Turbidity Currents


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Turbidity Currents

 

benthic currents in seas and oceans that are characterized by increased density.

Turbidity currents arise as a result of an earthquake or other factors on a slope of the sea bottom when the equilibrium of large masses of loose clastic deposits is disrupted and submarine landslides are formed; the sliding material is stirred up and, in the form of a mud (turbid) flow, descends along the slope at high speed over a distance as great as hundreds of kilometers; in the process the turbidity currents not only carry sediments but also erode the ocean floor. This may promote the formation of submarine canyons. Particles of various sizes (ranging from clay to coarse grainy material) are interspersed in turbidity currents. Saturation with suspended matter gives turbidity currents great density. Therefore, larger fragments are transported in suspension matter within a finer-grained “mud.” Discharge takes place on the bottom of sea and ocean basins, in submarine canyons, and in glacial troughs.

When the velocity and density of a turbidity current decrease, large and heavy particles, and then smaller and smaller particles, down to the size of mud, drop out of the suspended matter. The next turbidity current brings a new portion of sediment; a second layer is formed, with gradual internal sorting that is separated by a sharp boundary from the inferior layer. The layers can be traced over large distances. The thickness of each layer is usually modest, but the thicknesses of various layers range from a few centimeters to a few meters. Repeated deposition of layers forms a sedimentary layer with repeating stratification. Such a formation of deposits has been verified experimentally. The deposits of turbidity currents (“turbidites”) are widespread in recent seas and in many mineral deposits of varying geological age.

REFERENCES

Botvinkina, L. N. Sloistost’ osadochnykh porod. Moscow, 1962.
Shepard, F. P. Morskaia geologiia. Leningrad, 1969. (Translated from English.)
Bouma, A. H., and A. Brower [eds.]. Turbidites. Amsterdam-New York, 1964. (Developments in Sedimentology, vol. 3).

L. N. BOTVINKINA

References in periodicals archive ?
Deposits of turbidity currents, i.e., turbidites, can be found in different geological settings such as lakes, reservoirs, delta fronts and continental shelves (Walker 1976).
(1986), respectively, and indicate long-distance transport by debris flows and/or high-concentration turbidity currents and finally rapid collective deposition of a pebble-sand mixture.
and Sibuet, J.-C., 2009, How of turbidity currents as evidenced by failure of submarine telecommunication cables, in Chiocci, F.L., Ridenti, D., Casalbore, D., and Bosman, A., eds., International Conference on Seafloor Mapping for Geohazard Assessment, Extended Abstracts, Rendiconti online, Societa Geologica Italiana, v.
These factors again provide the conditions for minimizing the sediment deposition; thus, it seems that sedimentation rates can be greatly reduced by confining the turbidity currents.
Turbidity currents are powerful landslides of underwater debris.
Rare, very large turbidity currents periodically deposit thick sequences of sediment on oceanic abyssal plains, but their return periods span many thousands of years.
Here we will make a step change in understanding of turbidity currents, and their wider impacts, by making the first detailed measurements of turbidity current that runout into the deep (2-5 km) ocean.
SLIP 'N' SLIDE Scientists haven't often caught turbidity currents on the move.
and Migliorini, C.I., 1950, Turbidity currents as a cause of graded bedding: Journal of Geology, v.
At the floor, these slides, or turbidity currents, can deposit a 12-inch layer of sediments within 24 hours, says John E.
According to Shor, "smaller bedforms develop from fast tidal currents in shallow water, but normally the flows in deep water aren't strong or persistent enough to form [such large features in gravel]." But as more surveys are conducted with sonar systems along coastlines where strong turbidity currents might have flowed, it's likely that more gravel dunes will turn up.
The proposed research focuses on: i) modeling and algorithm development for sediment transport in river and coastal flows and for inland and offshore turbidity currents or debris flows, and ii) experiments and simulations of sediment transport in river and coastal flows, and sediment-laden density underflows in reservoirs and submarine canyons.