After 18 years of relative quiescence, Mount St. Helens volcano recaptured the world’s attention when it showed signs of reawakening in September 2004. On September 23 a swarm of small (less than magnitude (M) 0), shallow (less than 1.5 miles below the surface) earthquakes began in and beneath the 1980-1986 lava dome. -- Major et.al., 2005 |