Update, October 29, 2018: The Yellowstone Observatory posted more information on Yellowstone Caldera’s ranking and on the threat assessment process today.
It’s a little early to be making top-ten lists for 2018, but the USGS just released their 2018 update to the National Volcanic Threat Assessment:
Which #volcanoes are the most threatening in the U.S.?
— USGS Volcanoes🌋 (@USGSVolcanoes) October 24, 2018
The link takes you to an abstract of the report and a free PDF download.
Note that threat level doesn’t mean that the volcano is about to erupt. They looked at the bigger picture, placing volcanoes according to how they scored on a list of potential hazards.
If we had assessed only the hazards aspects of U.S. volcanoes, then the generally more explosive volcanoes in Alaska and CNMI [the Marianas**] would be more strongly represented in the higher (more hazardous) ranks. Because we include exposure factors in the assessment, volcanoes in CONUS are more strongly represented in the highest threat category owing to the greater nearby ground-based and airborne population, and more critical infrastructure exposed to volcano hazards . . .Eleven of the 18 [very high threat] volcanoes are in Washington, Oregon, and California, where explosive and often snow- and ice-covered edifices can project flowage hazards long distances to reach densely populated and highly developed areas. Five of the 18 volcanoes are in Alaska, near important population centers, economic infrastructure, or below busy air traffic corridors. The remaining two very high threat volcanoes are on the Island of Hawaiʻi, where densely populated and highly developed areas now exist on the flanks of highly active volcanoes. Large eruptions from any of these very high threat volcanoes could cause regional- or national-scale disasters.
**: In its October 26th weekly update, the USGS says that Supertyphoon Yutu has destroyed ground-based monitoring equipment on Saipan, affecting all CNMI volcanoes, including Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Sarigan, Pagan, Almagan and Guguan. Only satellite monitoring is possible now.
Ten Most Hazardous Volcanoes
The ten highest-threat volcanoes on the list are: