Mount St. Helens erupts after 18 years
Mount St. Helens in Washington releases a plume of ash during an eruption on March 8, 2005.
Small earthquakes resumed within hours of the blast, suggesting pressure inside the mountain was rebuilding.
Scientists say there could be more steam eruptions soon.
Scientists had been predicting just such an eruption for days because of thousands of earthquakes and signs that the rock inside the crater was expanding rapidly.
Few people live near the mountain, about 100 miles south of Seattle. The closest structure is the Johnston Ridge Observatory, about five miles from the crater.
USGS seismologist Bob Norris says magma could be moving underground and he would not be surprised to see more explosions in the next days or weeks.