Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: During a massive eruption, all of the material may be ejected from a magma changer. Without support, the mountain above the empty chamber may collapse. This produces a huge caldera . Calderas are generally round, bowl-shaped formations ( Figure below ). Answer: magma
A:
Huge calderas form when the mountain above an empty chamber of what collapses?