continental drift Large-scale movements of continents over the course of geologic time. The first complete theory of continental drift was pro¬ posed in 1912 by Alfred Wegener, who postulated that a single supercon¬ tinent, which he called Pangea, fragmented late in the Triassic Period (248- 206 million years ago) and that the parts began to move away from one another. He pointed to the similarity of rock strata in the Americas and Africa as evidence to support his hypothesis. Wegener’s ideas received support from the concepts of seafloor spreading and plate tectonics begin¬ ning in the 1960s. The modern theory states that the Americas were joined with Europe and Africa until c. 190 million years ago, when they split apart along what is now the Mid-Atlantic Ridge. Subsequent tectonic plate movements brought the continents to their present positions.
The theory of continental drift is based on the concept that the continental and oce¬ anic crusts are embedded in the uppermost layer of the rocky lithosphere. The lithos¬ phere is divided into sections called tectonic plates, which slide over an underlying partly molten layer of rock called the asthenosphere. New lithosphere is created at diverging plate margins (e.g., midocean ridges), and old lithosphere is consumed at converging margins (e.g., subduction zones). The continents passively "drift" along with the moving plates, and over hundreds of millions of years this movement alters the entire geography of the Earth.
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Continental philosophy Collective term for the many distinct philospohical traditions, methods, and styles that predominated on the European continent (particularly in France and Germany) from the time of Immanuel Kant. It is usually understood in contrast with analytic philoso¬ phy, also called Anglo-American philosophy. In the 20th century it encom¬ passed schools such as phenomenology, existentialism, structuralism, and deconstruction and thinkers such as Martin Heidegger, Jean-Paul Sartre, Maurice Merleau-Ponty, Michel Foucault, and Jacques Derrida. See also structuralism; poststructuralism.
continental shelf Broad, relatively shallow submarine platform that forms a border to a continent, typically extending from the coast to depths of 330-660 ft (100-200 m). Continental shelves average about 40 mi (65 km) in width. Almost everywhere they are simply a continuation of the continental landmass: narrow, rough, and steep off mountainous coasts but broad and comparatively level offshore from plains. Continental shelves are usually covered with a layer of sand, silts, and silty muds. Their surfaces feature small hills and ridges that alternate with shallow depressions and valley-like troughs. In a few cases, steep-walled V-shaped submarine canyons cut deeply into both the shelf and the slope below. See illustration above.
coastal shoreline plain
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canyon
continental
continental
slope
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abyssal
plain
The broad, gentle pitch of the continental shelf gives way to the relatively steep con¬ tinental slope. The more gradual transition to the abyssal plain is a sediment-filled region called the continental rise. The continental shelf, slope, and rise are collec¬ tively called the continental margin. Depth is exaggerated here for effect.
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continental shield Any of the large stable areas of low relief (little variation in elevations) in the Earth’s crust that are composed of Precam- brian crystalline rocks. These rocks are always more than 570 million years old, and some are as old as 2-3 billion years. Continental shields occur on each of the continents.
continental slope Seaward border of a continental shelf. The world’s combined continental slope is about 200,000 mi (300,000 km) long and descends at an average angle of about 4° from the edge of the continen¬ tal shelf to the beginning of the ocean basins at depths of 330-10,500 ft (100-3,200 m). The slope is most gradual off stable coasts without major rivers and is steepest off coasts with young mountain ranges and narrow continental shelves. Slopes off mountainous coastlines and narrow shelves commonly have outcrops of rock. The dominant sediments of continen¬ tal slopes are muds; there are smaller amounts of sediments of sand or gravel.
Continental System In the Napoleonic Wars, the blockade designed by Napoleon to paralyze Britain through the destruction of British com¬ merce. In the Decrees of Berlin (1806) and Milan (1807), France pro¬ claimed that neutrals and French allies were not to trade with the British. The United Kingdom responded with a counterblockade, which led indi¬ rectly to the War of 1812. Because of Britain’s naval superiority, the effort to enforce the system proved disastrous for Napoleon.
continuing education or adult education Any form of learning provided for adults. In the U.S. the University of Wisconsin was the first academic institution to offer such programs (1904). Empire College of the State University of New York was the first to be devoted exclusively to adult learning (1969). Continuing education includes such diverse meth¬ ods as independent study; broadcast, videotape, online, and other forms of distance learning; group discussion and study circles; conferences, seminars, and workshops; and full- or part-time classroom study. Reme¬ dial programs, such as high-school equivalency and basic literacy pro¬ grams, are common. In recent years the variety of subject matter has expanded greatly to include such topics as auto repair, retirement plan¬ ning, and computer skills. See also Chautauqua movement.
continuity In mathematics, a property of functions and their graphs. A continuous function is one whose graph has no breaks, gaps, or jumps. It is defined using the concept of a limit. Specifically, a function is said to be continuous at a value x if the limit of the function exists there and is equal to the function’s value at that point. When this condition holds true for all real number values of x in an interval, the result is a graph that can be drawn over that interval without lifting the pencil. Such functions are crucial to the theory of calculus, not just because they model most physi¬ cal systems but because the theorems that lead to the derivative and the integral assume the continuity of the functions involved.
continuity principle or continuity equation Principle of fluid mechanics. Stated simply, what flows into a defined volume in a defined time, minus what flows out of that volume in that time, must accumulate in that volume. If the sign of the accumulation is negative, then the mate-
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rial in that volume is being depleted. The principle is a consequence of the law of conservation of mass. The behaviour of fluids in motion is fully described by this equation, plus a second equation, based on the second of Newton's laws of motion, and a third equation, based on the conser¬ vation of ENERGY.
continuo or basso continuo In Baroque music, a special subgroup of an instrumental ensemble. It consists of two instruments reading the same part: a bass instrument, such as a cello or bassoon, and a chordal instrument, most often a harpsichord but sometimes an organ or lute. Its appearance in the early 17th century reflected the radically new musical texture of accompanied melody that was especially typical of the new vocal genre of opera. The continuo (which has a counterpart in the bass and rhythm guitar of a rock band) came to be employed in virtually all ensemble music of the Baroque era.