caldeira

Caldeira (caldera) is a large volcanic crater formed by the collapse of land following the withdrawal or evacuation of magma from a chamber during or after an eruption. The term is synonymous with the English word caldera; its etymology traces to Spanish and Portuguese for cauldron.

Most calderas form when a magma chamber partially empties, causing the overlying roof to collapse and create a roughly circular or elliptical depression. Eruptions can be explosive, ejecting large volumes of magma and ash; later magma recharge can refill the caldera or drive resurgent volcanism, producing domes and secondary vents.

Calderas vary in size from a few to more than 30 kilometers in diameter; the floor may host lakes, volcanic deposits, or new lava domes. Nested calderas occur when a second collapse follows the first. Calderas with active hydrothermal systems are common and can drive hot springs and fumaroles.

Notable calderas include Yellowstone Caldera in the United States, Crater Lake in Oregon, Santorini in Greece, and the Taupo caldera in New Zealand. Calderas are monitored for volcanic hazards due to potential renewed activity and their ability to influence regional geology, climate, and land use.