PACIFIC OCEAN

body of saltwater extending from the Antarctic region in the south to the Arctic in the north and lying between the continents of Asia and Australia on the west and North and South America on the east. Of the three oceans that extend northward from the Antarctic continent, the Pacific, occupying about a third of the surface of the terrestrial globe, is by far the largest. Its area, excluding adjacent seas, encompasses about 63,800,000 square miles (165,250,000 square kilometres). It has double the area and more than double the water volume of the Atlanticthe next largest division of the hydrosphereand its area more than exceeds that of the whole land surface of the globe. The Pacific Ocean stretches from the shores of Antarctica to the Bering Strait through 135 of latitude, or for 9,600 miles (15,500 kilometres). Its greatest longitudinal extent measures some 12,000 miles along the parallel of 5 N, between the coasts of Colombia in South America and the Malay Peninsula in Asia. The mean depth of the Pacific (excluding adjacent seas) is 14,040 feet (4,280 metres), and its greatest known depth is 36,201 feet (11,034 metres)in the Mariana Trenchalso the greatest depth found in any ocean. The Pacific and Arctic systems mingle their waters in the Northern Hemisphere at the shallow Bering Strait, and in the Southern Hemisphere the Pacific and Atlantic mix in the relatively narrow Drake Passage between Tierra del Fuego in South America and Graham Land in Antarctica. The separation between the Pacific and Indian oceans is less distinct, but generally it is considered to lie along the line of islands extending eastward from Sumatra, through Java to Timor, thence across the Timor Sea to Cape Londonderry in Australia. To the south of Australia the boundary extends across the Bass Strait and thence from Tasmania to Antarctica. Because of the pattern of major mountain systems of the globe, a relatively small proportion (one-seventh) of the total continental drainage enters the Pacifici.e., a total drainage area of less than about three times the total area of Australia. Of the rivers that drain into the Pacific, those of China and Southeast Asia are of the greatest importance; the basins of these rivers support more than one-quarter of the world's population. The eastern boundary of the Pacific is associated with the American Cordilleran mountain system, which stretches from Alaska in the north to Tierra del Fuego in the south. Except for its extreme northern and southern sections, which are characterized by fjords and their numerous off-lying islands, and except for the deeply indented Gulf of California, the coastal boundary is relatively regular and the continental shelf narrow. The western, or Asiatic, coastal boundary, in contrast, is irregular. Although the mountain systems there lie roughly parallel to the coast, as they do on the eastern Pacific coastlands, the western Pacific is noted for its many marginal seas. From north to south they include the Bering Sea, the Sea of Okhotsk, the Sea of Japan, the Yellow Sea, the East China Sea, and the South China Sea. Their eastern boundaries are formed by southward-jutting peninsulas or island arcs or both. It is of oceanographic significance that the great rivers of eastern Asiaincluding the Amur, the Huang Ho (Yellow River), the Yangtze, the Hsi and Pearl, and the Mekongenter the Pacific indirectly by way of the marginal seas. This article treats the physical and human geography of the Pacific Ocean. For discussion of the physical and chemical oceanography and marine geology of the Pacific, see ocean; for discussion of Pacific peoples and cultures, see Pacific Islands. For further references, see the Index. body of salt water extending from the Antarctic region in the south to the Arctic in the north and lying between the continents of Asia and Australia on the west and North and South America on the east. The Pacific Ocean occupies about one-third of the surface of the Earth and is by far the largest of the world's oceans. Its area, excluding adjacent seas, encompasses approximately 63,800,000 square miles (165,250,000 square km). It has twice the area and more than twice the water volume of the Atlanticthe next-largest ocean. Its area exceeds that of the whole land surface of the globe, Antarctica included. The mean depth of the Pacific (excluding adjacent seas) is 14,040 feet (4,280 m). The western Pacific is noted for its many peripheral seas. From north to south they include the Bering Sea, the Sea of Okhotsk, the Sea of Japan, the Yellow Sea, the East China Sea, and the South China Sea. The great rivers of eastern Asiaincluding the Amur, the Huang Ho, the Yangtze, the Hsi, and the Mekongenter the Pacific indirectly by way of peripheral seas. To the east of the meridian of 150 W, the relief of the Pacific Ocean floor is considerably less pronounced than it is to the west. Submerged oceanic ridges found at depths of less than 2,000 feet (600 m) rise at points to form several archipelagos in the western Pacific. These ridges include the Aleutian ridge in the northwestern Pacific; the series of ridges extending southward through the Kurils, Bonin, the Marianas, Yap, and Palau (Belau); those extending eastward from Palau, including the Bismarck, the Solomons, and Santa Cruz ridges; and finally the ridges extending southward from the Samoan islands, those of Tonga, Kermadec, Chatham, and Macquarie. Water temperatures in the northern Pacific tend to be higher than those in the southern Pacific because the ratio of land to sea areas is larger in the north than in the south and because the ice-clad continent of Antarctica influences water temperature. The Pacific waters within the belt of calms and variable winds near the Equator have lower salinities than those in the trade-wind belts. The most important influence on the vertical circulation of the Pacific is the cold water generated around the Antarctic continent. This dense circumpolar water sinks and then spreads northward to form the bottom layer of the greater part of the Pacific. Cold, deep water flows northward in the western Pacific in a relatively well-defined current from the vicinity of Antarctica to Japan. Branches from this deep mainstream convey cold water eastward and then poleward in both hemispheres. Deepwater circulation is influenced by the descent of surface water at zones of convergence of neighbouring water flows. In the zone known as the Pacific Tropical Convergence, water sinks to a depth of about 300 feet (91 m) before it spreads laterally. The Pacific Subtropical convergences are located between the parallels of 35 and 40 N and S. Water that sinks at the convergences spreads laterally at increasing depths as the distance from the Equator increases. The most important convergence in the Pacific is the Antarctic Convergence, which lies about 55 to 65 south in the southern Pacific. Additional reading General works Comprehensive summaries of information about the Pacific Ocean and its seas are found in Alastair Couper (ed.), The Times Atlas and Encyclopaedia of the Sea, 2nd ed. (1989), with excellent maps and text covering the ocean environment, resources, ocean trade, strategic use of the seas, law of the sea, problems of pollution, and scientific research; and Martyn Bramwell (ed.), The Rand McNally Atlas of the Oceans (1977, reprinted 1987), with specific sections on bathymetry, structural geology, reefs and islands circulation, mineral resources, and living resources. See also M. Grant Gross, Oceanography, a View of the Earth, 5th ed. (1990), offering topical rather than regional coverage, but with numerous examples based on the Pacific Ocean; Rhodes W. Fairbridge (ed.), The Encyclopedia of Oceanography (1966), with articles on the Pacific and its seas; and the articles pertaining to the Pacific in the periodical Oceanus (quarterly), particularly vol. 32, no. 4 (Winter 1989/90), which is devoted to the Pacific. Physical environment Otis W. Freeman, Geography of the Pacific (1951), surveys the physical features of the ocean; and Alan E.M. Nairn and Francis G. Stehli (eds.), The Ocean Basins and Margins, vol. 7, The Pacific Ocean, 2 vol. (198588), is comprehensive and highly detailed. Zvi Ben-Avraham (ed.), The Evolution of the Pacific Ocean Margins (1989); and H.W. Menard, Marine Geology of the Pacific (1964), explore marine geology and geophysics. See also Bruno Wauthy, Physical Ocean Environment in the South Pacific Commission Area (1986), a short but valuable summary of the oceanography of the central and South Pacific, prepared as a regional report under the United Nations Environment Programme. Economic aspects A detailed review of Pacific Ocean minerals, including those contained in seawater and those on or beneath the ocean floor, is offered in G.P. Glasby, Marine Minerals in the Pacific, Oceanography and Marine Biology 24:164 (1986). Information on economic and other resources of the ocean areas is also found in such works as Asia & Oceania, vol. 4 of the Worldmark Encyclopedia of the Nations, 7th ed., 5 vol. (1988); Fillmore C.F. Earney, Marine Mineral Resources (1990); and FAO Yearbook: Fishery Statistics. John P. Craven, The Management of Pacific Marine Resources (1982), offers well-written, scholarly coverage of resources and their management, or in some cases mismanagement; details on fisheries, shipping, scientific research, and maritime law are given in Edward Miles et al., The Management of Marine Regions: The North Pacific (1982); and Peter N. Nemetz (ed.), The Pacific Rim (1987), studies commerce, economic conditions, foreign investments, and resources in the Pacific Rim countries. Another valuable overview of economic conditions, international business enterprises, marine resources, and regionalism is Endel-Jacob Kolde, The Pacific Quest: The Concept and Scope of an Oceanic Community (1976); and Henry S. Albinski et al., The South Pacific (1989), studies the New Pacific and the economic, political, and social problems of island nations that have achieved independence since World War II. Study and exploration Andrew Sharp, The Discovery of the Pacific Islands (1960, reprinted 1985), summarizes the work of 121 explorers of the area and their contributions to charting the Pacific. J.C. Beaglehole, The Exploration of the Pacific, 3rd ed. (1966), and The Life of Captain James Cook (1974), are classics on the subject. Ernest S. Dodge, Beyond the Capes: Pacific Exploration from Captain Cook to the Challenger, 17761877 (1971), provides a thorough coverage of this important period. John E. Bardach Joseph R. Morgan