How Volcanic Islands Are Born

A submarine volcano can become an island when repeated eruptions build lava and volcanic debris to or above sea level. Surtsey, off Iceland, formed during an eruption from 1963 to 1967; however, not every new volcanic island lasts, as waves can quickly erode unstable ash. Hawaii has a different, long-term history: the islands formed over a hotspot beneath the Pacific Plate, which moved over it and left a chain of volcanoes and seamounts.