Friday, July 08, 2005

Volcano holds key to future eruptions?

From 1987-95 the Yellowstone caldera subsided and contracted.From 1995-2005 it rose and expanded.

From 1996-2000 the land around Norris rose about five inches and "then it stopped," Henry Heasler said."It's telling us something - what, we don't know," the park geologist said Tuesday at the Buffalo Bill Historical Center.Yellowstone's dynamic landscape is under constant monitoring, which Heasler said he hopes will allay some fears about a catastrophic occurrence. If one were to happen, indications would begin at least months, if not years, in advance, he added."Yellowstone is one of the world's largest active volcanoes," he said.

The indicators comprise 10,000 or more hydrothermal features, including 300-plus geysers, seismic activity, including 2,375 temblors in 2002, and active ground deformation of inches per year."That's unusual," Heasler said.The three major eruptions occurred 2.1 million years ago (6,000 times as powerful as Mount St. Helens), 1.3 million years ago and 640,000 years ago with the last lava flow 70,000 years ago or less."Lava flows created the topography you currently see," he said.The most recent eruption created the caldera, the volcanic crater, that collapsed afterward. It measures 45x35 miles and sits in the middle of the park.

Numerous earthquakes occurred in the park last year, many in the west-central area.Despite all the activity and recent media hype, Yellowstone is not about to blow up and destroy the world, Heasler said. Caldera-forming eruptions are infrequent and occur hundreds of thousands of years apart."And we don't know if there will be another," he added.Eighty eruptions have occurred since 640,000 years ago, along with lava flows, but no large, catastrophic ones.

Large hydrothermal explosions have also occurred, such as the one that created Mary Bay. The 5-10 in the last 14,000 years happened generally around the lake.Most common are small, hydrothermal explosions, 20 since 1872 including the most recent, Pork Chop Geyser in Norris in 1989."They have local effects only," he added.To predict a major eruption, the U.S. Geological Survey watches for signs such as large and shallow earthquake swarms, deformation involving yards of uplift, change in gas emissions, steam explosions and hydrothermal alterations.

"They've all occurred in the past several years, but the big thing is - not in the same area," Heasler said.If all the indicators converged, they would signal an impending eruption, he added. One sign or a combination of signs does not indicate an eruption.The Yellowstone Volcano Observatory project comprises 24 seismic stations, "with a 25th, I hope, this year," he added. "We try to make them as unobtrusive as possible, but they're necessary for visitor safety."The solar panels powering the equipment are camouflaged among tree branches.

The three stations around the lake will provide "real-time information about deformation," Heasler said. Scientists also monitor the hydrology."We don't manage the geologic resource. The geologic resource manages itself fine," he said. "We want to make sure we don't alter anything."One piece of equipment measuring the flow at Tantalus Creek tracks Echinus Geyser's eruptions. The data are posted on the observatory's Web site,
gathered recently showed changes in one area of Yellowstone Lake that harbors an underground geyser basin.

Instead of calling the activity a "bulge," Heasler said he prefers the moniker "non-inflated plane" or "Nash Creek/Storm Point vent system."The research created a flurry of predictions about eruptions."We have to be careful when we name features," Heasler added."Yellowstone is a natural laboratory," where scientists continue to gather information, he said.

"The three words I say most in Yellowstone are, 'I don't know.'"The technology assists the monitoring and provides baseline data for a warning if conditions warrant."We have no final answers, yet," he added.

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