What Makes an Explosive Supervolcano Erupt: Trigger Discovered by Scientists

Supervolcanos are some of the largest and most explosive in the world. After erupting, these massive volcanoes leave giant holes in the Earth's crust instead of a volcanic cone. On average, these volcanoes are active more rarely than once every 100,000 years. Now, though, scientists have discovered a trigger for these supereruptions, which tells them a bit more about what might make these supervolcanos explode.

Supervolcanos are a rare but serious threat. They're not easy to spot, either; new ones are still being discovered today. Explosions caused by these volcanoes usually eject at least 450 (but sometimes even several thousands) cubic kilometers of rock material and ash.  This material can rise high into the atmosphere and have devastating impacts on the climate and life on Earth.

Currently, scientists know that supervolcanos are located in the Yellowstone Caldera in the United States, Lake Toba in Indonesia and Lake Taupo in New Zealand. The somewhat smaller Phlegraean Fields near Naples also contain a smaller supervolcano.

In order to learn a bit more about supervolcanos, the researchers turned to X-rays. Using the X-ray beam at the European Synchrotron Radiation Facility (ESRF), the scientists demonstrated that the overpressure generated by density differences in the magma chamber alone can trigger a supereruption. The magma chamber is located in the Earths' crust beneath the volcano.

"X-rays can probe the state-liquid or solid-and the change in density when magma crystalizes into rock," said Mohamed Mezouar, one of the researchers, in a news release.

For the magma to actually break through the crustal rock above the magma chamber and carve out a path to the surface, it needs an overpressure level that is 100 to 400 times higher than air pressure. With a big enough magma chamber, though, this overpressure can occur.

While the differences in density may trigger an eruption, there are also contributory factors. For example, the saturation of the magma with water vapor or tectonic tension could help instigate the eruption, though probably couldn't trigger it by itself.

The findings reveal a bit more about supervolcanos. Since their eruptions can be so devastating, it's crucial to learn all we can about them.

The findings are published in the journal Nature Geoscience.