occupational training See employee training
ocean Large, continuous body of salt water. Ocean covers nearly 71% of the Earth’s surface and is divided into major oceans and smaller seas. The three principal oceans, the Pacific, Atlantic, and Indian, are largely delimited by land and submarine topographic boundaries. All are con¬ nected to what is sometimes called the Southern Ocean, the waters encir¬ cling Antarctica. Important marginal seas, primarily in the Northern Hemisphere, are partially enclosed by landmasses or island arcs. The larg¬ est are the Arctic Ocean and adjacent seas, Caribbean and adjacent waters, Mediterranean, Bering Sea, Sea of Okhotsk, Yellow and China Seas, and Sea of Japan.
ocean current Horizontal and vertical circulation system of ocean waters, produced by gravity, wind friction, and water density variation. Coriolis forces cause ocean currents to move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere and deflect them about 45° from the wind direction. This movement creates distinc¬ tive currents called gyres. Major ocean currents include the Gulf Stream-
North Atlantic-Norway Current in the Atlantic Ocean, the Peru (Humboldt) Current off South America, and the West Australia Current.
ocean liner Large merchant ship that visits designated ports on a regu¬ lar schedule, carrying whatever cargo and passengers are available on the date of sailing. The first liners were operated in the North Atlantic, nota¬ bly by Samuel Cunard of Britain, beginning in 1840. Their heyday lasted from the late 19th to the mid-20th century. Many were extraordinarily luxurious. Among the most famous were Cunarders such as the Mauret¬ ania and the Queen Mary, the German Vaterland (later renamed Levia¬ than), for many years the largest ship afloat; the ill-fated Titanic, and the United States. Their reign ended in the 1960s with the rise of jet travel, but liners ranging from cruise ships to refrigerated cargo ships continued to sail.
ocean perch See redfish
Oceania \,o-she-'a-ne-3\ Collective name for the islands scattered throughout most of the Pacific Ocean. The term especially refers to islands of the central and southern Pacific, including those of Micronesia, Melane¬ sia, and Polynesia; New Zealand is often included and sometimes Austra¬ lia. In its most restricted sense, excluding Australia but including Papua New Guinea, Oceania includes more than 10,000 islands and has a land area of about 317,000 sq mi (821,000 sq km). See map on following page.
Oceanic \,o-she-'a-nik\ arts Literary, performing, and visual arts of the Pacific islands of Oceania, including Australia as well as Polynesia, Melanesia, and Micronesia. Their isolation and wide range of environ¬ mental conditions led to the development of a rich variety of artistic styles. Religion and ritual strongly influence every aspect of Oceanic life, and their association with the arts is especially close. Religious symbolism infuses not only the objects, dances, and speeches used in ritual but also the materials and tools used to create them. Oceanic literature includes both complex oral traditions and a more modern body of works written primarily in English. The traditional oral transmission of literature neces¬ sitated rhythmic cadences and stock formulas to aid memory. Favoured subjects are tales of the gods and spirits and creation myths. Musical styles are multitudinous, though all regions, with some Melanesian exceptions, emphasize vocals using instruments to produce supranormal voices. Con¬ sequently most instruments are technically crude though often elaborately decorated in keeping with their extramusical function as gifts and cult objects. Polynesian song and dance is rooted in societal structure, and chants praise chiefs or high-ranking guests while the dancers’ movements
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narrate rather than act out the meaning. Australian and Melanesian dance has a historical function describing the activities of gods and ancestors—in the latter instance, dancers don elaborate costumes and masks. In all the islands the significant movements are made with the upper half of the body, while the feet merely keep time. The visual arts display ingenious use of environmental possibilities: a staggering range of materials are used, often in collage-style combination. Wood is the main artistic medium; secondary materials included clay, shell, and stone. Extant works include wooden masks, clubs, and religious effigies; carved stone sculptures; feather cloaks and helmets; and bark cloth stenciled with bold, dense geometric designs The most famous monuments of Oceanic art are the gargantuan stone figures of Easter Island. With the arrival of European colonists, the arts in these regions began to reflect European traditions and styles. See also bisj pole.
oceanic \,o-she-'a-nik\ plateau or submarine plateau Large sub¬ marine elevation rising sharply at least 660 ft (200 m) above the sur¬ rounding seafloor and having an extensive, relatively flat or gently tilted summit. Most plateaus are steplike interruptions of the continental slopes. Some, however, occur well beyond the continental margins. They stand alone, high above the surrounding seafloor, and are believed to be frag¬ ments of continents that were isolated during continental drift and sea¬ floor SPREADING.
Oceanic religions Non-Christian religions practiced in Oceania. Tra¬ ditional Melanesian religions, which are giving way under the pressures of Christianity and capitalism, hold that ancestral ghosts and other spirits are participants in daily life. Their presence and effects are manifested in dreams, in divination, and in human successes and failures. Magic is widely practiced, and sorcery is seen as the major cause of death and ill¬ ness. The traditional religions of Micronesia, which have largely died out, recognized several high gods and many other spirits, including the spirits of ancestors and the dead. Magic played an important role. In Polynesia, each of the gods, whether high or local, had its own ritual requirements, and schools of priests were often required to carry them out. All things were believed to possess mana, which had to be protected by complicated rules and taboos. The Polynesians often offered human sacrifices on important occasions, such as the formal investiture of a priest or chief. With the introduction of modem goods, the peoples of all these islands became susceptible to cargo cults.
oceanic ridge Continuous, submarine mountain chain extending approximately 50,000 mi (80,000 km) through all the world’s oceans, separating them into distinct basins. The main ridge extends down the middle of the Atlantic Ocean, passes between Africa and Antarctica, turns north to the Indian Ocean, then continues between Australia, New Zealand, and Antarctica and across the Pacific basin to the mouth of the Gulf of California. Lateral ridges extend from islands on the axis of the oceanic ridge to coasts of adjacent continents. The oceanic ridge system is the largest feature of the Earth’s surface after the continents and the ocean basins themselves; it is explained by the theory of plate tectonics as a boundary between diverging plates where molten rock is brought up from deep beneath the Earth’s crust. See also subduction zone.
oceanic trench See deep-sea trench
oceanography Scientific discipline concerned with all aspects of the world’s oceans and seas, including their physical and chemical proper¬ ties, origin and geology, and life forms. Research entails sampling sea¬ water and marine life, remote sensing of oceanic processes with aircraft and satellites, and exploration of the seafloor. Oceanography aids in pre¬ dicting weather and climate, in exploitation of the Earth’s resources, and in understanding the effects of pollutants. See also marine geology.