A massive landslide in Alaska's Glacier Bay triggered a near-record tsunami on August 10, 2025, sending waves 1,580 feet up the fjord walls. The event ranks as the second-highest tsunami ever documented, surpassed only by a 1958 event in the same region.
The Hanse Explorer cruise ship had departed the South Sawyer Glacier area just 12 hours before the collapse occurred. Passengers had been photographing and videoing the glacier when the adjacent mountainside suddenly gave way, dumping rock and debris into the fjord. The resulting displacement of water created the towering waves that raced up the narrow fjord's walls.
Glacier Bay, located in southeastern Alaska, sits in a geologically active region where tidewater glaciers and steep mountain terrain create conditions favorable for landslide-generated tsunamis. The 1958 Lituya Bay event, which produced waves reaching approximately 1,722 feet, remains the highest tsunami ever recorded. Tuesday's event came remarkably close to that extreme benchmark.
The timing proved fortunate for those aboard the cruise ship. Had the landslide occurred while the vessel remained in the immediate vicinity, passengers and crew could have faced serious danger. The rapid nature of fjord tsunamis leaves little warning time for evacuation.
Scientists monitoring glacial regions in Alaska continue tracking mountain stability around tidewater glaciers. Climate change and rapid glacial retreat alter the stress distribution in surrounding rock, potentially destabilizing slopes. As glaciers thin and retreat, the weight pressing on adjacent mountains decreases, allowing frozen rock faces to fracture more easily.
The August 2025 event adds to growing evidence that landslide-generated tsunamis pose a persistent hazard in Alaska's coastal fjords. Researchers study these occurrences to improve hazard assessment for both cruise ship operations