Supervolcanoes Are Even Scarier Than We Thought

Do you have a cute and cuddly stuffed animal near you? If not, you might want to find one because what you're about to read will scare you silly. And not the good kind of silly either. We're talking The-End-Is-Coming sort of silly.

Two studies published in Nature Geosciences describe new findings on supervolcanoes, the most destructive natural event imaginable short of a catastrophic meteor impact. The biggest discovery is that these volcanoes can erupt spontaneously, without a trigger. Previously, it was thought that an outside force, like an earthquake, is what causes supervolcanoes to spew thousands of cubic kilometers of ash and lava into the atmosphere, potentially ushering in years of nuclear winter-like conditions. By comparison, Mount St. Helens only blasted one cubic kilometer of ash and lava into the air. A supervolcano eruption could cause the global temperature to drop by ten degrees for an entire decade.

Supervolcanoes Are Even Scarier Than We Thought

Some 200,000 years ago, a supervolcano erupted at Yellowstone. Image: Shutterstock/Nina B.

So supervolcanoes are scary. Luckily, there are only a handful of these in the world, and eruptions only happen once over many thousands of years. Unluckily, the last eruption was 12,900 years ago. So we're due for a big one—and since eruptions can occur with zero warning, it's hard to say when and where the next one will occur. But, as Smithsonian Mag points out, the studies also found that supervolcanoes are even more rare than we thought. Rather than exploding when a magma chamber's internal pressure climbs too high, as normal volcanos do, supervolcanoes explode for a different reason:

Big pools of magma in a supervolcano heat up the surrounding rock, making it less likely to get overpressured and pop. Instead, supervolcanoes' magma chambers steadily fill, the pool of magma growing larger and larger. Magma, however, is lighter than the surrounding rock, and this buoyancy puts pressure on the top of the magma chamber. When there's enough magma in the chamber, the top of the chamber cracks open and the devastating flood of magma comes bursting out.

Scientists are hoping to use this new information to improve our chances of predicting the next eruption. The geologists used a customized x-ray room to simulate the conditions that give rise to supervolcanoes, using a so-called Paris-Edinburgh press containing two tungsten carbide anvils with specks of rocks sandwiched between them. The rocks were heated up with a resistive furnace and tested at various levels to determine how the resulting magma reacted to pressure.

Supervolcanoes Are Even Scarier Than We Thought

These tests showed that pressure alone can be enough to drive magma to the surface of a supervolcano. A supervolcano, of course, is simply a mass of molten and partially molten magma under the Earth's surface, eager to get out. "The driving force [of an eruption] is an additional pressure which is caused by the different densities of solid rock and liquid magma," explains Wim Malfait, lead author on the study. "It is comparable to a football filled with air under water, which is forced upwards by the denser water around it."

If and when—but really just when—the next supervolcano eruption happens, a catastrophic amount of damage will be done. The supervolcano resting dormant under Yellowstone National Park, for instance, could wipe out nearly half the country just with the initial explosion. The aftermath would look like a dark cross between The Road and the Book of Revelations. So until then, squeeze that stuffed animal tight. Squeeze it tight and sing pretty songs. It will all be over soon. [Science Daily; Smithsonian Mag]

Image via Getty / Gizmodo