Self-paced
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
25.
Based on the information in ███ ████████ █████ ███ ██ ███ █████████ █████████ █████ ████ █████████ ████████ ███ ████ ██████████
a
Depending on the ████████████ ███████ █████ ████████ ███ ███████ █████ ██ ██████ ███ ███████████ ████ █████ ████████ █████ █████████
This doesn’t fit, because we have no reason to think there’s “always a possibility plate velocity could increase.” The author never suggested anything that implies plate velocity can always increase. Since (A) isn’t supported, it wouldn’t be a logical completion.
b
The lower the █████ ██ ██████████ ██ ██ █████ ███ ███████ ███ ███████████ ████ ███ ██████████ █████ ██ █████████ ██ █ ███████ ██████
This doesn’t fit, because it’s unsupported. The author never suggests that lower levels of subduction imply higher chance of shallow subduction angles. The author never presents a correlation between amount of subduction and angle of subduction.
c
Any region where ██████████ ██████ █████ ██████ ██ ████████ ██ ███ █████ ██ ██████████ ███ █ ██████████ ████████ ██ ███████ █████████
This doesn’t fit, because the author’s emphasis at the end is on the “nature of the subduction” taking place — the direction of the plates that collide. The author doesn’t suggest that subduction might always increase and that this is why there might be risk in low subduction zones.
d
Even at low ███████ ███ ███████ █████ ██ ██████████ ██████████ ███████ ██ █ ███████████ ██████ ██ ███████ █████████
This doesn’t fit, because it’s not supported. The author doesn’t suggest that subduction at low levels “inevitably” (always) results in a lot of seismic activity. The angle of subduction matters.
e
Even in such █ ███████ █ █████ ██████████ ██ █ ███████ █████ ██ ██████ ██ █████ █ █████ ████ ██ ████████████████████ █████████
This fits at the end, because this helps explain why regions with low levels of subduction may be at risk of earthquakes. If a plate in a collision descends at a shallow angle — meaning,