Self-study
P1
According to the generally accepted theory of plate tectonics, the earth's crust consists of a dozen or so plates of solid rock moving across the mantle—the slightly fluid layer of rock between crust and core. ████ ███████████ ███ ████ ██ █████████ ██ █ ██████ ██ ███ ████████ ██ █████ ██████ ███████ ███ ███████ ██ ████ ████████ ███
Phenomenon & hypothesis ·
Earthquakes explained by plates colliding
Details of hypothesis ·
Collision causes subduction which causes earthquakes
Explains seismic hot zones: high levels of subduction produce many earthquakes
Phenomenon ·
But subduction can also occur without causing earthquakes
P2
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Hypothesis ·
Type of collision makes a difference
Collision type 1 ·
Plates moving toward each other
Occurs in seismic hot zones (many earthquakes)
Collision type 2 ·
Plates moving in same direction
Occurs in quiet zones (few earthquakes)
Analogy ·
Collision type 2 behaves like boat's oar
Collision zone moving across mantle (fluid layer) like boat over water; subducting plate descends steeply into mantle like oar in water
Evidence for hypothesis ·
Collision type 2 involves little contact (friction) between plates
Less friction means less likely to cause earthquake
Evidence for hypothesis ·
Collision type 1 involves more contact (friction) between plates
Collision zone not moving across mantle, so colliding plates remain in contact with each other. More friction means more likely to cause earthquake.
Analogy ·
Collision type 1 behaves like sheets of sandpaper
Colliding plates slide across each other; high resistance (friction)
P3
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Implication ·
of hypothesis
Regions with little subduction (plate collision) could still cause earthquakes, depending on collision type (collision type 1 causes greater risk)
Passage Style
Phenomenon-hypothesis (RC)
Single position
26.
According to the information in ███ ████████ █████ ███ ██ ███ █████████ █████ ██ ███████ ███████████ ███ ████ ████████████
a
regions where the ██████ ██ ███ █████████ ███████ ██████ ██ ████ ████ ███ █████ ████████ ███████ ████ ███ ██████
Sharp descent into the mantle is associated with plates that collide in the same direction, which
b
regions where resistance ████ ███ ██████ ██████ ██████████ ██ ████████
Resistance from the mantle is associated with plates that move in the same direction, which
c
regions where subduction ██████ ██ ███████ ██████
Supported. The author suggests in P2 that
d
regions where there ██ ███ ████████ ██████ ██ ██████████
Not supported, because the angle of subduction matters. Simply having a high amount of subduction does not imply frequent earthquakes. Although in P1 the author does indicate that most earthquakes take place in regions with high levels of subduction, this doesn’t imply that regions with the “greatest” levels of subduction have the most earthquakes. Those regions might have high subduction, but plates that collide in the same direction.
e
regions where plates ███ █████████ ██ ███ ████ ███████ █████████
Plates colliding in the same direction are associated with lower levels of earthquake-producing friction.