Which one of the following is most strongly supported by the passage?

Hunter on April 21, 2019

Why A?

Why is A right? I thought A was general for many reasons, and I don't see support for it in the passage. First, the ages of other rocks aren't even mentioned in the passage. So, even if could say the oldest submarine basalt rock, how could I make that jump to the rest of the rocks in the ocean? And how would I know that the rock closest to the continents are those furthest from the global mid-ocean ridge? I don't even have information of where mid-ocean ridge is located in the text. I mean am I supposed to assume that mid means middle of continents? I think there is more support for C. If I know magnetite locally distorts compasses on land, and magnetite is contained in the rock making up much of the ocean floor, than I have some reason to believe compass reading are more likely to be distorted at sea.

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Ravi on May 2, 2019


Happy to help. Let's take a look at both (A) and (C).

The question asks, "Which one of the following is most strongly
supported by the passage?"

(C) says, "Compass readings are more likely to become distorted at sea
than on land."

The problem with (C) is it's too general. It depends largely upon
where on land you are vs. where at sea you are. If you're near a bunch
of magnets on land, then your compass is going to be more likely to
get distorted. Thus, we can get rid of (C).

(A) says, "Submarine basalt found near the continents is likely to be
some of the oldest rock on the ocean floor."

From the passage, we have information about the evidence that supports
the ocean floor changing theory. Lines 30-40 tell us about the
mid-ocean ridge, and there we learn that the ocean floor is being
pulled apart along the ridge crest. New magma from deep within the
earth rises easily through these weak zones and eventually erupts
along the crest of the ridges to create new oceanic crust. From this,
we can infer that the newer rocks are near the crest of the mid-ocean
ridge (where the new magma comes up), and the older rocks are farther
away from the ridge and closer to the continents. Thus, (A) is the
correct answer, as it's strongly supported by lines 30-40 of the

Does this make sense? Let us know if you have any other questions!

Hunter on May 2, 2019

Thank you! It does make sense, and I see why C was too far a jump now.

Anna20 on August 10, 2020

Thanks for the above. I chose E here, and while I understand that there are only two polar possibilities (current and reversed), which flip-flop back and forth, I understood "any rock that exhibits present–day magnetic polarity was formed after the latest reversal of the earth's magnetic field" to mean just that - and even re-reading it, I still do. Obviously it's wrong, so I'm misunderstanding something here. Would you also be able to eliminate because it says "any".