Back-arc deformation is a product of subduction at convergent plate tectonic boundaries. It initiates and evolves behind the volcanic arc on the overriding plate of a subduction zone.[2] The stresses responsible for the deformation in this region of a subduction zone result from a combination of processes. The absolute motion of the upper plate as it moves towards or away from the trench strongly contributes to deformation in the back-arc region.[2] Since the downgoing slab is partly anchored in the viscous layers of the mantle, and therefore its lateral movement is significantly slower than the surface plate, then any motion of the overriding plate will cause extensional or compressional stress in the back-arc region depending on the direction of motion.[2] In addition, mantle convection in the upper mantle wedge caused by the downward movement of the subducted slab causes stress in the upper plate and the high heat flow that characterizes back-arcs.[3] The pulling effect of the slab as it goes down into the mantle causes a rollback motion of the trench, which also applies stress on the back-arc region of the upper plate.[2] However, this last process has less of an impact on deformation compared to upper plate motion.[2]
Back-arcs can form on either oceanic crust or continental crust. In the case of oceanic crust, most back-arc regions are subjected to tensional stresses and thus develop a spreading center where new oceanic crust is formed.[4] The composition of this new crust is similar to mid-ocean ridgebasalt (MORB), although it contains higher amounts of water.[4]
Back-arc extension vs. compressionedit
The back-arc deformation may be either extensional or compressional. The overriding plate will shorten when its motion is directed towards the trench, resulting in a compression of the back-arc region.[5] This type of deformation is associated with a shallow dipping subducted slab.[5] Inversely, an overriding plate moving away from the trench will result in extension, and a back-arc basin will form.[5] This extensional deformation is associated with a steeply dipping slab.[5]
The extreme cases of these two types of back-arc deformation can be found in Chile and at the Marianas arc. The shallow dipping slab subducting beneath Chile at an angle of about 10–15° causes a compressional stress on the back-arc region behind the Andes.[6] On the other extreme, the slab going down into the mantle at the Marianas subduction zone is so steep it is nearly vertical.[6] This is the perfect example of an oceanic back-arc basin experiencing extensional forces. The Oriente in Ecuador (the eastern part of the country covered by rainforest) is also a good example of an extensional back-arc basin, this time in a continental setting. The continental crust in this area east of the Andes has been stretched out and covered by layers of sediments.
^ abcdeHeuret, A., Lallemand, S. (March 2005), "Plate motions, slab dynamics and back-arc deformation", Physics of the Earth and Planetary Interiors, 149 (1–2): 31–51, Bibcode:2005PEPI..149...31H, doi:10.1016/j.pepi.2004.08.022{{citation}}: CS1 maint: multiple names: authors list (link)
^Uyeda, S. (January 1982), "Subduction zones: An introduction to comparative subductology", Tectonophysics, 81 (3–4): 133–159, Bibcode:1982Tectp..81..133U, doi:10.1016/0040-1951(82)90126-3
^ abTaylor, B., Martinez, F. (May 2003), "Back-arc basin basalt systematics", Earth and Planetary Science Letters, 210 (3–4): 481–497, Bibcode:2003E&PSL.210..481T, CiteSeerX10.1.1.486.4485, doi:10.1016/S0012-821X(03)00167-5{{citation}}: CS1 maint: multiple names: authors list (link)
^ abcdHeuret, A.; Funiciello, F.; Faccenna, C.; Lallemand, S. (April 2007), "Plate kinematics, slab shape and back-arc stress: A comparison between laboratory models and current subduction zones", Earth and Planetary Science Letters, 256 (3–4): 473–483, Bibcode:2007E&PSL.256..473H, doi:10.1016/j.epsl.2007.02.004
^ abUyeda, S.; Kanamori, H. (March 1979), "Back-arc opening and the mode of subduction" (PDF), Journal of Geophysical Research: Solid Earth, 84 (B3): 1049–1061, Bibcode:1979JGR....84.1049U, doi:10.1029/JB084iB03p01049
January 04, 2024
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The back arc region is the area behind a volcanic arc 1 In island volcanic arcs it consists of back arc basins of oceanic crust with abyssal depths which may be separated by remnant arcs similar to island arcs 1 In continental arcs the back arc region is part of continental platform either dry land subaerial or forming shallow marine basins 1 A back arc above a subduction zone Contents 1 Formation 2 Back arc extension vs compression 3 See also 4 ReferencesFormation editBack arc deformation is a product of subduction at convergent plate tectonic boundaries It initiates and evolves behind the volcanic arc on the overriding plate of a subduction zone 2 The stresses responsible for the deformation in this region of a subduction zone result from a combination of processes The absolute motion of the upper plate as it moves towards or away from the trench strongly contributes to deformation in the back arc region 2 Since the downgoing slab is partly anchored in the viscous layers of the mantle and therefore its lateral movement is significantly slower than the surface plate then any motion of the overriding plate will cause extensional or compressional stress in the back arc region depending on the direction of motion 2 In addition mantle convection in the upper mantle wedge caused by the downward movement of the subducted slab causes stress in the upper plate and the high heat flow that characterizes back arcs 3 The pulling effect of the slab as it goes down into the mantle causes a rollback motion of the trench which also applies stress on the back arc region of the upper plate 2 However this last process has less of an impact on deformation compared to upper plate motion 2 Back arcs can form on either oceanic crust or continental crust In the case of oceanic crust most back arc regions are subjected to tensional stresses and thus develop a spreading center where new oceanic crust is formed 4 The composition of this new crust is similar to mid ocean ridge basalt MORB although it contains higher amounts of water 4 Back arc extension vs compression editThe back arc deformation may be either extensional or compressional The overriding plate will shorten when its motion is directed towards the trench resulting in a compression of the back arc region 5 This type of deformation is associated with a shallow dipping subducted slab 5 Inversely an overriding plate moving away from the trench will result in extension and a back arc basin will form 5 This extensional deformation is associated with a steeply dipping slab 5 The extreme cases of these two types of back arc deformation can be found in Chile and at the Marianas arc The shallow dipping slab subducting beneath Chile at an angle of about 10 15 causes a compressional stress on the back arc region behind the Andes 6 On the other extreme the slab going down into the mantle at the Marianas subduction zone is so steep it is nearly vertical 6 This is the perfect example of an oceanic back arc basin experiencing extensional forces The Oriente in Ecuador the eastern part of the country covered by rainforest is also a good example of an extensional back arc basin this time in a continental setting The continental crust in this area east of the Andes has been stretched out and covered by layers of sediments See also editBack arc basin Forearc basin Foreland basinReferences edit a b c Moores Eldridge M Twiss Robert J 1995 Tectonics W H Freeman and Company p 157 ISBN 978 0 7167 2437 7 a b c d e Heuret A Lallemand S March 2005 Plate motions slab dynamics and back arc deformation Physics of the Earth and Planetary Interiors 149 1 2 31 51 Bibcode 2005PEPI 149 31H doi 10 1016 j pepi 2004 08 022 a href Template Citation html title Template Citation citation a CS1 maint multiple names authors list link Uyeda S January 1982 Subduction zones An introduction to comparative subductology Tectonophysics 81 3 4 133 159 Bibcode 1982Tectp 81 133U doi 10 1016 0040 1951 82 90126 3 a b Taylor B Martinez F May 2003 Back arc basin basalt systematics Earth and Planetary Science Letters 210 3 4 481 497 Bibcode 2003E amp PSL 210 481T CiteSeerX 10 1 1 486 4485 doi 10 1016 S0012 821X 03 00167 5 a href Template Citation html title Template Citation citation a CS1 maint multiple names authors list link a b c d Heuret A Funiciello F Faccenna C Lallemand S April 2007 Plate kinematics slab shape and back arc stress A comparison between laboratory models and current subduction zones Earth and Planetary Science Letters 256 3 4 473 483 Bibcode 2007E amp PSL 256 473H doi 10 1016 j epsl 2007 02 004 a b Uyeda S Kanamori H March 1979 Back arc opening and the mode of subduction PDF Journal of Geophysical Research Solid Earth 84 B3 1049 1061 Bibcode 1979JGR 84 1049U doi 10 1029 JB084iB03p01049 Retrieved from https en wikipedia org w index php title Back arc region amp oldid 1051022160, wikipedia, wiki, book, books, library,
