What Was the Largest Wave Ever Recorded Without an Earthquake?

The Short Answer

In August 2025, a massive landslide in Alaska’s Tracy Arm fjord triggered the largest wave of its kind ever recorded without an earthquake — pushing water 481 meters (1,578 feet) up the opposite fjord wall, surpassing any comparable event not caused by seismic activity.

What Happened in Tracy Arm Fjord?

In August 2025, at least 64 million cubic meters of rock detached from a mountainside above Tracy Arm, a remote fjord in southeastern Alaska, and plunged into the frigid water below. The impact was catastrophic. The displaced water surged upward with such violence that it stripped trees, soil, and vegetation from the granite wall on the opposite side of the fjord — leaving a pale, ghostly trimline scoured 1,578 feet above sea level. That visible scar remains today as one of the most dramatic geological records ever left on a landscape.

The seismic signal produced by the event registered as the equivalent of a magnitude 5.4 earthquake and was detected by sensors across the globe — despite no actual earthquake occurring. Pure rock, pure gravity, and an ice-free slope did what tectonic forces usually require.

How Does It Compare to the 1958 Lituya Bay Mega-Wave?

The previous record for the tallest wave of this type — known as a displacement wave or impulse wave — was set in Lituya Bay, Alaska, in 1958. That event reached an astonishing 1,720 feet (524 meters) up a hillside, but it was directly triggered by a magnitude 7.8 earthquake that destabilized an enormous rockslide into the bay. The Tracy Arm event in 2025 came within striking distance of that height — reaching 481 meters or approximately 1,578 feet — and it did so without any seismic trigger whatsoever. That distinction makes it the largest non-earthquake-triggered wave of its kind ever recorded.

Why Did This Happen Now?

The answer lies in glacial retreat. For centuries, glacial ice in Tracy Arm acted as a natural buttress, physically supporting the rock slopes above it. As climate change accelerated glacial melt throughout Alaska’s fjord system, that support disappeared. Without ice holding millions of tons of rock in place, the slope became progressively unstable — until gravity won. Scientists who analyzed the event point directly to the retreat of glacial ice as the primary enabling factor. The mountain did not fail suddenly in isolation; it was abandoned by the ice that had held it together.

Are More Events Like This Expected?

Yes — and scientists are vocal about the risk. As glaciers continue retreating across Alaska and beyond, thousands of slopes that were once buttressed by ice are becoming dangerously unstable. Fjords in Alaska, Greenland, Norway, and Patagonia all face similar conditions. Researchers warn that displacement wave events in fjord environments are likely to increase in both frequency and scale as warming continues. The threat is not hypothetical — it is already measurable in the geological record accumulating in real time on the walls of places like Tracy Arm.

What Is a Displacement Wave?

A displacement wave — sometimes called a megatsunami in popular media — is generated when a large mass of rock, ice, or debris rapidly enters a body of water, displacing an enormous volume all at once. Unlike traditional tsunamis driven by seafloor movement, displacement waves are localized and often reach extreme heights in enclosed environments like fjords, where the energy has nowhere to spread. The 2025 Tracy Arm event is a textbook example: a confined fjord, a massive rockfall, and a catastrophic wall of water with nowhere to go but up.