- 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
earthquake s orslumping . In such cases, high-speed sediment-laden water flows down the slope under the clearer water, causing a great deal oferosion and subsequentsedimentation in features classified asturbidite s.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 andsubmarine canyon s 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 current s.Examples of turbidity currents
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1929 Grand Banks earthquake , off the coast of Newfoundland. Minutes later,transatlantic telephone cable s began breaking sequentially, farther and farther downslope, away from theepicenter . 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 thecontinental 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.]
*Avalanche see also
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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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