A catastrophic collapse of Spain's Cumbre Vieja volcano could trigger a 'megatsunami' with the potential to reach the U.S. East Coast in a matter of hours, according to volcanologist Professor Bill McGuire.
McGuire's analysis, outlined in a BBC Science Focus article, proposes a worst-case scenario where a large section of the volcano's western flank detaches and plunges into the Atlantic Ocean. This event could displace a massive volume of seawater, generating waves that travel across the ocean.
A computer model suggests that such a collapse could create an initial dome of water nearly 3,300 feet high. This would subside to produce waves that could overwhelm La Palma and surrounding islands before propagating across the Atlantic. Estimates indicate waves could reach Florida approximately nine hours after the collapse, potentially as high as 65 feet. Waves reaching other parts of the U.S. East Coast could be around 33 feet high.
McGuire has been monitoring Cumbre Vieja on La Palma, located in Spain's Canary Islands off the coast of northwest Africa. He noted that the volcano's western flank showed signs of partial detachment during a 1949 eruption. His research team confirmed in the 1990s that this significant mass of rock, estimated to be billions of cubic yards, was slowly moving towards the sea.
"I expect this part of the flank will eventually crash into the North Atlantic, launching a megatsunami in the process," McGuire wrote.
He also pointed to large boulders found in the Bahamas, which some researchers believe were deposited by ancient tsunamis originating from the Canary Islands, suggesting that such waves can survive an Atlantic crossing. However, the origin of these deposits remains a subject of debate.
Volcanic flank collapses generate tsunamis by rapidly forcing a large amount of rock into the water, displacing the sea and sending waves outward. A volcano does not need to be actively erupting for a flank collapse to occur; gases can seep through the rock, weakening its internal structure and allowing a section to break off.
Evidence of prehistoric megatsunamis exists around the Canary Islands, with debris found nearly 980 feet above sea level suggesting at least five such events over the past million years. Similar deposits in the Cape Verde islands have been linked to an ancient collapse of the Fogo volcano.
Historical events illustrate the destructive potential of volcanic-induced landslides and tsunamis. In 1792, earthquakes near Japan's Unzen volcano triggered a landslide that caused significant destruction and resulted in approximately 15,000 deaths. More recently, the December 2018 disaster at Indonesia's Anak Krakatau volcano, where a partial collapse sent a tsunami toward coastal communities, killed over 400 people and destroyed thousands of homes. Volcanic tsunamis can also arrive as a series of waves, leading to repeated flooding.