The Greenland ice sheet covers about 82% of the surface of Greenland. Satellite images from NASA show that it is melting at a rate of about 239 cubic kilometres (57.3 cubic miles) each year. If all of it melted, it would cause sea levels to rise by 7.2 metres. The ice sheet did not develop at all until the late Pliocene, but apparently developed very quickly. This had the unusual effect of allowing fossils of plants that once grew on present-day Greenland to be much better preserved than with the slowly forming Antarctic ice sheet.