Another eruption of Mount St. Helens is not only likely, it’s pretty much a certainty.
But the combination of new instrumentation and decades of study by scientists, along with lessons learned from the event 40 years ago, means the public is much safer.
“It’s the best-monitored volcano in the Cascades,” said Seth Moran, the USGS scientist in charge at the Cascades Volcano Observatory. “The network lets us detect fairly subtle signs of unrest, and it tells us that there’s some magma movement that’s still going on since 2008.”
Tiny earthquakes of magnitude 1 or lower and small centimeter-by-centimeter movement of the ground show that geological activity continues. In April 2014, scientists noticed subtle deformations in the volcano’s surface area that also indicate the system is recharging, Moran said.
“It could be viewed as getting ready for the next eruption, years or decades down the road — and it’s still going today,” Moran said.
Other Cascade volcanoes are also restless — including Mount Hood and Mount Rainier, but Mount St. Helens still remains the most active in the chain.
“The other volcanoes in the Cascades, they like to let us know they’re also awake,” Moran said.
The geologic record indicates that Mount St. Helens erupts once or twice per century, including between 1800-1857. In comparison Mount Hood last erupted in 1781 and Mount Rainier last erupted about 1,000 years ago. In Northwest Washington, Mount Baker erupted fairly recently, in the 1870s.
“Any of the major Cascades volcanoes has the potential to erupt in our lifetimes,” Moran said. “The next time it gets restless, that will be the next stage for us to ask new questions and find even more answers.”
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