Antarctica is Earth’s southernmost continent, overlying the South Pole. It is situated in the Antarctica region of the southern hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14.4 million km2 (5.4 million sq mi), it is the fifth-largest continent in area after Asia, Africa, North America, and South America. About 98% of Antarctica is covered by ice, which averages at least 1.6 kilometers (1.0 mi) in thickness.
On average, Antarctica is the coldest, driest and windiest continent, and has the highest average elevation of all the continents. Antarctica is considered a desert, with annual precipitation of only 200 mm (8 inches) along the coast and far less inland. There are no permanent human residents, but anywhere from 1,000 to 5,000 people reside at the various research stations scattered across the continent throughout the year. Only cold-adapted plants and animals survive there, including penguins, seals, mosses, lichen, and many types of algae.
The name Antarctica is the romanized version of the Greek compound word Î±Î½Ï„Î±ÏÎºÏ„Î¹ÎºÎ® (antarktikÃ©), feminine of Î±Î½Ï„Î±ÏÎºÏ„Î¹ÎºÏŒÏ‚ (antarktikos), meaning “opposite to the north”. Although myths and speculation about a Terra Australis (”Southern Land”) date back to antiquity, the first confirmed sighting of the continent is commonly accepted to have occurred in 1820 by the Russian expedition of Mikhail Lazarev and Fabian Gottlieb von Bellingshausen.
The aurora australis, commonly known as the southern lights, is a glow observed in the night sky near the South Pole created by the plasma-full solar winds that pass by the Earth. Another unique spectacle is diamond dust, a ground-level cloud composed of tiny ice crystals. It generally forms under otherwise clear or nearly clear skies, so people sometimes also refer to it as clear-sky precipitation. A sun dog, a frequent atmospheric optical phenomenon, is a bright “spot” beside the true sun.