Massive Alaska megatsunami was second largest ever recorded

Key developments are emerging from the global stage. Massive Alaska megatsunami was second largest ever recorded1 hour ago Share Save Add as preferred on GoogleKate Stephens, Helen Briggs and Kevin Church, Climate and Science teamPhoto by Cyrus Read/U. Geological SurveyAerial view of the August 2025 landslide and tsunami near South Sawyer Glacier in AlaskaA massive 'megatsunami' wave created when part of an Alaskan mountain crumbled into the sea is the second tallest ever recorded – and a reminder of the risks posed by melting glaciers, say scientists. Last summer a giant wave swept through a remote fjord in southeast Alaska leaving destruction in its wake.

The event went largely unreported at the time, but a new scientific analysis shows tiny earthquakes triggered a massive landslide. An incredible 64 million cubic metres of rock – the equivalent of 24 Great Pyramids - splashed into the water below. The sheer power of that amount of rock plunging into the fjord in under a minute created a gigantic wave almost 500 metres tall.

The Details

Only the time it happened – in the early hours of the morning – prevented tourist cruise ships being caught up in the devastation, say the researchers. Dr Bretwood Higman, an Alaskan geologist, who saw for himself the damage at Tracy Arm Fjord, said it was "a close call". "We know that there were people that were very nearly in the wrong place," he said.

'I'm quite terrified that we're not going to be so lucky in the future. "Tracy Arm in Southeast Alaska is known for its sheer cliffs and icy terrainThese huge waves, labelled megatsunamis, happen when a landslide caused by either an earthquake or loose rock hit water below. They are usually localised and dissipate quickly.

The other type of tsunamis happen in the open ocean and are directly triggered by earthquakes, or occasionally other powerful events such as underwater volcanoes. They, like the 2011 Japan tsunami, can travel for thousands of miles, hitting populated areas and causing widespread devastation and loss of life. The biggest megatsunami was in the 1950s and was over 500 metres.

What Experts Say

This latest megatsunami was the second largest. The tsunami at Tracy Arm was beaten only by the Lityua Bay tsunami in 1958, also in AlaskaDr Higman arrived on the scene a few weeks after the tsunami hit at the Tracy Arm Fjord – a destination popular with cruise ships exploring the natural wonders of Alaska. He found broken trees littering the mountainside and hurled into the water, and vast swathes of scarred rock stripped of soil and vegetation.

Alaska is especially vulnerable to megatsunamis because of its steep mountains, narrow fjords and frequent earthquakes. Now new research published in Science suggests glacier melt driven by climate change is making such collapses far worse. The team combined field work, seismic and satellite data to reconstruct a domino chain of events and trace the height of the wave.

The development has drawn wide international attention, with diplomatic circles watching closely.