Most threatening U.S. volcanoes
WASHINGTON — Government scientists have classified 18 U.S. volcanoes as “very high threat” because of what’s been happening inside them and how close they are to people.
The U.S. Geological Survey has updated its volcano threat assessments for the first time since 2005.
The danger list is topped by Hawaii’s Kilauea, which has been erupting this year. The others in the top five are Mount St. Helens and Mount Rainier in Washington state, Alaska’s Redoubt Volcano and California’s Mount Shasta.
“This report may come as a surprise to many, but not to volcanologists,” said Concord University volcano expert Janine Krippner. “The USA is one of the most active countries in the world when it comes to volcanic activity,” she said, noting there have been 120 eruptions in U.S. volcanoes since 1980.
Kilauea is the most active volcano in the country “and it’s got a lot of development right on its flanks,” said government volcanologist John Ewert, the report’s chief author.
He said Hilo, Hawaii, is probably the biggest city in a hazard area for a very high threat volcano, Mauna Loa.
Ewert said the threat rankings aren’t about what will blow next, but “the potential severity” of the damage.
Eleven of the 18 very high threat volcanoes are in Oregon, Washington and California.
Of the highest threat volcanoes, Washington’s Mount Rainier “has the highest number of people in the downstream hazard zone,” about 300,000 people, said USGS geologist Angie Diefenbach, a report co-author.
Flagstaff, Ariz., is on the border of the large San Francisco Volcanic Field, which is in the moderate threat level, Ewert said.
Government scientists use two dozen factors to compute an overall threat score for each of the 161 young active volcanoes in the nation. The score is based on the type of volcano, how explosive it can be, how recently it has been active, how frequently it erupts, if there has been seismic activity, how many people live nearby, if evacuations have happened in the past and if eruptions disrupt air traffic.
They are then sorted into five threat levels, ranging from very low to very high.
Denison University volcanologist Erik Klemetti said the United States is “sorely deficient in monitoring” for many of the socalled Big 18.
Because of past activity, Alaska volcanoes tend to have more monitoring, said Tom Murray, USGS’s volcano science center director.
The rest of the Big 18 are: Mount Hood, Three Sisters, Newberry and Crater Lake in Oregon; Akutan Island, Makushin, Mount Spurr and Augustine in Alaska; Lassen and Long Valley in California; Mount Baker and Glacier Peak in Washington; and Mauna Loa in Hawaii.