Global Volcanism Program | Image GVP-02138
Alamagan, seen here from the W with two peaks on either side of a roughly 350-m-deep summit crater, is the emergent summit of a large submarine volcano. The exposed cone is largely Holocene in age and the SW flank contains a 1 x 1.6 km graben. Pyroclastic flow deposits have been dated at about 1,000 years old.
Photo by Norm Banks, 1981 (U.S. Geological Survey).