Volcanic rock has flowed to the surface of Mount St. Helens' crater, creating a new lava dome after weeks of seismic activity, a geologist 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. The bulge is now considered a new lava dome, the scientists said.
"Now that we have new lava at the surface, we're comfortable saying that dome-building has resumed at the volcano,” U.S. Geological Survey geologist Tina Neal said.
The bulge had risen at least 330 feet since scientists noticed it Sept. 30.
Geologists said there is still a chance of explosive ash eruptions from the 8,364-foot mountain, and the immediate area around the volcano remained closed.
The mountain 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 horizontally as in the devastating blast that left 57 people dead, leveled trees for miles around, and covered much of the Pacific Northwest with ash.
The mountain in the Cascade Range rumbled back to life Sept. 23, beginning with thousands of tiny earthquakes. For five days earlier this month, it spewed clouds of steam mixed with small amounts of old volcanic ash.
Earlier Tuesday, more steam rose from the crater as geologists kept up their close watch on the volcano.