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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2007–5094

Preliminary Volcano-Hazard Assessment for the Tanaga Volcanic Cluster, Tanaga Island, Alaska

By Michelle L. Coombs, Robert G. McGimsey, and Brandon L. Browne

Summary of Volcano Hazards at Tanaga Volcanic Cluster

The Tanaga volcanic cluster lies on the northwest part of Tanaga Island, about 100 kilometers west of Adak, Alaska, and 2,025 kilometers southwest of Anchorage, Alaska. The cluster consists of three volcanoes—from west to east, they are Sajaka, Tanaga, and Takawangha. All three volcanoes have erupted in the last 1,000 years, producing lava flows and tephra (ash) deposits. A much less frequent, but potentially more hazardous phenomenon, is volcanic edifice collapse into the sea, which likely happens only on a timescale of every few thousands of years, at most. Parts of the volcanic bedrock near Takawangha have been altered by hydrothermal activity and are prone to slope failure, but such events only present a local hazard. Given the volcanic cluster’s remote location, the primary hazard from the Tanaga volcanoes is airborne ash that could affect aircraft. In this report, we summarize the major volcanic hazards associated with the Tanaga volcanic cluster.

Contents

Summary of Volcano Hazards at Tanaga Volcanic Cluster
Introduction
Physical Setting and Features of Tanaga Volcanic Cluster
Eruptive Activity of Tanaga Volcanic Cluster
Volcano Hazards at Tanaga Volcanic Cluster
Event Frequency and Risk at Tanaga Volcanic Cluster
Hazard Warning and Mitigation
References Cited
Glossary

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Send questions or comments about this report to the author, M.L. Coombs, (907) 786-7403.

For more information about USGS activities in Alaska, visit the USGS Alaska Science Center home page.