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Sediment

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	Sediment
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	Topics Sediment Topic Home Sediment is any particulate matter that can be transported by fluid flowFluid dynamics Fluid dynamics is the subdiscipline of fluid mechanics that studies fluids in motion.... and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. Sedimentation is the deposition by settlingSettling Settling is the process by which particulates settle to the bottom of a liquid and form a sediment.... of a suspendedSuspension (chemistry) In chemistry, a suspension is a colloidal dispersion in which a finely-divided species is combined with another species, wit... material. Sediments are also transported by wind and glacierGlacier A glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity.... s. DesertDesert In geography, a desert is a landscape form or region that receives little precipitation.... sand dunes and loessFacts About Loess Among the classifications of soil types, loess is a fine, silty, windblown type of unconsolidated deposit; sometimes the ter... are examples of aeolian transport and deposition. Glacial moraineMoraine Moraine is rock debris, fallen or plucked from a mountain and transported by glaciers or ice sheets.... deposits and tillTill Till is an unsorted glacial sediment.... are ice transported sediments. Simple gravitational collapse also creates sediments such as talus and mountainslide deposits as well as karstKarst topography Karst topography is a three-dimensional landscape shaped by the dissolution of a soluble layer or layers of bedrock, usually... collapse features. Each sediment type has different settling velocities, depending on size, volume, density, and shape. SeaSea A sea is a large expanse of saline water connected with an ocean, or a large, usually saline, lake that lacks a natural outl... s, oceanOcean Oceans cover almost three quarters of the surface of the Earth, and nearly half of the world's marine waters are over 3,00... s, and lakeLake A lake is a body of water or other liquid of considerable size surrounded by land.... s accumulate sediment over time. These materials can be terrestrial (deposited on the land) or marine (deposited in the ocean); terrigenous deposits originate on land, but may be deposited in either terrestrial, marine, or lacustrine (lake) environments. Deposited sediments are the source of sedimentary rockSedimentary rock Sedimentary rock is one of the three main rock groups and is formed in three main ways—by the deposition of the weath... s, which can contain fossilFossil Fossils are the mineralized or otherwise preserved remains or traces of animals, plants, and other organisms.... s of the inhabitants of the body of water that were, upon death, covered by accumulating sediment. Lake bed sediments that have not solidified into rock can be used to determine past climaticClimate The climate is commonly considered to be the weather averaged over a long period of time, typically 30 years.... conditions. Sediment transport See also: Sediment transportFacts About Sediment transport Sediment transport is the movement of solid particles due to the movement of the fluid in which they are immersed.... Rivers and streams Sediment moves in a variety of ways, depending on a balance between the upwards velocity and the settling velocity on the particles in the bed. If the upwards velocity is greater than the settling velocity, sediment will be transported downstream as suspended load. As there will always be a range of different particle sizes in the flow, some will have sufficiently large diameters that they settle on the river or stream bed, but still move downstream. This is known as bed load and the particles are transported via such mechanisms as saltation (jumping up into the flow, being transported a short distance then settling again), rolling and sliding. Saltation marks are often preserved in solid rocks and can be used to estimate the flow rate of the rivers that originally deposited the sediments. The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equationExner equation The exner equation describes the conservation of mass of sediment in a fluvial system such as a river.... . This equation is important in that changes in flow depth and slope (see: depth-slope product) will change the basal shear stressShear stress In physics, shear stress is a stress state in which the shape of a material tends to change without particular volume change... , thus causing local areas of erosion and deposition. More large-scale changes such as dam emplacement and removal and sea-level variation change Base levelBase level The base level of a river or stream is the lowest point to which it can flow, often referred to as the 'mouth' of the river.... and cause the river to either pool (and deposit its entire load) or rapidly erode into its underlying substrate. Early applications of mathematical modeling of sediment transport in riverine systems were observed in the late 1970s. One such application was conducted by Santa Cruz CountySanta Cruz County, California Santa Cruz County is a county located on the Pacific coast of the U.S.... for the San Lorenzo RiverSan Lorenzo River The San Lorenzo River is a major river draining large watershed in Santa Cruz County, California.... to study erosionErosion Erosion is the displacement of solids by the agents of wind, water or ice, by downward or down-slope movement in response t... from surface runoffSurface runoff Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component o... and the resulting turbidityTurbidity Turbidity is a cloudiness or haziness of water caused by individual particles that are too small to be seen without magnific... and bedload transport to downstream reaches. This work was used to analyze effects of land use practices in this drainage basin. One of the main causes of riverine sediment load siltation stems from slash and burnSlash and burn Slash and burn is an agricultural procedure widely used in forested areas.... treatment of tropical forestForest A forest is an area with a high density of trees .... s. When the ground surface is stripped of vegetation and then seared of all living organisms, the upper soils are vulnerable to both wind and water erosion. In a number of regions of the earth, entire sectors of a country have been rendered erosive; for example, on the MadagascarMadagascar Madagascar, , is an island nation in the Indian Ocean, off the eastern coast of Africa, close to Mozambique.... high central plateauPlateau ... , comprising approximately ten percent of that country's land area, virtually the entire landscape is sterile of vegetationVegetation Overview Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants, and is, by fa... , with gully erosive furrows typically in excess of 50 meters deep and one kilometer wide. Shifting cultivationFacts About Shifting cultivation Shifting cultivation is an agricultural system in which a person uses a piece of land, only to abandon or alter the initial ... is a farming system which sometimes incorporates the slash and burnSlash and burn Slash and burn is an agricultural procedure widely used in forested areas.... method in some regions of the world. The resulting sediment load in rivers flowing to the west is ongoing, with most rivers a dark red brown colour, also leading to massive fish kills. Surface runoff Surface runoffSurface runoff Summary Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component o... water can pick up soil particles and transport them in overland flow for deposition at a lower land elevation or deliver that sediment to receiving waters. In this case the sediment is usually deemed to result from erosion. If the initial impact of rain droplets dislodges soil, the phenomenon is called splash erosion". If the effects are diffuse for a larger area and the velocity of moving runoff is responsible for sediment pickup, the effect is called "sheet erosion". If there are massive gouges in the earth from high velocity flow for uncovered soil, then "gully erosion" may result. Fluvial bedforms Any particle that is larger in diameter than approximately 0.7 mm will form visible topographic features on the river or stream bedStream bed A stream bed is the channel bottom of a stream or river or creek; the physical confine of the normal water flow.... . These are known as and include ripples, dunes, plane beds and antidunes. See bedforms for more detail. Again, bedforms are often preserved in sedimentary rocks and can be used to estimate the direction and magnitude of the depositing flow. Key depositional environments The major fluvial (river and stream) environments for deposition of sediments include: DeltasRiver delta A delta is a triangular shaped landform where the mouth of a river... (arguably an intermediate environment between fluvial and marine) Point-bars Alluvial fanAlluvial fan Summary An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exi... s Braided riverBraided river A braided river is one of a number of channel types and has a channel that consists of a network of small channels separated... s Oxbow lakeOxbow lake An oxbow lake is a type of lake which is formed when a wide meander from a stream or a river is cut off to form a lake.... s LeveeLevee A levee, leve , floodbank or stopbank is a natural or artificial embankment or dike, usually earthen, whic... s Shores and shallow seas The second major environment where sediment may be suspended in a fluid is in seas and oceans. The sediment could consist of terrigenous material supplied by nearby rivers and streams or reworked marine sediment (e.g. sandFacts About Sand Sand is an example of a class of materials called granular matter.... ). In the mid-ocean, living organisms are primarily responsible for the sediment accumulation, their shells sinking to the ocean floor upon death. Marine bedforms Marine environments also see the formation of bedforms, whose characteristics are influenced by the tides or currents. Key depositional environments The major areas for deposition of sediments in the marine environment include: LittoralLittoral Littoral refers to the coast or to the banks of a river, lake or estuary.... sands (e.g. beach sands, runoff river sands, coastal bars and spits, largely clasticSedimentary rock Sedimentary rock is one of the three main rock groups and is formed in three main ways—by the deposition of the weath... with little faunal content) The continental shelf. The shelf margin (low terrigenous supply, mostly calcareousCalcite The carbonate mineral calcite is a calcium carbonate corresponding to the formula CaCO3 and is one of the most widely distri... faunal skeletons) The shelf slope (much more fine-grained silts and clays) Beds of estuaries with the resultant deposits called "bay mudBay mud Overview Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are ... ". One other depositional environment which is a mixture of fluvial and marine is the turbiditeTurbidite Turbidite geological formations have their origins in turbidity current deposits, deposits from a form of underwater avalanc... system, which is a major source of sediment to the deep sedimentaryFacts About Sedimentary basin The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by se... and abyssal basinsAbyssal plain Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor.... as well as the deep oceanic trenchOceanic trench The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor.... es. See also Beach cuspsBeach cusps Beach cusps are shoreline formations made up of various grades of sediment in an arc pattern.... BiorhexistasyBiorhexistasy The Theory of Biorhexistasy describes climatic conditions necessary for periods of soil formation separated by periods of so... BioswaleBioswale Bioswales are landscape elements designed to remove silt and pollution from surface runoff water.... DecantationDecantation Decantation is a process for the separation of mixtures, carefully pouring a solution from a container, leaving the precipit... ErosionErosion Erosion is the displacement of solids by the agents of wind, water or ice, by downward or down-slope movement in response t... Exner equationExner equation The exner equation describes the conservation of mass of sediment in a fluvial system such as a river.... Gravel barGravel bar Gravel bars are hydrogeologic sediments that are prone to continuous erosion and migration.... Particle size RegolithRegolith Regolith is a layer of loose, heterogeneous material covering solid rock.... SandSand Sand is an example of a class of materials called granular matter.... Sedimentary depositional environmentSedimentary depositional environment In geology, sedimentary depositional environment describes the combination of physical, chemical and biological processes as... SettlingSettling Settling is the process by which particulates settle to the bottom of a liquid and form a sediment.... Surface runoffSurface runoff Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component o...