An overhead view of the August 2025 landslide and resulting tsunami near South Sawyer Glacier in Alaska. BBC
A massive megatsunami recently swept through Tracy Arm Fjord in Southeast Alaska, creating a wave nearly 500 meters tall. The destructive force of the wave was caused by a landslide that sent an astonishing 64 million cubic meters of rock into the fjord. The event, which occurred last summer, went largely unreported at the time but has now drawn attention due to its magnitude and the dangers posed by melting glaciers in the region.
Dr. Bretwood Higman, an Alaskan geologist who visited the scene, called it a "close call" and expressed concerns that future events could be even more dangerous. "I'm quite terrified that we're not going to be so lucky in the future," he said. Researchers emphasize that the timing of the incident, which took place in the early hours of the morning, prevented cruise ships from being caught up in the disaster. Had the event occurred during the day, the consequences could have been far worse.
Understanding Megatsunamis and Their Cause
Megatsunamis are extremely large waves triggered by landslides caused by either earthquakes or loose rock. Unlike regular tsunamis, which are usually the result of underwater earthquakes and can travel across vast ocean distances, megatsunamis are localized and dissipate quickly. However, their destructive power is immense, as seen in this incident where a significant amount of rock crashed into the water in under a minute, creating a towering wave.
The 1958 megatsunami in Lituya Bay, Alaska, remains the largest ever recorded, reaching heights of over 500 meters. The recent wave in Tracy Arm, at 482 meters, is the second tallest ever recorded, highlighting the extreme nature of these rare but highly destructive events.
Glacier Melt Makes Alaska Vulnerable
New research published in Science suggests that the melting glaciers in Alaska, a result of climate change, are making the risk of megatsunamis much worse. As glaciers retreat, they expose the cliffs below, which were previously held in place by the ice. When the ice melts, these cliffs become unstable and can collapse, sending huge amounts of rock into the fjords, triggering megatsunamis.
Dr. Stephen Hicks from University College London explained that the retreating glaciers are "allowing that rock material to suddenly collapse into the fjord." This process, combined with frequent earthquakes in the region, makes Alaska especially vulnerable to megatsunamis.
Safety Risks for Tourists and Local Communities
The scientists are warning that the frequency of megatsunamis could be increasing, possibly by a factor of 10 compared to just a few decades ago. As more tourists visit remote areas like Tracy Arm Fjord to witness the natural beauty and learn about climate change, they are unknowingly putting themselves in harm’s way. Some cruise lines have already announced plans to stop sending ships into Tracy Arm due to safety concerns.
Dr. Higman and his colleagues are calling for increased monitoring of potential megatsunami hazards in Alaska. There is growing concern that the risks of such events will only continue to rise as climate change accelerates the melting of glaciers and destabilizes the region’s landscapes.
