ANTARCTICA

fifth in size among the world's continents, lying concentrically about the South Pole, with a landmass almost wholly covered by a vast ice sheet, averaging about 6,500 feet (2,000 m) thick. It is roughly divided into two subcontinents, the larger, East Antarctica, consisting mainly of a high, ice-covered plateau, and West Antarctica, consisting largely of an archipelago of mountainous islands covered and bonded together by ice. The continent is about 5,500,000 square miles (14,200,000 square km) in area and is important as a region of international cooperation in scientific research. The southern portions of the Atlantic, Pacific, and Indian oceans form the Antarctic Ocean around Antarctica. fifth in size among the world's continents. Its landmass is almost wholly covered by a vast ice sheet. Lying almost concentrically around the South Pole, Antarcticathe name of which means opposite to the Arcticis the southernmost continent, a circumstance that has had momentous consequences for all aspects of its character. It covers about 5.5 million square miles (14.2 million square kilometres), and would be essentially circular except for the outflaring Antarctic Peninsula, which reaches toward the southern tip of South America (some 600 miles [970 kilometres] away), and for two principal embayments, the Ross Sea and the Weddell Sea. These deep embayments of the southernmost Pacific and Atlantic oceans make the continent somewhat pear-shaped, dividing it into two unequal-sized parts. The larger is generally known as East Antarctica because most of it lies in east longitudes. The smaller, wholly in west longitudes, is generally called West Antarctica. East and West Antarctica are separated by the 1,900-mile-long Transantarctic Mountains. Whereas East Antarctica consists largely of a high, ice-covered plateau, West Antarctica consists of an archipelago of mountainous islands covered and bonded together by ice. The continental ice sheet contains approximately 7 million cubic miles (30 million cubic kilometres) of ice, representing about 90 percent of the world's total. The average thickness is about 6,500 feet (2,000 metres). Many parts of the Ross and Weddell seas are covered by ice shelves, or ice sheets floating on the sea. These shelvesthe Ross Ice Shelf and the Ronne and Filchner ice shelvestogether with other shelves around the continental margins, constitute about 10 percent of the area of Antarctic ice. Around the Antarctic coast, shelves, glaciers, and ice sheets continually calve, or discharge, icebergs into the seas. Because of this vast ice, the continent supports only a primitive indigenous population of cold-adapted land plants and animals. The surrounding sea is as rich in life as the land is barren. With the decline of whaling and sealing, the only economic base in the past, Antarctica now principally exports the results of scientific investigations that lead to a better understanding of the total world environment. The present scale of scientific investigation of Antarctica began with the International Geophysical Year (IGY) in 195758. Although early explorations were nationalistic, leading to territorial claims, modern ones have come under the international aegis of the Antarctic Treaty. This treaty, which was an unprecedented landmark in diplomacy when it was signed in 1959 by 12 nations, preserves the continent for nonmilitary scientific pursuits. Antarctica, the most remote and inaccessible continent, is no longer the most unknown. All its mountain regions have been mapped and visited by geologists, geophysicists, glaciologists, and biologists. Mapping data can now be obtained by satellite rather than by the theodolites of surveyors. Many hidden ranges and peaks are known from geophysical soundings of the Antarctic ice sheets. By using radio-echo sounding instruments, systematic aerial surveys of the ice-buried terrains can be made; some of these are almost as well mapped as the exposed ones. The ice-choked and stormy seas around Antarctica long hindered exploration by wooden-hulled ships. No lands break the relentless force of the prevailing west winds as they race clockwise around the continent, dragging westerly ocean currents along beneath. The southernmost parts of the Atlantic, Pacific, and Indian oceans converge into a cold, oceanic water mass with singularly unique biologic and physical characteristics. Early penetration of this Antarctic (or Southern) Ocean, as it has been called, in the search for fur seals led in 1820 to the discovery of the continent. Icebreakers and aircraft now make access relatively easy, although still not without hazard in stormy conditions. Many tourists have visited Antarctica, and it seems likely that, at least in the short run, scenic resources have greater potential for economic development than do mineral and biological resources. The term Antarctic regions refers to all areasoceanic, island, and continentallying in the cold Antarctic climatic zone south of the Antarctic Convergence, an important boundary with little seasonal variability, where warm subtropical waters meet and mix with cold polar waters. For legal purposes of the Antarctic Treaty, the arbitrary boundary of latitude 60 S is used. The familiar map boundaries of the continent known as Antarctica, defined as the South Polar landmass and all its nonfloating grounded ice, are subject to change with future changes of climate. The continent was ice-free during most of its lengthy geologic history, and there is no reason to believe it will not become so again in the probably distant future. Additional reading General works John Stewart, Antarctica: An Encyclopedia, 2 vol. (1990), emphasizes history and geography but includes entries on geologic features and scientific topics, as well as a lengthy, annotated bibliography. The most complete guide to literature about the Antarctic is the U.S. Library of Congress, Antarctic Bibliography (annual). Fred G. Alberts (compiler and ed.), Geographic Names of the Antarctic (1981), contains a compilation and derivation of Antarctica's place names up to 1979, with coordinates, details of discovery, and for whom each was named. E.I. Tolstikov, Atlas Antarktiki, 2 vol. (196669), is a comprehensive map collection in Russian, useful especially when complemented by the translation of legend matter and explanatory text from vol. 1, published as Atlas of Antarctica, a special issue of Soviet Geography: Review & Translation, vol. 8, no. 56 (MayJune 1967). Louis O. Quam (ed.), Research in the Antarctic (1971); Richard S. Lewis and Philip M. Smith (eds.), Frozen Future: A Prophetic Report from Antarctica (1973); and D.W.H. Walton (ed.), Antarctic Science (1987), contain review articles by leading experts on most subjects of research, the latter two also with articles on resources, economics, politics, and the outlook for the future. Richard Fifield, International Research in the Antarctic (1987), introduces the various types of research undertaken in Antarctica. A general review, Raymond Priestley, Raymond J. Adie, and G. De Q. Robin (eds.), Antarctic Research (1964), emphasizes British scientific achievements, particularly in the Antarctic Peninsula and Scotia Arc. Semitechnical to nontechnical reviews of current projects and exploration are in summary articles in the Antarctic Journal of the United States (quarterly). A general nontechnical review of earlier research is provided in the still-useful work by H.G.R. King, The Antarctic (1969). G.E. Fogg, A History of Antarctic Science (1992), traces the development of scientific inquiry in Antarctica. Antarctic Science (quarterly) covers all fields of scientific research on the continent. American Geographical Society of New York, Antarctic Map Folio Series, 19 vol. (196475); and American Geophysical Union, Antarctic Research Series (irregular), provide modern maps and technical accounts of all phases of the research programs. F.M. Auburn, Antarctic Law and Politics (1982), provides a comprehensive discussion of the legal aspects of the Antarctic Treaty, jurisdictional problems of crime, ecology, and tourism. Gillian D. Triggs (ed.), The Antarctic Treaty Regime: Law, Environment, and Resources (1987), discusses current aspects of issues raised by the Antarctic Treaty. Anthony Parsons, Antarctica: The Next Decade (1987), addresses the history of the Antarctic Treaty and its future as well as current and projected uses of the continental region. Physical geography W.N. Bonner and D.W.H. Walton (eds.), Antarctica (1985); and R.M. Laws (ed.), Antarctic Ecology, 2 vol. (1984), discusses the continent's physical environment, fauna, flora, land and sea ecology, conservation, and exploitation. I.B. Campbell and G.G.C. Claridge, Antarctica: Soils, Weathering Processes, and Environment (1987), provides a summary of recent research. Geologic record Raymond J. Adie (ed.), Antarctic Geology (1964), and Antarctic Geology and Geophysics (1972); Campbell Craddock (ed.), Antarctic Geoscience (1982); R.L. Oliver, P.R. James, and J.B. Jago (eds.), Antarctic Earth Science (1983); and M.R.A. Thomson, J.A. Crame, and J.W. Thomson (eds.), Geological Evolution of Antarctica (1991), are records of international symposia describing Earth science research by many nations. J.C. Behrendt and C.R. Bentley, Magnetic and Gravity Maps of the Antarctic (1968); and Campbell Craddock et al., Geologic Maps of Antarctica (196970), provide maps and texts, the latter work covering most mountain regions at a 1:1,000,000 scale. Other works on the geology of Antarctica are Edmund Stump (ed.), Geological Investigations in Northern Victoria Land (1986); and W.E. LeMasurier and J.W. Thomson (eds.), Volcanoes of the Antarctic Plate and Southern Oceans (1990). Scripps Institution of Oceanography, Initial Reports of the Deep Sea Drilling Project, vol. 28 (1975), 35 (1976), and 36 (1977), contain results of drilling by the Glomar Challenger in Antarctic waters. Results of drilling by the JOIDES Resolution are contained in Proceedings of the Ocean Drilling Program: Scientific Results, especially vol. 113 (1990), from the Weddell Sea, vol. 114 (1991), from subantarctic regions and the Falkland Islands, and vol. 119 (1991), from the Kerguelen Plateau. A.L. Graham and John O. Annexstad, Antarctic Meteorites, Antarctic Science, 1(1):314 (1989), reviews the findings and origins of meteorites in Antarctica. Many details of Antarctic meteorite investigations are also reported in volumes of the Proceedings of the NIPR Symposium on Antarctic Meteorites (annual), published by the National Institute of Polar Research. Climate Morton J. Rubin (ed.), Studies in Antarctic Meteorology (1966); S. Orvig (ed.), Climates of the Polar Regions (1970); W.S. Weyant, The Antarctic Atmosphere: Climatology of the Surface Environment (1967); and W. Schwerdtfeger, Weather and Climate of the Antarctic (1984), include topical studies and a few general review articles. Glaciers and seas Malcolm Mellor (ed.), Antarctic Snow and Ice Studies (1964); and A.P. Crary (ed.), Antarctic Snow and Ice Studies II (1971), are collections mainly of topical studies of greatly varied scope. John Mercer, Glaciers of the Antarctic (1967), provides a general review of Antarctica's glaciers. Stephen J. Pyne, The Ice (1986), investigates Antarctic ice and also describes other aspects of the region, including exploration, literature, and art. A.L. Gordon and R.D. Goldberg, Circumpolar Characteristics of Antarctic Waters (1970); and Joseph L. Reid and Dennis E. Hayes (eds.), Antarctic Oceanology, 2 vol. (197172), describe features of South Polar water masses, their currents, and their interactions with subtropical and subantarctic waters, as well as of the ocean floor and sediment carpet. George Deacon, The Antarctic Circumpolar Ocean (1984), includes a summary of early discoveries by explorers, sealers, and whalers and a review of modern knowledge of Antarctic waters. Plant and animal life Eric Hosking and Bryan Sage, Antarctic Wildlife (1982), is an authoritative discussion of the fauna of Antarctica. Biology of the Antarctic Seas (irregular), contains technical accounts of Antarctic sea life; a more popular summary is Robert C. Murphy, The Oceanic Life of the Antarctic, Scientific American, 207(3):186194 (September 1962). Technical accounts of terrestrial life are in J. Linsley Gressitt (ed.), Entomology of Antarctica (1967); and S.W. Greene et al., Terrestrial Life of Antarctica (1967); a nontechnical review is provided by George A. Llano, The Terrestrial Life of the Antarctic, Scientific American, 207(3):212218 (September 1962). Oliver L. Austin, Jr. (ed.), Antarctic Bird Studies (1968), is a technical publication; whereas John Sparks and Tony Soper, Penguins, 2nd ed. (1987), comprehensively but nontechnically describes the characteristic flightless birds of subantarctic and Antarctic coasts. George Gaylord Simpson, Penguins: Past and Present, Here and There (1976), is an authoritative, popularly written account of penguins and their fossil record. David G. Campbell, The Crystal Desert (1992), evocatively portrays the natural history of the Antarctic Peninsula and the South Shetland Islands. Economic resources J.F. Lovering and J.R.V. Prescott, Last of Lands: Antarctica (1979), examines resources, discovery and exploration, political geography, and future prospects. Barbara Mitchell, Frozen Stakes: The Future of Antarctic Minerals (1983), presents an account of polar politics and minerals and discusses possible regimes for regulating resource development. Francisco Orrego Vicua (ed.), Antarctic Resources Policy: Scientific, Legal, and Political Issues (1983), contains reports from the first symposium of its kind, a meeting of scientists, diplomats, and international lawyers at an Antarctic scientific station. More recent works are Deborah Shapley, The Seventh Continent: Antarctica in a Resource Age (1985); and John F. Splettstoesser and Gisela A.m. Dreschoff (eds.), Mineral Resources Potential of Antarctica (1990). History A thorough general account is in C. Hartley Grattan, The Southwest Pacific Since 1900 (1963). An interesting and thorough history is Walter Sullivan, Quest for a Continent (1957). Kenneth J. Bertrand, Americans in Antarctica, 17751948 (1971), recounts early U.S. explorations. Antarctica: Great Stories from the Frozen Continent (1985), offers a readable and profusely illustrated account of explorers from many nations, as well as a description of the physical environment. A complete list of expeditions, claims, treaties, discoveries, and meetings is found in R.K. Headland, Chronological List of Antarctic Expeditions and Related Historical Events (1989). Arthur B. Ford History A great many nations, large and small, played important roles in the discovery and exploration of Antarctica. Who first saw the continent is controversial. The Russian expedition leader Fabian Gottlieb von Bellingshausen, the Englishman Edward Bransfield, and the American Nathaniel Palmer all claim first sightings in 1820: Bellingshausen sighted a shelf edge of continental ice on January 20; two days later Bransfield caught sight of land that the British later considered to be a mainland part of the Antarctic Peninsula; and on November 18 Palmer unequivocally saw the mainland-peninsula side of Orleans Strait. About AD 650, however, long before European geographers of the Middle Ages and the Renaissance were to conjecture about the mythical Terra Australis, Maori legend tells of a New Zealand Polynesian war canoe, under the command of one Ui-te-Rangiora, that sailed at least as far south as the frozen ocean. The legendary vast size of the continent shrank to nearly its present one when in 177275 the Englishman James Cook circumnavigated the globe in high southern latitude, proving that Terra Australis, if it existed at all, lay somewhere beyond the ice packs that he discovered between about 60 and 70 S. Early scientific progress The period from the 1760s to about 1900 was one dominated by exploitation of Antarctic and subantarctic seas, particularly along Scotia Ridge. Sealing vessels of many nations, principally American and British but including Argentine, Australian, South African, New Zealand, German, and Norwegian, participated in hunting that eventually led to near extinction of the southern fur seal. Many also hunted whales, and the less profitable whaling industry climaxed following World War I after the decline of sealing. Among the few geographic and scientific expeditions that stand out during this period are those of Bellingshausen, commanding the Russian ships Vostok and Mirny, in the first close-in circumnavigation of Antarctica in 181921; Bransfield, on a British expedition charting part of the Antarctic Peninsula in 181920; Dumont d'Urville, on a French expedition in 183740, when Adlie Land was discovered and claimed for France; Charles Wilkes, on a U.S. naval expedition in 183842 that explored a large section of the East Antarctic coast; and James Clark Ross, on a British expedition in 183943 that discovered the Ross Sea and Ross Ice Barrier (now called Ross Ice Shelf) as well as the coast of Victoria Land. Physical geography The land Geologic record Antarctica and continental drift The geologic evolution of Antarctica has followed a course similar to that of the other southern continents. The earliest chapters in Antarctica's rather fragmentary record extend far back, perhaps as much as 3 billion years, into early Precambrian time. Similarity in patterns of crustal and biological evolution in the southern continents can be traced back some 150 million years, and evolutionary courses began to diverge conspicuously by about 70 million years ago, or the early Cenozoic Era. Plant and animal migration routes that apparently had interconnected all the southern continents were largely cut off by the outset of the Cenozoic. Antarctica became isolated at a time when land mammals diversified and flourished elsewhere, populating all the other continents of the world. Antarctica had long been thought to be a migratory path for marsupials moving between southern continents in early Cenozoic time. But documentation for the theory was not discovered until 1982, when the first mammal remains, a marsupial fossil, were found on Seymour Island in the Weddell Sea. The subsequent growth of Antarctica's ice sheets cut off any further migrations by land animals. Now bathed by polar ice, Antarctica has abundant fossil evidence that its climate and terrain at one time supported far more populous flora and fauna than today's few seedless plants and primitive insects. Much of Antarctica was densely forested in Mesozoic times (245 to about 66 million years ago), dominated by southern conifers of podocarps and araucarias, with undergrowth of rain-forest-type ferns. Angiosperm trees, particularly the southern beech, Nothofagus, appeared during the Cretaceous Period (144 to roughly 66 million years ago) and lingered in places until Pliocene time (5.3 to 1.6 million years ago) as Antarctica drifted poleward, cooled, and became glaciated. Remains of luxuriant extinct floras, as well as fossils of Mesozoic reptiles and amphibians that have been discovered, compare so closely to those of other southern continents that many geologists have postulated former contiguity of these lands in a single, giant continent called Gondwanaland. Continental stratigraphic evidence and the dating of seafloors seem to indicate that the supercontinent broke apart along Jurassic rift faults 180 to 160 million years ago, and fragments such as Africa and Australia separated from Antarctica in Jurassic to Cretaceous and early Cenozoic times. Early stages of rifting were marked by immense outpourings of plateau lavas (Kirkpatrick Basalt, on Mount Kirkpatrick) and by related sill intrusions (Ferrar Dolerites) across Antarctica, including one of the world's largest layered gabbroic igneous complexes, the Dufek intrusion, in the Pensacola Mountains. Modern theory ties mobile zones to the interaction and jostling of immense crustal plates (see plate tectonics). Modern plate boundaries may be far different from ancient ones presumably marked by old fold belts. Ancient Antarctic mobile belts, such as are followed by today's Transantarctic Mountains, terminate at continental margins abruptly, as if sliced off, and seemingly reappear in other lands across young ocean basins. Much research has been concentrated on attempting to match intercontinentally the detailed structure of opposed coasts, such as between Antarctica and Australia, in an effort to learn whether they had been actually connected before the latest cycle of crustal spreading from intervening mid-oceanic ridges. Similarities between ancient mobile belts now suggest to some geologists that Antarctica may even have been connected to southwestern North America more than 600 million years ago, in late Precambrian time; this came to be known as the SWEAT (Southwest U.S.East Antarctica) hypothesis in the early 1990s.