Mount St Helens, the volcano that blew its top with cataclysmic force in
1980, quietened down after spewing a plume of steam and ash - but only briefly.
Within hours of the eruption yesterday, seismic readings suggested pressure was building again inside the volcano, which had been dormant for 18 years.
It began rumbling last week, set off by small earthquakes occurring as often as three or four times a minute, and scientists said there could be more steam eruptions soon.
Yesterday's eruption, described by US government scientist Mr Jeff Wynn as a "throat-clearing," was the sleeping giant's first since 1986.
The ash appeared to pose no threat to anyone, but scientists warned that people living south-west of the mountain might notice a dusting on their cars. There was no sign of lava.
The earthquakes started September 23rd and grew steadily stronger, finally reaching a magnitude of 3.3 Thursday and yesterday. After the eruption, they stopped for several hours, said Mr Wynn, of the US Geological Survey.
Mr Tom Pierson, a US Geological Survey geologist, said officials will monitor the site "on a very intense scale until we can determine that the thing has really gone back to sleep."
Scientists had not been expecting anything like the mountain's devastating eruption in 1980, which coated much of the north-western United States with ash and obliterated the top 1,300 feet of the mountain. It now stands 8,364 feet.
Few people live near the mountain, the centrepiece of the Mount St. Helens National Volcanic Monument in the Gifford Pinchot National Forest, about 100 miles south of Seattle. The closest structure is the Johnston Ridge Observatory, about five miles from the crater.
On May 18th, 1980, Mount St. Helens blew its top with such force that 57 people lost their lives.
PA