Fortunately, it happened early in the morning, so nobody was around.

The narrow confines of the fjord led to a massive tsunami.

Credit:

Douglas Sacha

The narrow confines of the fjord led to a massive tsunami.

Credit:

Douglas Sacha

At 5:26 am local time on August 10, 2025, a massive wedge of rock with a volume of at least 63.5 million cubic meters detached from a mountain above Alaska’s Tracy Arm fjord. The falling rock plummeted into the deep waters at the terminus of the South Sawyer Glacier and caused an initial 100-meter-high breaking wave that tore across the fjord at speeds exceeding 70 meters a second. When this wave hit the opposite shoreline, it surged up the steep rocks to a height of 481 meters above sea level.

“It was the second highest tsunami ever recorded on Earth,” says Aram Fathian, a researcher at the University of Calgary and co-author of a recent Science study that reconstructed this event in detail.…