Professor Bill McGuire, a British volcanologist, has renewed warnings that a collapse of the western flank of Cumbre Vieja on the Spanish island of La Palma could generate a megatsunami, potentially sending waves as high as 65 feet towards the US East Coast within nine hours. However, scientists emphasize that such an event is not an imminent threat and its timing remains uncertain, potentially occurring centuries or millennia from now.
The concern centers on the stability of a section of the volcano’s western flank. McGuire’s warning is based on extensive studies of Cumbre Vieja, which has a history of eruptions, most recently in 2021, when an 85-day event devastated parts of La Palma. His concerns are partly rooted in fractures that developed along the western flank during an eruption in 1949, raising questions about its long-term stability, according to Marca.
The Megatsunami Scenario
The megatsunami hypothesis gained international following a 2001 research paper by geophysicists Steven Ward and Simon Day. Their study investigated a theoretical failure of Cumbre Vieja’s western side, projecting that 150 to 500 cubic kilometres of rock might displace into the Atlantic Ocean. McGuire argues that geological data, such as gigantic boulders discovered on the Bahamas coast, implies powerful prehistoric tsunamis may have started in the Canary Islands, although this claim is disputed by some
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One predictive model, cited by McGuire in BBC Science Focus, outlines a worst-case scenario
where a collapse would generate an initial dome of water almost a kilometer high. This would subside to create waves hundreds of meters high near La Palma before sending waves of around 20 meters crashing into Florida just nine hours later, leaving little time for a mass evacuation
. McGuire wrote, Based on extensive studies, I expect this part of the flank will eventually crash into the North Atlantic, launching a megatsunami in the process.
He added, There has been huge debate and discussion, sometimes quite heated, about the level of expected destruction. In particular, whether devastating waves will reach the coast of North America.
Scientific Disagreement
The possibility of a transatlantic megatsunami remains controversial within the scientific community. A 2001 academic paper proposed the idea of the La Palma volcano giving way and producing tsunami waves as high as 80 feet along the east coasts of North and South America. However, the USGS has expressed skepticism about this hypothesis.
A 2025 assessment of tsunami hazards along the US East Coast also considered hypothetical Cumbre Vieja flank-collapse scenarios. According to the USGS, the waves would probably be between 3 and 7 feet high by the time they reached the U.S.
Evidence of Past Events
Despite the disagreement, scientists acknowledge that volcanic landslides can produce deadly tsunamis. This was demonstrated when Krakatau volcano partially collapsed in December 2018, killing more than 400 people. McGuire wrote in BBC Science Focus, Large rock masses can fall into the sea from coastal or island volcanoes at any time, driving devastating waves onto nearby coastlines and sometimes to great distances.
He added, Volcanoes might seem like bastions of stability, but many are just tottering piles of rubble, rotted internally by seeping volcanic gases and looking for any excuse to collapse.
Experts Describe Hypothetical Wave Speed
While the projected nine-hour travel time for a transatlantic tsunami is a critical factor, experts stress it describes a hypothetical wave’s speed, not an imminent evacuation deadline. McGuire himself has no doubt the event would be cataclysmic but has no idea when it will happen, it could easily be centuries or even millennia down the line.
