In the early morning of August 10, 2025, a remote fjord in southeastern Alaska witnessed one of the most extreme geological events of the decade. A massive chunk of mountain collapsed into the Tracy Arm fjord, unleashing a wave of astonishing scale. Few were around to witness the catastrophe unfold—but the data and debris tell a story of unimaginable force.
While the wave itself was brief, its echoes—scientific and environmental—continue to ripple across the region. Now, detailed analysis from the US Geological Survey (USGS) reveals just how powerful, and how dangerous, this event truly was.
A Landslide Measured In Millions: What Triggered The Giant Wave
At 5:30 am local time, more than 100 million cubic meters of rock and earth suddenly detached from a steep mountainside above South Sawyer Glacier, crashing into the narrow confines of Tracy Arm fjord. The resulting displacement of water created a megatsunami that reached an estimated run-up height of 500 meters—higher than all but one of New York City’s tallest buildings.
According to state seismologist Michael West, the impact zone was beyond catastrophic.
“I feel pretty comfortable saying that anything that was actually at the terminus of this glacier, right at the base of this landslide, would have been absolutely obliterated,” West said in an interview with Alaska Public Media. “I cannot see any way around that.”
Sensors more than 1,000 kilometers away detected the seismic shock, confirming the sheer energy released during the collapse. Satellite data, GPS surveys, and helicopter-mounted altimeters helped reconstruct the wave’s height and impact zones. But beyond the numbers, the real surprise was the silence that followed. “Fortunately, we do not have reports of folks who were really close to the slide, say, you know, within a mile or something, but I can only imagine that would have been an extremely violent affair,” West added.
The Tsunami Nobody Expected: Clues From The Water
Far from the landslide’s origin point, signs of the disaster first appeared subtly—and then unmistakably. Near the entrance of Fords Terror fjord, Christine Smith, a cruise ship operator, noticed a strange behavior in the tides. “[W]e started seeing the water rising again on what should have been a falling tide,” Smith told Alaska Public Media. “We knew something was really different, and wrong.”
This anomaly prompted Smith to contact a seismologist, eventually leading to a broader investigation involving the Alaska Earthquake Center and USGS scientists. The wave’s massive run-up on the opposite hillside revealed the true scale of the event. While no fatalities were reported, some kayakers camping near the mouth of the fjord lost their gear, underscoring how close this came to a human tragedy.
As data poured in, scientists identified the presence of a seiche—a type of standing wave that oscillates within enclosed bodies of water. This particular seiche lasted 35 hours, creating rhythmic sloshing back and forth every minute, a testament to how long the fjord remained in hydrodynamic turmoil after the initial wave.
A Landscape Rewritten: The Science Behind The Aftermath
The Tracy Arm event is now part of an ongoing study by the USGS Landslide Hazards Program, which is investigating both the geophysical triggers and long-term risks associated with such mountainous terrain. Their findings warn that the region remains highly unstable, especially near the exposed landslide scar left behind.
“Steep, mountainous landslide areas are inherently unstable and will continue to change for years following an initial landslide,” the USGS reported in their official briefing. “Continued rockfall and smaller-scale landslide events from the exposed landslide scar are expected and could impact the water, potentially causing future local tsunami. As such, this area remains hazardous.”
What makes the Tracy Arm landslide particularly significant is that it did not result from an earthquake. The event appears to have been gravity-driven, a consequence of glacial retreat, thawing permafrost, and steep, saturated slopes. In this way, the incident serves as a stark warning of how climate-related factors are interacting with Earth’s most fragile topographies.
A Wake-Up Call For Fjord Monitoring Around The World
Though it wasn’t the tallest tsunami ever recorded—1958’s Lituya Bay megatsunami still holds that record—the Tracy Arm tsunami ranks among the highest and most forceful of the 21st century. Yet it remains little-known to the general public, largely due to its remote location and lack of immediate casualties.
What it highlights, however, is a broader vulnerability. Dozens of similar fjords around the world—from Greenland to Norway—may harbor the same potential for sudden, high-impact waves triggered by landslides. Monitoring systems in these regions are often sparse, and events like Tracy Arm show just how narrow the margin is between geological instability and disaster.
Future scientific efforts will likely focus on real-time monitoring, AI-driven landslide modeling, and community preparedness in nearby settlements and cruise routes. For now, Tracy Arm stands as both a geological marvel and a silent reminder of the power that remains hidden in Earth’s remote corners.
