Lava has been climbing to the surface at nearly 1,300 degrees for the past few days in a process that scientists said Wednesday could go on for days, weeks or months. At night, low-hanging clouds and the steam rising from the volcano reflect the glow of the red-hot stone inside the crater.
Scientists said they do not know how long the eruption might continue, or whether it will be marked by explosive blasts. But they said any eruption would probably be far less dangerous than the cataclysmic explosion in 1980 that blasted away much of the mountaintop and killed 57 people.
Meanwhile, a British volcano expert suggests that monitoring the gases emitted by lava from might provide clues to future eruptions.
The isotope content of these gases might indicate whether the next eruption will be a catastrophic blast, as occurred in 1980, according to a paper by Jon Blundy of Bristol University, published in Thursday's issue of the journal Science.
Blundy and doctoral student Kim Berlo studied the gases from magma in the mountain's 1980 eruption and concluded there were two lava reservoirs.
One, located a little more than four miles deep had been shedding gas for five years before that explosive eruption, they said, and a second short-lived reservoir was located nearly two-and-a-half miles deep.
Blundy reported that the magma which erupted in May 1980 came from both the deep and shallow reservoirs. Later, more gentle eruptions, came exclusively from magma trapped at shallow levels.
"We have shown there is a link between the storage depth of magma and the explosiveness of an eruption," Blundy said in a statement.
"This suggests that monitoring the abundance of short-lived radioactive isotopes above restless volcanoes could be a useful tool for predicting the style of the next eruption. It might also provide clues as to when the next eruption will occur," he reported.
The molten rock, or magma, rising inside the mountain has been depositing itself on the crater floor inside the volcano, halfway up the 8,634-foot peak, creating a "fin" of rock estimated Tuesday at 60 to 90 feet tall and 150 to 180 feet wide.
Scientists calculate its growth rate at about 2 to 3 cubic meters a second, said Jeff Wynn, chief scientist for volcano hazards. That's enough new rock to fill an Olympic-size swimming pool in about 15 minutes.
"'Til you're actually down on it you can't imagine how huge it is," Wynn said.
The fin, at about 750 degrees, has a pinkish cast "like medium roast beef," geologist Tina Neal of the U.S. Geological Survey said.
The glowing rock itself can be seen only from above, from aircraft.
Lava first reached the surface Monday, following 2½ weeks of rumblings and steam and ash bursts from the mountain.