Q15 - According to current geological theory

[aileenann]

This is a strengthen question. Here, we should focus on the conclusion more than on the premises, though sometimes an answer choice can strengthen an argument by strengthening a premise. Also, we need to look at all of the answer choices because we are looking for the one that MOST strengthens the argument (sometimes people forget this).

The conclusion here is that melting ice likely contributed to the earthquakes in Sweden at the end of the ice ages.

Let's look at the answer choices:

(A) would require an additional assumption to be helpful - namely as assumption linking this cracking to earthquakes. In fact, this assumption that cracking earth goes along with earthquakes is in the original argument as well, but this answer choice doesn't fix it.

(B) is irrelevant because these cracks could have come at any time - not necessarily during the end of the Ice Age.

(C) is also irrelevant - northern Canada doesn't tell us much about Sweden unless we make our own assumption to make it relevant.

(D) is the answer. We know that
melting ice --led to--> reduced weight pressing on the crust --led to--> cracks in the crust appearing.
The author concludes that "melting ice ---led to-> earthquakes",
so she is assuming that "cracks in the crust appearing" leads to "earthquakes".
(D) provides some connective tissue for this missing link.

(E) would weaken the argument, by providing an alternate cause for the earthquakes around that time period.

One general note about scope on strengthen/weaken questions. This scope inquiry is not nearly as narrow as when we are doing assumption questions. It's not just that you see new ideas, but rather that these new ideas (as in (E)) are logically irrelevant to the original argument,

Any questions or thoughts?

[mrudula_2005]

Thanks for explaining this question. I'm still stuck on what makes D a better answer than A - is A off because we can't be sure that "the earths crust tends to crack" will lead to an earthquake (is that the outside assumption you are talking about?). And D threw me off because it specified "...near the earthquake site"

Where in the argument does it state that there was cracking of the earth's crust near Sweden?

Thanks!

[aileenann]

I think you hit the nail on the head as far as the problem with (A) - we can't assume that cracking has anything to do with earthquakes. On the other hand, (D) connects up the earthquakes with the cracking, which is precisely what we needed to do.

As far as your nit with (D) - "near the earthquake site" - I'd argue two things. First, I think it's implicit in the argument that the ice melting was near Sweden - either because we should be able to figure this out (via common sense - I agree, a little unfair) or because it is implied by the author's reasoning that the ice age cracks had something to do with earthquakes. In the latter case, (D) is a good answer because it strengthens an implicit assumption of the argument.

I hope this helps. I think it shows you have good instincts, because your very uneasiness reflected exactly what needed to be corrected in this argument!

[kdeclark]

I was hoping you could say a bit more about when to take something as implied. I realize it's not an exact science, but any advice you have would be helpful.

I see that, because the cracks could have happened at any time since the Ice Age, D is a better choice B. However, it doesn't seem SO obvious to me that that rules B out. Here is how I understand the argument:

1. Melting ice at end of IA caused cracks in some parts of the earth's crust
2. Sweden experienced earthquakes at the end of the IA.
---
5. Therefore, the melting ice caused these earthquakes.

It seem to me that two obvious things are missing:

3. Cracks cause (or, better, generally cause) earthquakes.
4. There were cracks under Sweden.

D addresses 3. B addresses 4.

So is this the way to approach this problem: You say, look, I need both of these, but B does a lousier job of providing 4 than D does of providing 3, so D is more of a strengthener (even though, without 4, 3 doesn't get it done--perhaps there weren't cracks anywhere near Sweden!).

This leads to my broader question: You say that the ice melting near Sweden is implicit in the argument. But that sort of worries me: I didn't see that at all. I don't know anything about the ice age, or Sweden. I think (and I bet most people think) of Sweden as being cold--and if it's naturally cold than there would be LESS ice melt there after the ice age, no? And even if that's wrong, the argument says that lasting cracks appeared in SOME of of those parts under the stress of pressure from below.

Isn't it more reasonable (for a non-expert) to assume that cracks in the earth generally cause earthquakes? Isn't that what fault lines are?

So my question is, given all of these things that I feel I have to assume to get to the point you said was implicit, and all of the implicit assumptions I think are MORE obvious than the one you felt comfortable drawing, I feel like you must be looking at the problem differently, and that you are probably doing this because you know a lot more about how the LSAT is written.

Since dividing the things we can assume from the things we can't is such an important skill, I was hoping you could say a few general things about how to improve it.

[zana.nanic]

Premises:
1.During Ice Age we have melting ice-> reduced pressure on Earth'crust->cracks
2.Sweeden racked with severe earthquakes

Conclusion:
Melting Ice-> earthquakes


Hey wait a minute!!Where is this conclusion coming from?When in the argument is the author liking melting ice with earthquake?Those are two different premises.

(What the author is assuming is that have melting ice-> reduced pressure on Earth'crust->cracks ->earthquakes )


Answers choices:
A)I already know this!It is my premise: reduced pressure-> cracks. This is not helping my reasoning to reach the conclusion.
B)This could be something. Keep it for now
C)Canada? Who cares! Even if this was the case how can we reach to the conclusion that the meeting ice of the Ice Age caused the earthquakes? Maybe it is just a coincidence
D)This is the statement of our assumption! This makes the argument sound!
E)This weakens the argument. If this is true, the conclusion that melting ice caused the earthquakes falls apart.


Review B. Why is B wrong?This shows there were cracks in Norther Europe, more cracks in Norther Europe so..?This is not helping my causation claim!! It shows a correlation between crack in Norther Europe (and Sweden indeed) and the severe earthquakes in Sweden. BUT CORRELATION IS NOT CAUSATION AND THIS IS NOT ENOUGH TO STRENGTHEN A CONCLUSION DEALING WITH CAUSATION. Reminder: do not fall in this trap.
Lsat could have said that there were a lot of penguins in norther Europe at the time of the earthquakes but this does't mean that penguins caused the earthquake. The problem is that Lsat uses your understanding and common sense to trick you- a lot of cracks is reasonable(penguins are not) and therefore we go for it! Logically is the same thing!

[amil91]

I was hoping you could say a bit more about when to take something as implied. I realize it's not an exact science, but any advice you have would be helpful.

I see that, because the cracks could have happened at any time since the Ice Age, D is a better choice B. However, it doesn't seem SO obvious to me that that rules B out. Here is how I understand the argument:

1. Melting ice at end of IA caused cracks in some parts of the earth's crust
2. Sweden experienced earthquakes at the end of the IA.
---
5. Therefore, the melting ice caused these earthquakes.

It seem to me that two obvious things are missing:

3. Cracks cause (or, better, generally cause) earthquakes.
4. There were cracks under Sweden.

D addresses 3. B addresses 4.

So is this the way to approach this problem: You say, look, I need both of these, but B does a lousier job of providing 4 than D does of providing 3, so D is more of a strengthener (even though, without 4, 3 doesn't get it done--perhaps there weren't cracks anywhere near Sweden!).

This leads to my broader question: You say that the ice melting near Sweden is implicit in the argument. But that sort of worries me: I didn't see that at all. I don't know anything about the ice age, or Sweden. I think (and I bet most people think) of Sweden as being cold--and if it's naturally cold than there would be LESS ice melt there after the ice age, no? And even if that's wrong, the argument says that lasting cracks appeared in SOME of of those parts under the stress of pressure from below.

Isn't it more reasonable (for a non-expert) to assume that cracks in the earth generally cause earthquakes? Isn't that what fault lines are?

So my question is, given all of these things that I feel I have to assume to get to the point you said was implicit, and all of the implicit assumptions I think are MORE obvious than the one you felt comfortable drawing, I feel like you must be looking at the problem differently, and that you are probably doing this because you know a lot more about how the LSAT is written.

Since dividing the things we can assume from the things we can't is such an important skill, I was hoping you could say a few general things about how to improve it.

I have thought of it like this. Try negating both B and D. If you negate D, the argument fails miserably, because if earthquakes are not caused by the cracking of the crust, than how could the melting of the ice, which caused the cracking of the crust, at all be linked to causing earthquakes. If you negate B, this argument can still work. A negation of B could be there are not various areas... Even if there are not various ones, that doesn't mean that Sweden couldn't have the cracks. This isn't to say that something that strengthens an argument is required, but if the negation of something presumed to strengthen the argument doesn't at least weaken the argument slightly, then I do not see how it's original form is truly strengthening the argument.

[kjjida9797]

Doesn't anyone think that this question is more like a sufficient assumption question?

The premise sentences in the stimulus say nothing about the relationship between occurrences of earthquakes and crakes. answer choice D connect the dots nicely.

[gaheexlee]

Doesn't anyone think that this question is more like a sufficient assumption question?

The premise sentences in the stimulus say nothing about the relationship between occurrences of earthquakes and crakes. answer choice D connect the dots nicely.

Correct answers to strengthen questions generally tend to identify and address assumptions between the premise and the conclusion to connect them. So yeap, you can think of them as being similar to sufficient assumption q answers (albeit weaker versions of them)!

[seychelles1718]

I think the original poster's explanation for D is not accurate. Can one of the instructors please confirm?

[ohthatpatrick]

Thanks, you're right. It was wonky. I edited it (and the explanation for E).

[PhoebeL747]

I eliminated B and E quickly and then eliminated A, was debating with C and D. I'd like to share my thought process:

I think (A) is just a premise booster. It reaffirms the idea that ice melting causes cracks but doesn't bridge it to the earthquake idea in the conclusion.
(C) shows more correlated evidence for this argument that uses correlation as evidence to draw a causal conclusion. Keep it for now.
(D) Directly tells you earthquake is CAUSED by cracks that was a result of ice melting. It strengthens much more by directly giving you the causation!

I personally think this strengthen question is an unusual one since typically there will be only one answer that strengthens. But I think (C) strengthen it a bit but not nearly as effective as (D). Therefore, (D) is the answer that MOST strengthens.

Any thoughts?

[AlexM563]

I agree that C is close to strengthening. However there is no connection in C from the ice age ending to cracks to earthquakes, and C is only a single case.

I am copying and pasting a wonderful response from Christine Defenbaugh to a question very similar to this question, except the correct answer strengthens the argument in a way that C in this question almost does. You will notice the correct answer in this question is multiple cases (vs just Canada) AND probably more important, the correct answer also shows all the important connections can be made in the reasoning)

This is Question 12, Preptest 71. Read at your own discretion.

"Thanks for posting, jm.kahn!

This is a very tricky question indeed!

First, a note about strengthen questions, in general. It's not actually correct to say that only one answer will strengthen even a teensy bit. That's usually true, but there are absolutely questions where one could make a case that other answers strengthened just a teeny tiny bit, while correct answer strengthens in a clear and substantive way.

Is that a judgment call? Yes it is, but when this occurs, it's never a hairsplitting difference between the strengthen value - it's always a wide gulf. The correct answer makes a bright, clear connection, while the incorrect answers only argument strengthen in the most miniscule ways.

You seem to understand why (B) solidly strengthens, but I'm going to lay that out for future readers before addressing your (totally valid!) concerns about (C) and (D)!

Since this is a strengthen question, we go straight to sorting out the core:

PREMISE:
Accepted prediction: Rocky mtns winter temps will increase, causing more of the precip to be rain (than was rain before)
CONCLUSION:
Predicted result: Rocky mtns snowpack will melt earlier (than it did before), causing more flooding (than before) and less storable water (than before)


Notice how the conclusion is not just a conclusion that in a certain situation (mild winter) a certain event will occur (flooding). Rather, this whole argument is a comparison. The premise is a comparison between the olden times (colder, more snow) and the future (warmer, more rain) for the same location. The conclusion is similarly a comparison between what used to happen in this particular location (later melting snowpack, less flooding, more storable water), and what will happen in this particular location (earlier melting snowpack, more flooding, less storable water).

If someone says "when there is plenty of rain, a river overflows" without any other information, then it seems a statement that says "on average, rivers located in regions with plenty of rain overflow more compared to one located in regions with less rain" strengthens the argument at least by bit.



Ahh, but this isn't what the conclusion proposed! The conclusion did not say that "when winters are mild, there is great spring flooding". It said, essentially "in this particular location, if the winter changes from colder to milder, it will likely result in more spring flooding than we had before". It's all comparative, not absolute!

(B) helps to strengthen this by providing a similarly comparative relationship in another similar region ("other mountainous regions"). We know that it's a comparative relationship because it says "after relatively mild winters" - that means relative to what that region normally experiences! And those regions experience more flooding and less storable water "than in those [same areas] after colder winters". So we are comparing the same location in mild winters versus cold winters, which is precisely the comparison we are attempting to make in the original argument!

(C) and (D) are both super tempting, as they both make comparisons between mild winters and cold winters. But notice that they are not comparing the same location.

(C) compares certain areas within the Rocky mtns where winters are relatively mild as compared to other areas with the areas that experience colder winters. Similarly, (D) compares regions of the world with mild winters to other regions of the world with harsh winters.

Because our stimulus was assessing a single location with varying winters, information about how other similar locations behave when their winters change is potentially extremely useful. But comparing totally different locations with totally different winters (and totally different all kinds of things, like elevation, humidity, average precipitation amounts, vegetation, topography, etc) is not really very useful to determine how this one particular location is going to behavior when the winter changes *there*.

Perhaps these mild-winter locations *always* have these effects, even when they have unusually cold winters! If that were true, then the flooding would probably be because of some other factor rather than the mildness of the winter. There's nothing in the data of these answer choices to indicate that it's the mild winter that is actually responsible, and there are a million other possibilities that spring to mind.

For the sake of completeness, I'll briefly address the remaining incorrect answers:
(A) We have no idea how an increase in the average amount of precipitation would affect anything. The argument focuses only on the impact of changing the proportions of rain/snow in the existing average precipitation.
(E) We have no idea whether the snowpack will be getting larger. In fact, it's possible it would get smaller with a milder winter, if the proportion of precipitation that is snow decreases. If that were true, this would arguably weaken the argument that more flooding will result!

Does this help clear things up a bit?"

[LeonC641]

I see that, because the cracks could have happened at any time since the Ice Age, D is a better choice B. However, it doesn't seem SO obvious to me that that rules B out. Here is how I understand the argument:

1. Melting ice at end of IA caused cracks in some parts of the earth's crust
2. Sweden experienced earthquakes at the end of the IA.
---
5. Therefore, the melting ice caused these earthquakes.

It seem to me that two obvious things are missing:

3. Cracks cause (or, better, generally cause) earthquakes.
4. There were cracks under Sweden.

D addresses 3. B addresses 4.

So is this the way to approach this problem: You say, look, I need both of these, but B does a lousier job of providing 4 than D does of providing 3, so D is more of a strengthener (even though, without 4, 3 doesn't get it done--perhaps there weren't cracks anywhere near Sweden!).

This leads to my broader question: You say that the ice melting near Sweden is implicit in the argument. But that sort of worries me: I didn't see that at all. I don't know anything about the ice age, or Sweden. I think (and I bet most people think) of Sweden as being cold--and if it's naturally cold than there would be LESS ice melt there after the ice age, no? And even if that's wrong, the argument says that lasting cracks appeared in SOME of of those parts under the stress of pressure from below.

Isn't it more reasonable (for a non-expert) to assume that cracks in the earth generally cause earthquakes? Isn't that what fault lines are?

So my question is, given all of these things that I feel I have to assume to get to the point you said was implicit, and all of the implicit assumptions I think are MORE obvious than the one you felt comfortable drawing, I feel like you must be looking at the problem differently, and that you are probably doing this because you know a lot more about how the LSAT is written.

Since dividing the things we can assume from the things we can't is such an important skill, I was hoping you could say a few general things about how to improve it.

I also agree with this poster Kdeclark. I was looking at some connection between the Sweden earthquake and the melting. So we want to provide my thoughts about why to me eventually B is really wrong, despite the fact of its correlation nature, and D is definitively right.

B certainly feeds something I was looking for. It's very tempting because: logically, what we need is sth helpful of making the argument more believable (i.e. strengthing) rather than making the argument valid or true. Generally, I believe a correlation can still strengthen a causation as long as such correlation makes the causation argument more possible. But the reason that I could confidentlly use to eliminate B was that for LSAC it seems that if we have a correlation which itself has many assumptions to make in order to be relevant with the causation, then such irrelevant, or far-fetched, correlation cannot be seen as a strengther. I feel this is the rationale LSAC likes to play with when designing LR questions, esp. those questions which requires the test-taker to fix or weaken an argument.

So, why D is 100 percent correct. Because it fixes two things the location gap and the link from the crack to Sweden earthquake ("SQ"). One, the conclusion in the stimulus is "it is likely that the melting of the ice contributed to these earthquakes." Note it needs a plausible reason to say there might be such causation. So looking at D, if SQ are generally caused by cracking of the earth’s crust near the earthquake site; then, we have can say most SQ happens near the cracking, regardless of some severe earthquake might still happens elsewhere.

Two, since it fixes the location link then, based upon this, D build a causation link from the cracking to the SQ (or at least, to a highly plausibility).

Hope the above helps. If there is anything wrong in my reasons, I will be happy to know that as well!

[YurikaC738]

B is very tempting to me. I think a reason to rule B out is "various areas". It's true that Sweden is in Northern Europe, but it does not necessarily need to be true that Sweden indeed shows cracks. A minor note, B also fails to mention the time that several cracks formed (what if it's after Ice Age?)