The largest tsunami wave recorded by living witnesses reached approx. 1,720 ft. high. ( 524m ) July 9, 1958, Lituya Bay in Alaska. Had such a wave hit New York City, the wave would have submerged the tops of the city's largest sky scrapers ( WTC Towers, 1,368 ft. ) under 352 ft. of water.
Some geologists speculate that the most likely candidate for the source of the next large-scale megatsunami is the island of La Palma, in the Canary Islands. Reports say that during the 1949 eruption the western half of the Cumbre Vieja ridge slipped four metres downwards into the Atlantic Ocean, though this is disputed. It is believed that this process was driven by the pressure caused by the rising magma heating and vaporising water trapped within the structure of the island, causing the island's structure to be pushed apart. The island is still considered active, though quiescent at present, but it is expected to erupt again some time in the next few hundred years. Were this to happen it is speculated that a megatsunami would be created as the western half of the island, weighing perhaps 500 billion tonnes, catastrophically slides into the ocean in a single event, causing local wave heights of hundreds of metres and a likely height of around 10?25 m at the Caribbean and the Eastern North American seaboard coast several hours later. However, this is speculative since there is disagreement whether it would in fact happen, when, or how likely it is.
