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Yellowstone national park, volcano under Yellowstone, caldera under Yellowstone
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Yellowstone National Park

Understanding Why Yellowstone’s Supervolcano Is So Dangerous

January 07, 2009 12:25 PM
by findingDulcinea Staff
The geological history of Yellowstone National Park worries many observers about a “supervolcanic” eruption that could destroy much of the United States.

Explaining Yellowstone’s Supervolcano

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When Yellowstone National Park experienced its largest eruption 2.1 million years ago, massive volcanic depressions formed, known as “calderas.” The explosion also spewed volcanic ash over half of the United States, reaching areas of as far away as Texas, Louisiana and southern California, according to the U.S. Geological Survey.

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.

Some call the enormous underground caldera, which measures approximately 28 by 47 miles, a “supervolcano.” The UnMuseum explains that supervolcano 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 increasess the likelihood 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.”

According to a BBC feature on such volcanoes, after an eruption, “The sky will darken, black rain will fall, and the Earth will be plunged into the equivalent of a nuclear winter.

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.

Supervolcanoes 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.

Reactions: How doomed are we?

Concern over the dangers of the Yellowstone caldera have been renewed recently by a series of hundreds of small earthquakes in the park that began at the end of December. 

The earthquakes have all measured less than 4.0 in magnitude, and haven’t caused any damage. But increased seismic activity at Yellowstone National Park raises the question: is the supervolcano going to erupt? Scientists say the string of 500-plus tremors that have been felt there in the past week is certainly atypical, according to the Times of London. Furthermore, the floor of Yellowtone’s caldera—a volcanolike formation usually formed by collapsed rock after an eruption—has risen about three inches a year for the past three years, “a rate more than three times greater than ever observed since such measurements began in 1923.”

Jake Lowenstern, Ph.D., Yellowstone Volcano Observatory’s chief scientist, who is also a member of the U.S. Geological Survey’s Volcano Hazards Team, does not think a supervolcano eruption will occur soon, according to U.S. News & World Report. “We don’t think the amount of magma exists that would create one of these large eruptions of the past,” he said. “It is still possible to have a volcanic eruption comparable to other volcanoes. But we would expect to see more and larger quakes, deformation and precursory explosions out of the lake. We don’t believe that anything strange is happening right now.”

On the other hand, Time magazine quotes a passage from Bill Bryson’s “A Short History of Nearly Everything,” in which Yellowstone geologist Paul Doss indicates to Bryson that an eruption could very well happen now, for the simple fact that “Nobody was around the last time it blew, so nobody knows what the warning signs are.” There may be sporadic earthquakes, strange geyser patters or a lifting of the surface, but “nobody really knows.”

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

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