What Triggers Supervolcanos? New Study Shows That Magma Pressure Alone Is Enough To Spark Devastation

By Ben Wolford on January 6, 2014 4:52 PM EST

Lake Toba
Super-volcanos, such as Lake Toba in Indonesia, can erupt from magma alone, without any external trigger. (Photo: Shutterstock)

Supervolcanos — which erupt thousands of times more powerfully than standard volcano blasts — have long been a mystery to volcanologists. Because they are exponentially larger than their peers, scientists had believed that something else, such as an earthquake, must be involved when these super-massive eruptions go off.

But a new study, published Sunday in the journal Nature Geoscience, examined the mechanics of supervolcano pressure. The research shows that the intense pressure of extra magma alone is enough, without any help from external influence. The authors say this new knowledge could help predict conditions for super-massive eruptions, hundreds of times worse than anything we've experienced.

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"This is something that, as a species, we will eventually have to deal with. It will happen in future," leader author Wim J. Malfait, of ETH Zurich, told BBC News. The largest-known eruptions all happened before anyone reading this was alive, and most of them occured long before any humans whatsoever even existed. To the extent that scientists have catalogued supervolcanic eruptions, we know that the largest are at least 150 times more massive than the 1991 eruption of Mt. Pinatubo in the Philippines. That one killed 800, displaced 100,000 and cooled global temperatures for several years because of the debris it jettisoned into the atmosphere.

To understand what sets off supervolcanos, the Swiss team of researchers traveled south to Grenoble, France, to borrow a machine called the "high pressure beamline," BBC reports. They used the device to shoot X-rays through a tiny diamond capsule full of synthetic magma, which they superheated past 3,000 degrees Fahrenheit. It created pressure around 529,000 pounds per square inch.

What they found was that the buoyant nature of enough magma could push material through the earth's crust with globe-shaking force. When magma forms and pushes up to the ceiling of the mantle, it cools and becomes more dense. The magma below it, meanwhile, is less dense and tries to rise. Malfait explains it to the BBC in soccer terms: "The effect is comparable to holding a football under water. When you release it, the air-filled ball is forced upwards by the denser water around it."

So how soon are we doomed? Probably not in our lifetimes. But there are several known active supervolcanos, including perhaps the most notable in the United States: Yellowstone National Park. The last time it blew up was about 640,000 years ago. The largest eruption ever also happened in what would become the United States. The Garita Caldera in Colorado unleashed 3,107 cubic miles of lava about 27 million years ago. These and other supervolcanos are characterized not by an obvious cone shape but by a lake or a depression called a caldera. Calderas form when the crust collapses into the place where pressurized liquid magma once propped up the ground.

Photo above courtesy of Shutterstock.

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