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 The tremor, a relatively light event by seismic standards, struck
the northwest corner of the park and capped a flurry of smaller
quakes at Yellowstone since Thursday, geologists at the University
of Utah Seismograph Stations said in a statement.
The latest earthquake struck at 6:34 a.m. near the Norris Geyser
Basin and was felt about 23 miles away in two small Montana towns
adjacent to year-around entrances to the park — Gardiner and West
Yellowstone.
The national park spans 3,472 square miles (8,992 square km) of
Wyoming, Montana and Idaho, and draws about 3 million visitors each
year to its iconic geysers and wildlife attractions, including
bison.
A U.S. Geological Survey team planned to tour the Norris Geyser
Basin on Sunday to determine if the quake altered any of
Yellowstone's geothermal features, such as geysers, mud pots and hot
springs.
Several people reported having felt shaking they compared to the
rumble of a tractor-trailer truck driving by, and a few items fell
off the shelves at a local grocery store, a West Yellowstone police
dispatcher said.
About 1,000 to 3,000 earthquakes strike Yellowstone each year,
according to the Yellowstone Volcano Observatory, a research
partnership of the park, the University of Utah and the U.S.
Geological Survey.
The ancient super-volcano, or caldera, that lies beneath the surface
of the park was discovered by scientists in recent years to be 2.5
times larger than previously thought, measured at 30 miles wide,
according to the park.
Sunday's quake occurred near the center of an area of ground uplift
that geologists have been tracking for several months, University of
Utah seismologists said. Elevated seismic activity was also found in
the area during a previous period of uplift from 1996 to 2003.
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The recent spike in earthquake activity at Yellowstone is linked to
the uplift, which in turn is caused by the upward movement of molten
rock beneath the Earth's crust, according to the U.S. Geological
Survey.
Fortunately, there was no indication that the recent seismic
activity signaled an impending eruption of the Yellowstone Caldera,
scientists said.
Researchers with the observatory have said in the past that
catastrophic eruptions by the super-volcano are unlikely for tens of
thousands of years, though less extreme lava releases could occur
within thousands of years.
The super-volcano's most cataclysmic eruption occurred 2 million
years ago, covering half of North America with ash and killing
prehistoric animals as far as away as modern-day Nebraska, according
to the Yellowstone Volcano Observatory.
Heat from a vast chamber of molten rock beneath the caldera fuels
the park's famous geothermal features, including Old Faithful
Geyser, Yellowstone scientists say.
(Reporting by Laura Zuckerman; editing by Steve Gorman and Sandra Maler)
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