Global Volcanism Program | Image GVP-02679
This hilly terrain is the surface of the debris avalanche deposit from summit collapse about 250-450 years ago, which forms the entire 2 x 3 km wide West Island. There are more than 1,000 hummocks of heights up to 30 m across the island. Bathymetric surveys suggest that the avalanche traveled an additional 3 km beyond the margin of West Island. Kamishak Bay and the Chigmit Mountains are on the horizon to the NW.
Photo by Lee Siebert, 1986 (Smithsonian Institution).