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The Yellowstone Supervolcano, or, Is Yellowstone About to Blow?

Interview with Dr. Bruno J. Giletti about the Yellowstone Supervolcano

Stories in the international media and on the Internet have stirred up a great deal of interest in Yellowstone as a supervolcano. The term seems to have been popularized first in a BBC program years ago. In April 2005, U.S. TV channels showed a new “factual drama” produced by the BBC and the Discovery Channel and titled Supervolcano.

These programs caused consternation to the point of inspiring some people to question whether it is safe to travel to the Yellowstone area. So we decided to interview our own scientist, Dr. Bruno J. Giletti, Professor Emeritus of Geological Sciences, Brown University, about the supervolcano. Dr. Giletti, do you feel we should be worried about an eruption of the Yellowstone Caldera‘s supervolcano occurring soon?

Dr. Bruno GilettiBruno J. Giletti: First, I would like to distinguish between two parts of this geological question. Many eruptions have taken place within the caldera since the last supervolcano eruption 639,000 years ago. These were lava flows that erupted intermittently for a period of years or decades. They were much smaller events and not what people are referring to when they talk about a supervolcano eruption.

The supervolcano eruption is a major spewing out of molten rock from within the Yellowstone Caldera. This is what has happened three times in about the last two million years. Those eruptions blew out as much as 2,500 cubic kilometers of magma from the caldera, probably in a few weeks’ time. This molten rock had built up within the earth’s crust. Prior to an eruption it would have raised the ground level an average of a few hundred meters in the caldera.

In contrast, two small rising areas exist in the park today. Geophysicists have found that these areas, called resurgent domes, have risen only about one meter over the past eighty years.

The volume of magma needed for a superexplosion would require considerable time to accumulate below the caldera. Given the amount of geophysical instrumentation deployed in and around the park, we would have ample evidence of this process taking place. Consequently, we would have ample warning if such a process were occurring. My personal estimate would be a period of many years.

Thus, I don’t think we should be worried about an imminent supervolcano eruption. We would need a great deal more magma below the Yellowstone caldera’s surface, and there’s no evidence for that. Is there anything the U.S. government should be doing to minimize damage from this potential eruption?

BJG: Given the size of the eruption 639,000 years ago, there would not be much a government could do to modify or reduce the eruption. When geophysical and geochemical signals indicate that such an explosion is imminent, an option would be to evacuate significant portions of Montana, Wyoming, and Idaho, and possibly areas farther away from Yellowstone Park. This would require major population dislocations.

If such massive evacuations become necessary, they would be unprecedented in scale. It might be useful for federal and state planners to examine the logistics of this move in terms of availability of highways, food, drinking water, and fuel, as well as where these people could go. I think there is ample time to make such plans.

There should be increased federal support for research into a possible supervolcano explosion. This would enable scientists to develop detection instruments that are more sensitive and precise than those that are available now—and to focus directly on the supervolcano. Then they could devise ways to measure at any time the locations, sizes, and shapes of magma bodies under Yellowstone. From what is learned, they might even develop means to mitigate the effects. Should people be encouraged to go to the park in spite of the instability of the region?

BJG: Of course they should! I would say the likelihood of a supervolcano eruption in the Yellowstone area in the next decade is extremely small. There is not enough magma, and if it’s growing at all, it’s growing at a very slow rate.

NOTE: For further information, see the U.S. Geological Survey’s frequently asked questions.

ON THIS WEBSITE: Be sure to look at the Yellowstone National Park Map to find out where the Yellowstone Caldera is.

IN THE GUIDEBOOK: Pages 305–10 of Yellowstone Treasures, fifth edition, explain about the three caldera events, the most recent of which created the present-day caldera. Page 317–18 answer the question: Are we due for another caldera eruption?

Updated August 3, 2017. Copyright 2005–2017. All Rights Reserved.