Massive Alaska megatsunami was second largest ever recorded

A massive megatsunami triggered by a colossal landslide in southeast Alaska last summer has been identified as the second tallest ever recorded, with a wave reaching nearly 500 metres in height. The event occurred when approximately 64 million cubic metres of rock—equivalent to 24 Great Pyramids—collapsed into a fjord near the South Sawyer Glacier, generating a devastating wave that swept through Tracy Arm Fjord. Fortunately, the timing in the early morning hours prevented any cruise ships, which frequently visit the area, from being caught in the disaster. The landslide and resulting megatsunami caused significant environmental damage, stripping vegetation and soil from the mountainside and scattering debris into the water. Geologists, including Dr Bretwood Higman who surveyed the site weeks after the event, described the situation as a "close call" for tourists and expressed concern about future risks. Alaska’s unique geography—characterized by steep mountains, narrow fjords, and frequent seismic activity—makes it particularly susceptible to such catastrophic landslides and megatsunamis. New research published in the journal Science links the event to glacier retreat driven by climate change. Scientists from University College London and other institutions used field observations, seismic data, and satellite imagery to reconstruct the sequence of events. They found that the retreat of the South Sawyer Glacier had previously supported the cliff face, and as the ice melted, it exposed unstable rock that eventually collapsed into the fjord. This domino effect highlights the growing threat posed by glacier melt in mountainous coastal regions. Megatsunamis differ from typical ocean-wide tsunamis caused by earthquakes or underwater volcanic activity in that they are highly localized but can produce extraordinarily tall waves. The largest recorded megatsunami occurred in the 1950s, with a wave over 500 metres high. The recent Alaska event underscores the increasing risks associated with climate-driven geological changes and raises concerns about the safety of communities and tourists in vulnerable coastal areas.