Researchers say that retreating glaciers, heavy rainfall, and small ground tremors served as warning signs before a 2025 landslide pushed a tsunami 1,580 feet up the sides of Tracy Arm fjord in Alaska.
Their study suggests methods to track similar hazards in the future. At 5:26 a.m. on August 10, over 64 million cubic meters of rock fell near South Sawyer Glacier into the fjord. This rockfall triggered a wave with the second-highest recorded run-up height, trailing only the 1958 tsunami in Lituya Bay.
The rushing water stripped plant life off the facing slope and moved through the fjord. Researchers calculate that the first breaking wave reached a height of about 100 meters. An earthquake did not cause the collapse, but scientists discovered that minor tremors, reaching up to magnitude 2.1, happened more frequently in the days leading up to the slide.
They found this trend after the event took place, along with proof of glacier retreat and heavy rains. Because they found these patterns after the fact, the signals serve as clues rather than a tested early-warning system. The rockslide occurred before boats arrived in the upper fjord, and nobody was reported injured or killed.
However, cruise ships and other boats travel to this area on a regular basis. The researchers note that tracking tremors, weather patterns, and glaciers together could help warn people when danger increases. They add that more study is required to pinpoint exactly where and when these slope collapses might happen.