Turbid flow

Turbidites are formed by underwater flows on the edge of continental shelves or deep lakes with steep slopes with shallows along the coastline. The material settling in the lower part of the shelf (turbidite deposits), as a rule, consists of sand or other coarse fragments, which are replaced above with siltstone, which is formed by layers of silt settling slower than sand particles

Longitudinal section through an underwater turbidity current

Turbid current ( English turbidity current ) - a term used in marine geomorphology, denoting one of the varieties of gravitational flows of sediments. In contrast to flows with a high concentration of the solid phase, 1500–2400 kg / m³ (liquefied sludge flows, grain flows, mud-stone flows), turbid flows are characterized by a low solids content of 1030–1300 kg / m³. Solid particles are kept afloat due to the vertical component of fluid turbulence. In essence, these are short-lived gravitational turbulent flows of a suspension of increased density relative to seawater. These flows transfer the bulk of terrigenous sediments from shallow waters to deep-sea ocean basins. Turbid flows can reach a speed of 90 km / h, transferring up to 3 kg / m³ of sedimentary material. Transfer distance up to 100 km and more ^[1] .

Turbid flows can occur as a result of an increase in solid river runoff, earthquakes, or excess of the steepness of the natural slope of sediments on the seabed. Turbid flows are usually associated with systems of submarine canyons on the continental margins. Most of these canyons are located opposite the mouths of large rivers. Deposits formed on the seabed due to matter brought by turbid flows are called turbidites .