Note: Single-source report; awaiting corroboration.
On August 10, 2025, a massive landslide struck the north side of Tracy Arm fjord in southeast Alaska. Over 64 million cubic meters of rock fell into the fjord after the rapid retreat of the South Sawyer Glacier, reshaping the landscape within minutes. The landslide generated a tsunami that stripped trees and vegetation from the opposite fjord wall, reaching heights up to 1,578 feet (481 meters) above sea level. Islands and shores along the fjord suffered substantial damage, with Sawyer Island's vegetation turning brown and few trees remaining at higher elevations.
NASA-USGS Landsat satellite images before and after the event show a distinct landslide scar and a 'bathtub ring' where the tsunami leveled forest. Researchers used satellite, airborne, and ground observations, along with eyewitness accounts and simulations, to analyze the event. Their findings were published in the journal Science in May 2026.
The tsunami's waters created a seiche that lasted more than 24 hours. Both the landslide and the seiche generated seismic signals detected worldwide. The landslide impact was equivalent to a magnitude 5.4 earthquake.
Satellite imagery also revealed the notable retreat of the South Sawyer Glacier, with a large portion of the glacier’s terminus breaking off due to the landslide, resulting in numerous icebergs in the fjord. The exact cause of the landslide remains uncertain, although moderate rainfall and rapid glacial retreat likely contributed to destabilization.
This event highlights the dynamic, rapidly changing nature of glacial fjord landscapes shaped by geological and climatic forces.