Q26

[TiffanyH940]

For this question, I'm a little thrown by choice C and D.

Paragraph 1 line 12-14 specifically said "most earthquakes take place in regions with very high level of subduction", which supports D almost word by word.

But then paragraph 2 explains when subduction occurs at shallow angles when two plates move toward each other happens in many seismic hot zones, which supports C.

How should I know which choice is better? or am I missing some other information?

[ohthatpatrick]

Good question. Good job getting rid of (A), (B), and (E), all of which involve keywords that relate to the times when we DON'T see earthquakes.

In terms of differentiating between (C) and (D), you're right that (D) has line 12-14 in positive support of it.

But then line 15-17 says that "there are also regions with high levels of subduction that are nonetheless FREE of earthquakes".

And you have line 54-56 saying that "regions with LOW levels of subduction may in fact be at significant risk of earthquakes".

So "area with high vs. low subduction" doesn't seem to be the best indicator.

Most quakes take place in areas with high subduction,
but since there are areas with high subduction that are quake-free
and areas with low subduction that are at a high risk for quakes,
it seems like "high subduction" isn't the strongest causal factor.

(If you're familiar with this covariation terminology, they weaken the causal association between high subduction and earthquakes: line 15-17 is Cause, No Effect, and line 54-56 is No Cause, Effect)

(C), meanwhile, is the essence of what the passage is about: the specific thing determining whether you do or don't have an earthquake in a high subduction zone is whether the plates are moving toward each other (opposite direction) and creating a shallow subduction angle, or whether they're moving in the same direction and creating a steep subduction angle.

The last paragraph is essentially saying, "now that we know that direction of plates / angle of subduction is really what determines quake vs. no quake, we might find some earthquakes in areas we wouldn't have previously expected."

(D) reflects the OLD WAY of understanding earthquakes (more subduction, more earthquakes).

(C) reflects the NEW WAY of understanding earthquakes (plates headed at each other / creating shallow subduction angle leads to more earthquakes)

Hope this helps.