HELENA, Mont., Dec. 30 (UPI) -- An "energetic earthquake swarm" of minor temblors shook Yellowstone National Park in Wyoming, Montana and Idaho for several days, officials said.
The park, which lies over a huge volcanic caldera, experienced around 40 quakes, the Helena, Mont., Independent Record reported. The largest measured 3.8 on the Richter scale -- a quake strong enough to be felt by people in the area but one that rarely causes damage.
The caldera is sometimes referred to as the Yellowstone 'super volcano.'
Clusters of temblors are common in the area, but they also raise anxieties about an eruption of the super volcano. The caldera measures 34 miles by 45 miles.
"It's an energetic earthquake swarm," said Mike Stickney of the Montana Bureau of Mines and Geology. "I'm hearing reports that people in the park have been feeling
some of them."
Stickney said there have been two other swarms this fall that had fewer quakes and tended to be of lesser magnitude. He said that the cluster is most likely a "tectonic adjustment" with no aftereffects.
Yellowstone last erupted about 640,000 years ago. An eruption, which Stickney described as a "remote possibility," could be severe enough to change the global climate as well as blanketing much of the west with lava and ash, he said.