A collapsing volcano could trigger a vast tidal wave capable of wiping New York, Washington and Miami off the map, warn geologists.

They also fear southern England could be hit.

Geologists are concerned that an unstable flank of the Cumbre Vieja volcano on the island of La Palma in the Canaries is in danger of sliding into the sea.

If shaken loose by a volcanic eruption, the huge slab of rock would send a tsunami more than 150 metres high racing across the Atlantic at the speed of a jumbo jet.

Within three hours, the wave would swamp the west coast of Africa, within five hours it would reach southern England and within 12 it would hit America's east coast.