LSAT Explanation PT 26, S2, Q6: The largest volcano on Mars rises

LSAT Question Stem

If the statements above are true, which one of the following must also be true on the basis of them? 

Logical Reasoning Question Type

This is a Must Be True question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

Alright, let's break down the passage and the question. The passage tells us that the largest volcano on Mars is much larger than any volcano on Earth could be, even if Earth had the same low gravity as Mars. This is because Earth's crust, despite having a similar composition to Mars', is too thin to support such a large volcano. The question is a Must Be True (MBT) question, asking us to determine which statement must be true based on the information given in the passage.

Before we dive into the answer choices, let's simplify the passage with an example. Imagine Earth and Mars as two tables made of the same material. Earth's table has thinner legs, while Mars' table has thicker legs. Even if we made the objects on Earth's table lighter (like reducing gravity), Earth's table still couldn't support a very heavy object (like a large volcano) because its legs are too thin.

Now, let's analyze the answer choices:

a) The surface of Mars is less subject to forces of erosion than is the surface of the Earth.

- This answer choice is not supported by the passage. Erosion is not mentioned or implied.

b) The highest volcanoes on Mars occur where its crust is thickest.

- While this may seem logical, the passage does not provide enough information to conclude that this must be true.

c) On average, volcanoes on Mars are higher than those on Earth.

- The passage only discusses the largest volcano on Mars, not the average height of all volcanoes. We cannot conclude this statement as true based on the passage.

d) The crust of Mars, at least at certain points on the planet, is thicker than the crust of the Earth.

- This answer choice is correct. The passage tells us that Earth's crust is too thin to support a large volcano like the one on Mars, so it must be true that Mars' crust is thicker, at least in some places, to support such a large volcano.

e) At least some of the Earth's volcanoes would be larger than they actually are if the Earth's crust were thicker than it is.

- This answer choice is tempting, but it is not necessarily true. While a thicker crust might allow for larger volcanoes, there could be other factors that prevent Earth's volcanoes from being larger. The passage does not provide enough information to conclude that this statement must be true.

So, the correct answer is (d). The crust of Mars, at least at certain points on the planet, is thicker than the crust of the Earth. This conclusion is based on the fact that Earth's thinner crust cannot support a large volcano like the one on Mars, even with reduced gravity.