St. Helens quakes move under the caldera

The Daily News Online, which serves the lower Columbia River region in the south of Washington State, reports on the recent St. Helens volcano earthquake swarm of this past week, and concludes:

The quakes are occurring along a fault known as the Mount St. Helens Seismic Zone, which stretches from an area immediately northwest of the mountain and into Lewis County. Seismologists continue to say the quakes are caused by relief of stresses in the earth’s crust and are not a signal that the volcano is getting ready for another eruption.

Well, in the past twenty-four hours, there have been two quakes of magnitude 2.0 or greater which have occured directly beneath the dormant volcano’s caldera. This is shown at the Pacific Northwest Seismic Network page:

Notice that the depths for the caldera quakes are only slightly more than a kilometer. The depths of the St. Helens quakes have been getting closer to the surface by about a kilometer a day.

Even if magma reaches the surface, it may not be such a big deal. In 2006, there was a 3.1 quake that resulted in a plume of ash and smoke that frankly I had forgotten about, and I doubt many people in the state recall it either. If you’re interested, read about that here.

Anyhow, we might be seeing another plume early this week, and I hope it’s of only scientific interest.

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About engineerzero

Once and future engineer.
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