Washington's Mount Rainier called 'monumental threat'

MOUNT RAINIER NATIONAL PARK, Wash. -- Wedding cake white and big beyond words, Mount Rainier floats above Puget Sound like a child's dream of what a mountain might be.

Dreams of Rainier come in handy here, for the mountain itself has a habit of disappearing in clouds for weeks or even months on end. The 3 million people who live in and around Seattle know, of course, that it is up here -- nearly 2 3/4 miles high, encased in glacial ice and fattening itself up every winter with more than 50 feet of fresh snow.

During this warm, dry and cloudless summer in the Pacific Northwest, astonishing views of Mount Rainier have been uncommonly common. Clear sightlines have made it possible to gaze at Rainier and appreciate it less as an intermittent aesthetic pleasure and more for what the U.S. Geological Survey warns that it really is.

"A monumental threat," said William E. Scott, scientist in charge of the Cascades Volcano Observatory, a USGS center that monitors volcanoes from California to Alaska.

Volcanologists determined in the late 1990s that the mountain is far more unstable than previously thought, and they have since persuaded local emergency management officials to launch an early-warning system and a major public-awareness campaign. Tens of thousands of people are being told to "enjoy the volcano in your back yard" but to be prepared to run away from it -- fast.

The town nearest Rainier has about 40 minutes to flee. Inside the national park that encircles the mountain, scientists in recent months have shortened the run-for-it survival time to five minutes.

Rotting from inside out

Beneath its snow, Mount Rainier is an active volcano, and it is rotting from the inside out, especially on its western flank, which drains toward population centers. The volcano has a long, spotty history of collapse and massive mudflows called lahars.

About 150,000 people now live atop lahars that have rioted down the slopes of Mount Rainier over the past 5,000 years.

About 500 years ago, which was the last time the mountain shrugged its rotting shoulders in a major way, mud came roaring down the valley. The rot in Rainier is caused by gas, which degrades rock and turns it into more fragile clay. With the consistency of concrete and traveling about 40 miles an hour, that lahar shredded a forest and reamed out a valley. The USGS calculates that Mount Rainier burps this way every 500 to 1,000 years.

"The bad news is that the window of opportunity is now open," said Steve Bailey, director of emergency management for Pierce County, where damage from Mount Rainier is most likely. "The good news is that the window is 500 years long."