LSAT 5 | Section 1 | Logical Reasoning: Q17

LR Question 17 Explanation

QUESTION TEXT: Sedimentary rock hardens within the earth’s crust as layers…

QUESTION TYPE: Weaken

CONCLUSION: The layer of iridium is evidence that a meteorite struck Earth sixty million years ago.

REASONING: Iridium is rare on earth, but meteorites are rich in iridium.

ANALYSIS: There are alternate explanations for almost all things. We need to find some other way of explaining the layer of iridium.

___________

1. So? That’s not inconsistent with a layer of iridium forming.
2. And…? The argument did not depend on the layer of iridium forming quickly.
3. This shows that the dating technique is valid, and strengthens the argument.
4. CORRECT. This shows that iridium could have come from volcanoes and not meteorites. The argument is weakened.
5. This provides additional evidence that the iridium could have been deposited by a meteorite. The argument is strengthened.

Recap: The question begins with “Sedimentary rock hardens within the earth’s crust as layers”. It is a Weaken question. Learn how to master LSAT Weaken questions on the LSAT Logical Reasoning question types page.