Agrigan, Mariana Islands

Location: 18.8N, 145.7E
Elevation: 3,165 feet (965 m)

Agrigan is a stratovolcano with a small caldera at its summit. The volcano forms an island about 4 miles (7 km ) in diameter. It is largest and tallest volcano in the northern Mariana Islands. Agrigan is made of basalt and lesser amounts of andesite. A single known historic eruption in 1917 threw blocks up to about 1 yard (1 m) in diameter as far as 3 miles (5 km) from the vent. About 10 feet (3 m) of ash fell on a coastal village. Deformation measurements made on Agrigan in 1992 revealed no significant changes since the volcano was first measured in 1990. Photograph by Frank Trusdell, U.S. Geological Survey, April 30, 1994.

In August of 1990 an increase in fumarole activity was observed on the cone within the caldera. No earthquakes were felt. The island's nine residents were evacuated. No eruption occurred. Photograph courtesy of CNMI.

A view facing southwest of the inside of the crater at the summit of Agrigan.

This photograph shows the deeply dissected slopes of the southwest flank of Agrigan.

This photograph shows the deeply dissected slopes of the west flank of Agrigan. The lower slopes are covered with palm trees, and the upper slopes are covered with swordgrass, making this area unpassable.

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Sources of Information:

Stern, R.J., 1978, Agrigan: An introduction to the geology of an active volcano in the northern Mariana Island arc: Bulletin of Volcanology, v. 41, p. 43-55.

Global Volcanism Network, 1992, Summary of Recent Activity: Bulletin of Volcanology, v. 55, p. 144.

Global Volcanism Network, 1990, Summary of Recent Activity: Bulletin of Volcanology, v. 52, p. 647.

Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.



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