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Agrigan Volcano | John Seach
Mariana Islands
18.77 N, 145.67 E
summit elevation 965 m
stratovolcano
Agrigan volcano is Agrigan is the highest and largest (44 sq km) of the volcanoes in the northern Mariana Islands. The island is oval shaped with a diameter of 6.2 x 9.7 km.
The flanks of the volcano are covered by andesitic pyroclastics. The island is asymmetrical. The western flank of the island has a slope of 20 degrees, with the eastern flank's slope 30 degrees.
A flat-floored crater with a diameter of 4 sq km, and depth of 500 m, is located north of the island centre. In the middle of the crater are two low, broad volcanic cones. The crater contains nearly vertical walls.
The northern shoreline of the island contains a crater which is open to the sea.
1990 Fumarolic Activity
An increase in fumarolic activity in August 1990 was suggested by observations from an overflight. This resulted in evacuation of nine residents. A survey of the volcano in September 1990 showed the summit contained weak fumarolic activity with sulfur deposition and boiling hot springs, but no evidence of renewed activity.
1917 Eruption
The only recorded historical eruption at Agrigan volcano occurred in 1917 when an explosive activity resulted in the evacuation of a village on the SE coast. Activity was concentrated from a cone in the summit crater.
Further reading
Stern, Robert James. "On the origin of andesite in the northern Mariana island arc: Implications from Agrigan." Contributions to Mineralogy and Petrology 68.2 (1979): 207-219.
Stern, R. J. "Agrigan: an introduction to the geology of an active volcano in the northern Mariana island arc." Bulletin Volcanologique 41.1 (1978): 43-55.
Agrigan Volcano Eruptions
1917