The Deep Funk of Mount St. Helens's "Drumbeat"

"The current eruption of Washington State's Mount St. Helens, which began about two years ago, has been marked by a series of weak, shallow earthquakes, or "drumbeats," that occur every couple of minutes, a new study says.

The "slip/stick" motion of the rocky "plug" being pushed out of the volcano is causing those rhythmic quakes, according to scientists from the Cascades Volcano Observatory in Vancouver, Washington..."