A devastating megatsunami triggered by a landslide in Alaska has been identified as the second tallest ever recorded, raising alarms about the escalating risks associated with climate change and melting glaciers. This colossal wave, which surged through a remote fjord in the summer of 2025, serves as a stark reminder of the potential dangers posed by our changing environment.
The Event: A Hidden Catastrophe
In August 2025, a massive landslide occurred near South Sawyer Glacier, unleashing approximately 64 million cubic metres of rock—equivalent to 24 Great Pyramids—into the sea. This landslide generated a wave nearly 500 metres high, making it only slightly smaller than the largest megatsunami recorded in the 1950s. The incident, which took place in the early hours of the morning, went largely unnoticed at the time, narrowly avoiding the presence of tourist cruise ships that frequent the area.
Dr Bretwood Higman, a geologist who witnessed the aftermath at Tracy Arm Fjord, described the event as “a close call.” He expressed concern over the increasing likelihood of similar occurrences in the future, stating, “We know that there were people that 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 localised phenomena resulting from landslides into bodies of water, often triggered by natural events such as earthquakes or the destabilisation of loose rock. Unlike traditional tsunamis, which can travel vast distances across oceans and are primarily caused by seismic activity, megatsunamis dissipate relatively quickly and pose immediate threats to nearby regions.
The destructive potential of these waves is magnified in areas like Alaska, characterised by steep mountains and narrow fjords. The recent incident at Tracy Arm underscores the precarious balance between natural geological processes and environmental changes driven by climate factors.
Climate Change: A Catalyst for Disaster
Recent scientific research published in *Science* has established a link between climate change and the increased frequency and severity of megatsunamis. Dr Stephen Hicks from University College London noted that glacier melt, driven by rising global temperatures, has weakened the structural integrity of cliffs, making them more susceptible to collapse. As glaciers retreat, they expose rock faces, facilitating rapid landslides into the fjords below.
Dr Higman confirmed the scientists’ concerns, asserting that the risks associated with megatsunamis are not just increasing incrementally but are potentially tenfold compared to a few decades ago. This alarming trend coincides with a rise in tourism to these remote areas, where visitors come to witness the effects of climate change firsthand, blissfully unaware of the lurking dangers.
A Call for Vigilance
In light of these findings, researchers are advocating for enhanced monitoring of regions in Alaska susceptible to megatsunamis. Some cruise lines have already opted to suspend operations in Tracy Arm due to safety concerns, emphasising the need for a comprehensive approach to disaster preparedness in vulnerable areas.
As climate change continues to reshape environmental landscapes, the need for proactive measures becomes ever more critical. The potential for megatsunamis to wreak havoc in populated regions necessitates