Antarctica
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Region lying south of the Antarctic Circle that includes the Antarctic continent surrounding the South Pole. Occupying 10% of the world's surface, in summer it is almost one-and-a-half times the size of the USA. Antarctica contains 90% of the world's ice, representing nearly three-quarters of its fresh water. It is thought that if all the ice suddenly melted, the world sea level would rise by 60 m/197 ft.
Area
13,000,000 sq km/5,019,300 sq mi; in winter Antarctica virtually doubles in area because of the increase in surrounding sea iceFeatures
Mount Erebus on Ross Island is the world's most southern active volcano, and reaches a height of 3,794 m/12,448 ft above sea level; the Ross Ice Shelf is formed by several glaciers coalescing in the Ross SeaPhysical
Antarctica can be divided into two regions, separated by the Transantarctic Mountains, which extend for 3,500 km/2,175 mi and whose peaks, many of them exceeding 3,000 m/9,850 ft in height, protrude through the ice. The larger region, known as Greater or East Antarctica, is comprised of ancient rocks lying mostly at sea level, which are approximately 3,800 million years old. In contrast, Lesser or West Antarctica is 150–200 million years old and has mountain ranges buried under the ice. These include the Antarctic Peninsular and the Ellsworth Mountains, in which the highest peak in Antarctica, the Vinson Massif, is located; height 5,140 m/16,863 ft. The few peaks that are visible above the ice are known as nunataks. Two vast seas, the Ross Sea and the Weddell Sea, cut into the continent. Between them lies the mountainous Antarctic Peninsula, which was originally connected to South America before continental driftPopulation
no permanent residents and no indigenous inhabitants; settlement is limited to scientific research stations with maximum population of 10,000 (including 3,000 tourists) during the summer months. Sectors of Antarctica are claimed by Argentina, Australia, Chile, France, the UK, Norway, and New ZealandAntarctic ice
Around 2% of the land is ice free. With an estimated volume of 30 million cu km/7.2 million cu mi, the ice-cap has an average thickness of approximately 2,000 m/6,600 ft, in places reaching depths of 4,000 m/13,000 ft or more. Each annual layer of snow preserves a record of global conditions, and where no melting at the surface of the bedrock has occurred the ice can be a million years old.The snow in the Antarctic rarely melts but accumulates into massive ice caps. As the ice caps grow, the weight of the ice squeezes the ice cap sideways towards the coast, where ice shelves extend out into the surrounding seas. These fringing ice shelves are broken up by ocean tides and waves, creating icebergs.
Solid ice attached to the Antarctic landmass is known as fast ice. If the ice forms a ridge more than 2 m/6.6 ft above sea level, it is known as an ice shelf. Pack ice is a mixture of ice floes in water. A lead is a navigable passage through pack ice. A polynya is a small area of open water surrounded by ice. The Antarctic Convergence is the point at which colder water from Antarctica meets and flows beneath warmer subantarctic water. The position of the Convergence may vary by up to 100 km/62 mi
Climate
The combination of cold air, high winds, and blowing snow makes Antarctica's climate the severest in the world. The location of Antarctica at the south pole results in only small amounts of energy being received from the sun. The temperatures are consequently very low. The Antarctic continent is surrounded by the Southern Ocean, which creates a physical barrier between Antarctica and the warmer seas and lands to the north. This creates a refrigeration of the Antarctic. It is the coldest continent on Earth, with a mean annual temperature at the South Pole of −49°C/−56°F. In 1983 a temperature of −89°C/−128°F was recorded in Antarctica at the Russian base Vostok, the lowest ever in the world.Precipitation is largely in the form of snow or hoar-frost rather than rain, which rarely exceeds 50 mm/2 in per year (less than the Sahara Desert). The minimal snow fall makes Antarctica one of the most arid deserts on Earth. Dry valleys are unique areas that remain snow-free all the year round because of the katabatic winds that remove moisture. The Antarctic summer (the period during which the ice melts) has lengthened from 60 to 90 days since the 1970s. The average temperature on the Antarctic Peninsula has risen by approximately 2.5°C/4.5°F since monitoring started in the 1950s, a result of the greenhouse effect.
Flora and fauna
The Antarctic ecosystem is characterized by large numbers of relatively few species of higher plants and animals, and a short food chain from tiny marine plants to whales, seals, penguins, and other sea birds.Plant life is rich in the Sub-Antarctic islands but is practically nonexistent in continental Antarctica. Only two species of flowering plant are known: the Antarctic pearlwort and the Antarctic hairgrass, both of which are rapidly increasing. There are about 85 species of moss, 200 species of lichen, and over 400 species of algae. As the Antarctic ice shelves disintegrate with the lengthening summers, new lichens are appearing in soil uncovered by the retreating glaciers.
There are five animal species which breed ashore during the winter months: emperor penguins, king penguins, wandering albatross, grey petrel, and the grey-winged petrel. The emperor penguin breeds under the most extreme environmental conditions of any vertebrate animal. There are only 67 species of insect; the largest in Antarctica is a midge measuring 12 mm/0.5 in. There are no native land mammals (the Arctic has 40); no resident land birds (the Arctic has 8); and fewer than 50 species of seabirds, only 13 of which breed in Antarctica. Because of the cold conditions, animals live longer, produce fewer eggs, and protect them for longer.
The oceans around the Antarctic contain relatively few fish; it is estimated that there are six times as many squid by weight in Antarctic seas as fish. Three-quarters of the Antarctic fish belong to the order Nototheniidae, comprising five families, of which four are found only in Antarctica, reflecting the need for specialization to survive in such hostile conditions. Most of them are deepwater fish. There is a high level of parental care, unusual in fish. Fish have low levels of haemoglobin, and some have a specialized ‘antifreeze’ glycoprotein in their blood, which lowers its freezing point, enabling them to survive without freezing in the sea at −1.9°C/28.6°F.
Large creatures on the Antarctic seabed, discovered in the late 1990s, include: isopods up to 17 cm/7 in long; sea spiders up to 33 cm/13 in (1,000 times larger than European sea spiders); ribbon worms 3 m/10 ft long; and a sponge 3 m/10 ft tall.
Products
Cod, Antarctic icefish, and krill are fished in Antarctic waters. Whaling, which began in the early 20th century, ceased during the 1960s as a result of overfishing, although Norway and Iceland defied the ban in 1992 and recommenced whaling. Petroleum, coal, and minerals such as palladium and platinum exist, but their exploitation is prevented by a 50-year ban on commercial mining, agreed by 39 nations in 1991.Exploration
The first person to explore Antarctica was Captain James Cook, who reached 70° 10' South in 1774; the most southerly point to which a ship had ever sailed. In 1775 Cook took possession of the Isle of Georgia and reached the South Sandwich Islands. In 1819 William Smith landed on and claimed for the UK the South Shetland Islands.International cooperationThe International Geophysical Year (IGY) 1957–58 marked a turning point in the understanding of this region. IGY was a worldwide experiment involving 66 nations and costing $75 million. The Antarctic section of the project was one of the most expensive components, involving 12 nations: Argentina, Australia, Belgium, Chile, France, Japan, New Zealand, Norway, South Africa, the Soviet Union, the UK, and the USA. Following IGY a series of conferences took place culminating in the signing of the Antarctic Treaty in 1959, which came into force in 1961. The Treaty covers the area south of 60° south. It recognizes ‘that it is in the interests of all mankind that Antarctica shall continue to be used exclusively for peaceful purposes and shall not become the scene or object of international discord’. A protocol to this treaty banned oil and other mineral exploration for at least the subsequent 50 years. The establishment of military bases, the testing of weapons, nuclear explosions, and the disposal of radioactive material were forbidden, and all national territorial claims were frozen. |
Geological history180 million years ago Antarctica was the keystone of a great southern supercontinent called Gondwanaland, which, before its break-up through continental drift, also included the Brazilian Plateau, most of Africa, and the Western Plateau of Australia. The geology has never been investigated in detail because of the thickness of the permanent ice which covers it. However, seismic and radio-echo soundings have revealed a picture of the continent beneath the ice. |
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