Multiple small earthquakes beneath the surface of Mount St. Helens the past two months suggest it may be recharging magma.
These tiny quakes which started March 14 have been happening at a depth of two and seven kilometers — or 1.2 to four miles beneath the surface. Over the last eight weeks, there have been over 130 earthquakes formally located by the Pacific Northwest Seismic Network and many more too small to be located, says USGS.
The small earthquakes beneath the surface may suggest Mount St. Helens is recharging magma. The magma chamber is likely imparting its own stresses on the crust around and above it as the system slowly recharges. The pressure drives fluids through cracks, producing the small quakes, per USGS.
Right now, the earthquake swarm at Mt. Hood is centered just to the south of the main edifice (see below) and most of the earthquakes are between 3 and 5 kilometers below the surface. This is likely the zone where magma is being staged as it ascends from its source.
Mt. Rainier has been dubbed a “time bomb“, “the most dangerous mountain in the United States” and “one of the most dangerous volcanoes in the world” because it sits so close to Seattle, Tacoma and other major cities along the coast of Washington state. In the event of a full-blown eruption, countless numbers of people would literally be buried alive in a tsunami of super-heated mud. These tsunamis of super-heated mud are known as “lahars”, and scientists believe that Mt. Rainier is capable of producing lahars that could move at speeds of up to 50 miles per hour. I am so convinced that an eruption of Mt. Rainier is in our future that I even put one in my novel.
If Mt. Rainier were to erupt as powerfully as Mount St. Helens did in its May 18, 1980, eruption, the effect would be cumulatively greater, because of the far more massive amounts of glacial ice locked on the volcano compared to Mount St. Helens and the vastly more heavily populated areas surrounding Rainier. Lahars from Rainier pose the most risk to life and property, as many communities lie atop older lahar deposits. According to the United States Geological Survey (USGS), about 150,000 people live on top of old lahar deposits of Rainier. Not only is there much ice atop the volcano, the volcano is also slowly being weakened by hydrothermal activity. According to Geoff Clayton, a geologist with a Washington State Geology firm, RH2 Engineering, a repeat of the Osceola mudflow would destroy Enumclaw, Orting, Kent, Auburn, Puyallup, Sumner and all of Renton. Such a mudflow might also reach down the Duwamish estuary and destroy parts of downtown Seattle, and cause tsunamis in Puget Sound and Lake Washington. Rainier is also capable of producing pyroclastic flows and expelling lava.