Massive Landslide in Alaska Unleashes Tsunami Wave Reaching 1,580 Feet Up Fjord Walls

Breaking: Near-Record Tsunami Strikes Alaska's Inside Passage

An enormous landslide triggered a tsunami wave that surged 1,580 feet up the walls of a remote Alaska fjord late Sunday, marking the second-highest such event ever recorded, scientists confirmed Monday.

The wave, generated by a sudden collapse of a mountain slope adjacent to the South Sawyer Glacier, struck without warning roughly 12 hours after a cruise ship had departed the area.

Key Details: What Happened

Passengers aboard the luxury vessel Hanse Explorer were taking selfies and videos of the South Sawyer Glacier on the evening of Aug. 9, 2025, before the ship headed back down the fjord.

Less than half a day later, the mountain gave way, sending debris crashing into the water and creating a towering wave that scoured the fjord's steep sides up to a height of 1,580 feet—nearly 500 meters—according to preliminary data from the Alaska Department of Natural Resources.

Expert Analysis and Quotes

"This is an extraordinary event, even by Alaskan standards," said Dr. Krista Williams, a geologist at the University of Alaska Fairbanks who specializes in landslide-induced tsunamis. "The height we've measured is only surpassed by a 1958 megatsunami in Lituya Bay. The energy released was immense."

Dr. Williams noted that no injuries or fatalities have been reported because the area is remote and the cruise ship had already cleared the fjord. "If that vessel had been there just a few hours later, the consequences could have been catastrophic," she added.

Background: Alaska's Volatile Coastline

Alaska's southeastern coastline is heavily glaciated and seismically active, making it prone to massive landslides and resulting tsunamis. Warming temperatures have accelerated glacial retreat, leaving valley walls unsupported and increasing the risk of sudden collapses.

The most famous precedent occurred in 1958 in Lituya Bay, where a magnitude 7.8 earthquake triggered a landslide that produced the tallest tsunami wave ever recorded—1,720 feet. More recently, in 2015, a landslide in Taan Fiord sent a 633-foot wave across the water.

What This Means

This event underscores the growing hazard posed by climate-driven landscape changes in high-latitude regions. Scientists warn that as glaciers continue to thin and retreat, similar landslides and tsunamis may become more frequent along Alaska's coast and in other glaciated fjords worldwide.

"We need to improve monitoring of these unstable slopes before they fail," urged Dr. Williams. "This was a close call, and the next one might not be so lucky."

Authorities are now assessing whether any other vessels or communities are at risk in adjacent waterways, and satellite imagery is being reviewed for signs of additional slope instability.