Temperature weathering

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Temperature weathering (also known as insolation weathering ) is a term for various weathering phenomena that are attributed to temperature fluctuations in the rock.

In particular in desert and arid polar regions as well as the summit regions of the eight-thousanders , which are characterized by very high temperature changes (either from positive to negative or fluctuations only in the deeply negative range), temperature weathering plays a prominent role in geomorphological processes.

theory

The heating or cooling of the surface of rock surfaces and stone structures causes an increase or decrease in volume in solids. Because of the mostly relatively low thermal conductivity of rocks, a temperature gradient develops . If the forces caused by the change in volume exceed the elastic limit of the rock-forming materials or their binding agent, the rock can break.

Research history

Originally, researchers assumed that the change in volume caused by temperature alone led to tensions in the rock and thus to fractures and splintering.

In a simplified assumption, the thermal expansion and modulus of elasticity (E-modulus) are proportional to the stress gradient . Depending on the material composition, binder, salt content, moisture, porosity and permeability, there are additional influences. Water or moisture play a major role in the effectiveness of weathering, while “dry” temperature weathering, without the effect of water, shows only minor characteristics. However, for selected examples it could be shown that dry insulation weathering can also lead to the formation of microcracks, which are important as the starting point for subsequent weathering phenomena.

Related processes

In many weathering processes, the temperature plays a role without the mechanism of action being mainly attributable to the change in temperature. This applies, for example, to the weathering of salt or frost bursting due to freeze-thaw cycles, for which the occurrence of water is obviously imperative. The temperature change only plays a subordinate role here.

High temperature effects come about through natural or man-made fire effects, which change the E-module of the surface and thus lead to rock disintegration. The term insolation weathering (which refers to solar radiation) is unsuitable for these processes.

Special forms of rock

Particularly pronounced sensitivity to temperature changes can be found in individual marble and limestone varieties due to the pronounced anisotropy of the modulus of elasticity of the rock-forming calcite . In the case of rocks that are sensitive to the sun, such as sunburner basalt, there are also chemical effects from the transformation of minerals.

See also

  • Firing , artificial application of temperature weathering in medieval mining

Individual evidence

  1. ^ Hans Murawski, Wilhelm Meyer: Geological dictionary . 11., revised. and exp. Edition. Elsevier, Spektrum Akademischer Verlag, Munich 2004, ISBN 3-8274-1445-8 .
  2. ↑ Alexander Stahr , Thomas Hartmann: Landscapes and landscape elements in the high mountains , Springer, Berlin / Heidelberg 1999, ISBN 978-3-540-65278-6 . P. 23.
  3. ^ A b Ronald U. Cooke, Andrew Warren, Andrew Goudie: Desert Geomorphology. Taylor & Francis, 1993, p. 28 ff.
  4. ↑ George Perkins Merrill : A Treatise on Rocks, Rock-Weathering, and Soils. 1897 (new edition: BiblioBazaar, LLC, 2008).

literature

  • Lukas Petersik: Physical weathering . In: Academic series . GRIN, Munich 2007, ISBN 978-3-638-76771-2 .
  • TP Burt, RJ Chorley, D. Brunsden, NJ Cox, AS Goudie: The History of the Study of Landforms Or the Development of Geomorphology . tape 4 : Quaternary and Recent Processes and Forms (1890-1965) and the Mid-century Revolutions . Geological Society, London 2008, ISBN 978-1-86239-249-6 .
  • D. Dragovich: Measuring stone weathering in cities: Surface reduction on marble monuments . In: Environmental Geology . Volume 9, No. 3 , 1987, ISSN  0943-0105 , pp. 139-141 .
  • Andreas Koch: Deformation of facade panels made of marble: Damage mapping and rock-technical investigations into the weathering dynamics of marble facades . Universitätsverlag, Göttingen 2006, ISBN 3-938616-47-4 , p. 89 ff . ( ediss.uni-goettingen.de [PDF] see section “Thermal and hygric weathering”).
  • Ulf Lindborg, Robert C. Dunakin: Thermal Stress and Weathering of Carrara, Pentelic and Ekeberg Marble . In: Vasco Fassina (Ed.): Proceedings of the 9th International Congress on Deterioration and Conservation of Stone, Venice, 19.-24. June 2000 . tape 1 . UNESCO, u. a., p. 109 ( limited preview in Google Book search).

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