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Topic: Turbidity current


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In the News (Mon 15 Sep 14)

  
  Turbidity current - Wikipedia, the free encyclopedia
The term "turbidity current" is most commonly used to describe underwater currents in lakes and oceans, which are usually triggered by earthquakes or slumping.
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.
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.
en.wikipedia.org /wiki/Turbidity_current   (313 words)

  
 index-page
This approach is advantageous because turbidity currents are difficult to observe directly in nature or model accurately in experiments.
The goal of this study is to develop a method for characterizing turbidity current flow conditions from particle-size distributions in turbidites using algorithms describing sediment transport.
This work was motivated by the fact that, although currents driven by the excess density of sediment in turbulent suspension are responsible for sculpting submarine landscapes and transferring large amounts of sediment from the shelf to deep waters, the physical properties of these flows remain poorly constrained.
web.mit.edu /kruhl/www/turbidity-currents.htm   (658 words)

  
 [No title]
Further, the study of the flow of turbidity currents is used to improve the design of submarine structures such as cables and pipelines to withstand the potentially damaging effects of turbidity currents.
The flow of turbidity currents is often accompanied by deposition of particles from the current on to the bottom surface.
The extent and thickness of turbidities are estimated by analyzing the three partial differential equations that govern the dynamics of and deposition from turbidity currents.
www.che.utexas.edu /~vatsan/phdres.html   (986 words)

  
 SedLab-N9-MIT   (Site not responding. Last check: 2007-10-15)
Turbidity currents are density-stratified flows that occur at the continental margin and in lakes and reservoirs.
Turbidity currents construct massive self-formed channels and are responsible for delivering terrestrial sediment into the deep marine.
We study depositional turbidity currents in various channel geometries by preparing crushed silica in the reservoir tank, and then pumping to a constant head tank, which then delivers a steady flow to the main tank.
www.mit.edu /~douglasj/SedLab-N9-MIT.html   (1093 words)

  
 DOUGHERTY GAP: Evidence for a Turbidity Current Paleoenvironment
The turbidity current depositional environment suggested by the writers for this site is presently not recognized by uniformitarian geologists because their current model requires a coastal swamp paleoenvironment to explain the occurrence of coal layers found in adjacent overlying strata.
Current ripple marks and scour and fill structures are present in some cores and indicate that currents were occasionally active during deposition.
The thickness of the individual sandstone layers in turbidity current deposits is estimated to be a function of the location of the deposit within the deep-sea fan or along the continental shelf edge (i.e., proximal versus distal; see Walker, 1967).
www.creationresearch.org /crsq/articles/32/32_4a1.html   (6803 words)

  
 GVRD - Water - Quality and treatment - Turbidity
Turbidity is measured in units called nephelometric turbidity units (NTUs), and is monitored both by a built-in monitoring system at the water supply intakes and by daily laboratory tests.
Increased turbidity in drinking water may interfere with disinfection, therefore, as turbidity increases there is the potential for an increase in gastrointestinal illness.
Turbidity levels above 1 NTU prompt increased disinfection levels as a safety precaution and may prompt the GVRD to change the operation of the system to maintain water quality.
www.gvrd.bc.ca /water/default.asp   (231 words)

  
 CLASSROOM@SEA PROJECT
Turbidity currents are a bit like that cloud, but they are composed of sediment grains and occur under the sea.
This current (known as a turbidity current because of its turbulent nature) races downslope towards the deep ocean, carrying its sediment load along with it.
This is because of the way that turbidity currents lose their energy as they slow down: the first particles to drop out of the flow are the biggest and the heaviest, but the flow still has enough energy and turbulence to carry the smaller particles.
www.noc.soton.ac.uk /gg/classroom@sea/general_science/turbidites.html   (958 words)

  
 Hurricane Iwa
Current sensors that were redeployed on 20 November 1982 were operating during the hurricane episode; initial deployment positions are plotted in Figure 1, with deployment and recovery information summarized in Table 1.
We hypothesize that the sequence of events was as follows: four of the slope failures generated turbidity currents carrying a mixture of sediment and water downslope at frontal speeds of 300 cm/ s or greater (i.e., speed of meter displacement is minimum).
The fourth turbidity current, detected as a current pulse at mooring 6, traveled downslope, moved mooring 5, caused mooring 4 to release, moved mooring 2, and horizontally buried or entangled mooring 2's current sensor.
www.marscigrp.org /gml84.html   (3663 words)

  
 Re: [iagi-net-l] asosiasi turbidit (laut dalam?) dengan delta   (Site not responding. Last check: 2007-10-15)
Turbidity currents are thought to be caused by the slumping of sediment that has piled up at the top of the continental slope, particularly at the heads of submarine canyons (see below Continental margins: Submarine canyons).
Most geologists and oceanographers accept that such currents exist and that the currents are important agents of erosion and sediment deposition, in both modern and ancient seas, but researchers believe that the turbidity current hypothesis has been overworked.
Hence the problem of discriminating between deposits formed by turbidity currents and deposits formed by other current types is quite complex and requires a careful assessment of all lines of evidence in each case.
www.mail-archive.com /iagi-net@iagi.or.id/msg12271.html   (1164 words)

  
 Water Resource Characterization DSS - Turbidity
General Information: Turbidity is a unit of measurement quantifying the degree to which light traveling through a water column is scattered by the suspended organic (including algae) and inorganic particles.
Suspended loads are carried in both the gentle currents of lentic (lake) waters and the fast currents of lotic (flowing) waters.
Turbidity is often largely due to suspended sediment in the water column.
www.water.ncsu.edu /watershedss/info/turbid.html   (758 words)

  
 WWB :: Environmental Aspects - Construction
The turbidity barrier is designed to restrict the flow of silt-laden runoff from a disturbed area, to keep it contained to a confined area, and to allow the silt and sediment to settle before being carried into the adjacent watercourses.
Turbidity barriers are similar in concept to silt fence and work effectively where silt fence is impractical or impossible to install.
Though originally thought by some to be questionable due to strong currents and tidal cycles, the use of turbidity curtains across the Woodrow Wilson Bridge Project has proven to be an effective and versatile tool to minimize environmental impact in constructing one of the largest transportation projects in the nation surrounded by sensitive environmental resources.
www.wilsonbridge.com /ea-ConTurbidityCurtain.htm   (642 words)

  
 Turbidity
Turbidity is one of the most important parameters used to determine the quality of drinking water.
Turbidity is a unit of measurement quantifying the degree to which light traveling through a water column is scattered by the suspended organic (including algae) and inorganic particles.
Highly turbid waters may be hazardous to the welfare of swimmers and boaters.
webpages.charter.net /kwingerden/erhs/aquarium/turbidit.htm   (798 words)

  
 EES: Kathryn's PhD
Turbidity currents are a type of gravity current, whereby flow results from density differences between two fluids.
Hyperpycnal turbidity currents are difficult to observe and record in the natural environment.
Research on hyperpycnal turbidity currents is being carried out at UEA by Kathryn Amos, Dr Jan Alexander and Prof.
www.uea.ac.uk /env/earthsciences/rivereff.htm   (845 words)

  
 Depositional Control on Hydrocarbon Accumulations in Deepwater Nigeria, by Xijin (CJ) Liu, #40226 (2006).
Turbidity current flows emanating down from a seafloor topographic high is forced to undergo a hydraulic jump from a Froude-supercritical flow regime to a highly Froude-subcritical regime.
It is possible that sands can be carried by a single turbidity current across multiple structural highs and deposit them in the form of terminal lobe if the channel thalweg is more or less close to the equilibrium profile and flow thickness is less than the channel depth.
Once the mini-basin is filled to such a level that the thalweg elevation plus a presumed turbidity current flow thickness exceeds the elevation of the regional equilibrium profile, sand will start to be funneled down the structural high into the downslope part of the channel and be potentially deposited in the next basinward mini-basin.
www.searchanddiscovery.com /documents/2006/06139liu/index.htm   (2002 words)

  
 Turbidity Current - Submarine Structure Interaction: Hazard Analysis via High-Resolution Flow Simulations   (Site not responding. Last check: 2007-10-15)
The most important practical case is that of a turbidity gravity current impact on a submarine oil or gas pipeline.
While forces from currents and waves are usually taken into account, very little is known about the forces involved in a potential impact from a gravity current.
Hence, high-accuracy numerical simulations of a compositional gravity current flow over a rather simple structure, a square cylinder, were performed to provide design criteria for the flow forces over the obstacle.
www.uweb.ucsb.edu /~esteban/gc_over_obstacle.htm   (792 words)

  
 BASIN: General Information on Turbidity
Turbidity is a measure of the cloudiness of water- the cloudier the water, the greater the turbidity.
Turbidity in water is caused by suspended matter such as clay, silt, and organic matter and by plankton and other microscopic organisms that interfere with the passage of light through the water (American Public Health Association, 1998).
A less expensive method of measuring turbidity is to evaluate the fuzziness of a mark at the bottom of a clear tube when a water sample is poured in the tube.
bcn.boulder.co.us /basin/data/FECAL/info/Turb.html   (723 words)

  
 Experimental Study of Reservoir Turbidity Current   (Site not responding. Last check: 2007-10-15)
A series of experiments were conducted in a flume to study the hydraulic characteristics of the turbidity current in a reservoir.
About 70% of the water discharge and 80% of the sediment discharge are confined to the denser layer, a layer close to the channel bed with approximately constant concentration.
The thickness of the turbidity current increases while the layer-averaged velocity and concentration decrease in the longitudinal direction; the layer-averaged velocity has the smallest variation rates.
www.pubs.asce.org /WWWdisplay.cgi?9702228   (187 words)

  
 Turbidity Currents   (Site not responding. Last check: 2007-10-15)
Turbidity currents are oceanic gravity currents which derive their motive force through suspended sediment.
Current laboratory models of these currents are performed in the tank shown below.
As the gate is lifted two opening simultaneously open allowing the turbidity current to flow out the bottom and a return flow in through the top.
www.physics.utoronto.ca /~nonlin/turbidity/jturbidite.html   (91 words)

  
 Turbidite Evidence for Cascadia Megathrust Earthquakes
When simultaneous turbidity currents from different side channels merge, the main channel can be expected to show a single large turbidite.
If this large tsunami did not trigger a turbidity current, it is highly unlikely the turbidite record reflects the occurrence of tsunamis.
Although these kinds of currents are likely to occur given enough time, the different rates of sedimentation and inclination of coastal regions make the synchronized turbidity currents implied shown in the core samples unlikely.
www.pnsn.org /HAZARDS/CASCADIA/turbidite_record.html   (506 words)

  
 Turbidity - Wikipedia, the free encyclopedia
Turbidity is a cloudiness or haziness of water (or other fluid) caused by individual particles (suspended solids) that are generally invisible to the naked eye, thus being much like smoke in air.
The higher the turbidity, the higher the risk of the drinkers developing gastrointestinal diseases, especially for immune-compromised people, because contaminants like virus or bacteria can become attached to the suspended solid.
Turbidity measured this way uses an instrument called a nephelometer with the detector setup to the side of the light beam.
en.wikipedia.org /wiki/Turbidity   (645 words)

  
 Sediment Gravity Flows   (Site not responding. Last check: 2007-10-15)
The suspended sediment in a turbidity current causes a density contrast between that and the ambient fluid, and the turbidity current will flow down slope, usually hugging the bottom.
Turbidity currents are caused by catastrophic failure along a shallow to steep slope (e.g.
Cohesive freezing of a subaqueous debris flow may produce a turbidity current as a suspended sediment resulting from turbulence associated with the debris flow may continue downslope.
www.umt.edu /geosciences/faculty/hendrix/g432/g432_L10.htm   (2749 words)

  
 Turbidity Meter and Turbidity Sensor for measurement, testing and analysis. Turbidity testing,water ...
In accordance with USEPA Method 180.1 for turbidity measurement, the Turbidity Sensor is a 90 degree scatter nephelometer.
The detected light intensity is directly proportional to the turbidity of the water.
The turbidity sensor utilizes a second light detector to correct for light intensity variations, color changes, and minor lens fouling.
www.globalw.com /products/turbidity.html   (368 words)

  
 The Dynamycs and Deposits of Lofting Turbidity Currents   (Site not responding. Last check: 2007-10-15)
The broad theme of my research is an investigation of the dynamics and deposits of lofting turbidity currents; in that, I will be examining the fluid dynamic processes in the lofting of density currents and also identify the key variables controlling the lofting behaviour.
Lofting behaviour in turbidity currents may possibly influence some of these deposits and more importantly the sorting of the grains in the deposits.
As outlined above, the rapid deceleration of the density current, caused by the continuation of sediment falling out of flow, just before lofting causes a rapid deposition of the sediment mass, which is clearly observed in the clefts and lobes structure in the deposit.
expage.com /page/theresearch   (484 words)

  
 Dukenvironment Magazine -- Spring 2005
But the currents also can have less dramatic causes, like the gradual buildup of excess sediment at the edge of the continental shelf.
Despite years of research, scientists still can’t predict with certainty where or when a turbidity current will occur, except in the relatively rare case when scientists know that a flooding river carries a concentration of suspended sediment that exceeds the concentration of sediment suspended in the basin into which it flows.
To reduce variables, scientists can simulate small-scale turbidity currents in the controlled environment of the laboratory using a special tank of water called a flume tank.
www.env.duke.edu /dukenvironment/sp05/f-utah2.html   (566 words)

  
 GEOL 4060 Lab #7- Turbidity Currents   (Site not responding. Last check: 2007-10-15)
As discussed in lecture last week, a turbidity current is a rapidly moving mixture of water in sediment that is responsible for much of the deposition of coarse-grained material in the deep ocean.
~ 7) initiated a large turbidity current that subsuquently broke a series of cables buried under the seafloor.
You are given a schematic of a turbidity current (figure1.pdf) to complete this part of the lab.
instaar.colorado.edu /ocean4060/labs/lab_7.html   (577 words)

  
 Ocean Planet:Tritium and Turbidity   (Site not responding. Last check: 2007-10-15)
The water had taken about 20 years to travel 3000 miles (4800 km) through the sea at an average speed of less than half a mile a day, about half the speed of a snail §.
Turbidity currents sweep sediment from shallow water to deep
Scientists calculated that the resulting turbidity current traveled 25-35 miles per hour (40-55 kph), and covered an area slightly larger than Maine and Connecticut §.
seawifs.gsfc.nasa.gov /OCEAN_PLANET/HTML/oceanography_currents_3.html   (183 words)

  
 Turbidity currents   (Site not responding. Last check: 2007-10-15)
The beginning of a turbidity current underflow is illustrated above.The turbid flow leaves the surface at the plunge point and continues as an underflow in the reservoir or basin.
On account of the shear at the interface between the underflow and the overlying basin water, some of the basin water is dragged down and a corresponding counterflow is induced in the upper portion of the basin.
The density currents that have a higher content of suspended sediment than the enclosing fluid are called turbidity currents or suspension currents.
home.swipnet.se /valter/tu.html   (175 words)

  
 Amateur Geologist Structured Geological Glossary: The Ocean
The continental rise is a depositional feature formed of sediment transported down the slope often by turbidity current.
A mass of mixed water and sediment that flows downhill along the bottom of an ocean or lake because it is denser than the surrounding water.
A subaqueous current that flows on the bottom of a sea or lake because entering water is more dense due to temperature or suspended sediment.
www.amateurgeologist.com /content/glossary/ocean/ocean.html   (1275 words)

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