Final answer:
A caldera is a large volcanic depression formed when a volcano collapses into a now-empty magma chamber, often following a significant volcanic eruption.
Step-by-step explanation:
A caldera is a volcanic depression much larger than the original crater, formed when the volcano collapses into a vacated magma chamber. An example of a well-known caldera is Crater Lake in Oregon. The formation of a caldera can occur after an eruption as the magma chamber empties and cannot support the weight of the volcanic structure, leading to a collapse. This feature is different from other volcanic structures like lava domes,
which are formed from viscous lava that spreads out, or cinder cones that are typically smaller and composed of volcanic debris. Stratovolcanoes are large, conical volcanoes built up by many layers of hardened lava and tephra, and may include a caldera at their summits, like the one found on Sif Mons on Venus.