• MLWA 7

Series of Earthquakes in and around Mt St. Helens Poses no Immediate Threats of Another Eruptions



— Mount Saint Helens


Four dozen earthquakes were detected at Mount St. Helens over the last month, but volcano seismologist Dr. Weston Thelen of the United States Geological Survey said it’s nothing to worry about.

While the volcano alert level hasn’t been raised, the swarm of activity is a reminder that Mount St. Helens is the most active volcano in the Cascade Range. It was the last to erupt, and likely also the next to erupt.


“This is not a sign that an eruption is coming. These are small earthquakes located right above where we think the magma chamber is, it may mean magma is moving around, feeding into the chamber,” said Thelen.

Mount St. Helens, Mount Rainier classified as 'very high threat' for eruption

“If they were larger or there were hundreds per day, that might cause a change to the alert level,” said Dr. Seth Moran, scientist-in-charge at the Cascades Volcano Observatory. “The two eruptions that we’ve watched happen both started with an incredible change in activity.”

Mount St. Helens last erupted from 2004 to 2008. Swarms of small earthquakes have happened several times a year in the decade since. These quakes are mostly between magnitude zero and one. Thelen explained that small quakes are detected because of the intensive monitoring at Mount St. Helens.


“The reason we have that dense array is because Mount St. Helens is more active than the other Cascade volcanoes. But even if you’re hiking on the rim, you wouldn’t feel these small earthquakes happening three or four miles below the surface,” Thelen said.