Mega-tsunamis are giant waves triggered by massive landslides, collapsing volcanoes, or even asteroid strikes—far more powerful than regular tsunamis. Picture “a wall of water up to a third of a mile high, roaring across the ocean at hundreds of miles per hour.”

One frightening possibility involves the Cumbre Vieja volcano on La Palma in the Canary Islands. A 2001 study suggested that a collapse of its west flank could send “up to 120 cubic miles of rock into the sea,” starting a 2,000-foot wave still 150 feet high when it hits the Americas. This scenario, while debated, was dramatized in the Netflix series La Palma.

The U.S. East Coast could be in the wave’s path if such a collapse occurs, though experts emphasize this event is not imminent.