A caldera is a crater formed after the eruption of a volcano. The caldera is formed when the volcano collapses into itself.
Volcanoes are impressive forces of nature with the power to wreak enormous destruction when they erupt. One sign of that power is a caldera, which is a crater formed after a volcano has erupted and collapsed into itself. Some of the more ancient calderas formed mountains and valleys in the Rockies and elsewhere. A related word in English is cauldron, whose modern meaning (a vessel for hot liquids) can remind us of the molten lava of a volcano.