New insights into caldera formation - what precedes volcanic eruptions?

Calderas (from Latin caldaria - pot, cauldron) are circular or elliptical depressions on the Earth's surface, often covered with water (so-called caldera lakes), formed by gravity-controlled subsidence of volcanoes into the underlying magma. This process has been associated with catastrophic volcanic eruptions and the ejection of huge quantities of volcanic ash into the atmosphere in the case of large calderas such as Lake Toba in Indonesia or Yellowstone in the USA.

While the final manifestations of these volcanic eruptions can be easily observed on the Earth's surface and are thus relatively well studied, the physical conditions and causes of caldera formation and the mechanisms of brittle failure of the underlying rocks are still a mystery. The aim of a long-standing project by a joint team from the Faculty of Science of the UK and the Czech Technical University in Prague was to understand under what conditions gravitational collapse of calderas occurs and what effect the shape of the underlying magma mantle, its size and depth in the Earth's crust has. New research has shown, using a combination of geological data and mathematical modelling, that magma pressure oscillations lead to intense brittle failure in places, and therefore to a reduction in the strength of the magma crust ceiling, but that collapse and caldera formation can only occur under specific conditions.

Somr, M., Žák, J., Kabele, P., Tomek, F., 2023. Analysis of fracturing processes leading to caldera collapse. Earth-Science Reviews 241, 104413, doi: 10.1016/j.earscirev.2023.104413.