Alaska contains over 140 volcanoes and volcanic fields which have been active within the last two million years. These volcanoes are catalogued on our website: https://www.avo.alaska.edu/volcano/.

Of these volcanoes, about 90 have been active within the last 10,000 years (and might be expected to erupt again), and more than 50 have been active in the past 300 years.

The volcanoes in Alaska make up well over three-quarters of U.S. volcanoes that have erupted in the last two hundred years.

Information on older volcanoes previously listed by AVO, and Alaskan mountains that have erroneous eruption reports can be found here.

Please use the Is Ash Falling form.

A list of all volcanoes in Alaska, presumed active within the last 2 million years, and their latitudes and longitudes, is available at https://www.avo.alaska.edu/explore/locations.

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First, the water that is stored in subducted sediments and in the oceanic crust is released. Then, at greater depths, water-bearing minerals (such as hornblende) change into non-water-bearing minerals (such as pyroxene). Water given off by this process, along with dissolved impurities, rises into the overlying mantle. The addition of water to the mantle lowers its melting point and is one of the primary processes that leads to the production of magma. Magma also forms as the mantle, stirred by the motion of the descending Pacific Plate, rises to a position beneath the volcanoes. The magma that results from these processes is less dense than the surrounding mantle and rises toward the surface of the earth. When it reaches the continental crust, which is less dense than mantle and the mantle-derived magma, it pools and begins to change in character. First it heats, then melts, and then mixes with the surrounding crust or country rock. As the magma cools, it begins to crystallize and the crystals that form differ in composition from the magma. This is important because the crystals separate from the liquid, which changes the magma's composition still further; it becomes richer in those chemical components not concentrated in the crystals. This process is called fractional crystallization, or fractionation.

The most fundamental change that results from the fractional crystallization of magma is the increase in silica. Throughout the fractionation process magma changes from the initial basalt to andesite and then to dacite. As the silica content of the magma increases, the magma continually becomes less and less dense until it reaches a point where it is lighter than the crust that surrounds it and then resumes its rise to the surface. Depending on the magma's rate of ascent, it can continue to crystallize, fractionate, and assimilate with the surrounding crust producing, in extreme cases, rhyolite with up to 76 percent silica.

When the magmas finally reach the surface, if they are relatively poor in dissolved gases, they erupt non-explosively and form lava flows or domes. If they are rich in dissolved gases, they explode violently (like a shaken soda bottle) and form columns of volcanic ash that can reach more than 15 kilometers (45,000 feet) into the atmosphere.

The processes outlined above are a thumbnail sketch of the complicated processes that form the volcanoes of the Aleutian Arc. Current models suggest that the Wrangell volcanoes formed in a very similar way and are associated with a small sliver of the Pacific Plate that is thrust northeastward beneath central Alaska. Several of the Wrangell volcanoes are among the most voluminous andesite volcanoes in the world - several times the volume of Mt. Rainier.

There are two major types of volcanoes in Alaska not directly tied to the Aleutian subduction zone. The first type is a series of small craters (and one larger one, Mt. Edgecumbe, near Sitka) scattered throughout southeastern Alaska. These small volcanoes may result from the intense shearing along many strike-slip transform faults that are caused by the northward movement of the Pacific Plate. Deep crustal fractures such as these faults may allow magma to rise and volcanoes to form in areas where magma could not normally reach the surface.

The second type of non-subduction volcanoes form the basalt fields of western Alaska. These fields typically consist of many basaltic cinder cones and lava flows, each of which formed over the course of only a few weeks or months. It has been suggested that at least some of these fields formed where tension in the earth produced deep fractures and thinning within the crust. The origin of these fields is not well understood, but they are analogous to the cinder cone fields northwest of the Japanese volcanoes in Southeast Asia, eastern China, and Korea.

Modified from Volcanoes of Alaska.

People do live in Alaska! Many Alaska communities can be directly affected by volcanic eruptions. The primary hazard is ashfall, which creates risks to public health, infrastructure, and aviation, affecting both routine flights as well as emergency transportation from airports such as Cold Bay or Dutch Harbor. About a dozen communities are within 50 kilometers of a volcano that has erupted within recent decades. Trace to minor ashfalls have also impacted communities in southcentral Alaska during recent eruptions of Cook Inlet volcanoes such as Redoubt, Spurr, and Augustine.

Our main volcanic hazard concerns are ash and aviation, as ash can cause severe damage to engines as well as other parts of the airplane. This means that eruptions from Alaska volcanoes may affect not just Alaskans, but also have rippling impacts to Asia-North American transportation routes. Alaska airspace is extremely busy with long-range, wide-body aircraft as well as bush planes and smaller aircraft. More than 50,000 people fly over or very near Alaska volcanoes as they travel the north Pacific and Russian Far East air routes. Because of Alaska's unique location, all direct air routes between the United States and Asia traverse this air space. In addition, the Anchorage International Airport is the third busiest cargo airport in the world (2022), and most of the aircraft carrying freight between Europe and Asia come through Anchorage for refueling. A considerable percentage of all airfreight on earth passes near Alaska's many volcanoes.

Encounters between aircraft and volcanic ash are serious because the ash can cause severe damage to the engines as well as other parts of the airplane. Two processes damage jet engines. The first damaging process is the mechanical abrasion of the moving parts in a jet engine, such as the compressor and turbine blades. This abrasion reduces the efficiency of the engine but does not typically cause engine failure. Another process with potentially more dangerous consequences is the introduction of ash into the hot parts of an aircraft's engines. Jet engines, particularly those on large airplanes used on international routes, operate near the melting temperature of volcanic ash. Ingestion of ash can clog fuel nozzles, combuster, and turbine parts causing surging, flame out, immediate loss of engine thrust, and engine failure.

The series of 1989-1990 eruptions from Mt. Redoubt had significant impact on the aviation and oil industries, as well as the people of the Kenai Peninsula. On the Kenai Peninsula, during periods of continuous ash fallout, schools were closed and some individuals experienced respiratory problems. At the Drift River oil terminal, lahars and lahar run-out flows threatened the facility and partially inundated the terminal on January 2, 1990 (Waythomas and others, 1998). The Redoubt eruption also damaged five commercial jetliners, and caused several days worth of airport closures and airline cancellations in Anchorage and on the Kenai Peninsula (Casadevall, 1994). Drifting ash clouds disrupted air traffic as far away as Texas. More information about the Redoubt 1989-1990 eruptions, including impact to people and infrastructure, is available here.

In recent years more than 80 jet airplanes have been damaged by volcanic ash worldwide. Seven of those encounters resulted in engine failure, although all seven eventually managed to restart enough engines to land without loss of life. In Alaska, potentially lethal ash clouds put aircraft at risk an average of four days per year." For more information on aircraft and volcanic ash, see Volcanic ash - danger to aircraft in the North Pacific. For detailed information on specific hazards at specific Alaska volcanoes, check out AVO's volcano-hazard reports.

Modified from Volcanoes of Alaska.

For more information, please visit https://www.avo.alaska.edu/volcano/ and check the hazards tab.

Please see Fields of Study.

On average, about two volcanoes erupt every year in Alaska, although many eruptions are spread over weeks and even months or years, so that in any single year it is not uncommon for three or four Alaska volcanoes to have experienced eruptive activity.

Most images on AVO's website are free for use by other people and publications. Please check the specific constraints displayed with the image you are interested in. If the image is available for use, please cite the photographer, as well as any agency the photographer was associated with. This information is provided with each image on AVO's site. If in doubt, please contact us via https://www.avo.alaska.edu/contact/.

Scientists from AVO often do work on other volcanoes, particularly in times of a volcanic crisis elsewhere in the United States (for example, some AVO scientists traveled to Hawai'i to help with recent eruptions.)

AVO does not distribute rocks or ash samples to the public. AVO collects rocks and ash samples for scientific analysis in support of its mission to better understand volcanic behavior in order to save lives, avoid damage to aircraft and other property, and to provide timely warnings of explosive activity. Samples are collected for use by AVO and its scientific collaborators only.

You can find them here in our reference search.

Sign up for the USGS Volcano Notification Service, located here.