A turbidity current or density current is a current of 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 than the fluid through which it flows. Turbidity standards of 10, 100, and 1000 NTU Turbidity is a cloudiness or haziness of water (or other liquid) caused by individual particles that are too small to be seen without magnification, thus being much like smoke in air. ...

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. Global earthquake epicenters, 1963–1998 An earthquake is a trembling or a shaking movement of the Earths surface. ... Severe soil erosion in a wheat field near Washington State University, USA. Erosion is the displacement of solids (soil, mud, rock, and so forth) by the agents of wind, water, ice, movement in response to gravity, or living organisms (in the case of bioerosion). ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ...

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. For a video showing a turbidity current in motion, see this link (http://faculty.gg.uwyo.edu/heller/SedMovs/middletonturb.htm). Categories: Stub | Plate tectonics | Earth sciences | Landforms | Oceanic trenches ... A Submarine canyon is a steep-sided valley on the seafloor of the continental slope. ...

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. For a video illustration of this process, see this link (http://faculty.gg.uwyo.edu/heller/SedMovs/Turbidity%20ignition.html).

Examples of turbidity currents

• Grand Banks earthquake of 1929, 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.^{[1] (http://en.wikipedia.org/wiki/Turbidity_current#endnote_Heezen)}
• Avalanches

Newfoundland (French: Terre-Neuve; Irish: Talamh an Éisc; Latin: Terra Nova) is a large island off the north-east coast of North America, and the most populous part of the Canadian province of Newfoundland and Labrador. ... A transatlantic telephone cable is a submarine communications cable that carries telephone traffic under the Atlantic Ocean between North America and Europe. ... The epicenter or epicentre (ancient Greek: επίκεντρον) is the point on the Earths surface that is directly above or below the center of a localized explosive event or point of seismic energy release. ... The continental shelf is an area of relatively shallow sea water that is found on the edge of each continent. ... A Himalayan avalanche. ...

References

^  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.