Massive Alaska Landslide Unleashed 481-Meter Tsunami, Highlighting Hidden Danger in Glacial Fjords

Breaking: Second-Highest Tsunami Ever Recorded Strikes Alaska Fjord

At 5:26 a.m. local time on August 10, 2025, a colossal rock wedge—at least 63.5 million cubic meters—broke free from a mountain towering over Alaska's Tracy Arm fjord. The debris crashed into the water at the terminus of South Sawyer Glacier, generating a wave that initially surged to 100 meters high and raced across the fjord at over 70 meters per second. When it slammed into the opposite shore, the water climbed 481 meters above sea level.

“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 study in Science that details the event. “But until now, almost nobody heard about it because it was a near-miss event,” he adds. No injuries or fatalities were reported, largely because the collapse occurred early in the morning when few people were near the water. Still, experts warn that future landslides could prove far deadlier.

The Scale of the Event

The 481-meter runup exceeds that of the 1958 Lituya Bay megatsunami—the highest ever recorded at 530 meters—but dwarfs typical earthquake-generated tsunamis, which rarely exceed a few tens of meters. Landslide tsunamis in confined fjords create extreme waves because millions of tons of rock suddenly displace water across varying depths. Since 1925, scientists have documented 27 such events with runups greater than 50 meters.

“This event underscores how vulnerable steep glacial valleys are to catastrophic failures,” says Fathian. “Climate change is destabilizing mountain slopes, and we need better monitoring systems in popular tourist areas like Tracy Arm.”

Background: Landslide Megatsunamis on the Rise

Earthquake-generated tsunamis typically reach runup heights of only a few tens of meters when they strike land. But landslide tsunamis, while more localized, are far more violent. When rock plunges into a narrow stretch of water, the direct displacement and abrupt depth changes produce towering waves. The 1958 Lituya Bay event in Alaska remains the highest recorded, with a 530-meter runup. The Tracy Arm wave now ranks second.

Tourism in Tracy Arm fjord—a popular cruise ship destination—makes the near-miss particularly concerning. The region attracts thousands of visitors each summer, and the landslide site lies close to frequented waterways.

What This Means

The Tracy Arm tsunami is a stark warning: as glaciers retreat and permafrost thaws, previously stable mountain slopes become prone to massive failure. Tourists and local communities near glacial fjords may face increasing risk. “We might not be so lucky next time,” warns Fathian. “A similar event during peak tourist hours could be catastrophic.”

Researchers are urging authorities to install real-time monitoring systems—including seismometers, radar, and water-level sensors—in high-risk fjords. For now, the Tracy Arm event serves as both a scientific benchmark and a call to action for disaster preparedness in a warming world.

— Reporting by [Your News Outlet]