Preliminary volcano-hazard assessment for the Tanaga volcanic cluster, Tanaga Island, Alaska

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.