Antarctica

 

(ăntärk'tĭkə, –är'tĭkə) , the fifth largest continent, c.5,500,000 sq mi (14,245,000 sq km), asymmetrically centered on the South Pole and almost entirely within the Antarctic Circle.

Geology and Geography

Antarctica consists of two major regions: W Antarctica (c.2,500,000 sq mi/6,475,000 sq km), a mountainous archipelago that includes the Antarctic Peninsula, and E Antarctica (c.3,000,000 sq mi/7,770,000 sq km), geologically a continental shield. They are joined into a single continental mass by an ice sheet thousands of feet thick. At the seaward margins of the ice sheet masses of ice break off and float away as icebergs, leaving ice cliffs. Where the outward creep of the ice is channeled into ice streams (zones of more rapid flow), great floating ice tongues project into the sea; where mountains retard outward movement, the flow is channeled into great valley glaciers.

Less than 5% of Antarctica is free of ice; these areas include mountain peaks, arid “dry valleys,” small coastal areas, and islands. Except for mountain ranges (some buried beneath the ice), much of E Antarctica's rock surface is near sea level; however, the continent's domed, snow-covered glacial surface rises to about 13,000 ft (4,000 m). In W Antarctica there is great variation in the subglacial relief, suggesting mountainous islands or submerged ranges separated by deep sounds beneath the ice cover. Since the 1970s more than 100 lakes of liquid water have been identified underneath the continental ice; the largest known of these is Lake Vostok, which lies 2.5 mi (4 km) beneath the Russian Vostok research station in E Antarctica. Many of the lakes are connected by subglacial rivers.

The two major coastal indentations are the Ross Sea, facing the Pacific Ocean, and the Weddell Sea, facing the Atlantic Ocean. At the head of each sea are great ice shelves, the Ross ice shelves in the Ross Sea and the Ronne and the Filchner ice shelves in the Weddell Sea. Partly aground but mostly afloat, these nearly level ice shelves are from 600 to 4,000 ft (180–1,220 m) thick. They move steadily toward the sea and are fed by valley glaciers, ice streams, and surface snow accumulations. Smaller ice shelves are found all along the coast.

The Transantarctic Mts (c.3,500–14,300 ft/1,100–4,400 m high), which extend from the east side of the Filchner Ice Shelf to the western portal of the Ross Sea, form the inner margin of E Antarctica. Primarily formed by block faulting (see mountains), the lower slopes have a complex structure of late Precambrian and early Paleozoic metamorphic rocks. These are overlaid by essentially horizontal sedimentary rock, mainly of continental or near-shore origin and ranging in age from the Devonian period to the early Jurassic, which are similar to rocks found in Australia, S Africa, and E South America; coal-bearing Permian strata are also found there. Distinctive plant, insect, fish, and animal fossils in the Triassic and Jurassic strata strongly indicate that the continents of the Southern Hemisphere are parts of an ancient supercontinent, Gondwanaland, which broke up in the late Mesozoic era. The continents have since drifted to their present positions.

The ice-drowned, mountainous archipelago of W Antarctica is related to the Andes Mts. of South America and is structurally connected to them by way of the Antarctic Peninsula and the Scotia Arc (South Georgia and the South Orkney and South Sandwich islands). The complex structure consists of highly folded metasedimentary strata from Paleozoic to Pliocene epochs. There has been much volcanism down to the present. Mountains of the Antarctic Peninsula rise to c.11,000 ft (3,350 m); the mountains of Marie Byrd Land have comparable heights. The Ellsworth Mts., at the head of Ronne Ice Shelf, are the highest in Antarctica; Vinson Massif (16,860 ft/5,140 m) is the continent's highest peak. A variety of mineral deposits have been discovered in Antarctica, but the extent of the deposits is largely unknown and their relative inaccessibility makes their utility doubtful.

Antarctica is surrounded by the world's stormiest seas. A belt of pack ice surrounds the continent; only a few areas are ice-free at the end of most summers. The physical boundary most widely accepted today for the antarctic region is the Antarctic Convergence, a zone c.25 mi (40 km) wide encircling the earth along a fluctuating, zigzagging line between 48°S and 61°S,. Within this zone the colder and denser north-flowing antarctic surface waters sink beneath warmer and saltier subantarctic waters; the difference in temperature and chemical content of the water on the two sides of the zone is reflected in noticeable differences in air temperature and in marine life. These differences and other characteristics have led oceanographers to regard the waters around Antarctica as a fifth ocean, the Southern Ocean (also known as the Antarctic Ocean).

Climate

Antarctic climate is characterized by low temperature, high wind velocities, and frequent blizzards. Rapidly changing weather is typical of coastal locations, where temperatures for the warmest month average around freezing. Winter minimums drop as low as −40°F (−40°C). High altitude and continuous darkness in winter combine to make the interior of Antarctica the coldest place on earth. Summer temperatures are unlikely to be warmer than 0°F (−18°C); winter mean temperatures are −70°F (−57°C) and lower. The lowest temperature ever recorded on earth was −126.9°F (−88.3°C) at Vostok, a Russian station. Precipitation is in the form of snow; the annual water equivalent in the interior is c.2 in. (5 cm) and c.10 in. (25 cm) in coastal areas. In the dry, dust-free air one can see for tens of miles in clear weather; distances are deceptive, and mirages are common. Scattering of light by blowing snow or low clouds causes “whiteouts” in which the sky blends with the snow-covered surface, eliminating the horizon; no condition is more feared by aviators.

Antarctic Life

There is no native human population in Antarctica, nor are there any large land animals. Few species are adapted to the antarctic environment, but individuals of these few species are numberless. Life that depends completely on the land is limited to microscopic life in summer meltwater ponds, tiny wingless insects living in patches of moss and lichens, and two types of flowering plants (both in the Antarctic Peninsula). Birds and seals that spend part of their time on land (e.g., emperor and Adélie penguins and the brown skua—the most southerly bird and a notorious predator—and Weddell, crabeater, and Ross seals) are dependent on the surrounding sea for food. Antarctic waters are rich in plankton, which serves as food for krill, small shrimplike crustaceans that are the principal food of baleen whales, crabeater seals, Adélie penguins, and several kinds of fish.

Fur and elephant seals, which spend the summers on islands north of lat. 65°S were the basis for 19th-century commercial activity in Antarctica. In the 20th cent., commercial interest shifted to baleen whales. Fur seals are recovering from the slaughter of the 19th cent., as are the elephant seals. Whaling has been declining since the peak year of 1930–31. In 1986 the International Whaling Commission imposed a moratorium on commercial whaling; the moratorium, however, has not been adhered to by all nations.

History of Exploration

Early Expeditions

Although there was for centuries a tradition that another land lay south of the known world, attempts to find it were defeated by the ice. Antarctica's frigid nature was revealed by the second voyage (1772–75) of the English explorer Capt. James Cook. He did not see the continent as he circumnavigated the world, but he was the first to cross the Antarctic Circle. British and U.S. seal hunters followed him to South Georgia, an island in the S Atlantic.

In 1819 the British mariner William Smith discovered the South Shetland Islands. Returning in 1820, he and James Bransfield of the British navy explored and roughly mapped the Shetlands and part of the shore of the Antarctic Peninsula. Searching for rookeries, sealers explored the coastal and offshore regions of the Antarctic Peninsula. Most notable were the British captains James Weddell, George Powell, and Robert Fildes and the Americans Nathaniel B. Palmer, Benjamin Pendleton, Robert Johnson, and John Davis. Davis made the first landing on the antarctic continent (Feb. 7, 1821) at Hughes Bay on the Antarctic Peninsula. First to spend the winter in Antarctica, on King George Island in 1821, were 11 men from the wrecked British vessel Lord Mellville.

After 1822 fur sealing declined, but in 1829–30 Palmer and Pendleton led a sealing and exploring expedition that included Dr. James Eights, the first U.S. scientist to visit Antarctica. John Biscoe, a British navigator, circumnavigated Antarctica from 1830 to 1832, sighting Enderby Land in 1831 and exploring the western side of the Antarctic Peninsula in 1832. John Balleny and Peter Kemp were other British sealers who made discoveries in E Antarctica in the 1830s.

Four naval exploring expeditions visited Antarctica in the first half of the 19th cent. Capt. T. T. Bellingshausen was the leader of a Russian expedition that circumnavigated Antarctica (1819–21). He apparently was the first to see (1820) the part of the continent that is now called Queen Maud Land. In W Antarctica he discovered (1821) Peter I Island and Alexander Island. Admiral J. S. C. Dumont d'Urville led a French expedition to the Pacific Ocean that made two visits to Antarctica. He explored in the area of the Antarctic Peninsula in 1838 and in 1840 discovered Clarie Coast and Adélie Coast in E Antarctica. In 1840 Lt. Charles Wilkes, leader of the U.S. Exploring Expedition to the Pacific (1838–42), sailed along the coast of E Antarctica for 1,500 mi (2,400 km), sighting land at nine points. British Capt. James C. Ross commanded two vessels on an expedition (1841–43) that discovered Victoria Land in E Antarctica, the Ross Sea, and the Ross Ice Shelf and explored and mapped the western approaches of the Weddell Sea.

Inland and to the Pole

In the 1890s, after a half-century of neglect, interest in Antarctica was revived. Norwegian and Scottish whaling firms sent ships (1892–93) to investigate the possibilities of whaling around the Antarctic Peninsula, and a Norwegian vessel examined the Ross Sea area, where a landing was made (1895) on Cape Adare. C. A. Larsen began whaling at South Georgia island in 1904–5, and the seas of the Scotia Arc became the center of Antarctic whaling until after 1926.

The 1890s also marked the beginning of a period of extensive Antarctic exploration, during which 16 exploring expeditions from nine countries visited the continent. For the first time, many of them were financed by private individuals and sponsored by scientific societies. It was a period of innovation and hardship in an extremely harsh, little-known environment. The Belgian expedition under Lt.Adrien de Gerlache was beset in the pack ice in Mar., 1898, and the ship drifted west across the Bellingshausen Sea for a year before it was released. A British expedition led by C. E. Borchgrevink was the first to establish a base for wintering on the continent (Cape Adare, 1899) and the first to make sledge journeys. Different parts of the Antarctic Peninsula and the islands of the Scotia Arc were explored by de Gerlache (1897–98), a Swedish expedition under Dr. Otto Nordenskjold (1901–4), the Scottish National Antarctic Expedition led by W. S. Bruce (1902–4), and two French expeditions led by Dr. Jean B. Charcot (1903–5 and 1908–10). Nordenskjold spent two winters in Antarctica before being rescued after his ship was crushed by ice.

Exploration in the Ross Sea area during this period was characterized by long inland journeys. Four British expeditions had bases on Ross Island at McMurdo Sound. British Capt. R. F. Scott headed two expeditions (1901–4 and 1910–13), E. H. Shackleton led another expedition (1907–9), and A. E. Mackintosh headed the Ross Sea Party of Shackleton's unsuccessful Trans-Antarctic Expedition (1914–17). Roald Amundsen, a Norwegian, set up his base at the Bay of Whales, an indentation in the front of the Ross Ice Shelf, and a Japanese expedition (1911–12) was ship-based. The British expeditions carried out extensive exploration and scientific investigation of Victoria Land. Shackleton sledged to within 97 mi (156 km) of the South Pole (Jan., 1909), but it was Amundsen who reached the Pole first, on Dec. 14, 1911. Scott reached it on Jan. 17, 1912, but he and four companions perished on the return trip.

The Weddell Sea border of E Antarctica was seen first by Bruce (1904), and it was later explored by the German expedition of Dr. Wilhelm Filchner, discoverer of the Filchner Ice Shelf, whose ship was beset and drifted in the Weddell Sea through the winter of 1912 before being released. Shackleton reached the Weddell Sea in Jan., 1915. He had planned to sledge to McMurdo Sound, via the South Pole, but his ship was beset and crushed in the ice, and his party lived on ice floes until they finally reached Elephant Island in boats. From there Shackleton made his epic voyage of c.800 mi (1,290 km) to South Georgia in an open boat.

Two other expeditions explored E Antarctica during the early 20th cent.—Dr. Erich von Drygalski's well-equipped German expedition (1901–3) was cut short on the Wilhelm II Coast when the ship was beset; and Douglas Mawson, leader of the Australasian Expedition (1911–14) established bases at Commonwealth Bay on the George V Coast and on the Queen Mary Coast. Five major sledge journeys were made from Commonwealth Bay; two men perished and Mawson barely survived.

Technological Advances in Exploration

In the period following World War I, scientific and technological advances were applied to further antarctic exploration. The first airplane flight in Antarctica (Nov. 26, 1928) was by Sir George Hubert Wilkins, an Australian who later flew down the eastern side of the Antarctic Peninsula. However, it was U.S. explorer Richard E. Byrd who most successfully coordinated radios, tractors, airplanes, and aerial cameras for the purposes of exploration.

On his first expedition Byrd established his base, Little America, near the site of Amundsen's old base at the Bay of Whales. From Little America he made the first flight over the South Pole on Nov. 29, 1929. On this expedition Marie Byrd Land was discovered and explored from the air. On his second expedition (1933–35) Byrd successfully integrated flights with long sledge and tractor journeys in a more complete exploration of Marie Byrd Land.

In 1929–30 three other expeditions were also using aircraft for short flights over the coast. Wilkins in 1929–30 operated in the Bellingshausen Sea. A Norwegian captain, Hjalmar Riiser-Larsen, explored (1929–30) the coast of E Antarctica from Enderby Land to Coats Land; the area was later claimed by Norway as Queen Maud Land. In Nov., 1935, U.S. explorer Lincoln Ellsworth made the first transantarctic flight, from Dundee Island at the tip of the Antarctic Peninsula to the Bay of Whales, landing four times en route. The British Graham Land Expedition explored the Antarctic Peninsula by sea, air, and dog team from 1935 to 1937, using a different base each winter. Germany made a calculatedly spectacular effort at aerial surveying when two aircraft flying from a catapult ship photographed approximately 135,000 sq mi (350,000 sq km) of Queen Maud Land.

The Norwegians had done considerable exploration and mapping during the first two decades of antarctic whaling in the Scotia Arc. In 1925–26 they introduced pelagic whaling with factory ships that could operate in the open sea. Between 1927 and 1937 Lars Christensen led an extensive program of aerial exploration and mapping of the coast of E Antarctica from the Weddell Sea to the Shackleton Ice Shelf. Also allied to whaling were the investigations in physical oceanography, marine biology, and coastal mapping carried out by the Discovery Committee of the British Colonial Office from 1925 to 1939. Their major achievement was the discovery of the Antarctic Convergence.

International Rivalry

The 1930s were a period of international rivalry in Antarctica, and the map was cut into wedgelike territorial claims that in some places overlapped. Although the U.S. government did not make a claim or recognize those of other nations, it supported antarctic exploration. The U.S. Antarctic Service Expedition (1939–41), directed by Byrd, introduced the notion of permanent bases, one of which was set up at the Bay of Whales and another on Stonington Island W of the Antarctic Peninsula. The onset of World War II forced the evacuation of the bases, but before the war ended Great Britain, in order to offset claims by Chile and Argentina, had established permanent bases on the Antarctic Peninsula and off-lying islands.

Interest in Antarctica intensified after the war, and several governments established permanent agencies to direct antarctic affairs. Great Britain, Argentina, and Chile continued the system of scientific bases in the Antarctic Peninsula and Scotia Arc. Australia established bases on Heard and Macquarie islands, and France founded one on the Adélie Coast. From 1945 to 1957 the U.S. navy conducted Operation Highjump, an expedition involving c.5,000 men. About 60% of the coastline was photographed, as well as much of the interior bordering the Ross Ice Shelf.

The Ronne Antarctic Research Expedition (1947–48), led by Finn Ronne, was the last privately sponsored U.S. expedition. Using Byrd's old base on Stonington Island, Ronne closed the unexplored gap at the head of the Weddell Sea. A portent of the international cooperation soon to follow, the Norwegian-British-Swedish Antarctic Expedition was organized by the respective governments and scientific societies for exploration and scientific investigation in Queen Maud Land.

The International Geophysical Year

The International Geophysical Year (IGY), from July, 1957, through Dec., 1958, was planned to correspond with a period of maximum sunspot activity. As part of the IGY, 12 nations maintained 65 stations and operational facilities in Antarctica. The more difficult logistical problems of establishing inland bases were undertaken by the United States and the USSR. The American effort, termed “Operation Deep Freeze,” concentrated on the building of McMurdo Station, a major base of operations, on Ross Island; five other U.S. stations were established, including one at the South Pole. The Russians concentrated on E Antarctica, building Mirnyy, a station on the Queen Mary Coast, and three bases inland: Komsomolskaya, Vostok (at the South Magnetic Pole), and Sovetskaya. Britain maintained 14 stations, and Argentina, Chile, France, Australia, Belgium, Japan, Norway, South Africa, and New Zealand also participated.

From 1951 to 1958, Dr. Vivian Fuchs led the British Commonwealth Trans-Antarctic Expedition's traverse with tractors from the Weddell Sea to McMurdo Sound via the South Pole, conducting a seismic and magnetic profile en route. Long-distance flights by U.S. planes covered c.2,000,000 sq mi (5,180,000 sq km) in 1955–56. These and later support flights, the tractor journeys to build bases, and geophysical traverses by tracked vehicles during the IGY left little of the continent that had not been seen.

The Antarctic Treaty and Current Research

The success of the IGY effort led to the signing (1959) of the Antarctic Treaty by representatives of the 12 nations that had been involved in the IGY. The treaty prohibits military operations, nuclear explosions, and the disposal of radioactive wastes in Antarctica and provides for cooperation in scientific investigation and the exchange of scientific data. In 1991, 24 nations signed a protocol to the 1959 treaty barring for 50 years the exploration of Antarctica for oil or minerals. The accord also contained provisions covering wildlife protection, waste disposal, and marine pollution.

Of the 12 nations involved in the IGY, some have dropped their programs, others have suspended and then renewed operations; those that have been continually involved have reduced the size of their programs. Some stations have been closed, new ones have been opened, and old ones have had to be replaced. Eighteen nations now operate more than 30 year-round research stations on the continent; many more are operated in the summer. At McMurdo the United States has built a scientific village where people may be housed in summer and winter. From McMurdo other U.S. bases are supported by air. The National Science Foundation (NSF) finances the U.S. programs. Logistical support was in the hands of the U.S. navy until 1998, when air support was taken over by the New York Air National Guard; other functions (kitchen, stores, security, transportation) were contracted to a commercial organization. Mapping is done by the U.S. Geological Survey. Russian research has suffered from financial difficulties in recent years and was cut back in the 1990s.

In the early 1970s fossil finds and geological studies gave further support to the theory of continental drift. Sediment samples obtained by the Ocean Drilling Project (1985) off the coast of Queen Maud Land indicate ice sheets covered E Antarctica over 37 million years ago. Since the late 1980s scientists have researched seasonal ozone depletion, or “holes,” in the stratosphere above Antarctica, which allows harmful levels of ultraviolet radiation from the sun to reach the earth (see ozone layer); they have also queried whether the rising incidence of iceberg calving in E Antarctica and increased snowfall in W Antarctica are related to global warming. In 1997, through a joint effort of NASA and the Canadian Space Agency, the first radar satellite images of the entire continent were made. These revealed new information on Antarctica's network of ice streams as well as features lying far below the surface of the ice.

Bibliography

See T. Hatherton, ed., Antarctica (1965); L. B. Quartermain, South to the Pole (1967); H. G. R. King, The Antarctic (1969); L. O. Quam, ed., Research in the Antarctic (1971); K. J. Bertrand, Americans in Antarctica, 1775–1948 (1971); R. S. Lewis and P. M. Smith, ed., Frozen Future (1973); A. Parsons, ed., Antarctica: The Next Decade (1987); R. K. Headland, Chronological List of Antarctic Expeditions and Related Historical Events (1989); A. Gurney, Below the Convergence: Voyages toward Antarctica, 1699–1839 (1997) and The Race to the White Continent (2000).

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Antarctica

Area	14,000,000 km² (5,400,000 sq mi) 280,000 km² (108,000 sq mi) ice-free, 13,720,000 km² (5,297,000 sq mi) ice-covered
Population	~1000 (none permanent)
Government	governed by the Antarctic Treaty System - current executive secretary Johannes Huber
Partial Territorial claims (subject to the Antarctic Treaty System)	Argentina  Australia  Chile  France  New Zealand  Norway  United Kingdom
Reserved the right to make claims	Russia  United States
Internet TLD	.aq
Calling Code	Listed Here

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.^[1] 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."^[2] 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 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.^[3]

History

Main article: History of Antarctica

See also: List of Antarctica expeditions

Belief in the existence of a Terra Australis—a vast continent located in the far south of the globe to "balance" the northern lands of Europe, Asia and north Africa—had existed since the times of Ptolemy (first century CE), who suggested the idea in order to preserve the symmetry of all known landmasses in the world. Depictions of a large southern landmass were common in maps such as the early 16th century Turkish Piri Reis map. Even in the late 17th century, after explorers had found that South America and Australia were not part of the fabled "Antarctica," geographers believed that the continent was much larger than its actual size.

European maps continued to show this hypothetical land until Captain James Cook's ships, HMS Resolution and Adventure, crossed the Antarctic Circle on January 17, 1773, and once again in 1774.^[4] The first confirmed sighting of Antarctica can be narrowed down to the crews of ships captained by three individuals. According to various organizations (the National Science Foundation,^[5] NASA,^[6] the University of California, San Diego,^[7] and other sources^[8][9]), ships captained by three men sighted Antarctica in 1820: Fabian Gottlieb von Bellingshausen (a captain in the Russian Imperial Navy), Edward Bransfield (a captain in the British Navy), and Nathaniel Palmer (an American sealer out of Stonington, Connecticut). Von Bellingshausen saw Antarctica on January 27, 1820, three days before Bransfield sighted land, and ten months before Palmer did so in November 1820. On that day the two-ship expedition led by Von Bellingshausen and Mikhail Petrovich Lazarev reached a point within 32 km (20 miles) of the Antarctic mainland and saw ice fields there. The first documented landing on mainland Antarctica was by the American sealer John Davis in Western Antarctica on February 7, 1821, although some historians dispute this claim.

In December 1839, as part of the United States Exploring Expedition of 1838 – 1842 (conducted by the United States Navy) (sometimes called the "Ex. Ex.", or "the Wilkes Expedition"), the expedition sailed from Sydney, Australia into the Antarctic Ocean, as it was then known, and reported the discovery "of an Antarctic continent west of the Balleny Islands." That part of Antarctica was later named "Wilkes Land," a name it maintains to this day.

In 1841, explorer James Clark Ross passed through what is now known as the Ross Sea and discovered Ross Island (both of which were named for him). He sailed along a huge wall of ice that was later named the Ross Ice Shelf (also named for him). Mount Erebus and Mount Terror are named after two ships from his expedition: HMS Erebus and Terror.^[10] Mercator Cooper landed in Eastern Antarctica on January 26, 1853.^[11]

During an expedition led by Ernest Shackleton in 1907, parties led by T. W. Edgeworth David became the first to climb Mount Erebus and to reach the South Magnetic Pole.^[12] In addition, Shackleton himself and three other members of his expedition made several firsts in December 1908 – February 1909: they were the first humans to traverse the Ross Ice Shelf, the first to traverse the Transantarctic Mountain Range (via the Beardmore Glacier), and the first to set foot on the South Polar Plateau. On December 14, 1911, a party led by Norwegian polar explorer Roald Amundsen from the ship Fram became the first to reach the geographic South Pole, using a route from the Bay of Whales and up the Axel Heiberg Glacier.^[13] One month later, the ill-fated Scott Expedition reached the pole.

Richard Evelyn Byrd led several voyages to the Antarctic by plane in the 1930s and 1940s. He is credited with implementing mechanized land transport on the continent and conducting extensive geological and biological research.^[14] However, it was not until October 31, 1956 that anyone set foot on the South Pole again; on that day a U.S. Navy group led by Rear Admiral George Dufek successfully landed an aircraft there.^[15]

Geography

Main article: Geography of Antarctica

Centered asymmetrically around the South Pole and largely south of the Antarctic Circle, Antarctica is the southernmost continent and is surrounded by the Southern Ocean. (Alternatively, it may be considered to be surrounded by the southern Pacific, Atlantic, and Indian Oceans, or by the southern waters of the World Ocean.) It covers more than 14 million km² (5.4 million sq mi), making it the fifth-largest continent, about 1.3 times larger than Europe. The coastline measures 17,968 km (11,160 miles) and is mostly characterized by ice formations, as the following table shows:

Coastal types around Antarctica (Drewry, 1983)

Type	Frequency
Ice shelf (floating ice front)	44%
Ice walls (resting on ground)	38%
Ice stream/outlet glacier (ice front or ice wall)	13%
Rock	4%
Total	100%

Antarctica 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, a sheet of ice averaging at least 1.6 km (1.0 mi) thick. The continent has approximately 90% of the world's ice (and thereby approximately 70% of the world's fresh water). If all of this ice were melted, sea levels would rise about 61 meters (200 feet).^[16] In most of the interior of the continent precipitation is very low, down to  millimeters ( in) per year; 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 4,892 meters (16,050 ft), is located in the Ellsworth Mountains. Although Antarctica is home to many volcanoes, only Mount Erebus is known to be active. Located on Ross Island, Erebus is the southernmost active volcano. There is 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.^[17] 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.^[18]

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 500,000 to one million years. There is some evidence, in the form of ice cores drilled to about  meters ( ft) above the water line, that Vostok's waters may contain microbial life. The sealed, frozen surface of the lake shares similarities with Jupiter's moon Europa. If life is discovered in Lake Vostok, this would strengthen the argument for the possibility of life on Europa.^[19][20]

See also: Extreme points of Antarctica, Antarctic territories, and List of Antarctic and sub-Antarctic islands

Geology

Main article: Geology of Antarctica

Geological history and paleontology

More than 170 million years ago, Antarctica was part of the supercontinent Gondwana. Over time, Gondwana gradually broke apart and Antarctica as we know it today was formed around 25 million years ago.

Paleozoic era (540-250 Mya)

During the Cambrian period, Gondwana had a mild climate. West Antarctica was partially in the northern hemisphere, and during this period large amounts of sandstones, limestones and shales were deposited. East Antarctica was at the equator, where sea-floor invertebrates and trilobites flourished in the tropical seas. By the start of the Devonian period (416 Mya), Gondwana was in more southern latitudes and the climate was cooler, though fossils of land plants are known from this time. Sand and silts were laid down in what is now the Ellsworth, Horlick and Pensacola Mountains. Glaciation began at the end of the Devonian period (360 Mya), as Gondwana became centered around the South Pole and the climate cooled, though flora remained. During the Permian period, the plant life became dominated by fern-like plants such as Glossopteris, which grew in swamps. Over time these swamps became deposits of coal in the Transantarctic Mountains. Towards the end of the Permian period, continued warming led to a dry, hot climate over much of Gondwana.^[21]

Mesozoic era (250-65 Mya)

As a result of continued warming, the polar ice caps melted and much of Gondwana became a desert. In East Antarctica, the seed fern became established, and large amounts of sandstone and shale were laid down at this time. The Antarctic Peninsula began to form during the Jurassic period (206-146 Mya), and islands gradually rose out of the ocean. Ginkgo trees and cycads were plentiful during this period, as were reptiles such as Lystrosaurus. In West Antarctica, coniferous forests dominated through the entire Cretaceous period (146-65 Mya), though Southern beech began to take over at the end of this period. Ammonites were common in the seas around Antarctica, and dinosaurs were also present, though only two Antarctic dinosaur species (Cryolophosaurus, from the Hanson Formation, and Antarctopelta) have been described to date. It was during this period that Gondwana began to break up.

Gondwana breakup (160-23 Mya)

Africa separated from Antarctica around 160 Mya, followed by the Indian subcontinent, in the early Cretaceous (about 125 Mya). About 65 Mya, Antarctica (then connected to Australia) still had a tropical to sub