Berkeley blog - Mount St. Helens and earthquakes

Flying back from Germany a week ago Saturday, our plane was diverted over Iceland to get north of the ash cloud blowing from the Eyjafjallajökull volcano towards Spain. This caused a delay of two hours, not bad compared to what others have experienced, and I got to see the ash cloud from the south-facing windows. First time I have ever seen an erupting volcano. Pretty cool, even though it was a volcanic eruption. The dark cloud was nearly vertical, before it topped out, and then headed off towards Spain.

Anyway, it is now thirty years since the last large volcanic eruption in the conterminous United States at Mount St. Helens. The Berkeley Seismo Blog has a nice description of the harmonic tremors that reflected the magma moving within the volcano, and then the 5.1 magnitude earthquake that triggered slope failure of the mountain and the explosive volcanism.

Small earthquakes continue to occur. Check out the graphics and info at the Pacific Northwest Seismic Network.