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

Start practicing free

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.

Premise

Identified meteorite impact craters are most densely concentrated in geologically stable regions.

Conclusion

This relative abundance must be explained by the lower rates of destructive geophysical processes in those regions (i.e., craters are preserved better there).

Evaluate

The author leaps from "more craters identified in stable regions" to "preservation explains it." But there is an obvious alternative: maybe meteorites really do strike stable regions more often. To rule out that alternative, the author needs to assume meteorite impacts have been distributed roughly evenly across Earth's surface — so that the unevenness in identified craters reflects unequal preservation, not unequal strikes.

Goal

The correct answer should establish that meteorite impacts are roughly evenly distributed across Earth's surface.

12.

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

  1. A meteorite that strikes exactly

    Out of Scope

    This is about whether one meteorite obliterates an earlier impact at the same spot. That speaks to crater destruction within a single location, not to whether stable regions had similar overall impact rates as unstable regions. It does not address the alternative explanation that meteorites strike unevenly.

    8% picked this

  2. Rates of destructive geophysical processes

    Out of Scope

    Variation in destructive processes within a single region over time does not bridge the gap. The argument needs us to know that meteorite impacts have been distributed similarly across regions; this answer talks about variation across time within regions, which is a different question.

    17% picked this

  3. The rate at which the

    Out of Scope

    The recent rate of meteor strikes does not address whether historical impacts were evenly distributed across Earth. The argument is about why crater density differs by region today — what matters is the long-term distribution of impacts, not the current rate.

    1% picked this

  4. Correct

    Actual meteorite impacts have been

    Why this is right

    This is the bridge. If actual meteorite impacts have been spread fairly evenly across Earth's surface throughout geological history, then the unevenness in identified craters cannot be due to impacts happening more often in stable regions. The only remaining explanation is that something has made craters survive more in those regions — exactly the author's conclusion (lower rates of destructive geophysical processes). Plug this in and the conclusion follows.

    Skill tested: Sufficient Assumption · how this choice captures the argument's function is the move to repeat next time.

    67% picked this

  5. 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. That is an alternative to the author's preservation explanation — not the bridge the argument needs.

    7% 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