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Answer Key
1) C
2) D
3) D
4) C
5) A
6) B
7) E
8) E
9) C
10)
11)
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
B
D
A
A
B
C
B
C
D
E
A
Mid-ocean ridge
system; divergent or
constructive or
extensional
22) Aulacogen/aulocogen
23) Asthenosphere
24) Pacific;
Mariana/Phillipine (in
that order)
25) Farallon Plate
26) Yellowstone
27) Mantle Convection
28) Andrija Mohorovičić
29)
Frederick Vine or Lawrence
Morley or Drummond Matthews
30)
Silica, silicon, Si, SiO2 (any
variant)
31)
Transform or conservative;
Pacific; North American (in that
order)
32)
Extensive or divergent or
extensional
33)
Gondwana(land) and Laurasia
34)
Back-Arc Basins
35)
Craton
36)
Accretionary wedge/prism or
accreted terranes
37)
Alfred Wegener; The Origin of
Continents and Oceans;
(in that order)
38)
Oceanic; density (in that order)
39)
Composite; shield (in that order)
40)
Wadati-Benioff Zone
Bonus: Bryce Canyon; Utah
41)
Wilson Cycle
42)
Divergent or constructive or
extensional
43)
Convergent or destructive
44)
Orogenesis
45)
Juan de Fuca
46)
Cocos
47)
Nazca
48)
Scotia
49)
Eurasian
50)
51)
52)
53)
54)
Arabian
Nazca(F); South American(G) (in that order)
Pacific(B); Ring of Fire
African(I); Arabian(K) (order does not matter)
Iron and Nickel (partial credit for sulfur or oxygen because they are not as
predominant)
55) Lithosphere (not crust)
56) Mesosphere
57) Mantle Plume
58) Isostasy
59) Hypsometric
60) 4-7%
61) 58-62%
62) Mt. Everest
63) Mariana Trench
64) Mantle plumes
65) Mantle convection
66) Kilauea
67) Mafic; basalt; gabbro (in that order)
68) Transform or conservative
69) Iceland
70) East African Rift; aulacogen/aulocogen
71) The layering reflects density stratification of the Earth: each layer is denser
than the one above it (2). The core formed more or less simultaneously with the
formation of the Earth, the crust formed later (1). Continental crust has grown
through geologic time; while oceanic crust is continually created and destroyed
(2).
72) The key factor is how fast the plates are spreading apart at the divergent
boundary (2). Mid-ocean ridges are elevated because the newly formed crust and
lithosphere is hot and therefore expanded. As the lithosphere moves away from a
ridge, it compacts, so water depth increases. Water depth will be proportional to
age (square root of age). In a slow spreading ridge like the Mid-Atlantic Ridge,
lithosphere of a given age (and therefore contracted to a given depth) will still be
close to the ridge, so the slope will be steep (2). In a fast spreading ridge like the
East Pacific rise, lithosphere of that same age and depth will be much further
away, producing a gentle slope away from the ridge (2).
73) The basin and range is uplifted and extended continental crust (1). Dominant
normal faulting produces horsts and grabens that are the ranges and basins,
respectively (2). The basin and range has above normal elevation and below
average crustal thickness, so it is not in isostatic equilibrium (2). Rather, it is
supported by dynamic upwelling of mantle asthenosphere beneath it, which is
also causing the extension (2). Products of erosion of the ranges fill the valleys
with sediment; the valleys would be otherwise much deeper (1).
74) New seafloor is continually created at mid-ocean ridges as magma rises to
surface (2). As this is happening, the Earth’s magnetic field reverses occasionally
(about every 500,000 years or so). Lavas of the new seafloor are magnetized
parallel to the Earth’s field at the time they form (2). The field of seafloor forming
during normal magnetic epochs adds to the Earth’s field, creating positive
anomalies, seafloor forming during reversed epochs subtracts from the Earth’s
field, forming negative anomalies (2). Thus we see bands of magnetic anomalies
parallel to the ridge.
75) The cyclical opening and closing of ocean basins caused by movement of
the Earth’s plates (.5). The Wilson cycle begins with a rising plume of magma
and the thinning of the overlying crust (1). As the crust continues to thin due to
extensional tectonic forces, an ocean basin forms and sediments
accumulate along its margins (1). Subsequently subduction is initiated on one
of the ocean basin's margins and the ocean basin closes up (1). When the crust
begins to thin again, another cycle begins. It is named after J. Tuzo Wilson, a
Canadian geophysicist (.5)
76) As long as one of these are mentioned then they get 2 points:
Earthquakes: Seismic activities have always been a main cause of landslides
throughout the world. Any time plate tectonics move the soil that covers those
moves with it. When earthquakes occur on areas with steep slopes, many times
the soil slips causing landslides. Furthermore, ashen debris flows caused by
earthquakes can also trigger mass movement of soil.
Heavy Rainfall: When sloped areas become completely saturated by heavy
rainfall many times landslides can occur. Without the aid of mechanical root
support the soil simply runs off when it contains too much water.
77) A tsunami is a series of ocean waves generated by sudden displacements in
the sea floor, landslides, or volcanic activity (1). An earthquake is the shaking and
vibration of the Earth's crust due to movement of the Earth's plates (plate
tectonics) (2). Since earthquakes cause tsunamis, then plate tectonic movement is
what eventually causes tsunamis so form.
78) At a 'typical' subduction zone, an oceanic plate typically sinks at a fairly high
angle. A volcanic arc grows above the subducting plate (2). During the growth of
the Rocky Mountains, the angle of the subducting plate may have been
significantly flattened, moving the focus of melting and mountain building much
farther inland than is normally expected (4). It is postulated that the shallow angle
of the subducting plate greatly increased the friction and other interactions with
the thick continental mass above it. Tremendous thrusts piled sheets of crust on
top of each other, building the extraordinarily broad, high Rocky Mountain range
(+2 if included).
79) North American Plate (1), Pacific Plate (1), Juan de Fuca Plate (also acceptable
is Gorda Plate) (1)
80) It is a structural basin that develops adjacent and parallel to a mountain belt
(1). Foreland basins form because the immense mass created
by crustal thickening associated with the evolution of a mountain belt causes
the lithosphere to bend, by a process known as lithospheric flexure (1).