gases

108
Q

Can waves be reflected and refracted?

A

Yes

109
Q

What does the angle of reflection equal?

A

The angle of incidence

110
Q

Angle of refraction depends on the direction/magnitude of the velocity contrast. What does this mean?

A

increases in velocity=bent towards the horizontal

decreases in velocity=bent towards the vertical

111
Q

Can you get wave conversions with seismic waves? How?

A

Yes. When an up and down wave strikes at an angle, it causes shaking side to side

112
Q

What do reflection and refraction of waves affect?

A

travel times of waves

113
Q

moho

A

boundary between the crust and the mantle

114
Q

Seismic velocity usually increases with….

A

…depth. Gets refracted more as you go deeper

115
Q

How can we find the earth’s core?

A

No direct p-waves arrive at the surface on the other side of the earth. They are refracted, creating shadow zones.

116
Q

Do s-waves make it to the other side of the Earth?

A

No. They can’t travel through liquids, and the core is liquid.

117
Q

Isolated mountain ranges are _____ in origin.

A

igneous

118
Q

orogen

A

a linear chain/range of mountains produced by deformation or “orogenesis”

119
Q

thicker crust means

A

higher topography

120
Q

cordillera

A

several different ranges produced by different events

121
Q

convergent

A

ocean/continent collision; subduction

122
Q

True or False: Continental crusts subduct easily

A

False. It is almost impossible to subduct continental crusts

123
Q

Episodic collision of exotic terranes means…

A

…the growth of an orogen is not constant. Find rocks of various make-ups; exotic implies that they don’t belong there

124
Q

Are subuction zones isolated?

A

No. They continue further back after exotic terrane is fused with the coast

125
Q

Continent/continent collision

A

Plates collide and everything in the middle gets crumpled up

126
Q

Because continental crust can’t subduct, motion cases what?

A

Deformation and the thickening of crust

127
Q

Can mountains form in extensional settings?

A

Yes. Crust is stretched apart, then the middle chunk rotates

128
Q

Why are mountains so high?

A

Archimedes principle (buoyance). The density of the crust is less than the density of the anthenosphere, so the crust “floats” on top. The thickest block of crust floats the highest and sinks the deepest

129
Q

compressional stress

A

squashed up; volume remains the same

130
Q

tensile/extensional stress

A

stretched out and extends in the direction of the applied force

131
Q

shear/stress

A

distorted, rotated

132
Q

Brittle deformations form what?

A

faults

133
Q

Ductile deformations form what?

A

folds

134
Q

tilting

A

distortion of bedding

135
Q

folding

A

crumpled rock

136
Q

flexural slip

A

brittle; different layers move past each other when under compression

137
Q

passive flow

A

ductile

138
Q

Deformations are structured on what?

A

planes and lines

139
Q

Is there displacement on joints?

A

No. Joints are just breaks in rocks

140
Q

two limbs

A

planar beds dipping in opposite directions from each other; dips shallow towards hinge

141
Q

hinge

A

where the axial plane intersects with surface

142
Q

axial plane

A

plane is the middle of the folding; can be vertical or tilted, depending on fold shape

143
Q

anticline

A

arch, oldest rocks at the hinge

144
Q

syncline

A

bowl, youngest rocks at hinge

145
Q

monocline

A

a kink; both limbs have similar orientation (almost creates a step)

Earth Dynamics (3 decks)

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