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The Yellowstone Supervolcano

U of U geology professor Robert B. Smith



U of U geology professor Robert B. Smith has made a 50-year career out of studying Yellowstone. He presents a lecture on the Yellowstone Supervolcano Wednesday, March 18, at 7:30 p.m. at the Skaggs Biology Building auditorium (257 S. 1400 East). Smith is a senior author of Windows Into the Earth: The Geologic Story of Yellowstone and Grand Teton National Parks.

In late December 2008, a swarm of earthquakes shook the north end of Yellowstone Lake for about 10 days. It was the second-largest swarm in recorded history with about 1,000 earthquakes, one a magnitude 3.9 on the Richter scale. Is Yellowstone powering up for something big?
Not really. Swarms are common occurrences in Yellowstone. We’ve just done a study where we’ve recognized 70 separate, distinct swarms within the Yellowstone caldera over the past 30 years. This happens to be the second largest. There was one bigger in 1985. We think it could have been related to hydrothermal fluids propagating along an old fracture zone.

The U.S. Geological Survey classifies the area as a “high-threat,” the 21st most dangerous of the 169 volcano centers in the United States. Why the red alert?
It is an active volcano. In the history of Yellowstone, we’ve had three of these giant eruptions, with the last one 630,000 years ago. Since then, there have been over 80 eruptions that were bigger than the Mount Pinatubo or Mount St. Helen eruptions, the [most recent] about 70,000 years ago. Since then, we’ve had dozens of hydrothermal eruptions—fluid flow or phreatic eruptions, as we call them. Plus, we’ve had the biggest earthquake in historic time in the Intermountain region at Yellowstone. So it’s a combination deal; you get earthquakes and volcanoes for the price of one.

Why is it called a supervolcano?
I don’t call it a supervolcano; I call it a “giant” volcano. But the BBC documentary (Supervolcano, 2005) called it a supervolcano, and when it was all said and done, they set a precedent. They did a good job. Of course, we were all consultants and kept them toeing the line. They took a very, very unlikely event and made it plausible. They didn’t say anything incorrect.

What’s the inside scoop on Yellowstone?
Everything is new. There are always earthquakes. There’s ground deformation.

It’s the most intense seismic area of the whole Intermountain West. We have mountain building; we have the ground uplifting at 7 centimeters per year. These are tremendously high geologic rates. So, basically, it’s a live system. It’s a living, breathing, shaking caldera, as I always say.

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