Editing Rift (section)

==Rift development==

===Rift initiation===
The formation of rift basins and strain localization reflects rift maturity. At the onset of rifting, the upper part of the lithosphere starts to extend on a series of initially unconnected [[normal fault]]s, leading to the development of isolated basins.<ref name="Withjack">{{cite book|last=Withjack|first=M.O. |author2=Schlische R.W. |author3=Olsen P.E.|title=Sedimentation in Continental Rifts|editor=Renaut R.W. & Ashley G.M.|publisher=Society for Sedimentary Geology|year=2002|series=Special Publications|volume=73|chapter=Rift-basin structure and its influence on sedimentary systems|chapter-url=http://www.rci.rutgers.edu/~schlisch/A33_2002_SEPM_rifts.pdf|access-date=28 October 2012}}</ref> In subaerial rifts, for example, drainage at the onset of rifting is generally internal, with no element of through drainage.

===Mature rift stage===
As the rift evolves, some of the individual fault segments grow, eventually becoming linked together to form the larger bounding faults. Subsequent extension becomes concentrated on these faults. The longer faults and wider fault spacing leads to more continuous areas of fault-related [[subsidence]] along the rift axis. Significant uplift of the rift shoulders develops at this stage, strongly influencing drainage and sedimentation in the rift basins.<ref name="Withjack"/>

During the climax of lithospheric rifting, as the crust is thinned, the Earth's surface subsides and the [[Mohorovičić discontinuity|Moho]] becomes correspondingly raised. At the same time, the mantle lithosphere becomes thinned, causing a rise of the top of the asthenosphere. This brings high heat flow from the upwelling asthenosphere into the thinning lithosphere, heating the orogenic lithosphere for dehydration melting, typically causing extreme metamorphism at high thermal gradients of greater than 30&nbsp;°C. The metamorphic products are high to ultrahigh temperature granulites and their associated migmatite and granites in collisional orogens, with possible emplacement of metamorphic core complexes in continental rift zones but oceanic core complexes in spreading ridges. This leads to a kind of orogeneses in extensional settings, which is referred as to rifting orogeny.<ref>{{cite journal | last1 = Zheng | first1 = Y.-F. | last2 = Chen | first2 = R.-X. | year = 2017 | title = Regional metamorphism at extreme conditions: Implications for orogeny at convergent plate margins | journal = Journal of Asian Earth Sciences | volume = 145 | pages = 46–73 | doi = 10.1016/j.jseaes.2017.03.009 | bibcode = 2017JAESc.145...46Z | doi-access = free }}</ref>

===Post-rift subsidence===
Once rifting ceases, the mantle beneath the rift cools and this is accompanied by a broad area of post-rift subsidence. The amount of subsidence is directly related to the amount of thinning during the rifting phase calculated as the beta factor (initial crustal thickness divided by final crustal thickness), but is also affected by the degree to which the rift basin is filled at each stage, due to the greater density of sediments in contrast to water. The simple 'McKenzie model' of rifting, which considers the rifting stage to be instantaneous, provides a good first order estimate of the amount of crustal thinning from observations of the amount of post-rift subsidence.<ref name="McKenzie">{{cite journal|last=McKenzie|first=D.|year=1978|title=Some remarks on the development of sedimentary basins|journal=Earth and Planetary Science Letters|volume=40|issue=1|pages=25–32|url=http://www.earth.ox.ac.uk/~tony/watts/downloads/McKenzie_1978_Basins.pdf|access-date=25 October 2012|doi=10.1016/0012-821x(78)90071-7|archive-url=https://web.archive.org/web/20140301085415/http://www.earth.ox.ac.uk/~tony/watts/downloads/McKenzie_1978_Basins.pdf|archive-date=1 March 2014|citeseerx=10.1.1.459.4779|bibcode=1978E&PSL..40...25M}}</ref><ref name="Kusznir">{{cite book|last=Kusznir|first=N.J. |author2=Roberts A.M. |author3=Morley C.K.|title=Hydrocarbon habitat in rift basins|editor=Lambiase J.J.|publisher=[[Geological Society]]|location=London|year=1995|series=Special Publications|volume=80|pages=33–56|chapter=Forward and reverse modelling of rift basin formation|isbn=9781897799154|chapter-url=http://sp.lyellcollection.org/content/80/1/33.abstract|access-date=25 October 2012}}</ref> This has generally been replaced by the 'flexural cantilever model', which takes into account the geometry of the rift faults and the [[Lithospheric flexure|flexural]] [[isostasy]] of the upper part of the crust.<ref name="Nøttvedt">{{cite journal|last=Nøttvedt|first=A. |author2=Gabrielsen R.H. |author3=Steel R.J.|year=1995|title=Tectonostratigraphy and sedimentary architecture of rift basins, with reference to the northern North Sea|journal=[[Marine and Petroleum Geology]]|volume=12|issue=8|pages=881–901|doi=10.1016/0264-8172(95)98853-W|bibcode=1995MarPG..12..881N }}</ref>

===Multiphase rifting===
Some rifts show a complex and prolonged history of rifting, with several distinct phases. The [[Geology of the North Sea|North Sea rift]] shows evidence of several separate rift phases from the [[Permian]] through to the Earliest [[Cretaceous]],<ref name="Rodmar">{{cite book|last=Ravnås|first=R. |author2=Nøttvedt A. |author3=Steel R.J.  |author4=Windelstad J.|publisher=[[Geological Society]]|location=London|year=2000|series=Special Publications|volume=167|title=Dynamics of the Norwegian Margin|pages=133–177|chapter=Syn-rift sedimentary architectures in the Northern North Sea|isbn=9781862390560|chapter-url=http://sp.lyellcollection.org/content/167/1/133.abstract|access-date=28 October 2012}}</ref> a period of over 100 million years.

===Rifting to break-up===
Rifting may lead to continental breakup and formation of oceanic basins. Successful rifting leads to seafloor spreading along a mid-oceanic ridge and a set of conjugate margins separated by an oceanic basin.<ref>{{cite journal|author1=Ziegler P.A. |author2=Cloetingh S.|title=Dynamic processes controlling evolution of rifted basins |journal=Earth-Science Reviews |date=January 2004 |volume=64 |issue=1–2 |pages=1–50 |doi=10.1016/S0012-8252(03)00041-2|bibcode=2004ESRv...64....1Z }}</ref> Rifting may be active, and controlled by [[mantle convection]]. It may also be passive, and driven by far-field tectonic forces that stretch the lithosphere. Margin architecture develops due to spatial and temporal relationships between extensional deformation phases. Margin segmentation eventually leads to the formation of rift domains with variations of the [[Mohorovičić discontinuity|Moho]] topography, including proximal domain with fault-rotated crustal blocks, necking zone with thinning of crustal [[Basement (geology)|basement]], distal domain with deep sag basins, ocean-continent transition and oceanic domain.<ref name="Marine and Petroleum Geology">{{cite journal|author1=Péron-Pinvidic G.|author2=Manatschal G.|author3=Osmundsen P.T.|title=Structural comparison of archetypal Atlantic rifted margins: a review of observations and concepts|journal=Marine and Petroleum Geology|date=May 2013|volume=43 |pages=21–47 |doi=10.1016/j.marpetgeo.2013.02.002|bibcode=2013MarPG..43...21P }}</ref>

Deformation and magmatism interact during rift evolution. Magma-rich and magma-poor rifted margins may be formed.<ref name="Marine and Petroleum Geology"/> Magma-rich margins include major volcanic features. Globally, volcanic margins represent the majority of passive continental margins.<ref>{{cite book|author1=Reston T.J.|author2=Manatschal G.|title=Building blocks of later collision|editor=Brown D. & Ryan P.D.|publisher=Frontiers in Earth Sciences|year=2011|chapter=Arc-Continent Collision}}</ref> Magma-starved rifted margins are affected by large-scale faulting and crustal hyperextension.<ref>{{cite journal|author1=Péron-Pinvidic G.|author2=Manatschal G.|title=The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view|journal=International Journal of Earth Sciences|year=2009|volume=98|issue=7 |page=1581 |doi=10.1007/s00531-008-0337-9 |bibcode=2009IJEaS..98.1581P |s2cid=129442856 }}</ref> As a consequence, upper mantle peridotites and gabbros are commonly exposed and serpentinized along extensional detachments at the seafloor.