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Photo by Jonathan Weyn.

35 Years After the Eruption: Living with the Legacy of Mount St. Helens

Geologist Carolyn Drieger narrowly avoided dying in the destructive blast of Mount St. Helens' eruption in 1980. Thirty-five years later she reflects back on the lessons and legacy in the years since | by Carolyn Driedger

“It was the day that changed our lives.”

Imagine sitting on a giant clock, knowing that the alarm is set and will go off soon—but not knowing exactly when. That describes the mindset of geologists 35 years ago as they observed Mount St. Helens’ reawakening. They made measurements and warned of more substantial eruptive activity. The clock continued to tick until the alarm rang at 8:32 a.m. on May 18, 1980.

The massive collapse of the north flank of Mount St. Helens, followed by the lateral blast, buried streams, forests and valleys in rocky pyroclastic debris. Now, life returns as the mountain rebuilds itself. Photo by Ashley Gossens. Inset: the iconic profile of Mount St. Helens prior to its 1980 eruption. Photo by Harry Glicken, USGS.

March 20, 1980

After 123 years of slumber—and consequent indifference from Northwest residents for much of that time—Mount St. Helens reawakened. It began with a flurry of earthquakes, followed by a small eruption at the snow-covered summit that opened a 250-foot-wide crater. Within a week, the crater broadened to 1,300 feet and giant cracks splintered the summit. Throughout the remainder of March and much of April, minor eruptions rocked the peak hourly. All of that was worrisome, but the alarming thing was a growing bulge on the volcano’s north flank, which was expanding at a rate of 6.5 feet per day. Magma was rising into the volcano.

May 17, 1980

The activity at Mount St. Helens attracted no shortage of scientific attention. My colleague Mindy Brugman and I visited the volcano to pursue her research on how an awakening volcano affects its glaciers. On May 17, the project took us to the Timberline parking lot beneath the expanding bulge. We then visited geologist David Johnston on the ridge directly north of the volcano. Our original intent had been to remain on the ridge overnight; the next morning we would take a helicopter trip to Shoestring Glacier. But Johnston’s cautions about potential bulge failure persuaded us to leave for the night. We headed south to Vancouver, with a new plan to approach Shoestring Glacier the next day by car. That change of plan saved our lives.

May 18, 1980

The next morning, as Brugman and I drove north on I-5 from Vancouver, a mighty black cloud emerged from the north flank of Mount St. Helens. It billowed and flowed over high terrain to the north. This perplexed us, but within seconds, Brugman mouthed what each of us could barely comprehend—that Johnston’s apprehensions had come true: the north flank had failed. Mount St. Helens had erupted catastrophically.

Brugman mouthed what each of us could barely comprehend—that Johnston’s apprehensions had come true: the north flank had failed. Mount St. Helens had erupted catastrophically.

By the evening of May 18, 1980, Mount St. Helens had the attention of the world. Reports circulated about one of the largest historical landslides on Earth and how it had swept away the volcano’s northern flank. That massive debris avalanche unleashed a sideways blast that destroyed 230 square miles of timber. Billions of rock fragments shot skyward in a volcanic ash plume that reached a height of 80,000 feet in just 15 minutes.

In towns across Central and Eastern Washington, Idaho and Montana, wind-blown ash filled the sky like a giant veil and turned daylight into darkness. Lahars (volcanic mudflows) swept down two branches of the Toutle River, Smith and Pine Creeks and Muddy River.

The eruption reshaped the volcano, creating the distinctive crater we recognize today, and transformed the surrounding landscape and ecology. Trails and familiar landscapes disappeared beneath the debris avalanche, which roared into Spirit Lake and raised its level by more than 200 feet. In a matter of minutes, the avalanche dammed tributary streams of the North Fork Toutle River, forming what we now know as Coldwater and Castle Lakes. The 1980 eruption of Mount St. Helens resulted in the loss of 57 people, including Johnston, and was the most costly volcanic disaster (to the tune of $1 billion in 1980 dollars) ever in the United States.

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A legacy of education

Overnight, Mount St. Helens morphed from being a symbol of the good life in the Pacific Northwest to a cataclysmic destroyer. But in the years since, it has also assumed the role of master teacher of everything from science to safety. More than destruction, this education is the true legacy of Mount St. Helens.

Advancing volcano science

Since the eruption of Mount St. Helens, our understanding of how volcanoes work has grown by leaps and bounds. We now know that the lava-dome building eruptions of 2004 through 2008 were fed by magma left over from the 1980s eruptions. The massive debris avalanche at Mount St. Helens we now understand to be commonplace (on a geologic timescale) for volcanoes in the Cascades, on the ocean floor and on other planets. Earthquakes, ground deformation and gas measurements have taken on new meaning as scientists have learned that patterns of change can help them make short-term eruption forecasts. In years since Mount St. Helens’ 1980 eruption, volcano monitoring has evolved from the placement of a few scientific instruments on a volcano’s flanks to a broad, integrated network of devices that can measure earthquakes, deformation and volcanic gases, as well as detect eruptions or volcano-related changes in the earth’s surface from space.

Thanks to these better monitoring systems, geologists now know that Cascade volcanoes are inherently restless during non-eruptive times. Since 2004, seismographs have detected earthquake swarms at or near Mount Rainier, Mount St. Helens, Mount Hood, Three Sisters, Newberry Volcano and Lassen Peak. During the same time period, satellite and ground-based deformation monitors have identified surface uplift at the Three Sisters, subsidence at Medicine Lake Volcano and Lassen Peak, and both subsidence and uplift at Mount St. Helens. The earlier we see symptoms of impending volcanic activity, the more time we have to become prepared.

This slow accumulation of magma could continue for centuries, or it could cause another eruption within our lifetimes.

In addition to detecting more volcanic activity around the Cascade Range, advancements in volcano science have also given us more insight into Mount St. Helens. The dome-building eruptions of 1980 to 1986 and 2004 to 2008 illustrate that while not in eruption at this very moment, Mount St. Helens remains a fully functioning active volcano. Careful measurements of swelling reveal that magma continues to accumulate beneath Mount St. Helens, and current earthquake studies confirm this. This slow accumulation of magma could continue for centuries, or it could cause another eruption within our lifetimes. When the volcano becomes more restless, scientists will warn authorities and the public so that they can keep clear.

Lessons in volcano preparedness

In 1980, people across the state of Washington and into the Midwest experienced the effects of an eruption firsthand. Millions more watched it on television. Powerful images of previously unimaginable events heightened people’s awareness about the problems caused by volcanoes and the need for community preparedness. With improved understanding of volcano behavior, and with new types of more sensitive monitoring instruments, scientists can provide better warning about the timing and style of an eruption.

Concerns for citizen safety have prompted installation of additional monitoring sites, as well as contingency planning and communication among scientists, residents, emergency managers and the media. Officials and scientists have developed and periodically exercise emergency coordination plans, aid interpretive staffs, offer teacher workshops and courses for the public and each year commemorate May as Volcano Preparedness Month. Volcanoes can have short warning periods, but thanks to better monitoring technology, more advanced community planning and the memory of a society that has already witnessed an eruption, we’re better prepared than ever for the next eruption.

Hiking in volcano country

Recreating at Mount St. Helens (taking a hike, learning at the visitor’s center, taking a field course), reading eyewitness accounts of the 1980 events, getting to know the other Cascade volcanoes and making sure that your community is prepared—these are some of the best ways to appreciate the legacy of Mount St. Helens. Visitors don’t need to be worried about hiking on or around a volcano. They should be alert, as they would be along any trail, use common sense, obey closures and steer clear when advised of renewed volcanic unrest. Rising magma will provide scientists with some warning, commonly days or more in advance.

Hikes at Mount St. Helens are proof that dramatic geological processes create spectacular scenery. With much of the forest eliminated during the catastrophic eruption, most trails offer grand vistas of Mount St. Helens and other Cascade volcanoes. Nowhere else in the Cascades can hikers view such fresh volcanic landscapes and rapidly evolving ecosystems. There is a trail type for everyone, as well as ranger-led walks, classes and world-class interpretive facilities. A visit to the volcano might be the closest you will ever come to a historical event of epic proportions. Mount St. Helens has a dynamic past, and its future will be similar. Enjoy it in the interlude.

Carolyn Driedger is a hydrologist and the outreach coordinator at the USGS Cascades Volcano Observatory in Vancouver, Wash. She works in partnership with public officials, emergency managers, media, park interpreters and educators to advance the cause of volcano preparedness in the Cascade Ranger.

This article originally appeared in the May+June 2015 issue of Washington Trails magazine. Support trails as a member WTA to get your one-year subscription to the magazine.