Alaska's Tracy Arm rockslide generates near‑miss tsunami, new study shows

On 10 August 2025 a 60‑million‑cubic‑metre rockslide plunged into Tracy Arm fjord in Alaska, sending a wave that reached 481 metres above sea level – the second‑tallest tsunami ever recorded. The collapse occurred just after 05:00 local time when the fjord was almost empty, sparing tourists and cruise ships from harm.

An international team led by Dan H. Shugar (University of Calgary) reconstructed the event using satellite data, seismic recordings and computer models. They found that the narrow fjord trapped the water, causing a long‑lasting seiche that reverberated for more than a day. The study identified small seismic tremors in the hours before the slide as potential warning signs. Researchers say the retreat of the South Sawyer glacier removed ice support from the mountain wall, and increased meltwater infiltration likely made the slope unstable, linking the disaster to climate‑change‑driven glacial loss.

The scientists propose that monitoring glacier retreat, precipitation and micro‑seismic activity could form an early‑warning system for ships navigating glacial fjords, helping to prevent future catastrophes.