A colossal tsunami measuring 1,578 feet (481 metres) in height—one and a half times the size of the Eiffel Tower—struck the popular tourist destination of Tracy Arm fjord in Alaska on 10 August 2025, according to a new study. This event ranks as the second highest tsunami ever recorded, surpassed only by the 1,720-foot (524-metre) wave that hit Lituya Bay, Alaska, in 1958.
Landslide Triggered by Glacial Retreat
The tsunami was caused by a massive landslide, which researchers from University College London (UCL) attribute to the effects of climate change. The glacier that had been supporting the mountain retreated rapidly—by 500 metres in just a few weeks—leaving the rock unsupported. When the rock plunged into the water, it generated an enormous wave.
Dr Stephen Hicks, co-author of the study, explained: "Fjords with retreating glaciers have seen a sharp increase in tourism. More people are visiting these beautiful places in the polar and sub-polar regions, but they are at the forefront of climate change impacts and can be dangerous. This event took everyone by surprise. The area had not been identified as hazardous."
Eyewitness Accounts and Scientific Analysis
Although no one was caught directly in the wave, several eyewitnesses provided accounts that were combined with numerical modelling, satellite data, and seismometer readings to reconstruct the event. The wave stripped trees and vegetation from the fjord walls, leaving a sheer rock face that allowed researchers to estimate the wave height at 1,578 feet for over 0.6 miles (1 km).
A group of kayakers camping further down the fjord reported waking at around 5:45 am to find water flowing past their tent, carrying away one kayak and much of their gear. Another eyewitness described a two-metre wave coming along the beach. Observers on a cruise ship anchored near the fjord's mouth saw currents and white water but no obvious wave.
Massive Scale of the Landslide
The amount of rock that crashed into the water was equivalent to 24 Great Pyramids of Giza, according to the researchers. Lead author Dr Dan Shugar, from the University of Calgary, noted: "Normally with these gigantic rock avalanches, they often give some sort of warning signs in the weeks, months, or years prior when the slope is slowly moving down the mountain. It's sagging and then it catastrophically gives way. In this case, that didn't happen."
Urgent Need for Warning Systems
Given the popularity of Tracy Arm fjord with cruise ships, the researchers stress the need for urgent action to prevent a repeat incident. Dr Hicks stated: "We need to reduce the risk of these expeditions by better identifying the riskiest areas and getting investment into warning systems that might give us a few hours' or days' notice of a potentially catastrophic event. With hindsight, there were some warning signs. Tiny earthquakes occurred at an increasing rate in the days to hours before the landslide, signalling that this mass of rock was starting to crack. Many seismic monitoring stations provide data in real-time, so this gives us some optimism that we can turn what we have learned into a warning system."
So far in 2025, at least six cruise lines have been forced to change their itineraries to avoid the Tracy Arm fjord. Dr Shugar added: "Ultimately what we hope is that coastal municipalities, the cruise ship industry, and other stakeholders take these threats seriously."
Broader Tsunami Risks
The news comes shortly after scientists warned that the French Riviera is "overdue" for a tsunami, with a 100 per cent chance of a great wave forming in the Mediterranean Sea within the next 30 years. Such a tsunami could hit France's southern coastline in as little as 10 minutes from the trigger, potentially endangering tens of thousands of summer tourists.
What Causes Tsunamis?
A tsunami, sometimes called a tidal wave or seismic sea wave, is a series of giant waves created by a disturbance in the ocean—most often an earthquake, but also landslides, volcanic eruptions, or meteorites. If the trigger occurs near the shore, the first wave can arrive within minutes, before any warning can be issued. Areas less than 25 feet above sea level are most at risk. The primary cause of death is drowning, but additional hazards include drinking water contamination, fires, and flooding. Inhabitants of coastal areas are advised to follow evacuation routes and seek higher ground or move inland immediately upon receiving a tsunami warning.
