Alamagan

Photo of this volcano
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 17.6°N
  • 145.83°E

  • 744 m
    2440 ft

  • 284180
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: January 1999 (BGVN 24:01) Citation IconCite this Report


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.

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

Bulletin Reports - Index


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




Information is preliminary and subject to change. All times are local (unless otherwise noted)


September 1990 (BGVN 15:09) Citation IconCite this Report


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.


June 1992 (BGVN 17:06) Citation IconCite this Report


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.


January 1999 (BGVN 24:01) Citation IconCite this Report


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.

Eruptive History


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.

Photo Gallery


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).
See title for photo information.

Smithsonian Sample Collections Database


There are no samples for Alamagan in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

Affiliated Sites