Editing Rift (section)

{{Short description|Geological linear zone where the lithosphere is being pulled apart}}
{{Redirect|Chasm}}
{{About|the geological concept}}
{{Distinguish|rift zone}}

[[File:Rift segmentation.png|thumb|240px|Block view of a rift formed of three segments, showing the location of the accommodation zones between them at changes in fault location or polarity (dip direction)]]

[[File:GulfofSuezRift.png|200px|thumb|[[Gulf of Suez Rift]] showing main [[extensional fault]]s]]

In [[geology]], a '''rift''' is a linear zone where the [[lithosphere]] is being pulled apart<ref>[http://ethiopianrift.igg.cnr.it/rift%20valley%20significance.htm Rift valley: definition and geologic significance], Giacomo Corti, The Ethiopian Rift Valley</ref><ref>[http://www.mantleplumes.org/VM_DecompressMelt.html Decompressional Melting During Extension of Continental Lithosphere], Jolante van Wijk, MantlePlumes.org</ref> and is an example of [[extensional tectonics]].<ref>[http://www.le.ac.uk/geology/art/gl209/lecture4/lecture4.html Plate Tectonics: Lecture 2], Geology Department at University of Leicester</ref> Typical rift features are a central linear [[Fault (geology)|downfaulted]] depression, called a [[graben]], or more commonly a [[half-graben]] with normal faulting and rift-flank uplifts mainly on one side.<ref name="Leeder_&_Gawthorpe_1987">{{Cite book |last1=Leeder |first1=M.R. |title=Continental Extensional Tectonics |last2=Gawthorpe |first2=R.L. |isbn=9780632016051 |editor-last1=Coward |editor-first1=M.P. |series=Geological Society, Special Publications |volume=28 |date=1987 |pages=139–152 |chapter=Sedimentary models for extensional tilt-block/half-graben basins  |editor-last2=Dewey |editor-first2=J.F. |editor-last3=Hancock |editor-first3=P.L. |chapter-url=https://pages.uoregon.edu/rdorsey/BasinAnalysis/BasinPapers/Leeder_&_Gawthorpe_1987.pdf}}</ref> Where rifts remain above sea level they form a [[rift valley]], which may be filled by water forming a [[rift lake]]. The axis of the rift area may contain [[volcanic rocks]], and active [[volcanism]] is a part of many, but not all, active rift systems.

Major rifts occur along the central axis of most [[mid-ocean ridge]]s, where new [[oceanic crust]] and lithosphere is created along a [[divergent boundary]] between two [[tectonic plate]]s.

''Failed rifts'' are the result of continental rifting that failed to continue to the point of break-up.  Typically the transition from rifting to spreading develops at a [[triple junction]] where three converging rifts meet over a [[Hotspot (geology)|hotspot]].  Two of these evolve to the point of seafloor spreading, while the third ultimately fails, becoming an [[aulacogen]].