Tuvurvur volcano
© Wikimedia CommonsTuvurvur volcano - part of Rabaul Caldera – Papua New Guinea.

Super-volcanoes are the worst natural disaster the Earth can face, besides a meteor strike, said Patricia Gregg, a post-doc at Oregon State University and lead author of a study that may have found what triggers the massive eruptions.

Luckily, super-volcanoes only devastate the planet ever 100,000 years or so. But why they erupt has had scientists stumped, since they aren't like their puny cousins, the regular volcano, which are triggered by internal precursor eruptions.

But there seems to be no internal precursor to a super-volcano eruption. The trigger comes from above.

"Instead of taking the evidence in these eruptions at face value, most models have simply taken small historic eruptions and tried to scale the process up to super-volcanic proportions," said Shanaka de Silva, an OSU geologist and co-author of the study, in a press release.

"Those of us who actually study these phenomena have known for a long time that these eruptions are not simply scaled-up Mt. Mazamas or Krakataus - the scaling is non-linear. The evidence is clear," said de Silva.

The researchers believe that super-volcanoes only form under specific, rare conditions.

A stretchable halo of rock has to build up above a magma chamber, which can be as large as 10,000 to 15,000 cubic kilometers. The ductile rock keeps stretching into a dome for thousands of years. Pressure keeps building in the magma chamber, until cracks start to form in the dome.

Once one of those cracks causes the dome to collapse, tens of thousands of years of pressure are released, and...

Castle Geyser
© Wikimedia CommonsCastle geyser, Yellowstone National Park.
"Huge amounts of material are expelled, devastating the environment and creating a gas cloud that covers the globe for years," said Gregg.

"You can compare it to cracks forming on the top of baking bread as it expands," explained Gregg. "As the magma chamber pressurizes at depth, cracks form at the surface to accommodate the doming and expansion. Eventually, the cracks grow in size and propagate downward toward the magma chamber.

"In the case of very large volcanoes, when the cracks penetrate deep enough, they can rupture the magma chamber wall and trigger roof collapse and eruption," Gregg added.

Hopefully, the researchers won't get a chance to observe their hypothesis in action any time soon, but places to watch are Huckleberry Ridge in Yellowstone National Park, Lake Toba in Sumatra, the central Andes Mountains, New Zealand, and Japan.

Don't cancel your vacations plans though, a Yellowstone eruption doesn't seem likely in the near future.

"The uplift of the surface at Yellowstone right now is on the order of millimeters," she explained. "When the Huckleberry Ridge eruption took place, the uplift of the whole Yellowstone region would have been hundreds of meters high, and perhaps as much as a kilometer."