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18 Most Dangerous U.S. Volcanoes Include Erupting Alaska Peak

John Roach
for National Geographic News
January 20, 2006
 
Spewing ash and steam miles into the sky, Alaska's Augustine Island
volcano has been erupting this week (see photo)
and posing a threat to air traffic.

The newly vigorous mountain is just one of the 18 most dangerous U.S. volcanoes, according to a report presented by John Ewert at a meeting of the American Geophysical Union in San Francisco last month. Ewert is a Vancouver, Washington-based volcanologist with the U.S. Geological Survey.

The overview ranks the United States' 169 volcanoes according to their threat levels and assesses the monitoring activity at each. The study authors aim to guide efforts to improve monitoring of U.S. volcanoes.

Ewert and colleagues based the threat rankings on frequency of eruptions and risks posed to nearby populations, infrastructure, and air traffic, among other factors. The more dangerous the volcano, the thinking goes, the better the early-warning system it should have. (Test the threat: Build a virtual volcano.)

Eighteen U.S. volcanoes are designated "very high threat"—the report's highest threat level.

Most Dangerous U.S. Volcanoes, in Descending Order

1. Kìlauea, Hawaii
2. Mount St. Helens, Washington State
3. Mount Rainier, Washington State
4. Mount Hood, Oregon
5. Mount Shasta, California
6. South Sister, Oregon
7. Lassen Volcanic Center, California
8. Mauna Loa, Hawaii
9. Redoubt Volcano, Alaska
10. Crater Lake area, Oregon
11. Mount Baker, Washington State
12. Glacier Peak, Washington State
13. Makushin Volcano, Alaska
14. Akutan Island, Alaska
15. Mount Spurr, Alaska
16. Long Valley caldera, California
17. Newberry Crater, Oregon
18. Augustine Island, Alaska



Only three of the most dangerous U.S. volcanoes are sufficiently monitored, according to the report: Kìlauea in Hawaii, Mount St. Helens in Washington State, and the Long Valley caldera in California.

"We do need more monitoring," said Stanley Williams, a volcanologist at Arizona State University in Tempe. "There are few volcanoes that are really being studied at a very close level."

Williams, who was not involved with the USGS study, said better monitoring of volcanoes would allow scientists to more accurately forecast eruptions. It would also allow experts to collect detailed information on what causes volcanoes to stir. Such information would help volcanologists to better distinguish routine rumblings from signals of unrest.

"People who have hurricanes to study have it nice and easy," Williams said. "They know they have six months to test instruments, to make measurements and six months to work on the data and upgrade things, whereas when volcanoes are erupting is unknown."

Instead, volcanologists can only put their monitoring equipment in place and wait.

Such specialized gear includes a mix of instruments: volcano-specific seismometers to measure earthquakes, sensors to gauge gas emissions, and global positioning systems (GPS) to detect land deformations.

"Volcanology requires you to have a suite of technology and instruments you are using, because there is no single magic thing you can do. You have to look at it all together," Ewert, the USGS volcanologist said.

With the right mix of equipment and personnel in place at the right time, volcano scientists today have the ability to detect unusual activity and forecast an eruption, Ewert said. Now scientists hope to refine their ability to forecast the style and size of eruptions.

"We're pretty good at the when, but not so good at the what or how big," he said.

Alaskan Eruption

The currently erupting Augustine Volcano, ranked as the 18th most dangerous, is the best monitored volcano in Alaska, according to geologists. Even so, scientists would benefit if more modern instruments were on the volcano to send back data for real-time analysis.

Rising from Cook Inlet in Southeast Alaska, Augustine Volcano forms the bulk of remote, uninhabited Augustine Island.

The volcano frequently cycles through bouts of explosive ash-producing eruptions, which pose a risk to air traffic, Ewert said.

"In terms of ash hazard, there are no remote volcanoes," he said. "Somewhere between 20 [thousand] and 25 thousand people fly in air routes that cross Alaskan volcanoes every day."

Hot ash can get sucked into jet engines, where it can melt, coat turbine blades, and cause engines to stall, Ewert explained. Ash can also jam electronic circuitry and coat windshields, reducing pilots' visibility.

To date, no airplane has crashed due to ash, but there have been several close calls.

In 1989 a Boeing 747 flew through an ash plume from Redoubt Volcano in Alaska and lost power to all four engines. The plane glided for four minutes, dropping nearly 12,000 feet (3,700 meters). It recovered just a few thousand feet from the ground.

When the 4,134-foot (1,260-meter) Augustine Volcano began erupting on January 11, several airlines cancelled or rerouted flights.

Augustine's eruptions grew in intensity on January 13 and 14. After a lull on Sunday and Monday, the volcano erupted again on Tuesday, sending an ash plume 8.5 miles (14 kilometers) into the air—the tallest plume yet in this recent bout of activity.

Yesterday the Alaska Volcano Observatory cautioned in an advisory that "it is likely, but not certain, that more explosive eruptions will occur."

The observatory is a run by the USGS, the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys.

Catch Up

Using the existing equipment on Augustine, scientists were able to detect a level of significant unrest by mid-July. However, the equipment is not sophisticated enough for detailed studies of the mountain, Ewert says.

The scramble to get more advanced equipment in place on Augustine is exactly the sort of challenge the USGS would like to avoid in the future. It is particularly difficult, for example, to deploy new equipment on Augustine now, when daylight is scarce and snow and ice is especially thick.

"We are playing catch-up with Augustine at this point, and, in fact, it's the middle of winter and it's really hard work out there," Ewert said.

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