64 Million Cubic Metres of Rock Slide into Alaska’s Tracy Arm Fjord, Generating 481-Metre Wave

A landslide of 64 million cubic metres of rock entered Tracy Arm Fjord in southeast Alaska on 10 August 2025, generating a megatsunami that reached 481 metres in height. The wave ranked as the second-largest ever recorded, exceeded only by the 1958 Lituya Bay tsunami that topped 530 metres. 4 magnitude seismic event.

M. It moved down the fjord at a minimum speed of 70 metres per second and produced a seiche that continued sloshing inside the fjord for 36 hours. m.

To find their campsite flooded and their gear carried off by the wave. Dr Bretwood Higman, an Alaskan geologist, reached the site several weeks later. He documented broken trees scattered across the mountainside and thrown into the water, plus large areas of rock stripped bare of soil and vegetation.

"It was a close call," Higman said. "We know that there were people that were very nearly in the wrong place. " Researchers combined fieldwork, seismic records, satellite imagery, eyewitness reports and computer models to reconstruct the sequence.

The South Sawyer Glacier feeding the fjord retreated more than 10 kilometres and thinned substantially through the 20th century and into recent decades. " "If a ship were in the upper part of the fjord, I can’t see how it would survive," he said. Several cruise operators have announced they will cease sending vessels into Tracy Arm Fjord due to safety concerns.