Great Rift Valley: Difference between revisions
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{{short description|Continuous geographic trench from Asia to Southeast Africa}} | {{short description|Continuous geographic trench from Asia to Southeast Africa}} | ||
{{other uses|Great Rift Valley (disambiguation)}} | {{other uses|Great Rift Valley (disambiguation)}} | ||
{{ | The '''Great Rift Valley''' (GRV) is a series of contiguous geographic [[depression (geology)|depressions]], approximately {{convert|6,500|km|mi|-2}} in total length, which, in its original definition, runs from "the plains of northern [[Syria]]" in the north,{{efn|[[Ottoman Syria]] at the end of the 19th-century included what is now the southern Turkish [[Hatay Province]].<ref name= Bat>{{cite journal |author= Benda, Petr |display-authors= et al. |title= Bats (Mammalia: Chiroptera) of the Eastern Mediterranean. Part 4. Bat fauna of Syria: distribution, systematics, ecology |date= January 2006 |journal= Acta Soc. Zool. Bohem. |issue= 70 |pages= 1–329 (9) |issn= 1211-376X |via= ResearchGate |url=https://www.researchgate.net/publication/235993996 |access-date= 9 September 2024}}</ref>}} through the [[Red Sea]], to [[Mozambique]] in the south.<ref name="rift"/><ref name="Drysdale_2025"/> The term remains in use in the fields of geography, zoology, ecology, paleontology and other disciplines, but it is now rarely used in [[geology]] where the term "'''Afro-Arabian Rift System'''" is preferred, which describes the series of geological structures that have given rise to the geographical feature.<ref>{{Cite journal |last=Girdler |first=R. W. |date=1991-10-30 |title=The Afro-Arabian rift system—an overview |url=https://linkinghub.elsevier.com/retrieve/pii/004019519190038T |journal=Tectonophysics |volume=197 |issue=2 |pages=139–153 |doi=10.1016/0040-1951(91)90038-T |bibcode=1991Tectp.197..139G |issn=0040-1951|url-access=subscription }}</ref> Great Rift Valley is also often used to refer to valleys, such as the [[Kenyan Rift Valley]], within the [[East African Rift]] system. | ||
[[ | |||
The | The term was introduced by British geologist [[John Walter Gregory]] in 1896, following on from the work of Austrian geologist [[Eduard Suess]], who first proposed the existence of a linked set of features extending from Syria to Mozambique.<ref name="rift">{{cite book | ||
| last = Gregory| first = John Walter| title = The Great Rift Valley: Being the Narrative of a Journey to Mount Kenya and Lake Baringo with Some Account of the Geology, Natural History, Anthropology and Future Prospect of British East Africa| url = https://books.google.com/books?id=JRtkpqANIB4C| year = 1896| publisher = Routledge| isbn = 0-7146-1812-8| page = 422 pages}}</ref> | |||
[[File:Tectonic African Arabian Rift System.jpg|thumb|Tectonic map of the Afro-Arabian rift system, showing the [[Afar triple junction]] between the [[Red Sea Rift|Red Sea rift]], the [[Aden Ridge|Gulf of Aden rift]], and the [[East African Rift|East African rift system]] with the velocities of each plate relative to the [[African plate|Nubian plate]]]] | |||
==Geology== | |||
The Afro-Arabian Rift (AAR) is a series of major geological structures that have created the observed topographic features that make up the Great Rift Valley. The northern part of the AAR is formed by the Dead Sea Transform (DST) (also known as the Dead Sea or Levantine rift), the transform type boundary between the [[Arabian plate]] and the [[Nubian plate|African (Nubian) plate]]. It extends southwards from the [[Marash triple junction]] in southeastern Turkey, where it meets the [[East Anatolian Fault]], to the mouth of the [[Gulf of Aqaba]] where it joins with the [[Red Sea Rift]]. The dominant displacement along the DST is left-lateral strike-slip, with [[transtension]] along the southern part, [[transpression]] in the central section in Lebanon and local transtension within overall [[transpression]] in the northern part. Transtension has produced a series of [[pull-apart basin]]s, the [[Dead Sea]], [[Sea of Galilee]], [[Hula basin]] and the [[Ghab basin]]. The transpression has led to the uplift of the [[Anti-Lebanon mountains]] and [[Mount Lebanon]] either side of the [[Beqaa valley]].<ref name="Garfunkel_2015">{{Cite book |last=Garfunkel |first=Z. |title=Dead Sea Transform Fault System: Reviews |publisher=Springer |year=2014 |isbn=978-94-017-8871-7 |editor-last=Garfunkel |editor-first=Z. |series=Modern Approaches in Solid Earth Sciences |volume=6 |pages=109–150 |chapter=Lateral Motion and Deformation Along the Dead Sea Transform |doi=10.1007/978-94-017-8872-4_5 |editor-last2=Ben-Avraham |editor-first2=Z. |editor-last3=Kagan |editor-first3=E.}}</ref> | |||
The Red Sea Rift is a [[mid-ocean ridge]] that accommodates the increasing separation between the Nubian and Arabian plates. The southeastern end of the Red Sea Rift links to both the western end of the [[Aden Ridge]] and the northern end of the [[East African Rift]] system (EARS), at the [[Afar triple junction]].<ref name="Augustin_etal_2016"/> | |||
The | Sited next to the triple junction, the [[Afar triangle]] is an area of thinned and heavily intruded [[continental crust]]. The EARS continues to the south of the Afar triangle as the [[Main Ethiopian Rift]] passing through the strongly uplifted [[Ethiopian Highlands]]. Further south, the EARS splits into two main parts, the western [[Albertine Rift]] and the eastern [[Gregory Rift]] that pass to either side of the [[Victoria microplate]], before joining again to the north of [[Lake Malawi]]. The EARS continues southwards to the coast along Lake Malawi and the [[Urema Graben]]. The Main Ethiopian and Gregory rifts are associated with major off-axis volcanism and many of the active basins within the rift are at least part filled with volcanic products. The Albertine Rift and its southward continuation into Mozambique are dominated by the formation of [[half-graben]] basins with major subsidence and flank uplifts.<ref name="Macgregor_2015">{{Cite journal |last=Macgregor |first=D. |date=2015 |title=History of the development of the East African Rift System: A series of interpreted maps through time |journal=Journal of African Earth Sciences |volume=101 |pages=232–252 |doi=10.1016/j.jafrearsci.2014.09.016 |bibcode=2015JAfES.101..232M }}</ref> | ||
== | ==Geography== | ||
[[File: | [[File:Great Rift Valley N Asian section.png|thumb|Topographic map pf the northern Asian section]] | ||
[[File: | [[File:Great Rift Valley S Asian section.png|thumb|Topographic map of the southern Asian section]] | ||
===Asian section=== | |||
The most northerly part of the GRV is the [[Ghab Plain]], developed above the [[Ghab basin]], along the valley of the [[Orontes River]] in northern Syria. The next section to the south of the Ghab plain is the Beqaa valley, which contains two rivers, the Orontes river, which drains northwards and the [[Litani river|Litani]], which drains southwestwards.<ref name="Drysdale_2025"/> At the southern end of the valley, where the Litani river turns abruptly westwards, it comes within 5 km of the Hisbai river, part of the headwaters of the Jordan river. Beyond the Beqaa valley, the remaining part of the GRF in Asia is known as the [[Jordan Rift Valley]], extending down to the Red Sea. The [[Hula valley]], which lies above the Hula basin, is a nearly completely flat valley at about 70 m elevation, confined between the drainage basin of the many tributaries of the Jordan river to the north, the Golan heights to the east, the Naftali mountains to the west, the drainage basin of further tributaries to the southwest and the Korazim plateau to the south. The Jordan river passes south through the plateau in a gorge before reaching the Sea of Galilee (Lake Kinneret).<ref name="Goshen_2023">{{Cite book |last=Goshen |first=M. |title=Agriculture, Recreation, Water Quality and Nature Protection in the Hula Valley, Israel |date=2023 |publisher=Springer-Nature |isbn=9783031234125|issn=2194-315X |pages=1}}</ref> The Sea of Galilee is the most northerly part of the Dead Sea depression, the base of which is all below sea level. The full length of the depression was filled during the Pleistocene by [[Lake Lisan]], although the lake surface was still about 200 m below sea level at its highest. The area of the depression below sea level is approximately 5,000 km<sup>2</sup>. The deepest part of the depression is occupied by the Dead Sea, while another local deep is the location of the Sea of Galilee. Almost the entire depression is flanked by steep sides.<ref name="Hall_1996">{{Cite journal |last=Hall |first=J.K. |date=1996 |title=Digital topography and bathymetry of the area of the Dead Sea Depression |journal=Tectonophysics |volume=266 |issue=1–4 |pages=177–185 |doi=10.1016/S0040-1951(96)00189-8 |bibcode=1996Tectp.266..177H }}</ref> The section between the Dead Sea depression and the Gulf of Aqaba is known as [[Arabah]], the northern part of which is also known as the Arava valley. It rises steeply from the Dead Sea before rising much more gradually up to the watershed at an elevation of about 200m. before descending gradually to the Gulf of Aqaba. The southern part of this section is well-defined and narrower than the northern part, being generally 10 km or less wide, compared to 30 km further north, an area that lacks a clear western edge.<ref name="Bienkowski_2006">{{Cite book |last=Bienkowski |first=P. |title=Crossing the Rift: Resources, Routes, Settlement Patterns and Interaction in the Wadi Arabah |publisher=Council for British Research in the Levant and Oxbow |year=2006 |isbn=9781842172094 |editor-last=Bienkowski |editor-first=P. |series=Levant supplementary series |volume=3 |chapter=The Wadi Arabah: meanings in a contested landscape |editor-last2=Galor |editor-first2=K.}}</ref><ref name="Drysdale_2025">{{Cite book |last=Drysdale |first=A. |title=The Middle East and North Africa: A Contemporary Geography |date=2025 |publisher=Bloomsbury Publishing |isbn=9798881859077 |pages=21}}</ref> The Gulf of Aqaba is a relatively narrow gulf that extends 160 km from the southern end of the Arabah valley to the [[Straits of Tiran]], its junction with the Red Sea. It contains a set of deeps, the Elat, Aragonese, Dakar and Tiran, with the greatest depth being reached in the Aragonese deep of 1850 m. The gulf narrows and shallows markedly in the Strait of Tiran, being only 13 km wide and about 250 m deep. Beyond the strait, within the Red Sea, the ~1,400 m deep Hume Deep is also developed.<ref name="Ribot_etal_2021">{{Cite journal |last1=Ribot |first1=M. |last2=Klinger |first2=Y. |last3=Jónsson |first3=S. |last4=Avsar |first4=U. |last5=Pons-Branchu |first5=E. |last6=Matrau |first6=R. |last7=Mallon |first7=F.R. |date=2021 |title=Active Faults' Geometry in the Gulf of Aqaba, Southern Dead Sea Fault, Illuminated by Multibeam Bathymetric Data |journal=Tectonics |volume=40 |issue=4 |article-number=e2020TC006443 |doi=10.1029/2020TC006443 |bibcode=2021Tecto..4006443R }}</ref> | |||
== | ===Red Sea=== | ||
{{ | The Asian and African sections of the GRV are linked by the Red Sea. The Red Sea is characterised by broad relatively shallow flanks and a narrow (<60 km wide), deep central valley that reaches a maximum depth of 2,860 m.<ref name="Augustin_etal_2016">{{Cite journal |last1=Augustin |first1=N. |last2=van der Zwan |first2=F.M. |last3=Devey |first3=C.W. |last4=Ligi |first4=M. |last5=Kwasnitschka |first5=T. |last6=Feldens |first6=P. |last7=Bantan |first7=R.A. |last8=Basaham |first8=A.S. |date=2016 |title=Geomorphology of the central Red Sea Rift: Determining spreading processes |journal=Geomorphology |volume=274 |pages=162–179 |doi=10.1016/j.geomorph.2016.08.028 |bibcode=2016Geomo.274..162A }}</ref> | ||
===African section=== | |||
[[File:GRV Ethiopian Rift section.png|thumb|Topographic map of the Ethiopian section]] | |||
[[File:GRV Albertine Gregory Rift section.png|thumb|Topographic map of the Albertine and Gregory rifts]] | |||
[[File:Great Rift Valley southernmost section.png|thumb|Topographic map of the southernmost section of the Great RIft Valley]] | |||
The first feature south of the Red Sea that is considered to be part of the GRV is the [[Danakil Depression]], within the [[Afar Depression]], formed between the [[Ethiopian plateau]] to the west and the [[Danakil Alps]] to the east. The deepest part of the depression is well below sea level, reaching a general ~120m below in the northern part. To the south the depression becomes progressively obscured by the volcanic [[Erta Ale Range]]. The next clearly defined section of the GRV is the [[Main Ethiopian Rift]] (MER) valley, bordered by the Ethiopian and Somalian plateaus. The MER has an overall northeast–southwest trend and has been divided into three parts; the northern, central and southern sections. The northern MER extends southwards from the Afar Depression as far as [[Lake Koka]]. It is characterised by a high level of volcanic activity. The central section extends from Lake Koka to [[Lake Awasa]], while the southern section runs from there to what is known as the "broadly rifted zone". The central and southern sections contain several lakes and are less affected by volcanic activity. The level of the rift valley floor in the MER climbs continuously from the Afar Depression into the central section, where it reaches an elevation of about 1,700 m, before descending gradually into the "broadly-rifted zone".<ref name="Corti_2009">{{Cite journal |last=Corti |first=G. |date=2009 |title=Continental rift evolution: From rift initiation to incipient break-up in the Main Ethiopian Rift, East Africa |journal=Earth Science Reviews |volume=96 |issue=1–2 |pages=1–53 |doi=10.1016/j.earscirev.2009.06.005 |bibcode=2009ESRv...96....1C }}</ref> | |||
The [[ | In the "broadly rifted zone", the GRV becomes indistinct. Further south the GRV splits into two separate parts, the western or Albertine rift and the eastern or Gregory rift. The northernmost part of the eastern branch is formed by the valley of the [[Omo river]] in southern Ethiopia and [[Lake Turkana]] in Kenya.<ref name="Lepre_2014">{{Cite journal |last=Lepre |first=C.J. |date=2014 |title=Early Pleistocene lake formation and hominin origins in the Turkana–Omo rift |journal=Quaternary Science Reviews |volume=102 |pages=181–191 |doi=10.1016/j.quascirev.2014.08.012 |bibcode=2014QSRv..102..181L }}</ref> Much of the eastern branch lies in Kenya and is often referred to as the [[Kenya Rift Valley]]. The rift valley floor is punctuated by relatively small lakes and numerous volcanoes. Many of these lakes are saline and alkaline in nature, such as [[Lake Bogoria]] and [[Lake Natron]]. The eastern part of the GRV continues into Tanzania, where it spreads out in what is known as the "North Tanzanian Divergence", with rift structures extending to the southwest ([[Lake Eyasi]]), to the south ([[Lake Manyara]]) and the [[Pangani River]] basin to the southeast.<ref name="Dawson_1992">{{Cite journal |last=Dawson |first=J.B. |date=1992 |title=Neogene tectonics and volcanicity in the North Tanzania sector of the Gregory Rift Valley: contrasts with the Kenya sector |journal=Tectonophysics |volume=204 |issue=1–2 |pages=81-83, 87-92 |doi=10.1016/0040-1951(92)90271-7 |bibcode=1992Tectp.204...81D }}</ref> In addition to the smaller volcanoes along the rift axis, there are large volcanic edifices on the rift shoulders, such as [[Mount Kenya]] and [[Mount Kilimanjaro]], the highest mountains in Africa. There are national parks associated with many of the lakes and the larger volcanoes, such as the [[Lake Baringo National Park]], the [[Lake Nakuru National Park]] and the [[Mount Kenya National Park]].<ref name="Scoon_2020"/> | ||
The western branch of the GRV starts from the north with the [[Rhino Camp]] basin, before stepping to the southeast and continuing along [[Lake Albert (Africa)|Lake Albert]]. The Albert River (part of the [[White Nile]]) passes through this zone of overlap and on through the Rhino Camp basin.<ref name="Katumwehe_etal_2015">{{Cite journal |last1=Katumwehe |first1=A.B. |last2=Abdelsalam |first2=M.G. |last3=Atekwana |first3=E.A. |title=The role of pre-existing Precambrian structures in rift evolution: The Albertine and Rhino grabens, Uganda |journal=Tectonophysics |date=2015 |volume=646 |pages=117–129 |doi=10.1016/j.tecto.2015.01.022 |bibcode=2015Tectp.646..117K }}</ref> The western branch consists mainly of a series of deep lakes, Lake Albert, [[Lake Rutanzige]], [[Lake Kivu]], [[Lake Tanganyika]] and [[Lake Rukwa]]. Of these, only Rukwa is endorheic and alkaline, with the others being through-drained and freshwater. Lake Tanganyika is the second largest and second deepest freshwater lake in the world. The western branch is bordered by some of the highest mountains in Africa, including the [[Virunga Mountains]], [[Mitumba Mountains]], and [[Ruwenzori Range]]. Much of this area lies within the boundaries of national parks, such as [[Virunga National Park]] in the [[Democratic Republic of Congo]], [[Rwenzori National Park]] and [[Queen Elizabeth National Park]] in Uganda, and [[Volcanoes National Park]] in [[Rwanda]].<ref name="Scoon_2020">{{Cite journal |last=Scoon |first=R.N. |date=2020 |title=Geotourism, Iconic Landforms and Island-Style Speciation Patterns in National Parks of East Africa |journal=Geoheritage |volume=12 |issue=66 |article-number=66 |doi=10.1007/s12371-020-00486-z |bibcode=2020Geohe..12...66S |doi-access=free }}</ref> | |||
The southernmost section of the GRV includes [[Lake Malawi]], the third-deepest freshwater body in the world, which reaches {{Convert|706|m|}} in depth and separates the [[Niassa Province|Nyassa]] plateau of Northern Mozambique from Malawi. The rift extends southwards from Lake Malawi as the valley of the [[Shire River]], which flows from the lake into the [[Zambezi]] River. The rift valley continues south, beyond the Zambezi, as the [[Urema Valley]] of central Mozambique.<ref name="Steinbruck_2010">{{Cite journal |last=Steinbruck |first=F. |date=2010 |title=Geology and geomorphology of the Urema Graben with emphasis on the evolution of Lake Urema |journal=Journal of African Earth Sciences |volume=58 |issue=2 |pages=272–284 |doi=10.1016/j.jafrearsci.2010.03.007 |bibcode=2010JAfES..58..272S |issn=1464-343X}}</ref> | |||
[[ | |||
The | ==Ornithology== | ||
The Great Rift Valley/Red Sea flyway is recognised as an important part of the [[Asian–East African Flyway]] and the second most important flyway globally for migratory [[soaring bird]]s.<ref name="Awad_ettal_2017">{{Cite journal |last1=Awad |first1=S.I. |last2=Farhoud |first2=M.H. |last3=Saada Abu |first3=R.K. |last4=Busse |first4=P. |date=2017 |title=Long-term Bird RInging in Palestine |journal=The Ring |volume=39 |pages=83–102 |doi=10.1515/ring-2017-0003|doi-access=free }}</ref> Species that use this route include the [[European honey buzzard]] (''Pernis apivorus''), the [[Steppe eagle]] (''Aquila nipalensis''), [[Common buzzard]] (''Buteo buteo''), the [[Lesser spotted eagle]] (''Clanga pomarina''), the [[White Stork]] (''Ciconia ciconia'') and the [[Great White Pelican]] (''Pelecanus onocrotalus'').<ref name="Newton_2023">{{Cite book |last=Newton |first=I. |title=The Migration Ecology of Birds |publisher=Academic Press |isbn=9780128237526 |pages=118–121 |chapter=7. Raptors and soaring birds |date=2 December 2023 }}</ref> | |||
==Other uses== | |||
In many other fields such as [[epidemiology]] (see for instance [[Rift Valley fever]]),<ref name=WHO2010>{{cite web|title=Rift Valley fever|work=Fact sheet N°207|url=https://www.who.int/mediacentre/factsheets/fs207/en/|publisher=World Health Organization|access-date=21 March 2014|date=May 2010|url-status=live|archive-url=https://web.archive.org/web/20140415092827/http://www.who.int/mediacentre/factsheets/fs207/en/|archive-date=15 April 2014}}</ref> [[paleontology]], [[archaeology]],<ref name="Heitkamp">{{Cite book |last=Heitkamp |first=K.L. |title=The Rift Valley and the Archaeological Evidence of the First Humans |date=15 July 2016 |publisher=The Rosen Publishing Group, Inc |isbn=9781499463217}}</ref> [[ecology]]<ref name="Fujiwara_etal_2014">{{Cite journal |last1=Fujiwara |first1=K. |last2=Furukawa |first2=T. |last3=Kiboi |first3=S. |last4=Mathenge |first4=S. |last5=Mutiso |first5=P. |last6=Hayashi |first6=H. |last7=Meguro |first7=S. |date=2014 |title=Forest types and biodiversity around the Great Rift Valley in Kenya |journal=Contributii Botanice |volume=49 |pages=143 |issn=0069-9616}}</ref> and [[zoology]],<ref name= Bat/> the term is used to describe the local part of the GRV that is relevant to the particular study. | |||
==Notes== | |||
{{Notelist}} | |||
==References== | ==References== | ||
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*''Photographic atlas of the Mid-Atlantic Ridge Rift Valley'', 1977, {{ISBN|978-0-387-90247-0}} | *''Photographic atlas of the Mid-Atlantic Ridge Rift Valley'', 1977, {{ISBN|978-0-387-90247-0}} | ||
*''Rift Valley fever : an emerging human and animal problem'', 1982, {{ISBN|978-92-4-170063-4}} | *''Rift Valley fever : an emerging human and animal problem'', 1982, {{ISBN|978-92-4-170063-4}} | ||
*'' | *''What is a rift valley?'', Giacomo Corti (National Research Council of Italy, Institute of Geosciences and Earth Resources) – The Ethiopian Rift Valley, 2026, [https://ethiopianrift.cnr.it/what-is-a-rift-valley/] | ||
* [https://www.cnn.com/2018/04/05/africa/crack-africa-rift-valley-continent-splitting-two/index.html Big crack is evidence that East Africa could be splitting in two, by Lucia Perez Diaz, CNN. Updated April 5, 2018] | * [https://www.cnn.com/2018/04/05/africa/crack-africa-rift-valley-continent-splitting-two/index.html Big crack is evidence that East Africa could be splitting in two, by Lucia Perez Diaz, CNN. Updated April 5, 2018] | ||
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[[Category:Landforms of Yemen]] | [[Category:Landforms of Yemen]] | ||
[[Category:Landforms of Rwanda]] | |||
[[Category:Landforms of Tanzania]] | [[Category:Landforms of Tanzania]] | ||
[[Category:Landforms of the Democratic Republic of the Congo]] | [[Category:Landforms of the Democratic Republic of the Congo]] | ||
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[[Category:Geology of the Democratic Republic of the Congo]] | [[Category:Geology of the Democratic Republic of the Congo]] | ||
Latest revision as of 05:24, 20 May 2026
The Great Rift Valley (GRV) is a series of contiguous geographic depressions, approximately 6,500 kilometres (4,000 mi) in total length, which, in its original definition, runs from "the plains of northern Syria" in the north,[lower-alpha 1] through the Red Sea, to Mozambique in the south.[2][3] The term remains in use in the fields of geography, zoology, ecology, paleontology and other disciplines, but it is now rarely used in geology where the term "Afro-Arabian Rift System" is preferred, which describes the series of geological structures that have given rise to the geographical feature.[4] Great Rift Valley is also often used to refer to valleys, such as the Kenyan Rift Valley, within the East African Rift system.
The term was introduced by British geologist John Walter Gregory in 1896, following on from the work of Austrian geologist Eduard Suess, who first proposed the existence of a linked set of features extending from Syria to Mozambique.[2]
Geology
The Afro-Arabian Rift (AAR) is a series of major geological structures that have created the observed topographic features that make up the Great Rift Valley. The northern part of the AAR is formed by the Dead Sea Transform (DST) (also known as the Dead Sea or Levantine rift), the transform type boundary between the Arabian plate and the African (Nubian) plate. It extends southwards from the Marash triple junction in southeastern Turkey, where it meets the East Anatolian Fault, to the mouth of the Gulf of Aqaba where it joins with the Red Sea Rift. The dominant displacement along the DST is left-lateral strike-slip, with transtension along the southern part, transpression in the central section in Lebanon and local transtension within overall transpression in the northern part. Transtension has produced a series of pull-apart basins, the Dead Sea, Sea of Galilee, Hula basin and the Ghab basin. The transpression has led to the uplift of the Anti-Lebanon mountains and Mount Lebanon either side of the Beqaa valley.[5]
The Red Sea Rift is a mid-ocean ridge that accommodates the increasing separation between the Nubian and Arabian plates. The southeastern end of the Red Sea Rift links to both the western end of the Aden Ridge and the northern end of the East African Rift system (EARS), at the Afar triple junction.[6]
Sited next to the triple junction, the Afar triangle is an area of thinned and heavily intruded continental crust. The EARS continues to the south of the Afar triangle as the Main Ethiopian Rift passing through the strongly uplifted Ethiopian Highlands. Further south, the EARS splits into two main parts, the western Albertine Rift and the eastern Gregory Rift that pass to either side of the Victoria microplate, before joining again to the north of Lake Malawi. The EARS continues southwards to the coast along Lake Malawi and the Urema Graben. The Main Ethiopian and Gregory rifts are associated with major off-axis volcanism and many of the active basins within the rift are at least part filled with volcanic products. The Albertine Rift and its southward continuation into Mozambique are dominated by the formation of half-graben basins with major subsidence and flank uplifts.[7]
Geography
Asian section
The most northerly part of the GRV is the Ghab Plain, developed above the Ghab basin, along the valley of the Orontes River in northern Syria. The next section to the south of the Ghab plain is the Beqaa valley, which contains two rivers, the Orontes river, which drains northwards and the Litani, which drains southwestwards.[3] At the southern end of the valley, where the Litani river turns abruptly westwards, it comes within 5 km of the Hisbai river, part of the headwaters of the Jordan river. Beyond the Beqaa valley, the remaining part of the GRF in Asia is known as the Jordan Rift Valley, extending down to the Red Sea. The Hula valley, which lies above the Hula basin, is a nearly completely flat valley at about 70 m elevation, confined between the drainage basin of the many tributaries of the Jordan river to the north, the Golan heights to the east, the Naftali mountains to the west, the drainage basin of further tributaries to the southwest and the Korazim plateau to the south. The Jordan river passes south through the plateau in a gorge before reaching the Sea of Galilee (Lake Kinneret).[8] The Sea of Galilee is the most northerly part of the Dead Sea depression, the base of which is all below sea level. The full length of the depression was filled during the Pleistocene by Lake Lisan, although the lake surface was still about 200 m below sea level at its highest. The area of the depression below sea level is approximately 5,000 km2. The deepest part of the depression is occupied by the Dead Sea, while another local deep is the location of the Sea of Galilee. Almost the entire depression is flanked by steep sides.[9] The section between the Dead Sea depression and the Gulf of Aqaba is known as Arabah, the northern part of which is also known as the Arava valley. It rises steeply from the Dead Sea before rising much more gradually up to the watershed at an elevation of about 200m. before descending gradually to the Gulf of Aqaba. The southern part of this section is well-defined and narrower than the northern part, being generally 10 km or less wide, compared to 30 km further north, an area that lacks a clear western edge.[10][3] The Gulf of Aqaba is a relatively narrow gulf that extends 160 km from the southern end of the Arabah valley to the Straits of Tiran, its junction with the Red Sea. It contains a set of deeps, the Elat, Aragonese, Dakar and Tiran, with the greatest depth being reached in the Aragonese deep of 1850 m. The gulf narrows and shallows markedly in the Strait of Tiran, being only 13 km wide and about 250 m deep. Beyond the strait, within the Red Sea, the ~1,400 m deep Hume Deep is also developed.[11]
Red Sea
The Asian and African sections of the GRV are linked by the Red Sea. The Red Sea is characterised by broad relatively shallow flanks and a narrow (<60 km wide), deep central valley that reaches a maximum depth of 2,860 m.[6]
African section
The first feature south of the Red Sea that is considered to be part of the GRV is the Danakil Depression, within the Afar Depression, formed between the Ethiopian plateau to the west and the Danakil Alps to the east. The deepest part of the depression is well below sea level, reaching a general ~120m below in the northern part. To the south the depression becomes progressively obscured by the volcanic Erta Ale Range. The next clearly defined section of the GRV is the Main Ethiopian Rift (MER) valley, bordered by the Ethiopian and Somalian plateaus. The MER has an overall northeast–southwest trend and has been divided into three parts; the northern, central and southern sections. The northern MER extends southwards from the Afar Depression as far as Lake Koka. It is characterised by a high level of volcanic activity. The central section extends from Lake Koka to Lake Awasa, while the southern section runs from there to what is known as the "broadly rifted zone". The central and southern sections contain several lakes and are less affected by volcanic activity. The level of the rift valley floor in the MER climbs continuously from the Afar Depression into the central section, where it reaches an elevation of about 1,700 m, before descending gradually into the "broadly-rifted zone".[12]
In the "broadly rifted zone", the GRV becomes indistinct. Further south the GRV splits into two separate parts, the western or Albertine rift and the eastern or Gregory rift. The northernmost part of the eastern branch is formed by the valley of the Omo river in southern Ethiopia and Lake Turkana in Kenya.[13] Much of the eastern branch lies in Kenya and is often referred to as the Kenya Rift Valley. The rift valley floor is punctuated by relatively small lakes and numerous volcanoes. Many of these lakes are saline and alkaline in nature, such as Lake Bogoria and Lake Natron. The eastern part of the GRV continues into Tanzania, where it spreads out in what is known as the "North Tanzanian Divergence", with rift structures extending to the southwest (Lake Eyasi), to the south (Lake Manyara) and the Pangani River basin to the southeast.[14] In addition to the smaller volcanoes along the rift axis, there are large volcanic edifices on the rift shoulders, such as Mount Kenya and Mount Kilimanjaro, the highest mountains in Africa. There are national parks associated with many of the lakes and the larger volcanoes, such as the Lake Baringo National Park, the Lake Nakuru National Park and the Mount Kenya National Park.[15]
The western branch of the GRV starts from the north with the Rhino Camp basin, before stepping to the southeast and continuing along Lake Albert. The Albert River (part of the White Nile) passes through this zone of overlap and on through the Rhino Camp basin.[16] The western branch consists mainly of a series of deep lakes, Lake Albert, Lake Rutanzige, Lake Kivu, Lake Tanganyika and Lake Rukwa. Of these, only Rukwa is endorheic and alkaline, with the others being through-drained and freshwater. Lake Tanganyika is the second largest and second deepest freshwater lake in the world. The western branch is bordered by some of the highest mountains in Africa, including the Virunga Mountains, Mitumba Mountains, and Ruwenzori Range. Much of this area lies within the boundaries of national parks, such as Virunga National Park in the Democratic Republic of Congo, Rwenzori National Park and Queen Elizabeth National Park in Uganda, and Volcanoes National Park in Rwanda.[15]
The southernmost section of the GRV includes Lake Malawi, the third-deepest freshwater body in the world, which reaches 706 metres (2,316 ft) in depth and separates the Nyassa plateau of Northern Mozambique from Malawi. The rift extends southwards from Lake Malawi as the valley of the Shire River, which flows from the lake into the Zambezi River. The rift valley continues south, beyond the Zambezi, as the Urema Valley of central Mozambique.[17]
Ornithology
The Great Rift Valley/Red Sea flyway is recognised as an important part of the Asian–East African Flyway and the second most important flyway globally for migratory soaring birds.[18] Species that use this route include the European honey buzzard (Pernis apivorus), the Steppe eagle (Aquila nipalensis), Common buzzard (Buteo buteo), the Lesser spotted eagle (Clanga pomarina), the White Stork (Ciconia ciconia) and the Great White Pelican (Pelecanus onocrotalus).[19]
Other uses
In many other fields such as epidemiology (see for instance Rift Valley fever),[20] paleontology, archaeology,[21] ecology[22] and zoology,[1] the term is used to describe the local part of the GRV that is relevant to the particular study.
Notes
- ↑ Ottoman Syria at the end of the 19th-century included what is now the southern Turkish Hatay Province.[1]
References
- ↑ 1.0 1.1 Benda, Petr; et al. (January 2006). "Bats (Mammalia: Chiroptera) of the Eastern Mediterranean. Part 4. Bat fauna of Syria: distribution, systematics, ecology". Acta Soc. Zool. Bohem. (70): 1–329 (9). ISSN 1211-376X. Retrieved 9 September 2024 – via ResearchGate.
- ↑ 2.0 2.1 Gregory, John Walter (1896). The Great Rift Valley: Being the Narrative of a Journey to Mount Kenya and Lake Baringo with Some Account of the Geology, Natural History, Anthropology and Future Prospect of British East Africa. Routledge. p. 422 pages. ISBN 0-7146-1812-8.
- ↑ 3.0 3.1 3.2 Drysdale, A. (2025). The Middle East and North Africa: A Contemporary Geography. Bloomsbury Publishing. p. 21. ISBN 9798881859077.
- ↑ Girdler, R. W. (1991-10-30). "The Afro-Arabian rift system—an overview". Tectonophysics. 197 (2): 139–153. Bibcode:1991Tectp.197..139G. doi:10.1016/0040-1951(91)90038-T. ISSN 0040-1951.
- ↑ Garfunkel, Z. (2014). "Lateral Motion and Deformation Along the Dead Sea Transform". In Garfunkel, Z.; Ben-Avraham, Z.; Kagan, E. (eds.). Dead Sea Transform Fault System: Reviews. Modern Approaches in Solid Earth Sciences. 6. Springer. pp. 109–150. doi:10.1007/978-94-017-8872-4_5. ISBN 978-94-017-8871-7.
- ↑ 6.0 6.1 Augustin, N.; van der Zwan, F.M.; Devey, C.W.; Ligi, M.; Kwasnitschka, T.; Feldens, P.; Bantan, R.A.; Basaham, A.S. (2016). "Geomorphology of the central Red Sea Rift: Determining spreading processes". Geomorphology. 274: 162–179. Bibcode:2016Geomo.274..162A. doi:10.1016/j.geomorph.2016.08.028.
- ↑ Macgregor, D. (2015). "History of the development of the East African Rift System: A series of interpreted maps through time". Journal of African Earth Sciences. 101: 232–252. Bibcode:2015JAfES.101..232M. doi:10.1016/j.jafrearsci.2014.09.016.
- ↑ Goshen, M. (2023). Agriculture, Recreation, Water Quality and Nature Protection in the Hula Valley, Israel. Springer-Nature. p. 1. ISBN 9783031234125. ISSN 2194-315X.
- ↑ Hall, J.K. (1996). "Digital topography and bathymetry of the area of the Dead Sea Depression". Tectonophysics. 266 (1–4): 177–185. Bibcode:1996Tectp.266..177H. doi:10.1016/S0040-1951(96)00189-8.
- ↑ Bienkowski, P. (2006). "The Wadi Arabah: meanings in a contested landscape". In Bienkowski, P.; Galor, K. (eds.). Crossing the Rift: Resources, Routes, Settlement Patterns and Interaction in the Wadi Arabah. Levant supplementary series. 3. Council for British Research in the Levant and Oxbow. ISBN 9781842172094.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Corti, G. (2009). "Continental rift evolution: From rift initiation to incipient break-up in the Main Ethiopian Rift, East Africa". Earth Science Reviews. 96 (1–2): 1–53. Bibcode:2009ESRv...96....1C. doi:10.1016/j.earscirev.2009.06.005.
- ↑ Lepre, C.J. (2014). "Early Pleistocene lake formation and hominin origins in the Turkana–Omo rift". Quaternary Science Reviews. 102: 181–191. Bibcode:2014QSRv..102..181L. doi:10.1016/j.quascirev.2014.08.012.
- ↑ Dawson, J.B. (1992). "Neogene tectonics and volcanicity in the North Tanzania sector of the Gregory Rift Valley: contrasts with the Kenya sector". Tectonophysics. 204 (1–2): 81–83, 87–92. Bibcode:1992Tectp.204...81D. doi:10.1016/0040-1951(92)90271-7.
- ↑ 15.0 15.1 Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Katumwehe, A.B.; Abdelsalam, M.G.; Atekwana, E.A. (2015). "The role of pre-existing Precambrian structures in rift evolution: The Albertine and Rhino grabens, Uganda". Tectonophysics. 646: 117–129. Bibcode:2015Tectp.646..117K. doi:10.1016/j.tecto.2015.01.022.
- ↑ Steinbruck, F. (2010). "Geology and geomorphology of the Urema Graben with emphasis on the evolution of Lake Urema". Journal of African Earth Sciences. 58 (2): 272–284. Bibcode:2010JAfES..58..272S. doi:10.1016/j.jafrearsci.2010.03.007. ISSN 1464-343X.
- ↑ Awad, S.I.; Farhoud, M.H.; Saada Abu, R.K.; Busse, P. (2017). "Long-term Bird RInging in Palestine". The Ring. 39: 83–102. doi:10.1515/ring-2017-0003.
- ↑ Newton, I. (2 December 2023). "7. Raptors and soaring birds". The Migration Ecology of Birds. Academic Press. pp. 118–121. ISBN 9780128237526.
- ↑ "Rift Valley fever". Fact sheet N°207. World Health Organization. May 2010. Archived from the original on 15 April 2014. Retrieved 21 March 2014.
- ↑ Heitkamp, K.L. (15 July 2016). The Rift Valley and the Archaeological Evidence of the First Humans. The Rosen Publishing Group, Inc. ISBN 9781499463217.
- ↑ Fujiwara, K.; Furukawa, T.; Kiboi, S.; Mathenge, S.; Mutiso, P.; Hayashi, H.; Meguro, S. (2014). "Forest types and biodiversity around the Great Rift Valley in Kenya". Contributii Botanice. 49: 143. ISSN 0069-9616.
Further reading
- Africa's Great Rift Valley, 2001, ISBN 978-0-8109-0602-0
- Tribes of the Great Rift Valley, 2007, ISBN 978-0-8109-9411-9
- East African Rift Valley lakes, 2006, OCLC 76876862
- Photographic atlas of the Mid-Atlantic Ridge Rift Valley, 1977, ISBN 978-0-387-90247-0
- Rift Valley fever : an emerging human and animal problem, 1982, ISBN 978-92-4-170063-4
- What is a rift valley?, Giacomo Corti (National Research Council of Italy, Institute of Geosciences and Earth Resources) – The Ethiopian Rift Valley, 2026, [1]
- Big crack is evidence that East Africa could be splitting in two, by Lucia Perez Diaz, CNN. Updated April 5, 2018
External links
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