A couple of quakes were reported 3 minutes apart around the base of Mt St. Helens overnight, followed by several other smaller quakes. The US Geological Survey and the Pacific Northwest Seismic Network recorded a 3.9 magnitude earthquake at 12:36 am this morning, followed by a 2.7 magnitude. Over 130 people reported feeling the first quake early Wednesday morning.
They recorded 7 other quakes in the area since 12:40 am Wednesday morning that were smaller than a 2.0 magnitude. All of the seismic activity this morning has been at about 10 kilometers below the surface.
From December 2016 to mid-2017, swarms of deep earthquakes were detected around the volcano. The U.S. Geological Survey says that seismic swarms do not directly indicate that an eruption is imminent, because volcanic forecasting is difficult.
Mount St. Helens is the most historically active volcano in the Cascade range, having produced four major explosive eruptions since 1479, and dozens more smaller eruptions, including pyroclastic flows, lava flows and domes, and lahars. It is located approximately 80 km NE of Portland, OR.
Mount St. Helens is best known for its large explosive eruption, summit collapse and directed blast of May 18, 1980, which was the most expensive and deadly volcanic event in United States history. The volcano continued erupting during 1980-1986, producing a lava dome within the 1980 crater. Mount St. Helens again erupted in 2004-2008, when it produced only minor explosive activity but a series of spectacular lava spines with a cumulative volume of almost 100 million cubic meters that doubled the size of the lava dome. Tremors and millions of small earthquakes accompanied both of the recent eruptions. Since early 2008 no eruptions have taken place and the lava dome has shrunk in height as its steep sides crumble into a broader, more symetrical shape.