The last time I reported on the Cascade Volcanic Arc, I was focused on Mt. Adams. This slumbering volcano had experienced an unusual round of seismic activity that lasted into the beginning of this year.
Subsequently, two of the area’s Congressional representatives sent a letter to the United States Geological Survey (USGS) requesting additional studies of the region. Additionally, emergency plans for the Pacific Northwest were being reviewed and updated.
These moves may prove to be most timely. Swarms of hundreds of small earthquakes have just been recorded around the Cascade Range’s iconic Mt. Rainier.
Mount Rainier was experiencing “the most significant seismic activity” at the volcano in more than 15 years as an “earthquake swarm” hit the site starting on Tuesday, according to the U.S. Geological Survey’s Cascades Volcano Observatory.The swarm — hundreds of small earthquakes hitting the same area in quick succession — started around 1:30 a.m. local time Tuesday and was continuing into Wednesday, data showed.But there was no cause for concern, according to the Cascades Volcano Observatory, which monitors volcanoes across Washington, Oregon and Idaho. Some of the earthquakes were too small to even locate.”Earthquakes are too small to be felt at the surface and will likely continue for several days,” the observatory said in a news release Tuesday. “There would be no damage caused by such small events.”
At the present time, Cascades Volcanic Observatory indicates there is no evidence suggesting that the swarm is heralding a potential eruption. The seismic activity appears to be related to the movement of heated water under the volcano’s surface.
According to CVO, there is no indication of magmatic movement or surface deformation. No changes have been observed in infrasound signals or volcanic gas emissions. As a result, the Volcano Alert Level remains at Green (Normal), and the Aviation Color Code is also Green.Hydrothermal activity, rather than magmatic intrusion, is believed to be the primary driver of the swarm. Such swarms occur once or twice annually beneath Mount Rainier.
The nature of this seismic activity, therefore, is similar to that which occurred during a 2009 swarm.
“The last large swarm at Mount Rainier in 2009 had a maximum magnitude of M2.3 and lasted three days. The 2009 swarm had over 1,000 earthquakes, of which the PNSN officially located 120 earthquakes,” the USGS said. “Past swarms have been attributed to circulation of fluids interacting with preexisting faults.”
There is even more good news. Mt. Adams and its more infamous partner, Mt. St. Helens, are also quiet at the present time.
All volcanoes in the Cascade Range of Washington and Oregon are at normal background activity levels. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State and Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake in Oregon.
For those of you who might be interested, the Cascade Mountain Range formed by the oceanic plate (the Juan de Fuca Plate) sliding beneath the lighter continental plate (North American Plate). The geologic stresses occurring in the region are enormous, and it is far more likely to pose a significant regional problem for the country (sooner) than the Yellowstone Supervolcano.
But, for now, all is quiet along the West Coast — at least in terms of geology.
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