Mount St. Helens is rumbling again, but it‘s not the volcano that worries Washington state seismologists the most.
A 3.9-magnitude jolt Wednesday morning, about 11 km northeast of the volcano, was the strongest tremor in the seismically active area since 1981. It was followed by a swarm of up to 150 smaller earthquakes.
In 1980, an eruption blew out the side of the volcano, killing 57 people and devastating the landscape. Cascades of water, mud, and rock raged down valleys and knocked down forests.
But the latest quakes do not signal that the volcano is moving closer to another eruption, seismologist Seth Moran told host Gregor Craigie.
“There are earthquakes that are occurring at Mount St. Helens kind of continuously,” said Moran, who is a seismologist and scientist-in-charge at the United States Geological Survey‘s Cascades Volcano Observatory.
The most hazardous volcano in Washington state is considered by seismologists to be Mount Rainier, where volcanic mud flows, called lahars, roar down the Puyallup River drainage system every 500 to 1,000 years.
“That‘s a long time from a humanity perspective, but from a geologic perspective that‘s pretty frequent and a really good reason for believing it‘s going to happen again,” Moran said.