More crowd control---
Scientists: No major eruption likely soon at Yellowstone
Aug. 20, 2003 11:30 AM
BC-WST--Yellowstone-Eruption,500
YELLOWSTONE NATIONAL PARK, Wyo. (AP) - Geothermal activity is increasing in a
Yellowstone National Paark geyser basin and the bottom of Yellowstone Lake is
bulging, but scientists say there is no impending major eruption.
Searing ground temperatures, bursts of steam and flows of hot water prompted
park officials to close about half the trails in Norris Geyser Basin this
summer, and the increased thermal activity has led to concern among some
visitors about the potential for an eruption.
"This is just part of the change that goes on in Yellowstone," park geologist
Hank Heasler said. "I wont say its normal, because we dont know what normal is."
But scientists say there is no evidence that Yellowstone is poised for a
powerful eruption, such as the one that rocked the region 600,000 years ago.
If the park were ready to blow its top, there would be several signs that magma
was moving toward the surface, and earthquakes would be more frequent and
stronger. The ground, while often rising and falling in Yellowstone, would most
likely gradually rise and the chemistry of many geysers would change.
All of that activity is constantly monitored by scientists with the Yellowstone
Volcanic Observatory, a long-running study of the parks underground systems.
If the park were poised for a major eruption, the signs wouldnt be subtle,
Heasler said.
"I doubt youd need seismographs to know that changes were happening in
Yellowstone," he said.
Early signs of an impending outburst would be similar to the 1980 eruption of
Mount St. Helens in Washington state. Scientists knew something big was brewing
months ahead of time although they couldnt predict exactly how big or when the
eruption was coming.
The current geologic activity in Yellowstone appears to be much closer to the
surface than would be exhibited by magma flows. At such shallow depths, water
heated by the earth is driving the changes.
"Were not searching for magmatic fluids," said Bob Smith, a geologist at the
University of Utah who has studied the park for three decades. "We think this is
a very shallow system."
Norris is the most dynamic of the parks geyser basins and Jacob Lowenstern, a
researcher at the U.S. Geological Survey in Menlo Park, Calif., said it always
experiences increased activity in summer.
But this year is exceptional, with a new mud pot welling up, 200-degree
temperatures on the ground and geysers that havent erupted in years spouting
off.
And unlike years past, dramatic improvements in equipment are allowing
scientists to peek deeper and more precisely record changes in the upper
plumbing. They are using precision seismometers and satellite-mapping systems to
record the changes.
"Lets say were doctors and Norris Geyser Basin is our patient," Heaslier said.
"Before, we had the ability to take its pulse and temperature. Now we have a
stethoscope and an X-ray machine, and we can look inside."
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On the Net:
Yellowstone Volcano Observatory:
http://volcanoes.usgs.gov/yvo