LSAT 133 | Section 4 | Reading Comprehension: Q18

RC Question 18 Explanation

DISCUSSION: You can and should prove the right answer by referring to the passage.

Basalt contains magnetite. Magma turns into basalt. You can basically view all three terms as interchangeable for the purpose of answering this question. Magma becomes basalt, which takes on the Earth’s current polarity as it hardens.

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1. CORRECT. Basalt takes on the polarity the Earth has at the time the basalt forms. The youngest basalt is forming as we speak. So the youngest basalt has the Earth’s current polarity. See lines 20-23.
2. Lines 20-23 simply say that basalt takes on the current polarity of the Earth. The passage doesn’t say that “most but not all of basalt” takes on current polarity. This answer is totally unsupported.
3. The passage never says this. Maybe many rocks have magnetite.
4. Not all grains are the same size. The passage never says that magnetite grains are the same size as grains of sand.
5. The passage never says this. Maybe magnetite grains are very large.