Editing Mountain (section)

==Geology==
{{Main|Mountain formation|List of mountain types}}
There are three main types of mountains: [[volcanic]], [[fold mountain|fold]], and [[fault-block mountain|block]].<ref name="literacy">{{Cite book |title=Science matters: earth and beyond; module 4 |publisher=Pearson South Africa |year=2002 |isbn=0-7986-6059-7 |page=75 |chapter=Mountain building |chapter-url=https://books.google.com/books?id=qoZftjymxFsC&pg=PA75}}</ref> All three types are formed from [[plate tectonics]]: when portions of the Earth's crust move, crumple, and dive. Compressional forces, [[isostasy|isostatic]] [[Orogeny|uplift]] and intrusion of [[igneous rock|igneous matter]] forces surface rock upward, creating a landform higher than the surrounding features. The height of the feature makes it either a hill or, if higher and steeper, a mountain. Major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity.

===Volcanoes===
{{Main|Volcano}}
[[File:080103 hakkai fuji.jpg|thumb|[[Mount Fuji|Fuji volcano]]]]
Volcanoes are formed when [[subduction|a plate is pushed below another plate]], or at a [[mid-ocean ridge]] or [[hotspot (geology)|hotspot]].<ref name="Butz">{{Cite book |last=Butz |first=Stephen D. |url=https://archive.org/details/isbn_9780766833913/page/136 |title=Science of Earth Systems |publisher=Thompson |year=2004 |isbn=0-7668-3391-7 |page=[https://archive.org/details/isbn_9780766833913/page/136 136] |chapter=Plate tectonics |chapter-url=https://books.google.com/books?id=JB4ArbvXXDEC&pg=PA136}}</ref> At a depth of around {{cvt|100|km|mi|sp=us|sigfig=1}}, melting occurs in rock above the slab (due to the addition of water), and forms [[magma]] that reaches the surface. When the magma reaches the surface, it often builds a volcanic mountain, such as a [[shield volcano]] or a [[stratovolcano]].<ref name=Gerrard1990/>{{rp|194}} Examples of volcanoes include [[Mount Fuji]] in Japan and [[Mount Pinatubo]] in the Philippines. The magma does not have to reach the surface in order to create a mountain: magma that solidifies below ground can still form [[dome mountain]]s, such as [[Navajo Mountain]] in the US.<ref>{{Cite book |last=Fillmore |first=Robert |title=Geological evolution of the Colorado Plateau of eastern Utah and western Colorado, including the San Juan River, Natural Bridges, Canyonlands, Arches, and the Book Cliffs |date=2010 |publisher=University of Utah Press |isbn=978-1607810049 |location=Salt Lake City |page=430}}</ref>

===Fold mountains===
{{Main|Fold mountains}}
[[File:Lewis overthrust fault nh10f.jpg|thumb|Illustration of mountains that developed on a [[fold (geology)|fold]] that has been [[Thrust fault|thrust]]]]
Fold mountains occur when two plates collide: shortening occurs along thrust faults and the crust is overthickened.<ref name="Hatcher">{{Cite book |last=Searle |first=Michael P. |title=4-D framework of continental crust |publisher=Geological Society of America |year=2007 |isbn=978-0-8137-1200-0 |editor-last=Hatcher |editor-first=Robert D., Jr. |editor-link=Robert D. Hatcher |pages=41 ff |chapter=Diagnostic features and processes in the construction and evolution of Oman-, Zagros-, Himalayan-, Karakoram-, and Tibetan type orogenic belts |editor-last2=Carlson |editor-first2=M. P. |editor-last3=McBride |editor-first3=J. H. |editor-last4=Martinez Catalán |editor-first4=J. R. |chapter-url=https://books.google.com/books?id=jD-zXhTfJuMC&pg=PA41}}</ref> Since the less dense [[continental crust]] "floats" on the denser [[Mantle (geology)|mantle]] rocks beneath, the weight of any crustal material forced upward to form hills, [[plateau]]s or mountains must be [[isostasy|balanced by the buoyancy force]] of a much greater volume forced downward into the mantle. Thus the continental crust is normally much thicker under mountains, compared to lower lying areas.<ref>{{Cite book |last=Press |first=Frank |url=https://archive.org/details/earth0004pres/page/413 |title=Earth |last2=Siever |first2=Raymond |publisher=W.H. Freeman |year=1985 |isbn=978-0-7167-1743-0 |edition=4th |page=[https://archive.org/details/earth0004pres/page/413 413]}}</ref> Rock can [[fold (geology)|fold]] either symmetrically or asymmetrically. The upfolds are [[anticline]]s and the downfolds are [[syncline]]s: in asymmetric folding there may also be recumbent and overturned folds. The [[Balkan Mountains]]<ref>{{Cite journal |last=Hsü |first=Kenneth J. |last2=Nachev |first2=Ivan K. |last3=Vuchev |first3=Vassil T. |date=July 1977 |title=Geologic evolution of Bulgaria in light of plate tectonics |journal=Tectonophysics |volume=40 |issue=3–4 |pages=245–256 |bibcode=1977Tectp..40..245H |doi=10.1016/0040-1951(77)90068-3}}</ref> and the [[Jura Mountains]]<ref>{{Cite journal |last=Becker |first=Arnfried |date=June 2000 |title=The Jura Mountains — an active foreland fold-and-thrust belt? |journal=Tectonophysics |volume=321 |issue=4 |pages=381–406 |bibcode=2000Tectp.321..381B |doi=10.1016/S0040-1951(00)00089-5}}</ref> are examples of fold mountains.

===Block mountains===
{{Main|Block mountains}}
[[File:Vihren Pirin IMG 8898.jpg|thumb|alt=the highest summit of Pirin|[[Pirin|Pirin Mountain]], Bulgaria, part of the fault-block [[Rila]]-[[Rhodope Mountains|Rhodope]] massif]]
Block mountains are caused by [[fault (geology)|faults]] in the crust: a plane where rocks have moved past each other. When rocks on one side of a fault rise relative to the other, it can form a mountain.<ref name="Ryan">{{Cite book |last=Ryan |first=Scott |url=https://archive.org/details/cliffsquickrevie0000ryan |title=CliffsQuickReview Earth Science |publisher=Wiley |year=2006 |isbn=0-471-78937-2 |chapter=Figure 13-1 |chapter-url=https://books.google.com/books?id=PV_BabxTTkcC&pg=PA94 |url-access=registration}}</ref> The uplifted blocks are block mountains or [[Horst (geology)|horsts]]. The intervening dropped blocks are termed [[graben]]: these can be small or form extensive [[rift valley]] systems. This kind of landscape can be seen in [[East Africa]],<ref>{{Cite journal |last=Chorowicz |first=Jean |date=October 2005 |title=The East African rift system |journal=Journal of African Earth Sciences |volume=43 |issue=1–3 |pages=379–410 |bibcode=2005JAfES..43..379C |doi=10.1016/j.jafrearsci.2005.07.019}}</ref> the [[Vosges]] and [[Rhine graben|Rhine]] valley,<ref>{{Cite journal |last=Ziegler |first=P. A. |last2=Dèzes |first2=P. |date=July 2007 |title=Cenozoic uplift of Variscan Massifs in the Alpine foreland: Timing and controlling mechanisms |journal=Global and Planetary Change |volume=58 |issue=1–4 |pages=237–269 |bibcode=2007GPC....58..237Z |doi=10.1016/j.gloplacha.2006.12.004}}</ref> and the [[Basin and Range Province]] of Western North America.{{sfn|Levin|2010|pp=474-478}} These areas often occur when the regional stress is extensional and the [[crust (geology)|crust]] is thinned.{{sfn|Levin|2010|pp=474-478}}

===Erosion===
{{Main|Erosion}}
[[File:Valle Trebbia-(scaled-and-sharpened).jpg|thumb|right|[[Apennine Mountains]] and [[Trebbia]] river, Italy]]

During and following uplift, mountains are subjected to the agents of [[erosion]] (water, wind, ice, and gravity) which gradually wear the uplifted area down. Erosion causes the surface of mountains to be younger than the rocks that form the mountains themselves.<ref name=Fraknoi2004/>{{rp|160}} [[Glacier|Glacial processes]] produce characteristic landforms, such as [[pyramidal peak]]s, knife-edge [[arête]]s, and bowl-shaped [[cirque]]s that can contain lakes.<ref name="thornbury-1969">{{Cite book |last=Thornbury |first=William D. |title=Principles of geomorphology |publisher=Wiley |year=1969 |isbn=0471861979 |edition=2nd |location=New York |pages=358–376}}</ref> [[Plateau]] mountains, such as the [[Catskills]], are formed from the erosion of an uplifted plateau.<ref>{{Cite journal |last=Ver Straeten |first=Charles A. |date=July 2013 |title=Beneath it all: bedrock geology of the Catskill Mountains and implications of its weathering: Bedrock geology and weathering of the Catskills |journal=Annals of the New York Academy of Sciences |volume=1298 |pages=1–29 |doi=10.1111/nyas.12221 |pmid=23895551 |s2cid=19940868}}</ref>