- 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
turbiditythan 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 erosionand subsequent sedimentationin features classified as turbidites.
Turbidity currents are characteristic of areas where there is seismic instability and an underwater slope, especially
submarine trenchslopes 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
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 slopefrom 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.]
* [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] .
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