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sediment

The Columbia Encyclopedia, 6th ed. | 2011 | Copyright

sediment mineral or organic particles that are deposited by the action of wind, water, or glacial ice. These sediments can eventually form sedimentary rocks (see rock ).

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 floodplains or carry these particles to the ocean, where they may be deposited as a delta . Ocean sediments, especially in the form of turbidites, are usually deposited at the foot of continental slopes (see oceans ). 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 conglomerates ; sands become sandstone ; and muds become shale . 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).

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sediment

The Oxford Pocket Dictionary of Current English | 2009 | Copyright

sed·i·ment / ˈsedəmənt/ • n. matter that settles to the bottom of a liquid; dregs. ∎ Geol. particulate matter that is carried by water or wind and deposited on the surface of the land or the bottom of a body of water, and may in time become consolidated into rock. • v. [intr.] settle as sediment. ∎ (of a liquid) deposit a sediment. ∎ [tr.] deposit (something) as a sediment: the DNA was sedimented by centrifugation | [as adj.] (sedimented) sedimented waste. DERIVATIVES: sed·i·men·ta·tion / ˌsedəmənˈtāshən/ n.

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"sediment." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

"sediment." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O999-sediment.html

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sediment

World Encyclopedia | 2005 | Copyright

sediment In geology, a general term used to describe any material (such as gravel, sand, and clay) that is transported and deposited by water, ice, wind, or gravity. The term includes material such as lime that is transported in solution and later precipitated, and organic deposits such as coal and coral reefs.

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sediment

A Dictionary of Earth Sciences | 1999 | | Copyright

sediment Material derived from pre-existing rock, from biogenic sources, or precipitated by chemical processes, and deposited at, or near, the Earth's surface.

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AILSA ALLABY and MICHAEL ALLABY. "sediment." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

AILSA ALLABY and MICHAEL ALLABY. "sediment." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O13-sediment.html

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sediment

A Dictionary of Ecology | 2004 | | Copyright

sediment Material derived from preexisting rock, from biogenic sources, or precipitated by chemical processes, and deposited at or near the Earth's surface.

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MICHAEL ALLABY. "sediment." A Dictionary of Ecology. 2004. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

MICHAEL ALLABY. "sediment." A Dictionary of Ecology. 2004. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O14-sediment.html

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sediment

The Concise Oxford Dictionary of English Etymology | 1996 | | Copyright

sediment XVI. — F. sēdiment or L. sedimentum settling, f. sedēre SIT, settle; see -MENT.

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T. F. HOAD. "sediment." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

T. F. HOAD. "sediment." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O27-sediment.html

T. F. HOAD. "sediment." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-sediment.html

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