Supervolcanoes May Erupt Surprisingly Fast

Supervolcanoes May Erupt Surprisingly Fast
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Once primed, a supervolcano can decompress and erupt in under a year, a new study shows, offering little warning before a potentially cataclysmic event. 

Supervolcanoes, the hulking geological behemoths that they are, slumber for hundreds of thousands or even millions of years in between eruptions. That's a very good thing, for when they blow, they explode with colossal power, spewing hundreds or even thousands of cubic kilometers of ash across thousands of miles, as well as altering the global climate. 

A quarter of all known supervolcanoes are in the United States, with the best-known dwelling below the picturesque, breathing landscape of Yellowstone National Park. If it were to erupt, it would spew ash as far away as New York. But the sooty dusting that the eastern seaboard would receive would pale in comparison to the ashfall in the heart of the country. Nearby states would be buried under as much as six feet of ash!

Such a scenario seems unlikely to occur anytime soon. None of the world's supervolcanoes currently house magma bodies large enough to produce a cataclysmic eruption. The dormancy has afforded modern humans a chance to thrive globally, and given geologists a chance to safely study supervolcanoes.

Geologists Guilherme Gualda of Vanderbilt University and Stephen Sutton of the University of Chicago recently examined quartz crystal formations left by the supervolcano eruption that created the Long Valley Caldera in California more than 760,000 years ago. Patterns and element concentrations in the crystals are used gauge the evolution of a historical body of magma. In this case, the authors focused on the concentration of titanium to measure the growth rate of crystal rims that mark the final stages of an eruption.

From their analysis, Gualda and Sutton determined that a body of magma below a supervolcano can decompress and erupt in under a year. Their finding disagrees with prior analyses conducted on crystals from the same source, suggesting that this process usually takes over a century.

With their results, the researchers created a rough timeline of a supervolcano explosion. Over tens of thousands of years, the volcanic chamber fills with magma mush of melted rock and solid crystal. Eventually, sufficient magma flows into the chamber and the crystals are expelled. Over the next 5,000 years, the bulging chamber builds pressure. Finally, decompression begins, followed swiftly by an eruption.

“Now we have shown that the onset of the process of decompression, which releases the gas bubbles that power the eruption, starts less than a year before eruption,” Gualda said in a press release.

The timeline is potentially terrifying. If true, it means humanity could be afforded comparatively small notice of a coming eruption.

Source: Gualda GAR, Sutton SR (2016) The Year Leading to a Supereruption. PLoS ONE 11(7): e0159200. doi:10.1371/journal.pone.0159200

(Image: Robert B. Smith via AP)

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