Overview
- The peer‑reviewed analysis published Wednesday in Science confirms the Aug. 10, 2025 Tracy Arm landslide drove a localized tsunami that ran up about 481 meters.
- Roughly 64 million cubic meters of rock fell in about a minute, generating long‑period seismic waves equal to a magnitude 5.4 earthquake that were detected worldwide and setting off a long seiche, or sloshing, in the fjord.
- The wave struck around 5:30 a.m., so no vessels were in the upper fjord and no injuries were reported in a corridor that typically sees heavy cruise and tour traffic later in the day.
- Seismic records show days of small quakes followed by a pre‑dawn shift to continuous tremor before the collapse, a pattern researchers say could support tiered alerts if denser sensors and rapid messaging are in place.
- The study links the failure to loss of ice support as South Sawyer Glacier thinned and retreated, which can debuttress steep valley walls in narrow fjords and raise the chance of landslide‑driven tsunamis.