Ancient submarine landslide may have caused giant tsunami

Science : From rock deposits on an island off the west coast of Africa, researchers have found evidence of a possible megatsunami that may have been triggered by the collapsing rim of a powerful oceanic volcano some 73 000 years ago. Telltale signs of the volcanic eruption—scarring on the rim of the caldera and some 160 km³ of rock deposited on the sea floor—were found some time ago on Fogo, an island in the Cape Verde archipelago. Now, on the nearby island of Santiago, researchers have found 49 massive boulders that appear to have come from Fogo at about the same time as the ancient landslide occurred. Because some of the rocks weigh more than 700 tons and are located high up on two separate plateaus, the researchers conclude that the only way the rocks could have gotten there is by being pushed by a massive tsunami, more than 270 m high. Such an event today, were it to occur near a large city, could be devastating and should be taken into account in disaster mitigation plans, they say.