Carved over millennia by the pressure and motion of glacial ice, the valley walls cradling the Tracy Arm fjord in southeast Alaska continue to be reshaped. In summer 2025, following the rapid retreat of South Sawyer Glacier, a large landslide sent rock careening into the fjord, altering the wider landscape in a matter of minutes.
The slide culminated on the morning of August 10, 2025, when at least 64 million cubic meters of rock slid downslope. Material entering the fjord induced a tsunami that stripped trees and other vegetation from the opposing fjord wall up to 1,578 feet (481 meters) above sea level. While this peak was the highest “runup” reached by the tsunami, shores and islands down the fjord also saw substantial destruction.
NASA-USGS Landsat satellites captured these images on July 26 (left) and August 19 (right), before and after the event, respectively. “The bright landslide scar on the north side of the fjord is striking, as is the ‘bathtub’ ring around the fjord showing the areas where the forest was leveled by the tsunami,” said Dan Shugar, a geomorphologist at the University of Calgary.
Note that Sawyer Island, about 6 miles (9 kilometers) from the landslide, also turned from green to brown. Only a few trees …