#21 - Nuclear reactors are sometimes built in "geologically quiet" regions,

[Amber Thomas]

Hi Morgan!

We can actually cite the stimulus in drawing this conclusion about fault lines: "since no minor fault in a geologically quiet region produces an earthquake more often than once in any given 100,000-year period, it follows that of all potential nuclear reactor sites in such a region, those that are least likely to be struck by an earthquake are ones located near a fault that has produced an earthquake within living memory."

It is explicitly stated that minor fault lines VERY RARELY produce earthquakes, therefore, it is unlikely that nuclear reactors placed near minor fault lines will experience an earthquake. We can infer from this, and the fact that scientists specifically put their nuclear reactors in areas with minor faults, that major fault lines or plate boundaries would produce more earthquakes or "geological noise." It logically follows that one would want their nuclear reactor away from an area that has frequent earthquakes, and in an area with relatively infrequent earthquakes.

I hope this helps!

[Adam Tyson]

I don't think the stimulus requires us to know anything about fault lines or earthquakes, Morgan2cats. We just have to analyze the structure of the argument. Let's change the topic slightly to illustrate:

Some cities have a lot of coffee shops, and some of those coffee shops take advantage of their customers by tricking them into buying extra stuff that they don't need and that aren't good for them. Other coffee shops in these cities are totally honest and never do that. So, if you live in one of these cities and you are concerned about being tempted into spending too much money on coffee, the best place to live is near an honest coffee shop.

This argument fails to consider that there might be places in the city that aren't near ANY coffee shops, and that those might be even better places to avoid temptation to spend too much on coffee. To fix that flaw, the author must assume that if you live in one of these cities, you are going to have to live near at least one coffee shop. Similar argument structure, same assumption, different topic, and no outside knowledge required!

[ellieeiff4]

Hi Powerscore,

Could someone please assist with explaining this question? I think I need more clarity in how to approach Necessary Assumption questions, especially in a difficult stimulus like this one.

I selected answer choice D - "Nuclear reactors that are located in geologically quiet regions are built to withstand at least one but not necessarily more than one earthquake of minor to moderate force." I tried the Assumption Negation test on this one - "Nuclear reactors that are located in geologically quiet regions are NOT built to withstand at least one but not necessarily more than one earthquake..."
Looking back, I know that this does not necessarily weaken the argument (i.e. how would the ability of the nuclear reactor sites to withstand an earthquake support the idea that those sites near a fault with an earthquake produced within living memory are least likely to be struck by an earthquake?); however, I think I chose this answer because I had a hard time identifying even a gap in the argument here.

I chose C after another look at the answer choices - I vaguely understand why it is correct. When negated ("In GQ region, NOT every potential nuclear reactor site is near at least one minor fault."), I understand now that this would weaken the argument (i.e. there could be sites near no fault and thus no earthquake), but I was not able to make this leap during the section.

Thanks for your help!

[Amber Thomas]

Hi ellieeiff4!

Let's start by breaking down our stimulus:

Premise 1: Nuclear reactors are built in "geologically quiet" regions that are distant from plate boundaries and only contain minor faults.
Premise 2: Minor faults in "geologically quiet" regions produce earthquakes no more than once per 100,000 year period.
Conclusion: Therefore, it follows that the nuclear reactors in these regions near faults that have produced an earthquake in living memory are the least likely to be struck.

What's our line of logic here? Since these minor faults produce earthquakes only once every 100,000 years, if a minor fault has experienced an earthquake in living memory, that means it likely won't have another earthquake for a very long time.

So, what assumption needs to be made so that our conclusion logically follows?

Answer Choice D states: "Nuclear reactors that are located in geologically quiet regions are built to withstand at least one but not necessarily more than one earthquake of minor to moderate force."

This is actually out of scope-- our stimulus doesn't mention anything about whether or not these nuclear reactors are able to withstand any amount of earthquakes (one or more). It's not relevant to our conclusion.

Answer Choice C states: "In a geologically quiet region, every potential nuclear reactor site is near at least one minor fault."

This works with our stimulus! Let's recall: geologically quiet regions only contain minor faults. However, that does not mean that they are everywhere throughout the region-- certainly, there are areas within geologically quiet regions with no faults. So, it follows that a nuclear reactor near a minor fault (even one that has experienced an earthquake recently) is more likely to experience an earthquake than a nuclear reactor near no faults.

So, for our conclusion to logically follow, every nuclear reactor in a geologically quiet region would need to be located near a minor fault.

I hope this helps!