03:48 PM PDT on Thursday, October 21, 2004

By kgw.com and AP Staff

MOUNT ST. HELENS, Wash. -- The new lobe on the lava dome at Mount St. Helens has grown to about the size of an aircraft carrier, scientists said Thursday afternoon.

AP photo

The area behind the lava dome in the Mount St. Helens crater continues to grow as steam bellows over the crater rim.

After getting a good look in the crater of the volcano in Wednesday's clear weather, the U.S. Geological Survey said the new extrusion is about 900 feet long, 250 feet wide and 230 feet high. In addition to the lava dome's increase in width since last week, geologists said a "fin" shaped rock has collapsed.

“The crews of course gave us their rough estimate based on flying around and taking pictures and I think they feel it’s not doubled in size but something to perhaps another 25 percent and 30 percent,” said USGS geologist Tina Neal.

A helicopter hauling a bucket on a 100-foot line was able to scrape up fresh rock and ash samples, which turned out to be typical Mount St. Helens lava. The USGS planned to further analyze the samples for more information about the magma that is rising to the surface.

By analyzing the new rock in a lab, scientists said they can get a better idea of whether the lava coming up is left over from the eruptions that ended in 1986 or from new magma making its way to the surface, which could prove to be much more explosive.

Scientists said earthquake activity indicates magma is still pushing into the volcano where it continues to build the lava dome as it has for more than a week. In addition, a gas-sensing flight Wednesday detected low levels of the volcanic gases carbon dioxide, sulfur dioxide, and hydrogen sulfide, which is also consistent with magma continuing to rise.

The USGS believes this could go on for months, but it remains possible the volcano could have a more violent eruption at any time.

“Even though it seems like activity may be diminishing a little bit in intensity, because these earthquakes have diminished, we still consider there a possibility that there could be a sudden explosion,” said Neal.

If there were an ash plume currently, the National Weather Service projected it would drift to the southeast.

Scientists were also able Wednesday to test the remote controlled “Silver Fox,” an unmanned aircraft 5-feet long with an 8-foot wingspan developed for the military.

However, it was too cloudy Thursday for a flight. Researchers hope to use the plane to to provide visual images and collect additional gas samples, which could indicate the presence of new, more violent magma.

Some forest roads to reopen

Also Thursday, the U.S. Forest Service said sections of Forest Roads 81 and 83 on the south side of Mount St. Helens would be reopened on Friday.

The two roads between Kalama Horse Camp and Lava Canyon had been closed when a volcanic alert was issued earlier this month, which prompted the forest areas within a 5-mile radius of the volcano’s crater to be evacuated.

Although those two roads on the edge of the 5-mile radius will reopen, officials said the Johnston Ridge Observatory and other roads in the area would remain closed.

“We are confident forest visitors will respect closures north of the roads that remain closed for people’s health and safety,” said National Volcanic Monument Manager Cliff Ligons.