40: Mt St. Helens

Mount St. Helens Erupts

Mount St. Helens in Washington erupts, causing a massive avalanche and killing 57 people on this day in 1980. Ash from the volcanic eruption fell as far away as Minnesota. Seismic activity at Mount St. Helens, which is 96 miles south of Seattle, began on March 16. A 4.2-magnitude tremor was recorded four days later and then, on March 23-24, there were 174 different recorded tremors. The first eruption occurred on March 27, when a 250-foot wide vent opened up on top of the mountain. Ash was blasted 10,000 feet in the air, some of which came down nearly 300 miles away in Spokane. The ash caused static electricity and lightning bolts.

Authorities issued a hazard watch for a 50-mile radius around the mountain. The National Guard set up road blocks to prevent access to the area, but these were easily avoided by using the region’s unguarded logging roads. Many residents of the area evacuated, but a substantial number refused. Harry Truman, 84—no relation to the former president—was one resident who refused to move and, after receiving a great deal of positive media coverage for his decision, became a national icon as well as, later, the subject of a local memorial. Throughout April, scientists watched a bulge on the north side of Mount St. Helens grow larger and larger. Finally, on May 18 at 8:32 a.m., a sudden 5.1-magnitude earthquake and eruption rocked the mountain. The north side of the peak rippled and blasted out ash at 650 miles per hour. A cloud of ash, rocks, gas and glacial ice roared down the side of the mountain at 100 mph. Fourteen miles of the Toutle River were buried up to 150 feet deep in the debris. Magma, at 1,300 degrees Fahrenheit, flowed for miles.

The 24-megaton blast demolished a 230-square-mile area around the mountain. Geologist Dave Johnston was the closest to the eruption when it blew. He was on his radio that morning and was only able to say, Vancouver, Vancouver, this is it! before his truck was pushed over a ridge and he was killed.

Millions of trees were scorched and burned by the hot air alone. When the glacier atop the mountain melted, a massive mudslide wiped out homes and dammed up rivers throughout the area. The plume of ash belched out for nine hours; winds carried it across the state and as far away as Minneapolis, Minnesota. The falling ash clogged carburetors and thousands of motorists were stranded. Fifty-seven people died overall from suffocation, burns and other assorted injuries. Twenty-seven bodies, including that of the stubborn Harry Truman, were never found. Mount St. Helens went from 9,600 feet high to only 8,300 feet high in a matter of seconds.

https://www.history.com/this-day-in-history/mount-st-helens-erupts