Mount St. Helens cranked up the drama in its six-month-long eruption, sending a plume of ash 30,000 feet into the air beginning today at 5:25 p.m.

Clearly visible from Portland, the ash cloud was as big or bigger than any since the volcano rumbled back to life in late September.

The explosion seems similar to one that occurred on Jan. 16, but which was hidden by a heavy cloud layer, said University of Washington seismologist Steve Malone.

The event was preceded by a subtle shift in the pattern of small earthquakes that has been rattling the volcano for the past several months, Malone said. Soon after the plume was unleashed, the volcano became relatively quiet again.

"It looks like it's gone back to roughly the same type of signature we were seeing before," Malone said.