What's Driving All The Shaking At Yellowstone National Park?
Since December 26 the park has been hit by more than 250 earthquakes that, while not overpowering, have been in the range of a 4.0 magnitude, according to the Yellowstone Volcano Observatory.
The largest of the earthquakes was a magnitude 3.9 (revised from magnitude 3.8) at 10:15 pm MST on Dec. 27. The sequence has included nine events of magnitude 3 to 3.9 and approximately 24 of magnitude 2 to 3 at the time of this release. A total of more than 250 events large enough to be located have occurred in this swarm. Reliable depths of the larger events are up to a few miles. Visitors and National Park Service employees in the Yellowstone Lake area reported feeling the largest of these earthquakes.
While Yellowstone experiences anywhere between 1,000 and 2,000 earthquakes of varying magnitudes each year, the recent swarm -- centered beneath Yellowstone Lake some 3 to 6 miles south-southeast of Fishing Bridge -- is impressive in that its been unleashed in a handful of days.
"This ... earthquake sequence is the most intense in this area for some years and is centered on the east side of the Yellowstone caldera," reports the observatory staff. "Scientists cannot identify any causative fault or other feature without further analysis. Seismologists continue to monitor and analyze the data and will issue new information if the situation warrants it."
Earth scientists aren't sure what to make out of this burst of activity. At the University of Utah, where Dr. Robert Smith teaches geophysics and also monitors Yellowstone's seismic activity, the professor says it's impossible to say at this point whether the swarm is a precursor to some larger volcanic event.
If you recall, it was just about four years ago that a made-for-TV docudrama about this geologic wonder created some serious buzz about whether Yellowstone, and anyone visiting within a few hundred miles, was going to be blown to smithereens at any moment.
Well, that was four years ago, and while Yellowstone's geologic plumbing has uttered some burps -- minor earthquakes are normal, the Norris Geyser Basin grew a bit hotter than normal in 2003, as did the Artist Paint Pots area did this past May, the caldera is pushing up at a somewhat faster-than-normal rate -- the park is still there.