BELLINGHAM, WA – More than 400 earthquakes have been detected beneath Mount St. Helens in the past few months, though there are no signs of an imminent eruption.
Most of the quakes since mid-July were less than magnitude 1.0 and too small to be felt at the surface, according to the U.S. Geological Survey.
From late August to early September, scientists observed about 40 to 50 earthquakes a week, a number that has fallen to around 30 a week.
Since 2008, the volcano has averaged about 11 earthquakes per month.
Small magnitude earthquakes detected with sensitive equipment signal a volcano is recharging as magma flows through chambers and cracks deep underground.