Passage Summary: While the common theory of earthquakes seems logical, it doesn't account for why we don't see the heat that should be produced when massive rock plates rub together.

Conclusion: The prevailing theory that earthquakes are caused by plates sliding past each other fails to explain at least one significant phenomenon.

Reasoning: The friction from plates sliding should generate massive amounts of heat, yet no such heat increases have been detected following earthquakes.

Analysis: This is an 'Identify the Conclusion' task, so we must pinpoint the author's main point rather than critiquing the logic. The author introduces the current theory only to point out a 'mystery' or a flaw in its explanatory power. The evidence regarding the lack of heat is used specifically to support the claim that the theory is incomplete. Look for an answer choice that focuses on the theory's inability to explain the missing heat, as that is the primary thrust of the passage.