161 Volcanoes in the U.S. Threaten Lives and Property, New Assessment Finds

Mount St. Helens in Washington spews smoke, soot and ash into the sky in April 1980. (AP Photo/Jack Smith)

As one of the most volcanically active nations on the globe, the United States has 161 volcanoes that pose a threat to lives and property, the U.S. Geological Survey said this week.

The USGS updated its Volcanic Threat Assessment for the first time since 2005, adding three volcanoes and taking 14 others out of the danger rankings in the contiguous United States. Across the entire country, 18 volcanoes are deemed a very high threat. Thirty-nine other volcanoes are classified as high threat, 49 are moderate, 34 are low, and 21 are very low threat.

USGS geologist John Ewert, lead author of the assessment, said that the list isn’t a prediction of which volcano will erupt next, but a guide for communities at the highest risk to focus on emergency preparedness and management measures.

“More than ten percent of the world’s known active and potentially active volcanoes are within U.S. territories,” Ewert said. “All of these volcanoes pose some degree of risk to people and infrastructure.”

Volcanoes were ranked and categorized using 24 factors including type of volcano, history including time between eruptions and effects experienced during past eruptions, explosiveness, exposure risk including population near the volcano, aviation impacts and infrastructure impacts.

The highest-threat volcanoes, starting with No. 1, are Kilauea in Hawaii, Mount St. Helens in Washington, Mount Rainier in Washington, Redoubt in Alaska, Mount Shasta in California, Mount Hood in Oregon, Three Sisters in Oregon, Akutan Island in Alaska, Makushin in Alaska, Mount Spurr in Alaska, Lassen in California, Augustine in Alaska, Newberry in Oregon, Mount Baker in Washington, Glacier Peak in Washington, Mauna Loa in Hawaii, Crater Lake in Oregon, and Long Valley Caldera in California.

More than 700 homes were destroyed, two dozen people were injured and the property damage price tag was at least $800 million in this summer’s Kilauea eruption. Lava plowed over 13.7 square miles.

Yellowstone, with its “recurrent earthquake swarms and ground deformation” and “changes in hydrothermal features,” ranked No. 21 on the list.

“Volcanoes can have long life spans, sometimes lasting millions of years, with dormant intervals ranging to tens of thousands of years, which makes a precise definition of an active or potentially active volcano problematic,” states the report. “For the purposes of this threat assessment, we considered only those volcanoes that have erupted in the geologically recent past (in Holocene time) in addition to three notably large and longlived caldera systems (Yellowstone, Wyoming; Valles, New Mexico; and Long Valley, California).”

Added to the threat rankings were Salton Buttes in Southern California’s Imperial Valley, which was added as a high threat; Soda Lakes, Nev., which was judged to be a moderate threat; and the Red Hill-Quemado volcanic field in New Mexico, added as a very low threat.

Dropped from the threat list were Mount Washington in Oregon, Lava Mountain in Oregon, Four Craters Lava Field in Oregon, Jackies Butte in Oregon, Brushy Butter in California, Big Cave in California, Twin Buttes in California, Tumble Buttes in California, Eagle Lake volcanic field in California, Lavic Lake volcanic field in California, Amboy Crater in California, Steamboat Springs in Nevada, Santa Clara volcanic field in Utah, and Bald Knoll in Utah.

Since 1980, 44 U.S. volcanoes have produced 120 eruptions and 52 “episodes of notable volcanic unrest,” USGS notes.

“The effects of eruptions are usually greatest near the volcano but can also extend far downstream, downwind, and can even persist over time. Airborne ash clouds have caused hundreds of millions of dollars of damage to aircraft and nearly brought down passenger jets flying in U.S. and international airspace,” the agency said. “Ash falls have caused agricultural losses and disrupted the lives and businesses of hundreds of thousands of people in Washington and Alaska. In California, noxious gas emissions have resulted in direct loss of life, and in Hawaii, have given rise to widespread human respiratory ailments.”