Q21 - Nuclear reactors are sometimes built

[mcrittell]

Can you please walk me through this?

[jiyoonsim]

A) General dangerous isn't the point here - the point here is earthquake and fault and likelihood of getting struck.

B) How to make decisoin about nuclear sites - primary determinant - has nothing to do with the given stem.

C) If you put the C) into the opposite way, it wobbles the entire argument. What if some sites that are in the geologically quiet region AND have zero faults around them? Then those sites are the least likey to have earthquake struck, not the sites near the minor faults.

D) Both the force of eartuquake and the number of eartuquake has nothing to do with the argument here.

E) If we are to assume E, then the faults can now cause earthquakes more than once!!(+1) The stem says "no more than once (-1)." This option runs against the argument.

[giladedelman]

Yes, nice explanation!

As always, the core is key:

P: no minor fault in quiet region produces more than one earthquake per 100,000 years --> C: nuclear sites least likely to get hit by an earthquake are the ones located near faults that have recently produced an earthquake.

I have to admit, at first, I couldn't tell exactly what was missing from this argument! But when I went through the answer choices, it became clear: the conclusion says that the sites least likely to get hit by earthquakes are the ones located nearest these faults. That makes a kind of sense, because those faults shouldn't produce a quake for almost 100,000 years. But wait a minute: what if there were sites that aren't near any faults? Maybe those would be even less likely to get hit by an earthquake.

So that's why (C) is right: the argument assumes that every potential nuclear site is near a fault.

[nicholasasquith]

Just wanted to add to why I feel (E) is incorrect, because I don't feel that it runs counter to the argument like the first responder mentioned.


I actually picked E and it was because I couldn't find the gap in the argument (That they mention only minor faults in our "quiet" regions and don't rule out/explain the likelihood of quakes elsewhere within it). But in either case, when I looked at E again I realized it doesn't give us any new information.

We already know there's a 1/100,000 chance of a quake at a minor fault, and we already know the safest faults are supposed to be next to the faults that recently had a quake (This is the conclusion), so whether or not we need to assume minor faults do indeed produce a quake every 100,000 years is irrelevant. Our conclusion is telling us the faults of interest have already been quaked recently.

[austindyoung]

I see the reason sated above for why (C) was chosen. I chose it for another reason. Term shift. Ya'll tell me what you think.


Argument states: Because no minor faults have had earthquakes in 100,000 years we can conclude that ALL potential nuclear reactor sites that are least likely to get rocked are those next to a fault that has had an earthquake within living memory.

Notice the term shift? The argument goes from "minor faults" and makes a conclusion about "a fault" that has produced an earthquake in living memory. Similar, but in LSAT land it's different enough.

I saw (C) as protecting the conclusion. Making sure that the faults mentioned the second time fall within the purview of the safety guaranteed by "minor faults."

[ohthatpatrick]

I like your suspicion, but I don't think what you're addressing is a valid gap in this argument.

The conclusion says "of all potential reactors in such a region ..."

What type of region? (I had to look back for this when I read it the first time)

"Geologically quiet" regions -- defined as 'distant from plate boundaries' and 'containing only minor faults'.

So when the conclusion says "a fault", we already know it's must be a "minor fault" because those are the only types of faults in such a region.

You also somewhat distorted the 100,000 year fact. The argument states that minor faults never have more than one quake in any 100,000 year period.

You said "no minor faults have had earthquakes in 100,000 years".

Those are two different statements, but maybe you were just typing quickly and didn't really mean what you typed.

Anyway, thanks for offering your take on this!

[austindyoung]

Well looks like I kinda butchered that one! But, now I see what you're saying about there not being a term shift because of the "only" in the argument! Thank you.

The part about the 100,000 years was a sloppy-paraphrase on my part.

Thanks again, I see why there's not a term shift going on!

[griffin.811]

I went with E on this one.

I dismissed C as a premise booster. I was thinking if there is an earthquake in a region, it doesn't matter if the reactor is near the fault or not, it will still feel the earthquake.

How are we to assume any different? I see that the quakes are described as minor, but even so, it's an earthquake. Additionally no degree is stated as to what qualifies as a "minor" quake, nor is there any clue as to how big a "region" is. Is it northeastern Cali, Northern Cali, Cali, West Coast etc...

I went with E because in the case that there is a reactor near a spot that has a quake only once in every 10 million years, this at least could destroy the argument that those least likely to be effected are thos that have had a quake in living memory.

Thoughts?

[ohthatpatrick]

It's true that even if you're not near a fault, you might still feel an earthquake. But would you feel it as intensely as you would if you were right near the fault? No. That's within the scope of common sense that LSAT expects us to have.

Being near the epicenter is a completely different experience from being many miles away, where you just feel a little ripple in the ground.

I know many students at some point think or hear "we're not supposed to use outside knowledge or common sense", but it does not say that in LR. It says, at the beginning of every LR section, that we "should not make assumptions are are by commonsense standards superfluous, implausible, or incompatible with the passage".

Which is a safer (note: not "safe") place to be in: right by the fault of an earthquake, or NOT near the fault of an earthquake?

We're allowed to answer that question using commonsense, and our answer is relevant, plausible, and compatible.

In terms of (E), I assessed it based on its similarity to the statistic that was cited in the evidence.

If I'm told that "no fault produces an earthquake more than once in any given 100,000 year period", does that mean I'm assuming that "each fault DOES produce AT LEAST ONE earthquake in every 100,000 year period"? No. It's an extreme statement that the author doesn't have to assume.

I could truthfully say that "no friend of mine has been President of the US more than once". Does that mean I'm assuming that "each friend of mine has been US President at least once"?

I see where you were going with your story, but it doesn't quite give the certain objection to the conclusion that (C) does.

And jumping to the idea that "some sites only have an earthquake once every 10 million years" IS what LSAT means by a "superfluous" assumption. We're creating our own story there.

Hope this helps.

[zacharymosesdavid]

The reason this question is tricky is because the information that is essential to answering the question correctly is located in what seems to be background information, not a premise. The first sentence states that nuclear reactors built in geologically quiet regions are built there because such regions "only contain minor faults," meaning that if the region has a fault, it's a minor one "” it may be the case that a geologically quiet region doesn't have any faults! That's why C has to be assumed.

I originally was tempted by E as well, because I thought that just because a minor fault produces an earthquake no more than once in any given 100,000 year period, it might be the case that some faults produce earthquakes no more than once every 1,000,000 year period, and that therefore it's incorrect to say that those faults least likely to be struck again are ones that have had an earthquake recently unless all faults do actually have one every 100,000 years. Otherwise a fault whose chances of producing an earthquake no more than once every million years would still be less likely to have an earthquake than a fault whose chances of producing an earthquake was one in every 200,000 years but had a quake recently. So it would be helpful to assume E, because if every fault did produce a quake every 100,000 years, then it's more likely that a fault that recently had a quake are least likely to be struck again in the near future.

I agree that C must be assumed. But I'd appreciate some more pointed dialogue about E. One thing that tipped me off about it was the phrase "at least once," which implies that it could be more than once (which we know it cannot). If it had said "once" or "exactly once," I would have picked it.

[ttunden]

Hello

I can see why C is correct however when I did this initially, under timed conditions, I tried the negation test. When negating answer choice C, I came up with " in a geologically quiet region, NOT every ( some ) potential nuclear reactor site is near at least one minor fault. My negation did not destroy the argument so I eliminated it.

Was my negation incorrect? if I were to not negate answer choice C, I can see how it is the right answer choice but in timed conditions I did the negation test. The obvious assumption I was looking for was an answer choice stating there has been an earthquake that has occurred within living memory. Something like that.

I would really appreciate any advice regarding the negation for answer choice C.

Thanks

[Alvanith]

I was very tempted by E but finally I went for C. This is my take for this question:

P: the minor faults in the quiet region produces ≤1 earthquake in any 100,000-year period.

C: The sites least likely to be struck by an earthquake in such quiet region are those located near faults that have recently produced an earthquake.

Thoughts:
Why the sites least likely to be struck have to be near faults that have recently produced an earthquake? Are there any sites in such region are located near no faults? Are there any sites located near faults that produce no earthquake at all, if possible? Normally these sites could be even less likely to be struck than those located near faults that have recently been hit by an earthquake.

Therefore, we probably need to assume:
(a) no sites are located near no faults, which means every site is located near at least one minor fault.
(b) no sites are located near faults that are earthquake-free.

The correct answer choice C directly hit on the assumption (a).

Now let's look at the answer choice E.
It looks like E is trying to attack on the assumption (b), but fails.
First, the conclusion is the sites least likely to be struck are those near faults hit by an earthquake recently. Whatever the rate of those earthquake faults producing earthquakes, like no more than once in 200,000 years or even less frequent, we still can conclude the least likely ones are those hit by an earthquake recently. So we don't have to assume the rate is ≥1 in every 100,000 year.
Second, we don't need a general statement that all earthquake faults in such quiet region produce earthquakes at such a rate. Instead, we probably need the faults near sites produce earthquake. Just a illustration:
Say there are 1000 minor faults in this quiet region, but only 200 of those 1000 faults have a nuclear site located nearby. For this question, we only need assume those 200 faults produce earthquake, but we don't care about how frequent those other earthquake faults produce earthquakes.
This difference is significant enough to get rid of E.

Correct me if I am wrong. Thanks:)

[pewals13]

Core:

Geologically quiet regions are distant from plate boundaries and contain only minor faults
+
No minor fault in a geologically quiet region produces an earthquake more often than once in any given 100,000-year
period
=>
Of nuclear reactors in quiet regions, those least likely to be struck by an earthquake are ones located near a fault that has produced an earthquake within living memory

Assumptions:

What about nuclear reactors within a quiet zone not located near a fault line at all? Wouldn't those be safer?

Answer Choices:

(A) Out of scope (too strong): This does not need to be true order for the conclusion to be true

(B) Out of scope (too strong): Earthquake likelihood does not need to be the primary determinant of site safety in order for the conclusion to hold

(C) CORRECT: Consider the negation- "In a geologically quiet region, NOT every potential nuclear reactor site is near at least one minor fault." If some potential sites could be near no fault at all (keep in mind that the only faults that exist in quiet zones are minor faults), then those near recently stricken sites are not the safest within the zone. Those located near no fault would be at least equally safe. The conclusion no longer holds.

(D) Out of scope (relevance): It doesn't matter whether the reactors were built to withstand 1 or 100 earthquakes, the core addresses whether reactor sites least likely to be stricken by an earthquake are those near fault lines that have produced one within living memory

(E) Out of scope (too strong): Tough one to eliminate. This is how I looked at it: whether the fault line produces an earthquake every 100,000 years or every 100 trillion, it doesn't change the fact that the faults least likely to produce an earthquake at a given moment in time are those that have produced one in living memory. Thus, the negation would not destroy the conclusion.

Final Notes:

Keep the precise wording of the conclusion inside your head at all times while evaluating the answer choices

[jiangziou]

When it says that the regions "contain only minor faults,", it means such regions contain at least one fault. No conditionality.
It's like those glasses contain only water". It means they have water in it.

The first sentence states that nuclear reactors built in geologically quiet regions are built there because such regions "only contain minor faults," meaning that if the region has a fault, it's a minor one "” it may be the case that a geologically quiet region doesn't have any faults! That's why C has to be assumed.

[a8l367]

Didn't get it.

Q:
The safest place to build is near a minor fault wich had earthquake, since it will not have it again in the following 100000 years.

Assumption (correct answer):
There is no region without minor fault. (as though such a region is safer by default)

But why we shoud assume that a region w/o minor fault is safer?
Morover, we know that in the region with minor fault you will not have earhtquake in 100000 for sure, so safeness is guaranteed