Supervolcano: How much warning time would we have?

Monday, July 25, 2016, 3:41 PM - Depending on how large a supervolcano eruption is, it could strike a devastating blow to civilization as we know it.

Luckily, scientists have figured out how we might have some warning, though not much: A new study released last week suggests humanity would have about a year to brace itself before just such an eruption.

To come up with their conclusions, the researchers -- from Vanderbilt University and the University of Chicago -- examined California's Bishop Tuff, in the Long Valley Caldera, which itself was the site of a super eruption around 760,000 years ago.

The researchers used microscopic analysis of the rims of quartz crystals within the pumice to determine how fast they grew in the leadup to an eruption.

The end of the Bishop Tuff pyroclastic flow. Image: Rhalden/Wikimedia Commons

"Our data show that quartz rims grew well within a year of eruption, with most of the growth happening in the weeks or days preceding eruption," the researcher wrote in their paper, published in the open source journal PLOS One. "Growth took place under conditions of high supersaturation, suggesting that rim growth marks the onset of decompression and the transition from pre-eruptive to syn-eruptive conditions."

The researchers say an impending super eruption would likely also show signs at the surface as the volcano's magma store slowly expanded, though more work is needed to determine what those signs could look like.

Several super eruptions have taken place on Earth over the last few million years, the last being the Oruanui eruption in New Zealand more than 26,000 years ago. The Toba eruption in modern-day Indonesia, 75,000 years ago, spewed more than 2,800 square kilometres of volcanic material into the environment, and some theories blame the event for the catastrophic fall in the number of human beings on Earth to a mere few thousand (though later studies, most recently in 2013, dispute the link between the eruption and the population collapse, according to Livescience).

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Closer to home, the supervolcano beneath Yellowstone has erupted several times in the past few million years, most recently 640,000 years ago.

"As far as we can determine, none of these places currently house the type of melt-rich, giant magma body needed to produce a super-eruption," lead researcher Guilherme Gualda said in a release from Vanderbilt. "However, they are places where super-eruptions have happened in the past so are more likely to happen in the future."

SOURCES: Vanderbilt University | PLOS One | Livescience | Yellowstone Park