calderas

Calderas are large volcanic depressions formed when the magma chamber beneath a volcano empties during a major eruption or when the ground above the chamber collapses after an eruption. Calderas are typically several to tens of kilometers across and can be circular, elliptical, or irregular in outline. Many calderas host lakes, volcanic domes, or hydrothermal fields, and some preserve concentric ring faults or resurgent uplift within their floors.

Formation and evolution: The principal mechanism is the collapse of the chamber roof following the withdrawal of magma. Subsequent intrusions and eruptions can create renewed activity within the caldera, including the growth of resurgent domes and the formation of secondary calderas. The structure can remain volcanically active for hundreds of thousands to millions of years, punctuated by large eruptions.

Examples and significance: Famous calderas include Yellowstone (United States), Crater Lake (United States), Long Valley (United States), Toba (Sumatra, Indonesia), Tambora (Sumbawa, Indonesia), Santorini (Greece), Krakatau (Indonesia), and Taupo (New Zealand). Calderas are indicators of past extreme magmatic behavior and are monitored for potential future hazards; large caldera-forming eruptions have significant societal and climatic implications and pose hazards to nearby populations.