Mount St. Helens has experienced approximately 350 earthquakes since Feb. 1, according to a report published Tuesday by the U.S. Geological Survey.
Cascades Volcano Observatory conducted the latest measurements of seismic activity for the Washington state volcano noting that over 95% of the recorded earthquakes have been less than magnitude 1.0 and would be too small to be felt on the surface, with the largest being a magnitude 2.0 on May 31.
The earthquakes reached a peak of 38 in a single week during the first seven days of June. The surveyors say the past two periods of heightened seismic activity from 2023 to the present "represent the largest short-term increase in earthquake rates since the last eruption ended in 2008."
According to a post on X from USGC Volcanoes, the recent activity could be interpreted as the arrival of additional magma, a process known as "recharge."
"Small magnitude earthquakes located beneath Mount St. Helens at depths well below sea level are generally thought to be associated with pressurization of the magma transport system. One cause for this pressurization is the arrival of additional magma, a process called recharge," the report stated.
The Cascades Volcano Observatory went on to explain: "Magma slowly rises through the lower crust and accumulates in a reservoir about 2.5 to 6 miles ... below sea level. Recharge events can occur when magma enters this upper reservoir and increases stresses that lead to earthquakes."
Mount St. Helens is most famously known for its explosive eruption on May 18, 1980, which claimed 57 lives, caused over $1 billion in damage, and leveled 230 square miles of forest.
Authorities say Mount St. Helens remains at normal, background levels of activity and there is no change in alert levels.
James Morley III ✉
James Morley III is a writer with more than two decades of experience in entertainment, travel, technology, and science and nature.
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