Antarctica is Earth's southernmost continent, overlying the South Pole. It is situated in the southern hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14.4 million square kilometers (5.4 million sq mi), it is the fifth-largest continent in area after Asia, Africa, North America, and South America. Some 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. Since there is little precipitation, except at the coasts, the interior of the continent is technically the largest desert in the world. There are no permanent human residents and there is no evidence of any existing or pre-historic indigenous population. Only cold-adapted plants and animals survive there, including penguins, fur seals, mosses, lichen, and many types of algae.
The name Antarctica comes from the Greek antarktikos (ανταρκτικός), meaning "opposite to the Arctic." 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 an Estonian-born explorer Fabian Gottlieb von Bellingshausen. However, the continent remained largely neglected for the rest of the 19th century because of its hostile environment, lack of resources, and isolation.
The Antarctic Treaty was signed in 1959 by twelve countries; to date, forty-five countries have signed the treaty. The treaty prohibits military activities and mineral mining, supports scientific research, and protects the continent's ecozone. Ongoing experiments are conducted by more than 4,000 scientists of many nationalities and with different research interests.