The slope gave way at 5:26 a.m. at the head of the fjord, about 50 miles (80 kilometers) southeast of Juneau, where South Sawyer Glacier meets the sea. Nobody was hurt.<\/p>\n\n\n\n
A glacier that stopped holding the slope<\/h2>\n\n\n\n
For years the ice had braced the foot of that mountainside. In the months before the collapse, the glacier pulled back several hundred meters along the base of the slope, the paper says. UAF describes a modest retreat in July and a much faster one from August 2 to 5.<\/p>\n\n\n\n
The rock let go above open water, not ice. Satellite records cited in a University of Washington release<\/a> show the glacier has lost nearly 6 miles (10 kilometers) since the industrial era began, faster after 2000. Co-author Gerard Roe, a UW professor, and UW research scientist Mira Berdahl ran hundreds of climate simulations for the region. They concluded that all of its industrial-era warming is human-caused, and Roe said he is fully confident the retreat comes mainly from that change.<\/p>\n\n\n\n Had the slope still ended on glacier ice, the authors write, the slide would likely have collapsed onto it and made no such wave. It might not have happened at all.<\/p>\n\n\n\n A wedge of bedrock failed first, then shattered into a rock avalanche that dropped about one vertical kilometer (some 3,300 feet). Simulations fed with an October field survey put the breaking wave at around 330 feet (100 meters). It slammed the far shore at more than 150 mph (70 meters per second).<\/p>\n\n\n\n The high-water mark sits on the opposite wall, about a mile (1.6 kilometers) from the slide. Only Lituya Bay, another Alaska inlet, holds a higher one. In 1958 a landslide-generated tsunami<\/a> there reached about 1,740 feet (530 meters).<\/p>\n\n\n\n “The bright landslide scar on the north side of the fjord is striking, as is the ‘bathtub’ ring around the fjord showing the areas where the forest was leveled by the tsunami,” Shugar told NASA Earth Observatory<\/a>.<\/p>\n\n\n\n On Harbor Island, near the fjord’s mouth, kayakers woke to water flowing past their tents. It carried off a kayak and much of their gear. An hour after the slide, the tide gauge in Juneau rose at least 1.3 feet (0.4 meters). That gauge sits some 81 miles (130 kilometers) away.<\/p>\n\n\n\n Distant seismic stations had picked up the hillside for days. Each early signal matched a magnitude 1 to 2 earthquake. They came about an hour apart, and the largest reached magnitude 2.1.<\/p>\n\n\n\n In the last six hours the pace jumped to one signal every 30 to 60 seconds. About two hours before the slide, the bursts merged into a constant vibration. The team reads it as the rock moving steadily along the surface that would soon fail.<\/p>\n\n\n\n “These seismic signals were like the hillside saying, ‘Hey, I’m going to fail,'” Karas\u00f6zen said. She added that such activity is relatively rare before landslides.<\/p>\n\n\n\n Boaters in nearby Endicott Arm reported surging water, and that sent the Earthquake Center looking for a slide. Its new landslide tools then pinpointed the site for responders.<\/p>\n\n\n\n West noted that Alaska already has solid systems for tracking earthquakes and volcanoes. “But this tremendous and dangerous landslide went undetected, and that is a hazard Alaska needs to come to terms with,” he said.<\/p>\n\n\n\n Seismometers around the world recorded the slide. Its long-period waves matched those of a magnitude 5.4 earthquake.<\/p>\n\n\n\n Afterward, the water sloshed from wall to wall in a standing wave called a seiche. It sent out a global signal with a period of about 66 seconds for up to 36 hours. Tsunami simulations and satellite data confirmed the source, the paper says. It is only the second days-long seiche seen this way.<\/p>\n\n\n\n The first came from Greenland in 2023. A rockslide there set off a megatsunami of about 650 feet (200 meters)<\/a> in Dickson Fjord. Its seiche made the planet ring for days<\/a>, a 2024 study in Science reported.<\/p>\n\n\n\n On an average summer day, three cruise ships sail into Tracy Arm, the paper says. An unknown number of smaller boats come too, and some pass within a few kilometers of the slide site.<\/p>\n\n\n\n At 5:26 a.m. that traffic had not yet reached the upper fjord. Roe said the wave would have been “unsurvivable for any ship of any size.” Maximillian Van Wyk de Vries, a Cambridge co-author, puts the lack of deaths down to luck and timing.<\/p>\n\n\n\n Several cruise lines changed their 2026 itineraries to avoid the area. Shugar wants coastal towns and the cruise industry to take the threat seriously. He singles out the West Coast and polar regions where glaciers are thinning.<\/p>\n\n\n\n Nobody knows yet what set the slope off. NASA notes moderate rain beforehand and says both rain and glacier retreat can weaken a slope. The UW release adds that landslide triggers are notoriously hard to pin down.<\/p>\n\n\n\n The warning tremors only turned up in hindsight. Van Wyk de Vries said scientists may be able to flag riskier slopes. Knowing exactly when one will fall is much harder, he added.<\/p>\n\n\n\n Harold Tobin, a UW professor of Earth and space sciences who is not an author, said signals like these could conceivably warn of large slides with enough seismic monitoring. The paper also notes that nobody had assessed the area for slope instability.<\/p>\n\n\n\n The full study appeared online in Science<\/a> on May 6, 2026.<\/p>\n\n\n\n Photo: Cyrus Read\/U.S. Geological Survey<\/p>\n","protected":false},"excerpt":{"rendered":" On August 10, 2025, more than 64 million cubic meters (about 2.3 billion cubic feet) of rock fell into Tracy … <\/p>\nA run-up second only to Lituya Bay<\/h2>\n\n\n\n
![\"Aerial](\"https:\/\/www.ecoticias.com\/en\/wp-content\/uploads\/2026\/10\/tracy-arm-landslide-glacier-terminus.jpg\")
Tremors that started days earlier<\/h2>\n\n\n\n
Water that rocked for a day and a half<\/h2>\n\n\n\n
A morning before the cruise ships arrived<\/h2>\n\n\n\n
What is still uncertain<\/h2>\n\n\n\n