A farmer walks through a thick cloud of volcanic ash. (Photographer: Ragnar Axelsson/Bloomberg)

U.S. Geological Survey Sees 18 Volcanoes as 'Very High Threat'

(Bloomberg) -- A new U.S. Geological Survey national volcanic threat assessment identified 18 volcanoes as a "very high" risk. The threat assessment reviewed 161 active volcanoes in the U.S. and divides them into five threat categories. In addition to the 18 very high threat volcanoes, the rest of the total includes 39 high threat, 49 moderate threat, 34 low threat, and 21 very low threat volcanoes.

While the vast majority of the active volcanoes are in Alaska and Hawaii, more than half of the highest threat category volcanoes are in Washington, Oregon or California. These west coast volcanoes were deemed very high threat because "explosive and often snow- and ice-covered edifices can project hazards long distances to densely populated and highly developed areas," according to the report.

High threat volcanoes are identified as such due to their proximity to population centers, busy air traffic routes, economic infrastructure or due to increasing activity within the volcanic structures.

U.S. Geological Survey Sees 18 Volcanoes as 'Very High Threat'

The threat assessment index does not identify which volcanoes are likely to erupt soonest, but rather it identifies risk areas. The most dangerous volcano is Hawaii’s Kilauea, which erupted earlier this year.

On a global scale, no U.S. city ranks among the world’s most at risk cities using Swiss Reʼs proprietary global volcano model. The Swiss Re model ranks Managua, the capital of Nicaragua, as the city with the highest expected substantial loss to its country-wide economy from a volcanic eruption. Among the top 15 highest ranked cities, 12 are located along ’the ring of fire’ -- an area of high volcanic activity -- which follows the edges of the Pacific Ocean.

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