- Here's a reason to breathe easier: Civilization probably
won't be crippled anytime soon by a pulverizing volcanic eruption at Yellowstone
National Park.
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- New research indicates there is probably not a huge pot
of magma brewing beneath Yellowstone that's building up to a superviolent
eruption thousands of times more powerful than the 1980 eruption of Mount
St. Helens.
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- "If something like that was cooking up right now
we'd see the evidence, and we don't," said Drew Coleman, an assistant
geology professor at the University of North Carolina.
- Coleman is one of three scientists who authored two recent
studies aimed at changing the way we think about volcanoes - especially
how often the "big ones" erupt.
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- Earth has seen staggering volcanic eruptions. The last
was about 75,000 years ago when an eruption at the Toba volcano in Indonesia
may have come close to wiping out all primates, including humans, university
officials said.
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- Yellowstone, the largest known center of active volcanism
on the planet, has had its share. Massive eruptions 2 million, 1.3 million
and 630,000 years ago were 2,500, 280 and 1,000 times larger, respectively,
than Mount St. Helens.
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- The latest major eruption formed the famous Yellowstone
Caldera than encircles Old Faithful, Canyon, Grant Village and portions
of Yellowstone Lake.
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- "It's not hyperbole to say that the biggest eruptions
could bring an end to civilization," said Allen F. Glazner, a geology
professor at UNC. "Our new work casts doubt on the assumption that
gigantic eruptions should be relatively common."
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- To reach that conclusion, Coleman, Glazner and the University
of Utah's John Bartley examined long-extinct volcanoes in California's
Sierra Nevada Mountains.
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- In particular, they studied bodies of magma that have
cooled underground, called plutons, which are the main building blocks
of the Earth's crust. They also examined seismic waves produced during
earthquakes and measured magma cooling.
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- According to traditional geologic theories, they should
have found big blobs of magma beneath the surface that formed in less than
1 million years - a relatively short period of time on a geologic scale.
The huge stores of magma, which is underground molten rock, were thought
to be lurking beneath active volcanoes and feeding large-scale eruptions.
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- Instead, they found that it takes much longer for those
plutons to form, up to 10 million years, and that it happens in small fits
and starts, not with a big blob of magma rising up.
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- That means that the giant eruptions fueled by large volumes
of magma are less likely to happen, the researchers concluded.
- "We conclude that volcanoes are more prone to chugging
along, producing many small - though still dangerous - eruptions such as
the 1980 eruption at Mount St. Helens, rather than huge civilization-destroying
eruptions," Coleman said.
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- Although the research focused on the Sierra Nevada, Coleman
said the results apply to places like Yellowstone.
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- The findings, which have already drawn praise from some
and will likely spur controversy, appear in the April issue of GSA Today
and the May issue of Geology.
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- The research comes amid international debate over the
existence of mantle plumes, the columns of hot rocks that were typically
thought to rise from deep within the Earth, giving life to volcanoes in
Yellowstone, Hawaii, Iceland and elsewhere.
- Recent research by the U.S. Geological Survey and others
suggests there may not be a deep plume beneath Yellowstone. Instead, a
shallow skin of magma beneath the ground may fuel the area's vast geothermal
system.
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- Events at the park, including the discovery of a bulge
at the bottom of Yellowstone Lake and briefly higher temperatures at Norris
Geyser Basin, have ignited Internet chatter over the possibility of a "supervolcanic"
eruption at Yellowstone.
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- Like other geologists who have weighed in, UNC's Coleman
said that prospect seems unlikely for a long time to come.
- "Of the seismic evidence under Yellowstone that
I'm familiar with, there's no big volume of magma waiting to blow,"
he said.
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2004/04/28/build/state/40-yellowstone-blowup.inc
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