From The Associated Press...

Updated: 01:05 PM EDT
Yellowstone Listed as High Eruption Threat

YELLOWSTONE NATIONAL PARK, Wyo. (May 9) - The Yellowstone caldera has
been classified a high threat for volcanic eruption, according to a
report from the U.S. Geological Survey.

AP
The U.S. Geological Survey says Yellowstone is the 21st most

of the 169 volcano centers in the United States.

Yellowstone ranks 21st most dangerous of the 169 volcano centers in

United States, according to the Geological Survey's first-ever
comprehensive review of the nation's volcanoes.

Kilauea in Hawaii received the highest overall threat score followed

Mount St. Helens and Mount Rainer in Washington, Mount Hood in Oregon
and Mount Shasta in California.

Kilauea has been erupting since 1983. Mount St. Helens, which erupted
catastrophically in 1980, began venting again in 2004.

Those volcanoes fall within the very high threat group, which

18 systems. Yellowstone is classified with 36 others as high threat.

Recurring earthquake swarms, swelling and falling ground, and changes
in hydrothermal features are cited in the report as evidence of

at Yellowstone.

The report calls for better monitoring of the 55 volcanoes in the

high and high threat categories to track seismic activity, ground
bulging, gas emissions and hydrologic changes.

University of Utah geology professor Robert Smith, who monitors
earthquakes and volcanic activity in Yellowstone, said more real-time
monitoring should be helpful.

''We've really been stressing over the last couple of years that the
USGS should consider hazards as a very high priority in their

he said. ''We need to get the public's confidence and the perception
that we're doing it right.''

The university has joined the Geological Survey and Yellowstone
National Park in creating the Yellowstone Volcano Observatory, which
uses ground-based instruments throughout the region and satellite

to monitor volcanic and earthquake unrest in the world's first

park.

The USGS report recognizes Yellowstone as an unusual hazard because

the millions of people who visit the park and walk amid features
created by North America's largest volcanic system, Smith said, a
status he has been advocating for years.

Smith does not paint the devastating picture portrayed in a recent TV
docudrama but said smaller threats exist. For example, a lower-scale
hydrothermal blast could scald tourists strolling along boardwalks.

Emissions of toxic gases from the park's geothermal features also

a threat. Five bison dropped dead last year after inhaling poisonous
gases trapped near the ground due to cold, calm weather near Norris
Geyser Basin.

Stepped up monitoring and a new 24-hour watch office could lead to

timely warnings and help avoid human catastrophes at Yellowstone and
nationally, according to the USGS.

Forty-five eruptions, including 15 cases of notable volcanic unrest,
have been documented at 33 volcanoes in the U.S. since 1980,

to the report, released April 29.