This anniversary of the eruption at Mt St Helens is met with news of renewed activity at the volcano in Washinton state. A swarm of tremors have been increasing since March.
For those of us who remember the eruption at Mt St Helens it’s hard to believe it was 36 years ago today. The eruption sent ash 80,000 feet into the air in just 15 minutes. The blast of 24 megatons of thermal energy blew the side and top off the volcano and claimed 57 lives.
(Video credit: CNN, reporter Patty Lane-30 year anniversary of eruption)
May 18, 1980, was a bright sunny Sunday morning in Washington state. A day earlier residents who lived around Mount St Helens had been allowed to briefly return to their homes to gather items. They had been evacuated because of recent activity at the volcano and concern of an eruption.
Volcanologist David Johnston was at an observation lookout post 6 miles north of the volcano and radioed in measurements from the volcano. At 8:32 a.m., (Pacific Daylight Time) a 5.1 magnitude earthquake was measured beneath the volcano triggering a “cataclysmic eruption” and massive landslide on the north flank of the volcano. the lateral blast took the top and side off the mountain sent out 24 megatons of thermal energy.
At 7 a.m. on May 18, 1980 According to USGS, the eruption “sent hot ash, pumice and pyroclastic flows out of the crater at 50 to 80 miles per hour and spread as far as 5 miles to the north.” The ash cloud reached 80,000 feet – in just 15 minutes.
Volcanologist Don Swanson had been monitoring Mount St Helens since March 1980. When the eruption began he jumped into a helicopter for a birds-eye view. He said the sight was unbelievable. “We had to believe it because we could see it…it was a very remarkable experience scientifically and emotionally that first day.” Swanson’s friend Dave Johnston was killed in that blast. Swanson was actually scheduled to be at that lookout post that day – but earlier asked Johnston to switch with him.
He estimates Johnston saw the blast coming his way. “It was quick but it would have taken enough time for this blast cloud to reach him that he would have seen it coming.” Several lahars, massive mudflow with pyroclastic debris, “poured down the volcano into river valleys, ripping trees from their roots and destroying roads and bridge.”
The eruption and landslide removed 1,341 feet from the top of the mountain leaving a massive crater. Fifty-seven people were killed by the eruption, including volcanologist Johnston, and many who were in areas thought to be safe.
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- Mt St Helens erupting Oct. 2004
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- USGS-Eruption 10/2004
(All photos in gallery by Patty Lane unless otherwise noted)
In 1982 the President and Congress created he 110,000 acre national Volcanic Monument for research, recreatioin an education at Mount St Helens. The area within 5 miles of the volcano was left to naturally return without disturbance for scientists and the public to witness nature renew.
Mount St Helens is the most active volcano in the Cascade Rage. Although the volcano has returned to a period of quiet, scientists with U.S.G.S and the University of Washington Geophysics Program continue to monitor the volcano for signs of activity.
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