Lots of rumbling under Mount St. Helens, but scientists say no cause for alarm

There's been a lot of seismic activity under Mount St. Helens recently.

Between Feb. 1 and early June, seismologists documented roughly 350 small-magnitude earthquakes, the vast majority of which were too small to feel at the surface.

That much activity might sound alarming, but scientists say there’s no cause for concern.

“The things that are happening right now don’t look anything like what we see leading up to an eruption,” said Weston Thelen, research seismologist with the United States Geological Survey’s Cascade Volcano Observatory. “Volcanoes are really cool, and they’re dynamic, and they change. And just because they’re changing doesn’t mean that the next 1980 eruption is coming.”

The 1980 eruption of Mount St. Helens was the deadliest and most destructive in U.S. history. Thelen said the recent increased activity is not uncommon, and similar patterns can be found in records that go back to 1980.

He said the current cluster of quakes is consistent with something called "recharge," which is the arrival of additional magma, molten rock beneath the earth’s surface.

Thelen said he and his colleagues will be vigilant in monitoring seismic activity under the volcano and interpreting it with an open mind.

He said current monitoring systems would likely give about a week of notice prior to any future eruptions, big or small.