Turbidity current


Turbidity current

A turbidity current or density current is a current of rapidly moving, sediment-laden water moving down a slope through air, water, or another fluid. The current moves because it has a higher density and turbidity than the fluid through which it flows.

The term "turbidity current" is most commonly used to describe underwater currents in lakes and oceans, which are usually triggered by earthquakes or slumping. In such cases, high-speed sediment-laden water flows down the slope under the clearer water, causing a great deal of erosion and subsequent sedimentation in features classified as turbidites.

Turbidity currents are characteristic of areas where there is seismic instability and an underwater slope, especially submarine trench slopes of convergent plate margins and continental slopes and submarine canyons of passive margins.

As the slope of the flow increases, the speed of the current increases. As the speed of the flow increases, turbulence increases, and the current draws up more sediment. The increase in sediment increases the density of the current, and thus its speed, even further. Turbidity currents can reach speeds up to half the speed of sound.

Turbity currents are examples of gravity currents.

Examples of turbidity currents

* 1929 Grand Banks earthquake, off the coast of Newfoundland. Minutes later, transatlantic telephone cables began breaking sequentially, farther and farther downslope, away from the epicenter. Twelve cables were snapped in a total of 28 places. Exact times and locations were recorded for each break. Investigators suggested that a 60-mile-per-hour (100 km/h) submarine "landslide" or turbidity current of water saturated sediments swept 400 miles (600 km) down the continental slope from the earthquake’s epicenter, snapping the cables as it passed. [Bruce C. Heezen and Maurice Ewing, “Turbidity Currents and Submarine Slumps, and the 1929 Grand Banks Earthquake,” American Journal of Science, Vol. 250, December 1952, pp. 849–873.]
* Avalanches

ee also

*Bouma sequence

External links

* [http://faculty.gg.uwyo.edu/heller/SedMovs/middletonturb.htm Turbidity current in motion]
* [http://faculty.gg.uwyo.edu/heller/SedMovs/Turbidity%20ignition.html Start of a turbidity current] .

References


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Look at other dictionaries:

  • turbidity current — n. a current of highly turbid water carrying large amounts of suspended sediment that increase its density and cause it to flow downward through less dense water along the bottom slope of a sea or lake …   English World dictionary

  • turbidity current — Geol. a turbid, dense current of sediments in suspension moving along the slope and bottom of a lake or ocean. Also called density current. * * * Underwater current of abrasive sediments. Such currents appear to be relatively short lived,… …   Universalium

  • turbidity current — Geol. a turbid, dense current of sediments in suspension moving along the slope and bottom of a lake or ocean. Also called density current …   Useful english dictionary

  • turbidity current — noun A fast flowing downhill current (of air or water) that carries silt …   Wiktionary

  • turbidity current — noun an underwater current flowing swiftly downslope owing to the weight of sediment it carries …   English new terms dictionary

  • turbidity current — turbid′ity cur rent n. gel a turbid, dense current of sediments in suspension moving along the slope and bottom of a lake or ocean …   From formal English to slang

  • 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

  • Current (fluid) — A current in a fluid is the magnitude and direction of flow within that fluid. An air current presents the same properties for a gaseous medium. Kinds of fluid currents include. Boundary current Current (stream), a current in a river or stream… …   Wikipedia

  • 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… …   Universalium

  • 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


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