denude

(dĭ-nūd', -nyūd')

1. To divest of covering; make bare.
2. Geology. To expose (rock strata) by erosion.

[Latin dēnūdāre : dē-, de- + nūdāre, to make bare (from nūdus, nude).]

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All the weathering and erosional processes that contribute to the lowering of the land surface. Denudation is, thus, the complement of deposition, which is the accumulation of the products of denudation in sedimentation basins. See also Basin; Depositional systems and environments; Erosion; Weathering processes.

Contemporary records of sediment and solute flux through river systems, representing the mass removed from the continental surfaces, have been used to estimate rates of denudation since the mid-nineteenth century. These are usually expressed as an average rate of lowering of the land surface, in units of millimeters per thousand years (mm/ka).

In recent decades methods which allow the definition of denudation rates over geologic time scales have been developed. Attempts to invert sedimentary and stratigraphic records, and so define rates of erosion on the contributing continental surface, have greatly benefitted from improved seismic surveys, core extraction, and modeling of sedimentation basin processes. On the land surface itself, estimates of denudation rates based on the dissection of surfaces of known age have improved with the use of digital terrain models and absolute dating techniques. Equivalent estimates show that very rapid rates of bedrock denudation (up to 15 mm/yr) have been maintained in the western Himalaya during the past few million years. See also Dating methods.

Developments in the dating of bedrock surfaces and surficial material in the 1990s represent the greatest improvement in defining rates of denudation during the late Cenozoic era. Potassium-argon (K-Ar) dating of lavas and the magnitude of dissection on volcanic cones had been used earlier to define erosion rates. More recently, exposure dating of bedrock through the accumulation of cosmogenic nuclides produced within them is a development that allows the estimation of average surface lowering rates over long time intervals. Cosmogenic nuclides have also been used to define rates of regolith production and erosion, contributing to denudation, over more recent time periods. Fission track analysis of apatite is another recent development that has had success in defining the long-term tectonic and denudational history of continental margins and mountain systems. See also Apatite; Cenozoic; Cosmogenic nuclide; Fission track dating; Regolith.

verb

To make bare: bare, disrobe, divest, expose, strip, uncover. See put on/take off.

The laying bare of underlying rocks by the processes of weathering, transport, and erosion. The term may be used more narrowly to describe the removal of weathered rock and the exposure of the material beneath by mass wasting processes. Denudation chronology is the now somewhat outdated study of the long-term formation of specific landscapes.

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The stripping or laying bare of any part.

Schematic illustration of regional denudation for felsic alkaline intrusive rock bodies of the State of Rio de Janeiro, Brazil: Cabo Frio Island and Itaúna Body.

In geology, denudation is the long-term sum of processes that cause the wearing away of the earth’s surface leading to a reduction in elevation and relief of landforms and landscapes. Endogenetic processes such as volcanoes, earthquakes, and plate tectonics uplift and expose continental crust to the exogenetic denudation processes of weathering, erosion, and mass wasting.

Contents 1 Processes 2 Rates 3 Proposed cycles 4 Volcanic landforms 5 Medical use 6 References

Processes

Denudation incorporates mechanical, biological and chemical processes of erosion, weathering and mass wasting. Denudation can involve the removal of both solid particles and dissolved material. These include sub-processes of cryofracture, insolation weathering, slaking, salt weathering, bioturbation and anthropogenic impacts.^[1]

Factors affecting denudation include:

• Surface topography
• Geology
• Climate (most directly in chemical weathering)
• Tectonic activity
• Biosphere (fauna and flora)
• Anthropogenic activity

Rates

Modern denudation estimates are usually based on stream load measurements taken at gauging stations. Suspended load, bed load, and dissolved load are included in measurements. The weight of the load is converted to volumetric units and the load volume is divided by the area of the watershed above the gaging station. The result is an estimate of the wearing down of the Earth's surface in inches or centimeters per 1000 years.^[2] In most cases no adjustments are made for human impact, which causes the measurements to be inflated.^[3]

Denudation rates are usually much lower than the rates of uplift. The only areas at which there could be equal rates of denudation and uplift are active plate margins with an extended period of continuous deformation.^[4]

Proposed cycles

Early studies prompted the formation of denudation cycle hypotheses to describe land formations. Although at present they are mostly discounted, many of these models are enduring due to their simplicity and seemingly obvious assumptions.

In the 1890s W. M. Davis proposed a cycle of 'wearing down' in which so called 'young' landscapes had high gradients and elevations, and waning, low elevation topography through middle age to old age. Landscapes of Britain and Wales were thought to reflect these multiple peneplanation and rejuvenation cycles, such as the 3,000-foot remnant summit plateau in North Wales. A number of assumptions of fluvial and glacial dynamics in temperate areas were made in the formation of this model.

Such theories were proposed before tectonic theory was largely understood, and therefore are now largely discredited.

Volcanic landforms

A) Villarica Volcano, Chile, a volcano without effects of erosion and denudation
B) Chachahén Volcano, Mendoza, Argentina, a volcano with strong effect of erosion but no denudation
C) Cardiel Lake, Santa Cruz, Argentina, a volcanic area under strong effect of denudation, exposing subvolcanic rock body.^[5]

Denudation exposes deep sub-volcanic structures on the present surface of the area where volcanic activity once occurred. Sub-volcanic structures such as neck and dyke (volcanic vent) are exposed by denudation.

Medical use

In medicine, denudation refers to the loss of surface layers, such as the epithelium.

References

1. ^ Smithson, P et al (2008) Fundamentals of the Physical Environment (4th ed.)
2. ^ Ritter, D.F. 1967. Rates of denudation. Jour. Geol. Educ. 15, C.E.G.S. short rev. 6:154-59
3. ^ Judson, S. 1968. Erosion of the land. Am. Scientist 56:356-74
4. ^ Burbank, D.W., and Beck, R.A. 1991. Rapid long term rates of denudation. Geology 19:1169-72
5. ^ Motoki, Akihisa; Sichel, Susanna (in Brazilian Portuguese). Avaliação de aspectos texturais e estruturais de corpos vulcânicos e subvulcânicos e sua relação com oambiente de cristalização, com base em exemplos do Brasil, Argentina e Chile. http://www.scielo.br/pdf/rem/v59n1/a003.pdf. 

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Dansk (Danish)
v. tr. - klæde af, afdække, berøve, fratage

Nederlands (Dutch)
blootleggen, ontdoen (van)

Français (French)
v. tr. - (lit, fig) dénuder, dépouiller

Deutsch (German)
v. - abholzen, entziehen, berauben

Ελληνική (Greek)
v. - απογυμνώνω, ξεγυμνώνω, (μτφ.) αποστερώ

Italiano (Italian)
denudare

Português (Portuguese)
v. - desnudar

Русский (Russian)
обнажить, начисто уничтожить

Español (Spanish)
v. tr. - desnudar, descarnar, descortezar, denudar

Svenska (Swedish)
v. - blotta, beröva

中文（简体）(Chinese (Simplified))
使裸露, 剥夺, 剥下

中文（繁體）(Chinese (Traditional))
v. tr. - 使裸露, 剝奪, 剝下

한국어 (Korean)
v. tr. - 벗기다, 빼앗아 가다, (땅이) 척박하다

日本語 (Japanese)
v. - 裸にする, …からはぎ取る

العربيه (Arabic)
‏(فعل) يعري, يجرد‏

עברית (Hebrew)
v. tr. - ‮עירטל, חשף, הפשיט‬

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