What Do Lots of Little Earthquakes Mean?

Photo Credit: Jason Riedy on Flickr

When they are associated with a volcano, lots of little earthquakes may spell a coming eruption.  Called an “earthquake swarm” they happen regularly in volcanic regions but are always of interest to seismologists as they indicate possible movement of magma beneath the earth’s surface.  A recent swarm of earthquakes around Mount Rainier has seismologists in the region watching the mountain with increased interest.  A swarm of  174 earthquakes over the two days leading the the 1980 eruption of Mount St. Helens illustrated just how important monitoring such seismic activity could be.  Here’s hoping its just a little bit of grumbling on the part of Mount Rainier and nothing more.