Supervolcanoes

Grand Prismatic Spring, Yellowstone National Park

The term supervolcano was first used in a TV documentary to describe eruptions of more than 1,000 cubic kilometres of magma. Such volcanoes are devastating, but very rare. The last one happened at Toba in Sumatra, Indonesia, 74,000 years ago.

The active volcanic system at Yellowstone National Park has resulted in super-eruptions - the most recent happened 640,000 years ago. Yellowstone's volcanism is powered by magma rising from a hotspot. The relatively thick continental crust causes large amounts of magma to build up underground.

In the near future, a super-eruption at Yellowstone or anywhere else is extremely unlikely. We are far more likely to encounter composite volcanoes, shield volcanoes, and cinder cones.

Image: Grand Prismatic Spring, one of the many thermal springs in the volcanically active Yellowstone National Park (credit: Douglas Faulkner/SPL)

Introduction

Grand Prismatic Spring, Yellowstone National Park Supervolcanoes

TV clips (3)

Supervolcanoes

A supervolcano is a volcano capable of producing a volcanic eruption with an ejecta mass greater than 1015 kg (1012 t). Supervolcanoes occur when magma in the mantle rises into the crust but is unable to break through the crust, and pressure builds in a large and growing magma pool until the crust is unable to contain the pressure. This can occur at hotspots (for example, Yellowstone Caldera) or at subduction zones (for example, Toba). Another setting for the eruption of very large amounts of volcanic material is in large igneous provinces, which can cover huge areas with lava and volcanic ash, causing long-lasting climate change (such as the triggering of a small ice age or global warming), which can threaten species with extinction. The Oruanui eruption of New Zealand's Taupo Volcano, the world's most recent supereruption, had a Volcanic Explosivity Index of 8.

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