The Antarctic Peninsula is the northernmost part of the mainland of Antarctica, located at the base of the Southern Hemisphere. At the surface, it is the biggest, most prominent peninsula in Antarctica as it extends 1300 km (800 miles) from a line between Cape Adams (Weddell Sea) and a point on the mainland south of Eklund Islands. Beneath the ice sheet which covers it, the Antarctic Peninsula consists of a string of bedrock islands; these are separated by deep channels whose bottoms lie at depths considerably below current sea level. They are joined together by a grounded ice sheet. Tierra del Fuego, the southernmost tip of South America, lies only about 1000 km (620 miles) away across the Drake Passage.