Afar Triangle: Difference between revisions

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{{Short description|Geological depression caused by the Afar triple junction}}
{{Short description|Geological depression caused by the Afar triple junction}}
[[File:Topographic30deg N0E30.png|thumb|upright=1.4|Topographic map showing the Afar Triangle, which corresponds to the shaded area in the location map shown above]]
[[File:Topographic30deg N0E30.png|thumb|upright=1.4|Topographic map showing the Afar Triangle]]
The '''Afar Triangle''' (also called the '''Afar Depression''') is a [[geological depression]] caused by the [[Afar triple junction]], which is part of the [[Great Rift Valley (geographical concept)|Great Rift Valley]] in [[East Africa]]. The region has disclosed fossil specimens of the very earliest [[hominins]]; that is, the earliest of the human clade, and it is thought by some paleontologists to be the cradle of the evolution of humans. The Depression overlaps the borders of [[Eritrea]], [[Djibouti]] and the entire [[Afar (region)|Afar Region]] of [[Ethiopia]]; and it contains the [[List of places on land with elevations below sea level|lowest point]] in [[Africa]], [[Lake Assal (Djibouti)|Lake Assal]], [[Djibouti]], at {{Convert|155|m|ft|abbr=on|sp=us}} below sea level.
The '''Afar Triangle''' (also called the '''Afar Depression''') is a [[geological depression]] caused by the [[Afar triple junction]], which is part of the [[Great Rift Valley (geographical concept)|Great Rift Valley]] in [[East Africa]]. The region has disclosed fossil specimens of the very earliest [[hominins]]; that is, the earliest of the human clade, and it is thought by some paleontologists to be the cradle of the evolution of humans. The Depression overlaps the borders of [[Eritrea]], [[Djibouti]] and the entire [[Afar (region)|Afar Region]] of [[Ethiopia]]; and it contains the [[List of places on land with elevations below sea level|lowest point]] in [[Africa]], [[Lake Assal (Djibouti)|Lake Assal]], [[Djibouti]], at {{Convert|155|m|ft|abbr=on|sp=us}} below sea level.


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[[File:Tectonic map of the Afar Depression.jpg|thumb|Tectonic map of the Afar Depression showing the small scale [[Plate tectonics|plate]] configuration, the velocities of extension and the active [[rift]] segments.]]
[[File:Tectonic map of the Afar Depression.jpg|thumb|Tectonic map of the Afar Depression showing the small scale [[Plate tectonics|plate]] configuration, the velocities of extension and the active [[rift]] segments.]]
[[File:Geological map of the Afar Depression.jpg|thumb|[[Geological map]] of the Afar Depression showing the [[Igneous rock|magmatic rocks]] from old (yellow) to recent (dark red), as well as the [[Fault (geology)|fault]] pattern. ]]
[[File:Geological map of the Afar Depression.jpg|thumb|[[Geological map]] of the Afar Depression showing the [[Igneous rock|magmatic rocks]] from old (yellow) to recent (dark red), as well as the [[Fault (geology)|fault]] pattern. ]]
The Afar Depression is a [[plate tectonics|tectonic]] [[triple junction#Examples|triple junction]] (the [[Afar triple junction]]), where the spreading ridges of the [[Red Sea Rift|Red Sea]] and the [[Gulf of Aden]] meet the [[Great Rift Valley|East African Rift]]. These rifts are caused by the northeastward movement of the [[Arabian plate]] (approximately 20 mm/yr<ref>{{Cite journal |last1=Viltres |first1=Renier |last2=Jónsson |first2=Sigurjón |last3=Alothman |first3=Abdulaziz O. |last4=Liu |first4=Shaozhuo |last5=Leroy |first5=Sylvie |last6=Masson |first6=Frédéric |last7=Doubre |first7=Cécile |last8=Reilinger |first8=Robert |date=2022 |title=Present-Day Motion of the Arabian Plate |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021TC007013 |journal=Tectonics |language=en |volume=41 |issue=3 |pages=e2021TC007013 |doi=10.1029/2021TC007013 |bibcode=2022Tecto..4107013V |issn=1944-9194}}</ref>) and the much slower eastward movement of the [[Somali plate|Somalian plate]] (approximately 5 mm/yr<ref>{{Cite journal |last1=Stamps |first1=D.S. |last2=Kreemer |first2=C. |last3=Fernandes |first3=R. |last4=Rajaonarison |first4=T.A. |last5=Rambolamanana |first5=G. |date=2021-09-23 |title=Redefining East African Rift System kinematics |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/49/2/150/591119/Redefining-East-African-Rift-System-kinematics?redirectedFrom=fulltext |journal=Geology |volume=49 |issue=2 |pages=150–155 |doi=10.1130/G47985.1 |bibcode=2021Geo....49..150S |issn=0091-7613}}</ref>) relative to the [[African plate|Nubian (African) plate]].
The Afar Depression is a [[plate tectonics|tectonic]] [[triple junction#Examples|triple junction]] (the [[Afar triple junction]]), where the spreading ridges of the [[Red Sea Rift|Red Sea]] and the [[Gulf of Aden]] meet the [[Great Rift Valley|East African Rift]]. These rifts are caused by the northeastward movement of the [[Arabian plate]] (approximately 20 mm/yr<ref>{{Cite journal |last1=Viltres |first1=Renier |last2=Jónsson |first2=Sigurjón |last3=Alothman |first3=Abdulaziz O. |last4=Liu |first4=Shaozhuo |last5=Leroy |first5=Sylvie |last6=Masson |first6=Frédéric |last7=Doubre |first7=Cécile |last8=Reilinger |first8=Robert |date=2022 |title=Present-Day Motion of the Arabian Plate |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021TC007013 |journal=Tectonics |language=en |volume=41 |issue=3 |pages=e2021TC007013 |doi=10.1029/2021TC007013 |bibcode=2022Tecto..4107013V |issn=1944-9194}}</ref>) and the much slower eastward movement of the [[Somali plate|Somalian plate]] (approximately 5 mm/yr<ref>{{Cite journal |last1=Stamps |first1=D.S. |last2=Kreemer |first2=C. |last3=Fernandes |first3=R. |last4=Rajaonarison |first4=T.A. |last5=Rambolamanana |first5=G. |date=2021-09-23 |title=Redefining East African Rift System kinematics |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/49/2/150/591119/Redefining-East-African-Rift-System-kinematics?redirectedFrom=fulltext |journal=Geology |volume=49 |issue=2 |pages=150–155 |doi=10.1130/G47985.1 |bibcode=2021Geo....49..150S |issn=0091-7613|url-access=subscription }}</ref>) relative to the [[African plate|Nubian (African) plate]].


At smaller scale, the [[tectonics]] of the Afar Depression is more complex. An independent [[Microplate (geology)|microplate]], the [[Danakil microplate|Danakil (or Arrata) microplate]], is carrying a piece of continental material (the Danakil block) between the Afar and the Red Sea and is rotating counterclockwise,<ref name=":8">{{Cite book |last=Varet |first=Jacques |url=http://link.springer.com/10.1007/978-3-319-60865-5 |title=Geology of Afar (East Africa) |date=2018 |publisher=Springer International Publishing |isbn=978-3-319-60863-1 |series=Regional Geology Reviews |location=Cham |doi=10.1007/978-3-319-60865-5|bibcode=2018geaf.book.....V }}</ref><ref>{{Cite journal |last1=Viltres |first1=Renier |last2=Jónsson |first2=Sigurjón |last3=Ruch |first3=Joël |last4=Doubre |first4=Cécile |last5=Reilinger |first5=Robert |last6=Floyd |first6=Michael |last7=Ogubazghi |first7=Ghebrebrhan |date=2020-06-01 |title=Kinematics and deformation of the southern Red Sea region from GPS observations |url=https://academic.oup.com/gji/article/221/3/2143/5800989 |journal=Geophysical Journal International |language=en |volume=221 |issue=3 |pages=2143–2154 |doi=10.1093/gji/ggaa109 |doi-access=free |issn=0956-540X}}</ref><ref name=":0">{{Cite journal |last1=Rime |first1=Valentin |last2=Foubert |first2=Anneleen |last3=Ruch |first3=Joël |last4=Kidane |first4=Tesfaye |date=2023-09-01 |title=Tectonostratigraphic evolution and significance of the Afar Depression |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825223002088 |journal=Earth-Science Reviews |volume=244 |pages=104519 |doi=10.1016/j.earscirev.2023.104519 |bibcode=2023ESRv..24404519R |issn=0012-8252|doi-access=free }}</ref> causing the slow propagation of the Afar Rift to the north and the propagation of the Red Sea rift to the south.<ref name=":0" />  
At smaller scale, the [[tectonics]] of the Afar Depression is more complex. An independent [[Microplate (geology)|microplate]], the [[Danakil microplate|Danakil (or Arrata) microplate]], is carrying a piece of continental material (the Danakil block) between the Afar and the Red Sea and is rotating counterclockwise,<ref name=":8">{{Cite book |last=Varet |first=Jacques |url=http://link.springer.com/10.1007/978-3-319-60865-5 |title=Geology of Afar (East Africa) |date=2018 |publisher=Springer International Publishing |isbn=978-3-319-60863-1 |series=Regional Geology Reviews |location=Cham |doi=10.1007/978-3-319-60865-5|bibcode=2018geaf.book.....V }}</ref><ref>{{Cite journal |last1=Viltres |first1=Renier |last2=Jónsson |first2=Sigurjón |last3=Ruch |first3=Joël |last4=Doubre |first4=Cécile |last5=Reilinger |first5=Robert |last6=Floyd |first6=Michael |last7=Ogubazghi |first7=Ghebrebrhan |date=2020-06-01 |title=Kinematics and deformation of the southern Red Sea region from GPS observations |url=https://academic.oup.com/gji/article/221/3/2143/5800989 |journal=Geophysical Journal International |language=en |volume=221 |issue=3 |pages=2143–2154 |doi=10.1093/gji/ggaa109 |doi-access=free |issn=0956-540X}}</ref><ref name=":0">{{Cite journal |last1=Rime |first1=Valentin |last2=Foubert |first2=Anneleen |last3=Ruch |first3=Joël |last4=Kidane |first4=Tesfaye |date=2023-09-01 |title=Tectonostratigraphic evolution and significance of the Afar Depression |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825223002088 |journal=Earth-Science Reviews |volume=244 |pages=104519 |doi=10.1016/j.earscirev.2023.104519 |bibcode=2023ESRv..24404519R |issn=0012-8252|doi-access=free }}</ref> causing the slow propagation of the Afar Rift to the north and the propagation of the Red Sea rift to the south.<ref name=":0" />  


The recent geological history of the Afar Depression started around 33 million years ago, before any [[rifting]], with the eruption of the Ethiopian [[Flood basalt|Flood Basalts]] that covered large parts of [[Ethiopia]] and [[Yemen]] with hundreds to thousands of meters of [[Volcanic rock|volcanic rocks]].<ref>{{Cite journal |last1=Hofmann |first1=C. |last2=Courtillot |first2=V. |last3=Féraud |first3=G. |last4=Rochette |first4=P. |last5=Yirgu |first5=G. |last6=Ketefo |first6=E. |last7=Pik |first7=R. |date=October 1997 |title=Timing of the Ethiopian flood basalt event and implications for plume birth and global change |url=https://www.nature.com/articles/39853 |journal=Nature |language=en |volume=389 |issue=6653 |pages=838–841 |doi=10.1038/39853 |bibcode=1997Natur.389..838H |issn=1476-4687}}</ref><ref>{{Cite journal |last1=Baker |first1=Joel |last2=Snee |first2=Lawrence |last3=Menzies |first3=Martin |date=1996-02-01 |title=A brief Oligocene period of flood volcanism in Yemen: implications for the duration and rate of continental flood volcanism at the Afro-Arabian triple junction |url=https://linkinghub.elsevier.com/retrieve/pii/0012821X95002296 |journal=Earth and Planetary Science Letters |volume=138 |issue=1 |pages=39–55 |doi=10.1016/0012-821X(95)00229-6 |bibcode=1996E&PSL.138...39B |issn=0012-821X}}</ref><ref>{{Citation |last1=Mohr |first1=Paul |title=The Ethiopian Flood Basalt Province |date=1988 |work=Continental Flood Basalts |pages=63–110 |editor-last=Macdougall |editor-first=J. D. |url=https://link.springer.com/chapter/10.1007/978-94-015-7805-9_3 |access-date=2025-05-16 |place=Dordrecht |publisher=Springer Netherlands |language=en |doi=10.1007/978-94-015-7805-9_3 |isbn=978-94-015-7805-9 |last2=Zanettin |first2=Bruno}}</ref><ref>{{Cite journal |last1=Coulié |first1=E |last2=Quidelleur |first2=X |last3=Gillot |first3=P. -Y |last4=Courtillot |first4=V |last5=Lefèvre |first5=J. -C |last6=Chiesa |first6=S |date=2003-02-15 |title=Comparative K–Ar and Ar/Ar dating of Ethiopian and Yemenite Oligocene volcanism: implications for timing and duration of the Ethiopian traps |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X02010890 |journal=Earth and Planetary Science Letters |volume=206 |issue=3 |pages=477–492 |doi=10.1016/S0012-821X(02)01089-0 |bibcode=2003E&PSL.206..477C |issn=0012-821X}}</ref><ref>{{Cite journal |last=Rooney |first=Tyrone O. |date=2017-08-01 |title=The Cenozoic magmatism of East-Africa: Part I — Flood basalts and pulsed magmatism |url=https://linkinghub.elsevier.com/retrieve/pii/S0024493717301883 |journal=Lithos |volume=286-287 |pages=264–301 |doi=10.1016/j.lithos.2017.05.014 |bibcode=2017Litho.286..264R |issn=0024-4937|doi-access=free }}</ref> These eruptions were cause by a hot rising [[mantle plume]] that impacted the [[continental crust]] and produced large quantities of [[magma]].<ref>{{Cite journal |last1=Hansen |first1=Samantha E. |last2=Nyblade |first2=Andrew A. |last3=Benoit |first3=Margaret H. |date=2012-02-15 |title=Mantle structure beneath Africa and Arabia from adaptively parameterized P-wave tomography: Implications for the origin of Cenozoic Afro-Arabian tectonism |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X11007436 |journal=Earth and Planetary Science Letters |volume=319-320 |pages=23–34 |doi=10.1016/j.epsl.2011.12.023 |bibcode=2012E&PSL.319...23H |issn=0012-821X}}</ref><ref>{{Cite journal |last1=Civiero |first1=Chiara |last2=Lebedev |first2=Sergei |last3=Celli |first3=Nicolas L. |date=2022 |title=A Complex Mantle Plume Head Below East Africa-Arabia Shaped by the Lithosphere-Asthenosphere Boundary Topography |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GC010610 |journal=Geochemistry, Geophysics, Geosystems |language=en |volume=23 |issue=11 |pages=e2022GC010610 |doi=10.1029/2022GC010610 |bibcode=2022GGG....2310610C |issn=1525-2027|hdl=10261/286934 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Rooney |first1=Tyrone O. |last2=Herzberg |first2=Claude |last3=Bastow |first3=Ian D. |date=2012-01-01 |title=Elevated mantle temperature beneath East Africa |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/40/1/27/130670/Elevated-mantle-temperature-beneath-East-Africa?redirectedFrom=fulltext |journal=Geology |volume=40 |issue=1 |pages=27–30 |doi=10.1130/G32382.1 |bibcode=2012Geo....40...27R |issn=0091-7613}}</ref><ref>{{Cite journal |last1=Civiero |first1=Chiara |last2=Celli |first2=Nicolas L. |last3=Tesauro |first3=Magdala |date=2023-12-01 |title=Revisiting the geodynamics of the Middle East region from an integrated geophysical perspective |url=https://linkinghub.elsevier.com/retrieve/pii/S0264370723000455 |journal=Journal of Geodynamics |volume=158 |pages=102005 |doi=10.1016/j.jog.2023.102005 |bibcode=2023JGeo..15802005C |issn=0264-3707|hdl=11368/3066862 |hdl-access=free }}</ref> This impact of the mantle plume also caused the [[Dynamic topography|high topography]] of the region,<ref>{{Cite journal |last1=Moucha |first1=Robert |last2=Forte |first2=Alessandro M. |date=October 2011 |title=Changes in African topography driven by mantle convection |url=https://www.nature.com/articles/ngeo1235 |journal=Nature Geoscience |language=en |volume=4 |issue=10 |pages=707–712 |doi=10.1038/ngeo1235 |bibcode=2011NatGe...4..707M |issn=1752-0908}}</ref><ref>{{Cite journal |last1=Sembroni |first1=Andrea |last2=Faccenna |first2=Claudio |last3=Becker |first3=Thorsten W. |last4=Molin |first4=Paola |date=2024-10-01 |title=The uplift of the East Africa - Arabia swell |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825224002289 |journal=Earth-Science Reviews |volume=257 |pages=104901 |doi=10.1016/j.earscirev.2024.104901 |bibcode=2024ESRv..25704901S |issn=0012-8252|doi-access=free }}</ref> an effect still visible today.  
The recent geological history of the Afar Depression started around 33 million years ago, before any [[rifting]], with the eruption of the Ethiopian [[Flood basalt|Flood Basalts]] that covered large parts of [[Ethiopia]] and [[Yemen]] with hundreds to thousands of meters of [[Volcanic rock|volcanic rocks]].<ref>{{Cite journal |last1=Hofmann |first1=C. |last2=Courtillot |first2=V. |last3=Féraud |first3=G. |last4=Rochette |first4=P. |last5=Yirgu |first5=G. |last6=Ketefo |first6=E. |last7=Pik |first7=R. |date=October 1997 |title=Timing of the Ethiopian flood basalt event and implications for plume birth and global change |url=https://www.nature.com/articles/39853 |journal=Nature |language=en |volume=389 |issue=6653 |pages=838–841 |doi=10.1038/39853 |bibcode=1997Natur.389..838H |issn=1476-4687|url-access=subscription }}</ref><ref>{{Cite journal |last1=Baker |first1=Joel |last2=Snee |first2=Lawrence |last3=Menzies |first3=Martin |date=1996-02-01 |title=A brief Oligocene period of flood volcanism in Yemen: implications for the duration and rate of continental flood volcanism at the Afro-Arabian triple junction |url=https://linkinghub.elsevier.com/retrieve/pii/0012821X95002296 |journal=Earth and Planetary Science Letters |volume=138 |issue=1 |pages=39–55 |doi=10.1016/0012-821X(95)00229-6 |bibcode=1996E&PSL.138...39B |issn=0012-821X|url-access=subscription }}</ref><ref>{{Citation |last1=Mohr |first1=Paul |title=The Ethiopian Flood Basalt Province |date=1988 |work=Continental Flood Basalts |pages=63–110 |editor-last=Macdougall |editor-first=J. D. |url=https://link.springer.com/chapter/10.1007/978-94-015-7805-9_3 |access-date=2025-05-16 |place=Dordrecht |publisher=Springer Netherlands |language=en |doi=10.1007/978-94-015-7805-9_3 |isbn=978-94-015-7805-9 |last2=Zanettin |first2=Bruno|url-access=subscription }}</ref><ref>{{Cite journal |last1=Coulié |first1=E |last2=Quidelleur |first2=X |last3=Gillot |first3=P. -Y |last4=Courtillot |first4=V |last5=Lefèvre |first5=J. -C |last6=Chiesa |first6=S |date=2003-02-15 |title=Comparative K–Ar and Ar/Ar dating of Ethiopian and Yemenite Oligocene volcanism: implications for timing and duration of the Ethiopian traps |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X02010890 |journal=Earth and Planetary Science Letters |volume=206 |issue=3 |pages=477–492 |doi=10.1016/S0012-821X(02)01089-0 |bibcode=2003E&PSL.206..477C |issn=0012-821X|url-access=subscription }}</ref><ref>{{Cite journal |last=Rooney |first=Tyrone O. |date=2017-08-01 |title=The Cenozoic magmatism of East-Africa: Part I — Flood basalts and pulsed magmatism |url=https://linkinghub.elsevier.com/retrieve/pii/S0024493717301883 |journal=Lithos |volume=286-287 |pages=264–301 |doi=10.1016/j.lithos.2017.05.014 |bibcode=2017Litho.286..264R |issn=0024-4937|doi-access=free }}</ref> These eruptions were cause by a hot rising [[mantle plume]] that impacted the [[continental crust]] and produced large quantities of [[magma]].<ref>{{Cite journal |last1=Hansen |first1=Samantha E. |last2=Nyblade |first2=Andrew A. |last3=Benoit |first3=Margaret H. |date=2012-02-15 |title=Mantle structure beneath Africa and Arabia from adaptively parameterized P-wave tomography: Implications for the origin of Cenozoic Afro-Arabian tectonism |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X11007436 |journal=Earth and Planetary Science Letters |volume=319-320 |pages=23–34 |doi=10.1016/j.epsl.2011.12.023 |bibcode=2012E&PSL.319...23H |issn=0012-821X|url-access=subscription }}</ref><ref>{{Cite journal |last1=Civiero |first1=Chiara |last2=Lebedev |first2=Sergei |last3=Celli |first3=Nicolas L. |date=2022 |title=A Complex Mantle Plume Head Below East Africa-Arabia Shaped by the Lithosphere-Asthenosphere Boundary Topography |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GC010610 |journal=Geochemistry, Geophysics, Geosystems |language=en |volume=23 |issue=11 |pages=e2022GC010610 |doi=10.1029/2022GC010610 |bibcode=2022GGG....2310610C |issn=1525-2027|hdl=10261/286934 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Rooney |first1=Tyrone O. |last2=Herzberg |first2=Claude |last3=Bastow |first3=Ian D. |date=2012-01-01 |title=Elevated mantle temperature beneath East Africa |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/40/1/27/130670/Elevated-mantle-temperature-beneath-East-Africa?redirectedFrom=fulltext |journal=Geology |volume=40 |issue=1 |pages=27–30 |doi=10.1130/G32382.1 |bibcode=2012Geo....40...27R |issn=0091-7613|url-access=subscription }}</ref><ref>{{Cite journal |last1=Civiero |first1=Chiara |last2=Celli |first2=Nicolas L. |last3=Tesauro |first3=Magdala |date=2023-12-01 |title=Revisiting the geodynamics of the Middle East region from an integrated geophysical perspective |url=https://linkinghub.elsevier.com/retrieve/pii/S0264370723000455 |journal=Journal of Geodynamics |volume=158 |pages=102005 |doi=10.1016/j.jog.2023.102005 |bibcode=2023JGeo..15802005C |issn=0264-3707|hdl=11368/3066862 |hdl-access=free }}</ref> This impact of the mantle plume also caused the [[Dynamic topography|high topography]] of the region,<ref>{{Cite journal |last1=Moucha |first1=Robert |last2=Forte |first2=Alessandro M. |date=October 2011 |title=Changes in African topography driven by mantle convection |url=https://www.nature.com/articles/ngeo1235 |journal=Nature Geoscience |language=en |volume=4 |issue=10 |pages=707–712 |doi=10.1038/ngeo1235 |bibcode=2011NatGe...4..707M |issn=1752-0908|url-access=subscription }}</ref><ref>{{Cite journal |last1=Sembroni |first1=Andrea |last2=Faccenna |first2=Claudio |last3=Becker |first3=Thorsten W. |last4=Molin |first4=Paola |date=2024-10-01 |title=The uplift of the East Africa - Arabia swell |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825224002289 |journal=Earth-Science Reviews |volume=257 |pages=104901 |doi=10.1016/j.earscirev.2024.104901 |bibcode=2024ESRv..25704901S |issn=0012-8252|doi-access=free }}</ref> an effect still visible today.  


This [[Volcanism|volcanic activity]] weakened the crust and allowed the beginning of the separation between the Arabian plate and the Nubian plate.<ref>{{Cite journal |last1=Bellahsen |first1=N. |last2=Faccenna |first2=C. |last3=Funiciello |first3=F. |last4=Daniel |first4=J. M. |last5=Jolivet |first5=L. |date=2003-11-30 |title=Why did Arabia separate from Africa? Insights from 3-D laboratory experiments |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X03005168 |journal=Earth and Planetary Science Letters |volume=216 |issue=3 |pages=365–381 |doi=10.1016/S0012-821X(03)00516-8 |bibcode=2003E&PSL.216..365B |issn=0012-821X}}</ref><ref>{{Cite journal |last1=Koptev |first1=Alexander |last2=Gerya |first2=Taras |last3=Calais |first3=Eric |last4=Leroy |first4=Sylvie |last5=Burov |first5=Evgueni |date=2018-10-03 |title=Afar triple junction triggered by plume-assisted bi-directional continental break-up |journal=Scientific Reports |language=en |volume=8 |issue=1 |pages=14742 |doi=10.1038/s41598-018-33117-3 |issn=2045-2322 |pmc=6170478 |pmid=30283091|bibcode=2018NatSR...814742K }}</ref> The Gulf of Aden rift propagated westwards and rifting started in the Afar region approximately 28 million years ago, at the same time as in the southern Red Sea.<ref name=":0" /> Between 13 and 8 Ma, a major reorganization of the region took place.<ref name=":0" /> The [[Danakil microplate]] started rotating, causing the secession of tectonic activity in the [[Bab-el-Mandeb|southernmost Red Sea]], and propagation of the Afar rift in the [[Danakil Depression]] (i.e. the northern part of the Afar Triangle).<ref name=":0" /> At the same time, the [[Great Rift Valley, Ethiopia|Main Ethiopian Rift]] (the northernmost part of the [[East African Rift|East African Rift System]]) started to form and the Afar Depression became a [[triple junction]]<ref>{{Cite journal |last1=Wolfenden |first1=Ellen |last2=Ebinger |first2=Cynthia |last3=Yirgu |first3=Gezahegn |last4=Deino |first4=Alan |last5=Ayalew |first5=Dereje |date=2004-07-30 |title=Evolution of the northern Main Ethiopian rift: birth of a triple junction |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X04002705 |journal=Earth and Planetary Science Letters |volume=224 |issue=1 |pages=213–228 |doi=10.1016/j.epsl.2004.04.022 |bibcode=2004E&PSL.224..213W |issn=0012-821X}}</ref>. This movement in three different directions by three major [[List of tectonic plates|plates]] caused extension and thinning of the crust, explaining the general morphology of the Afar Depression.  
This [[Volcanism|volcanic activity]] weakened the crust and allowed the beginning of the separation between the Arabian plate and the Nubian plate.<ref>{{Cite journal |last1=Bellahsen |first1=N. |last2=Faccenna |first2=C. |last3=Funiciello |first3=F. |last4=Daniel |first4=J. M. |last5=Jolivet |first5=L. |date=2003-11-30 |title=Why did Arabia separate from Africa? Insights from 3-D laboratory experiments |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X03005168 |journal=Earth and Planetary Science Letters |volume=216 |issue=3 |pages=365–381 |doi=10.1016/S0012-821X(03)00516-8 |bibcode=2003E&PSL.216..365B |issn=0012-821X|url-access=subscription }}</ref><ref>{{Cite journal |last1=Koptev |first1=Alexander |last2=Gerya |first2=Taras |last3=Calais |first3=Eric |last4=Leroy |first4=Sylvie |last5=Burov |first5=Evgueni |date=2018-10-03 |title=Afar triple junction triggered by plume-assisted bi-directional continental break-up |journal=Scientific Reports |language=en |volume=8 |issue=1 |pages=14742 |doi=10.1038/s41598-018-33117-3 |issn=2045-2322 |pmc=6170478 |pmid=30283091|bibcode=2018NatSR...814742K }}</ref> The Gulf of Aden rift propagated westwards and rifting started in the Afar region approximately 28 million years ago, at the same time as in the southern Red Sea.<ref name=":0" /> Between 13 and 8 Ma, a major reorganization of the region took place.<ref name=":0" /> The [[Danakil microplate]] started rotating, causing the secession of tectonic activity in the [[Bab-el-Mandeb|southernmost Red Sea]], and propagation of the Afar rift in the [[Danakil Depression]] (i.e. the northern part of the Afar Triangle).<ref name=":0" /> At the same time, the [[Great Rift Valley, Ethiopia|Main Ethiopian Rift]] (the northernmost part of the [[East African Rift|East African Rift System]]) started to form and the Afar Depression became a [[triple junction]].<ref>{{Cite journal |last1=Wolfenden |first1=Ellen |last2=Ebinger |first2=Cynthia |last3=Yirgu |first3=Gezahegn |last4=Deino |first4=Alan |last5=Ayalew |first5=Dereje |date=2004-07-30 |title=Evolution of the northern Main Ethiopian rift: birth of a triple junction |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X04002705 |journal=Earth and Planetary Science Letters |volume=224 |issue=1 |pages=213–228 |doi=10.1016/j.epsl.2004.04.022 |bibcode=2004E&PSL.224..213W |issn=0012-821X|url-access=subscription }}</ref> This movement in three different directions by three major [[List of tectonic plates|plates]] caused extension and thinning of the crust, explaining the general morphology of the Afar Depression.  


During the [[Extensional tectonics|extension]], [[volcanism]] remained very important in the Depression, with kilometers of [[Volcanic rock|volcanic rocks]] dominated by [[Basalt|basalts]] emplaced in central Afar<ref name=":8" /><ref>{{Cite journal |last1=Lahitte |first1=Pierre |last2=Gillot |first2=Pierre-Yves |last3=Kidane |first3=Tesfaye |last4=Courtillot |first4=Vincent |last5=Bekele |first5=Abebe |date=2003 |title=New age constraints on the timing of volcanism in central Afar, in the presence of propagating rifts |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2001JB001689 |journal=Journal of Geophysical Research: Solid Earth |language=en |volume=108 |issue=B2 |page=2123 |doi=10.1029/2001JB001689 |bibcode=2003JGRB..108.2123L |issn=2156-2202}}</ref><ref>{{Cite journal |last=Rooney |first=Tyrone O. |date=2020-05-01 |title=The Cenozoic magmatism of East Africa: Part IV – The terminal stages of rifting preserved in the Northern East African Rift System |url=https://linkinghub.elsevier.com/retrieve/pii/S0024493720300189 |journal=Lithos |volume=360-361 |pages=105381 |doi=10.1016/j.lithos.2020.105381 |bibcode=2020Litho.36005381R |issn=0024-4937|doi-access=free }}</ref>. So much magmatic rocks were added to crust, at the surface as lava flows, but also in the crust as [[Igneous intrusion|intrusions]] and below the crust as [[Magmatic underplating|underplated]] material, that it did not thin as much as expected<ref name=":0" /><ref name=":1">{{Cite journal |last1=Rime |first1=Valentin |last2=Keir |first2=Derek |last3=Phethean |first3=Jordan |last4=Kidane |first4=Tesfaye |last5=Foubert |first5=Anneleen |date=2024-07-31 |title=Central Afar: An analogue for oceanic plateau development |url=https://pubs.geoscienceworld.org/gsa/geology/article/52/11/819/646098/Central-Afar-An-analogue-for-oceanic-plateau |journal=Geology |volume=52 |issue=11 |pages=819–824 |doi=10.1130/G52330.1 |bibcode=2024Geo....52..819R |issn=0091-7613|hdl=2158/1408188 |hdl-access=free }}</ref><ref name=":6">{{Cite journal |last=Stab |first=Martin |last2=Bellahsen |first2=Nicolas |last3=Pik |first3=Raphaël |last4=Quidelleur |first4=Xavier |last5=Ayalew |first5=Dereje |last6=Leroy |first6=Sylvie |date=2016 |title=Modes of rifting in magma-rich settings: Tectono-magmatic evolution of Central Afar |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2015TC003893 |journal=Tectonics |language=en |volume=35 |issue=1 |pages=2–38 |doi=10.1002/2015TC003893 |issn=1944-9194}}</ref>. This phenomenon is called ''magma-compensated thinning''<ref>{{Cite journal |last1=Thybo |first1=H. |last2=Nielsen |first2=C. A. |date=February 2009 |title=Magma-compensated crustal thinning in continental rift zones |url=https://www.nature.com/articles/nature07688 |journal=Nature |language=en |volume=457 |issue=7231 |pages=873–876 |doi=10.1038/nature07688 |bibcode=2009Natur.457..873T |issn=1476-4687}}</ref> and it can explain why the central Afar is the only part of the Gulf of Aden - Red Sea system that do not feature normal [[oceanic crust]].<ref name=":0" /><ref name=":1" /> Because of this high volcanic activity, some researchers propose that this region might never form a normal ocean, but instead form an [[oceanic plateau]], similar to [[Iceland]]<ref name=":1" />.
During the [[Extensional tectonics|extension]], [[volcanism]] remained very important in the Depression, with kilometers of [[Volcanic rock|volcanic rocks]] dominated by [[Basalt|basalts]] emplaced in central Afar.<ref name=":8" /><ref>{{Cite journal |last1=Lahitte |first1=Pierre |last2=Gillot |first2=Pierre-Yves |last3=Kidane |first3=Tesfaye |last4=Courtillot |first4=Vincent |last5=Bekele |first5=Abebe |date=2003 |title=New age constraints on the timing of volcanism in central Afar, in the presence of propagating rifts |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2001JB001689 |journal=Journal of Geophysical Research: Solid Earth |language=en |volume=108 |issue=B2 |page=2123 |doi=10.1029/2001JB001689 |bibcode=2003JGRB..108.2123L |issn=2156-2202}}</ref><ref>{{Cite journal |last=Rooney |first=Tyrone O. |date=2020-05-01 |title=The Cenozoic magmatism of East Africa: Part IV – The terminal stages of rifting preserved in the Northern East African Rift System |url=https://linkinghub.elsevier.com/retrieve/pii/S0024493720300189 |journal=Lithos |volume=360-361 |pages=105381 |doi=10.1016/j.lithos.2020.105381 |bibcode=2020Litho.36005381R |issn=0024-4937|doi-access=free }}</ref> So much magmatic rocks were added to crust, at the surface as lava flows, but also in the crust as [[Igneous intrusion|intrusions]] and below the crust as [[Magmatic underplating|underplated]] material, that it did not thin as much as expected.<ref name=":0" /><ref name=":1">{{Cite journal |last1=Rime |first1=Valentin |last2=Keir |first2=Derek |last3=Phethean |first3=Jordan |last4=Kidane |first4=Tesfaye |last5=Foubert |first5=Anneleen |date=2024-07-31 |title=Central Afar: An analogue for oceanic plateau development |url=https://pubs.geoscienceworld.org/gsa/geology/article/52/11/819/646098/Central-Afar-An-analogue-for-oceanic-plateau |journal=Geology |volume=52 |issue=11 |pages=819–824 |doi=10.1130/G52330.1 |bibcode=2024Geo....52..819R |issn=0091-7613|hdl=2158/1408188 |hdl-access=free }}</ref><ref name=":6">{{Cite journal |last=Stab |first=Martin |last2=Bellahsen |first2=Nicolas |last3=Pik |first3=Raphaël |last4=Quidelleur |first4=Xavier |last5=Ayalew |first5=Dereje |last6=Leroy |first6=Sylvie |date=2016 |title=Modes of rifting in magma-rich settings: Tectono-magmatic evolution of Central Afar |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2015TC003893 |journal=Tectonics |language=en |volume=35 |issue=1 |pages=2–38 |doi=10.1002/2015TC003893 |issn=1944-9194}}</ref> This phenomenon is called ''magma-compensated thinning''<ref>{{Cite journal |last1=Thybo |first1=H. |last2=Nielsen |first2=C. A. |date=February 2009 |title=Magma-compensated crustal thinning in continental rift zones |url=https://www.nature.com/articles/nature07688 |journal=Nature |language=en |volume=457 |issue=7231 |pages=873–876 |doi=10.1038/nature07688 |bibcode=2009Natur.457..873T |issn=1476-4687|url-access=subscription }}</ref> and it can explain why the central Afar is the only part of the Gulf of Aden - Red Sea system that do not feature normal [[oceanic crust]].<ref name=":0" /><ref name=":1" /> Because of this high volcanic activity, some researchers propose that this region might never form a normal ocean, but instead form an [[oceanic plateau]], similar to [[Iceland]].<ref name=":1" />  


[[File:Graben Afar ASTER 20020327.jpg|thumb|left|Satellite image of a [[graben]] in the Afar Depression.]]
[[File:Graben Afar ASTER 20020327.jpg|thumb|left|Satellite image of a [[graben]] in the Afar Depression.]]
[[Volcanism|Volcanic]] and [[Tectonics|tectonic]] activity is still very strong in the Depression. In different regions of the Afar, the extension is accommodated by [[Fault (geology)|faulting]] or [[Igneous intrusion|magmatic intrusions]]<ref name=":2">{{Cite journal |last1=Ebinger |first1=Cynthia |last2=Ayele |first2=Atalay |last3=Keir |first3=Derek |last4=Rowland |first4=Julie |last5=Yirgu |first5=Gezahegn |last6=Wright |first6=Tim |last7=Belachew |first7=Manahloh |last8=Hamling |first8=Ian |date=2010-05-30 |title=Length and Timescales of Rift Faulting and Magma Intrusion: The Afar Rifting Cycle from 2005 to Present |url=https://www.annualreviews.org/content/journals/10.1146/annurev-earth-040809-152333 |journal=Annual Review of Earth and Planetary Sciences |language=en |volume=38 |issue= |pages=439–466 |bibcode=2010AREPS..38..439E |doi=10.1146/annurev-earth-040809-152333 |issn=0084-6597|hdl=2158/1110108 |hdl-access=free }}</ref><ref name=":7" />. The faults form a complex system of [[Horst (geology)|horst]] and [[graben]]<ref>{{Cite journal |last1=Polun |first1=Sean G. |last2=Gomez |first2=Francisco |last3=Tesfaye |first3=Samson |date=2018-10-01 |title=Scaling properties of normal faults in the central Afar, Ethiopia and Djibouti: Implications for strain partitioning during the final stages of continental breakup |url=https://linkinghub.elsevier.com/retrieve/pii/S0191814118302748 |journal=Journal of Structural Geology |volume=115 |pages=178–189 |doi=10.1016/j.jsg.2018.07.018 |bibcode=2018JSG...115..178P |issn=0191-8141}}</ref><ref name=":7">{{Cite journal |last1=La Rosa |first1=Alessandro |last2=Gayrin |first2=Pauline |last3=Brune |first3=Sascha |last4=Pagli |first4=Carolina |last5=Muluneh |first5=Ameha A. |last6=Tortelli |first6=Gianmaria |last7=Keir |first7=Derek |date=2025-03-26 |title=Cross-scale strain analysis in the Afar rift (East Africa) from automatic fault mapping and geodesy |url=https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1215/ |journal=EGUsphere |language=English |pages=1–28 |doi=10.5194/egusphere-2025-1215|doi-access=free }}</ref><ref name=":6" /><ref>{{Cite journal |last=Chauvet |first=François |last2=Geoffroy |first2=Laurent |last3=Le Gall |first3=Bernard |last4=Jaud |first4=Marion |date=2023-05-01 |title=Volcanic passive margins and break-up processes in the southern Red Sea |url=https://linkinghub.elsevier.com/retrieve/pii/S1342937X23000266 |journal=Gondwana Research |volume=117 |pages=169–193 |doi=10.1016/j.gr.2023.01.004 |issn=1342-937X}}</ref> easily observable on [[Orthophoto|orthophotos]] thanks to the [[Desert|desertic environment]]. [[Igneous intrusion|Magmatic intrusions]] intrude the crust as [[Dike (geology)|dikes]] that can also erupt at the surface<ref name=":2" /><ref name=":3">{{Cite journal |last1=Ayele |first1=Atalay |last2=Keir |first2=Derek |last3=Ebinger |first3=Cynthia |last4=Wright |first4=Tim J. |last5=Stuart |first5=Graham W. |last6=Buck |first6=W. Roger |last7=Jacques |first7=Eric |last8=Ogubazghi |first8=Ghebrebrhan |last9=Sholan |first9=Jamal |date=2009 |title=September 2005 mega-dike emplacement in the Manda-Harraro nascent oceanic rift (Afar depression) |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2009GL039605 |journal=Geophysical Research Letters |language=en |volume=36 |issue=20 |doi=10.1029/2009GL039605 |bibcode=2009GeoRL..3620306A |issn=1944-8007|hdl=2158/1110101 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Keir |first1=Derek |last2=Pagli |first2=Carolina |last3=Bastow |first3=Ian D. |last4=Ayele |first4=Atalay |date=2011 |title=The magma-assisted removal of Arabia in Afar: Evidence from dike injection in the Ethiopian rift captured using InSAR and seismicity |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2010TC002785 |journal=Tectonics |language=en |volume=30 |issue=2 |doi=10.1029/2010TC002785 |bibcode=2011Tecto..30.2008K |issn=1944-9194|hdl=11568/500499 |hdl-access=free }}</ref>. Both processes cause important [[Earthquake|earthquakes]] reaching magnitude 6<ref>{{Cite journal |last=Hofstetter |first=R. |last2=Beyth |first2=M. |date=2003-11-01 |title=The Afar Depression: interpretation of the 1960–2000 earthquakes |url=https://academic.oup.com/gji/article/155/2/715/599878 |journal=Geophysical Journal International |volume=155 |issue=2 |pages=715–732 |doi=10.1046/j.1365-246X.2003.02080.x |issn=0956-540X}}</ref> and having devastating consequences for the local population <ref>{{Cite book |last=Gouin |first=P |title=Earthquake History of Ethiopia and the Horn of Africa |date=1979 |publisher=IDRC |location=Ottawa, ON, CA}}</ref>. In 2005, an important magmatic and tectonic crisis in [[Dabbahu Volcano|Dabbahu]] caused up to 8 meters of extension along a 60 km rift segment and the [[Igneous intrusion|intrusion]] of 2.5 km<sup>3</sup> of lava in only two weeks<ref>{{Cite journal |last1=Wright |first1=Tim J. |last2=Ebinger |first2=Cindy |last3=Biggs |first3=Juliet |last4=Ayele |first4=Atalay |last5=Yirgu |first5=Gezahegn |last6=Keir |first6=Derek |last7=Stork |first7=Anna |date=July 2006 |title=Magma-maintained rift segmentation at continental rupture in the 2005 Afar dyking episode |url=https://www.nature.com/articles/nature04978 |journal=Nature |language=en |volume=442 |issue=7100 |pages=291–294 |doi=10.1038/nature04978 |pmid=16855588 |bibcode=2006Natur.442..291W |hdl=2158/1078052 |issn=1476-4687|hdl-access=free }}</ref><ref name=":2" /><ref name=":3" />. Accounting for an extension rate of approx. 20 mm/yr in the area, 8 m of extension corresponds to the release of 400 years of [[Stress (mechanics)|stress]] accumulation in the [[Crust (geology)|crust]].  
[[Volcanism|Volcanic]] and [[Tectonics|tectonic]] activity is still very strong in the Depression. In different regions of the Afar, the extension is accommodated by [[Fault (geology)|faulting]] or [[Igneous intrusion|magmatic intrusions]].<ref name=":2">{{Cite journal |last1=Ebinger |first1=Cynthia |last2=Ayele |first2=Atalay |last3=Keir |first3=Derek |last4=Rowland |first4=Julie |last5=Yirgu |first5=Gezahegn |last6=Wright |first6=Tim |last7=Belachew |first7=Manahloh |last8=Hamling |first8=Ian |date=2010-05-30 |title=Length and Timescales of Rift Faulting and Magma Intrusion: The Afar Rifting Cycle from 2005 to Present |url=https://www.annualreviews.org/content/journals/10.1146/annurev-earth-040809-152333 |journal=Annual Review of Earth and Planetary Sciences |language=en |volume=38 |issue= |pages=439–466 |bibcode=2010AREPS..38..439E |doi=10.1146/annurev-earth-040809-152333 |issn=0084-6597|hdl=2158/1110108 |hdl-access=free }}</ref><ref name=":7" /> The faults form a complex system of [[Horst (geology)|horst]] and [[graben]]<ref>{{Cite journal |last1=Polun |first1=Sean G. |last2=Gomez |first2=Francisco |last3=Tesfaye |first3=Samson |date=2018-10-01 |title=Scaling properties of normal faults in the central Afar, Ethiopia and Djibouti: Implications for strain partitioning during the final stages of continental breakup |url=https://linkinghub.elsevier.com/retrieve/pii/S0191814118302748 |journal=Journal of Structural Geology |volume=115 |pages=178–189 |doi=10.1016/j.jsg.2018.07.018 |bibcode=2018JSG...115..178P |issn=0191-8141|url-access=subscription }}</ref><ref name=":7">{{Cite journal |last1=La Rosa |first1=Alessandro |last2=Gayrin |first2=Pauline |last3=Brune |first3=Sascha |last4=Pagli |first4=Carolina |last5=Muluneh |first5=Ameha A. |last6=Tortelli |first6=Gianmaria |last7=Keir |first7=Derek |date=2025-03-26 |title=Cross-scale strain analysis in the Afar rift (East Africa) from automatic fault mapping and geodesy |url=https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1215/ |journal=EGUsphere |language=English |pages=1–28 |doi=10.5194/egusphere-2025-1215|doi-access=free }}</ref><ref name=":6" /><ref>{{Cite journal |last=Chauvet |first=François |last2=Geoffroy |first2=Laurent |last3=Le Gall |first3=Bernard |last4=Jaud |first4=Marion |date=2023-05-01 |title=Volcanic passive margins and break-up processes in the southern Red Sea |url=https://linkinghub.elsevier.com/retrieve/pii/S1342937X23000266 |journal=Gondwana Research |volume=117 |pages=169–193 |doi=10.1016/j.gr.2023.01.004 |issn=1342-937X}}</ref> easily observable on [[Orthophoto|orthophotos]] thanks to the [[Desert|desertic environment]]. [[Igneous intrusion|Magmatic intrusions]] intrude the crust as [[Dike (geology)|dikes]] that can also erupt at the surface.<ref name=":2" /><ref name=":3">{{Cite journal |last1=Ayele |first1=Atalay |last2=Keir |first2=Derek |last3=Ebinger |first3=Cynthia |last4=Wright |first4=Tim J. |last5=Stuart |first5=Graham W. |last6=Buck |first6=W. Roger |last7=Jacques |first7=Eric |last8=Ogubazghi |first8=Ghebrebrhan |last9=Sholan |first9=Jamal |date=2009 |title=September 2005 mega-dike emplacement in the Manda-Harraro nascent oceanic rift (Afar depression) |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2009GL039605 |journal=Geophysical Research Letters |language=en |volume=36 |issue=20 |doi=10.1029/2009GL039605 |bibcode=2009GeoRL..3620306A |issn=1944-8007|hdl=2158/1110101 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Keir |first1=Derek |last2=Pagli |first2=Carolina |last3=Bastow |first3=Ian D. |last4=Ayele |first4=Atalay |date=2011 |title=The magma-assisted removal of Arabia in Afar: Evidence from dike injection in the Ethiopian rift captured using InSAR and seismicity |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2010TC002785 |journal=Tectonics |language=en |volume=30 |issue=2 |doi=10.1029/2010TC002785 |bibcode=2011Tecto..30.2008K |issn=1944-9194|hdl=11568/500499 |hdl-access=free }}</ref> Both processes cause important [[Earthquake|earthquakes]] reaching magnitude 6<ref>{{Cite journal |last=Hofstetter |first=R. |last2=Beyth |first2=M. |date=2003-11-01 |title=The Afar Depression: interpretation of the 1960–2000 earthquakes |url=https://academic.oup.com/gji/article/155/2/715/599878 |journal=Geophysical Journal International |volume=155 |issue=2 |pages=715–732 |doi=10.1046/j.1365-246X.2003.02080.x |issn=0956-540X}}</ref> and having devastating consequences for the local population.<ref>{{Cite book |last=Gouin |first=P |title=Earthquake History of Ethiopia and the Horn of Africa |date=1979 |publisher=IDRC |location=Ottawa, ON, CA}}</ref> In 2005, an important magmatic and tectonic crisis in [[Dabbahu Volcano|Dabbahu]] caused up to 8 meters of extension along a 60 km rift segment and the [[Igneous intrusion|intrusion]] of 2.5 km<sup>3</sup> of lava in only two weeks.<ref>{{Cite journal |last1=Wright |first1=Tim J. |last2=Ebinger |first2=Cindy |last3=Biggs |first3=Juliet |last4=Ayele |first4=Atalay |last5=Yirgu |first5=Gezahegn |last6=Keir |first6=Derek |last7=Stork |first7=Anna |date=July 2006 |title=Magma-maintained rift segmentation at continental rupture in the 2005 Afar dyking episode |url=https://www.nature.com/articles/nature04978 |journal=Nature |language=en |volume=442 |issue=7100 |pages=291–294 |doi=10.1038/nature04978 |pmid=16855588 |bibcode=2006Natur.442..291W |hdl=2158/1078052 |issn=1476-4687|hdl-access=free }}</ref><ref name=":2" /><ref name=":3" /> Accounting for an extension rate of approx. 20 mm/yr in the area, 8 m of extension corresponds to the release of 400 years of [[Stress (mechanics)|stress]] accumulation in the [[Crust (geology)|crust]].  


In the northern part of the Afar Depression, called the [[Danakil Depression]], the volcanic activity was less intense until approx. 0.6 My ago<ref name=":0" />. This allowed the crust to thin more than the central part of the Afar and the topography to reach elevations below sea level.<ref name=":0" /> This allowed the Red Sea to invade the Danakil Depression during at least four [[Interglacial|periods of high sea-level]] in the [[Pleistocene]].<ref name=":4">{{Cite journal |last1=Jaramillo-Vogel |first1=David |last2=Foubert |first2=Anneleen |last3=Braga |first3=Juan Carlos |last4=Schaegis |first4=Jean-Charles |last5=Atnafu |first5=Balemwal |last6=Grobety |first6=Bernard |last7=Kidane |first7=Tesfaye |date=2019 |title=Pleistocene sea-floor fibrous crusts and spherulites in the Danakil Depression (Afar, Ethiopia) |url=https://onlinelibrary.wiley.com/doi/10.1111/sed.12484 |journal=Sedimentology |language=en |volume=66 |issue=2 |pages=480–512 |doi=10.1111/sed.12484 |bibcode=2019Sedim..66..480J |issn=1365-3091}}</ref><ref name=":5">{{Cite journal |last1=Foubert |first1=Anneleen |last2=Keir |first2=Derek |last3=Atnafu |first3=Balemwal |last4=Kidane |first4=Tesfaye |last5=the ADD-ON Workshop Consortium |date=2024-08-30 |title=Workshop report: Afar Dallol Drilling – ONset of sedimentary processes in an active rift basin (ADD-ON) |url=https://sd.copernicus.org/articles/33/207/2024/ |journal=Scientific Drilling |language=English |volume=33 |issue=2 |pages=207–218 |doi=10.5194/sd-33-207-2024 |doi-access=free |bibcode=2024SciDr..33..207F |issn=1816-8957|hdl=20.500.11850/693510 |hdl-access=free }}</ref> The last flooding happened approx. 130'000 years ago.<ref name=":4" /><ref name=":5" /> These flooding are testified by fossil [[Coral reef|coral reefs]]<ref name=":4" /><ref name=":5" /> and by thick (>500 m) [[Evaporite|evaporites]] deposits (mainly [[halite]], i.e. [[salt]]) found in the central part of the basin.<ref>{{Cite journal |last1=Holwerda |first1=James G. |last2=Hutchinson |first2=Richard W. |date=1968-03-01 |title=Potash-bearing evaporites in the Danakil area, Ethiopia |url=http://pubs.geoscienceworld.org/economicgeology/article/63/2/124/17788/Potashbearing-evaporites-in-the-Danakil-area |journal=Economic Geology |language=en |volume=63 |issue=2 |pages=124–150 |doi=10.2113/gsecongeo.63.2.124 |bibcode=1968EcGeo..63..124H |issn=1554-0774}}</ref><ref>{{Cite journal |last1=Rime |first1=Valentin |last2=Negga |first2=Haileyesus |last3=Fentimen |first3=Robin |last4=Rüggeberg |first4=Andres |last5=El Korh |first5=Afifé |last6=Pirkenseer |first6=Claudius |last7=Schaegis |first7=Jean-Charles |last8=Hajdas |first8=Irka |last9=Adatte |first9=Thierry |last10=Atnafu |first10=Balemwal |last11=Kidane |first11=Tesfaye |last12=Foubert |first12=Anneleen |date=2025 |title=Nature and significance of Late Pleistocene to Holocene thick evaporite deposits of the Danakil Depression, Afar, Ethiopia |url=https://onlinelibrary.wiley.com/doi/10.1111/sed.13237 |journal=Sedimentology |language=en |volume=72 |issue=2 |pages=475–506 |doi=10.1111/sed.13237 |bibcode=2025Sedim..72..475R |issn=1365-3091}}</ref>  
In the northern part of the Afar Depression, called the [[Danakil Depression]], the volcanic activity was less intense until approx. 0.6 My ago.<ref name=":0" /> This allowed the crust to thin more than the central part of the Afar and the topography to reach elevations below sea level.<ref name=":0" /> This allowed the Red Sea to invade the Danakil Depression during at least four [[Interglacial|periods of high sea-level]] in the [[Pleistocene]].<ref name=":4">{{Cite journal |last1=Jaramillo-Vogel |first1=David |last2=Foubert |first2=Anneleen |last3=Braga |first3=Juan Carlos |last4=Schaegis |first4=Jean-Charles |last5=Atnafu |first5=Balemwal |last6=Grobety |first6=Bernard |last7=Kidane |first7=Tesfaye |date=2019 |title=Pleistocene sea-floor fibrous crusts and spherulites in the Danakil Depression (Afar, Ethiopia) |url=https://onlinelibrary.wiley.com/doi/10.1111/sed.12484 |journal=Sedimentology |language=en |volume=66 |issue=2 |pages=480–512 |doi=10.1111/sed.12484 |bibcode=2019Sedim..66..480J |issn=1365-3091|url-access=subscription }}</ref><ref name=":5">{{Cite journal |last1=Foubert |first1=Anneleen |last2=Keir |first2=Derek |last3=Atnafu |first3=Balemwal |last4=Kidane |first4=Tesfaye |last5=the ADD-ON Workshop Consortium |date=2024-08-30 |title=Workshop report: Afar Dallol Drilling – ONset of sedimentary processes in an active rift basin (ADD-ON) |url=https://sd.copernicus.org/articles/33/207/2024/ |journal=Scientific Drilling |language=English |volume=33 |issue=2 |pages=207–218 |doi=10.5194/sd-33-207-2024 |doi-access=free |bibcode=2024SciDr..33..207F |issn=1816-8957|hdl=20.500.11850/693510 |hdl-access=free }}</ref> The last flooding happened approx. 130'000 years ago.<ref name=":4" /><ref name=":5" /> These flooding are testified by fossil [[Coral reef|coral reefs]]<ref name=":4" /><ref name=":5" /> and by thick (>500 m) [[Evaporite|evaporites]] deposits (mainly [[halite]], i.e. [[salt]]) found in the central part of the basin.<ref>{{Cite journal |last1=Holwerda |first1=James G. |last2=Hutchinson |first2=Richard W. |date=1968-03-01 |title=Potash-bearing evaporites in the Danakil area, Ethiopia |url=http://pubs.geoscienceworld.org/economicgeology/article/63/2/124/17788/Potashbearing-evaporites-in-the-Danakil-area |journal=Economic Geology |language=en |volume=63 |issue=2 |pages=124–150 |doi=10.2113/gsecongeo.63.2.124 |bibcode=1968EcGeo..63..124H |issn=1554-0774}}</ref><ref>{{Cite journal |last1=Rime |first1=Valentin |last2=Negga |first2=Haileyesus |last3=Fentimen |first3=Robin |last4=Rüggeberg |first4=Andres |last5=El Korh |first5=Afifé |last6=Pirkenseer |first6=Claudius |last7=Schaegis |first7=Jean-Charles |last8=Hajdas |first8=Irka |last9=Adatte |first9=Thierry |last10=Atnafu |first10=Balemwal |last11=Kidane |first11=Tesfaye |last12=Foubert |first12=Anneleen |date=2025 |title=Nature and significance of Late Pleistocene to Holocene thick evaporite deposits of the Danakil Depression, Afar, Ethiopia |url=https://onlinelibrary.wiley.com/doi/10.1111/sed.13237 |journal=Sedimentology |language=en |volume=72 |issue=2 |pages=475–506 |doi=10.1111/sed.13237 |bibcode=2025Sedim..72..475R |issn=1365-3091}}</ref>  


Geologists predict that in about 10 million years the whole {{Convert|6000|km|mi|abbr=on|sp=us|sigfig=2}} length of the East African Rift will be submerged, forming a new [[Oceanic basin|ocean basin]] as large as today's Red Sea, and separating the [[Somali plate]] and the [[Horn of Africa]] from the rest of the continent.<ref>{{cite news | first=Axel | last=Bojanowski | title=Africa's New Ocean: A Continent Splits Apart | date=2006-03-15 | publisher=Spiegel Online | url = http://www.spiegel.de/international/spiegel/0,1518,405947,00.html | access-date=2006-03-16 }} Includes a photo essay of the region and its geologic changes.
Geologists predict that in about 10 million years the whole {{Convert|6000|km|mi|abbr=on|sp=us|sigfig=2}} length of the East African Rift will be submerged, forming a new [[Oceanic basin|ocean basin]] as large as today's Red Sea, and separating the [[Somali plate]] and the [[Horn of Africa]] from the rest of the continent.<ref>{{cite news | first=Axel | last=Bojanowski | title=Africa's New Ocean: A Continent Splits Apart | date=2006-03-15 | publisher=Spiegel Online | url = http://www.spiegel.de/international/spiegel/0,1518,405947,00.html | access-date=2006-03-16 }} Includes a photo essay of the region and its geologic changes.
Line 54: Line 54:
*The {{annotated link|Afar people}} who inhabit the region
*The {{annotated link|Afar people}} who inhabit the region


== References ==
==References==
=== Citations ===
===Citations===
{{Reflist}}
{{Reflist}}


=== Sources ===
===Sources===
{{Refbegin}}
{{Refbegin}}
* {{Cite journal |last1=Barberi |first1=F. |last2=Borsi |first2=S. |last3=Ferrara |first3=G. |last4=Marinelli |first4=G. |last5=Santacroce |first5=R. |last6=Tazieff |first6=H. |last7=Varet |first7=J. |title=Evolution of the Danakil Depression (Afar, Ethiopia) in Light of Radiometric Age Determinations |journal=Journal of Geology |volume=80 |issue=6 |year=1972 |pages=720–729 |doi=10.1086/627797 |bibcode=1972JG.....80..720B|s2cid=128757919 }}
*{{Cite journal |last1=Barberi |first1=F. |last2=Borsi |first2=S. |last3=Ferrara |first3=G. |last4=Marinelli |first4=G. |last5=Santacroce |first5=R. |last6=Tazieff |first6=H. |last7=Varet |first7=J. |title=Evolution of the Danakil Depression (Afar, Ethiopia) in Light of Radiometric Age Determinations |journal=Journal of Geology |volume=80 |issue=6 |year=1972 |pages=720–729 |doi=10.1086/627797 |bibcode=1972JG.....80..720B|s2cid=128757919 }}
*{{cite news | first=Axel | last=Bojanowski | title=Africa's New Ocean: A Continent Splits Apart | date=2006-03-15 | publisher=Spiegel Online | url = http://www.spiegel.de/international/spiegel/0,1518,405947,00.html | access-date=2006-03-16 }} Includes a photo essay of the region and its geologic changes.
*{{cite news | first=Axel | last=Bojanowski | title=Africa's New Ocean: A Continent Splits Apart | date=2006-03-15 | publisher=Spiegel Online | url = http://www.spiegel.de/international/spiegel/0,1518,405947,00.html | access-date=2006-03-16 }} Includes a photo essay of the region and its geologic changes.
*{{Cite journal |last=Kloos |first=Helmut |year=1982 |title=Development, drought and famine in the Awash valley of Ethiopia |jstor=524399 |journal=[[African Studies Review]] |volume=25 |issue=4 |pages=21–48 |doi = 10.2307/524399 }}
*{{Cite journal |last=Kloos |first=Helmut |year=1982 |title=Development, drought and famine in the Awash valley of Ethiopia |jstor=524399 |journal=[[African Studies Review]] |volume=25 |issue=4 |pages=21–48 |doi = 10.2307/524399 }}
* {{WWF ecoregion|name=Ethiopian xeric grasslands and shrublands|id=at1305}}
*{{WWF ecoregion|name=Ethiopian xeric grasslands and shrublands|id=at1305}}
* Jon Kalb: ''Adventures in the Bone Trade. The Race to Discover Human Ancestors in Ethiopia's Afar Depression.'' Copernicus Books, New York 2001, {{ISBN|0-387-98742-8 }}
*Jon Kalb: ''Adventures in the Bone Trade. The Race to Discover Human Ancestors in Ethiopia's Afar Depression.'' Copernicus Books, New York 2001, {{ISBN|0-387-98742-8 }}
* {{cite book |last1=Jeangene Vilmer |first1=Jean-Baptiste |last2=Gouery |first2=Franck |title=Les Afars d'Éthiopie. Dans l'enfer du Danakil |url = http://www.afars-danakil.fr |year=2011 |publisher=Non lieu |isbn=9782352701088 |url-status=dead |archive-url = https://web.archive.org/web/20130731230922/http://www.afars-danakil.fr/ |archive-date=2013-07-31 }}
*{{cite book |last1=Jeangene Vilmer |first1=Jean-Baptiste |last2=Gouery |first2=Franck |title=Les Afars d'Éthiopie. Dans l'enfer du Danakil |url = http://www.afars-danakil.fr |year=2011 |publisher=Non lieu |isbn=9782352701088 |url-status=dead |archive-url = https://web.archive.org/web/20130731230922/http://www.afars-danakil.fr/ |archive-date=2013-07-31 }}
{{Refend}}
{{Refend}}


Latest revision as of 08:09, 29 June 2025

Template:Short description

File:Topographic30deg N0E30.png
Topographic map showing the Afar Triangle

The Afar Triangle (also called the Afar Depression) is a geological depression caused by the Afar triple junction, which is part of the Great Rift Valley in East Africa. The region has disclosed fossil specimens of the very earliest hominins; that is, the earliest of the human clade, and it is thought by some paleontologists to be the cradle of the evolution of humans. The Depression overlaps the borders of Eritrea, Djibouti and the entire Afar Region of Ethiopia; and it contains the lowest point in Africa, Lake Assal, Djibouti, at Template:Convert below sea level.

The Awash River is the main waterflow into the region, but it runs dry during the annual dry season, and ends as a chain of saline lakes. The northern part of the Afar Depression is also known as the Danakil Depression. The lowlands are affected by heat, drought, and minimal air circulation, and contain the hottest places (year-round average temperatures) of anywhere on Earth.

The Afar Triangle is bordered as follows (see the topographic map): on the west by the Ethiopian Plateau and escarpment; to the north-east (between it and the Red Sea) by the Danakil block; to the south by the Somali Plateau and escarpment; and to the south-east by the Ali-Sabieh block (adjoining the Somali Plateau).[1]

Many important fossil localities exist in the Afar region, including the Middle Awash region and the sites of Hadar, Dikika, and Woranso-Mille. These sites have produced specimens of the earliest (fossil) hominins and of human tool culture, as well as many fossils of various flora and fauna.

Environment

File:AFAR-MODIS.jpg
Moderate Resolution Imaging Spectroradiometer satellite image of the Afar Depression and surrounding regions of the Red Sea, Gulf of Aden, Arabia, and the Horn of Africa

Dallol in the Danakil Depression is one of the hottest places year-round anywhere on Earth. There is no rain for most of the year; the yearly rainfall averages range from Template:Convert, with even less rain falling closer to the coast. Daily mean temperatures at Dallol ranged from Template:Convert in January to Template:Convert in July in six years of observations from 1960 to 1966.

File:AfarDrape.jpg
Perspective view of the Afar Depression and environs, generated by draping a Landsat image over a digital elevation model.

The Awash River, flowing north-eastward through the southern part of the Afar Region, provides a narrow green belt which enables life for the flora and fauna in the area and for the Afars, the nomadic people living in the Danakil Desert. About Template:Convert from the Red Sea the Awash ends in a chain of salt lakes, where its waterflow evaporates as quickly as it is supplied. Some Template:Convert of the Afar Depression is covered by salt deposits, and mining salt is a major source of income for many Afar groups.

The Afar Depression biome is characterized as desert scrubland. Vegetation is mostly confined to drought-resistant plants such as small trees (e.g. species of the dragon tree), shrubs, and grasses. Wildlife includes many herbivores such as Grévy's zebra, Soemmerring's gazelle, beisa and, notably, the last viable population of African wild ass (Equus africanus somalicus).

Birds include the ostrich, the endemic Archer's lark, the secretary bird, Arabian and Kori bustards, Abyssinian roller, and crested francolin. In the southern part of the plain lies the Mille-Serdo Wildlife Reserve.

The Afar Triangle is a cradle source of the earliest hominins. It contains a paleo-archaeological district that includes the Middle Awash region and numerous prehistoric sites of fossil hominin discoveries, including: the hominids and possible hominins, Ardi, or Ardipithecus ramidus, and Ardipithecus kadabba, see below; the Gawis cranium hominin from Gona; several sites of the world's oldest stone tools; Hadar, the site of Lucy, the fossilized specimen of Australopithecus afarensis; and Dikika, the site of the fossilized child Selam, an australopithecine hominin.[2]

In 1994, near the Awash River in Ethiopia, Tim D. White found the then-oldest known human ancestor: 4.4 million-year-old Ar. ramidus. A fossilized almost complete skeleton of a female hominin which he named "Ardi", it took nearly 15 years to safely excavate, preserve, and describe the specimen and to prepare publication of the event.[3]

Geology

File:Tectonic African Arabian Rift System.jpg
Tectonic map of the African-Arabian Rift System. The Afar Depression is situated at the junction of the Red Sea, the Gulf of Aden, and the East African Rift System
File:Tectonic map of the Afar Depression.jpg
Tectonic map of the Afar Depression showing the small scale plate configuration, the velocities of extension and the active rift segments.
File:Geological map of the Afar Depression.jpg
Geological map of the Afar Depression showing the magmatic rocks from old (yellow) to recent (dark red), as well as the fault pattern.

The Afar Depression is a tectonic triple junction (the Afar triple junction), where the spreading ridges of the Red Sea and the Gulf of Aden meet the East African Rift. These rifts are caused by the northeastward movement of the Arabian plate (approximately 20 mm/yr[4]) and the much slower eastward movement of the Somalian plate (approximately 5 mm/yr[5]) relative to the Nubian (African) plate.

At smaller scale, the tectonics of the Afar Depression is more complex. An independent microplate, the Danakil (or Arrata) microplate, is carrying a piece of continental material (the Danakil block) between the Afar and the Red Sea and is rotating counterclockwise,[6][7][8] causing the slow propagation of the Afar Rift to the north and the propagation of the Red Sea rift to the south.[8]

The recent geological history of the Afar Depression started around 33 million years ago, before any rifting, with the eruption of the Ethiopian Flood Basalts that covered large parts of Ethiopia and Yemen with hundreds to thousands of meters of volcanic rocks.[9][10][11][12][13] These eruptions were cause by a hot rising mantle plume that impacted the continental crust and produced large quantities of magma.[14][15][16][17] This impact of the mantle plume also caused the high topography of the region,[18][19] an effect still visible today.

This volcanic activity weakened the crust and allowed the beginning of the separation between the Arabian plate and the Nubian plate.[20][21] The Gulf of Aden rift propagated westwards and rifting started in the Afar region approximately 28 million years ago, at the same time as in the southern Red Sea.[8] Between 13 and 8 Ma, a major reorganization of the region took place.[8] The Danakil microplate started rotating, causing the secession of tectonic activity in the southernmost Red Sea, and propagation of the Afar rift in the Danakil Depression (i.e. the northern part of the Afar Triangle).[8] At the same time, the Main Ethiopian Rift (the northernmost part of the East African Rift System) started to form and the Afar Depression became a triple junction.[22] This movement in three different directions by three major plates caused extension and thinning of the crust, explaining the general morphology of the Afar Depression.

During the extension, volcanism remained very important in the Depression, with kilometers of volcanic rocks dominated by basalts emplaced in central Afar.[6][23][24] So much magmatic rocks were added to crust, at the surface as lava flows, but also in the crust as intrusions and below the crust as underplated material, that it did not thin as much as expected.[8][25][26] This phenomenon is called magma-compensated thinning[27] and it can explain why the central Afar is the only part of the Gulf of Aden - Red Sea system that do not feature normal oceanic crust.[8][25] Because of this high volcanic activity, some researchers propose that this region might never form a normal ocean, but instead form an oceanic plateau, similar to Iceland.[25]

File:Graben Afar ASTER 20020327.jpg
Satellite image of a graben in the Afar Depression.

Volcanic and tectonic activity is still very strong in the Depression. In different regions of the Afar, the extension is accommodated by faulting or magmatic intrusions.[28][29] The faults form a complex system of horst and graben[30][29][26][31] easily observable on orthophotos thanks to the desertic environment. Magmatic intrusions intrude the crust as dikes that can also erupt at the surface.[28][32][33] Both processes cause important earthquakes reaching magnitude 6[34] and having devastating consequences for the local population.[35] In 2005, an important magmatic and tectonic crisis in Dabbahu caused up to 8 meters of extension along a 60 km rift segment and the intrusion of 2.5 km3 of lava in only two weeks.[36][28][32] Accounting for an extension rate of approx. 20 mm/yr in the area, 8 m of extension corresponds to the release of 400 years of stress accumulation in the crust.

In the northern part of the Afar Depression, called the Danakil Depression, the volcanic activity was less intense until approx. 0.6 My ago.[8] This allowed the crust to thin more than the central part of the Afar and the topography to reach elevations below sea level.[8] This allowed the Red Sea to invade the Danakil Depression during at least four periods of high sea-level in the Pleistocene.[37][38] The last flooding happened approx. 130'000 years ago.[37][38] These flooding are testified by fossil coral reefs[37][38] and by thick (>500 m) evaporites deposits (mainly halite, i.e. salt) found in the central part of the basin.[39][40]

Geologists predict that in about 10 million years the whole Template:Convert length of the East African Rift will be submerged, forming a new ocean basin as large as today's Red Sea, and separating the Somali plate and the Horn of Africa from the rest of the continent.[41]

See also

References

Citations

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Sources

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  • Script error: No such module "Citation/CS1".
  • Script error: No such module "citation/CS1". Includes a photo essay of the region and its geologic changes.
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  • Template:WWF ecoregion
  • Jon Kalb: Adventures in the Bone Trade. The Race to Discover Human Ancestors in Ethiopia's Afar Depression. Copernicus Books, New York 2001, Template:ISBN
  • Script error: No such module "citation/CS1".

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External links

Template:Major African geological formations Template:Regions of Africa Template:Authority control

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  25. ↑ a b c Script error: No such module "Citation/CS1".
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  28. ↑ a b c Script error: No such module "Citation/CS1".
  29. ↑ a b Script error: No such module "Citation/CS1".
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  38. ↑ a b c Script error: No such module "Citation/CS1".
  39. ↑ Script error: No such module "Citation/CS1".
  40. ↑ Script error: No such module "Citation/CS1".
  41. ↑ Script error: No such module "citation/CS1". Includes a photo essay of the region and its geologic changes.
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