More info on eruption:
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Mount St. Helens eruption
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From: Curtis R Manley

Mount St. Helens erupted at 12:03pm PDT. The activity continued for about
24 minutes, creating a steam and dust plume that reached about 10,000 feet
elevation and drifted SSW toward Portland, OR and the Pacific coast.

Steam vented from a location at the southern edge of the dome where the
dome edge is covered by glacial ice and debris from the southern crater
wall. On Thursday afternoon N-S linear cracks were observed in the glacier
ice there, implying a slight uplift beneath the ice. Video images of the
eruption showed steam, some possibly superheated, venting from a limited
area and carrying blocks and fines upward into a mostly-white steam plume.
A USGS helicopter flight at the time of the eruption detected no thermal
anomaly with a thermal IR device, implying that this was a steam explosion
only, without magma being directly involved. Live video images taken by
helicopter at roughly 2:00pm PDT show a large hole in the glacial ice at
the edge of the dome, with a layer of gray ash and ejected blocks extending
from it over the ice only toward the SW.

The ongoing seismic activity decreased substantially during the eruption,
but then has rebounded at least slightly since the eruption ceased.

There have been no reported mudflows, but a possibility of slightly
increased flow of water out of the crater.

A USGS team was installing a seismometer on the NW flank of the volcano at
the time, but they were not affected by the event and were not in the path
of the plume.

Presumably an update will soon be posted at:
http://vulcan.wr.usgs.gov/Volcanoes/Cascades/CurrentActivity/

• Current Cascades Activity