geoscience midterm

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71 Terms

1
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According to wegener’s hypothesis of continental drift, all continents were once attached and formed a single landmass that he called _____, He thought that this land mass survived until about the middle of the _*___* era
pangea / mesozoic
2
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what is the relationship between the coastlines on the east side of the atlantic and those on the west side?
Continents on the east side could fit snugly against those on the west.
3
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Which of the following statements about wegener’s reconstruction of late paleozoic pangea is true?
Areas glaciated during late paleozoic laid over the south polar region at the time
4
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When wegener compared rock units how exposed on different continents bordering the Atlantic, what did he discover?
Fossils of identical land dwelling species occur on continents that are now separated from one another by the ocean
5
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When wegener compared rock units now exposed on different continents bordering atlantic, what did he discover?
fossils of identical land dwelling species occur on continents that are now separated from one another by the ocean
6
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Why did most geologists initially oppose wegener’s hypothesis of continental drift?
wegener could not explain how or why continents move
7
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keeping in mind shape of magnetic field lines in space around earth, what is true?
Magnetic inclination is approx 0º at equator and 90º at poles
8
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Why can samples of basalt exhibit paleomagnetism?
dipoles of tiny magnetite grains in basalt align with the earth’s field as the basalt cools and stay that way once the basalt is cold.
9
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Today, what is the favored explanation of appareny polar wander paths?
Continental drift with respect to relatively fixed magnetic poles
10
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When a magnetometer is towed over a positive marine mgnetic anomaly…
The measured magnetic field is stronger than expected
11
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Studies of sea floor bathymetry demonstrate that
deep ocean trenches, the deepest of which have a depth of about 11 km, border chains of active volcanoes
12
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Where is the heat flow of oceanic crust the greatest?
along the axis of the mid ocean ridges
13
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Which of the following statements about earth’s magnetic field is correct?
The polarity of the magnetic field reverses every now nad then
14
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A lihtospheric plate consists of
The crust and uppermost part of the mantle
15
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What defines the location of plate boundaries?
The location of abundant earthquake epicenters
16
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What is the difference between a passive continental margin and an active continental margin?
Passive margins are not plate boundaries, whereas active margins are
17
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In the atlantic ocean, where does the youngest oceanic crust occur
adjacent to the mid ocean ridge
18
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In which of the following pairs of terms does the second term represent the type of process that happens at the first term?
Mid ocean ridge / sea floor spreading
19
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Which of the following processes happens at the axis of a mid ocean ridge?
all of the above (molten rock, mineral saturated water, stretching force)
20
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Which of the following statements about a hot spot track is correct?
The youngest volcano of the track occurs at one end of the track
21
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At a (blank), continental crust is being stretched apart. As a consequence, the crust becomes (blank) and volcanoes erupt
Rift / thinner
22
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Why can’t continental crust be subducted?
Too buoyant and can’t sink into asthenosphere
23
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Which of the following statements concerning the forces that drive plate motions is correct?
Ridge push and slab pull forces have the greatest influence on the velocity of plate motion
24
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The character of a lava flow depends on the viscosity of the lava erupted. (blank) lava is less viscous than (blank) and thus flows out as (blank)
basaltic / rhyolitic / thin sheet
25
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Volcanic ash consists of
tiny shards of glass
26
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An avalanche of hot ash is flowing down the flanks of a volcano is known as
pyroclastic flow
27
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What type of pyroclastic debris builds a streamlined form, as show by the image?
a bomb
28
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A large, cone shaped volcano consisting of alternating layers of ash and lava is a
stratovolcano or composite volcano
29
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If a volcano is erupting a gassy, felsic magma, then it is more likely to be (blank)
an explosive eruption
30
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which of the following is not a hazard related to volcano eruptions?
heat wave
31
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What measurable clues indicate that a particular volcano may erupt in the near future?
The volcano changes shape as the magma chamber fills
32
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What is NOT a functional protection or mitigation effort to prevent volcanic hazards?
prediction of exact timing or style of the eruption
33
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Mafic lava erupted at submarine volcano will produce
pillow basalt
34
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which statement is NOT correct
aerosols from volcanic eruptions may be a cause of global warming
35
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Mt. St. Helens erupted in 1980, sending out gas and pyroclastics. Geologists have found evidence of many eruptions of St. Helens, dating back 37,000 years. The mountain is huge and is composed of layers of lava and pyroclastics. Which of the following is most likely true?
It’s a stratovolcano (or composite cone)
36
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Rhyolite lava…
all of the possible answers are correct
37
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Lava is the greatest volcanic hazard to human life because it travels so fast
False, lava is not the greatest threat to human life
38
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The point on the surface of the earth that lies directly above the place where a slip on a fault occurs is the
epicenter
39
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On a (blank) fault, the hanging wall block slips down the surface of the fault, relative to footwall. If the fault displaces the ground surface, a (blank) develops
normal / fault scarp
40
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According to the elastic rebound theory of earthquake generation…
a rock bending elastically before breaking; the sudden break and or frictional sliding causes earthquakes
41
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which of the following is the correct sequence of seismic waves that will be recorded at a distance from the epicenter?
P waves, S waves, surface waves
42
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A mechanical seismograph consists of a pen attached to a suspended weight, and a rolling drum with paper attached. During an earthquake,
the weight stays fixed in space, while the drum and the paper move
43
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To locate the epicenter of an earthquake, what information do you need?
The difference in the arrival times of the P- and S- waves, as recorded at three different stations
44
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The “intensity” of an earthquake…
is defined by the amount of damage caused by the earthquake
45
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A magnitude 4 earthquake results in ground motion that is (blank) the ground motion that occurs during a magnitude 2 earthquake, and releases approximately ____ the amount of energy
100x / 1000 x
46
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Which statement about the distribution of earthquakes on Earth is correct?
Earthquakes occur in discrete belts, along plate boundaries
47
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Which statement about the distribution of earthquakes at convergent plate boundaries is correct?
Hypocenters occur in the Wadati-Benioff zone, down to a depth of about 670 km below the surface
48
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All else being equal, which building would more likely survive a large earthquake?
One whose foundation is built on an exposure of granite bedrock
49
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Tsunamis can be caused by
earthquakes at subduction zones
50
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In the context of geology, a “joint” refers to
a natural crack, on which there has been no sliding, in rock
51
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Both normal faults and reverse faults are considered to be ___ faults. The hanging wall block of a normal fault slides *__*_ the surface of the fault
dip-slip / down
52
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The fault shown in the above diagram is a vertical surface, and the slip lineations on it are horizontal. What type of fault is it?
strike slip
53
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The type of deformation does NOT depend on
Grain size
54
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Major weather events such as hurricanes and tornadoes release as much energy as the great earthquakes
False. they do not.
55
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A tsunami…
may be just a low and very broad wave at sea, but both slows in speed and grows in height as it approaches shore
56
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If a rock undergoes enough stress to produce elastic strain, an earthquake always happens.
False. an earthquake does not always happen.
57
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Geologists distinguish among different kinds of downslope movement based, in part, on
rate of movement
58
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The gradual downslope movement of surficial sediment or soil in a temperate climate is called ___. If such movement occurs in the tunrdra, where it is permafrost, it is called ___
creep / solifluction
59
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If the water table beneath a hill rises, because of either heavy rain or the impounding of a reservoir,
adjacent slopes become more unstable (because detachment surfaces become weaker)
60
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Downslope movement can be triggered when
downslope forces exceeds resistance force
61
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In a typical slump, the glide surface (slip surface) is ___, and at the uphill end, a ___ formes
curving (spoon shaped) / head scarp
62
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Which of the following will __increase__ the potential for mass movement on a slope?
deforestation
63
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_____ in sedimentary rock may become a failure surface
Bedding plane
64
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The principal difference between a debris slide and a debris avalanche is the _____
degree to which the displaced material remains internally coherent
65
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The main difference between a slump and a debris slide is the ____
shape of the path taken by the moving mass
66
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to a geologist…
all landslides are mass movements, but not all mass movements are landslides
67
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moisture among sediment grains…
can promote stability if present in small amounts, but promotes mass wasting if sediment is saturated
68
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which of the following factors decreases the risk of mass movements
adding vegetation to the side of the hill
69
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slow downhill movement of regolith creep is due to
expansion and contraction
70
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submarine landslides are…
responsible for catastrophic tsunamis
71
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geologic mapping can identify regions at landslide risk by
identifying past failures and detecting slow movements