Mountain's Growing Dome Surprises Scientists

When the earthquakes started rumbling Mount St. Helens on Sept. 23, 2004, seismologist Seth Moran never dreamed he'd still be recording them two years later.

U.S. Geological Survey scientists had charted earthquake swarms and even small eruptions since the volcano's 1980 massive eruption, but those lasted a matter of days or weeks. The current eruption has lasted nearly two years.

In the first two days of the earthquakes officials weren't even sure if this was an eruption, they just knew they were recording hundreds of earthquakes each day.

"Within two or three days we started thinking it was leading up to an eruption, but we certainly didn't have a sense that it would last for two years," Moran said. "Even if we'd had known this was going to be a lava dome-building eruption, I don't think anyone would have thought that it would have lasted this long."

But last it has.

Lava first reached the crater on Oct. 11, 2004, and hasn't stopped since.

In the past two years the volcano has thrust more than 100 million cubic yards of volcanic rock into the crater, eclipsing the 97 million cubic yards it took six years to squeeze out during the 1980s. From the crater floor of 6,279 feet, the latest dome has grown 1,300 feet -- taller than the Empire State Building.

The pace seems to have slowed in the past year, but when it comes to making predictions about the eruption all bets are off, Moran said.

"I think everyone here is tired of losing bets on it," joked Moran. "It could go on for awhile or it could stop in a month and I don't think it would surprise anyone."

And, even at the slower rate of 1 cubic meter a second, the volcano is still producing enough lava to completely fill Lake Sacajawea every five-and-a-half days.

Significantly different from the devastating 1980 eruption, the volcano now is emitting relatively low levels of gas, meaning this eruption is much less likely to be explosive, Moran said.