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A colossal megatsunami triggered by a landslide in Alaska has been identified as the second tallest wave ever recorded, raising alarms about the dangers posed by retreating glaciers. The event, which unfolded in August 2025, saw a staggering 64 million cubic metres of rock plunge into a remote fjord, resulting in a wave that soared nearly 500 metres high, according to a recently published analysis by scientists.
The Unfolding of the Event
In the early hours of that fateful summer day, a dramatic landslide occurred near South Sawyer Glacier in Southeast Alaska, sending a massive volume of rock crashing into the sea. Despite the magnitude of the disaster, the incident initially went largely unnoticed. However, further investigations revealed that the sheer force of the landslide generated a wave of unprecedented height.
Dr Bretwood Higman, a geologist based in Alaska, described witnessing the aftermath of the megatsunami at Tracy Arm Fjord. “It was a close call,” he noted, highlighting the narrow escape of tourist cruise ships that could have been caught in the chaos. “We know that there were people who were very nearly in the wrong place. I’m quite terrified that we’re not going to be so lucky in the future.”
Understanding Megatsunamis
Megatsunamis are typically caused by sudden geological events, such as landslides triggered by earthquakes or the destabilisation of loose rock. These waves are generally localised, dissipating quickly and causing damage primarily to nearby areas. In contrast, traditional tsunamis, like the catastrophic one that struck Japan in 2011, are generated by seismic activity beneath the ocean and can travel vast distances, wreaking havoc on coastal communities.
The largest recorded megatsunami occurred in the 1950s, reaching heights exceeding 500 metres. The recent event has now taken its place as the second largest, signalling a growing concern among researchers regarding the frequency and intensity of such occurrences.
The Role of Climate Change
The implications of this event extend far beyond its immediate devastation. New research published in *Science* suggests that climate change, particularly the melting of glaciers, is exacerbating the risks associated with landslides and megatsunamis in Alaska. Dr Stephen Hicks from University College London explained that glaciers previously acted as stabilising factors for rock formations. As ice retreats, it exposes cliff faces, increasing the likelihood of sudden collapses.
“The glacier was helping to hold up this piece of rock,” Hicks noted. “When the ice retreated, it allowed that rock material to suddenly collapse into the fjord.” His team, which has dedicated decades to studying tsunamis, is urgently calling for enhanced monitoring of regions in Alaska that are susceptible to megatsunami risks.
A Call for Vigilance
The increase in visitor numbers to these remote areas, many drawn by the allure of Alaska’s natural beauty and the impacts of climate change, raises additional safety concerns. Dr Higman warned that these locations, while breathtaking, can also be perilous. “More people are now going to remote areas. These tourist cruises aim to showcase the natural wonders of the region, but they are also dangerous places to be,” he cautioned.
In light of the heightened risks, some cruise companies have begun to reassess their itineraries, opting to suspend trips to Tracy Arm amidst safety fears. The scientific community is advocating for a comprehensive review of monitoring systems to better understand and manage the hazards posed by megatsunamis in the region.
Why it Matters
The recent Alaskan megatsunami serves as a stark reminder of the intricate relationship between climate change and geological stability. As glaciers continue to melt, the risks of catastrophic landslides and megatsunamis are expected to rise, posing significant threats not only to natural landscapes but also to human life. Awareness and preparedness are crucial as more people venture into these stunning but volatile environments, underscoring the urgent need for proactive measures to safeguard both the environment and those who seek to explore it.