A massive megatsunami struck Tracy Arm Fjord in southeast Alaska on August 10, 2025, reaching a height of 481 meters (1,578 feet)—the second-largest ever recorded. The wave, triggered by a 64-million-cubic-meter landslide, was caused by the rapid retreat of a glacier, which destabilized the mountain above the fjord. Researchers from UCL and Alaskan geologists analyzed the event, noting that the tsunami occurred in the early morning, avoiding direct impact on tourist cruise ships that frequent the area.
Part 1: Immediate Action & Core Facts
- A 481-meter megatsunami struck Tracy Arm Fjord on August 10, 2025, ranking as the second-largest ever recorded.
- The wave was triggered by a 64-million-cubic-meter landslide, caused by glacier retreat linked to climate change.
Part 2: Deeper Dive & Context
The Landslide and Tsunami Mechanics
The landslide, equivalent to 24 Great Pyramids of Giza, plunged into the fjord in under a minute, displacing enough water to generate the massive wave. Researchers used satellite data, seismometers, and eyewitness accounts to reconstruct the event. The glacier had retreated 500 meters in weeks, leaving the rock unsupported.
Tourism and Safety Concerns
Tracy Arm Fjord is a popular cruise ship destination, and the tsunami’s timing—around 5:30 AM—prevented direct casualties. However, Dr. Bretwood Higman, an Alaskan geologist, warned that future events could be less fortunate. "We know there were people who were very nearly in the wrong place," he said. "I’m quite terrified that we’re not going to be so lucky in the future."
Megatsunamis vs. Traditional Tsunamis
Megatsunamis, like this one, are localized and dissipate quickly, unlike oceanic tsunamis (e.g., the 2011 Japan tsunami), which travel long distances and cause widespread destruction. The largest recorded megatsunami occurred in Lituya Bay, Alaska, in 1958, reaching 524 meters (1,720 feet).
Climate Change and Future Risks
Researchers emphasize that retreating glaciers in fjords are increasing the risk of such events. "Fjords with retreating glaciers have seen a sharp increase in tourism," said Dr. Stephen Hicks of UCL. "More people are visiting these beautiful places, but they are at the forefront of climate change impacts and so can be dangerous." The area had not been previously identified as hazardous, highlighting the unpredictability of such events.