Logical Reasoning

PT5 · S1 · Q12 Impact craters caused by meteorites

A free, expert breakdown of this official LSAT Logical Reasoning question.

Save & drill this skill — build targeted practice sets from questions like this one
Video walkthroughs — watch every question solved step by step
81 official LSATs — as questions, timed sections & full-length tests

Impact craters caused by meteorites smashing into Earth have been found all around the globe, but they have been found in the greatest density in geologically stable regions.

Curious Fact / Evidence

Why are impact craters found in greatest numbers in geologically stable regions?

Explanation / Conclusion

Those areas have lower rates of destructive geophysical processes. (There aren't as many earthquakes or volcanoes that would break up the crater or throw crap on top of it so that we couldn't see it.)

Evaluate

It's weird to see our boy Explain Curious Fact on a Sufficient Assumption question! It's much more common on Str / Wkn / Flaw / NA.

To logically prove that X is the cause of Y, we basically need to rule out all possible alternate explanations.

We can't just make the author's explanation more plausible. We have to guarantee it.

The author's explanation, "destructive geophysical processes" actually goes beyond the mere idea of geologic instability (like earthquakes and volcanoes). It would also include erosive forces like wind / rain.

So the author is really saying,

But maybe we see more craters in certain regions simply because more asteroids landed there in the first place.

Goal

Look for an answer ruling out all possible alternate explanations for why there are more impact craters in these stable regions.

12.

The conclusion is properly drawn if which one of the following is assumed?

A meteorite that strikes exactly
Out of Scope
Sure, this makes sense (when a meteorite hits, it's gonna basically destroy everything in the blast radius), but what does this have to do with solving the mystery of why most craters are found in stable regions? We have no reason to think that meteorites ever strike exactly the same spot as an earlier meteorite, nor would we have any reason to think that such a phenomenon would be more likely occurring in stable vs. unstable regions.
9% picked this
Rates of destructive geophysical processes
Out of Scope
This is just a wishy-washy idea saying that, "within a given region, the rate of destructive stuff ebbs and flows over tens of thousands of years". Sure, but more stable regions average out to having less destructive stuff, and less stable regions average out to have more destructive stuff. Zooming in on the variety within these groups does nothing to rule out alternate explanations for why we find most craters in stable regions.
15% picked this
The rate at which the
Out of Scope
Comparing how many meteorites strike Earth nowadays vs. back in the day has no bearing on this conversation. Nowadays, are the meteorites still mainly hitting in stable regions? And if so, do we know why? This answer doesn't address either of those, and that's what we're here to investigate.
2% picked this
Correct
Actual meteorite impacts have been
Why this is right
Well this is not quite a Sufficient Assumption, test 5!, but it's the best available answer. It rules out one important alternate explanation, which is more than we can say for the other answers. An alternate explanation for why we find more craters in the stable regions could simply have been that more meteorites have landed there. This answer choice rules out that possibility. The impacts have happened fairly evenly around the whole globe, so the fact that we find more craters in the stable regions seems to just be because in the unstable regions, the craters get hidden by destructive geophysical processes. Does that HAVE to be the explanation? Technically, no. There could be humans or animals in those unstable regions that are doing things to cover up the impact craters. It doesn't HAVE to be destructive geophysical processes. But given that asteroid craters are huge and last millions of years (the famous crater from the asteroid that killed the dinosaurs is 65 million years old and like 100 miles in diameter), it would be a pretty corny objection to say, "Maybe it's not destructive geophysical processes that has hidden the craters in the unstable regions, maybe it's ... human/alien intervention." Technically the answer has not ruled out that exotic possibility, so the conclusion might not be 100% proven, but we'll still consider the answer that makes it 99% proven the best available.
Skill tested: Sufficient Assumption · how this choice captures the argument's function is the move to repeat next time.
68% picked this
The Earth’s geologically stable regions
Opposite
If anything, this weakens the argument by offering a different explanation for the observed concentration: stable regions might just be more thoroughly studied, so more of their craters are identified.
6% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill

LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free