Saturday, September 16, 2006

Current Mount St.Helens' eruption has been lasting two years!

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.

Mount St. Helens.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.In the past few months there have been more rockfalls and ash plumes from within the crater, but Moran said that's because the material inside the dome is larger and steeper and thus more vulnerable to gravity.The 2004 earthquakes started "out of the blue" and the USGS has proposed placing more monitoring equipment on several volcanos in the region to address that.

Part of the reasoning is that the current eruption has illustrated how quickly dormant volcanoes can "wake up" in just a day or two. If that happens, there isn't enough time to safely transfer more equipment to a suddenly active mountain and scientists are left with whatever equipment is already in place, Moran said.

In addition, scientists want to see if more sensitive equipment might reveal that there are earlier, subtle warning signs before the earthquakes start.For now, though, it's business as usual as scientists continue to chart the volcano's every move."In general, there haven't been any significant changes in the eruption over the last year plus," Moran said.

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