Massive Alaska megatsunami was second largest ever recorded

A significant 'megatsunami' wave, which resulted from the collapse of part of an Alaskan mountain into the sea, has been identified as the second tallest ever recorded, emphasizing the potential dangers associated with melting glaciers, according to scientific experts.

In the summer of 2025, a colossal wave surged through a secluded fjord in southeast Alaska, causing widespread devastation. Although the incident did not receive extensive media coverage at the time, subsequent scientific analysis has revealed that minor earthquakes instigated a considerable landslide.

Approximately 64 million cubic metres of rock—equivalent to 24 Great Pyramids—plummeted into the water below. The immense force generated by this quantity of rock entering the fjord in under a minute resulted in a massive wave nearly 500 metres in height.

The timing of the event, occurring in the early morning hours, worked in favor of tourist cruise ships, preventing them from being affected by the disaster, as noted by researchers.

Dr. Bretwood Higman, an Alaskan geologist who personally observed the aftermath at Tracy Arm Fjord, described it as "a close call." He expressed concern over the potential risks for future incidents, 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 characterized by their immense waves, which occur when a landslide—triggered by either an earthquake or loose geological material—strikes the water. These events are generally localized and dissipate relatively quickly.

In contrast, traditional tsunamis originate in the open ocean, instigated directly by earthquakes or sometimes by other powerful phenomena, such as underwater volcanic activity. Events like the 2011 Japan tsunami can travel thousands of miles, affecting populated areas and resulting in widespread destruction and loss of life.

The record for the largest megatsunami was set in the 1950s, surpassing 500 metres in height. The recent megatsunami at Tracy Arm has now been classified as the second largest, following the Lituya Bay tsunami of 1958, which also occurred in Alaska.

Glacier Melt and Increased Risk

Upon visiting the site several weeks post-tsunami at Tracy Arm Fjord—a popular destination for cruise ships exploring Alaska's natural wonders—Dr. Higman observed broken trees scattered across the mountainside and into the water, alongside large areas of exposed rock stripped of soil and vegetation.

Alaska's geographical characteristics—steep mountains, narrow fjords, and frequent seismic activity—render it particularly susceptible to megatsunamis.

Recent research published in the journal Science indicates that glacier melt exacerbated by climate change is intensifying the likelihood of such catastrophic landslides. The research team employed fieldwork, seismic analysis, and satellite imagery to reconstruct the sequence of events that led to the wave's height.

Dr. Stephen Hicks from University College London pointed out that the glacier previously served to stabilize the rock formation, but as the ice receded, it left the cliff face vulnerable to collapse into the fjord. He and his colleagues, who have dedicated decades to the study of tsunamis, share their growing concern: "More people are now going to remote areas—often these tourist cruises are intended to observe the region's natural beauty and understand climate change—but they are also dangerous places to be."

Rising Frequency

Dr. Higman has expressed confidence that the risks associated with megatsunamis are escalating. "At this point, I'm pretty confident that these are increasing not just a little bit, but increasing a lot," he stated, estimating that their frequency may have increased tenfold over the past few decades.

In light of these findings, scientists advocate for enhanced monitoring of regions in Alaska that could be at risk of megatsunamis. Several cruise companies have begun to reassess their itineraries, opting to halt voyages into Tracy Arm out of safety concerns.