Supervolcanoes are on a much bigger scale than normal volcanoes and an eruption would have global consequences.

A supervolcano is a volcano capable of producing a volcanic eruption which emits over 1,000km3. This is massive compared to normal volcano eruptions (Mt St Helens erupted 1km3 volcanic material). Supervolcanoes are also different to normal volcanoes as they form depressions called calderas, they are usually surrounded by a ridge of higher land and they erupt a lot less frequently. This video explains the basics of supervolcanoes and introduces Yellowstone (video)

Supervolcanoes are on a much bigger scale than normal volcanoes and consequently have much bigger impacts. Once they have erupted supervolcanoes create calderas.

Calderas are the huge depressions created after the supervolcanic eruption.

Formation of a caldera video

Caldera formation diagram

The Yellowstone caldera measures approximately 55km by 72km.

Scientists predict there are six or seven supervolcanoes in the world. Yellowstone is one of the most famous supervolcanoes. Here the caldera is so big that scientists had to use satellite photos to check it was a caldera. About 6.5km below Yellowstone is a 64km-wide magma chamber. This volcanic activity powers Yellowstone’s hot springs and geysers.

Old Faithful Geyser Live webcam

USGS website

Potential Impacts

If a supervolcano erupted its impacts would be felt around the world. If Yellowstone erupted again magma would be flung 50km into the atmosphere and virtually all life up to 1000km away would be killed by falling ash, lava flows and the force of the eruption. Over 1000km3 of lava would pour out of the volcano which would be enough to cover the whole of the USA with a layer 12.5cm thick. The amount of ash and gas thrown up into the atmosphere would dramatically reduce the level of radiation from the sun reaching the Earth’s surface. This would trigger a freezing cold volcanic winter across the planet. This would mean crops wouldn’t grow and people would starve. Economies would collapse and society would not survive. However, supervolcanoes are rare and Yellowstone is constantly monitored to check for signs of activity. Yellowstone last erupted 640,000 years ago and the the last supervolcanic eruption was Toba 74,000 years ago.

This video explores a potential supervolcanic at Yellowstone and its potential impacts. BBC supervolcano video