Volcanoes Strung Along Cascade Range Define Picturesque Powder Keg : Northwest: An average of two eruptions a century have occurred in the Cascades over the last 4,000 years. Majestic Mt. Rainier is considered the most dangerous today.

The pre-dawn earthquake that shook the foothills of Mt. Rainier in September was mild. But it was enough to remind residents of the Pacific Northwest that they live on top of a picturesque powder keg.

Nowhere is nature’s beauty-and-beast behavior more compelling than along the Cascade Range that stretches 1,000 miles from southern British Columbia to Northern California.

But beneath snowcapped peaks, green forests and flowering alpine meadows churns one of the biggest chains of active volcanoes in the world.

Fourteen large volcanic centers in the American portion of the Cascades have erupted before. “And they all could do it again,” warned Dan Dzurisin, the scientist in charge of the U.S. Geological Survey’s Cascades Volcano Observatory here.

Over the last 4,000 years, an average of two eruptions a century have occurred in the Cascades. Majestic Mt. Rainier, just 40 miles southeast of Seattle, is considered the most dangerous today.

“For millions of years, the pattern has been long periods of quiet punctuated by brief eruptions,” Dzurisin said. “There’s no reason to think this isn’t exactly what’s happening now.

“The fact that there hasn’t been an eruption for several years, or several hundred years, doesn’t mean the volcanoes are extinct. It just means that they’re in an in-between period. Eruptions are coming.”

Dzurisin emphasizes that geologists are not predicting imminent major explosions. “It could be decades, it could be centuries. But history tells us it will happen again.”

During the 37-million-year history of the Cascades, entire volcanoes have built up, collapsed, eroded away and been replaced by new ones.

Seven Cascade volcanoes have erupted since American independence in 1776. Mt. St. Helens in 1980 still ranks as the worst volcanic disaster in modern U.S. history. Fifty-seven people died.

Worldwide, the 1980s were one of the most volatile decades of volcanic devastation ever recorded, causing more than 28,500 deaths.

“It’s not that the world’s volcanoes are becoming more active, but that population pressures are causing more people to live near dangerous volcanoes,” Dzurisin said.

That is one of the reasons why Mt. Rainier, which is a threat to 2.5 million people in the Seattle-Tacoma area, is among several volcanoes targeted by an international volcanology association for special study.

Geologists are convinced that Rainier, built by countless eruptions during its half-million-year history and recently active with minor eruptions and earthquakes, will explode again, spewing suffocating blankets of ash and sluggish lava flows.

The greatest danger, however, is likely to come from debris flows, mixtures of water-saturated earth, rock and debris that can move at speeds of up to 100 m.p.h. and destroy distant communities.

At 14,410 feet, Mt. Rainier is the highest volcano in the Cascade Range. Its steep slopes are packed with vast amounts of potentially lethal ice and snow.

Rainier’s largest known debris flow, 5,000 years ago, spread over 60 miles to bury the valley where Enumclaw, Buckley and other towns now stand. A flow of that magnitude would be catastrophic today.

“We cannot prevent volcanic activity,” Dzurisin said, “but we can prepare for it and mitigate its effects.”

Unlike earthquakes, which usually strike without warning, volcanoes almost always send signals of impending trouble--days, weeks, even months ahead of time.

The Cascades Volcano Observatory, established during the Mt. St. Helens eruption, takes the pulse of these volcanoes. With a staff of 70 geologists, geophysicists, geochemists, hydrologists and cartographers, it is the largest of the Geological Survey’s three such stations. The others are in Hawaii and Alaska.

“We aren’t able to intensively monitor all the volcanoes,” Dzurisin admitted. “You might wait 100 years and not see anything at some of them.”

The observatory concentrates on studying past eruptive behavior and on developing a “rapid response” capability for future emergencies. It also works with local officials on land-use planning and tries to educate the public.

“We’re not trying to scare people or force them to move away,” said Dzurisin. “We just want them to be aware of the dangers and to prepare.”

“It’s absolutely gorgeous here. We’d never think of leaving,” said Anita Glasco of Enumclaw, Wash., who has watched nine children and 36 grandchildren grow up in the shadow of Mt. Rainier.

“But you pay a price for your scenery. If an evacuation call comes, we’ll pack up and head out.”

But, like her neighbors, Glasco insists her family eventually would return and resume its uneasy relationship with the beautiful-but-belligerent Cascade volcanoes.