A turbidity current is most typically an underwater current of usually rapidly moving, sediment-laden water moving down a slope; although current research (2018) indicates that water-saturated sediment may be the primary actor in the process. Turbidity currents can also occur in other

fluid In physics, a fluid is a liquid, gas, or other material that may continuously motion, move and Deformation (physics), deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are M ...

s besides water. Researchers from the Monterey Bay Aquarium Research Institute found that a layer of water-saturated sediment moved rapidly over the seafloor and mobilized the upper few meters of the preexisting seafloor. Plumes of sediment-laden water were observed during turbidity current events but they believe that these were secondary to the pulse of the

seafloor sediment Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles either have their origins in soil and rocks and have been transported from the land to the ...

moving during the events. The belief of the researchers is that the water flow is the tail-end of the process that starts at the seafloor. In the most typical case of oceanic turbidity currents, sediment laden waters situated over sloping ground will flow down-hill because they have a higher

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

than the adjacent waters. The driving force behind a

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and wa ...

current is gravity acting on the high density of the sediments temporarily suspended within a fluid. These semi-suspended solids make the average density of the sediment bearing water greater than that of the surrounding, undisturbed water. As such currents flow, they often have a "snow-balling-effect", as they stir up the ground over which they flow, and gather even more sedimentary particles in their current. Their passage leaves the ground over which they flow scoured and eroded. Once an oceanic turbidity current reaches the calmer waters of the flatter area of the

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They ...

(main oceanic floor), the particles borne by the current settle out of the water column. The sedimentary deposit of a turbidity current is called a

turbidite A turbidite is the geologic Deposition (geology), deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing ...

. Seafloor turbidity currents are often the result of sediment-laden river outflows, and can sometimes be initiated by

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

s, slumping and other soil disturbances. They are characterized by a well-defined advance-front, also known as the current's head, and are followed by the current's main body. In terms of the more often observed and more familiar above sea-level phenomenon, they somewhat resemble flash floods. Turbidity currents can sometimes result from submarine

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...

instability, which is common with steep underwater slopes, and especially with submarine trench slopes of convergent plate margins, continental slopes and

submarine canyon A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to , from canyon flo ...

s of passive margins. With an increasing continental shelf slope, current velocity increases, as the velocity of the flow increases, turbulence increases, and the current draws up more sediment. The increase in sediment also adds to the density of the current, and thus increases its velocity even further.

Definition

Turbidity currents are traditionally defined as those sediment gravity flows in which sediment is suspended by fluid turbulence. Meiburg, E. & Kneller, B. 2010, "Turbidity currents and their deposits", Annual Review of Fluid Mechanics, vol. 42, pp. 135–156. However, the term "turbidity current" was adopted to describe a

natural phenomenon A natural phenomenon is an observable event which is not man-made. Examples include: sunrise, weather, fog, thunder, tornadoes; biological processes, decomposition, germination; physical processes, wave propagation, erosion; tidal flow, and na ...

whose exact nature is often unclear. The turbulence within a turbidity current is not always the support mechanism that keeps the sediment in suspension; however it is probable that turbulence is the primary or sole grain support mechanism in dilute currents (<3%).Kneller, B. & Buckee, C. 2000, "The structure and fluid mechanics of turbidity currents: A review of some recent studies and their geological implications", Sedimentology, vol. 47, no. SUPPL. 1, pp. 62–94. Definitions are further complicated by an incomplete understanding of the turbulence structure within turbidity currents, and the confusion between the terms

turbulent In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between ...

(i.e. disturbed by eddies) and

turbid Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and wate ...

(i.e. opaque with sediment). Kneller & Buckee, 2000 define a suspension current as 'flow induced by the action of gravity upon a turbid mixture of fluid and (suspended) sediment, by virtue of the density difference between the mixture and the ambient fluid'. A turbidity current is a suspension current in which the

interstitial fluid In cell biology, extracellular fluid (ECF) denotes all body fluid outside the Cell (biology), cells of any multicellular organism. Body water, Total body water in healthy adults is about 50–60% (range 45 to 75%) of total body weight; women ...

is liquid (generally water); a pyroclastic current is one in which the interstitial fluid is gas.

Triggers

Hyperpycnal plume

When the concentration of suspended sediment at the mouth of a

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

is so large that the density of river water is greater than the density of sea water a particular kind of turbidity current can form called a hyperpycnal plume.Mulder, T. & Syvitski, J.P.M. 1995, "Turbidity currents generated at river mouths during exceptional discharges to the world oceans", Journal of Geology, vol. 103, no. 3, pp. 285–299. The average concentration of suspended sediment for most river water that enters the

ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...

is much lower than the sediment concentration needed for entry as a hyperpycnal plume. Although some rivers can often have continuously high sediment load that can create a continuous hyperpycnal plume, such as the Haile River (China), which has an average suspended concentration of 40.5 kg/m³. The sediment concentration needed to produce a hyperpycnal plume in marine water is 35 to 45 kg/m³, depending on the water properties within the

coastal A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

zone. Most rivers produce hyperpycnal flows only during exceptional events, such as storms,

floods A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

outbursts, dam breaks, and

lahar A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of Pyroclastic rock, pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a valley, river valley. Lahars are o ...

flows. In fresh water environments, such as

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

s, the suspended sediment concentration needed to produce a hyperpycnal plume is quite low (1 kg/m³).

Sedimentation in reservoirs

The

transport Transport (in British English) or transportation (in American English) is the intentional Motion, movement of humans, animals, and cargo, goods from one location to another. Mode of transport, Modes of transport include aviation, air, land tr ...

and deposition of the

sediments Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

in narrow alpine

reservoirs A reservoir (; ) is an enlarged lake behind a dam, usually built to store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of water, interrup ...

is often caused by turbidity currents. They follow the

thalweg In geography, hydrography, and fluvial geomorphology, a thalweg or talweg () is the line or curve of lowest elevation within a valley or watercourse. Normally only the horizontal position of the curve is considered (as viewed on a map); the c ...

of the lake to the deepest area near the

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

, where the sediments can affect the operation of the bottom outlet and the intake structures.Oehy, C.D. & Schleiss, A.J. 2007, "Control of turbidity currents in reservoirs by solid and permeable obstacles", Journal of Hydraulic Engineering, vol. 133, no. 6, pp. 637–648. Controlling this

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to th ...

within the reservoir can be achieved by using solid and permeable obstacles with the right design.

Earthquake triggering

Turbidity currents are often triggered by

tectonic Tectonics ( via Latin ) are the processes that result in the structure and properties of the Earth's crust and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons. These processes ...

disturbances of the sea floor. The

displacement Displacement may refer to: Physical sciences Mathematics and physics *Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...

continental crust Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...

in the form of fluidization and physical shaking both contribute to their formation. Earthquakes have been linked to turbidity current deposition in many settings, particularly where physiography favors preservation of the deposits and limits the other sources of turbidity current deposition.Adams, J., 1990, Paleoseismicity of the Cascadia subduction zone: Evidence from turbidites off the Oregon-Washington Margin: Tectonics, v. 9, p. 569–584. Since the famous case of breakage of submarine cables by a turbidity current following the 1929 Grand Banks earthquake, earthquake triggered turbidites have been investigated and verified along the Cascadia subduction Zone,Goldfinger, C., Nelson, C.H., and Johnson, J.E., 2003, Holocene Earthquake Records From the Cascadia Subduction Zone and Northern San Andreas Fault Based on Precise Dating of Offshore Turbidites: Annual Review of Earth and Planetary Sciences, v. 31, p. 555–577. the Northern San Andreas Fault, a number of European, Chilean and North American lakes, Japanese lacustrine and offshore regions and a variety of other settings.

Canyon-flushing

When large turbidity currents flow into

canyons A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...

they may become self-sustaining, and may entrain sediment that has previously been introduced into the canyon by littoral drift, storms or smaller turbidity currents. Canyon-flushing associated with surge-type currents initiated by slope failures may produce currents whose final volume may be several times that of the portion of the slope that has failed (e.g. Grand Banks).

Slumping

Sediment that has piled up at the top of the

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

, particularly at the heads of submarine canyons can create turbidity current due to overloading, thus consequent slumping and sliding.

Convective sedimentation beneath river plumes

A buoyant sediment-laden river plume can induce a secondary turbidity current on the ocean floor by the process of convective sedimentation. Sediment in the initially buoyant hypopycnal flow accumulates at the base of the surface flow, so that the dense lower boundary become unstable. The resulting convective sedimentation leads to a rapid vertical transfer of material to the sloping lake or ocean bed, potentially forming a secondary turbidity current. The vertical speed of the convective plumes can be much greater than the Stokes settling velocity of an individual particle of sediment. Most examples of this process have been made in the laboratory, but possible observational evidence of a secondary turbidity current was made in Howe Sound, British Columbia, where a turbidity current was periodically observed on the delta of the Squamish River. As the vast majority of sediment laden rivers are less dense than the ocean, rivers cannot readily form plunging hyperpycnal flows. Hence convective sedimentation is an important possible initiation mechanism for turbidity currents.

Effect on ocean floor

Large and fast-moving turbidity currents can carve gulleys and

ravines A ravine is a landform that is narrower than a canyon and is often the product of streambank erosion. Ravines are typically classified as larger in scale than gullies, although smaller than valleys. Ravines may also be called a cleuch, dell, g ...

into the ocean floor of continental margins and cause damage to artificial structures such as telecommunication cables on the seafloor. Understanding where turbidity currents flow on the ocean floor can help to decrease the amount of damage to telecommunication cables by avoiding these areas or reinforcing the cables in vulnerable areas. When turbidity currents interact with regular ocean currents, such as contour currents, they can change their direction. This ultimately shifts submarine canyons and sediment deposition locations. One example of this is located in the western part of the Gulf of Cadiz, where the ocean current leaving the Mediterranean Sea (also known as the Mediterranean outflow water) pushes turbidity currents westward. This has changed the shape of submarine valleys and canyons in the region to also curve in that direction.

Deposits

When the energy of a turbidity current lowers, its ability to keep suspended sediment decreases, thus sediment deposition occurs. When the material comes to rest, it is the sand and other coarse material which settles first followed by mud and eventually the very fine particulate matter. It is this sequence of deposition that creates the so called Bouma sequences that characterize

deposits. Because turbidity currents occur underwater and happen suddenly, they are rarely seen as they happen in nature, thus turbidites can be used to determine turbidity current characteristics. Some examples:

grain A grain is a small, hard, dry fruit (caryopsis) – with or without an attached husk, hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and ...

size can give indication of current velocity, grain

lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...

and the use of

foraminifera Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...

for determining origins, grain distribution shows flow dynamics over time and sediment thickness indicates sediment load and longevity. Turbidites are commonly used in the understanding of past turbidity currents, for example, the Peru-Chile Trench off Southern Central

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

(36°S–39°S) contains numerous turbidite layers that were cored and analysed.Völker, D., Reichel, T., Wiedicke, M. & Heubeck, C. 2008, "Turbidites deposited on Southern Central Chilean seamounts: Evidence for energetic turbidity currents", Marine Geology, vol. 251, no. 1–2, pp. 15–31 From these turbidites the predicted history of turbidity currents in this area was determined, increasing the overall understanding of these currents.

Antidune deposits

Some of the largest

antidunes An antidune is a bedform found in fluvial and other channeled environments. Antidunes occur in supercritical flow, meaning that the Froude number is greater than 1.0 or the flow velocity exceeds the wave velocity; this is also known as upper flow ...

on Earth are formed by turbidity currents. One observed sediment-wave field is located on the lower continental slope off

Guyana Guyana, officially the Co-operative Republic of Guyana, is a country on the northern coast of South America, part of the historic British West Indies. entry "Guyana" Georgetown, Guyana, Georgetown is the capital of Guyana and is also the co ...

, South America.Ercilla, G., Alonso, B., Wynn, R.B. & Baraza, J. 2002, "Turbidity current sediment waves on irregular slopes: Observations from the Orinoco sediment-wave field", Marine Geology, vol. 192, no. 1–3, pp. 171–187. This sediment-wave field covers an area of at least 29 000 km² at a water depth of 4400–4825 meters. These antidunes have

wavelengths In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same '' phase'' on ...

of 110–2600 m and

wave height In fluid dynamics, the wave height of a surface wave is the difference between the elevations of a crest and a neighboring trough. ''Wave height'' is a term used by mariners, as well as in coastal, ocean and naval engineering. At sea, the ...

s of 1–15 m. Turbidity currents responsible for wave generation are interpreted as originating from slope failures on the adjacent

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

and

Suriname Suriname, officially the Republic of Suriname, is a country in northern South America, also considered as part of the Caribbean and the West Indies. It is a developing country with a Human Development Index, high level of human development; i ...

continental margins. Simple numerical modelling has been enabled to determine turbidity current flow characteristics across the sediment waves to be estimated: internal

Froude number In continuum mechanics, the Froude number (, after William Froude, ) is a dimensionless number defined as the ratio of the flow inertia to the external force field (the latter in many applications simply due to gravity). The Froude number is ba ...

= 0.7–1.1, flow thickness = 24–645 m, and flow velocity = 31–82 cm·s⁻¹. Generally, on lower gradients beyond minor breaks of slope, flow thickness increases and flow velocity decreases, leading to an increase in wavelength and a decrease in height.

Reversing buoyancy

The behaviour of turbidity currents with buoyant fluid (such as currents with warm, fresh or

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

interstitial water entering the sea) has been investigated to find that the front speed decreases more rapidly than that of currents with the same density as the ambient fluid.Hürzeler, B.E., Imberger, J. & Ivey, G.N. 1996 Dynamics of turbidity current with reversing buoyancy. J. Hydraul. Eng., 122, 230–236. These turbidity currents ultimately come to a halt as sedimentation results in a reversal of buoyancy, and the current lifts off, the point of lift-off remaining constant for a constant discharge. The lofted fluid carries fine sediment with it, forming a plume that rises to a level of neutral buoyancy (if in a stratified environment) or to the water surface, and spreads out. Sediment falling from the plume produces a widespread fall-out deposit, termed hemiturbidite. Experimental turbidity currents and field observations suggest that the shape of the lobe deposit formed by a lofting plume is narrower than for a similar non-lofting plume

Prediction

Prediction A prediction (Latin ''præ-'', "before," and ''dictum'', "something said") or forecast is a statement about a future event or about future data. Predictions are often, but not always, based upon experience or knowledge of forecasters. There ...

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

by turbidity currents, and of the distribution of turbidite deposits, such as their extent, thickness and grain size distribution, requires an understanding of the mechanisms of

sediment transport Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems wh ...

and deposition, which in turn depends on the

fluid dynamics In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in motion ...

of the currents. The extreme complexity of most turbidite systems and beds has promoted the development of quantitative models of turbidity current behaviour inferred solely from their deposits. Small-scale laboratory experiments therefore offer one of the best means of studying their dynamics. Mathematical models can also provide significant insights into current dynamics. In the long term, numerical techniques are most likely the best hope of understanding and predicting three-dimensional turbidity current processes and deposits. In most cases, there are more variables than governing

equations In mathematics, an equation is a mathematical formula that expresses the equality of two expressions, by connecting them with the equals sign . The word ''equation'' and its cognates in other languages may have subtly different meanings; for e ...

, and the models rely upon simplifying assumptions in order to achieve a result. The accuracy of the individual models thus depends upon the validity and choice of the assumptions made. Experimental results provide a means of constraining some of these variables as well as providing a test for such models. Physical data from field observations, or more practical from experiments, are still required in order to test the simplifying assumptions necessary in

mathematical model A mathematical model is an abstract and concrete, abstract description of a concrete system using mathematics, mathematical concepts and language of mathematics, language. The process of developing a mathematical model is termed ''mathematical m ...

s. Most of what is known about large natural turbidity currents (i.e. those significant in terms of sediment transfer to the deep sea) is inferred from indirect sources, such as submarine cable breaks and heights of deposits above submarine valley floors. Although during the 2003 Tokachi-oki earthquake a large turbidity current was observed by the cabled observatory which provided direct observations, which is rarely achieved.

Oil exploration

Oil and gas companies are also interested in turbidity currents because the currents deposit

organic matter Organic matter, organic material or natural organic matter is the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come fro ...

that over

geologic time The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronolo ...

gets buried, compressed and transformed into

hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may b ...

. The use of numerical modelling and flumes are commonly used to help understand these questions.Salles, T., Lopez, S., Eschard, R., Lerat, O., Mulder, T. & Cacas, M.C. 2008, "Turbidity current modelling on geological time scales", Marine Geology, vol. 248, no. 3–4, pp. 127–150. Much of the modelling is used to reproduce the physical processes which govern turbidity current behaviour and deposits.

Modeling approaches

Shallow-water models

The so-called depth-averaged or shallow-water models are initially introduced for compositional gravity currents Rottman, J.W. & Simpson, J.E. 1983, "Gravity currents produced by instantaneous releases of a heavy fluid in a rectangular channel", Journal of Fluid Mechanics, vol. 135, pp. 95–110. and then later extended to turbidity currents.Parker, G., Fukushima, Y. & Pantin, H.M. 1986, "Self-accelerating turbidity currents", Journal of Fluid Mechanics, vol. 171, pp. 145–181.Bonnecaze, R.T., Huppert, H.E. & Lister, J.R. 1993, "Particle-driven gravity currents", Journal of Fluid Mechanics, vol. 250, pp. 339–369. The typical assumptions used along with the shallow-water models are: hydrostatic pressure field, clear fluid is not entrained (or detrained), and particle concentration does not depend on the vertical location. Considering the ease of implementation, these models can typically predict flow characteristic such as front location or front speed in simplified geometries, e.g. rectangular channels, fairly accurately.

Depth-resolved models

With the increase in computational power, depth-resolved models have become a powerful tool to study gravity and turbidity currents. These models, in general, are mainly focused on the solution of the Navier-Stokes equations for the fluid phase. With dilute suspension of particles, a Eulerian approach proved to be accurate to describe the evolution of particles in terms of a continuum particle concentration field. Under these models, no such assumptions as shallow-water models are needed and, therefore, accurate calculations and measurements are performed to study these currents. Measurements such as, pressure field, energy budgets, vertical particle concentration and accurate deposit heights are a few to mention. Both

Direct numerical simulation A direct numerical simulation (DNS)https://eprints.soton.ac.uk/66182/1/A_primer_on_DNS.pdf "A Primer on Direct Numerical Simulation of Turbulence – Methods, Procedures and Guidelines", Coleman and Sandberg, 2010 is a simulation in computational ...

(DNS) Necker, F., Hartel, C., Kleiser, L. & Meiburg, E. 2002, "High-resolution simulations of particle-driven gravity currents", International Journal of Multiphase Flow, vol. 28, pp. 279–300. and Turbulence modelingKassem, A. & Imran, J. 2004, "Three-dimensional modeling of density current. II. Flow in sinuous confined and uncontined channels", Journal of Hydraulic Research, vol. 42, number. 6, pp. 591–602. are used to model these currents.

Notable examples of turbidity currents

* Within minutes after the 1929 Grand Banks earthquake occurred off the coast of

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

transatlantic telephone cable A transatlantic telecommunications cable is a submarine communications cable connecting one side of the Atlantic Ocean to the other. In the 19th and early 20th centuries, each cable was a single wire. After mid-century, coaxial cable came into us ...

s began breaking sequentially, farther and farther downslope, away from the

epicenter The epicenter (), epicentre, or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Determination The primary purpose of a ...

. Twelve cables were snapped in a total of 28 places. Exact times and locations were recorded for each break. Investigators suggested that an estimated 60 mile per hour (100 km/h) submarine ''landslide'' or turbidity current of water saturated sediments swept 400 miles (600 km) down the

from the earthquake's epicenter, snapping the cables as it passed. Subsequent research of this event have shown that continental slope sediment failures mostly occurred below 650 meter water depth.Piper, D.J.W., Cochonat, P. & Morrison, M.L. 1999, "The sequence of events around the epicentre of the 1929 Grand Banks earthquake: Initiation of debris flows and turbidity current inferred from sidescan sonar", Sedimentology, vol. 46, no. 1, pp. 79–97. The slumping that occurred in shallow waters (5–25 meters) passed down slope into turbidity currents that evolved ignitively. The turbidity currents had sustained flow for many hours due to the delayed retrogressive failure and transformation of

debris flow Debris flows are geological phenomena in which water-laden masses of soil and fragmented Rock (geology), rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. ...

s into turbidity currents through hydraulic jumps. *The Cascadia subduction zone, off the northwestern coast of North America, has a record of earthquake triggered turbiditesGoldfinger, C., Nelson, C.H., Morey, A., Johnson, J.E., Gutierrez-Pastor, J., Eriksson, A.T., Karabanov, E., Patton, J., Gracia, E., Enkin, R., Dallimore, A., Dunhill, G., and Vallier, T., 2011, Turbidite Event History: Methods and Implications for Holocene Paleoseismicity of the Cascadia Subduction Zone, USGS Professional Paper 1661-F, Reston, VA, U.S. Geological Survey, 332 p, 64 Figures. that is well-correlated to other evidence of earthquakes recorded in coastal bays and lakes during the Holocene. Forty–one

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

turbidity currents have been correlated along all or part of the approximately 1000 km long plate boundary stretching from northern California to mid-Vancouver island. The correlations are based on radiocarbon ages and subsurface stratigraphic methods. The inferred recurrence interval of Cascadia great earthquakes is approximately 500 years along the northern margin, and approximately 240 years along the southern margin. *

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

is a hot spot for submarine turbidity currents as there are large amounts of sediment suspended in rivers, and it is seismically active, thus large accumulation of seafloor sediments and earthquake triggering.Hsu, S.-., Kuo, J., Lo, C.-., Tsai, C.-., Doo, W.-., Ku, C.-. & Sibuet, J.-. 2008, "Turbidity currents, submarine landslides and the 2006 Pingtung earthquake off SW Taiwan", Terrestrial, Atmospheric and Oceanic Sciences, vol. 19, no. 6, pp. 767–772. During the

2006 Pingtung earthquake The 2006 Hengchun earthquakes occurred on December 26 at 20:26 and 20:34 China Standard Time, local time off the southwest coast of Taiwan in the Luzon Strait, which connects the South China Sea with the Philippine Sea. The International Seismolo ...

off SW Taiwan, eleven submarine cables across the Kaoping canyon and

Manila Trench The Manila Trench is an oceanic trench in the Pacific Ocean, located west of the islands of Luzon and Mindoro in the Philippines. The trench reaches a depth of about , in contrast with the average depth of the South China Sea of about . It i ...

were broken in sequence from 1500 to 4000 m deep, as a consequence of the associated turbidity currents. From the timing of each cable break the velocity of the current was determined to have a positive relationship with bathymetric slope. Current velocities were on the steepest slopes and on the shallowest slopes. *One of the earliest observations of a turbidity currents was by

François-Alphonse Forel François-Alphonse Forel (; 2 February 1841 – 7 August 1912) was a Swiss physician and scientist who pioneered the study of lakes, and is thus considered the founder. He was also professor at the University of Lausanne and the Father of limnolo ...

. In the late 1800s he made detailed observations of the plunging of the Rhône river into Lake Geneva at Port Valais. These papers were possibly the earliest identification of a turbidity current and he discussed how the submarine channel formed from the delta. In this freshwater lake, it is primarily the cold water that leads to plunging of the inflow. The sediment load by itself is generally not high enough to overcome the summer thermal stratification in

Lake Geneva Lake Geneva is a deep lake on the north side of the Alps, shared between Switzerland and France. It is one of the List of largest lakes of Europe, largest lakes in Western Europe and the largest on the course of the Rhône. Sixty percent () ...

. *The longest turbidity current ever recorded occurred in January 2020 and flowed for through the Congo Canyon over the course of two days, damaging two submarine communications cables. The current was a result of sediment deposited by the 2019–2020 Congo River floods.

References

External links

Turbidity current in motion

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Depth-resolved simulation of turbidity currents
{{Authority control Sedimentology Fluid dynamics Ocean currents he:התנזלות קרקע#זרמי עכירות