A giant plume of steam shot up into the sky above Mt. St. Helens this afternoon in what has been the most dramatic sign yet of the recent increase in volcanic activity on the mountain.
Scientists said the column of steam and some ash rose about 15,000 feet high and was drifting southwest in the direction of Vancouver, Wash. and Portland. However, the steam cloud posed little threat to residents and was expected to result at most in a light dusting of ash, officials said.
Television cameras captured images of the white and gray plume that erupted about noon and rose into clear blue skies. Most of the cloud had dissipated within an hour.
Earlier in the day, scientists said that they were examining images of cracks on the glacier inside the volcano crater to determine if it was connected to existing activity.
Officials on Thursday said there was a 70% chance that Mt. St. Helens, which erupted in a huge and deadly explosion 24 years ago, could experience a small to moderate eruption.
Times staff writer Jesus Sanchez in Los Angeles contributed to this report.