The island is mountainous and oval shaped with a land area of 80.04 square miles (207.3 km2).

The island consists of several overlapping stratovolcanoes, and it contains two calderas each with central volcanic cones.

On March 6, 1977 USCGC Mellon WHEC 717 spotted a volcanic eruption just a few hours old on Seguam Island in the Aleutian chain.

On recent activity has occurred at Pyre Peak, the cone within the western caldera and the highest point on the island, and has produced explosive eruptions and basaltic lava flows.

This article about a location in the Aleutians West Census Area, Alaska is a stub.