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GEO > GEO EXAM 2 > Flashcards

GEO EXAM 2 Flashcards

1
Q

Absolute time

A

Putting numbers on rocks, estimates of the earth’s age

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2
Q

Ideas of earth’s age

A

Salinity of the oceans, heat loss, thickness of sedimentary rocks, radioactive decay

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3
Q

Half-Life

A

The amount it takes for 1/2 of the orginial parent atoms to decay to the daughter.

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4
Q

The Geologic Time Scale

A

Originally based on fossils - now based on radioactive decay

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5
Q

Precambrian (time)

A

4.6 billion years to 570 million years. Comprises of 80% of earth’s time.

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6
Q

Paleozoic (time)

A

540 million years to 250 million years. (explosion of life)

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7
Q

Mesozoic (time)

A

250 million years to 65 million years. (dinosaurs)

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8
Q

Ceozoic (time)

A

Age of mammals. 65 million years to present.

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9
Q

declination

A

the angle between magnetic north ( the direction the north end of the compass needle points) and true north

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10
Q

Sea Floor Spreading

A

The formation of new areas of oceanic crust, which occurs through the upwelling of magma at midocean ridges and its subsequent outward movement on either side.

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11
Q

Features of sea floor

A

Long continuous mountain chains, trenches (deep valleys), continental shelves, abyssal plains.

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12
Q

Age of sea floor

A

200 million years

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13
Q

Sea Floor Spreading theory

A
  1. The sea floor moves laterally away from the ocean ridges (spreading centers)
  2. Magma rises up to the sea floor ridges
  3. The magma hardens to form a new seafloor
  4. The ridges crack in half and move away from each other
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14
Q

Evidence that supports seafloor spreading

A
  1. The age of the seafloor
  2. Seafloor sediment thickens away from the ridge
  3. Valleys run down the center of the ridges
  4. Paleomagnetism
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15
Q

Paleomagnetism

A

magnetic polarity stripes on the seafloor

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16
Q

How do polarity stripes form?

A

as basalt cools at the ridges, it preserves the polarity of earth’s magnetic field.

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17
Q

Three compositional layers

A

crust, core, mantle

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18
Q

Crust features

A
  1. Made up of oceanic and continental crust
  2. 6 to 25 miles thick
  3. covered by sediment and sedimentary rock
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19
Q

Mantle features

A
  1. makes up about 80% of the earth
  2. made mostly of olivine
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20
Q

Outer core

A

liquid Fe

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21
Q

Inner core

A

solid Fe

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22
Q

What results in the Earth’s magnetic field

A

circulation of the liquid Fe outer core

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23
Q

Lithosphere features

A

100 km thick, rigid, strong, cold, brittle, less dense

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24
Q

Lithosphere

A

Contains the crust and a small amount of the upper mantle

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25
Q

Asthenosphere features

A

100 to 300km, plastic, pliable, weak, hot, flows, more dense

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26
Q

Theory of plate tectonics

A
  1. The surface of the earth is covered by 7 large lithospheric plates
  2. These lithospheric plates travel in directions that differ from different adjacent plates
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27
Q

How are lithosphere plates created?

A

at ocean ridges and slide over the asthenosphere

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28
Q

Seismology

A

Study of earthquakes

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29
Q

Where do faults occur?

A

crust and upper mantle

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30
Q

Elastic rebound theory

A

explains origin of earthquakes

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31
Q

elastic rebound theory features

A
  1. If a rock is stressed it can store up its energy elastically
  2. When the strength of the rock is exceeded the rock breaks (brittle)
  3. The rocks on either side of the fault snap back to their orginial shape and release the stored energy
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32
Q

What determines the size of the earthquake?

A

the amount of energy stored up

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33
Q

What do seismographs rely on?

A

inertia

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34
Q

geophone

A

a device that converts ground movement into voltage which can be recorded

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35
Q

seismic waves

A

waves that travel through rock

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36
Q

properities of waves

A
  1. wavelength
  2. amplitude
  3. period
  4. frequency
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37
Q

high energy wave

A

high amplitude

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38
Q

low energy wave

A

low amplitude

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39
Q

classification of seismic waves

A

body waves and surface waves

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40
Q

body waves

A

pass through the earth and travel outward in all directions from the focus

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41
Q

surface waves

A
  • travel along the surface of the earth
  • travel more slowly than P and S waves
  • last wave to be detected
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42
Q

types of body waves

A

p wave (primary, compression) and s wave (secondary, shear)

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43
Q

p-wave

A
  • consist of alternating pulses of compression and expansion
  • produce changes in volume and density
  • travel through solids, liquids, and gases
  • motion of the wave is parallel to its direction
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44
Q

s-wave

A
  • shear waves
  • motion is perpendicular to direction
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45
Q

determining the location of the epicenter

A
  • measuring the time interval between P and S wave arrival
  • three seismic stations are needed
46
Q

modified mercalli scale

A
  • qualitative measures based on earthquake effects in populated areas
  • intensity ratings between 1 - 12
47
Q

shake map

A

shows the intensity of shaking over an area that has experieced an earthquake

48
Q

richter scale

A
  • quantitatively measures the amount of energy released from an earthquake
  • needs instrument measurement
  • only one magnitude for an earthquake
49
Q

How is magnitude calculated?

A

measuring the height of the largest S wave

50
Q

effects of an earthquake

A

1) ground motion (destroys buildings)
2) faults (breaks the ground surface)
3) fire - gas lines break
4) landslides, avalanches
5) liquefaction
6) tsunami
7) flooding
8) differential ground settlement

51
Q

seismic gap

A
  • location where a earthquake hasn’t occured in a long time
  • areas where built up stress has not been released
52
Q

stress

A

push or pull on a rock

53
Q

strain

A

deformation - the measure of change in shape to a stressed material

54
Q

types of deformation

A
  1. elastic
  2. ductile
  3. brittle
55
Q

elastic

A

reversible or nonpermanent change in shape - the rock stores energy

56
Q

ductile deformation

A

stretching or flowing of material without breaking

57
Q

brittle deformation

A

breaking or fracturing

58
Q

continental drift theory

A

Alfred Wegener’s theory stating the world used to all be connected but drifted

59
Q

Evidence for continental drift

A

Identical: continents, fossils, mountains, age of rocks, glaciated areas, ice flow

60
Q

divergent plate boundaries

A

a line along which two adjacent plates move apart from each other

61
Q

divergent margins

A

places where new oceanic lithosphere is created

62
Q

origin and evolution of divergent boundaries

A

1) begin as rift zones on the continents - pulling apart of continental crust
2) as the continent is pulled apart, basaltic magma is extruded into the rift valley (oceanic crust is being formed)
3) the valley floor sinks and is filled with sea water
4) divergence continues and results in a large ocean basin

63
Q

examples of divergent margins

A
  1. mid-atlantic ridge
  2. iceland
64
Q

physical aspects of divergent margins

A
  • state of stress (tensional or pulling)
  • earthquake activity ( abundant, low magnitude, shallow depth)
  • volcanism (intense volcanism, basaltic)
65
Q

convergent margins

A

places where two lithosphereic plates move towards each other

66
Q

oceanic - oceanic crustal convergence

A

one lithospheric plate turns down into the earth and is recycled

67
Q

trench

A

arcuate shaped valleys on the seafloor

68
Q

subduction zone

A

the trench is the location of a downturning lithosphere

69
Q

physical aspect of oceanic-oceanic crust convergence zones

A
  • state of stress (compression)
    -earthquake activity (abundant, follows the down going slab - shallow and deep, high magnitude earthquakes)
    -volcanism (abundant)
70
Q

examples of oceanic-oceanic crust convergence

A
  1. Japan
  2. aleutian islands
71
Q

oceanic - continental crust convergence

A

oceanic crust dives beneath the continental crust

72
Q

features of oceanic - continental

A
  1. trench - location of a subduction zone
  2. continental volcanic chains
73
Q

physical aspects of oceanic-continental crustal convergence

A

1) stress (compression)
2) earthquakes (shallow to deep, lots of them, high magnitude)
3) volcanic activity (abundant)

74
Q

examples of oceanic to continental

A
  1. West coast of south america - andes
  2. Cascades
75
Q

continental - continetal

A

continents are buoyant and don’t subduct ( continental collisions)

76
Q

features of continental-continental crustal convergence

A
  1. double thickness of continental crust
  2. huge mountain chains
77
Q

physical aspects on continental-continental crustal convergence

A

compression, earthquakes (high magnitude, shallow), mountains

78
Q

examples of continetal crust collisions

A
  1. himalyas
  2. alps
  3. appalachians
79
Q

convergent margins

A

crust is a passive passenger on the lithosphere

80
Q

hot spots

A
  • heat anonomly in the asthenosphere
  • magma makes its way to the surface from deep depths
81
Q

Examples of hot spots

A

yellowstone, hawaiian islands

82
Q

mechanisms of plate tectonics

A
  • convection of the mantle
  • slab pull
83
Q

shear

A

a stress which is applied horizontal or tangential to the face of a material

84
Q

mantle convection

A

motion caused by density changes due to heating

85
Q

remanant magnetism

A

rocks can preserve a “fossil” record of the earth’s magnetic field

86
Q

earth’s magnetic field

A

the earth behaves as if there is a giant magnetic bar inside

87
Q

Types of magnetic information

A

polarity, declination

88
Q

polarity

A
  • the location of the north and south poles
89
Q

normal polarity

A

todays magnetic field

90
Q

reversed polarity

A

180 degrees from today’s field

91
Q

paths of apparent polar wandering

A

ancient rocks, layered rocks and diff continent rocks

92
Q

does the earth’s magnetic pole wander?

A

NO, the continents wander, not the magnetic poles

93
Q

dipping bed

A

a layer of rock that is not horizontal

94
Q

strike

A

is a line representing the intersection of that feature with a horizontal plane

95
Q

dip

A

The dip gives the steepest angle of descent of a tilted bed or feature relative to a horizontal plane

96
Q

anticline

A

a type of fold that is an arch like shape and has its oldest beds at its core. Older towards center of the fold.

97
Q

syncline

A

a type of fold that has its younger layers closer to the center, lower than a anticline

98
Q

normal fault

A

drops rock on one side of the fault DOWN relative to the other side (ex, san andreas)

99
Q

reverse fault

A

one rocky block is pushed up relative to the rock on the other side

100
Q

strike-slip

A

scrape along side by side

101
Q

dip slip

A

inclined fractures where the blocks have shifted vertically. (normal or reverse)

102
Q

how to read a seismogram

A

first p waves, then s waves, then surface waves

103
Q

distance between p and s waves

A

can be used to determine the distance between the station and the earthquake

104
Q

passive margin

A

transition between oceanic and continential lithosphere that is not an active plate margin.

105
Q

mechanism for plate tectonics

A

convection currents beneath the plates move the crustal plates in different directions. - thermal convection

106
Q

transform features

A

shallow earthquakes, shear stress, no volcanism

107
Q

1989 Loma Prieta

A

6.9 magnitude, 63 deaths, 3757 injured

108
Q

2011 Sendai Earthquake

A

9 magnitude, around 20k deaths

109
Q

Seismograph

A

Instrument that detects vibrations and shaking of earth

110
Q

Where do Texas earthquakes occur?

A

near El Paso and in the Panhandle

GEO (8 decks)

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