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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).

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).

Keywords: hummocky | deposit | debris avalanche | debris avalanche deposit


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