Carved over millennia by glacial ice, the Tracy Arm fjord in southeast Alaska recently got a much quicker makeover - courtesy of a landslide and tsunami that did in minutes what nature usually takes ages to accomplish.
On the morning of August 10, 2025, at least 64 million cubic meters of rock slid into the fjord after the rapid retreat of South Sawyer Glacier, triggering a tsunami that stripped vegetation up to 1,578 feet (481 meters) above sea level on the opposite wall. Sawyer Island, about 6 miles (9 kilometers) away, turned from green to brown, with only a few trees clinging to higher ground.
NASA-USGS Landsat satellites captured the before and after on July 26 and August 19, 2025. Dan Shugar, a geomorphologist at the University of Calgary, described the "bathtub ring" of leveled forest around the fjord - proof that even nature enjoys a good scrub now and then.
The landslide and subsequent "seiche" (water sloshing for over a day) produced seismic signals equivalent to a magnitude 5.4 earthquake, felt globally. The slide also broke off a chunk of South Sawyer Glacier, creating a slurry of icebergs.
Researchers, led by Shugar, published their analysis in the journal Science on May 6, 2026, combining satellite, airborne, and ground data. While no one was injured, kayakers on Harbor Island lost their gear, and passengers on a small cruise vessel in neighboring Endicott Arm reported wild water level swings.
Brentwood Higman of Ground Truth Alaska noted that visible glacier retreat in satellite images could serve as a warning sign for future landslides and tsunamis. Because nothing says "vacation destination" like a potential landscape-reorganizing wave.