Indians of the Pacific Northwest called it Louwala-Clough -- smoking mountain. Part of the Cascade Range, it was christened Mount St. Helens by George Vancouver and the officers of HMS Discovery during their exploration of the coast in 1792, named for the Baron St. Helens, the British diplomat Alleyne Fitzherbert. With a summit altitude of 9,677 feet, Mount St. Helens was only the fifth highest peak in Washington state, but it proved to be the most troublesome. Recognized early on as a volcanic cone, it was particularly active between 1831 and 1857. Then, for more than 120 years, Mount St. Helens was quiescent. Its surroundings, Gifford Pinchot National Forest, became a popular recreational area. The mountain itself was called the "Fuji of America" because its symmetrical, snow-capped peak was reminiscent of the famous Japanese landmark. But in 1980 the volcano awakened from its long slumber, with disastrous results.
The tragedy's sequence of events began with a series of low magnitude shocks starting on March 19 and culminating in a major earthquake (4.2 on the Richter scale) on March 20. More seismic activity followed, increasing in intensity on March 25. In the next 48 hours, 176 shocks registering 2.6 or greater were recorded. On March 27, Mount St. Helens erupted ash and steam -- the first eruption in the United States since activity at California's Lassen Peak in 1917. The eruption created a 250-foot crater at the summit and, later, a second crater, as the volcano continued to spew ash through April 21. Seismographs picked up volcanic tremor, distinguishable from the sharp shocks associated with earthquakes by its continuous rhythm. This was indicative of magma and gas in motion within the mountain. A cryptodome, or "bulge," appeared at the summit on March 27, the date of the first eruption, and continued to grow. By May 12 this bulge, acting like a cork in a bottle, was being expanded by magma intrusion and growing five feet a day. Most of the growth was horizontal, deforming the summit of the mountain. By mid-May 10,000 earthquakes had been recorded. It was clear to geologists that the volcano was highly unstable, and most inhabitants were evacuated from the immediate vicinity.
Early in the morning of Sunday, May 18, geologists Keith and Dorothy Stoffel were in a small plane flying over the volcano summit when they witnessed a massive landslide. "The entire mass began to ripple and churn up, without moving laterally," they reported. "Then the entire north side of the summit began sliding . . . ." Just as they started to take photographs a huge explosion occurred. The pilot executed a steep dive to gain speed and barely managed to escape the mushrooming eruption cloud.
David A.. Johnston, a volcanologist working for the U.S. Geological Survey (USGS), was manning an observation post six miles north of Mount St. Helens when the eruption occurred. At 8:31 A.M. he radioed in -- "Vancouver, Vancouver, this is it!" Seconds later, gases trapped inside the volcano exploded with a force 500 times greater than the bomb that had destroyed Hiroshima, blowing the top off the peak. An earthquake registering 5.1 on the Richter scale had caused the landslide which uncorked the volcano and released the pent-up fury inside Mount St. Helens, triggering the worst volcanic disaster in United States history. A lateral blast carrying volcanic debris at a speed of at least 300 miles an hour caused terrible devastation for a distance of nineteen miles. Caught within the direct blast zone, David Johnston was killed. Flattening everything in its path, the blast mowed down entire forests, killing two backpackers camped fourteen miles away.
Photographer David Crockett, employed by Seattle's KOMO-TV, was walking on a logging road at the base of the mountain when the explosion occurred. He looked up to see a landslide of mud and debris hurtling towards him. Fortunately, the slide separated to pass on either side of the road. Blinded by a cloud of burning ash that turned day into night, Crockett stumbled away, speaking into his sound camera. "Oh dear God, this is hell! It's either dark or I'm dead." Ten hours later Crockett was located and rescued by a search helicopter.
A massive volcanic debris flow, traveling as fast as 50 miles per hour, struck the Toutle River drainage, destroying everything in its path. In all, 200 homes, 27 bridges, and 185 miles of roadway were lost. Mudflows dumped millions of cubic yards of sediment into the Cowlitz and Columbia Rivers. The Toutle River crested 21 feet above normal, while its north fork was buried to an average depth of 150 feet. The mudflows averaged 33 to 66 feet in depth, but in places they swept completely over 250-foot hills.
The mushroom-shaped ash cloud rose 16 miles above the volcano, which continued to emit ash for nine hours. Moving at 60 miles per hour, the ash cloud reached Yakima and Spokane and fell on those cities like dirty snow, turning the day so dark that street lights were activated. Airports in eastern Washington were shut down. Interstate 90 was closed, and remained so for a week. Within 24 hours prevailing winds had distributed the fallout across the Rocky Mountain states. Schools, factories and stores were closed in the Idaho panhandle and western Montana. Over 200,000 people were temporarily put out of work. Ash blew out transformers, causing blackouts. All told, an estimated 540 million tons of ash were distributed over an area of 22,000 square miles.
The May 18 eruption claimed 57 lives. Most died by asphyxiation after breathing hot volcanic ash. About 7,000 game animals and most birds and small mammals in the immediate vicinity of the eruption were killed; 12 million salmon fingerlings were lost in destroyed hatcheries. Approximately 4 million board feet of salable lumber -- $600 million worth -- was decimated; that summer, 600 truckloads of lumber were retrieved per day in timber-salvage operations. Nearly $200 million worth of damage was done to crops, though in the long term ash deposits added nutrients to the soil. Congress approved $951 million in disaster relief.
As it had in the mid-19th century, Mount St. Helens went through a period of eruptive activity that lasted through the Eighties. The volcano exploded again on the Sunday following the May 18 eruption, producing an ash column that reached an altitude of nine miles. On June 12 there was yet another eruption. The time magma formed a lava dome on the crater floor that was 1,200 feet in diameter. An explosive episode on October 16-18 proved to be the last major activity, though minor events occurred throughout 1983, in the spring of 1984, the spring of 1985, the spring and fall of 1986, and in December 1989.
Long-term effects of the eruption included increased hazards of catastrophic flooding due to the rearrangement of local terrain by volcanic debris that blocked parts of the area's natural drainage system. For years the Corps of Engineers labored to prevent serious floods by building debris dams and controlled outlets for overflowing lakes and reservoirs. The USGS opened a permanent regional office in Vancouver, Washington to monitor Mount St. Helens and other Cascade Range volcanoes. The observatory, named after David A. Johnston, the volcanologist who lost his life during the eruption, was one of only three such facilities operated by the USGS -- the other two were in Hawaii and Alaska. On May 18, 1983 the Mount St. Helens National Volcanic Monument was dedicated. It was the only monument of its kind in the nation, and by the end of 1989 had been visited by 1.5 million tourists.