Even after an eruption, supervolcanoes remain a threat for thousands of years

Sept. 3 (UPI) -- It's long been assumed that after supervolcanoes explode, the threat of another massive eruption is greatly diminished.

However, new research -- published Friday in the journal Communications Earth and Environment -- suggests supervolcanoes remain active for thousands of years after a super-eruption.

Previous surveys suggest supervolcano eruptions are typically separated by tens of thousands of years, but until now, researchers knew little about the dormancy periods in-between massive eruptions.

"Gaining an understanding of those lengthy dormant periods will determine what we look for in young active supervolcanoes to help us predict future eruptions," lead author Martin Danišík, associate professor at Curtin University's John de Laeter Center, said in a press release.

When supervolcanoes explode, they can expel deadly waves of molten hot rock in all directions.

Supervolcano explosions are a global phenomenon. The massive ash plumes produced by a super-eruption can spread out across Earth's upper atmosphere, blocking sunlight and triggering what's known as a "volcanic winter."

"Learning how supervolcanoes work is important for understanding the future threat of an inevitable super-eruption, which happen about once every 17,000 years," Danišík said.

To better understand supervolcano dormancy, researchers analyzed feldspar and zircon minerals in the magma deposited by the Toba super-eruption 75,000 years ago.

By studying argon and helium gasses trapped in the ancient mineral deposits, researchers were able to reconstruct Toba's past.

"Using these geochronological data, statistical inference and thermal modelling, we showed that magma continued to ooze out within the caldera, or deep depression created by the eruption of magma, for 5,000 to 13,000 years after the super-eruption, and then the carapace of solidified left-over magma was pushed upward like a giant turtle shell," Danišík said.

Traditionally, volcanologists look for liquid magma beneath a volcano to assess its potential for catastrophic eruption. But the latest findings suggest supervolcanoes remain a threat even when liquid magma is absent.

"While a super-eruption can be regionally and globally impactful and recovery may take decades or even centuries, our results show the hazard is not over with the super-eruption and the threat of further hazards exists for many thousands of years after," Danišík said.

"Learning when and how eruptible magma accumulates, and in what state the magma is in before and after such eruptions, is critical for understanding supervolcanoes," Danišík said.