Photo Information

View of landslide hummmocks, Mount Augustine volcano, Alaska
Photograph by R.B. Waitt in July 1988

One of the largest landslides that swept from Augustine volcano forms a 2 x 3 km-wide island called West Island, which consists of more than 1,000 hummocks. This view of the hummocks on West Island is looking toward the ESE about 8 km from the summit; a shallow lagoon (not visible) separates West Island from the main Augustine Island.

The West Island landslide occurred sometime between about 600 and 350 years ago, and was accompanied by a directed blast. Many hummocks are as tall as 20-30 m. The deposit may cover an area of about 30 km2 and have a rough volume of about 0.5 km3. The most recent landslide in 1883 A.D. extended the volcano's north shoreline as far as 2 km and produced a small tsunamis that swept across Cook Inlet.

The summit of Augustine volcano consists of several overlapping lava domes, and its flanks consist mostly of an apron of rock debris from pyroclastic flows and landslides that extends to the sea on all sides. The volume of the debris apron is several times the volume of the domes.

Augustine Island is located in southern Cook Inlet, about 100 km WSW of the town of Homer on the Kenai Peninsula and nearly 300 km SW from Anchorage.

More about Augustine volcano, from the Alaska Volcano Observatory.


Back to volcano-landslide deposits


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Last modification: 14 December 1999 (SRB)