ARM · South Korea · Ars Technica
Major landslide assembled a 500-meter-high tsunami in a major tourist area
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◌ Single Source
At 5:26 am local time on August 10, 2025, a massive wedge of rock with a volume of at least 63.5 million cubic meters detached from a mountain above Alaska’s Tracy Arm fjord.
Key facts
- Nearby in No Name Bay, observers on a motor vessel reported a 2-2.5-meter cresting wave coming along the beach from the direction of Tracy Arm, followed by a secondary 1-meter wave
- At 5:26 am local time on August 10, 2025, a massive wedge of rock with a volume of at least 63.5 million cubic meters detached from a mountain above Alaska’s Tracy Arm fjord
- Since 1925, scientists have documented 27 such events with runups exceeding 50 meters
- Between 2013 and 2022 alone, the glacier ice bracing the failure site thinned by 100 to 130 meters
Summary
“It was the second highest tsunami ever recorded on Earth,” says Aram Fathian, a researcher at the University of Calgary and co-author of a recent Science study that reconstructed this event in detail. Earthquake-generated tsunamis usually reach runup heights of a few tens of meters when they strike land. Since 1925, scientists have documented 27 such events with runups exceeding 50 meters. The source of the 2025 Tracy Arm tsunami was a steep rock wedge on the northern side of the fjord. “We studied the event from several aspects, from different lenses,” Fathian says.