Mt. St. Helens Rumbling. USGS: Magma Moving

Small earthquakes are shaking the dormant Mount St. Helens

Mount St. Helens — dormant since 2008 — seems to be rumbling. The U.S. Geological Survey says more than 130 small earthquakes have been detected under the volcano in the past eight weeks. . . .

“Tiny temblors are shaking Mount St. Helens, indicating that the magma beneath the volcano is on the move, the U.S. Geological Survey (USGS) reports. “

5 thoughts on “Mt. St. Helens Rumbling. USGS: Magma Moving

  1. “Small magnitude earthquake swarm continues at Mount St. Helens
    May 05, 2016
    Beginning March 14, 2016, a number of small magnitude earthquakes have occurred beneath Mount St. Helens, at a depth between 2 and 7 km (1.2 to 4 miles). Over the last 8 weeks, there have been over 130 earthquakes formally located by the Pacific Northwest Seismic Network and many more earthquakes too small to be located. The earthquakes have low magnitudes of 0.5 or less; the largest a magnitude 1.3. Earthquake rates have been steadily increasing since March, reaching nearly 40 located earthquakes per week. These earthquakes are too small to be felt at the surface.
    The earthquakes are volcano-tectonic in nature, indicative of a slip on a small fault. Such events are commonly seen in active hydrothermal and magmatic systems. The magma chamber is likely imparting its own stresses on the crust around and above it, as the system slowly recharges. The stress drives fluids through cracks, producing the small quakes. The current pattern of seismicity is similar to swarms seen at Mount St. Helens in 2013 and 2014; recharge swarms in the 1990s had much higher earthquake rates and energy release.
    No anomalous gases, increases in ground inflation or shallow seismicity have been detected with this swarm, and there are no signs of an imminent eruption. As was observed at Mount St. Helens between 1987-2004, recharge can continue for many years beneath a volcano without an eruption.” Pics ad more at link:

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