A Spurt of Quake Activity Raises Fears in Yellowstone
By Pat Dawson / Billings Thursday, Jan. 01, 2009
The Firehole River in Yellowstone National Park flows past other geysers, including Old Faithful, part of the Yellowstone Caldera
We who live along Montana's Yellowstone River are downstream from a simmering caldera, a geologic hot spot that has become especially active recently. Indeed, Yellowstone National Park contains the floor of a gigantic volcanic cauldron, one that rises and sinks with the forces that lie beneath — hence the picturesque geysers and steam holes. But a wave of recent earthquake activity is raising fears that have their origins 642,000 years ago, when a Yellowstone "supervolcano" exploded so violently that it created the caldera itself. Today, such an explosion — 1,000 times more powerful than the explosion of Mount St. Helens in 1980 — would not only cover most of the U.S. with ash but also throw so much dust into the atmosphere that the world's climate could change.
Last week, geologists at the Yellowstone Volcano Observatory (YVO) announced they had recorded a "notable swarm of earthquakes under way since Dec. 26 beneath Yellowstone Lake." The strongest tremor among the hundreds in the past week measured 3.9 on Dec. 27; most of the readings above 2.8 were felt by park employees and visitors around the lake area. The activity relaxed in magnitude early this week but then flexed upward again to top 3.0 by early New Year's Eve. "This December 2008 earthquake sequence is the most intense in this area for some years," YVO reported, "and is centered on the east side of the Yellowstone Caldera," the ancient collapsed volcano beneath Yellowstone Lake. The scientists said they cannot immediately "identify any causative fault or other feature without further analysis." (See a gallery of recent volcanic eruptions.)
more:
http://www.time.com/time/nation/article/0,8599,1869089,00.html