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delta |
Also found in: Dictionary/thesaurus, Medical, Financial, Wikipedia, Hutchinson | 0.03 sec. |
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delta [from triangular shape of the Nile delta, like the Greek letter delta], a deposit of clay, silt, and sand formed at the mouth of a river where the stream loses velocity and drops part of its sediment load. No delta is formed if the coast is sinking or if there is an ocean or tidal current strong enough to prevent sediment deposition. Coarse particles settle first, with fine clays last and found at the outer regions of the delta. The three main varieties of deltas are the arcuate (the Nile), the bird's-foot (the Mississippi), and the cuspate (the Tiber). The Nile, Mississippi, Niger, Rhine, Danube, Kuban, Volga, Amu Darya, Indus, Ganges-Brahmaputra, Ayeyarwady, Tigris and Euphrates, and Huang He (Yellow) rivers are among those that have formed large deltas, many of which are fertile lands that support dense agricultural populations. deltaLow-lying plain composed of stream-borne sediments deposited by a river at its mouth. Deltas have been important to humankind since prehistoric times. Sands, silts, and clays deposited by floodwaters were extremely productive agriculturally; and major civilizations flourished in the deltaic plains of the Nile and Tigris-Euphrates rivers. In recent years geologists have discovered that much of the world's petroleum resources are found in ancient deltaic rocks. Deltas vary widely in size, structure, composition, and origin, though many are triangular (the shape of the Greek letter delta). deltaAn incremental value between one number and another. delta 1. the fourth letter in the Greek alphabet (Δ or δ), a consonant transliterated as d 2. the flat alluvial area at the mouth of some rivers where the mainstream splits up into several distributaries 3. Maths a finite increment in a variable delta [′del·tə] (anatomy) A fingerprint focal point which is the point on a ridge at or in front of and nearest the center of the divergence of the type lines. (electronics) The difference between a partial-select output of a magnetic cell in a one state and a partial-select output of the same cell in a zero state. (geology) An alluvial deposit, usually triangular in shape, at the mouth of a river, stream, or tidal inlet.
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