Skip to main content
U.S. flag

An official website of the United States government

Agrigan

Find U.S. Volcano

The highest of the Marianas arc volcanoes, Agrigan (also spelled Agrihan) contains a 500-m-deep, flat-floored caldera. 

Quick Facts

Location: Commonwealth of the Northern Mariana Islands

Latitude: 18.77° N​​​​​​​

Longitude: 145.67° E​​​​​​​

Elevation: 965 (m) 3,166 (f)​​​​​​​

Volcano type: Stratovolcano​​​​​​​

Composition: Basalt - Andesite​​​​​​​

Most recent eruption: 1917 CE

Threat Potential: High*

*based on the National Volcano Early Warning System

Summary

Agrigan Island
Sources/Usage: Public Domain. View Media Details
Agrigan Island image taken from NASA Space Shuttle.

The highest of the Marianas arc volcanoes, Agrigan (also spelled Agrihan) contains a 500-m-deep, flat-floored caldera. The elliptical island is 8 km long; its 965-m-high summit is the top of a massive 4000-m-high submarine volcano, the second largest in the Marianas Islands. Deep radial valley dissect the flanks of the thickly vegetated stratovolcano. The elongated caldera is 1 x 2 km wide and is breached to the NW, from where a prominent lava flow extends to the coast and forms a lava delta. The caldera floor is surfaced by fresh-looking lava flows and also contains two cones that may have formed during the volcano's only historical eruption in 1917. This eruption deposited large blocks and 3 m of ash and lapilli on a village on the SE coast, prompting its evacuation. From the Smithsonian Global Volcanism Program.

Publications

Volcanic hazards in the Pacific U.S. Territories

The Commonwealth of the Northern Mariana Islands, Guam, and American Samoa lie along the western side of the famed Pacific Ring of Fire. Here, the processes of active island and submarine volcanoes produce activity both underwater and in the atmosphere that poses potential hazards to the daily lives of residents and travelers. Since 2000, CNMI volcanoes have erupted six times, and one submarine vo
Authors
Gabrielle Tepp, Brian Shiro, William W. Chadwick
By
Volcano Hazards Program, Volcano Science Center, Agrigan, Ahyi Seamount, Alamagan, Anatahan, Asuncion, Daikoku Seamount , East Diamante, Esmeralda Bank, Farallon de Pajaros, Fukujin Seamount , Guguan, Kasuga 2, Maug Islands, Ofu-Olosega, Pagan, Ruby, Sarigan, South Sarigan Seamount, Supply Reef, Ta'u Island, Tutuila Island, Zealandia Bank, Subduction Zone Science

2018 update to the U.S. Geological Survey national volcanic threat assessment

When erupting, all volcanoes pose a degree of risk to people and infrastructure, however, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location. Assessing the relative threats posed by U.S. volcanoes identifies which volcanoes warrant the greatest risk-mitigation efforts by the U.S. Geological Survey and its partners. This update

Authors
John W. Ewert, Angela K. Diefenbach, David W. Ramsey
By
Volcano Hazards Program, Volcano Science Center, Agrigan, Ahyi Seamount, Alamagan, Anatahan, Asuncion, Belknap, Black Butte Crater Lava Field, Black Rock Desert Volcanic Field, Blue Lake Crater, Carrizozo Lava Flow, Cascade Range Weekly Update, Cinnamon Butte, Clear Lake Volcanic Field, Coso Volcanic Field, Crater Lake, Craters of the Moon Volcanic Field, Daikoku Seamount , Davis Lake Volcanic Field, Devils Garden Lava Field, Diamond Craters Volcanic Field, Dotsero Volcanic Center, East Diamante, Esmeralda Bank, Farallon de Pajaros, Fukujin Seamount , Glacier Peak, Guguan, Haleakalā, Hell's Half Acre Lava Field, Hualālai, Indian Heaven Volcanic Field, Jordan Craters Volcanic Field, Kama‘ehuakanaloa, Kasuga 2, Kīlauea, Lassen Volcanic Center, Long Valley Caldera, Mammoth Mountain, Markagunt Plateau Volcanic Field, Maug Islands, Mauna Kea, Mauna Loa, Medicine Lake, Mono Lake Volcanic Field, Mono-Inyo Craters, Mount Adams, Mount Bachelor, Mount Baker, Mount Hood, Mount Jefferson, Mount Rainier, Mount Shasta, Mount St. Helens, Newberry, Ofu-Olosega, Pagan, Red Hill-Quemado Volcanic Field, Ruby, Salton Buttes, San Francisco Volcanic Field, Sand Mountain Volcanic Field, Sarigan, Soda Lakes, South Sarigan Seamount, Supply Reef, Ta'u Island, Three Sisters, Tutuila Island, Ubehebe Craters, Uinkaret Volcanic Field, Valles Caldera, Wapi Lava Field, Weekly Update, West Crater Volcanic Field, Yellowstone, Zealandia Bank, Zuni-Bandera Volcanic Field

Volcanic investigations in the Commonwealth of the Northern Mariana Islands, April to May 1994

A team of U.S. Geological Survey geologists, a seismologist, and technicians gathered new geologic, seismic, and deformation data in the Commonwealth of the Northern Mariana Islands (CNMI). Nine volcanic islands on the active East Mariana Ridge north of Saipan were examined between April 20 and May 3, 1994. In addition, a new radio-telemetry seismic station was installed on the island of Agrihan (

Authors
M. K. Sako, F. A. Trusdell, R. Y. Koyanagi, George Kojima, R. B. Moore
By
Natural Hazards Mission Area, Volcano Hazards Program, Volcano Science Center, Agrigan, Ahyi Seamount, Alamagan, Anatahan, Asuncion, Daikoku Seamount , East Diamante, Esmeralda Bank, Farallon de Pajaros, Fukujin Seamount , Guguan, Kasuga 2, Kīlauea, Maug Islands, Pagan, Ruby, Sarigan, South Sarigan Seamount, Supply Reef, Zealandia Bank
View All

Quick Facts

Location: Commonwealth of the Northern Mariana Islands

Latitude: 18.77° N​​​​​​​

Longitude: 145.67° E​​​​​​​

Elevation: 965 (m) 3,166 (f)​​​​​​​

Volcano type: Stratovolcano​​​​​​​

Composition: Basalt - Andesite​​​​​​​

Most recent eruption: 1917 CE

Threat Potential: High*

*based on the National Volcano Early Warning System

Volcano Hazards Program Links