Hundreds of small earthquakes at Yellowstone National Park in recent weeks have been an unsettling reminder for some people that underneath the park's famous geysers and majestic scenery lurks one of the world's biggest volcanoes.
In the ancient past, the volcano has erupted 1,000 times more powerfully than the 1980 blast at Mount St. Helens, hurling ash as far away as Louisiana.
No eruption that big has occurred while modern humans have walked the earth, however, and geologists say even a minor lava flow is extremely unlikely any time soon.
Some observers are nonetheless warning of imminent catastrophe.
"To those of us who have been following these events, we know that something is brewing, especially considering that Yellowstone is over 40,000 years overdue for a major eruption," warned a posting on the online disaster forum Armageddononline.org.
Another Web site contained a page entitled "Yellowstone Warning" that encouraged "everyone to leave Yellowstone National Park for 100 miles around the volcano caldera because of the danger in poisonous gasses that can escape from the hundreds of recent earthquakes."
That site, which carried the U.S. Geological Survey logo, has since been taken down.
"A casual observer would be led to believe that was an official source," Yellowstone spokesman Al Nash said, pointing out that the Yellowstone Volcano Observatory, which monitors the park for seismic activity, hasn't changed the volcano's alert level from "normal."
Working with the Geological Survey, Nash issued a news release Thursday, saying no evacuation had been ordered.
Jessica Robertson, a Geological Survey spokeswoman in Reston, Va., said the Web page violated the USGS trademark and that the agency's attorneys were investigating whether a federal offense was committed.
Earthquakes are hardly unusual in Yellowstone. Hundreds occur in the park every year. Earthquake "swarms" like the recent activity also aren't uncommon, although the 900 or so quakes that began December 26, 2008 and significantly tapered off about a week later appear to have been the most energetic swarm in more than 20 years.
The most powerful temblor was magnitude 3.9, just short of being able to cause moderate damage. The vast majority of quakes were too weak to be felt by people.
Scientists knowledgeable about Yellowstone's geology aren't publicly speculating about what caused the swarm before they can analyze data.
That will take months.
"I could come up with 100 different theories without any evidence for them and they would all be equally likely," said Jake Lowenstern, the Menlo Park, Calif.-based scientist in charge of Yellowstone Volcano Observatory.
"Unless you have some reason to say that's what's going on, then you're not going to get a whole lot of people convinced by your speculation."
Park geologist Hank Heasler said the odds of a cataclysmic eruption at Yellowstone any time soon are astonishingly remote - about the same as a large meteorite hitting the Earth.
The last such eruption occurred 640,000 years ago.
The last eruption of any kind at Yellowstone was a much smaller lava flow about 70,000 years ago.
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OK, Yellowstone is going to 'explode' - it IS a volcano after all. However, the likelihood of it happening anytime soon is relative. Soon - has a whole different meaning geologically than it does to we humans. Yellowstone's last eruption could be viewed as but a moment ago geologically and that was 70,000 years ago to we humans.
I for one am not going to fret about an eruption in Yellowstone ... then again, I live a bit away from there.
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