The Grand Prismatic Spring is beautiful but it sits just above a dangerous supervolcano.Photo: Reuters
What is a supervolcano?
The common picture of a volcano being a mountainous cone of ash and lava does not apply to the supervolcanos like Yellowstone.
These are vast spaces of collapsed crust that formed pools – known as calderas – under a seemingly normal surface. Only mapping reveals the gentle swell, over a space of hundreds of square kilometres, that contains the cauldron of molten magma below.
Tourists walk beside a hot spring and the partially frozen Yellowstone Lake.Photo: Getty Images
But wait: There’s more
Twenty “smaller” supervolcanoes have been found nearby, on the Utah/Nevada state border.
The new study published in the journal Geosphere shows that these volcanoes are not active today. But, 30 million years ago, they spilt more than 5500 cubic kilometres of magma during a one-week period.
“In southern Utah, deposits from this single eruption are 4km thick. Imagine the devastation – it would have been catastrophic to anything living within hundreds of miles,” Dr. Eric Christiansen of Brigham Young University said.