Editing Basin and Range Province (section)

== Geology ==
It is generally accepted that basin and range topography is the result of extension and thinning of the [[lithosphere]], which is composed of [[Earth's crust|crust]] and [[Upper mantle (Earth)|upper mantle]].  Extensional environments like the Basin and Range are characterized by [[Listric fault|listric normal faulting]], or faults that level out with depth. Opposing normal faults link at depth producing a [[Horst (geology)|horst]] and [[graben]] geometry, where horst refers to the upthrown fault block and graben to the down dropped fault block.

The average crustal thickness of the Basin and Range Province is approximately 30–35&nbsp;km and is comparable to extended [[continental crust]] around the world.<ref>{{cite book|last1=Mooney|first1=Walter D|last2=Braile|first2=Lawrence W|chapter=The seismic structure of the continental crust and upper mantle of North America|title=The Geology of North America – An Overview|publisher=Geological Society of America|year=1989|page=42}}</ref> The crust in conjunction with the upper mantle comprises the [[lithosphere]]. The base of the lithosphere beneath the Basin and Range is estimated to be about 60–70&nbsp;km.<ref>{{cite journal|last1=Zandt|first1=G|first2=S|last2=Myers|first3=T|last3=Wallace|year=1995|title=Crust and mantle structure across the Basin and Range-Colorado Plateau boundary at 37°N latitude and implications for Cenozoic extensional mechanism|journal=J. Geophys. Res.|volume=100|number=B6|pages=10529–10548|doi=10.1029/94JB03063|bibcode=1995JGR...10010529Z}}</ref> Opinions vary regarding the total extension of the region; however, the median estimate is about 100% total lateral extension.<ref>{{cite web|url=http://geomaps.wr.usgs.gov/parks/province/basinrange.html|title=Geologic Provinces of the United States: Basin and Range Province|archive-url=https://web.archive.org/web/20090125163038/http://geomaps.wr.usgs.gov/parks/province/basinrange.html |archive-date=2009-01-25|publisher=United States Geological Survey}}</ref> Total lateral displacement in the Basin and Range varies from 60 to 300&nbsp;km since the onset of extension in the Early [[Miocene]] with the southern portion of the province representing a greater degree of displacement than the north. Evidence exists to suggest that extension initially began in the southern Basin and Range and propagated north over time.<ref>{{cite book|first1=Stephen L|last1=Salyards|first2=Eugene M|last2=Shoemaker|author1-link=Stephen L. Salyards|author2-link=Eugene Shoemaker|year=1987|chapter=Landslide and debris-flow deposits in the Thumb Member of the Miocene Horse Spring Formation on the east side of Frenchman Mountain, Nevada: A measure of basin-range extension|publisher=Cordilleran Section of the Geological Society of America|title=Centennial Field Guide|volume=1|editor-first=Mason L|editor-last=Hill|doi=10.1130/0-8137-5401-1.49}}</ref>

[[Clarence Dutton]] famously compared the many narrow parallel mountain ranges that distinguish the unique topography of the Basin and Range to an "army of caterpillars crawling northward."<ref>{{Cite journal|last=Dutton|first=Clarence|date=1885|title=Mount Taylor and the Zuni Plateau|url=https://ngmdb.usgs.gov/Prodesc/proddesc_92540.htm|journal=Sixth Annual Report of the United States Geological Survey to the Secretary of the Interior, 1884-1885|publisher=United States Geological Survey|pages=113–198|doi=10.3133/ar6|doi-access=free}}</ref>

===Tectonics===
[[File:MtMoriahNV.jpg|thumb|[[Snake Range]]]]
The tectonic mechanisms responsible for lithospheric extension in the Basin and Range province are controversial, and several competing hypotheses attempt to explain them. Key events preceding Basin and Range extension in the western United States include a long period of compression due to the [[subduction]] of the [[Farallon plate]] under the west coast of the North American continental plate which stimulated the thickening of the crust. Most of the pertinent tectonic plate movement associated with the province occurred in the [[Neogene]] period (23.03-2.58 million years ago) and continues to the present. By the Early [[Miocene]] sub-epoch (23.03-15.97 million years ago), much of the Farallon plate had been consumed, and the [[seafloor spreading ridge]] that separated the Farallon plate from the [[Pacific plate]] ([[Pacific-Farallon Ridge]]) approached North America.<ref name=Riney>{{cite web|last=Riney|first=Brad|url=http://www.oceanoasis.org/fieldguide/geology1.html|archive-url=https://web.archive.org/web/20110102140209/http://www.oceanoasis.org/fieldguide/geology1.html|archive-date=2011-01-02|title=Plate Tectonics|work=Ocean Oasis Field Guide|publisher=San Diego Natural History Museum|year=2000|access-date=5 Dec 2010}}</ref> In the Middle [[Miocene]] (15.97-11.63 million years ago), the Pacific-Farallon Ridge was subducted beneath North America ending [[subduction]] along this part of the Pacific margin; however, the Farallon plate continued to subduct into the [[Earth's mantle|mantle]].<ref name=Riney/> The movement at this boundary divided the Pacific-Farallon Ridge and spawned the [[San Andreas Fault|San Andreas]] [[transform fault]], generating an oblique [[strike-slip]] component.<ref>{{cite web|url=http://geology.isu.edu/Digital_Geology_Idaho/Module9/mod9.htm|work=Digital Geology of Idaho|title=Basin and Range Province – Tertiary Extension|access-date=5 Dec 2010|archive-date=11 September 2019|archive-url=https://web.archive.org/web/20190911200732/http://geology.isu.edu/Digital_Geology_Idaho/Module9/mod9.htm|url-status=dead}}</ref> Today, the Pacific plate moves north-westward relative to North America, a configuration which has given rise to increased shearing along the [[continental margin]].<ref name=Riney/>

The tectonic activity responsible for the extension in the Basin and Range is a complex and controversial issue among the geoscience community. The most accepted hypothesis suggests that crustal [[Shear (geology)|shearing]] associated with the [[San Andreas Fault]] caused spontaneous extensional faulting similar to that seen in the Great Basin.<ref name=Stanley>{{cite book|last=Stanley|first=SM|year=2005|title=Earth system history|location=New York|publisher=Freeman}}</ref> However, plate movement alone does not account for the high elevation of the Basin and Range region.<ref name=Stanley/> The western United States is a region of high [[heat transfer|heat flow]] which lowers the density of the lithosphere and stimulates [[isostasy|isostatic]] [[Uplift (geology)|uplift]] as a consequence.<ref>{{cite web|archive-url=https://web.archive.org/web/20101031185845/http://www.enotes.com/earth-science/basin-range-topography|url=http://www.enotes.com/earth-science/basin-range-topography|archive-date=2010-10-31|title=Basin and Range Topography|work=World of Earth Science|editor-first1=Lee|editor-last1=Lerner|editor-first2=Brenda Wilmoth|editor-last2=Lerner|first=Gale|last=Cengage|year=2003|publisher=eNotes.com|access-date=5 Dec 2010}}</ref> Lithospheric regions characterized by elevated heat flow are weak and extensional deformation can occur over a broad region. Basin and Range extension is therefore thought to be unrelated to the kind of extension produced by [[mantle convection|mantle upwelling]] which may cause narrow rift zones, such as those of the [[Afar triple junction]].<ref>{{citation|last=Stern|first=Robert J|type=Class Notes|title=Rifts|work=Physics and Chemistry of the Solid Earth|publisher=University of Texas at Dallas|location=Dallas, Texas|date=2010-09-01}}</ref> Geologic processes that elevate heat flow are varied, however some researchers suggest that heat generated at a subduction zone is transferred to the overriding plate as subduction proceeds. Fluids along fault zones then transfer heat vertically through the crust.<ref>{{cite journal|first1=Makoto|last1=Yamano|first2=Masataka|last2=Kinoshita|first3=Shusaku|last3=Goto|title=High heat flow anomalies on an old oceanic plate observed seaward of the Japan Trench|journal=International Journal of Earth Sciences|year=2008|volume=97|issue=2|pages=345–352|doi=10.1007/s00531-007-0280-1|bibcode=2008IJEaS..97..345Y|s2cid=129417881}}</ref> This model has led to increasing interest in [[Geothermal gradient|geothermal systems]] in the Basin and Range, and requires consideration of the continued influence of the fully subducted Farallon plate in the extension responsible for the Basin and Range Province.

===Metamorphic core complexes===
In some localities in the Basin and Range, metamorphic basement is visible at the surface. Some of these are [[metamorphic core complex]]es (MCC), an idea that was first developed based on studies in this province. A metamorphic core complex occurs when lower crust is brought to the surface as a result of extension. MCCs in the Basin and Range were not interpreted as being related to crustal extension until after the 1960s. Since then, similar deformational patterns have been identified in MCCs in the Basin and Range and has led geologists to examine them as a group of related geologic features formed by crustal extension during the [[Cenozoic]] era (66.0 million years ago to present). The study of metamorphic core complexes has provided valuable insight into the extensional processes driving Basin and Range formation.<ref>{{cite web|last=Rystrom|first=VL|url=http://www.colorado.edu/GeolSci/Resources/WUSTectonics/CoreComplex/5700.html|title=Metamorphic Core Complexes|archive-url=https://web.archive.org/web/20101103161632/http://www.colorado.edu/GeolSci/Resources/WUSTectonics/CoreComplex/5700.html |archive-date=2010-11-03|year=2000|access-date=5 Dec 2010}}</ref>

=== Volcanism ===
{{main|List of large volume volcanic eruptions in the Basin and Range Province}}
{{See also|Geologic timeline of Western North America|Yellowstone hotspot}}

Prior to the Eocene Epoch (55.8 ±0.2 to 33.9 ±0.1&nbsp;Ma) the convergence rate of the Farallon and North American plates was fast, the angle of subduction was shallow, and the slab width was huge. During the [[Eocene]] the [[Farallon plate]] [[subduction]]-associated compressive forces of the [[Laramide orogeny|Laramide]], [[Sevier orogeny|Sevier]] and [[Nevada orogeny|Nevada]] orogenies ended, plate interactions changed from orthogonal compression to [[Fault (geology)|oblique strike-slip]], and volcanism in the Basin and Range Province flared up ([[Mid-Tertiary ignimbrite flare-up]]). It is suggested that this plate continued to be underthrust until about 19&nbsp;Ma, at which time it was completely consumed and volcanic activity ceased, in part. [[Olivine basalt]] from the [[oceanic ridge]] erupted around 17&nbsp;Ma and [[extension (geology)|extension]] began.<ref>{{cite journal
 |last= McKee |first= E. H.   |year= 1971 |title= Tertiary Igneous Chronology of the Great Basin of Western United States – Implications for Tectonic Models |journal= Geological Society of America Bulletin |volume= 82 |issue= 12 |pages= 3497–3502 |doi = 10.1130/0016-7606(1971)82[3497:ticotg]2.0.co;2|bibcode = 1971GSAB...82.3497M }}</ref><ref>{{cite web
 |url = http://www.washington.edu/burkemuseum/geo_history_wa/index.htm
 |title = Northwest Origins, An Introduction to the Geologic History of Washington State, Catherine L. Townsend and John T. Figge |publisher = The Burke Museum of Natural History and Culture, University of Washington |access-date = 2010-04-10 }}</ref><ref>
{{cite web |url = http://www.oregongeology.com/sub/publications/ims/ims-028/index.htm |title = Oregon: A Geologic History |publisher = Oregon Department of Geology and Mineral Industries |access-date = 2010-03-26 |archive-url = https://web.archive.org/web/20100128052050/http://www.oregongeology.com/sub/publications/IMS/ims-028/index.htm |archive-date = 2010-01-28 |url-status = usurped }}
</ref><ref>{{cite web |url = http://geology.isu.edu/Digital_Geology_Idaho/Module1/mod1.htm |title = Digital Geology of Idaho, Laura DeGrey and Paul Link |publisher = Idaho State University |access-date = 2010-04-10 |archive-date = 2018-07-21 |archive-url = https://web.archive.org/web/20180721185108/http://geology.isu.edu/Digital_Geology_Idaho/Module1/mod1.htm |url-status = dead }}</ref>

=== Volcanic areas ===
{{div col|colwidth=30em}}
* [[Great Basin]] volcanism:
** [[Yucca Mountain|Southwestern Nevada volcanic field]] (SWNVF)
** [[Reveille Range|Réveille Range]] and [[Lunar Crater volcanic field]]
** [[Indian Peak volcanic field]], [[Nevada]]/[[Utah]]
** [[Marysvale Volcanic Field|Marysvale volcanic field]], [[Utah]]
* [[Mogollon-Datil volcanic field]]:
** [[Bursum calderas|Bursum]]
** [[Emory calderas|Emory]]
** [[Organ calderas|Organ]] ([[Las Cruces, New Mexico|Las Cruces]], [[Doña Ana Mountains]], [[Organ Mountains]])
** [[Socorro caldera]]s
* The [[Jemez Lineament]]:
** [[San Carlos volcanic field]]
** [[Springerville volcanic field]]
** [[Red Hill volcanic field]]<ref>{{cite book | last = Wood | first = Charles A. |author2=Jűrgen Kienle | title = Volcanoes of North America | publisher = [[Cambridge University Press]] | year = 1993 | pages = 284–86 | isbn = 978-0521438117 }}</ref>
** [[Zuni-Bandera volcanic field]]
** [[Mount Taylor (New Mexico)|Mount Taylor volcanic field]]
** [[Jemez Mountains|Jemez volcanic field]]
* [[Trans-Pecos|Trans-Pecos volcanic field]]:
** [[Big Bend National Park]]
** [[Davis Mountains]]
{{div col end}}