Tsunami — Admiralty Island, Alaska

2025-08-10 · Admiralty Island, Alaska

Event narrative

The landslide generated tsunami scoured trees and vegetation from Sawyer Island and had an estimated runup height on the opposite side of the fjord of 1500-1600 feet. Kayakers near the entrance of Tracy Arm on Harbor Island had some of their gear swept away by a 15 to 20 foot tidal wave.

Wider weather episode

USGS and the Alaska Earthquake Center reported that seismic activity was measured at 526am AKDT on the 10th of August in vicinity of Tracy Arm south of Juneau. The seismic measurement had a landslide signature that they recognized and further USGS ground investigations confirmed that a large mass of the mountain fell into the water at the terminus of South Sawyer Glacier, generating a massive tsunami and successive waves that scoured trees and vegetation from both sides of the fjord and Sawyer Island. As a result, a significant amount of debris remained in the fjord and nearby areas for days after the event and disrupted navigation.

Source: NOAA Storm Events Database, event_id 1293435. Narrative written by the NWS forecast office that issued the report.