Earthquake Swarm Reported At Mt. St Helens

PUYALLUP, WA - The city just tested the lahar warning siren on Dec. 5, which is a good thing because there's volcanic activity nearby.

Mt. St Helens is experiencing an earthquake swarm. Over 120 small quakes were detected over the last few weeks, according the U.S. Geological Survey (USGS). The mountain is considered an active volcano, and the earthquake swarm indicates that pressure is changing in the area likely due to lava moving around.

Earthquake swarms were also detected earlier in 2016. But that doesn't mean the mountain is ready to blow again. The most recent swarm began on Nov. 21, and the USGS has not detected and gas discharges or changes in the ground, which would indicate an imminent eruption.

In their own words:

"The current pattern of seismicity is similar to swarms most recently seen at Mt. St Helens in March-May 2016, and in 2014 and 2013," according to the USGS' Cascades Volcano Observatory blog. "The magmatic system is likely imparting its own stresses on the crust around and above it as the system slowly recharges. The stresses drive fluids through cracks, producing the small quakes. Subtle evidence of recharge has been observed since 2008 and can continue for many years. It is a sign that Mount St. Helens remains an active volcano."

Image via Flickr user Cat Branchman