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alluvium

 
Dictionary: al·lu·vi·um   (ə-lū'vē-əm) pronunciation
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n., pl., -vi·ums, or -vi·a (-vē-ə).
Sediment deposited by flowing water, as in a riverbed, flood plain, or delta. Also called alluvion.

[Medieval Latin, flood, from neuter of Latin alluvius, alluvial, from alluere, to wash against. See alluvion.]


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Geography Dictionary: alluvium
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A general term for all deposits laid down by present-day rivers, especially at times of flood. Alluvium is characterized by:

▪ sorting, so that coarser alluvium is found in the upper course of rivers and finer in the lower courses;
▪ stratification, such that coarse material in river bars is overlain by finer material;
▪ structures such as current bedding.

Alluvial landforms include alluvial cones and fans, deltas, river bed materials, and flood plains. Alluvial deposits are fertile, and can contain minerals, such as the alluvial gold and diamonds of West Africa. There is a tendency to restrict the term alluvium to fine-grained deposits such as silt or silty clays.

Architecture: alluvium
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Gravel, sand, silt, soil, or other material that is deposited by running water.

Archaeology Dictionary: alluvium
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[Ge]

A general term for sediment deposited by rivers, including that on the river bed, along its margins, across its floodplain, and in an estuary, if it has one. Alluvium tends to be rich in organic matter and may contain archaeological material. The onset of periods of rapid alluviation may also have the effect of sealing old land surfaces under the alluvium.
Word Tutor: alluvium
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pronunciation

IN BRIEF: n. - Clay or silt or gravel carried by rushing streams and deposited where the stream slows down.

Tutor's tip: "Alluvion" is the flow of water against a shore that sometimes deposits "alluvium" (silt or sand deposited by flowing water). When the wind deposits material such as sand or rock, the correct term is "eluvium."

Wikipedia: Alluvium
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"Alluvial" redirects here. For the American racehorse, see Alluvial (horse).
Section of alluvium at the Blue Ribbon Mine in Alaska
Alluvium deposits in the Gamtoos Valley in South Africa

Alluvium (from the Latin, alluvius, from alluere, "to wash against") is loose, unconsolidated (not cemented together into a solid rock), soil or sediments, eroded, deposited, and reshaped by water in some form in a non-marine setting.[1][2] Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel. When this loose alluvial material is deposited or cemented into a lithological unit, or lithified, it would be called an alluvial deposit.

The term "alluvium" is not typically used in situations where the formation of the sediment can clearly be attributed to another geologic process that is well described. This includes (but is not limited to): lake sediments (lacustrine), river sediments (fluvial), or glacially-derived sediments (glacial till). Sediments that are formed and/or deposited in a perennial stream or river are typically not referred to as alluvial.

Most, if not all, alluvium is very young (Quaternary in age), and is often referred to as "cover" because of the fact that these sediments obscure the underlying bedrock. Most sedimentary material that fills a basin ("basin fill") that is not lithified is typically lumped together in the term alluvial.

Alluvium can contain valuable ores such as gold and platinum and a wide variety of gemstones. Such concentrations of valuable ores is termed a placer deposit.

See also

References

  1. ^ http://www.geotech.org/survey/geotech/dictiona.html#sectA
  2. ^ http://geology.com/dictionary/glossary-a.shtml

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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
Geography Dictionary. A Dictionary of Geography. Copyright © Susan Mayhew 1992, 1997, 2004. All rights reserved.  Read more
Architecture. McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
Archaeology Dictionary. The Concise Oxford Dictionary of Archaeology. Copyright © 2002, 2003 by Oxford University Press. All rights reserved.  Read more
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Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Alluvium".  Read more