Lava breaks surface at Mount St. Helens

MOUNT ST. HELENS, Wash. — A new lava dome is growing on Mount St. Helens, with volcanic rock reaching the surface of the crater after weeks of seismic activity, scientists said Tuesday.

Scientists had known for days that magma or molten rock was nearing the surface, as a bulge grew on the south side of the existing 1,000-foot lava dome and the increasingly hot rock gave off steam as it met water and ice in the crater. That bulge is now considered a new dome.

"Now that we have new lava at the surface, we're comfortable saying" that dome-building has resumed at the volcano, said U.S. Geological Survey geologist Tina Neal.

The dome building could continue for weeks, months or even years, she said. After the mountain's deadly 1980 blast, lava eruptions built the existing dome periodically for six years.

Seismic activity has dwindled to small quakes, about magnitude 1, every five to 10 minutes, Neal said. That suggests smooth, steady magma flow to the new dome, she said.

The extrusion of new rock measured about 60 by 120 feet, she said.

Scientists saw jets of dark steam and ash at the site, which rose about 30 feet and then fell back into the crater in the form of hot rock and ash, Neal said.

Geologists said there is still a chance of explosive ash eruptions from the 8,364-foot mountain, and that the immediate area around the volcano remained closed. Neal said winds Tuesday were from the northwest, and would direct any ash released by the dome-building activity to the southeast, which is sparsely populated.

Glacier and snow melt in the crater could create small lahars, or mud flows, said USGS hydrologist Jon Major. But the flows likely would stop at a sediment retention dam several miles west of the mountain in the valley formed by the North Fork of the Toutle River.

The volcano exploded on May 18, 1980, with a massive landslide as the top of the mountain collapsed. Any new ash eruption, scientists say, would likely be much smaller and would shoot vertically, instead of the devastating horizontal blast in 1980 that left 57 people dead, leveled trees for miles around and covered much of the Pacific Northwest with ash.

For the past week and a half, the restless mountain has sent steam, sometimes mixed with ash, venting from the bulge on the lava dome that has risen at least 330 feet since scientists noticed it Sept. 30.