Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Problem:Passage: Composite volcanoes are common along convergent plate boundaries. When a tectonic plate subducts, it melts. This creates the thick magma needed for these eruptions. The Pacific Ring of Fire is dotted by composite volcanoes. Answer: it melts
Solution:
What happens to a tectonic plate when it subducts?