Supervolcanoes Likely Triggered Externally

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According to a recent study, supervolcanoes, massive eruptions with potential global consequences, appear not to follow the conventional volcano mechanics of internal pressure building until the volcano blows. Instead, the new study finds that such massive magma chambers might erupt when the roof above them cracks or collapses.

The study was conducted by Patricia Gregg of University of Illinois, in collaboration with Eric Grosfils of Pomona College and Shan de Silva of Oregon State University.

Knowledge of triggering mechanisms is crucial for monitoring supervolcano systems, including ones that lie beneath Yellowstone National Park and Long Valley, California, according to the study led by Patricia Gregg, University of Illinois professor of geology. Gregg said that it’s very likely that supereruptions must be triggered by an external mechanism and not an internal mechanism, which makes them very different from the typical, smaller volcanoes that we monitor.

“If we want to monitor supervolcanoes to determine if one is progressing toward eruption, we need better understanding of what triggers a supereruption. It’s very likely that supereruptions must be triggered by an external mechanism and not an internal mechanism, which makes them very different from the typical, smaller volcanoes that we monitor.” -Gregg said.

A supervolcano is classed as more than 500 cubic kilometers of erupted magma volume. For comparison, Gregg said, Mount St. Helen’s ejected about one cubic kilometer of material, so a supervolcano is more than five hundred times larger.

“A typical volcano, when it erupts, can have lasting impacts across the globe,” Gregg said. “We’ve seen that in Iceland when we’ve had large ash eruptions that have completely disrupted air traffic across Europe. A supereruption takes that to the nth degree.”

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The new study’s findings are contrary to a pair of papers published in the journal Nature Geoscience in 2014 that claim a link between eruption likelihood and magma buoyancy. The magma byouancy hypothesis suggested that magma may be less dense than the rock surrounding it and therefore could push up against the roof, like an ice cube bobbing in water, increasing the pressure within the chamber and triggering an eruption.

The study was published in the Journal of Volcanology and Geothermal Research. Gregg also presented the findings this week at the annual meeting of the Geological Society of America.

Courtesy: news.illinois.edu