Mount St. Helens Erupts Summary

  • Last updated on November 10, 2022

The eruption of Mount St. Helens greatly altered the physical landscape of southwest Washington, giving scientists a rare opportunity to record the destructive and recuperative powers of nature.

Summary of Event

“Vancouver, Vancouver, this is it!” Transmitted from his observation camp just five miles north of the mountain, the excited voice of geologist David A. Johnston was the first to announce the eruption of Mount St. Helens. The thirty-year-old volcano specialist had been observing the cone-shaped mountain for more than five weeks, and was monitoring a five-hundred-foot bulge growing out of its northern face. His broadcast to fellow scientists at U.S. Geological Survey headquarters in Vancouver, Washington, was the last communication ever received from Johnston. He was the first of fifty-seven people to die on what looked to be another quiet spring morning within the shadow of Mount St. Helens. Volcanoes;Mount St. Helens[Mount Saint Helens] Mount St. Helens[Mount Saint Helens] Disasters;volcanic eruptions [kw]Mount St. Helens Erupts (May 18, 1980) [kw]St. Helens Erupts, Mount (May 18, 1980) Volcanoes;Mount St. Helens[Mount Saint Helens] Mount St. Helens[Mount Saint Helens] Disasters;volcanic eruptions [g]North America;May 18, 1980: Mount St. Helens Erupts[04180] [g]United States;May 18, 1980: Mount St. Helens Erupts[04180] [c]Disasters;May 18, 1980: Mount St. Helens Erupts[04180] [c]Environmental issues;May 18, 1980: Mount St. Helens Erupts[04180] Johnston, David

Although the size and character of the May 18, 1980, eruption caught many people off guard, the volcanic history of Mount St. Helens was well known by scientists. Geologic records document an eruptive history dating back thousands of centuries, marking Mount St. Helens as the most active and most violent of all the known volcanoes in the contiguous United States. Northwest Native Americans called the mountain Loo-wit (Keeper of the Fire) or Tah-one-lat-clah (Fire Mountain), and stories of “earth thunder” and falling ash are strung throughout the folklore and traditions of Pacific Northwest tribes. The first Caucasian account of an eruption was recorded in 1836. Dr. Meredith Gairdner, a medical officer at Fort Vancouver, wrote of three days of haze and ashfall that, upon clearing, revealed a mountain “deeply furrowed and destitute of snow.” Numerous accounts exist of subsequent eruption periods, the longest occurring from 1842 to 1843. By the beginning of the 1980’s, however, the mountain had been dormant for nearly 125 years, an interval that geologists expected would end before the close of the twentieth century.

Mount St. Helens began to stir from its long dormancy in late March of 1980. Small earthquakes, some as strong as 4.4 on the Richter scale, were recorded from beneath the mountain. On March 27, a traffic reporter flew close to the mountain summit, which was hidden from the view of ground observers due to heavy cloud cover, and witnessed a black plume of steam and ash shooting seven thousand feet upward from a two-hundred-foot-wide crater. Numerous small eruptions of steam and ash continued to entertain the hundreds of spectators who had come to see the volcano, but by mid-April the bursts of ash and steam stopped, leading many to believe that the volcano had become dormant once again.

Emboldened by the lull in activity, land and cabin owners within the vicinity of Spirit Lake, which was nestled just below the treeline along the northern slope of Mount St. Helens, demanded that they be granted access to their property. Months earlier, when the volcano was active, Washington governor Dixie Lee Ray had ordered the closure of all highways into what had been established as the “red zone” around the mountain, making it off-limits to the public. When the volcano quieted, property owners demanded permission to enter the zone and retrieve family heirlooms, pets, and other belongings. On Saturday, May 17, a caravan of twenty property owners, accompanied by an entourage of reporters, photographers, and emergency personnel, made the journey to Spirit Lake. Four hours later, they drove back down the valley of the Toutle River, their trunks and backseats filled with personal belongings and family heirlooms. Another caravan was scheduled for ten o’clock the next morning.

During those weeks of outward calm, scientists were busily studying changes in the once-symmetrical shape of Mount St. Helens. Using laser technology, scientists identified a peculiar bulge rising up from the northern flank of the mountain at a rate of nearly five feet per day. Scientists speculated that the bulge was caused by superheated magma being forced through the cracks and fissures beneath the mountain’s surface. It was apparent to those monitoring the situation that the outward calmness of the mountain belied the turmoil occurring beneath its surface.

The morning of May 18 was bright and quiet around the mountain. The noise of log trucks, chainsaws, and heavy machinery was absent, as most of the loggers working within and around the red zone were enjoying their Sunday off. Except for the morning rituals of a handful of scientists, journalists, and volcano watchers who had eluded the roadblocks and had illegally camped in the restricted area, Mount St. Helens appeared to be lifeless.

At 8:32 a.m., an earthquake of Richter magnitude 5.1 rumbled through the mountain. Suddenly, the bulging northern face began to collapse, triggering a massive landslide down the mountain’s flank and into Spirit Lake. A fraction of a second later, glacial ice and groundwater came into contact with the superheated magma, instantly flashing into steam. A mixture of steam, explosive gases, and volcanic debris formed a dense cloud that stormed down the mountain slope. With estimated temperatures exceeding 600 degrees Fahrenheit and driven by hurricane-force winds, the cloud scoured the ridges and hillsides within a six-mile radius of the mountain, denuding them of soil, vegetation, and life. Plants and forests caught in the flow of this superheated volcanic storm were instantly vaporized. Outside the inner blast zone, large trees were torn up by their roots or snapped off at their trunks and were scattered like matchsticks along the hillsides.





A giant plume of volcanic ash, gas, and steam boiled seventy thousand feet into the atmosphere above the newly created crater. An estimated 540 million tons of ash spewed from the volcano during the first nine hours of the eruption, spreading a coat of volcanic ash across twenty-two thousand square miles. Communities east of the volcano found themselves in a dry “snow” storm that buried them beneath four to twelve inches of ash.

Giant rivers of mud, created by the rapid melting of glacial ice, engulfed entire forests and gorged deep canyons into the sides of the mountain. Picking up trees, boulders, logging equipment, and even houses, the mudflows rumbled down river valleys at speeds in excess of seventy miles per hour. More than 100 million cubic feet of sediment were transported down streams and rivers, knocking down bridges, damming side streams, and burying highways, farms, and houses beneath six to ten feet of warm mud.

The mudflows, as well as the other destructive forces unleashed by the eruption, devastated much of the land and life around the volcano. The initial eruption was equivalent to a nuclear blast five hundred times larger than the bomb dropped on Hiroshima. A 234-square-mile swath, barren of vegetation and covered with a coating of volcanic ash, fanned outward from a smoldering Mount St. Helens. The lush green forests, lakes, and multicolored flowers that had attracted so many to Mount St. Helens for decades had been replaced by the gray hues of a lunar landscape. The eruption was perhaps the most photographed and recorded in history, and the overwhelming destruction of May 18 appeared in newspapers and on televisions around the world.


The catastrophic destruction of Mount St. Helens gave scientists a unique opportunity to study and monitor the recovery of not only a volcano but also an entire ecosystem. Nature had wiped the slate clean in a tiny section of southwest Washington, and scientists had the opportunity to watch the rebirth process—a natural experiment too impractical to have been tried before. What they discovered was a recovery process that refused to adhere to a particular scientific model or to follow textbook descriptions and expert opinions.

The natural environment had suffered the most drastic effects. Dramatic changes in the forest ecosystem caused many scientists to question the ability of the environment to bounce back. In a matter of minutes, nearly five billion board feet of timber had been destroyed, an amount roughly equal to the combined annual timber harvests of Washington and Oregon. Most of the devastated area had been covered with ash—in some places up to seven feet deep—blocking seeds from reaching the fertile soil beneath or smothering young seedlings from needed sunshine. Because of the restricted access to fertile soil, scientists believed that several years would pass before the grasses, flowers, and trees would return to the devastated area.

However, only months later, after the ash had cooled, tiny oases of plants began to dot the “lunar” landscape—thanks in part to the activities of the pocket gopher, one of the eruption survivors. Overlooked by scientists, the pocket gophers burrowed through the ash as though they were little snowplows, mixing the ash with the organically rich soils and pushing it to the surface. Fireweed, lupine, and thimbleberry seeds, carried by the wind into the devastation zone, quickly took root on the fertile pocket gopher mounds. These plants attracted insects, which attracted birds. The contrasting colors of green vegetation on the gray ash attracted foraging mammals into the devastated area. Nature was clearly on its way to re-creating what had been destroyed by the eruption.

Beneath the hot blanket of ash, tremendous amounts of organically rich materials were literally baked under the intense heat. At the time of the blast, the plants and trees within the devastation zone had been about to burst forth in their spring foliage. The baking of resins, juices, and other organic matter in the buried material produced a potpourri of organic chemicals, particularly phenols, which drained out of the ash and into nearby lakes, streams, and ponds.

Spirit Lake, like many other lakes in the blast zone, was sterilized by the intense heat of the eruption. For years after the eruption, harmful soluble metals, ash, and volcanic rock washed down the steep slopes into the lake, frequently burying bottom-dwelling animals. Organic chemicals oozing from the ash began to accumulate in the lake, attracting new life in the form of bacteria, mold, and fungi, which turned the murky waters to shades of crimson, green, and red. The raging bacterial growth quickly consumed the oxygen in the water, making way for non-oxygen-dependent organisms to colonize.

Beyond the blast zone, frogs and salamanders, protected beneath bottom sediments during the blast, surfaced with no apparent ill effects. Where the ice was thickest and the ashfall light, muskrats, mink, and fish also survived. A decade later, the lakes affected by Mount St. Helens had essentially returned to their normal state. Even the chemical composition of Spirit Lake returned to preeruption levels. Oxygen levels and water quality again became high enough to support salmon and steelhead in those lakes and streams with access to the ocean.

Three years after the eruption, 90 percent of the plant and nearly all the mammal species believed to have inhabited the area before the eruption had been observed in smaller populations in the devastated area. Contrary to textbook knowledge about the natural recovery processes associated with natural disasters, regeneration was highly dependent on surviving animal and plant species, not solely on the ability of colonizing species to migrate into the devastated area. Scientists watched in fascination as species which survived the eruption, along with colonizing plants and animals, worked to heal the damaged environment at a pace never thought possible.

One of the more obvious changes occurring in the devastated areas surrounding Mount St. Helens is the ever-increasing number of tourists. Millions of people come to the monument annually to witness the destruction and the recovery of North America’s most famous volcano. Millions of dollars have been spent in the construction of highways, visitor centers, gift shops, trails, and viewpoints to enhance the tourist experience. The spectacle of increasing numbers of humans tromping across such a unique landscape repulses many scientists, but others see such visits as essentially beneficial. Proponents argue that viewing Mount St. Helens and the surrounding devastation gives people an opportunity to witness nature’s awesome power to destroy and then give life to the planet, encouraging them to be more aware of the interconnectedness of living things in the global environment. Volcanoes;Mount St. Helens[Mount Saint Helens] Mount St. Helens[Mount Saint Helens] Disasters;volcanic eruptions

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Carson, Rob. Mount St. Helens: The Eruption and Recovery of a Volcano. 1990. Rev. ed. Seattle: Sasquatch Books, 2002. A pictorial and written account of the catastrophic volcanic explosion and subsequent recovery of Mount St. Helens and the surrounding region. This twentieth anniversary edition includes updated material.
  • citation-type="booksimple"

    xlink:type="simple">Dale, Virginia H., Frederick J. Swanson, and Charles M. Crisafulli, eds. Ecological Responses to the 1980 Eruption of Mount St. Helens. New York: Springer, 2005. A thorough synthesis of twenty-five years of ecological research since the 1980 eruption.
  • citation-type="booksimple"

    xlink:type="simple">Harris, Stephen L. Fire and Ice: The Cascade Volcanoes. Rev. ed. Seattle: Mountaineers-Pacific Search Press, 1980. Overview of the volcanic and glacial history of the Cascade Mountains in the Pacific Northwest. Explains the geological forces that created the prominent volcanoes of the Cascades and the potential hazards of future eruptions.
  • citation-type="booksimple"

    xlink:type="simple">Rosenfeld, Charles, and Robert Cooke. Earth Fire: The Eruption of Mount St. Helens. Cambridge, Mass.: MIT Press, 1982. A scientific examination of the geologic forces and activities leading up to the blast and the role of computerized imagery in analyzing the eruption. Includes descriptions of the cultural impacts experienced within the region.
  • citation-type="booksimple"

    xlink:type="simple">Shane, Scott. Discovering Mount St. Helens: A Guide to the National Volcanic Monument. Seattle: University of Washington Press, 1985. Reviews the geologic and human history of southwest Washington and the events surrounding the May 18 eruption. Provides excellent descriptions of recreational opportunities and includes appendixes for those interested in more technical aspects of the eruption and Mount St. Helens.
  • citation-type="booksimple"

    xlink:type="simple">U.S. Department of Agriculture. Forest Service, Pacific Northwest Region. Mount St. Helens National Volcanic Monument: Draft Environmental Impact Statement. Portland, Oreg.: Author, 1984. Describes the impacts of the May 18 eruption and possible management plans for the national volcanic monument. Highly technical.

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