While Hawaii and Alaska are the two states most often associated with volcanic eruptions, 11 of the 18 very highest threat volcanoes on U.S. soil are located in the Western United States – 4 in Washington, 4 in Oregon & 3 in California. (note: Yellowstone is ranked 21st).
The updated national volcanic threat assessment presented here is not a forecast or indication of which volcanoes are most likely to erupt next. Rather, it is an indicator of the potential severity of impacts that may result from future eruptions at any given volcano. As such, the assessment can be used to help guide and prioritize volcano research, hazard assessment, emergency planning and preparation, and monitoring efforts by Federal, state, and local government.
- In 2010 airline traffic in Europe was disrupted by the eruption of Iceland’s Eyjafjallajökull volcano (see study The vulnerability of the European air traffic network to spatial hazards), halting many flights for nearly a week.
- When Mount Pinatubo erupted in the Philippines in 1991, within a year its aerosol cloud had dispersed around the globe, resulting in `an overall cooling of perhaps as large as -0.4°C over large parts of the Earth in 1992-93’ (see USGS The Atmospheric Impact of the 1991 Mount Pinatubo Eruption).
- In 1783 the Craters of Laki in Iceland erupted and over the next 8 months spewed clouds of clouds of deadly hydrofluoric acid & Sulphur Dioxide, killing over half of Iceland’s livestock and roughly 25% of their human population. These noxious clouds drifted over Europe, and resulted in widespread crop failures and thousands of deaths from direct exposure to these fumes (see 2012 UK: Civil Threat Risk Assessment)
The 40 page 2018 update to the U.S. Geological Survey national volcanic threat assessment and summary are available at this USGS link.