Research Spotlight: The ‘Rosetta Stone’ of supervolcanoes

Bishop Tuff at Long ValleyScientists have found the “Rosetta Stone” of supervolcanoes, those giant pockmarks in the Earth’s surface produced by rare and massive explosive eruptions that rank among nature’s most violent events. The eruptions produce devastation on a regional scale – and possibly trigger climatic and environmental effects at a global scale.

A fossil supervolcano has been discovered in the Italian Alps’ Sesia Valley by a team led by Jim Quick, SMU’s associate vice president for research and dean of graduate studies, and a geology professor in the Huffington Department of Earth Sciences, Dedman College. A rare uplift of the Earth’s crust in the Sesia Valley reveals for the first time the actual “plumbing” of a supervolcano from the surface to the source of the magma deep within the Earth, according to a new research article reporting the discovery.

The uplift was created when Africa and Europe began colliding about 30 million years ago and the crust of Italy was turned on end, Quick says. It reveals to an unprecedented depth of 25 kilometers the tracks and trails of magma as it moved through the Earth’s crust.

Supervolcanoes, historically called calderas, send up hundreds to thousands of cubic kilometers of volcanic ash in explosive events that occur every few hundred thousand years. They have spread lava and ash over vast distances, and scientists believe they may have set off catastrophic global cooling events at different periods in the Earth’s past.

Sesia Valley’s caldera, which is more than 13 kilometers in diameter, erupted during the Permian geologic time period, say the discovery scientists. Its discovery will advance scientific understanding of active supervolcanoes like Yellowstone, which is the second-largest supervolcano in the world and last erupted 630,000 years ago.

“What’s new is to see the magmatic plumbing system all the way through the Earth’s crust,” says Quick, who previously served as program coordinator for the Volcano Hazards Program of the U.S. Geological Survey. “Now we want to start to use this discovery. We want to understand the fundamental processes that influence eruptions. Where are magmas stored prior to these giant eruptions? From what depth do the eruptions emanate?”

To date, scientists have been able to study a caldera’s exposed “plumbing” from the surface of the Earth to a depth of only 5 kilometers. Because of that, scientific understanding has been limited to geophysical data and analysis of erupted volcanic rocks.

Quick likens the relevance of Sesia Valley to seeing bones and muscle inside the human body for the first time after previously envisioning human anatomy on the basis of a sonogram only.

“We think of the Sesia Valley find as the ‘Rosetta Stone’ for supervolcanoes because the depth to which rocks are exposed will help us to link the geologic and geophysical data,” Quick says. “This is a very rare spot.”

(Above, the Bishop Tuff volcanic deposits, consisting of ash and pumice ejected during the eruption that created the Long Valley Caldera in California. The event erupted 140 cubic miles of magma 760,000 years ago. Photo: U.S. Geological Survey)

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