In geology, a forebulge is a flexural bulge in front as a result of a load on the lithosphere, often caused by tectonic interactions and glaciations. An example of forebulge can be seen in the Himalayan foreland basin, a result of the Indian-Eurasian (continent-continent) plate collision, in which the Indian plate subducted and the Eurasian plate created a large load on the lithosphere, leading to the Himalayas and the Ganges foreland basin.[1]
Example of forebulge via lithospheric flexure in the formation of a Foreland basin.
Forebulge is most commonly found with continent-continent convergent collisions, in which the formation of mountain ranges as the plates collide places a large load on the lithosphere below.[2] The lithosphere flexes in response to the load on the mantle, causing depression and subsidence (fordeep) followed by the forebulging in the front. The forebulge area is lifted by a height that is 4% of the depression height caused by the load.[3] It takes roughly 10,000 to 20,000 years for forebulge to fully develop when the mantle flexure to reach isostatic equilibrium, a process that is controlled by mantle viscosity.[3]
Tectonic
View of the Persian Gulf with the Zagros Mountains whose load on the lithosphere helped to form the Gulf.
Forebulge can be seen during the formation of a mountain range, which creates a large load and crustal thickening that leads to lithospheric flexure. Part of the land sinks under the load (Foredeep) while part of the outer land forebulges, leading to the creation of these foreland basins. Forebulge associated with the formation of these basins is most commonly a result of convergent collision.[2] Foreland basins can occur in convergent subduction, but this is rare.[2] These basins are linked to fold-thrust belts, which are divided into three main types: collisional (peripheral), retroarc, and retreating collisional subduction.[4] Collisional and retroarc thrust belts form in collision convergent plates whereas retreating collisional forms when the subduction rate exceeds the convergence rate of the collision.
The Ganges Basin seen next to the Himalayas whose load on the lithosphere helped to create the basin.
The Persian Gulf foreland basin and forebulge was created as a result of the collision of the Arabian and Eurasian plates around 13 million years ago.[5] The Zagros mountains that formed, as a result, created a load on the lithosphere that led to the creation of the modern-day Persian Gulf.[5]
Collisions between tectonic plates and island arcs lead to loading and flexure of the lithosphere. The flexure produces a significant forebulge, which divides a forearc basin and a back arc basin.
Forebulge can be seen here in the Mariana Trench where the Pacific plate is subducted.
The Ganges basin and Himalayan Basin roughly 50 to 70 million years ago as a result of the load of the Himalayan mountains after the collision of the Eurasian and Indian plates.[6]
The Andean foreland basins were created as a result of the lithospheric flexure due to the load of the Andean mountain (fold-thrust belt) and resulting foredeep, forebulge, and backbulge.[4]
Forebulge can also be observed in the flexural plate of the Mariana arc, which was formed when the Pacific plate subducted under the Philippine plate.[7]
Glacial
Chesapeake Bay is one area currently experiencing a rise in sea level due to post-glacial rebound.
One cause for forebulge formation is the loading of the continental lithosphere by ice sheets during continental glaciations. Due to recession of the ice sheets, the formerly-glaciated areas are currently rising in a phenomenon known as post-glacial rebound. Forebulge collapse due to post-glacial rebound is greatest along the east coast of the United States, which lay just under the North American ice sheet.[8] As a result of forebulge collapse due to post-glacial rebound, most of the coast of the Eastern US has slowly been sinking; it is estimated that the area around the Chesapeake Bay will sink a foot (0.305 m) over the next hundred years.[9] Due to the coupling of the mantle with the plates, data from post-glacial rebound are used as a direct probe of the viscosity of the upper mantle.[10] As an ice sheet collapses, the land that was previously depressed rises in isostatic recovery followed by subsidence of forebulge, causing sea levels to rise.[8] Forebulge collapse is also the reason why the Netherlands and parts of southern England are still slowly sinking.[11] One estimate is that the center of the North Sea rose by about 170 m (558 ft) during the Ice Age because of forebulging.[12]
References
^Singh, B.P. (2003). "Evidence of growth fault and forebulge in the Late Paleocene (~57.9–54.7 Ma), western Himalayan foreland basin, India". Earth and Planetary Science Letters. 216 (4): 717–724. doi:10.1016/S0012-821X(03)00540-5.
^ abcJohnson, Chris (2017). An Introduction to Geology. Matthew D. Affolter, Paul Inkenbrandt, Cam Mosher, XanEdu. Ann Arbor, MI. ISBN978-1-7114-0577-3. OCLC 1199367048.
^ abThe dictionary of physical geography. David S. G. Thomas (Fourth ed.). Hoboken, NJ. 2016. ISBN978-1-118-78231-6. OCLC 925426734.{{cite book}}: CS1 maint: others (link)
^ abDeCelles, Peter G. (2011), "Foreland Basin Systems Revisited: Variations in Response to Tectonic Settings", Tectonics of Sedimentary Basins, John Wiley & Sons, Ltd, pp. 405–426, doi:10.1002/9781444347166.ch20, ISBN978-1-4443-4716-6, retrieved 2021-11-05
^ abDewey, J.F.; Hempton, M.R.; Kidd, W.S.F.; Saroglu, F.; Şengör, A.M.C. (1986). "Shortening of continental lithosphere: the neotectonics of Eastern Anatolia — a young collision zone". Geological Society, London, Special Publications. 19 (1): 1–36. doi:10.1144/GSL.SP.1986.019.01.01. ISSN 0305-8719. S2CID 128626856.
^Aitchison, Jonathan C.; Ali, Jason R.; Davis, Aileen M. (2007). "When and where did India and Asia collide?". Journal of Geophysical Research: Solid Earth. 112 (B5). doi:10.1029/2006JB004706. hdl:10722/72794. ISSN 2156-2202.
^Ziegler, P. A.; Bertotti, G.; Cloetingh, S. (2002). "Dynamic processes controlling foreland development – the role of mechanical (de)coupling of orogenic wedges and forelands". Stephan Mueller Special Publication Series. 1: 17–56. doi:10.5194/smsps-1-17-2002. ISSN 1868-4564.
^ abPeltier, W. R. (1998). "Postglacial variations in the level of the sea: Implications for climate dynamics and solid-Earth geophysics". Reviews of Geophysics. 36 (4): 603–689. doi:10.1029/98RG02638. ISSN 1944-9208.
^DeJong, Benjamin D.; Bierman, Paul R.; Newell, Wayne L.; Rittenour, Tammy M.; Mahan, Shannon A.; Balco, Greg; Rood, Dylan H. (2015-08-01). "Pleistocene relative sea levels in the Chesapeake Bay region and their implications for the next century". GSA Today: 4–10. doi:10.1130/GSATG223A.1. S2CID 140118725.
^Perry, H. K. C.; Forte, A. M.; Eaton, D. W. S. (2003). "Upper-mantle thermochemical structure below North America from seismic-geodynamic flow models". Geophysical Journal International. 154 (2): 279–299. doi:10.1046/j.1365-246x.2003.01961.x. ISSN 0956-540X.
^Devoy, Robert J. N. (1995). "Deglaciation, Earth crustal behaviour and sea-level changes in the determination of insularity: a perspective from Ireland". Geological Society, London, Special Publications. 96 (1): 181–208. doi:10.1144/gsl.sp.1995.096.01.14. ISSN 0305-8719. S2CID 130211641.
July 24, 2023
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In geology a forebulge is a flexural bulge in front as a result of a load on the lithosphere often caused by tectonic interactions and glaciations An example of forebulge can be seen in the Himalayan foreland basin a result of the Indian Eurasian continent continent plate collision in which the Indian plate subducted and the Eurasian plate created a large load on the lithosphere leading to the Himalayas and the Ganges foreland basin 1 Example of forebulge via lithospheric flexure in the formation of a Foreland basin Contents 1 Background 2 Tectonic 3 Glacial 4 ReferencesBackground EditForebulge is most commonly found with continent continent convergent collisions in which the formation of mountain ranges as the plates collide places a large load on the lithosphere below 2 The lithosphere flexes in response to the load on the mantle causing depression and subsidence fordeep followed by the forebulging in the front The forebulge area is lifted by a height that is 4 of the depression height caused by the load 3 It takes roughly 10 000 to 20 000 years for forebulge to fully develop when the mantle flexure to reach isostatic equilibrium a process that is controlled by mantle viscosity 3 Tectonic Edit View of the Persian Gulf with the Zagros Mountains whose load on the lithosphere helped to form the Gulf Forebulge can be seen during the formation of a mountain range which creates a large load and crustal thickening that leads to lithospheric flexure Part of the land sinks under the load Foredeep while part of the outer land forebulges leading to the creation of these foreland basins Forebulge associated with the formation of these basins is most commonly a result of convergent collision 2 Foreland basins can occur in convergent subduction but this is rare 2 These basins are linked to fold thrust belts which are divided into three main types collisional peripheral retroarc and retreating collisional subduction 4 Collisional and retroarc thrust belts form in collision convergent plates whereas retreating collisional forms when the subduction rate exceeds the convergence rate of the collision See also Persian Gulf The Ganges Basin seen next to the Himalayas whose load on the lithosphere helped to create the basin The Persian Gulf foreland basin and forebulge was created as a result of the collision of the Arabian and Eurasian plates around 13 million years ago 5 The Zagros mountains that formed as a result created a load on the lithosphere that led to the creation of the modern day Persian Gulf 5 See also Asuncion archCollisions between tectonic plates and island arcs lead to loading and flexure of the lithosphere The flexure produces a significant forebulge which divides a forearc basin and a back arc basin See also Ganges Basin Forebulge can be seen here in the Mariana Trench where the Pacific plate is subducted The Ganges basin and Himalayan Basin roughly 50 to 70 million years ago as a result of the load of the Himalayan mountains after the collision of the Eurasian and Indian plates 6 See also Andean foreland basins The Andean foreland basins were created as a result of the lithospheric flexure due to the load of the Andean mountain fold thrust belt and resulting foredeep forebulge and backbulge 4 See also Mariana Trench Forebulge can also be observed in the flexural plate of the Mariana arc which was formed when the Pacific plate subducted under the Philippine plate 7 Glacial Edit Chesapeake Bay is one area currently experiencing a rise in sea level due to post glacial rebound One cause for forebulge formation is the loading of the continental lithosphere by ice sheets during continental glaciations Due to recession of the ice sheets the formerly glaciated areas are currently rising in a phenomenon known as post glacial rebound Forebulge collapse due to post glacial rebound is greatest along the east coast of the United States which lay just under the North American ice sheet 8 As a result of forebulge collapse due to post glacial rebound most of the coast of the Eastern US has slowly been sinking it is estimated that the area around the Chesapeake Bay will sink a foot 0 305 m over the next hundred years 9 Due to the coupling of the mantle with the plates data from post glacial rebound are used as a direct probe of the viscosity of the upper mantle 10 As an ice sheet collapses the land that was previously depressed rises in isostatic recovery followed by subsidence of forebulge causing sea levels to rise 8 Forebulge collapse is also the reason why the Netherlands and parts of southern England are still slowly sinking 11 One estimate is that the center of the North Sea rose by about 170 m 558 ft during the Ice Age because of forebulging 12 References Edit Singh B P 2003 Evidence of growth fault and forebulge in the Late Paleocene 57 9 54 7 Ma western Himalayan foreland basin India Earth and Planetary Science Letters 216 4 717 724 doi 10 1016 S0012 821X 03 00540 5 a b c Johnson Chris 2017 An Introduction to Geology Matthew D Affolter Paul Inkenbrandt Cam Mosher XanEdu Ann Arbor MI ISBN 978 1 7114 0577 3 OCLC 1199367048 a b The dictionary of physical geography David S G Thomas Fourth ed Hoboken NJ 2016 ISBN 978 1 118 78231 6 OCLC 925426734 a href Template Cite book html title Template Cite book cite book a CS1 maint others link a b DeCelles Peter G 2011 Foreland Basin Systems Revisited Variations in Response to Tectonic Settings Tectonics of Sedimentary Basins John Wiley amp Sons Ltd pp 405 426 doi 10 1002 9781444347166 ch20 ISBN 978 1 4443 4716 6 retrieved 2021 11 05 a b Dewey J F Hempton M R Kidd W S F Saroglu F Sengor A M C 1986 Shortening of continental lithosphere the neotectonics of Eastern Anatolia a young collision zone Geological Society London Special Publications 19 1 1 36 doi 10 1144 GSL SP 1986 019 01 01 ISSN 0305 8719 S2CID 128626856 Aitchison Jonathan C Ali Jason R Davis Aileen M 2007 When and where did India and Asia collide Journal of Geophysical Research Solid Earth 112 B5 doi 10 1029 2006JB004706 hdl 10722 72794 ISSN 2156 2202 Ziegler P A Bertotti G Cloetingh S 2002 Dynamic processes controlling foreland development the role of mechanical de coupling of orogenic wedges and forelands Stephan Mueller Special Publication Series 1 17 56 doi 10 5194 smsps 1 17 2002 ISSN 1868 4564 a b Peltier W R 1998 Postglacial variations in the level of the sea Implications for climate dynamics and solid Earth geophysics Reviews of Geophysics 36 4 603 689 doi 10 1029 98RG02638 ISSN 1944 9208 DeJong Benjamin D Bierman Paul R Newell Wayne L Rittenour Tammy M Mahan Shannon A Balco Greg Rood Dylan H 2015 08 01 Pleistocene relative sea levels in the Chesapeake Bay region and their implications for the next century GSA Today 4 10 doi 10 1130 GSATG223A 1 S2CID 140118725 Perry H K C Forte A M Eaton D W S 2003 Upper mantle thermochemical structure below North America from seismic geodynamic flow models Geophysical Journal International 154 2 279 299 doi 10 1046 j 1365 246x 2003 01961 x ISSN 0956 540X p54 in Doggerland a Speculative Survey by B J Coles Proceedings of the Prehistoric Society 64 1998 pp 45 81 Devoy Robert J N 1995 Deglaciation Earth crustal behaviour and sea level changes in the determination of insularity a perspective from Ireland Geological Society London Special Publications 96 1 181 208 doi 10 1144 gsl sp 1995 096 01 14 ISSN 0305 8719 S2CID 130211641 Retrieved from https en wikipedia org w index php title Forebulge amp oldid 1140640201, wikipedia, wiki, book, books, library,
