Continents of the world
Continents of the world :
Africa | Antarctica
| America | Asia
| Australia | Eurasia
| Eurafrasia | Europe
| Oceania | North
America | South
America
Antarctica
Antarctica is the southernmost continent and includes the South Pole. Geographic sources disagree as to whether it is surrounded by the Southern Ocean or the South Pacific Ocean, South Atlantic Ocean, and Indian Ocean. It is divided by the Transantarctic Mountains. On average, it is the coldest, driest, and windiest continent and has the highest average elevation of all the continents. At 14.425 million km², Antarctica is the third-smallest continent before Europe and Australia; 98% of it is covered in ice. Because 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 Antarctica has never had an indigenous population. Only cold-adapted plants and animals survive there, including penguins, fur seals, mosses, lichens, and many types of algae.
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. However, the continent remained largely neglected for the rest of the 19th century because of its hostile environment, lack of resources, and isolated location.
The Antarctic Treaty was signed in 1959 by 12 countries. 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
 Photo :: Antarctic map, Courtesy of the University of Texas Libraries, The University of Texas at Austin
Geography
Most of Antarctica is located south of the Antarctic Circle, surrounded by the Southern Ocean. It is the southernmost land mass and comprises more than 14 million km², making it the fifth-largest continent. The coastline measures 17 968 km (11,160 miles) and is mostly characterized by ice formations.
Physically, it is divided in two by the Transantarctic Mountains close to the neck between the Ross Sea and the Weddell Sea. The portion west of the Weddell Sea and east of the Ross Sea is called Western Antarctica and the remainder Eastern Antarctica, because they roughly correspond to the Western and Eastern Hemispheres relative to the Greenwich meridian.
About 98% of Antarctica is covered by the Antarctic ice sheet. The ice sheet is, on average, 2.5 kilometers (1.6 miles) thick. The continent has approximately 90% of the world's ice (approximately 70% of the world's fresh water). If all of this ice were melted sea levels would rise about 61 m (200 feet). In most of the interior of the continent precipitation is very low, down to 20 mm/yr; in a few "blue ice" areas precipitation is lower than mass loss by sublimation and so the local mass balance is negative. In the dry valleys the same effect occurs over a rock base, leading to a desiccated landscape.
Western Antarctica is covered by the West Antarctic Ice Sheet. The sheet has been of recent concern because of the real, if small, possibility of its collapse. If the sheet were to break down, ocean levels would rise by several meters in a relatively geologically short period of time, perhaps a matter of centuries. Several Antarctic ice streams, which account for about 10% of the ice sheet, flow to one of the many Antarctic ice shelves.
Vinson Massif, the highest peak in Antarctica at 4892 meters (16,050 feet), is located in the Ellsworth Mountains. Although Antarctica is home to many volcanoes, only Mt. Erebus is active. Mount Erebus, located in Ross Island, is the southernmost active volcano. There was another famous volcano called Deception Island, which is famous for its giant eruption in 1970. Minor eruptions are frequent and lava flow has been observed in recent years. Other dormant volcanoes may potentially be active. In 2004, an underwater volcano was found in the Antarctic Peninsula by American and Canadian researchers. Recent evidence shows this unnamed volcano may be active.
Antarctica is home to more than 70 lakes that lie thousands of meters under the surface of the continental ice sheet. Lake Vostok, discovered beneath Russia's Vostok Station in 1996, is the largest of these subglacial lakes. It is believed that the lake has been sealed off for 35 million years. There is some evidence that Vostok's waters may contain microbial life. The sealed, frozen surface of the lake shares similarities with Jupiter's moon Europa. Confirming that life can survive in Lake Vostok strengthens the argument for life on the satellite
Climate
Antarctica is the coldest place on Earth. It is a frozen desert with little precipitation; the South Pole itself receives less than 10 cm (4 inches) per year, on average. Temperatures reach a minimum of between -80 °C and -90 °C (-112 °F and -130 °F) in the interior in winter and reach a maximum of between +5 °C and +15 °C (41 °F and 59 °F) near the coast in summer. Sunburn is often a health issue as the snow surface reflects almost all of the ultraviolet light falling on it. Eastern Antarctica is colder than its western counterpart because of its higher elevation. Weather fronts rarely penetrate far into the continent, leaving the center cold and dry. Despite the lack of precipitation over the central portion of the continent, ice there lasts for extended time periods. Heavy snowfalls are not uncommon on the coastal portion of the continent, where snowfalls of up to 1.22 meters (48 inches) in 48 hours have been recorded.
At the edge of the continent, strong katabatic winds off the polar plateau often blow at storm force. In the interior, however, wind speeds are typically moderate. During summer more solar radiation reaches the surface during clear days at the South Pole than at the equator because of the 24 hours of sunlight each day at the Pole.
Antarctica is colder than the Arctic for two reasons. First, much of the continent is more than 3 km above sea level, and temperature decreases with elevation. Second, the Arctic Ocean covers the north polar zone: the ocean's relative warmth is transferred through the icepack and prevents temperatures in the Arctic regions from reaching the extremes typical of the land surface of Antarctica.
Given the latitude, long periods of constant darkness or constant sunlight create climates unfamiliar to human beings in much of the rest of the world. The aurora australis, commonly known as the southern lights, is a glow observed in the night sky near the South Pole. 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.
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