volcanic sink

A caldera is a large, bowl-shaped volcanic depression, typically over a kilometer in diameter. It forms when the top of a volcanic cone collapses into the void left by the ejection of magma during a violent eruption. The diameter of a caldera is often many times that of the original volcanic vent.12

Subsequent, smaller eruptions can create new cones on the caldera floor. Sometimes, these depressions fill with water, forming lakes like Crater Lake in Oregon. Other volcanic depressions, which are more angular and irregular, are called volcano-tectonic depressions. Their shape is influenced by tectonic structures like faults and joints in the Earth's crust, and their collapse is also linked to the rapid extrusion of lava.12