For decades, we have viewed climate change as a slow-motion problem: gradually rising seas, shifting weather patterns, melting polar ice, and the opening of new maritime routes. The Arctic and the world’s high-altitude peaks were treated as remote, frozen boundaries governed by their own distinct, isolated rules.
That siloed perspective is shattering. Modern climate disruption is no longer merely disrupting frozen land, sea and ice scapes; it is also destabilizing the solid Earth. As glaciers retreat and permafrost thaws, the geological foundations supporting enormous mountain slopes can weaken, unleashing catastrophic collapses whose consequences extend far beyond their points of origin. These events introduce a disturbing new dimension to global security: the possibility that warming temperatures can transform frozen geography into a kinetic force resembling the destructive power associated with the Cold War’s ultimate, “absolute” weapon.
Three extraordinary collapses across the cryosphere from the Arctic to the Himalayan “third pole” illuminate this emerging threat: the September 2023 mega-tsunami at Dickson Fjord, Greenland; the August 2025 mega-tsunami at Tracy Arm, Alaska; and the August 2026 mountain collapse and devastating downstream flood in the Himalayas near Langtang Lirung, Nepal. Together, these three towers of stone and ice recall the destruction of the World Trade Center’s Twin Towers on September 11, 2001—an event that transformed the global security imagination a quarter-century ago.
The comparison is not that these disasters share the same causes. The Twin Towers were destroyed by a deliberate terrorist attack; the geological catastrophes arose from natural processes whose risks are being reshaped by a warming climate. Rather, the parallel lies in the sudden failure of massive structures, the conversion of gravitational potential energy into destructive kinetic force, and the capacity of a localized collapse to generate consequences that overwhelm established expectations.
The Physics of Mountain Failure: From Ice-Glue to Kinetic Waves
For millennia, glaciers and frozen ground have helped stabilize steep mountain slopes. Ice occupying fractures in bedrock, together with glaciers buttressing mountainsides, can contribute to the structural integrity of high-altitude and polar landscapes. As warming changes these conditions, previously stable slopes may become increasingly vulnerable to failure.
The resulting danger is not limited to falling rocks or retreating glaciers. When enormous masses of rock and ice plunge into confined fjords, they can displace extraordinary volumes of water, generating mega-tsunamis. When similar collapses strike steep river valleys, the debris can mix with water and snow to create fast-moving avalanches and destructive floods. In both settings, a mountain can become a source of sudden, cascading hazards that conventional monitoring systems may not anticipate.
Dickson Fjord, Greenland (2023): The Mega-Tsunami That Made the Earth Ring
On September 16, 2023, a mountainside overlooking remote Dickson Fjord in East Greenland catastrophically collapsed. Approximately 25 million cubic meters of rock and ice plunged into the narrow fjord, generating an initial mega-tsunami estimated at around 200 meters high.
The consequences did not end with the initial wave. The displaced water became trapped within the confined fjord, sloshing back and forth in a prolonged standing wave known as a seiche. Its oscillations generated an unusual, low-frequency seismic signal detected around the world. Scientists subsequently established that the phenomenon continued for nine days, making this event remarkable not only for its destructive potential but also for the planetary reach of its geophysical signature.
The episode revealed an unsettling truth: a catastrophic mountain collapse can occur in a remote landscape, escape immediate human observation, and nevertheless register across the planet. Its remoteness limited the human toll, but it did not limit the event’s scientific significance.
The Dickson Fjord tsunami also exposed a weakness in conventional early-warning systems. Monitoring frameworks designed primarily for earthquakes, conventional landslides, and glacial lake outburst floods may overlook the possibility that a mountainside itself could fail, displace a fjord’s water, and generate a sustained seismic signal. In this case, the unusual signal helped scientists discover the event after the fact. The challenge is to move from retrospective discovery toward anticipatory risk management.
Tracy Arm, Alaska (2025): A Near Miss in a Tourist Corridor
Two years later, an even larger collapse occurred at Tracy Arm, Alaska, near South Sawyer Glacier, approximately 45 miles south of Juneau. On August 10, 2025, an estimated 64 million cubic meters of rock and associated debris entered the fjord, generating a massive tsunami.
The wave stripped vegetation from the opposing fjord wall to a height of approximately 481 meters above sea level—the second-highest recorded tsunami runup. The event also produced globally recorded seismic waves equivalent to a magnitude 5.4 earthquake. A prolonged seiche continued within the fjord for 36 hours after the initial impact.
Yet Tracy Arm differed critically from Dickson Fjord. Although both are dramatic glacial landscapes, Tracy Arm attracts substantial seasonal tourism, including cruise ships, expedition vessels, recreational boats, and kayakers. Its beauty and accessibility place people within reach of a hazard capable of transforming the fjord into a deadly trap.
The collapse occurred at approximately 5:26 a.m., before most tourist traffic had entered the fjord. No deaths or injuries were reported. That outcome was fortunate, but it should not be mistaken for evidence of low risk. Had the collapse occurred later in the day, with vessels and visitors inside the affected waters, the consequences could have been far more severe. (Indeed, just 12 hours earlier, passengers aboard the luxury expedition vessel Hanse Explorer stopped to take photos directly in front of South Sawyer Glacier just before the ship turned around to exit the fjord.)
Tracy Arm therefore provides the crucial link between Greenland and the Himalayas: Dickson Fjord demonstrated the extraordinary power of a collapse in an almost uninhabited wilderness. Tracy Arm demonstrated how a similar event can threaten a heavily visited landscape, even without a permanent population in the immediate hazard zone. The difference was not simply geological; it was a matter of human exposure and timing.
Langtang Lirung, Nepal (2026): A Collapsing Tower Becomes an Inland Tsunami
On August 26, 2026, a catastrophic ice-and-rock collapse near Langtang Lirung, along the Nepal–Tibet border, triggered a devastating downstream cascade. A massive hanging glacier and adjacent bedrock failed, sending enormous quantities of debris into a steep alpine valley.
Rather than entering a confined marine fjord, the collapsing mass plunged into a river system. Rock, ice, water, and sediment combined into a fast-moving debris flow that surged downstream along the Trishuli River corridor, destroying infrastructure and communities. The disaster affected a strategically important border region, including the Gyirong–Rasuwagadhi trade corridor, and created additional hazards as water and debris accumulated in unstable barriers and temporary lakes.
The consequences were dramatically different from those in Greenland and Alaska. The Himalayan collapse struck a populated corridor connected to settlements, transportation networks, trade infrastructure, and communities dependent on vulnerable mountain rivers. The disaster resulted in mass casualties, with the full toll complicated by the large number of people reported missing.
This was not simply a conventional flash flood, nor the familiar scenario of a glacial lake suddenly bursting through a moraine dam. It was a cascading geological failure in which a collapsing mountain mass generated a destructive torrent downstream.
The distinction matters. Early-warning systems that focus on known glacial lakes may not adequately account for unstable bedrock, hanging glaciers, or the possibility that a sudden landslide will create its own flood-generating conditions. In a steep Himalayan valley, the interval between the initial collapse and downstream destruction may be measured in minutes rather than hours.
The Himalayas also introduce a geopolitical dimension. Rivers, trade routes, and emergency-response requirements cross borders, while political tensions can complicate the rapid exchange of information. When a natural disaster strikes before its cause is understood, uncertainty itself can become a security risk.
Three Collapses, Three Human Geographies
Taken together, the cases reveal a continuum of danger.
Dickson Fjord was a spectacular geological event in a remote wilderness. Its initial tsunami and nine-day seismic signature demonstrated that an isolated mountain collapse can produce planetary-scale observations without a comparable human catastrophe.
Tracy Arm was a near miss in a landscape frequented by tourists and recreational users. The extraordinary tsunami runup demonstrated that a remote-looking fjord can become a mass-casualty hazard when human activity overlaps with an unstable mountainside.
Langtang Lirung demonstrated the devastating potential of the same broad family of hazards when a collapsing mountain feeds directly into an inhabited river corridor. Here, the effects extended into public safety, transport, trade, emergency response, and transboundary relations.
These differences caution against treating all geological collapses as interchangeable. Their consequences depend on the mass and composition of the material released, the geometry of the landscape, the presence of water, the speed and direction of the resulting flow, and the number of people and critical facilities in its path.
Nevertheless, the three cases share a troubling feature: each reveals how rapidly a geological process can escape the boundaries within which conventional institutions expect to manage risk.
