A huge landslide in Alaska's Tracy Arm fjord on 10 August 2025 generated the second-largest tsunami ever recorded, with waves reaching 481 metres high. The event displaced 64 million cubic metres of rock and created a 5.4 magnitude seismic signal.
The landslide occurred at 5.26am when a mountainside above the fjord collapsed, sending rock into the water at high speed. This triggered a tsunami that raced down the fjord at least 70 metres per second and produced a seiche wave that continued sloshing for 36 hours. Researchers led by Dan Shugar of the University of Calgary later reconstructed the event using satellite imagery, seismic records, eyewitness reports and computer models.
