Impact craters caused by meteorites smashing into Earth have

Question

12. 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. This relatively greater abundance of securely identified crater in geologically stable regions must be explained by the lower rates of destructive geophysical processes in those regions.

The conclusion is properly drawn if which one of the following is assumed?

(A) A meteorite that strikes exactly the same spot as an earlier meteorite will obliterate all traces of the earlier impact.
(B) Rates of destructive geophysical processes within any given region vary markedly throughout geological time.
(C) The rate at which the Earth is struck by meteorites has greatly increased in geologically recent times.
(D) Actual meteorite impacts have been scattered fairly evenly over the Earthâ€™s surface in the course of Earthâ€™s geological history.
(E) The Earthâ€™s geologically stable regions have been studied more intensively by geologists than have its less stable regions.

kapslock · Answer

Arsene,

D looks much more appropriate to me. Can you describe your thought process behind B?

D is fairly straightforward - you are more likely to discover meteorite craters in the regions you've studied well.

gandy_achar · Answer

Ans - D

After a lot of thought, I go with D. B was close, however on close scrutiny, B states that the rate of destruction is a factor of geological time rather than geological region. The author here is trying to make a comparison between geologically stable regions.

Arsene_Wenger · Answer

Kaps, 1. Impact craters have been found in the greatest density in geologically stable regions. Why? 2. Because of lower rates of destructive geophysical processes in these geologically stable regions. This conclusion (1) can hold iff the rates of destructive processes are known to be the same in all geological regions, in which case if the rates are high, then impact craters will not be found in substantial amounts (as well as the opposite). When you negate (B), my choice, you get: Rates of destructive geophysical processes within any given region DO NOT vary markedly throughout geological time. How does this affect the conclusion? If the rates of destructive geophysical processes do not vary, then you cannot say for sure (as the argument states) that the rates are solely responsible for the occurence of impact craters in certain regions. Refuting (D) by negation: Actual meteorite impacts have NOT been scattered fairly evenly over the Earth’s surface in the course of Earth’s geological history. IMO, that is what the argument already tells you - that there is unequal distribution of impact craters in regions of earth (which are on the surface of earth). So, it's not an assumption. Hope i'm correct after all these. 8-)

GMATT73 · Answer

Is this a trick question? Consider this: the face of the Earth during Pangea was much different than the current face of the earth; which will undoubtedly be unrecognizable in another 2 billion years. Assuming so, the only possibility is  C.

kamal_tejnani · Answer

(A) A meteorite that strikes exactly the same spot as an earlier meteorite will obliterate all traces of the earlier impact.
- will affect stable and non-stable regions

(B) Rates of destructive geophysical processes within any given region vary markedly throughout geological time.
- where does geological time come into picture

(C) The rate at which the Earth is struck by meteorites has greatly increased in geologically recent times.
- same as above

(D) Actual meteorite impacts have been scattered fairly evenly over the Earthâ€™s surface in the course of Earthâ€™s geological history.
Only when the impacts have been scattered evenly, can such comparisons be made, and hence
conclusion drawn that the " lower rates of destructive geophysical processes in those regions" is
a reason for higher density
Hence D seems to be correct


(E) The Earthâ€™s geologically stable regions have been studied more intensively by geologists than have its less stable regions.
- "Impact craters caused by meteorites smashing into Earth have been found all around the globe,"...
implies all regions have been surveyed and "but they have been found in the greatest density in geologically stable regions.." means they have been compared.

Arsene_Wenger · Answer

OK i change my mind. It's (D). I have seen my error. (B) says '...within a region' not '...the whole globe', and what is geological time? If you negate (D), i think the arg. falls apart because if they craters were not evenly distributed, then you can't say it's because of the stable geo. regions...blah, blah, blah. hmmmm.........heaven help me!

DLMD · Answer

I think it's D. Because we must assume the impact rates are the same, then we can make comparisons.

GMATT73 · Answer

WinWinMBA:

Could we have the OA on this one please?

Antmavel · Answer

After checking each answer and eliminate 4 of them, I would finish with D but it's not an easy choice.

D for me

WinWinMBA · Answer

The OA is D.

Impact craters caused by meteorites smashing into Earth have

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards