- density current
Geol., Oceanog.See turbidity current.
* * *Any current in either a liquid or a gas that is kept in motion by the force of gravity acting on small differences in density.A density difference can exist between two fluids or between different parts of the same fluid. Density currents flow along ocean and lake bottoms, because the water entering is colder, saltier, or contains more suspended sediment and thus is denser than the surrounding water. Density currents are a factor in water pollution, as the industrial discharge of large amounts of polluted or heated water can generate density currents that affect neighbouring human or animal communities.
* * *▪ physicsany current in either a liquid or a gas that is kept in motion by the force of gravity acting on small differences in density. A density difference can exist between two fluids or between different parts of the same fluid because of a difference in temperature, salinity, or concentration of suspended sediment.Density currents in nature are exemplified by those currents that flow along the bottom of oceans or lakes. Such subaqueous currents occur because the water entering an ocean or a lake is colder, saltier, or contains more suspended sediment and, thus, is denser than the surrounding waters. As a consequence, it sinks and flows along the bottom under the effect of gravity. The difference in density, moreover, slows down the mixing of the subaqueous current with the overlying waters, enabling it to maintain itself for a relatively long distance.Density currents are of considerable practical importance. For example, the deposition of sediment from turbidity currents—i.e., density currents in which the density difference is caused by suspended sediment—in lakes may result in a rapid decrease of reservoir capacity. Equally significant, the industrial discharge of large amounts of polluted or heated water may generate density currents that have adverse effects on neighbouring human or animal communities.Because of such considerations, many experimental studies on the properties of density currents have been undertaken. Small turbidity currents have been investigated in the laboratory and have been observed directly in lakes. Indirect evidence strongly suggests that large-scale turbidity currents occur in ocean basins. Many researchers believe that a current of this type is caused by the slumping of sediments that have accumulated at the head of a submarine canyon. Slumping of large masses of sediment produces a very dense sediment–water mixture that eventually flows down the canyon to spread out across the seafloor and deposit a layer of sand in the deep water. Repeated deposition results in the formation of submarine fans, structures that closely resemble the alluvial fans that occur at the mouth of many river canyons. Sedimentary rocks that are thought to have originated from ancient turbidity currents are called turbidites and are common in the geological record.
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density current — Geol., Oceanog. See turbidity current. * * * density current, 1. Physics. the passage by gravity of a liquid or gas through or around a fluid of slightly different density. 2. = turbidity current. (Cf. ↑turbidity current) … Useful english dictionary
density current — A gravity induced flow of one current through, over, or under another, owing to density differences. Factors affecting density differences include temperature, salinity, and concentration of suspended particles … Lexicon of Cave and Karst Terminology
density current — /ˈdɛnsəti kʌrənt/ (say densuhtee kuruhnt) noun a current, as in a liquid or a gas, which is kept flowing by gravity acting on small differences in density, as those created by differences in temperature, salinity and turbidity … Australian English dictionary
density — /den si tee/, n., pl. densities. 1. the state or quality of being dense; compactness; closely set or crowded condition. 2. stupidity; slow wittedness; obtuseness. 3. the number of inhabitants, dwellings, or the like, per unit area: The… … Universalium
current — currently, adv. /kerr euhnt, kur /, adj. 1. passing in time; belonging to the time actually passing: the current month. 2. prevalent; customary: the current practice. 3. popular; in vogue: current fashions. 4. new; present; most recent: the… … Universalium
density — /ˈdɛnsəti / (say densuhtee) noun (plural densities) 1. the state or quality of being dense; compactness; closely set or crowded condition. 2. stupidity. 3. Physics a. the mass per unit of volume. b. the amount per unit of volume or per unit of… … Australian English dictionary
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