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The coldest, windiest, and driest continent, overlying the South Pole. The lowest temperature ever measured on Earth was recorded at the Russian Antarctic station of Vostok at −89.2°C (−128.5°F) in July 1983. Katabatic (cold, gravitational) winds with velocities up to 50 km/h (30 mi/h) sweep down to the coast and occasionally turn into blizzards with 150 km/h (nearly 100 mi/h) wind velocities. Antarctica's interior is a cold desert with only a few centimeters of water-equivalent precipitation, while the coastal areas average 30 cm (12 in.).

Antarctica's area is about 14 million square kilometers (5.4 million square miles), which is larger than the contiguous 48 United States and Mexico together. It is the third smallest continent, after Australia and Europe. About 98% of it is buried under a thick ice sheet, which in places is 4 km (13,000 ft) thick, making it the highest continent, with an average elevation of over 2 km (6500 ft).

Although most of Antarctica is covered by ice, some mountains rise more than 3 km (almost 10,000 ft) above the ice sheet. The largest of these ranges is the Transantarctic Mountains separating east from west Antarctica, and the highest peak in Antarctica is Mount Vinson, 5140 m (16,850 ft), in the Ellsworth Mountains. Other mountain ranges, such as the Gamburtsev Mountains in East Antarctica, are completely buried, but isolated peaks called nunataks frequently thrust through the ice around the coast.

The Antarctic ice sheet is the largest remnant of previous ice age glaciations. It has probably been in place for the last 20 million years and perhaps up to 50 million years. It is the largest reservoir of fresh water on Earth, with a volume of about 25 million cubic kilometers (6 million cubic miles). Glaciers flow out from this ice sheet and feed into floating ice shelves along 30% of the Antarctic coastline. The two biggest ice shelves are the Ross and Filchner-Ronne. These shelves may calve off numerous large tabular icebergs, with thicknesses of several hundred meters, towering as high as 70–80 m (250 ft) above the sea surface.Glaciology

Year-round life on land in Antarctica is sparse and primitive. North of the Antarctic Peninsula a complete cover of vegetation, including moss carpets and only two species of native vascular plants, may occur in some places. For the rest of Antarctica, only lichen, patches of algae in melting snow, and occasional microorganisms occur. In summer, however, numerous migrating birds nest and breed in rocks and cliffs on the continental margins, to disappear north again at the beginning of winter. South of the Antarctic Convergence, 43 species of flying birds breed annually. They include petrels, skuas, and terns, cormorants, and gulls. Several species of land birds occur on the subantarctic islands. The largest and best-known of the Antarctic petrels are the albatrosses, which breed in tussock grass on islands north of the pack ice. With a wing span of 3 m (10 ft), they roam freely over the westerly wind belt of the Southern Ocean.

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From McGraw-Hill Concise Encyclopedia of Environmental Science. The Content is a copyrighted work of McGraw-Hill and McGraw-Hill reserves all rights in and to the Content. The Work is © 2008 by The McGraw-Hill Companies, Inc.
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