Extensive, topographically high area of an ocean floor that rises to within 2–3 km of the sea surface above the abyssal floor, e.g. the plateau on which Iceland stands, the Galápagos Islands platform, and the Azores platform. Many Pacific plateaux, e.g. the Magellan Rise and Ontong Java Plateau, have a thick covering of carbonate oozes overlying volcanic rocks. The origin of such plateaux is volcanic, but many are now inactive.