Diastrophism

Diastrophism refers to deformation of the Earth's crust, and more especially to folding and faulting. Diastrophism can be considered part of geotectonics. Diastrophism comes from the Greek word meaning a twisting.^[1][2]

All processes that move, elevate or build up portions of the earth’s crust come under diastrophism. They include: (i) orogenic processes involving mountain building through severe folding and affecting long and narrow belts of the earth’s crust; (ii) epeirogenic processes involving uplift or warping of large parts of the earth’s crust; (iii) earthquakes involving local relatively minor movements; (iv) plate tectonics involving horizontal movements of crustal plates.

Diastrophism covers movement of solid (plastic) crust material, as opposed to movement of molten material which is covered by volcanism. Movement causes rock to be bent or broken. The most obvious evidence of disastrophic movement can be seen where sedimentary rocks have been bent, broken or tilted. Such non-horizontal strata provide visual proof of movement. Diastrophic movement can be classified as two types, folding and faulting, tilted beds usually are part of a larger syncline or anticline. Diastrophic movement is often called orogenic as it is associated with mountain building.

There are various theories of the cause of diastrophic movement such as being the result of pressures exerted by convection currents in the mantle or the rise of magma through the crust. Other deformations are caused by meteorite impact and combinations of gravity and erosion such as landslides and slumping.^[3]

The study of diastrophism encompasses the varying responses of the crust to tectonic stresses. These responses include linear or torsional horizontal movements (such as continental drift) and vertical subsidence and uplift of the lithosphere (strain) in response to natural stresses on Earth’s surface such as the weight of mountains, lakes, and glaciers. Subsurface conditions also cause subsidence or uplift, known as epeirogeny, over large areas of Earth’s surface without deforming rock strata. Such changes include the thickening of the lithosphere by overthrusting, changes in rock density of the lithosphere caused by metamorphism or thermal expansion and contraction, increases in the volume of the asthenosphere (part of the upper mantle supporting the lithosphere) caused by hydration of olivine, and orogenic, or mountain-building, movements.

Historical development of the concept

By the end of the 19th Century it was generally accepted that the cause of folding and faults was lateral compression that resulted from a shrinking Earth caused by its gradual cooling.^[4] In the late 19th Century, Eduard Suess proposed his eustatic theory that provided the underpinnings for Chamberlin's explanation of disastrophism.^[5]

In volume two of Das Amlicz der Erde^[6] Suess set out his belief that across geologic time, the rise and fall of sea levels were mappable across the earth, that is, that the periods of ocean transgression and regression were correlatable from one continent to another. Suess postulated that as sediments filled the ocean basins the sea levels gradually rose, and periodically there were events of rapid ocean bottom subsidence that increased the ocean's capacity and caused the regressions. Chamberlin proposed that instead of a thermal contraction, diastrophic movement was caused by gravitational contraction.^[7] In the United States, it was not until the late 1960s that thermal convection replaced the shrinking Earth theories.^[7]

Notes

1. ^ "diastrophism". Merriam-Webster Online Dictionary. http://www.merriam-webster.com/dictionary/diastrophism. Retrieved 2009-03-12. 
2. ^ "A Word A Day for 17 August 2009: diastrophism". A Word A Day. http://wordsmith.org/words/diastrophism.html. Retrieved 2009-08-17. 
3. ^ Kallweit, Cheryl (February 1993). "Deformation Style and Structural Relationships Associated with a Well-Exposed Slump Block within the Tongue River Formation of the Fort Union Group, Carter County, Southeastern Montana". Geological Society of America, Abstracts with Programs 25 (1). ISSN 0016-7592. 
4. ^ Burt, T. P. et al. (eds.) (2008) The History of the Study of Landforms: Quaternary and recent processes and form (1890–1965) and the mid-century revolution. (volume 4 of The History of the Study of Landforms; or, The Development of Geomorphology), p. 77, ISBN 978-1-86239-249-6, citing: Dana, James D. (1873) "On some results of the earth's contraction from cooling, including a discussion of the origin of mountains, and the nature of the earth's interior" American Journal of Science (3rd series) Part I 5: pp.423–443; Part II 6: pp.6–14; Part IV pp.104–115 and Part V pp.161–171; as well as Iddings, Joseph P. (1914) The Problem of Volcanism Yale University Press, New Haven, Connecticut, OCLC 569285
5. ^ Chorley, Richard J. (1963) "Diastrophic Background to Twentieth-Century Geomorphological Thought" Geological Society of America Bulletin 74(8): pp. 953–970; abstract
6. ^ Suess, Eduard (1885–1908) Das Amlicz der Erde F. Tempsky, Vienna, OCLC 2903551, Note: volume 3 was published in two parts
7. ^ ^{a b} Dott, Robert H. (1997) "James Dwight Dana's old tectonics; global contraction under divine direction" American Journal of Science 297: pp.283–311, p. 283; abstract, citing Chamberlin, Thomas C. and Salisbury, Rollin D. (1904–1906) Geology (3 volumes) H. Holt, New York, OCLC 547718

Further reading

• Chorley, Richard J. (1963). "Diastrophic Background to Twentieth-Century Geomorphological Thought". Geological Society of America Bulletin 74(8): pp. 953–970.
• McKnight, Tom L; Hess, Darrel (2000). "The Internal Processes: Diastrophism". Physical Geography: A Landscape Appreciation. Upper Saddle River, NJ: Prentice Hall. p. 409. ISBN 0-13-020263-0. 

This tectonics article is a stub. You can help Wikipedia by expanding it.v · Categories: Structural geology Tectonics stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем написать реферат Four Saints in Three Acts Computer programs and the Patent Cooperation Treaty Look at other dictionaries: diastrophism — [dī as′trə fiz΄əm] n. [< Gr diastrophē, distortion < diastrephein, to turn aside, distort < dia , aside + strephein, to turn (see STROPHE) + ISM] 1. the process by which the earth s surface is reshaped through rock movements and… …   English World dictionary diastrophism — diastrophic /duy euh strof ik, stroh fik/, adj. diastrophically, adv. /duy as treuh fiz euhm/, n. Geol. 1. Also called tectonism. the action of the forces that cause the earth s crust to be deformed, producing continents, mountains, changes of… …   Universalium diastrophism — noun Etymology: Greek diastrophē twisting, from diastrephein to distort, from dia + strephein to twist Date: 1890 tectonism • diastrophic adjective • diastrophically adverb …   New Collegiate Dictionary diastrophism — noun The deformation of the Earths crust to form the continents, mountains and other large features …   Wiktionary diastrophism — Distortion that occurs in objects as a result of bending. [G. diastrophe, fr. diastrephein, distortion] …   Medical dictionary diastrophism —   movements producing positional changes in the crust. Orogenic changes are large scale folding and faulting processes which lead to landforms such as fold mountains. Epeirogenic changes are more gentle processes of uplift …   Geography glossary diastrophism — n. process through which the earth s crust changes, formation of land and mountains (Geology) …   English contemporary dictionary diastrophism — di·as·tro·phism …   English syllables diastrophism — di•as•tro•phism [[t]daɪˈæs trəˌfɪz əm[/t]] n. gel the action of the forces that cause the earth s crust to be deformed, producing continents, mountains, etc • Etymology: 1880–85; < Gk diastroph(ḗ) a distortion (n. der. of diastréphein to… …   From formal English to slang diastrophism — /daɪˈæstrəˌfɪzəm/ (say duy astruh.fizuhm) noun 1. the action of the forces which cause the earth s crust to be deformed, producing continents, mountains, changes of level, etc. 2. any such deformation. {Greek diastrophē distortion + ism}… …   18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”