On the evening of August 9, 2025, passengers aboard the expedition vessel Hanse Explorer stood on the outer decks, framing their final shots and capturing smartphone videos of the stunning South Sawyer Glacier in Alaska. With their cameras full of ice-choked blue waters and towering walls of jagged stone, the ship weighed anchor and began its journey back down the remote fjord.

Twelve hours later, a massive section of the adjacent mountain gave way without warning, plunging millions of tons of rock and debris directly into the fjord. The catastrophic impact triggered the second-highest tsunami ever recorded in human history, unleashing forces that fundamentally reshaped the surrounding landscape and underscored a terrifying, rapidly evolving hazard across the circumpolar north.

Researchers at the Alaska Earthquake Center, including the Alaska state seismologist, have spent the months following the event studying the mechanics of the disaster alongside colleagues. In a comprehensive new study published in the scientific journal Science, the researchers detail how the massive landslide displaced a wall of water and debris 1,580 feet—or 481 meters—up the opposing side of the fjord. That height exceeds the top floor of the famed Taipei 101 skyscraper.

The colossal wave continued its destructive path down Tracy Arm, moving with such unimaginable force that it stripped the fjord’s steep walls completely bare down to solid rock, obliterating vegetation and altering the topography of the popular tourist destination.

The timing of the event was a matter of sheer fortune. The disaster struck just after five o’clock in the morning on a dreary, overcast day, and no cruise ships or commercial vessels were operating nearby. Yet, the psychological and practical ripple effects were immediate. In the months following the disaster, several major cruise lines altered their itineraries, quietly deciding to avoid Tracy Arm altogether. However, seismologists and geologists emphasize that the underlying environmental conditions that triggered this catastrophic collapse are not unique to this single fjord in southeastern Alaska.

Landslides have long been a common occurrence in the rugged coastal mountains of Alaska, where rapid tectonic uplift and long-term ice loss intersect directly with heavy precipitation and the relentless erosive forces of moving glaciers. But in recent years, scientists have noticed a curious and deeply concerning pattern emerging globally: multiple major landslides have occurred precisely at the terminus of retreating glaciers.

Although the complex physical mechanics behind the phenomenon are still poorly understood by the scientific community, these steep mountain slopes appear to become critically unstable as the supporting glaciers melt and disappear. When a mountain slope fails and hits the water, the immense momentum of millions of tons of rock is instantly transferred into tsunami waves, transforming a terrestrial collapse into a maritime hazard.

This exact geological phenomenon is playing out across the globe, stretching from the glacier-carved coastlines of Alaska to the remote fjords of Greenland and Norway. In some instances, these events have carried deadly human consequences. Across the entire Arctic, national authorities and local communities are struggling to come to terms with this growing, poorly understood hazard. The available options are stark and unappealing: either avoid vast, economically vital swaths of coastline entirely, or learn to live with an unpredictable risk. Researchers argue that an obvious solution lies in the deployment of targeted alert systems, but such measures are only viable if scientists possess a significantly better understanding of where and when these landslides are most likely to strike.

Signs That a Landslide Might Be Coming

The catastrophic collapse at Tracy Arm serves as a powerful case study for researchers attempting to decode the warning signs of mountain slope failures.

The landslide took place in August, a month when warm ocean waters and heavier precipitation favor both rapid glacier retreat and slope failure. In the two months leading up to the disaster, the glacier situated directly below the landslide zone had experienced intense calving—a process where massive chunks of ice break off and plunge into the water—and had retreated by more than a third of a mile. At the same time, heavy rains had been soaking the region. When heavy rain falls on steep mountain slopes, water infiltrates deep fractures within the rock, pushing the geological structures closer to structural failure by exponentially increasing the water pressure inside internal cracks.

Most provocative to seismologists are the thousands of small, low-magnitude seismic tremors that emanated from the immediate area of the slide in the days prior to the final collapse of the mountainside.

Researchers believe that this specific combination of environmental and seismic signs would have been more than sufficient to issue progressive alerts to any commercial ships in the vicinity, as well as to homes and businesses vulnerable to tsunamis, at least a day prior to the final failure—had an appropriate monitoring program been in place.

Escalating alert systems are already widely utilized across modern society for everything from terrorism threats and nuclear plant safety to avalanches and volcanic unrest. While such systems do not completely eliminate underlying risks, they make it significantly easier for human populations to safely coexist with natural hazards.

For example, although people still occasionally fall victim to winter avalanches, formal alert systems and public forecasts have played an essential role in making winter backcountry travel safer and more manageable for millions of people. The catastrophic collapse at Tracy Arm demonstrates what could similarly be possible for tracking and responding to sudden mountain landslides.

What an Alert System Could Look Like

Scientists suggest that the combination of unseasonable weather and rapid glacier retreat in early August 2025 would likely have been sufficient to issue an initial advisory notifying the public that the geological hazard was temporarily elevated across a general region. Translated to a standard risk scale, this would mirror a yellow alert.

In the hours immediately preceding the landslide, the exponential increase in local seismic events and the telltale transition to what geologists call seismic tremor—a continuous, low-frequency hum of seismic energy—provided enough data to communicate a highly time-sensitive warning for a specific geographic region.

These crucial observations, which were recorded as a byproduct of standard regional earthquake monitoring networks, warranted an orange alert noting immediate concern. In hindsight, researchers argue these signs were arguably sufficient to recommend keeping all recreational boats and commercial ships completely out of the fjord.

Recent scientific research over the past few years has demonstrated that once a large landslide has actually begun, it is entirely possible to detect and measure the event within a couple of minutes. During this narrow window of time, seismic waves propagating through the surrounding bedrock can indicate the rough physical size of the landslide and confirm whether it occurred near open water, setting the stage for a potential tsunami.

A modern monitoring program capable of quickly communicating these findings would be able to issue a red alert, signaling a major geological event currently in progress.

While the National Oceanic and Atmospheric Administration’s established tsunami warning program has spent decades fine-tuning the rapid dissemination of emergency messages, a dedicated local warning system would have offered little physical help to ships caught in the immediate impact zone. However, it could have provided perhaps ten precious minutes of warning for residents and visitors who had to ride out the harrowing tsunami further down the channel.

Currently, there is no comprehensive landslide monitoring system operating at this specific scale within the United States. Constructing such a network will require unprecedented cooperation across state and federal agencies, alongside strengthened geophysical monitoring and communication frameworks. Even then, experts caution that such a system will never be entirely fail-proof.

Understanding Risk, Not Removing It

Emergency alert systems do not remove natural risks entirely, but they represent a vastly superior option compared to having no warning at all. Over time, these systems also build cultural awareness as local communities and seasonal visitors grow accustomed to factoring these geological hazards into their daily planning.

Many of the most alluring, visually stunning places on Earth inherently come with significant natural hazards, and the fjords of the Arctic are prime examples. The very same geological and environmental processes that create these terrifying hazards—glacier retreat, steep terrain, and dynamic, shifting geology—are precisely what make these landscapes so compelling to travelers. The unique mix of towering glaciers, ice-choked waters, and sheer mountain walls is what draws people to these remote frontiers, and visitors will undoubtedly continue to travel there to experience them.

The central question facing policymakers, tourism operators, and scientists is not whether these wild places should be avoided altogether, but rather how to help people make more informed, risk-aware decisions. Researchers maintain that stronger geophysical and meteorological monitoring, coupled with innovative research and reliable communication channels, represents the critical first step toward achieving that balance.

On August 9, unsuspecting visitors passed safely through a magnificent landscape that was already on the very cusp of geological failure. A functional, real-time alert system might have provided tour operators and individuals in the area with the vital information they needed to make informed choices and avoid being caught entirely by surprise.