Yellowstone national park, volcano under Yellowstone, caldera under Yellowstone
Gerry Broome/AP
The Yellowstone River plunges over
Lower Falls into the Grand Canyon of


Small Earthquakes Rattle Yellowstone and Its Volcano

December 30, 2008 01:55 PM
by Emily Coakley
A recent series of earthquakes in Yellowstone National Park has renewed concerns about what a giant volcano under the park has in store.

Scientists Watching Earthquakes Closely

Some scientists are speculating that a cluster of more than 200 small earthquakes felt in Yellowstone National Park over the weekend may lead up to something larger, reports LiveScience.

As the national park is actually sitting on what’s been called a “super volcano,” some worry what the larger event could be.

The earthquakes have all measured less than 4.0 on the Richter scale, and haven’t caused any damage. People in the Yellowstone area probably didn’t even feel most of the tremors, LiveScience said. But in aggregate, they could carry great significance.

“This is an active volcanic and tectonic area, and these are the kinds of things we have to pay attention to. We might be seeing something precursory,” said Robert Smith, a geophysics professor at the University of Utah, in an interview with the Associated Press.

He added: “Could it develop into a bigger fault or something related to hydrothermal activity? We don’t know. That’s what we’re there to do, to monitor it for public safety.”

The University of Utah runs the Yellowstone Seismic Network, which keeps an eye on activity throughout the national park.

Background: Yellowstone’s “super volcano”

Yellowstone’s many attractions include geysers, such as Old Faithful, and hot springs. These are believed to be a result of the giant pool of magma that Yellowstone sits on, according to the United States Geological Survey’s Cascades Volcano Observatory.

Some call the enormous caldera, which measures approximately 28 by 47 miles, a “super volcano.” The UnMuseum explains that “super volcano” isn’t exactly a technical scientific term, but says it differs from a traditional volcano “in that there is often no mountain peak associated with it.”

The lack of a peak or potential outlet for gas, heat and pressure building underground means that “the entire surface above the underground chamber, which can be many miles wide, is blown away by a titanic explosion that can be thousands of times more powerful than that of a regular volcano.”

Volcanic eruptions can’t be predicted, and scientists wonder when Yellowstone will blow again. According to LiveScience, the caldera last blew up about 600,000 years ago.

Projections suggest that such an eruption would be catastrophic to most of the United States, with half the country being “covered in ash up to 3 feet deep,” LiveScience says, adding, “But those same researchers say nothing suggests such an eruption is imminent. They point out, however, that Yellowstone seems to blow its top about every 600,000 years.”

The Cascades Volcano Observatory calls the Yellowstone caldera “one of the largest and most active in the world.” The United States has other, smaller calderas throughout the west.

Super volcanoes are also found in other parts of the world, according to the Discovery Channel. They include a 1,000-square-mile caldera in Bolivia, and Lake Toba in Indonesia, which the Discovery Channel describes as the world’s largest at 1,080 square miles.

Reference: National parks and Montana travel; interactive lesson on calderas


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