The red triangles are volcano locations. Dark-orange areas have a higher volcanic hazard; 

light-orange areas have a lower volcanic hazard. Dark-gray areas have a higher ash fall hazard; 

light-gray areas have a lower ash fall hazard. Information is based on data during the past 

10,000 years. Bottom, from left to right: Hawaii, Alaska, Puerto Rico, and the Commonwealth of 

the Northern Mariana Islands. Map not to scale. Sources: the National Atlas and the USGS 

An Explosive Danger

When the violent energy of a volcano is unleashed, the results are often 

catastrophic. The risks to life, property, 

and infrastructure from volcanoes are 

escalating as more and more people live, 

work, play, and travel in volcanic regions. 

Since 1980, 45 eruptions and 15 cases 

of notable volcanic unrest have occurred 

at 33 U.S. volcanoes. 

Lava flows, debris avalanches, and 

explosive blasts have invaded communities, swept people to their deaths, choked 

major riverways, destroyed bridges, and 

devastated huge tracts of forest. 

Noxious volcanic gas emissions 

have caused widespread lung problems. 

Airborne ash clouds have disrupted the 

health, lives, and businesses of hundreds 

of thousands of people; caused millions 

of dollars of aircraft damage; and nearly 

brought down passenger flights.

 Volcano Impacts USGS Science Priorities

• About 11 percent of the world’s ac-

 tive volcanoes are located in the United 

 States. Many of them lie below active 

 air traffic routes.

• From 1973 through 2003, about 100 

 encounters of aircraft with airborne vol-

 canic ash have been documented. About 

 20 percent of the reported encounters in-

 volved significant damage to engines 

 and airframes. In eight encounters, dam-

 age was so severe that in-flight engine 

 failures occurred. 

• Mount Rainier volcano in Washington

 State is one of the Nation’s most danger-

 ous volcanoes. More than 100,000 

 people live in areas near Rainier that 

 have been buried by volcanic debris 

 flows during the past few thousand years.

 Apply National Volcano Early Warning 

 System report recommendations:

• Monitor hazardous U.S. volcanoes at 

 levels appropriate to the threats posed

• Establish a 24-7 volcano watch office

• Provide rapid event notification during 

escalating unrest and eruptions, aiming 

for a 5-minute warning of major explosive 

• Continue research into how volcanoes 

 work

• Integrate real-time ground-based, air-

 borne, and remote-sensing techniques

• Coordinate volcano-monitoring resourc-

 es across agencies and institutions

USGS Science Helps Build Safer Communities

Volcano Hazards—A National Threat

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006–3014

February 2006 Printed on recycled paper

Volcanic hazards and activity in the United States and its Territories 

Mount St. Helens in Washington State 

explosively erupts on Sunday, May 18, 1980. 

The eruption led to 57 deaths. (USGS photo/

D.A. Swanson)
For More Information

http://volcanoes.usgs.gov/ 

http://www.usgs.gov/

 Volcano Facts

• The United States is one of the most volcanically rich countries in the world, 

 with 169 active and dormant volcanoes.

• Of the 55 volcanoes that pose the biggest threat to the United States, approxi-

 mately half are significantly undermonitored.

• Volcanoes account for approximately 5 percent of all tsunamis in the past 

 250 years.

 

• Mauna Loa, in Hawaii, is the world’s largest active volcano.

• The Cascade Range—home to more than a dozen large, active volcanoes— 

 extends more than 1,000 miles from Mount Baker in northern Washington to 

 Lassen Peak in northern California. Although Cascade volcanoes do not often 

 erupt (on average, about two erupt each century), they can be dangerous because 

 of their violently explosive behavior, their permanent snow and ice cover that 

 can fuel large volcanic debris flows (lahars), and their proximity to various criti-

 cal infrastructure, air routes, and populated areas in Washington, Oregon, and 

 California. 

• Erupting Cascade volcanoes are more prone than other U.S. volcanoes to explo-

 sive volcanic activity, resulting in pyroclastic flows. These are hot, often incan-

 descent mixtures of volcanic fragments and gases that sweep along close to the 

 ground at speeds up to 450 mph. Pyroclastic flows occurred in the 1980 eruption 

 of Mount St. Helens. 

• During the 1980 Mount St. Helens eruption, in which 57 people died, the total 

 volume of the ash produced equaled an area as wide and long as a football field 

 and about 150 miles high. 

Tools for Today

The U.S. Geological Survey (USGS) 

is responsible for issuing timely warnings 

of potential volcanic disasters to affected 

communities and civil authorities. 

USGS scientists, with State, Federal, 

and academic partners, operate five volcano observatories that monitor volcanic 

activity in Hawaii, the Cascade Range, 

Alaska, Long Valley in California, Yellowstone National Park, and the Northern 

Mariana Islands. 

After 25 years of intense research on 

restless volcanoes in the United States 

and around the globe, the USGS has 

greatly advanced its ability to evaluate volcanic risks and hazards. In the 

process, the USGS has helped save tens 

of thousands of lives and has developed 

a suite of new volcano-monitoring tools. 

Many of these tools allow large amounts 

of data to flow in realtime from remote 

volcanoes to observatories for analysis 

and interpretation.

The USGS can now better anticipate 

volcanic hazards in time for civil authorities, communities, and the aviation sector 

to take preparatory actions—but only if a 

volcano is adequately monitored with instrument networks in place before unrest 

develops.

Preparing for Tomorrow

Volcanic eruptions herald their coming over periods of days to years with 

detectable signals of unrest. Many human 

risks associated with eruptions can be 

drastically reduced through the use of 

hazards assessments, response planning among scientists, State, and local 

authorities, and proper monitoring and 

technology.

In 2005, the USGS released the first 

ever comprehensive and systematic 

review of the 169 U.S. volcanoes. The 

report establishes a framework for a 

National Volcano Early Warning System 

(NVEWS). The framework calls for enhanced instrumentation and monitoring 

at targeted volcanoes, and a 24-7 volcano 

watch office to improve the ability to 

provide rapid, reliable hazard warnings.

The NVEWS report ranks the most 

dangerous U.S. volcanoes that pose a 

threat to human lives, property, and aviation safety and also discusses monitoring 

gaps at each volcano. Alaska, California, Washington State, Oregon, Hawaii, 

Wyoming, and the Commonwealth of 

the Northern Marianas have dangerous 

volcanoes with either significant monitoring gaps or no monitoring in place. The 

report can be accessed online at http://

pubs.usgs.gov/of/2005/1164/.

To help keep communities safe, it is 

essential to monitor hazardous volcanoes 

so that the public knows when unrest begins and what hazards can be expected. 

The USGS helps the public, policymakers, and emergency managers make 

informed decisions on how to prepare for 

and react to volcano hazards and reduce 

losses from future volcanic eruptions and 

debris flows.

This house in Kalapana, Hawaii, is burned 

by approaching lava from Kilauea Volcano 

on Sunday, April 22, 1990. Most of Kalapana 

was destroyed by lava flows between 1986 

and 1990, with 180 homes lost. (USGS photo)