Earthquakes -- small ones but lots of them. From Bloomberg:
Yellowstone National Park Hit by Hundreds of Small Earthquakes
Hundreds of small earthquakes have struck Yellowstone National Park in the western U.S. during the past four days, the most intense series of tremors in the area in some years, the University of Utah reported.
Earthquakes are common in Yellowstone, which averages 1,000 to 2,000 tremors a year, and its 10,000 geysers and hot springs are the result of geologic activity, the university said in a statement on its Web site. The park covers sections of Wyoming, Idaho and Montana.
The university's network of 28 seismographs in the area started picking up the tremors on Dec. 26, and more than 250 quakes have been recorded since then -- including nine greater than magnitude 3.0 and about 24 between magnitude 2.0 and 3.0. Some visitors have reported feeling the quakes.
Seismologists are trying to determine if the tremors are being caused by fault movements, the university said. The biggest quake was a magnitude 3.9 recorded at 10:15 p.m. local time on Dec. 27, when the largest number of tremors of magnitude 3.0 or more was recorded.
The park maintains two websites for Earthquakes and Volcanos
The University of Utah also monitors Earthquakes and Volcanos
There is a lot of careful observation going on as Yellowstone was once a huge volcano and if it decides to go again, it has the potential to take out a large area of land.
