Scientists reflect on the catastrophic 1980 Mount St. Helens eruption
By Ashley Williams, AccuWeather staff writer
May 18, 2018, marks 38 years since the Mount St. Helens eruption in Washington State that took 57 lives. The violent explosion of the Cascade Range’s most active volcano had been its first major event in over a century.
A series of small earthquakes at the volcano had begun a couple of months prior.
“On the afternoon of March 20, , a 4.0-magnitude earthquake took place at Mount St. Helens, and I immediately recognized that as something of interest,” said Dr. Stephen Malone, research professor emeritus at the University of Washington.
Malone studied volcano seismology as a research assistant professor in the university’s geophysics program in 1980.
In the weeks leading up to the May 18 eruption, researchers collaborated with volcano hazard experts at the U.S. Geological Survey (USGS) to monitor Mount St. Helens. According to Malone, the volcano’s first eruption occurred on March 27.
For the next two months, researchers continued to monitor the volcano’s earthquake activity, which seemed to decrease in terms of numbers of events.
“However, some of the earthquakes that were occurring were even bigger than the ones that had occurred before, so we were convinced this was not over," said Malone.
At 8:32 a.m. on May 18, a 5.1-magnitude earthquake shook the north face of Mount St. Helens, causing it to collapse and trigger an avalanche of rock debris. According to the Cascade Volcano Observatory (CVO), the debris avalanche was the largest on Earth in recorded history.
The CVO calculated the avalanche’s total volume at 3.3 billion cubic yards – equal to one million Olympic swimming pools. The blast measured at a VEI 5 on the Volcanic Explosivity Index, which is a relative measure of the explosive activity of volcanic eruptions.
“My hope had been that we would see some change in the earthquake activity, some additional number of events, types of events… something that would give us a warning before an eruption occurred,” said Malone.
Unfortunately, he said, this did not occur. However, people abandoned their homes and authorities blocked off roads in areas near the volcano, which saved many lives.
“There was quite a large area that was closed to the public,” said CVO research geophysicist Dr. Weston Thelen. “The area right around the volcano was pretty well-evacuated."
However, not all nearby residents vacated the dangerous area. Harry Truman, who lived six miles away at Spirit Lake, was nearest to the blast as it occurred. He was killed immediately.
The explosion and avalanche devastated nearly 150 square miles of forest, but surprisingly, not all lifeforms were lost in the destruction.
Only 2 percent of the landscape influenced by the blast had all life obliterated, said Charlie Crisafulli, research ecologist and lead Mount St. Helens researcher at the Pacific Northwest Research Station.
“In that 2 percent, that arguably makes the most interesting and compelling place to study, to see where life is starting from scratch,” said Crisafulli, who began studying the volcano in the weeks following the catastrophic eruption.
“We’ve learned that the single most important factor influencing how ecosystems respond following a disturbance is what is left behind,” he said.
The 1980 blast occurred in springtime while Mount St. Helens remained covered in snow, a factor that protected some organisms and even entire ecosystems from the blast.
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Had the eruption occurred two months later during summer, the ecological consequences would have been different, said Crisafulli.
“The [recovery] process may have taken decades longer based on what we saw based on a May eruption,” he added.
Now, decades later, the Mount St. Helens landscape has evolved from gray to green but still bears little resemblance to its appearance before the 1980 eruption.
“Our ability to forecast eruptions improves every time we monitor one of these,” Thelen said.
Advancements in technology since 38 years ago have allowed for scientists to better predict future volcanic activity.
"We have more seismometers on the cone," he said. Seismometers are very sensitive instruments that can detect movements of the Earth's surface.
"We [also] have better ways of detecting when the volcano is inflating or deflating," Thelen said.
“[These] provide us clues and give us a better idea of what’s going on in the volcano. That’s important for us to try to open up that forecasting window to longer and longer time periods,” he said.
As forecasting methods continue to improve, preparedness also remains at the forefront, as Washington State recognizes Volcano Preparedness Month throughout May. Residents in the area have the opportunity to learn about volcano hazards and the appropriate steps to reduce potential impacts.
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