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New Quake at Mt. St. Helens Sends Steam, Ash 15,000 Feet High
logical Survey spokesman Jim Vallance said the quake was probably caused by a large rockfall from the lava dome inside the crater. Most likely some hot rock mixed with snow causing the steam. The small amount of ash in the plume was probably kicked up by the rock fall, he said.
A similar event on May 29th melted some snow and ice in the crater and also sent up a plume to about the same altitude, he said.
Seismic activity at the mountain has now returned to normal.