Earthquake swarm beneath Mount St. Helens June 2019

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Earthquake swarm beneath Mount St. Helens June 2019

Over the past month, more than 70 small earthquakes occurred beneath Mount St. Helens, the largest of which was a Magnitude 1.4 on June 30, 2019. Ranging in depths from 1 to 5 miles (2 to 8 km) below sea level, the earthquakes are too small to be felt at the surface.

The current pattern of seismicity is similar to swarms detected at Mount St. Helens in March 2019, May 2017, November-December 2016, March-May 2016, and in 2014. The activity is likely the result of small-scale underground movements of hydrothermal fluids or gas — a sign that Mount St. Helens remains an active volcano.

There is no detectable surface deformation or volcanic gas signal associated with this swarm. While the swarm represents a temporary uptick in activity, Mount St. Helens remains at normal, background levels of activity.

For more information, see the Activity Updates for Volcanoes in CVO Area of Responsibility and Earthquake Monitoring at Mount St. Helens.