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mineral or organic particles that are deposited by the action of wind, water, or glacial ice. These sediments can eventually form sedimentary rocks (see rockrock,
aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic.
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Classification of Sediments

Sediments are commonly subdivided into three major groups—mechanical, chemical, and organic.

Mechanical, or clastic, sediments are derived from the erosion of earlier formed rocks on the earth's surface or in the oceans. These are then carried by streams, winds, or glaciers to the site where they are deposited. Streams deposit sediment in floodplainsfloodplain,
level land along the course of a river formed by the deposition of sediment during periodic floods. Floodplains contain such features as levees, backswamps, delta plains, and oxbow lakes.
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 or carry these particles to the ocean, where they may be deposited as a deltadelta
[from triangular shape of the Nile delta, like the Greek letter delta], a deposit of clay, silt, and sand formed at the mouth of a river where the stream loses velocity and drops part of its sediment load.
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. Ocean sediments, especially in the form of turbidites, are usually deposited at the foot of continental slopes (see oceansocean,
interconnected mass of saltwater covering 70.78% of the surface of the earth, often called the world ocean. It is subdivided into four (or five) major units that are separated from each other in most cases by the continental masses. See also oceanography.
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). Glaciers carry sediment frozen within the mass of the ice and are capable of carrying even huge boulders (erratics).

Chemical sediments are formed by chemical reactions in seawater that result in the precipitation of minute mineral crystals, which settle to the floor of the sea and ultimately form a more or less chemically pure layer of sediment. For example, evaporation in shallow basins results in a sequence of evaporite sediments, which include gypsum and rock salt.

Organic sediments are formed as a result of plant or animal actions; for example, peat and coal form by the incomplete decay of vegetation and its later compaction. Deep-ocean sediment known as pelagic ooze consists largely of the remains of microscope organisms (mostly foraminifera and diatoms) from the overlying waters as well as minor amounts of windblown volcanic and continental dust. Limestones are commonly formed by the aggregation of calcite shells of animals.

Formation of Sedimentary Rock

Sediments form sedimentary rock by compaction and cementation of the particles. Thus, coarse sediments become conglomeratesconglomerate,
in geology, sedimentary rock composed largely of pebbles or other rounded particles whose diameter is larger than 2 mm (.08 in.). Essentially a cemented gravel, conglomerates are formed along beaches, as glacial drift, and in river deposits.
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; sands become sandstonesandstone,
sedimentary rock formed by the cementing together of grains of sand. The usual cementing material in sandstone is calcium carbonate, iron oxides, or silica, and the hardness of sandstone varies according to the character of the cementing material; quartz sandstones
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; and muds become shaleshale,
sedimentary rock formed by the consolidation of mud or clay, having the property of splitting into thin layers parallel to its bedding planes. Shale tends to be fissile, i.e., it tends to split along planar surfaces between the layers of stratified rock.
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. Sedimentary rocks make up only about 5% of all rocks of the earth's crust, yet they cover 75% of the land area in a veneer that averages 2.26 km (1.4 mi) in thickness, ranging from 0 to 12.9 km (0–8 mi).


Transported and deposited particles or aggregates derived from rocks, soil, or biological material.


A mass of organic or inorganic solid fragmented material, or the solid fragment itself, that comes from weathering of rock and is carried by, suspended in, or dropped by air, water, or ice; or a mass that is accumulated by any other natural agent and that forms in layers on the earth's surface such as sand, gravel, silt, mud, fill, or loess.
A solid material that is not in solution and either is distributed through the liquid or has settled out of the liquid.


The matter which settles to the bottom of water or any other liquid.


material that has been deposited from water, ice, or wind
References in periodicals archive ?
Direct measurements of residual snowpack and sediment cover were not collected at the end of 2003.
Sediments were allowed to soak overnight in seawater before each trial to allow a biofilm to accumulate.
Soil and polymer chemical properties determine whether soil particles will form micro- or macro-aggregates with different shapes and densities, and will determine the response of the aggregated sediment to runoff stresses (Rhoton et al.
Sedimentation remains a major problem in reservoirs which not only lessens the useful life of the reservoir but also causes abrasion of turbine units; when the sediment loaded water finds its way into the power house.
For instance, main dominant diatom taxa in surface sediments have not changed during more than 25 years (between the 1970s and 2006), indicating continuous eutrophic conditions (Puusepp & Punning 2011).
The main characteristic of submerged vanes, as a method for controlling the sediments entering the intake, is that due to the pressure difference between both sides of the vane, secondary flows are created behind the vanes which cause that the direction of approaching bed sediments are changed towards the middle of river.
Three sampling locations were selected so that the study would include sediments from drainage areas that ranged from 768 acres to 10,625 acres.
By measuring the radioactivity of suspended material moving down the river and comparing this with the radioactivity of sediments, the scientists can work out the relative contributions of each erosion process.
Practices used successfully to retain soil on croplands and mitigate the transport of sediments to surface waters include the use of polyacrylamide (PAM, a liquid or solid material synthesized from propylene) added to water to stabilize the soil (Sojka et al.
The tracks--some of them tens of meters across and as much as 6 m deep--are now buried by about 10 m of sediment that has accumulated on the lake floor since the icebergs plowed the region.
These background organisms are a concern because the bottom sediment is resuspended, along with the FIB persisting in the sediment, during high flow conditions.