A caldera is a large cauldron-like pit that forms following the collapse of a volcano. They are sometimes also known as crater lakes. The word comes from the Spanish language, and its original meaning was “cooking pot”. Calderas can be found on every continent except for Antarctica.
The largest recorded caldera in the world is at Toba, Sumatra, Indonesia. It has an area of approximately 18,000 km2 (7,100 mi2) and is believed to have been formed around 75,000 years ago when a supervolcano erupted. This event was so large that it is thought to have caused a global volcanic winter and possibly triggered a genetic bottleneck in humans.
Calderas can form through several mechanisms: explosive eruptions that empty the magma chamber underneath the volcano; gradual emptying of the magma chamber by lava or pyroclastic flows; or by dike injections that plug up the magma conduit (the pathway from deep within Earth to the surface). Once formed, calderas can become sites of intense hydrothermal activity due to all of the heat released from below ground. This can lead to geysers, hot springs, fumaroles (steam vents), and deposits of minerals such as silica sinter terraces.