Special Report

50 Most Dangerous Volcanoes in America

Detailed Findings & Methodology

Because of its disproportionately high number of active volcanoes and high population density, Indonesia has by far the highest volcanic threat level of all countries. Along the boundaries of tectonic plates, there are plenty of active volcanoes in the United States as well.

Twenty-six of the 50 volcanoes listed are in Alaska, seven are in California, five are in Washington, and there are four in each Oregon and the Northern Mariana Islands. One, Yellowstone, is in Wyoming.

Apart from the current eruption in Hawaii, the most recent eruptions in the United States were in Alaska. Pavlof, Veniaminof, and Shishaldin erupted in 2016, 2015, and 2013, respectively. But as these volcanoes are located along the remote and sparsely populated Aleutian Islands, eruptions there are less threatening than those that might occur in many other parts of the country.

The last eruption in California was 100 years ago — relatively recent by geological standards. The state is home to the iconic cone of Mount Shasta, the lava domes of the Mono-Inyo Craters, and to frequent steam explosions of Ubehebe Craters.

In addition to land damage from lava flows and health risks from toxic gas, other consequences include obstruction to air travel. Between 1953 and 2010, there were approximately 80 incidents involving aircrafts and volcanic ash that resulted in damage to the aircraft. Of these encounters, nine resulted in engine shutdown during flight.

The timeline of a volcano is quite long. Geological studies have demonstrated that about 600 volcanoes have erupted at some point since the year 1500, and about 866 volcanoes have a record spanning the last 10,000 years.

Volcanoes are considered to be either extinct, dormant, or active. Because most volcanoes alternate between long periods of rest and short bursts of activity, it is not uncommon for volcanoes to unexpectedly move between these categories. For example, before the 2010 volcanic eruption in Indonesia, Sinabung was considered dormant.

Both a volcano’s eruption and the aftermath can last a very long time. In 1943, for example, the cornfields of the Mexican state of Michoacan broke open and a new volcano, Paricutin, was born. That eruption lasted nine years. As Mandeville explained, much of the devastation resulting from volcanic eruptions can be permanent. Farmland engulfed in lava flow cannot be reclaimed for decades.

To identify America’s 50 most dangerous volcanoes, 24/7 Wall St. reviewed threat scores from the USGS report, “An Assessment of Volcanic Threat and Monitoring Capabilities in the United States: Framework for a National Volcano Early Warning System.” Scores are as of 2005 (Mandeville confirmed the threat levels of hazardous volcanoes are very unlikely to have changed since then). The last eruption year, as well as the population within 30 kilometers and 100 kilometers was obtained from the Smithsonian Institution’s National Museum of Natural History Global Volcanism Program. When unavailable, we listed the population of the town nearest to the volcano.