Volcanism in Northern Islands

The Northern islands, with the exception of Farallon de Medinilla, are volcanic. The volcanoes on Pagan and Farralon de Pajaros are currently active, while the others are dormant. The sites below contain detailed information about the volcanic history and underlying geology of the Northern Islands.

Future Hazards & Risk Study in Planning: The CNMI Government is currently seeking funding to do a detailed hazards and risk study of four volcanic islands –Anatahan, Alamagan, Pagan and Agrigan– to determine if and where the types of facilities envisioned should be built and to maximize safety and minimize risks for people living there.

Because of the possibility that eruptions will occur in the future, it is essential that a fail-proof monitoring system be put in place for each inhabited island, should eruption warnings or evacuation ever be needed in t he future. CNMI agencies including the Emergency Management Office will coordinate the U.S. Geological Survey to ascertain the amount of work that needs to be done.

Anatahan Volcano

The first historical eruption of Anatahan Volcano began suddenly on the evening of May 10, 2003. No one was directly threatened by the initial strong explosive activity, because residents had long before evacuated the small volcanic island.

Anatahan Volcano is located 120 km (75 miles) north of Saipan Island and 320 km (200 miles) north of Guam. The island is about 9 km (5.6 miles) long and 3 km (2 miles) wide. Anatahan is a stratovolcano that contains the largest known caldera in the Northern Mariana Islands.

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Alamagan Volcano

Alamagan is a stratovolcano about 30 km south of the island of Pagan. Two historic eruptions are suspected in 1864 and 1887.

Alamagan is a large stratovolcano in the central Mariana Islands. The volcanic island is 9.5 km x 6 km in size. It contains a 2 km wide caldera. An large basaltic-andesite lava flow has extended the northern coast of the island, and a lava platform also occurs on the southern flank.

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Pagan Volcano

Pagan Volcano consist 2 stratovolcanoes (North and South Pagan) were constructed within calderas, 7 and 4 km in diameter, respectively. The 570-m-high Mount Pagan at the NE end of the island rises above the flat floor of the northern caldera, which may have formed less than 1000 years ago. It is located 173 nautical miles north of Saipan. (from: Smithsonian / GVP)

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Agrigan Volcano

Agrigan volcano is an active stratovolcano and the highest of the volcanoes in the Marianas volcanic arc. It contains contains a 500-m-deep, flat-floored caldera. The last confirmed eruption was in 1917.

The highest of the Marianas arc volcanoes, Agrigan 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.

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