Prior to 1965 geologists assumed that the two giant rock plates meeting at the San Andreas Fault generate heat through friction as they grind past each other, but in 1965 Henyey found that temperatures in drill holes near the fault were not as elevated as had been expected. Some geologists wondered whether the absence of friction-generated heat could be explained by the kinds of rock composing the fault. Geologists’ pre-1965 assumptions concerning heat generated in the fault were based on calculations about common varieties of rocks, such as limestone and granite; but “weaker” materials, such as clays, had already been identified in samples retrieved from the fault zone. Under normal conditions, rocks composed of clay produce far less friction than do other rock types. In 1992 Byerlee tested whether these materials would produce friction 10 to 15 kilometers below the Earth’s surface. Byerlee found that when clay samples were subjected to the thousands of atmospheres of pressure they would encounter deep inside the Earth, they produced as much friction as was produced by other rock types. The harder rocks push against each other, the hotter they become; in other words, pressure itself, not only the rocks’ properties, affects frictional heating. Geologists therefore wondered whether the friction between the plates was being reduced by pockets of pressurized water within the fault that push the plates away from each other 1 1. The passage suggests which of the following regarding Henyey’s findings about temperature in the San Andreas Fault? (A) Scientists have yet to formulate a definitive explanation for Henyey’s findings. (B) Recent research suggests that Henyey’s explanation for the findings should be modified. (C) Henyey’s findings had to be recalculated in light of Byerlee’s 1992 experiment. (D) Henyey’s findings provided support for an assumption long held by geologists. (E) Scientists have been unable to duplicate Henyey’s findings using more recent experimental methods. 2 2. The passage is primarily concerned with (A) evaluating a method used to test a particular scientific hypothesis (B) discussing explanations for an unexpected scientific finding (C) examining the assumptions underlying a particular experiment (D) questioning the validity of a scientific finding (E) presenting evidence to support a recent scientific hypothesis 3 3. The passage mostly agree that Henyey’s findings about temperature in the San Andreas Fault made the greatest contribution in that they (A) revealed an error in previous measurements of temperature in the San Andreas Fault zone (B) indicated the types of clay present in the rocks that form the San Andreas Fault (C) established the superiority of a particular technique for evaluating data concerning friction in the San Andreas Fault (D) suggested that geologists had inaccurately assumed that giant rock plates that meet at the San Andreas Fault generate heat through friction (E) confirmed geologists’ assumptions about the amount of friction generated by common varieties of rocks, such as limestone and granite 4 4. According to the passage, Henyey's findings in 1965 were significant because they (A) revealed an error in previous measurements of temperature in the San Andreas Fault zone (B) indicated the types of clay present in the rocks that form the San Andreas Fault (C) established the superiority of a particular technique for evaluating data concerning friction in the San Andreas Fault (D) suggested that geologists had inaccurately assumed that giant rock plates that meet at the San Andreas Fault generate heat through friction (E) confirmed geologists' assumptions about the amount of friction generated by common varieties of rocks, such as limestone and granite Source : GMATPrep Default Exam Pack

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Prior to 1965 geologists assumed that the two giant rock plates

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Utkersh

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16 May 2023, 15:02

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I'm still not able to understand how is D the correct answer for Q-3. The pressure and types of rocks just affect the amount of friction. But it is infact at the end, friction that generates the heat right? So how is it inaccurate to say that friction generated heat?

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Question 3

Utkersh

As you point out, it may be hard to defend the general statement that "friction generates heat." But is that exactly what (D) is saying?

Quote:

3. The passage mostly agree that Henyey’s findings about temperature in the San Andreas Fault made the greatest contribution in that they
(D) suggested that geologists had inaccurately assumed that giant rock plates that meet at the San Andreas Fault generate heat through friction

Notice that (D) isn't claiming that Henyey's findings suggest that "friction does not generate heat" generally speaking. Rather, it asks us to agree that Henyey's findings suggested that geologists were wrong to assume that "giant rock plates that meet at the San Andreas Fault generate heat through friction."

So did Henyey's findings call this assumption into question? It would seem so. After his findings were made, geologists began to wonder whether there was an "absence of friction-generated heat." In other words, they questioned whether heat was created through friction in this particular instance. Maybe friction can generate heat, but in this case, there was no friction between the rocks. In which case, there wouldn't be any heat generated through friction.

The rest of the passage explores this question. First, it considers whether rock types could explain the absence of heat found by Henyey. Next it considers whether pressurized water could explain the absence of friction-generated heat.

Overall, since Henyey's findings suggest that geologists inaccurately assumed that the rock plates of the San Andreas fault generate heat through friction, (D) is correct.

I hope that helps!

kartickdey

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GMATNinja Although I admit that the option D is the best option but ideally I think that option is not right. From the passage whatever I comprehended is that Henry's findings did not suggest that geologists had inaccurately assumed that giant rock plates that meet at the San Andreas Fault generate heat through friction; rather it suggested that there may be a third factor which is resposible for the reduction in the expected temperature from the assumption of the earliest geologist but it does not mean that heat was not generated through friction. what is yout opinion on this matter.

GMATNinja

Question 3

Let’s take a look at (D):

All that (D) says is that Henyey’s work SUGGESTED that geologists had inaccurately assumed that heat was generated through friction. You’re correct to note that it is Byerlee’s work that confirms this suggestion by finding that even weaker materials would produce friction under such pressure. But Henyey is the first to suggest that the geologists’ assumption may not be correct. Ultimately, Henyey’s work proves important because it turns out that the geologists, indeed, were wrong to assume that the giant rock plates generated heat through friction. And it was Henyey’s work that provided the basis for Byerlee’s tests to confirm that geologists were wrong. Therefore, (D) is correct.

Honestly, I don’t love (D) when I first look at it either. But it is true that Henyey’s work is the first to SUGGEST that the geologists’ assumption may be incorrect. And this question is an excellent example of where finding four wrong answers, rather than one right answer, can be immensely beneficial. It may be hard to see why (D) is correct. But it’s easy to see why the other four answers are incorrect, making (D) the least wrong answer. And on that basis, we can choose (D).

I hope that helps!