Recent research has revealed alarming developments in Alaska’s Denali National Park, where glaciers are melting at unprecedented rates, leading to increased risks of catastrophic events such as mega tsunamis. A striking example occurred in August 2025, when a massive rockslide triggered a tsunami reaching 481 metres in height, the second-tallest ever recorded. This incident serves as a stark reminder of the dangers posed by climate change and the retreat of glaciers in coastal regions.
A Record-Setting Tsunami
On 10 August 2025, at 5:26 am local time, the Tracy Arm fjord bore witness to a colossal landslide that unleashed a tsunami of historic proportions. According to the study published in *Science* and led by Dan Shugar, a geomorphologist at the University of Calgary, the landslide involved a 1-kilometre vertical drop onto the South Sawyer glacier, resulting in a wave that dwarfed the Eiffel Tower, which stands at 330 metres.
While there were no casualties during this early morning event, the fjord is frequented by approximately three cruise ships daily, alongside other maritime traffic. Just hours after the landslide, vessels such as a National Geographic tour boat and a sightseeing craft from Juneau were scheduled to enter the fjord. The previous day had seen thousands of cruise passengers visit the area, raising serious concerns about the safety of tourists and local communities alike.
Increased Risks from Climate Change
Dennis Staley from the US Geological Survey described the tsunami as “a historic event,” expressing relief that the situation did not result in fatalities. The researchers highlighted the growing frequency of such events, exacerbated by climate change, as glaciers continue to retreat and coastal rockslides become more likely. The study underscores the urgent need for better risk management strategies in these vulnerable areas.
Interestingly, the tsunami triggered a 36-hour seiche—an oscillating wave phenomenon—while also generating seismic waves comparable to a 5.4 magnitude earthquake. Eyewitness accounts from kayakers and other observers detailed the tsunami’s extensive reach: a wave surged past a campsite on Harbor Island, located approximately 55 kilometres away, while another observer in No Name Bay noted waves cresting at heights of up to 2.5 metres.
The Implications of Glacier Retreat
The study emphasised that the massive wave was made possible by the rapid retreat of glaciers, which created conditions that facilitated the landslide. Without this glacier melt, the event may not have occurred, or its consequences would have been significantly less severe. The report drew connections between climate-induced glacier retreat and an increase in landslide-generated tsunamis, noting that fjords with melting glaciers are now popular tourist destinations.
The number of cruise passengers in Alaska has surged from roughly 1 million in 2016 to 1.6 million in 2025, a trend that raises further concerns about the safety of maritime activities in these increasingly unstable environments.
Call for Better Preparedness
As climate change continues to destabilise coastal regions, researchers warn that the risk of large-scale landslide-generated tsunamis is rising across the Arctic. They advocate for enhanced monitoring of unstable slopes and realistic tsunami modelling scenarios. Stronger protective measures for local communities, tourists, and critical infrastructure are also essential to mitigate the dangers posed by these natural disasters.
Recent history has seen several significant tsunami events in Alaska, including a wave measuring 18 to 55 metres in Kenai Fjords National Park in 2024, and a 193-metre tsunami in Taan fjord in 2015, both linked to landslides near retreating glaciers.
Why it Matters
The findings from this study highlight an urgent call to action as climate change continues to reshape our planet. With the increasing frequency of mega tsunamis and the rapid melting of glaciers, the safety of coastal communities, tourists, and ecosystems hangs in the balance. The time has come for comprehensive strategies to address these threats, ensuring that both local populations and visitors can navigate these stunning yet perilous landscapes with greater assurance.