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 any volcano capable of producing a volcanic eruption with an ejecta volume greater than 1,000 km3 (240 cu mi). This is thousands of times larger than normal volcanic eruptions. Supervolcanoes can occur when magma in the mantle rises into the crust from a hotspot 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 is the case for the Yellowstone Caldera). They can also form at convergent plate boundaries (for example, Toba).

Although there are only a handful of Quaternary supervolcanoes, supervolcanic eruptions typically cover huge areas with lava and volcanic ash and cause a long-lasting change to weather (such as the triggering of a small ice age) sufficient to threaten species with extinction.

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