10:07 AM PDT on Sunday, October 24, 2004

By kgw.com and AP Staff

MOUNT ST. HELENS, Wash. -- Rain and clouds Saturday again hampered efforts by the U.S. Geological Survey to monitor the restless Mount St. Helens volcano.

AP photo

Park ranger David Roth, of Vader, Wash., takes a wind speed reading opposite the crater of Mount St. Helens.

Due largely to low clouds, a remote-control monitoring plane has not been an immediate help to scientists, but it shows promise. Poor viewing conditions with rain were forecast throughout the weekend.

Lava continued to ooze into the volcano's crater and the new lava dome remains substantial, scientists said Friday.

After getting a good look into the crater about 48 hours ago, geologists described it as about 900 feet long, 250 feet wide and 230 feet high.

"That sucker is huge," said Jeff Wynn, chief scientist for volcano hazards at the Cascades Volcano Observatory in Vancouver. It's still growing, he said, and glows red-hot at night.

Seismic activity is diminishing and "does not seem to correlate with how much material is coming out," Wynn said. Earthquakes have decreased, with two or three magnitude 1 quakes every few minutes.

Earthquakes at the volcano are at or below magnitude 1 and occurring at a rate of two or three per minute, the University of Washington seismology lab said Friday.

USGS scientists managed to collect some rock samples from the new lava lobe at mid-week, using a bucket dangled from a helicopter on a 100-foot line.

"No one is allowed to walk in there," Wynn said. Trails within a five-mile radius remain closed, as does the Johnston Ridge Observatory, 5 miles north of the 8,364-foot mountain.

Scientists with Advanced Ceramics Research have been hoping to use one of their 22-pound, remote-controlled drone airplanes that might be used to collect gas samples and other data from the volcano. However, cloud cover Friday prevented a launch under Federal Aviation Administration rules.

Fifty-seven people were killed by the volcano's massive May 18, 1980 blast.

Like the old lava dome, formed in the six years after that devastating eruption, the new lobe is made of a type of volcanic rock called dacite, Wynn said. More than 63 percent silica, it tends to be sticky and viscous - and "more likely to trap gases and reach an explosive point."

Other types of lava, with less silica, typically flow more easily and are less explosive, he said.

The volcano rumbled back to life Sept. 23, with shuddering seismic activity that peaked above magnitude 3 as hot magma broke through rock. Molten rock first reached the surface on Oct. 11, marking the resumption of dome-building activity that had stopped in 1986.

The low earthquake and gas-emission rates indicate the lava has little gas, which scientists said reduces the probability of highly explosive eruptions.

Nonetheless, they warn a more explosive eruption, possibly dropping ash within a 10-mile radius of the crater, is still possible at any time.