What IS a supervolcano?

Supervolcanoes may be hot in the media but what are they really?

 

The word ‘supervolcano’ often appears in the media with threats of a global humanitarian crisis and the end of modern civilisation, but first thing’s first: what IS a supervolcano?

A supervolcano is defined as being a volcano that has experienced a large eruption that produced 1,000 km3 of rock (known as the Dense Rock Equivalent or DRE).

Comparison of the volumes of material erupted by different eruptions, those that produced more than 1,000 km3 were ‘super-eruptions’ Credit: USGS

By erupting such a large volume of material the volcano will commonly then collapse in on itself and create a caldera. This is why these eruptions are sometimes called ‘caldera-forming eruptions’ within the volcanological community.

A caldera is bound by faults and is not like a normal volcanic crater which is produced when material is blasted outwards from a vent or there is smaller-scale subsidence.

Some of the best examples of calderas include, 1. Crater Lake, USA. 2. Mount Somma, in which Vesuvius has subsequently grown, Italy. 3. Krakatau, Toba and Tambora in Indonesia. 4. Lake Taupo, New Zealand. 5. Las Cañadas, a series of at least 3 overlapping calderas in which Teide has subsequently grown, Tenerife. However, many of these calderas were produced by very large eruptions, but did not necessarily produce 1,000 km3 of material to classify them as super-eruptions.

Crater Lake, Mount Mazama
Crater Lake, a caldera formed by the eruption of Mount Mazama, USA. Credit: S.Wanmer 2015

 

 

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