Editing Orogeny

{{Short description|The formation of mountain ranges}}
{{Use dmy dates|date=March 2021}}
{{World geologic provinces}}

'''Orogeny''' ({{IPAc-en|ɒ|ˈ|r|ɒ|dʒ|ə|n|i}}) is a [[mountain]]-[[mountain formation|building]] process that takes place at a [[convergent boundary|convergent plate margin]] when plate motion compresses the margin. An {{em|[[orogenic belt]]}} or {{em|orogen}} develops as the compressed plate crumples and is [[tectonic uplift|uplifted]] to form one or more [[mountain range]]s. This involves a series of geological processes collectively called '''orogenesis'''. These include both structural [[deformation (physics)|deformation]] of existing [[continental crust]] and the creation of new continental crust through [[volcanism]]. [[Magma]] rising in the orogen carries less dense material upwards while leaving more dense material behind, resulting in compositional differentiation of Earth's [[lithosphere]] ([[crust (geology)|crust]] and uppermost [[mantle (geology)|mantle]]).<ref name=Waltham>{{cite book |title=Foundations of Engineering Geology |first=Tony|last=Waltham |page=20 |url=https://books.google.com/books?id=JGtIHJTXaI4C&pg=PA20 |isbn=978-0-415-46959-3 |publisher=[[Taylor & Francis]] |date=2009 |edition=3rd}}</ref><ref name=Vine>{{cite book |title=Global Tectonics |first1=Philip|last1=Kearey |first2=Keith A.|last2=Klepeis |first3=Frederick J.|last3=Vine |chapter-url=https://books.google.com/books?id=HYqZntfg25UC&pg=PA287 |page=287 |chapter=Chapter 10: Orogenic belts |isbn=978-1-4051-0777-8 |date=2009 |publisher=[[Wiley-Blackwell]] |edition=3rd}}</ref> A '''synorogenic''' (or '''synkinematic''') process or event is one that occurs during an orogeny.<ref>{{cite book |last1=Allaby|first1=Michael |title=A dictionary of geology and earth sciences |date=2013 |publisher=[[Oxford University Press]] |location=Oxford |isbn=9780199653065 |edition=Fourth |chapter=synorogenic}}</ref>

The word ''orogeny'' comes {{etymology|grc|''{{Wikt-lang|grc|ὄρος}}'' ({{grc-transl|ὄρος}})|mountain||''{{Wikt-lang|grc|γένεσις}}'' ({{grc-transl|γένεσις}})|creation, origin}}.<ref name="Chambers">{{cite encyclopedia |title=orogeny |encyclopedia=[[Chambers Dictionary|Chambers 21st Century Dictionary]] |publisher=Allied Publishers |date=1999 |page=972 |isbn=978-0550106254 |url=https://books.google.com/books?id=D37Cd3Ad7eIC&pg=PA972}}</ref> Although it was used before him, the American geologist [[Grove Karl Gilbert|G. K. Gilbert]] used the term in 1890 to mean the process of mountain-building, as distinguished from [[epeirogenic movement|epeirogeny]].<ref name="Friedman">{{cite book |chapter-url=https://books.google.com/books?id=AbECAQAAQBAJ&q=%22orogeny%22+gilbert&pg=PA160 |chapter=Pangean Orogenic and Epeirogenic Uplifts and Their Possible Climatic Significance |title=Pangea: Paleoclimate, Tectonics, and Sedimentation During Accretion, Zenith, and Breakup of a Supercontinent |editor-last=Klein|editor-first=G. O. |last=Friedman|first=G. M. |series=Geological Society of America Special Paper |volume=288 |year=1994 |page=160 |isbn=9780813722887 |publisher=[[Geological Society of America]]}}</ref>

==Tectonics==
{{See also|Subduction|Plate tectonics|Continental collision}}
[[File:Active Margin.svg|thumb|upright=1.2|[[Subduction]] of an [[oceanic plate]] beneath a [[Plate tectonics|continental plate]] to form an accretionary orogen (example: the [[Andes]]) ]]
[[File:Continental-continental convergence Fig21contcont.gif|thumb|upright=1.2|[[Continental collision]] of two continental plates to form a collisional orogen. Typically, continental crust is subducted to lithospheric depths for [[blueschist]] to [[eclogite facies]] metamorphism, and then exhumed along the same subduction channel. (example: the [[Himalayas]]) ]]
Orogeny takes place on the [[Convergent boundary|convergent margins]] of continents. The convergence may take the form of [[subduction]] (where a [[continent]] rides forcefully over an [[oceanic plate]] to form a noncollisional orogeny) or continental collision (convergence of two or more continents to form a collisional orogeny).<ref name= Press>{{cite book |title= Understanding Earth |author= Frank Press |url= https://books.google.com/books?id=P8iEVK1yGKwC&pg=PA468 |pages= 468–69 |isbn= 978-0-7167-9617-6 |edition= 4th |date= 2003 |publisher= Macmillan}}</ref>{{sfn|Kearey|Klepeis|Vine|2009|page=287}}

Orogeny typically produces ''orogenic belts'' or ''orogens'', which are elongated regions of deformation bordering continental [[craton]]s (the stable interiors of continents). Young orogenic belts, in which subduction is still taking place, are characterized by frequent [[volcanic activity]] and [[earthquake]]s. Older orogenic belts are typically deeply [[eroded]] to expose displaced and deformed [[strata]]. These are often highly [[metamorphosed]] and include vast bodies of [[intrusive igneous rock]] called [[batholith]]s.<ref name="levin-2010-83">{{cite book |last1=Levin |first1=Harold L. |title=The earth through time |date=2010 |publisher=J. Wiley |location=Hoboken, N.J. |isbn=978-0470387740 |page=83 |edition=9th}}</ref>

Subduction zones consume oceanic [[crust (geology)|crust]], thicken lithosphere, and produce earthquakes and volcanoes. Not all subduction zones produce orogenic belts; mountain building takes place only when the subduction produces compression in the overriding plate. Whether subduction produces compression depends on such factors as the rate of plate convergence and the degree of coupling between the two plates,{{sfn|Kearey|Klepeis|Vine|2009|page=289}} while the degree of coupling may in turn rely on such factors as the angle of subduction and rate of sedimentation in the oceanic trench associated with the subduction zone. The [[Andes Mountains]] are an example of a noncollisional orogenic belt, and such belts are sometimes called ''Andean-type orogens''.{{sfn|Kearey|Klepeis|Vine|2009|pages=287-288, 297-299}}

As subduction continues, [[island arc]]s, [[continental fragment]]s, and oceanic material may gradually accrete onto the continental margin. This is one of the main mechanisms by which continents have grown. An orogen built of crustal fragments (''[[terranes]]'') accreted over a long period of time, without any indication of a major continent-continent collision, is called an ''accretionary orogen.'' The [[North American Cordillera]] and the [[Lachlan Orogen]] of southeast Australia are examples of accretionary orogens.{{sfn|Kearey|Klepeis|Vine|2009|page=288}}

The orogeny may culminate with continental crust from the opposite side of the subducting oceanic plate arriving at the subduction zone. This ends subduction and transforms the accretional orogen into a [[Himalayas|Himalayan]]-type collisional orogen.<ref name="YuanEtAl2009">{{cite journal | title=Accretionary Orogenesis in the Active Continental Margins | first1=S. | last1=Yuan | first2=G. | last2=Pan | first3= L. | last3=Wang | first4=X. | last4=Jiang | first5=F. | last5=Yin | first6=W. | last6=Zhang | first7=J. | last7=Zhuo | journal=Earth Science Frontiers | year=2009 | volume=16 | issue=3 | pages=31–48 | doi=10.1016/S1872-5791(08)60095-0| bibcode=2009ESF....16...31Y }}</ref> The collisional orogeny may produce extremely high mountains, as has been taking place in the [[Himalayas]] for the last 65 million years.<ref>{{cite journal |last1=Ding |first1=Lin |last2=Kapp |first2=Paul |last3=Wan |first3=Xiaoqiao |title=Paleocene-Eocene record of ophiolite obduction and initial India-Asia collision, south central Tibet |journal=Tectonics |date=June 2005 |volume=24 |issue=3 |pages=n/a |doi=10.1029/2004TC001729|bibcode=2005Tecto..24.3001D |doi-access=free }}</ref>

The processes of orogeny can take tens of millions of years and build mountains from what were once [[sedimentary basin]]s.<ref name="levin-2010-83"/> Activity along an orogenic belt can be extremely long-lived. For example, much of the [[basement (geology)|basement]] underlying the United States belongs to the Transcontinental Proterozoic Provinces, which accreted to [[Laurentia]] (the ancient heart of North America) over the course of 200 million years in the [[Paleoproterozoic]].<ref>{{cite journal |last1=Anderson |first1=J. Lawford |last2=Bender |first2=E. Erik |last3=Anderson |first3=Raymond R. |last4=Bauer |first4=Paul W. |last5=Robertson |first5=James M. |last6=Bowring |first6=Samuel A. |last7=Condie |first7=Kent C. |last8=Denison |first8=Rodger E. |last9=Gilbert |first9=M. Charles |last10=Grambling |first10=Jeffrey A. |last11=Mawer |first11=Christopher K. |last12=Shearer |first12=C. K. |last13=Hinze |first13=William J. |last14=Karlstrom |first14=Karl E. |last15=Kisvarsanyi |first15=E. B. |last16=Lidiak |first16=Edward G. |last17=Reed |first17=John C. |last18=Sims |first18=Paul K. |last19=Tweto |first19=Odgen |last20=Silver |first20=Leon T. |last21=Treves |first21=Samuel B. |last22=Williams |first22=Michael L. |last23=Wooden |first23=Joseph L. |editor2-first=Marion E |editor2-last=Bickford |editor1-first=W. Randall Van |editor1-last=Schmus |title=Transcontinental Proterozoic provinces |journal=Precambrian |date=1993 |pages=171–334 |doi=10.1130/DNAG-GNA-C2.171|isbn=0813752183 }}</ref> The [[Yavapai orogeny|Yavapai]] and [[Mazatzal orogeny|Mazatzal orogenies]] were peaks of orogenic activity during this time. These were part of an extended period of orogenic activity that included the [[Picuris orogeny]] and culminated in the [[Grenville orogeny]], lasting at least 600 million years.<ref name="wk2007">{{cite journal |last1=Whitmeyer |first1=Steven |last2=Karlstrom |first2=Karl E. |journal=Geosphere |date=2007 |volume=3 |issue=4 |pages=220 |doi=10.1130/GES00055.1 |title=Tectonic model for the Proterozoic growth of North America|doi-access=free }}</ref> A similar sequence of orogenies has taken place on the west coast of North America, beginning in the [[late Devonian]] (about 380 million years ago) with the [[Antler orogeny]] and continuing with the [[Sonoma orogeny]] and [[Sevier orogeny]] and culminating with the [[Laramide orogeny]]. The Laramide orogeny alone lasted 40 million years, from 75 million to 35 million years ago.<ref>{{cite journal |last1=Bird |first1=Peter |title=Kinematic history of the Laramide orogeny in latitudes 35°-49°N, western United States |journal=Tectonics |date=October 1998 |volume=17 |issue=5 |pages=780–801 |doi=10.1029/98TC02698|bibcode=1998Tecto..17..780B |doi-access=free }}</ref>

=== Intraplate orogeny ===
Stresses transmitted from plate boundaries can also lead to episodes of intracontinental [[Transpression|transpressional]] orogeny. Examples in Australia include the  Neoproterozoic [[Petermann Orogeny]] (630–520 Ma),<ref>Quentin de Gromard, R., Howard, HM and Smithies, RH. (29 January 2020) [https://reportviewer.dmp.wa.gov.au/reportviewer/Default.aspx?reportPath=/ENS/Event%20Report&rs%3ACommand=Render&REGDEFID=PE Petermann Orogeny] ''Explanatory Notes.'' (online extract) Geological Survey of Western Australia. Retrieved 21 January 2025.</ref><ref>Quentin de Gromard, R., Kirkland, C.L., Howard, H.M., Wingate, M.T.D., Jourdan, F., McInnes, B.I.A., Danišík, M., Evans, N.J., McDonald, B.J., Smithies, R.H. (2019)
[https://www.sciencedirect.com/science/article/pii/S1674987118301993 When will it end? Long-lived intracontinental reactivation in central Australia], ''Geoscience Frontiers'', Volume 10, Issue 1, Pp. 149-164. Retrieved 21 January 2025.
{{ISSN|1674-9871}}, {{doi|10.1016/j.gsf.2018.09.003}}</ref> and the [[Sprigg Orogeny]] ([[Miocene]] – present).<ref>Sandiford, M.: Neotectonics of southeastern Australia: linking the Quaternary faulting record with seismicity and in situ stress. '''In''' Hillis, R. R. & Müller, R. D. (Editors) 2003. ''Evolution and Dynamics of the Australian Plate'', Pp 2, 107-120. Geological Society of Australia Special Publication 22 and Geological Society of America Special Paper 372.</ref><ref>Clark, D., McPherson, A. and Collins, C.D.N. 2011. Australia's seismogenic neotectonic record: a case for heterogeneous intraplate deformation. Record 2011/11. Geoscience Australia, Canberra.  Pp 46-47. {{isbn|978-1-921781-91-9}}</ref>

===Orogens===
{{main|Orogenic belt}}
[[File:ForelandBasinSystem.png|thumb|upright=1.75|right|The Foreland Basin System]]

Orogens show a great range of characteristics,<ref>{{cite journal |last1=Simandjuntak |first1=T. O. |last2=Barber |first2=A. J. |title=Contrasting tectonic styles in the Neogene orogenic belts of Indonesia |journal=Geological Society, London, Special Publications |date=1996 |volume=106 |issue=1 |pages=185–201 |doi=10.1144/GSL.SP.1996.106.01.12 |bibcode=1996GSLSP.106..185S |s2cid=140546624 |language=en |issn=0305-8719}}</ref><ref>{{cite journal |last1=Garzanti |first1=Eduardo |last2=Doglioni |first2=Carlo |last3=Vezzoli |first3=Giovanni |last4=Andò |first4=Sergio |title=Orogenic Belts and Orogenic Sediment Provenance |journal=The Journal of Geology |date=May 2007 |volume=115 |issue=3 |pages=315–334 |doi=10.1086/512755|bibcode=2007JG....115..315G |s2cid=67843559 }}</ref>
but they may be broadly divided into collisional orogens and noncollisional orogens (Andean-type orogens). Collisional orogens can be further divided by whether the collision is with a second continent or a continental fragment or island arc. Repeated collisions of the latter type, with no evidence of collision with a major continent or closure of an ocean basin, result in an accretionary orogen. Examples of orogens arising from collision of an island arc with a continent include [[Taiwan]] and the collision of Australia with the [[Banda Islands|Banda]] arc.{{sfn|Kearey|Klepeis|Vine|2009|pages=330-332}} Orogens arising from continent-continent collisions can be divided into those involving ocean closure (Himalayan-type orogens) and those involving glancing collisions with no ocean basin closure (as is taking place today in the [[Southern Alps]] of New Zealand).{{sfn|Kearey|Klepeis|Vine|2009|page=287}}

Orogens have a characteristic structure, though this shows considerable variation.{{sfn|Kearey|Klepeis|Vine|2009|page=287}} A ''foreland basin'' forms ahead of the orogen due mainly to loading and resulting [[lithospheric flexure|flexure of the lithosphere]] by the developing mountain belt. A typical foreland basin is subdivided into a wedge-top basin above the active orogenic wedge, the foredeep immediately beyond the active front, a forebulge high of flexural origin and a back-bulge area beyond, although not all of these are present in all foreland-basin systems.{{sfn|Kearey|Klepeis|Vine|2009|pages=302-303}} The basin migrates with the orogenic front and early deposited foreland basin sediments become progressively involved in folding and thrusting. [[Sediment]]s deposited in the foreland basin are mainly derived from the [[erosion]] of the actively uplifting rocks of the mountain range, although some sediments derive from the foreland. The fill of many such basins shows a change in time from deepwater marine (''[[flysch]]''-style) through shallow water to continental (''[[molasse]]''-style) sediments.<ref name="DeCelles&Giles">{{cite journal | url= http://www.geo.arizona.edu/geo5xx/geos517/pdfs/decelles_Giles96.pdf | title= Foreland basin systems | author= DeCelles P.G. & Giles K.A. | journal= Basin Research | year= 1996 | volume= 8 | issue= 2 | pages= 105–23 | doi= 10.1046/j.1365-2117.1996.01491.x | bibcode= 1996BasR....8..105D | access-date= 30 March 2015 | archive-url= https://web.archive.org/web/20150402091232/http://www.geo.arizona.edu/geo5xx/geos517/pdfs/decelles_Giles96.pdf | archive-date= 2 April 2015 | url-status= dead }}</ref>

While active orogens are found on the margins of present-day continents, older inactive orogenies, such as the [[Algoman orogeny|Algoman]],<ref name=billions>{{cite book|title=Billions of Years in Minnesota, The Geological Story of the State|author=Bray, Edmund C|year=1977|id=Library of Congress Card Number: 77:80265}}</ref> [[Penokean orogeny|Penokean]]<ref>{{cite journal
 | last1 = Schulz | first1 = K. J.
 | last2 = Cannon | first2 = W. F.
 | title = The Penokean orogeny in the Lake Superior region
 | year = 2007 | journal = Precambrian Research | volume = 157 | issue = 1 | pages = 4–25
 | url = https://www.researchgate.net/publication/248450648 | access-date = 6 March 2016
 | doi=10.1016/j.precamres.2007.02.022| bibcode = 2007PreR..157....4S}}<!-- {{Harvnb|Schulz|Cannon|2007}} -->
</ref> and [[Antler Orogeny|Antler]], are represented by deformed and metamorphosed rocks with sedimentary basins further inland.<ref name=Poole74>{{cite book|last=Poole|first=F.G.|year=1974|editor-last=Dickinson|editor-first=W.R.|title=Tectonics and Sedimentation|publisher=Society of Economic Paleontologists and Mineralogists|id=Special Publication 22|pages=58–82|chapter=Flysch deposits of the foreland basin, western United States|chapter-url=http://www.muststayawake.com/SDAG/library/PooleUSGS-halftones.pdf}}</ref>

==Orogenic cycle==
{{see also|Wilson Cycle}}
Long before the acceptance of [[plate tectonics]], geologists had found evidence within many orogens of repeated cycles of deposition, deformation, crustal thickening and mountain building, and crustal thinning to form new depositional basins. These were named ''orogenic cycles'', and various theories were proposed to explain them. Canadian geologist [[Tuzo Wilson]] first put forward a plate tectonic interpretation of orogenic cycles, now known as Wilson cycles. Wilson proposed that orogenic cycles represented the periodic opening and closing of an ocean basin, with each stage of the process leaving its characteristic record on the rocks of the orogen.<ref name=Twiss1992p493>{{cite book |author= Robert J. Twiss |author2= Eldridge M. Moores |title= Structural Geology |chapter-url= https://books.google.com/books?id=14fn03iJ2r8C&pg=PA493 |page= [https://archive.org/details/structuralgeolog0000twis/page/493 493] |chapter= Plate tectonic models of orogenic core zones |isbn= 978-0-7167-2252-6 |publisher= Macmillan |edition= 2nd |date= 1992 |url-access= registration |url= https://archive.org/details/structuralgeolog0000twis/page/493}}</ref>

===Continental rifting===
{{main|Continental rifting}}
The Wilson cycle begins when previously stable continental crust comes under tension from a shift in [[mantle convection]]. [[Continental rifting]] takes place, which thins the crust and creates basins in which sediments accumulate. As the basins deepen, the ocean invades the rift zone, and as the continental crust rifts completely apart, shallow marine sedimentation gives way to deep marine sedimentation on the thinned marginal crust of the two continents.{{sfn|Kearey|Klepeis|Vine|2009|pages=208-209}}<ref name=Twiss1992p493/>

===Seafloor spreading===
{{main|Seafloor spreading}}
As the two continents rift apart, [[seafloor spreading]] commences along the axis of a new ocean basin. Deep marine sediments continue to accumulate along the thinned continental margins, which are now [[passive margin]]s.{{sfn|Kearey|Klepeis|Vine|2009|pages=208-209}}<ref name=Twiss1992p493/>

===Subduction===
{{main|Subduction}}
At some point, subduction is initiated along one or both of the continental margins of the ocean basin, producing a [[volcanic arc]] and possibly an Andean-type orogen along that continental margin. This produces deformation of the continental margins and possibly crustal thickening  and mountain building.{{sfn|Kearey|Klepeis|Vine|2009|pages=208-209}}<ref name=Twiss1992p493/>

===Mountain building===
[[Image:SunRiver.JPG|thumb|250px|An example of [[thin-skinned deformation]] ([[thrust fault]]ing) of the [[Sevier Orogeny]] in [[Montana]]. The white [[Madison Limestone]] is repeated, with one example in the foreground (that pinches out with distance) and another to the upper right corner and top of the picture.]]
[[File:Sierra Nevada Mountains.JPG|thumb|250px|[[Sierra Nevada (U.S.)|Sierra Nevada Mountains]] (a result of [[delamination (geology)|delamination]]) as seen from the [[International Space Station]]]]

[[Mountain formation]] in orogens is largely a result of crustal thickening. The compressive forces produced by plate convergence result in pervasive deformation of the crust of the continental margin ([[thrust tectonics]]).<ref>{{cite journal |last1=Faccenna |first1=Claudio |last2=Becker |first2=Thorsten W. |last3=Holt |first3=Adam F. |last4=Brun |first4=Jean Pierre |title=Mountain building, mantle convection, and supercontinents: revisited |journal=Earth and Planetary Science Letters |date=June 2021 |volume=564 |pages=116905 |doi=10.1016/j.epsl.2021.116905|s2cid=234818905 |doi-access=free }}</ref> This takes the form of folding of the ductile deeper crust and thrust faulting in the upper brittle crust.<ref>{{cite book |last1=Howell |first1=David G. |title=Tectonics of Suspect Terranes |chapter=Mountain building and the shaping of continents |date=1989 |pages=157–199 |doi=10.1007/978-94-009-0827-7_6|isbn=978-94-010-6858-1 }}</ref>

Crustal thickening raises mountains through the principle of [[isostasy]].<ref name= Allen>{{cite book |title= Earth Surface Processes |author= PA Allen |chapter-url= https://books.google.com/books?id=e5i8cRGRCuwC&pg=PA36 |pages= 36 ff |chapter= Isostasy in zones of convergence |isbn= 978-0-632-03507-6 |date= 1997 |publisher= Wiley-Blackwell}}</ref> Isostacy is the balance of the downward [[Newton's law of universal gravitation|gravitational force]] upon an upthrust mountain range (composed of light, [[continental crust]] material) and the buoyant upward forces exerted by the dense underlying [[mantle (geology)|mantle]].<ref name=Wilcock>{{cite book |title= Mechanics in the Earth and Environmental Sciences |chapter= §5.5 Isostasy |page= 170 |chapter-url= https://books.google.com/books?id=K4IgLIDbZicC&pg=PA170|author= Gerard V. Middleton|author2= Peter R. Wilcock |isbn= 978-0-521-44669-3 |date= 1994 |publisher= Cambridge University Press |edition= 2nd}}</ref>

Portions of orogens can also experience uplift as a result of [[Delamination (geology)|delamination of the orogenic lithosphere]], in which an unstable portion of cold [[lithosphere|lithospheric]] root drips down into the asthenospheric mantle, decreasing the density of the lithosphere and causing buoyant uplift.<ref name="delamination_lee">{{cite journal|doi= 10.1126/science.289.5486.1912|pmid= 10988067|title= Osmium Isotopic Evidence for Mesozoic Removal of Lithospheric Mantle Beneath the Sierra Nevada, California|first5= SB|last5= Jacobsen|first4= JT|last4= Chesley|first3= RL|last3= Rudnick|first2= Q|date= 2000|last2= Yin|last1= Lee|first1= C.-T.|journal= Science|volume= 289|issue= 5486|pages= 1912–16|url= http://www.geol.umd.edu/~rudnick/Webpage/Lee_2000_Science.pdf|bibcode= 2000Sci...289.1912L|url-status= dead|archive-url= https://web.archive.org/web/20110615170551/http://www.geol.umd.edu/~rudnick/Webpage/Lee_2000_Science.pdf|archive-date= 15 June 2011}}</ref> An example is the [[Sierra Nevada (U.S.)|Sierra Nevada]] in California. This range of [[fault-block mountain]]s<ref name=Gerrard>{{cite book |title= Mountain Environments: An Examination of the Physical Geography of Mountains |author= John Gerrard |page= 9 |url= https://books.google.com/books?id=jHnrVEyMhkQC&pg=PA9 |isbn= 978-0-262-07128-4 |date= 1990|publisher= MIT Press}}</ref> experienced renewed uplift and abundant magmatism after a delamination of the orogenic root beneath them.<ref name="delamination_lee" /><ref>{{cite journal|doi= 10.1130/0091-7613(2000)28<811:TOVITS>2.0.CO;2|date= 2000|volume= 28|page= 811|title= Timing of Volcanism in the Sierra Nevada of California: Evidence for Pliocene Delamination of the Batholithic Root?|first3= G. Lang|last3= Farmer|first2= Allen F.|last2= Glazner|author= Manley, Curtis R.|journal= Geology|issue= 9|bibcode = 2000Geo....28..811M }}</ref>

[[File:Mount Rundle, Banff, Canada (200544945).jpg|thumb|[[Mount Rundle]], [[Banff, Alberta]]]]

[[Mount Rundle]] on the [[Trans-Canada Highway]] between [[Banff, Alberta|Banff]] and [[Canmore, Alberta|Canmore]] provides a classic example of a mountain cut in dipping-layered rocks. Millions of years ago a collision caused an orogeny, forcing horizontal layers of an ancient ocean crust to be thrust up at an angle of 50–60°. That left Rundle with one sweeping, tree-lined smooth face, and one sharp, steep face where the edge of the uplifted layers are exposed.<ref>{{cite web
|url= http://www.mountainnature.com/geology/platetectonics.htm
|title= The Formation of the Rocky Mountains
|work= Mountains in Nature
|date= n.d.
|access-date= 29 January 2014
|archive-date= 23 July 2014
|archive-url= https://web.archive.org/web/20140723230042/http://www.mountainnature.com/Geology/platetectonics.htm
|url-status= dead
}}</ref>

Although mountain building mostly takes place in orogens, a number of secondary mechanisms are capable of producing substantial mountain ranges.<ref name=Huggett>{{cite book |title= Fundamentals of Geomorphology |author= Richard J. Huggett |url= https://books.google.com/books?id=QY3-bBTUmKEC&pg=PA104 |page= 104 |isbn= 978-0-415-39084-2 |date= 2007 |publisher= Routledge |edition= 2nd}}</ref><ref name=Einsele>{{cite book |title= Sedimentary Basins: Evolution, Facies, and Sediment Budget |url= https://books.google.com/books?id=-N3nidyNoJUC&pg=PA453 |page= 453 |quote= Without denudation, even relatively low uplift rates as characteristic of epeirogenetic movements (''e.g.'' 20m/MA) would generate highly elevated regions in geological time periods. |author= Gerhard Einsele |isbn= 978-3-540-66193-1 |date= 2000 |edition= 2nd |publisher= Springer}}</ref><ref name=Douglas>{{cite book |title= Companion Encyclopedia of Geography: The Environment and Humankind |url= https://books.google.com/books?id=afH8DDAVkUQC&pg=PA33 |page= 33 |author= Ian Douglas |author2= Richard John Huggett |author3= Mike Robinson |isbn= 978-0-415-27750-1 |date= 2002 |publisher= Taylor & Francis}}</ref> Areas that are rifting apart, such as [[mid-ocean ridge]]s and the [[East African Rift]], have mountains due to thermal buoyancy related to the hot mantle underneath them; this thermal buoyancy is known as [[dynamic topography]]. In [[strike-slip]] orogens, such as the [[San Andreas Fault]], [[Thrust tectonics#Restraining bends on strike-slip faults|restraining bends]] result in regions of localized crustal shortening and mountain building without a plate-margin-wide orogeny. [[Hotspot (geology)|Hotspot]] volcanism results in the formation of isolated mountains and mountain chains that look as if they are not necessarily on present tectonic-plate boundaries, but they are essentially the product of plate tectonism. Likewise, uplift and erosion related to [[Epeirogenic movement|epeirogenesis]] (large-scale vertical motions of portions of continents without much associated folding, metamorphism, or deformation)<ref name=Holmes>{{cite book |title= Holmes Principles of Physical Geology |author= Arthur Holmes |author-link= Arthur Holmes|author2= Doris L. Holmes|author-link2 = Doris L. Holmes|url= https://books.google.com/books?id=E6vknq9SfIIC&pg=PT109 |page= 92 |isbn= 978-0-7487-4381-0 |edition= 4th |publisher= Taylor & Francis |date= 2004}}</ref> can create local topographic highs.

===Closure of the ocean basin===
Eventually, seafloor spreading in the ocean basin comes to a halt, and continued subduction begins to close the ocean basin.{{sfn|Kearey|Klepeis|Vine|2009|pages=208-209}}<ref name=Twiss1992p493/>

===Continental collision and orogeny===
{{main|Continental collision}}
The closure of the ocean basin ends with a continental collision and the associated Himalayan-type orogen.

===Erosion===
[[Erosion]] represents the final phase of the orogenic cycle. Erosion of overlying strata in orogenic belts, and isostatic adjustment to the removal of this overlying mass of rock, can bring deeply buried strata to the surface. The erosional process is called ''unroofing''.<ref>{{cite journal |last1=Sagripanti |first1=Lucía |last2=Bottesi |first2=Germán |last3=Kietzmann |first3=Diego |last4=Folguera |first4=Andrés |last5=Ramos |first5=Víctor A. |title=Mountain building processes at the orogenic front. A study of the unroofing in Neogene foreland sequence (37ºS) |journal=Andean Geology |date=May 2012 |volume=39 |issue=2 |pages=201–219 |doi=10.5027/andgeoV39n2-a01|doi-access=free |bibcode=2012AndGe..39b...1S |hdl=11336/68522 |hdl-access=free }}</ref> Erosion inevitably removes much of the mountains, exposing the core or ''mountain roots'' ([[metamorphic rocks]] brought to the surface from a depth of several kilometres). [[isostasy|Isostatic]] movements may help such unroofing by balancing out the buoyancy of the evolving orogen. Scholars debate about the extent to which erosion modifies the patterns of tectonic deformation (see [[erosion and tectonics]]). Thus, the final form of the majority of old orogenic belts is a long arcuate strip of crystalline metamorphic rocks sequentially below younger sediments which are thrust atop them and which dip away from the orogenic core.

An orogen may be almost completely eroded away, and only recognizable by studying (old) rocks that bear traces of orogenesis. Orogens are usually long, thin, arcuate tracts of rock that have a pronounced linear structure resulting in [[terrane]]s or blocks of deformed rocks, separated generally by [[Suture (geology)|suture zones]] or [[Strike and dip|dipping]] [[thrust fault]]s. These thrust faults carry relatively thin slices of rock (which are called [[nappe]]s or thrust sheets, and differ from [[tectonic plate]]s) from the core of the shortening orogen out toward the margins, and are intimately associated with [[fold (geology)|folds]] and the development of [[metamorphism]].<ref name=Merle>{{cite book |title= Emplacement Mechanisms of Nappes and Thrust Sheets|volume= 9|series= Petrology and Structural Geology |author= Olivier Merle |chapter= §1.1 Nappes, overthrusts and fold-nappes |pages= 1 ff |chapter-url =https://books.google.com/books?id=UJeVXaMhxI8C&pg=PA1 |isbn= 978-0-7923-4879-5 |publisher= Springer |date= 1998}}</ref>

==History of the concept==
Before the development of geologic concepts during the 19th century, the presence of marine [[fossil]]s in mountains was explained in [[Christianity|Christian]] contexts as a result of the Biblical [[Deluge (mythology)|Deluge]]. This was an extension of [[Neoplatonic]] thought, which influenced [[List of early Christian writers|early Christian writers]].<ref>{{cite journal |last1=Vai |first1=G.B. |year=2009 |title=The scientific revolution and Nicholas Steno's twofold conversion |journal=Geol Soc Am Mem |volume=203 |pages=187–208 |isbn=9780813712031 |url=https://books.google.com/books?id=4gGAgHcKX6YC&dq=fossils+and+the+noachian+deluge,+neoplatonism&pg=PA187 |access-date=17 April 2022}}</ref>

The 13th-century [[Dominican order|Dominican]] scholar [[Albert the Great]] posited that, as erosion was known to occur, there must be some process whereby new mountains and other land-forms were thrust up, or else there would eventually be no land; he suggested that marine fossils in mountainsides must once have been at the sea-floor.<ref>{{cite book |last1=Gohau |first1=Gabriel |title=A history of geology |date=1990 |publisher=Rutgers University Press |location=New Brunswick |isbn=9780813516660 |pages=26–27 |url=https://books.google.com/books?id=GBG7XDS5CbwC |access-date=17 April 2022}}</ref> Orogeny was used by [[Amanz Gressly]] (1840) and [[Jules Thurmann]] (1854) as ''orogenic'' in terms of the creation of mountain elevations, as the term ''mountain building'' was still used to describe the processes.<ref name="FrancoisEtal2021">{{cite journal |last1=François |first1=Camille |last2=Pubellier |first2=Manuel |last3=Robert |first3=Christian |last4=Bulois |first4=Cédric |last5=Jamaludin |first5=Siti Nur Fathiyah |last6=Oberhänsli |first6=Roland |last7=Faure |first7=Michel |last8=St-Onge |first8=Marc R. |title=Temporal and spatial evolution of orogens: a guide for geological mapping |journal=Episodes |date=1 October 2021 |volume=45 |issue=3 |pages=265–283 |doi=10.18814/epiiugs/2021/021025|s2cid=244188689 |doi-access=free }}</ref> [[Elie de Beaumont]] (1852) used the evocative "Jaws of a Vise" theory to explain orogeny, but was more concerned with the height rather than the implicit structures created by and contained in orogenic belts. His theory essentially held that mountains were created by the squeezing of certain rocks.<ref>{{cite book|last=Élie de Beaumont|first=JB|author-link=Jean-Baptiste Élie de Beaumont|year=1852|title=Notice sur les Systèmes de Montagnes|trans-title=Note on Mountain Systems|publisher=Bertrand|location=Paris|language=fr}} English synopsis in {{cite book|last=Dennis|first=John G.|year=1982|title=Orogeny|series=Benchmark Papers in Geology|volume=62|publisher=Hutchinson Ross Publishing Company|location=New York|isbn=978-0-87933-394-2}}</ref> [[Eduard Suess]] (1875) recognised the importance of horizontal movement of rocks.<ref>{{cite book|last=Suess|first=Eduard|year=1875|title=Die Entstehung Der Alpen|url=https://archive.org/details/dieentstehungde00suesgoog|trans-title=The Origin of the Alps|publisher=Braumüller|location=Vienna}}</ref> The concept of a ''precursor [[geosyncline]]'' or initial downward warping of the solid earth (Hall, 1859)<ref>{{cite journal|last=Hall|first=J|year=1859|title=Palaeontology of New York|journal=New York National Survey|volume=3|number=1}}</ref> prompted [[James Dwight Dana]] (1873) to include the concept of ''compression'' in the theories surrounding mountain-building.<ref>{{cite journal | last1 = Dana | first1 = James D. | date = 1873 | title = On Some Results of the Earth's Contraction From Cooling, Including a Discussion of the Origins of Mountains, and the Nature of the Earth's Interior |  journal = [[American Journal of Science]] | volume = 5 | issue = 30| pages = 423–43 | bibcode = 1873AmJS....5..423D | doi = 10.2475/ajs.s3-5.30.423 | s2cid = 131423196 | url = https://zenodo.org/record/1450110 }}</ref> With hindsight, we can discount Dana's conjecture that this contraction was due to the cooling of the Earth (aka the [[Geophysical global cooling|cooling Earth]] theory). The cooling Earth theory was the chief paradigm for most geologists until the 1960s. It was, in the context of orogeny, fiercely contested by proponents of vertical movements in the crust, or convection within the [[asthenosphere]] or [[mantle (geology)|mantle]].<ref name=Sengor1982>{{cite book |last=Şengör |first=Celâl|author-link=Celâl Şengör |date=1982|chapter=Classical theories of orogenesis|editor-last=Miyashiro|editor-first=Akiho|editor-link=Akiho Miyashiro|editor-last2=Aki|editor-first2=Keiiti|editor-last3=Şengör|editor-first3=Celâl |title=Orogeny |publisher=John Wiley & Sons |isbn=0-471-103764|ref=Sengor1982}}</ref>

[[Gustav Steinmann]] (1906) recognised different classes of orogenic belts, including the ''Alpine type orogenic belt'', typified by a [[flysch]] and [[molasse]] geometry to the sediments; [[ophiolite]] sequences, [[tholeiitic]] basalts, and a [[nappe]] style fold structure.

In terms of recognising orogeny as an ''event'', [[Leopold von Buch]] (1855) recognised that orogenies could be placed in time by bracketing between the youngest deformed rock and the oldest undeformed rock, a principle which is still in use today, though commonly investigated by [[geochronology]] using radiometric dating.<ref>{{cite book|last=Buch|first=L. Von|year=1902|title=Gesammelte Schriften|publisher=Roth & Eck|location=Berlin|language=de}}</ref>

Based on available observations from the metamorphic differences in orogenic belts of Europe and North America, [[Hendrik Jan Zwart|H. J. Zwart]] (1967)<ref>{{cite journal|last=Zwart|first=HJ|year=1967|title=The duality of orogenic belts|journal=Geol. Mijnbouw|volume=46|pages=283–309}}</ref> proposed three types of orogens in relationship to tectonic setting and style: Cordillerotype, Alpinotype, and Hercynotype. His proposal was revised by [[Wallace Spencer Pitcher|W. S. Pitcher]] in 1979<ref>{{cite journal|first=WS|last=Pitcher|title=The nature, ascent and emplacement of granitic magmas|journal=Journal of the Geological Society|year=1979|volume=136|issue=6|pages=627–62|doi=10.1144/gsjgs.136.6.0627|bibcode=1979JGSoc.136..627P|s2cid=128935736}}</ref> in terms of the relationship to granite occurrences. Cawood et al. (2009)<ref>{{cite book|last1=Cawood|first1=PA|last2=Kroner|first2=A|last3=Collins|first3=WJ|last4=Kusky|first4=TM|last5=Mooney|first5=WD|last6=Windley|first6=BF|year=2009|title=Accretionary orogens through Earth history|publisher=Geological Society|id=Special Publication 318|pages=1–36}}</ref> categorized orogenic belts into three types: accretionary, collisional, and intracratonic. Both accretionary and collisional orogens developed in converging plate margins. In contrast, Hercynotype orogens generally show similar features to intracratonic, intracontinental, extensional, and ultrahot orogens, all of which developed in continental detachment systems at converged plate margins.

# Accretionary orogens, which were produced by subduction of one oceanic plate beneath one continental plate for arc volcanism. They are dominated by calc-alkaline igneous rocks and high-T/low-P metamorphic facies series at high thermal gradients of >30&nbsp;°C/km. There is a general lack of ophiolites, migmatites and abyssal sediments. Typical examples are all circum-Pacific orogens containing continental arcs.
# Collisional orogens, which were produced by subduction of one continental block beneath the other continental block with the absence of arc volcanism. They are typified by the occurrence of blueschist to eclogite facies metamorphic zones, indicating high-P/low-T metamorphism at low thermal gradients of <10&nbsp;°C/km. Orogenic peridotites are present but volumetrically minor, and syn-collisional granites and migmatites are also rare or of only minor extent. Typical examples are the Alps-Himalaya orogens in the southern margin of Eurasian continent and the Dabie-Sulu orogens in east-central China.

==See also==
{{Portal|Earth sciences}}
{{colbegin}}
* {{annotated link|Biogeography}}
* {{annotated link|Epeirogenic movement}}
* {{annotated link|Fault mechanics}}
* {{annotated link|Fold mountains}}
* {{annotated link|Guyot}}
* {{annotated link|List of orogenies}}
* {{annotated link|Mantle convection}}
* {{annotated link|Tectonic uplift}}
{{colend}}

==References==
{{reflist|33em}}

== Further reading ==
* {{cite conference|last1=Harms|last2=Brady|last3=Cheney|year=2006|title=Exploring the Proterozoic Big Sky Orogeny in Southwest Montana|conference=19th annual Keck symposium}}
* {{cite book |title=Mountain Building in Scotland: Science : A Level 3 Course Series |author=Kevin Jones |isbn=978-0-7492-5847-4 |publisher=Open University Worldwide Ltd |date=2003}} provides a detailed history of a number of orogens, including the Caledonian Orogeny, which lasted from the late [[Cambrian]] to the [[Devonian]], with the main collisional events occurring during [[Ordovician]] and [[Silurian]] times.
* {{cite book |series=The Geology of Central Europe|volume=1|title=Precambrian and Palaeozoic |editor=Tom McCann |url=https://books.google.com/books?id=BR9FWgu2ps4C&q=orogeny |isbn=978-1-86239-245-8 |publisher=Geological Society of London |date=2008}} is one of a two-volume exposition of the geology of central Europe with a discussion of major orogens.
* {{cite book |title=Backbone of the Americas: Shallow Subduction, Plateau Uplift, and Ridge and Terrane Collision; Memoir 204 |editor=Suzanne Mahlburg Kay |editor2=Víctor A. Ramos |editor3=William R. Dickinson|editor-link2=Víctor Alberto Ramos |isbn=978-0-8137-1204-8 |date=2009 |publisher=Geological Society of America |url=https://books.google.com/books?id=ThpUlnCKwdgC}} Evolution of the Cordilleras of the Americas from a multidisciplinary perspective from a symposium held in Mendoza, Argentina (2006).

==External links==
{{Wikibooks|Historical Geology|Orogeny}}
{{commons category}}
* [https://web.archive.org/web/20080820030739/http://greenfield.fortunecity.com/shell/89/ Maps of the Acadian and Taconic orogenies]
* [https://web.archive.org/web/20081019222334/http://home.freeuk.com/gtlloyd/tam/geochron.htm Antarctic Geology]

{{Structural geology}}

{{Authority control}}

[[Category:Orogeny| ]]
[[Category:Geological processes]]
[[Category:Plate tectonics]]
[[Category:Mountain geomorphology]]
[[Category:Effects of gravity]]
[[Category:Events in the geological history of Earth]]