Global Volcanism Program | Image GVP-02677
The rock in the foreground is a hummock of a debris avalanche produced by collapse of the Augustine summit about 450 years ago. The avalanche swept into Kamishak Bay and traveled a distance of 11 km from the summit, forming the 2 x 3 km wide West Island. The fine-grained component of this avalanche hummock has been removed by the powerful Cook Inlet tides. The eruption was accompanied by a small lateral blast.
Photo by Lee Siebert, 1987 (Smithsonian Institution).