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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 17.6°N
  • 145.83°E

  • 744 m
    2440 ft

  • 284180
  • Latitude
  • Longitude

  • Summit

  • Volcano

The Global Volcanism Program has no activity reports for Alamagan.

The Global Volcanism Program has no Weekly Reports available for Alamagan.

Index of Monthly Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

09/1990 (BGVN 15:09) Seismic station installed

06/1992 (BGVN 17:06) Fumarolic activity but no shallow seismicity

01/1999 (BGVN 24:01) False eruption report

Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

All times are local (= UTC + 10 hours)

09/1990 (BGVN 15:09) Seismic station installed

Fieldwork was conducted . . . 28 September-3 October . . . . A regional network of single vertical-component, short-period seismometers was installed, with instruments located on the islands of Pagan, Alamagan, and Anatahan, and a receiving station on Saipan. . . .

Information Contacts: R. Koyanagi, HVO.

06/1992 (BGVN 17:06) Fumarolic activity but no shallow seismicity

A six-member team of USGS volcanologists visited the Commonwealth of the Northern Mariana Islands 11-27 May 1992 at the request of the CNMI Office of Civil Defense. The team observed all of the islands in the chain N of Saipan, installed a new seismic station at the base of frequently active Pagan, remeasured existing EDM networks, mapped the geology of Alamagan, sampled fumaroles and hot springs, and collected rocks and charcoal for radiocarbon dating.

[At Alamagan] the team measured a temperature of 72°C at one fumarole. No shallow earthquakes or volcanic tremor have been recorded on the Alamagan seismic station since it was installed in September 1990. Charcoal was collected that should date the youngest and one of the oldest eruptions.

Information Contacts: R. Moore, USGS; R. Koyanagi, M. Sako, and F. Trusdell, HVO.

01/1999 (BGVN 24:01) False eruption report

News reports from the Commonwealth of the Northern Mariana Islands (CNMI) during 23-24 December indicated that a small group of residents had been evacuated from Alamagan Island by helicopters after the volcano of the same name showed signs of activity. Although five men were taken off the island due to fears of an eruption, an increased volume of steaming apparently led to the false alarm.

Nobody with the technical capability to make a volcanological assessment accompanied the evacuation helicopters, but Greg Guerrero, the Acting Director of the Emergency Management Office discussed the situation with the evacuees and with USGS seismologist Robert Koyanagi in Hawaii. There were no tremors or rumblings felt, and no eruption noises were heard. It is believed that rain penetrating fissures in the volcanic edifice, following a dry period, resulted in a greater than normal amount of steaming. The seismic station installed in 1990 (BGVN 15:09) was not operational due to a lack of funding for batteries. Fieldwork in 1992 (BGVN 17:06) identified one fumarole with a temperature of 72°C.

Reference. Moore, R.B., and Trusdell, F.A., 1993, Geologic map of Alamagan volcano, northern Mariana Islands: U.S. Geological Survey Map I-2408, 1:12,500.

Information Contacts: Greg Guerrero, Emergency Management Office, Commonwealth of the Northern Mariana Islands; Debbie Subera-Wiggins and Jeff Schorr, Insular Affairs Office, Department of the Interior, Washington, DC 20240 USA; Robert Koyanagi, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii Volcanoes National Park, HI 96718, USA.

Alamagan is the emergent summit of a large stratovolcano in the central Mariana Islands with a roughly 350-m-deep summit crater east of the center of the island. The exposed cone is largely Holocene in age. A 1.6 x 1 km graben cuts the SW flank. An extensive basaltic-andesite lava flow has extended the northern coast of the island, and a lava platform also occurs on the south flank. Pyroclastic-flow deposits erupted about 1000 years ago have been dated, but reports of historical eruptions were considered invalid (Moore and Trusdell, 1993).

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
[ 1887 Nov 29 ] [ Unknown ] Uncertain    
[ 1864 Jan ] [ Unknown ] Uncertain    
0870 ± 100 years Unknown Confirmed 4 Radiocarbon (uncorrected)
0540 ± 75 years Unknown Confirmed   Radiocarbon (uncorrected)

The Global Volcanism Program has no synonyms or subfeatures listed for Alamagan.

Alamagan, seen here from the west with two peaks on either side of a roughly 350-m-deep summit crater, is the emergent summit of a large stratovolcano. Low-angle lava platforms occur at the northern and southern coasts, whereas the eastern and western flanks are steeper. The exposed cone is largely Holocene in age. A 1.6 x 1 km graben cuts the SW flank. Pyroclastic-flow deposits erupted about 1000 years ago have been dated, but reports of historical eruptions were considered invalid.

Photo by Norm Banks, 1981 (U.S. Geological Survey).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Bloomer S H, Stern R J, Smoot N C, 1989. Physical volcanology of the submarine Mariana and Volcano arcs. Bull Volc, 51: 210-224.

Corwin G, 1971. Quaternary volcanics of the Mariana Islands. Unpublished manuscript, 137 p.

Katsui Y (ed), 1971. List of the World Active Volcanoes. Volc Soc Japan draft ms, (limited circulation), 160 p.

Kuno H, 1962. Japan, Taiwan and Marianas. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 11: 1-332.

Meijer A, Reagan M, 1983. Origin of K2O-SiO2 trends in volcanoes of the Mariana arc. Geology, 11: 67-71.

Moore R B, Trusdell F A, 1993. Geologic map of Alamagan volcano, northern Mariana Islands. U S Geol Surv Map I-2408, 1:12,500 scale.

Volcano Types


Tectonic Setting

Subduction zone
Crustal thickness unknown

Rock Types

Andesite / Basaltic Andesite
Basalt / Picro-Basalt


Within 5 km
Within 10 km
Within 30 km
Within 100 km

Affiliated Databases

Large Eruptions of Alamagan Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.