Tracking Yellowstone's `beast'


Ancient: The national park is home to one of the world's largest active volcanoes, which scientists are monitoring for the next big eruption.

September 08, 2001|By Usha Lee McFarling | Usha Lee McFarling,SPECIAL TO THE SUN

YELLOWSTONE NATIONAL PARK - When the volcano here blew, it obliterated a mountain range, felled herds of prehistoric camels hundreds of miles away and left a smoking hole in the ground the size of the Los Angeles Basin.

Modern Yellowstone doesn't dwell on its cataclysmic past or its potential for another monster eruption. Rangers tell people to keep their distance from bison and steaming geysers. But there are no signs, aside from nature's bubbling mud pots and geysers, that visitors are wandering through the caldera of one of the largest active volcanoes in the world.

"This is a geologic park, and not many know it," says Robert Smith, a geophysicist at the University of Utah who has spent his career piecing together the story of the Yellowstone volcano. "It's not a bison park. Not an elk park. It's a geologic park."

New sensors have allowed researchers to confirm a suspicion that Smith has held for a long time - that the ancient volcano scientists dub "the beast" is a living force. The instruments, acting as an early warning system, record a pattern of heaving and bulging.

Installed without fanfare and hidden from view, the sensitive devices are an acknowledgment that the past could be prologue, that this seemingly serene plateau could blow so hard it would make the Mount St. Helens explosion in 1980 look like a sneeze.

Observatory site

This summer, Yellowstone was added to the nation's handful of official volcano observatories. The others, smaller but far better known, are in Hawaii, Alaska, the Cascades and California's Long Valley. The Yellowstone observatory consists of a string of 28 electronic detection stations scattered through the park. Related plans call for at least 100 more monitoring sites.

For Smith, who argued for years that the volcano deserved more attention than it was getting, the observatory is sweet vindication. The beast is getting its due.

Geophysicists have known for 30 years that Yellowstone is a major volcanic system. But it took them so long to put their ears to the ground, Smith says, because they couldn't decide whether the Yellowstone system was active or in its death throes. Also, it doesn't look like a volcano.

It's just too big. From a viewpoint on the north rim of the caldera, a few miles from the Yellowstone River's Upper and Lower Falls, the southern edge of the caldera is obscured. It's more than 30 miles away - well within the large park but lost in the haze.

The last big eruption was 640,000 years ago. Since then, a series of smaller ones has filled in the caldera "like tubes of toothpaste squeezing out all over the place," says Smith. The 3,000-foot-thick glaciers of the last Ice Age erased edges of the caldera, which is a broad, undulating plateau rimmed by mountains.

The ground has always shaken periodically around Yellowstone. But without the proper monitoring equipment in place, no one knew how often it happened or why. Smith, who has been investigating here for more than 30 years, set up seismometers and found earthquakes by the hundreds.

The Basin and Range country that extends from California to Montana is one of the most seismically active regions east of California's San Andreas Fault. It is being stretched apart as tectonic plates beneath it move.

But the earthquakes Smith started tracking three decades ago - 15,000 between 1973 and 1998, often in clusters - didn't completely fit conventional notions of seismic activity. Along with quakes along fault lines perpendicular to the stretching, which might be expected, there were also some along parallel fault lines, which seemed to have no relation to the stretching.

A volatile landscape

Smith started thinking about the quakes in combination with Yellowstone's famously unstable plumbing. Was it possible, scientists asked, that the quakes and the geysers were products of volcanic action, of underground magma flows?

Yellowstone is clearly a volatile landscape. The ground, the hot- test in North America, steams. Pools of sapphire and opaline water bubble. Thick, white minerals encrust the land. Sulfur wafts through the air. And geysers such as Old Faithful erupt.

In 1965, a team led by Robert Christiansen of the U.S. Geological Survey mapped the caldera and lava flows in detail while NASA tried out a new remote-sensing technology in the region.

"It was not a surprise it was a young volcano," Christiansen recalls. "It was a surprise it was as young as it is."

He turned to Smith, whose seismic data would reveal whether the volcano was rumbling. Together, the two men were able to see the system for what it was: an active and large volcano that had sculpted much of the Northwest.

Smith and Christiansen saw evidence that a huge plume of magma rose from deep within the Earth and bore through the continental plate. As the plate moved southwest, the "hot spot" left a series of what Smith terms "ancient Yellowstones" across a 500-mile swath of southern Idaho from Oregon to Montana.

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