Q12 - Impact craters caused by meteorites

[weiyichen1986]

Dear Manhattan LSAT members,

I have some trouble figuring out this one. The conclusion is about impact craters in those density regions. The evidence is that "the rate" of destructive in those regions are very low.

And the question is about assumption. So isnt the answer at least contain the idea of "the rate" ??? D just does not get me. Can any one explain to me? Thank you in advance.

[noah]

I think you're a bit off about the core of this argument (no tectonic pun intended, and perhaps none made - )

The conclusion is that the greater abundance must be because stable regions don't have lots of earthquakes/volcanoes (which, we assume, would cover up the evidence of the craters). Why? Because there are more craters found in these stable regions.

Since the conclusion is a "this must be the reason" we should be thinking what other explanation there could be. It's possible - albeit kind of hard to believe - that there simply have been more meteorites striking these stable regions. (Perhaps, and I know this is crazy, meteorites are magnetically attracted to stable regions.) Crazy or not, it may be true - perhaps through random chance - that meteorites have not struck the earth in a fairly even pattern, and so we can't say that the stability is the reason we see more craters; instead it could be the way the meteorites fall.

(D) fills that gap and establishes that the meteorites fell in a generally even distribution pattern over the Earth's surface.

(A) establishes that we may not see that multiple meteorites have fallen on the same spot, but who says that's happening, and, if it is, who says that it happens only in the stable regions? Wouldn't that affect the results everywhere?

(B) may be tempting--look below to badalov90's comment to read why--but it's irrelevant if the rates have changed over time. We were told that the regions are geologically stable in the time period that the argument is concerned with. It's not important that those regions have been stable the entire time that earth has existed.

(C) is similar to (B).

(E) is tempting - perhaps the reason we found more in the stable regions is because scientists have looked more in the stable regions. But, this actually provides another reason other than the conclusion to explain the premise! This is the opposite of what we want.

Tell me if that doesn't clear it up.

[schmid215]

Hmm. Not sure that clears it up for me. In the first place, "fairly evenly" is not the same as "evenly"; "fairly evenly" could mean a relatively equal distribution of impacts except in one region, which has a disproportionate number of them. But going further, "evenly" doesn't even seem to guarantee the conclusion, because couldn't it be something other than geo-physical processes or impact numbers? How about human preservation of the crater sites for religious purposes?

[noah]

Hmm. Not sure that clears it up for me. In the first place, "fairly evenly" is not the same as "evenly"; "fairly evenly" could mean a relatively equal distribution of impacts except in one region, which has a disproportionate number of them. But going further, "evenly" doesn't even seem to guarantee the conclusion, because couldn't it be something other than geo-physical processes or impact numbers? How about human preservation of the crater sites for religious purposes?

I've given it some thought, and I can't see a hole in your point about there being some remaining alternate explanations, albeit a rather fantastical one--I think it's not an air-tight argument. Bravo for either twisting up this LSAT geek or seeing a hole in what should be a hole-less argument (once (D) is in place).

As for "fairly evenly" vs. "evenly"--I think that it's reasonable to interpret "fairly evenly" as good enough for this argument as the argument is not talking about a high level of mathematical precision.

It seems like you might have spotted an old LR question with some rust!

[sumukh09]

More light on why D is correct?

[noah]

More light on why D is correct?

Hi Sumukh, which part of the explanation above doesn't make sense?

[sumukh09]

More light on why D is correct?

Hi Sumukh, which part of the explanation above doesn't make sense?

Hey Noah,

I just reread your explanation and it makes some more sense now; I guess I was looking for another interpretation on why D is a sufficient assumption that guarantees the truth of the conclusion. But after rethinking it it seems like D would exclude against the possibility that the meteorites are somehow supernaturally attracted to geologically stable regions as you suggested in your explanation above.

[noah]

More light on why D is correct?

Hi Sumukh, which part of the explanation above doesn't make sense?

Hey Noah,

I just reread your explanation and it makes some more sense now; I guess I was looking for another interpretation on why D is a sufficient assumption that guarantees the truth of the conclusion. But after rethinking it it seems like D would exclude against the possibility that the meteorites are somehow supernaturally attracted to geologically stable regions as you suggested in your explanation above.

Great! You might be sensing the issue that I discussed with someone else a bit later in the thread--that there still seems to be some other possible problems.

[badalov90]

Hey Noah,
You said that B) is out of scope because its not about changes over time...

I would like to perpetuate the argument that the negative of "B) Rates of destructive geophysical processes within any given region DO NOT vary markedly (conclusion says lower rates) over throughout geologic time" would destroy the argument because the argument is assuming that the rates of geologic processes are in fact consistently lower than other areas and that is why we can draw conclusions from the regions. If the rates WERE changing then the whole argument falls apart.

Thank you, your input will be highly appreciated.

[noah]

Hey Noah,
You said that B) is out of scope because its not about changes over time...

I would like to perpetuate the argument that the negative of "B) Rates of destructive geophysical processes within any given region DO NOT vary markedly (conclusion says lower rates) over throughout geologic time" would destroy the argument because the argument is assuming that the rates of geologic processes are in fact consistently lower than other areas and that is why we can draw conclusions from the regions. If the rates WERE changing then the whole argument falls apart.

Thank you, your input will be highly appreciated.

Thanks for your thoughtful question.

First off, we shouldn't be using the negation test here since this is not a necessary assumption question.

Second, the LSAT doesn't go for negating premises. Assumptions are all about the connection between the premises and conclusion, so be wary anytime you think an assumption, when negated, would destroy an argument by showing a premise is not true. Usually, as I think is the case here, the negated assumption gives context to the premise. In this case, I think we can thread the needle and have there be geologically stable regions in the context of the argument, while also holding that regions have varying rates of geologic destruction. Perhaps the stable regions mentioned in the argument were unstable in the first 1000 years of existence, and then settled down, awaiting the arrival of those meteorites.

But, I may have dealt with (B) too superficially--I may just go and edit that when I'm done writing this.

[WaltGrace1983]

I don't like this question at all. I think this is a weak sufficient assumption question but potentially a great necessary assumption question. I would hope that, with this question being more than 20 years old, that some of these minor issues are completely eradicated from the test I will take.

I think that this isn't correct because it doesn't make the conclusion absolutely 100% sound from the premises given. If we are talking about sufficient assumption questions, we are talking about ones that, with the assumption provided, would make this the case. Let me go through this question before I explain myself.

There is a greater density of craters in stable regions
-->
This must be explained by lower rates of destructive processes in those stable regions

So the argument is basically saying that there are more craters and therefore this MUST be caused by less stuff interfering with the evidence of them:earthquakes, volcanoes, etc. The thought we are perhaps supposed to have here is "well couldn't there be other causes? Maybe there were just less meteorite impacts?" If there were less meteorites in these geographically stable regions then this would certainly explain why there were less impacts found in such regions, ultimately pointing to a flaw in the conclusion.

(A) There are a few problems with this.
#1 is that we are already confining the scope to only meteorites that strike "in the same spot." Sufficient assumption questions are generally fairly big and because we are talking about all meteorites in the argument we must be talking about all meteorites in the answer for it to completely fill the gap. For example, "Wide Receiver X of the Dallas Cowboys is faster than Wide Receiver Y on the San Francisco 49ers. Thus, every player on the Dallas Cowboys is faster than every player on the San Francisco 49ers" and the answer choice is "Wide Receiver Z is faster than every player on the 49ers"...does this prove the conclusion? Absolutely not. In other words, if I am talking about "meteorites smashing into Earth" in the argument and confine myself to "meteorites that strike exactly the same spot," this is pretty much always going to be wrong. I need SUFFICIENCY. I need something that will completely fill the gap! I can't just talk about certain meteorites and expect a good outcome.
#2, and perhaps more important, is that this would not explain the conclusion! This doesn't say whether or not we are talking about meteorites in certain regions and this is critical! If we say that these meteorites are obliterating all traces of earlier impacts, would this not mean that this is happening all over the place? In other words, since we don't know anything about the specifics of which meteorites this answer choice is referring to, we can say that all impacts would be affected by this evenly. Therefore, this wouldn't explain why there are more impacts found in one spot than the other.

(B) This is an answer that is giving us some very strong language, which is great for sufficiency questions. However, it is quite inconclusive. We are talking about how there are more impact craters found in more stable environments only because there are less destructive rates of geophysical processes. This answer talks about "rates" which is good. However, does it matter that they "vary markedly?" Let's say they do. Does the conclusion absolutely 100% follow? I may even say this weakens the conclusion. Maybe. It is a very vague answer choice that can be interpreted in many ways (not a good sign - especially for a sufficient assumption Q)

(C) This is very similar to (B). However, when spun the right way, this may also weaken the conclusion. Maybe the rates of meteorite strikes increases ONLY in the more stable geophysical regions? Who knows.

(E) This definitely weakens the conclusion a bit. If we say that "we find more impacts in more stable regions" yet we also say that "we study those regions more intensely" than we probably found more simply because we looked harder - not because of anything geophysical. The key word here is "find/found." The argument is not saying that there ARE more impacts...just that we have FOUND more impacts.

(D) Here is what we are left with. I can see why this is the best answer choice (for a strengthen question, perhaps - maybe even a necessary assumption). However, this is just not sufficient.

#1: The point about "fairly evenly" versus "evenly" is definitely nitpicky. Is it something to really worry about? Probably not EXCEPT in sufficient assumption questions. From what I have gathered, there should be NO DOUBT that an answer is right if you think about (unfortunately, having 1:20 to complete a question is not always conducive to the most critical and relaxed thought processes ). The words "fairly evenly" opens up doubt I think. In this context, what does "fairly evenly" mean? Is having 150 impacts in America and 200 impacts in Australia mean "fairly" evenly? Wouldn't 50 impacts make a BIG difference when determining how many have been found. I just don't like that word "fairly" when you are making a conclusion about something that absolutely "must be." Either way, moving on...

#2: This still doesn't seem to justify the conclusion. Let's say we throw out the argument about "fairly evenly." Let's say we have discovered 150 impacts in Hawaii where there are lots of hurricanes, volcanoes, etc. and 200 impacts in Kansas where there is hardly anything. There have been objectively 205 impacts in both locations - despite a difference in findings. With this in mind, does it have to be the case that it was the lower rates of geophysical processes that caused this? No! Maybe, as someone else mentioned, they were preserved better in certain areas by the inhabitants. Maybe in Hawaii there have been numerous hotels built over impacts and thats why we have "securely identified" less of them. Maybe, as (E) alludes to, we simply did look harder.

I think this problem is flawed. However, I have gained a lot from thinking about it. Let me know if I am missing something and if it is not this problem - but I - that is flawed