Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: deep sea trenches : Trenches are found in the sea. Some are near the edges of continents. Trenches are found near chains of active volcanoes. An example is the line of the very deepest blue, off of western South America. Answer: volcanoes
A:
What kind of mountainous formation can often be found near trenches?