The glaciers of Chile cover 2.7% (20,188 km2) of the land area of the country, excluding Antártica Chilena, and have a considerable impact on its landscape and water supply. By surface 80% of South America's glaciers lie in Chile. Glaciers develop in the Andes of Chile from 27˚S southwards and in a very few places north of 18°30'S in the extreme north of the country: in between they are absent because of extreme aridity, though rock glaciers formed from permafrost are common. The largest glaciers of Chile are the Northern and Southern Patagonian Ice Fields. From a latitude of 47° S and south some glaciers reach sea level.