One year ago, on August 10, 2025, a massive landslide entered Tracy Arm in Southeast Alaska and generated a tsunami within the narrow fjord. NOAA says the wave ran up the opposite side of the fjord to an elevation higher than the top floor of One World Trade Center. Cruise ships had left the area only about 12 hours earlier.
NOAA scientists combined satellite imagery, tide gauges, seismic data, eyewitness accounts, and other observations to reconstruct the event. Waves farther down the fjord were smaller, but reportedly traveled through the region at speeds greater than 100 mph. The event is a striking example of how a large rock slope failure can quickly become a regional marine hazard.
There is also a useful monitoring story here. The Alaska Earthquake Center’s seismic network detected the landslide, while NOAA observations helped track the resulting tsunami. As glaciers retreat and steep valley walls lose support, understanding and monitoring landslide-generated tsunamis is becoming increasingly important in Alaska and other glaciated coastal regions.
NOAA and the Alaska Center for Climate Assessment and Preparedness are holding a webinar on August 18 to discuss the Tracy Arm event and Alaska’s broader coastal-landslide threat.
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