Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: The Permian Period ended with Earth's second mass extinction. During this event, most of Earth's species went extinct. It was the most massive extinction ever recorded. It's not clear why it happened. One possible reason is that a very large meteorite struck Earth. Another possibility is the eruption of enormous volcanoes. Either event could create a huge amount of dust. The dust might block out sunlight for months. This would cool the planet and prevent photosynthesis. Answer: mass extinction
What happened to earth's species during the permian period?