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The Zanclean flood or Zanclean Deluge is a flood theorized to have refilled the Mediterranean
Mediterranean
Sea 5.33 million years ago.[1] This flooding ended the Messinian salinity crisis
Messinian salinity crisis
and reconnected the Mediterranean
Mediterranean
Sea to the Atlantic Ocean, although it is possible that even before the flood there were partial connections to the Atlantic Ocean. The reconnection marks the beginning of the Zanclean age. According to this model, water from the Atlantic Ocean
Atlantic Ocean
refilled the dried up basin through the modern-day Strait of Gibraltar. The Mediterranean
Mediterranean
Basin flooded mostly during a period estimated to have been between several months and two years.[2][3] Sea level rise
Sea level rise
in the basin may have reached rates at times greater than ten metres per day (thirty feet per day).[2] Based on the erosion features preserved until modern times under the Pliocene
Pliocene
sediment, Garcia-Castellanos et al. estimate that water rushed down a drop of more than 1 kilometre (0.62 mi) with a discharge of up to 2×108 m3/s (7.1×109 cu ft/s), about 1,000 times that of the present day Amazon River.[2] Studies of the underground structures at the Gibraltar Strait
Gibraltar Strait
show that the flooding channel descended in a rather gradual way toward the bottom of the basin rather than forming a steep waterfall. Not all scientific studies have agreed with the catastrophist interpretation of this event. Some researchers have estimated that the reinstallment of a "normal" Mediterranean
Mediterranean
Sea basin following the Messinian
Messinian
"Lago Mare" episode took place in a much more gradual way, taking as long as 10,000 years.[4]

Contents

1 Background 2 Event

2.1 Timing

3 Consequences 4 Similar megafloods 5 See also 6 Notes and references

6.1 Notes 6.2 References 6.3 Sources

7 External links

Background[edit] The geologic history of the Mediterranean
Mediterranean
is governed by plate tectonics involving the African Plate, the Arabian Plate
Arabian Plate
and the Eurasian Plate
Eurasian Plate
which shrank the previously existing Tethys until its western part became the present-day Mediterranean.[5] For reasons not clearly established, during the latest Miocene
Miocene
the Mediterranean
Mediterranean
was severed from the Atlantic Ocean
Atlantic Ocean
and partly dried up when the Guadalhorce
Guadalhorce
and Rifian corridors that had previously connected the Mediterranean
Mediterranean
to the Atlantic closed,[6] triggering the Messinian Salinity Crisis with the formation of thick salt deposits on the former seafloor[7] and erosion of the continental slopes.[8] The Nile and Rhone
Rhone
carved deep canyons during this time.[9] Water levels in the Mediterranean
Mediterranean
during this time dropped by kilometres;[10] the exact magnitude of the drop and whether it was symmetric between the Western Mediterranean
Mediterranean
and the Eastern Mediterranean
Mediterranean
is unclear;[11] it is possible that interconnected seas remained on the floor of the Mediterranean.[12] The presence of Atlantic fish in Messinian
Messinian
deposits[12] and the volume of salt deposited during the Messinian Salinity Crisis
Messinian Salinity Crisis
implies that there was some remnant flow from the Atlantic into the Mediterranean even before the Zanclean flood.[6] Already before the Zanclean flood, increased precipitation and runoff had lowered the salinity of the remnant sea,[7] with some water putatively originating in the Paratethys
Paratethys
north of the Mediterranean.[13] Event[edit] The Zanclean flood occurred when the Strait of Gibraltar
Strait of Gibraltar
opened.[14] Tectonic subsidence of the Gibraltar region may have lowered the sill until it breached.[7] The exact triggering event is not known with certainty; faulting or sea level rise are debatable. The most widely accepted hypothesis is that a stream flowing into the Mediterranean eroded through the Strait of Gibraltar
Strait of Gibraltar
until it captured the Atlantic Ocean[10] and that the Strait did not exist before this erosion event.[15] During the flood, a channel formed across the Strait of Gibraltar,[14] which starts at the Camarinal Sill in the Strait of Gibraltar,[16] splits around the Vizconde de Eza high of the Alboran Sea[17] and eventually connects with the Alboran Channel before splitting into several branches that end in the Algero-Balear basin.[16][18] The channel has an U-like shape in its starting region, which is consistent with its formation during a giant flood.[19] The sector of the Zanclean channel that passes through the Camarinal Sill may have a different origin, however.[11] Whether the Zanclean flood occurred gradually or as a catastrophic event is controversial.[20] The magnitude of a catastrophic flood has been simulated by modelling. One single-dimensional model assumes a catastrophic flood of more than 10–100 sverdrup.[note 1] Another estimate assumes that after the first breach of the sill, the flowing water eroded the threshold and forming the channel across the Gibraltar strait, increasing the flow of water which in turn increased the erosion until water levels rose enough in the Mediterranean
Mediterranean
to slow the flood.[19] Under such a scenario, a peak discharge of over 100,000,000 cubic metres per second (3.5×109 cu ft/s) occurred with water velocities of over 40 metres per second (130 ft/s); such flow rates are about a thousand times larger than the discharge of the Amazon River
Amazon River
and ten times as much as the Missoula Floods.[23] This flood would have descended a relatively gentle ramp into the Mediterranean
Mediterranean
basin, not as a giant waterfall.[24] Later simulations using more explicit geography constrain the flow to about 100 Sverdrup, which is about 100,000,000 cubic metres per second (3.5×109 cu ft/s). They further indicate the formation of large gyres in the Alboran Sea
Alboran Sea
during the flooding[21] and that the flood eroded the Camarinal Sill at a rate of 0.4–0.7 metres per day (1.3–2.3 ft/d).[25] The exact size of the flood is dependent on the pre-flood water levels in the Mediterranean
Mediterranean
and higher water levels there would result in a much smaller flood.[26] The flood affected only the Western Mediterranean
Mediterranean
at first, because the Sicily Sill (located at the present Straits of Sicily) formed a barrier separating its basin from the Eastern Mediterranean
Mediterranean
basin;[27] in addition a sill may have existed in the eastern Alboran Sea
Alboran Sea
at this time.[28] While it was at first assumed that the filling of the eastern Mediterranean
Mediterranean
would have taken thousands of years, later estimates of the size of the Strait of Gibraltar
Strait of Gibraltar
channel implied that it would have taken much less, potentially less than a year until reconnection.[29] A 2018 study suggested that the Mediterranean reversed water losses in around two years.[30] A large flood is not the only explanation for the reconnection of the Mediterranean
Mediterranean
with the Atlantic and concomitant environmental changes; more gradual reflooding of the Mediterranean
Mediterranean
including reflooding through other water sources is also possible.[31][32] The absence of a catastrophic flooding event is supported by geological evidence found along the southern margin of the Alboran Sea.[33] A January 2018 study by scientists from the University of Malta, published in the journal Scientific Reports, however, presented geological evidence that the catastrophic megaflood was indeed responsible. The study, led by geoscientist Aaron Micallef, used seafloor data from between Sicily's eastern coast and Malta
Malta
to identify a body of sediment which Micallef and his colleagues believe to have been pushed eastwards as the opening of the Strait of Gibraltar caused a massive amount of water to flow from the Atlantic. The collection of sediment Micallef and his colleagues observed was 160 kilometres long, 95 kilometres wide, and as much as 900 metres deep in some areas, abutting an underwater limestone cliff known as the Malta
Malta
Escarpment.[30][34][35] Timing[edit] The timing of the Zanclean flood is uncertain, with one possibility being a flood around 5.33 million years ago;[36] the end of the Messinian/ Miocene
Miocene
and beginning of the Zanclean/ Pliocene
Pliocene
is usually associated with the flood.[37] The main Zanclean flood may have been preceded by an earlier smaller flood event,[11][38] and the presence of deep sea terraces has been used to infer that the refilling of the Mediterranean
Mediterranean
occurred in several pulses.[39] Complete refilling of the Mediterranean
Mediterranean
may have taken about a decade.[7] Consequences[edit] The Zanclean flood created the Strait of Gibraltar; it is questionable that tectonic or volcanic events could have created the strait themselves seeing as the main plate boundaries do not run through the strait and there is little seismic activity in its area.[40] The current morphology of the strait is characterized by two sills, the maximally 284 metres (932 ft) deep Camarinal Sill and the somewhat deeper Spartel Sill[41] farther west; the narrowest part of the strait is located east of either sill,[42] and this narrowest part is considerably deeper.[41] It is possible that these sills were formed after the flood through gravity-induced movement of neighbouring terrain.[43] The Zanclean flood caused a major change in the environment of the Mediterranean
Mediterranean
basin; the continental "Lago Mare" facies was replaced by Zanclean deep sea deposits.[7] The flood may have affected global climate, considering that the much smaller flood triggered when Lake Agassiz drained did result in a cold period.[44] Rising sea levels made the deeply incised Nile
Nile
river become a ria as far inland as Aswan, 900 km from the modern mediterranean coast.[45] The Zanclean flood resulted in the final isolation of numerous Mediterranean
Mediterranean
islands such as Crete,[46] resulting in speciation of animals found there.[47] On the other hand, the formation of the Gibraltar Strait
Gibraltar Strait
prevented animals from crossing over between Africa and Europe.[48] Further the reconnection allowed sea animals such as cetaceans and their ancestors and pinnipeds to colonize the Mediterranean
Mediterranean
from the Atlantic.[49] Evidence of the flooding has been obtained on Zanclean-age sediments, both in boreholes and in sediments that were subsequently uplifted and raised above sea level.[50] A sharp erosional surface separates the pre- Zanclean flood surface from the younger deposits, which are always marine in origin.[51] The rates at which the Mediterranean
Mediterranean
filled during the flood were more than enough to trigger substantial induced seismicity.[52] Resulting large landslides would have sufficed at creating large tsunamis with waveheights reaching 100 metres (330 ft), evidence of which has been found in the Algeciras Basin.[53] Similar megafloods[edit] Similar floods have occurred elsewhere on Earth during history; examples include the Bonneville flood
Bonneville flood
in North America,[9] during which Lake Bonneville
Lake Bonneville
overflowed through Red Rock Pass
Red Rock Pass
into the Snake River Basin, as well as the Black Sea deluge hypothesis
Black Sea deluge hypothesis
that postulates a flood from the Mediterranean
Mediterranean
into the Black Sea
Black Sea
through the Bosporus.[54] See also[edit]

Lake Manych-Gudilo Outburst flood "Time" (xkcd)

Notes and references[edit] Notes[edit]

^ 1 sverdrup is 1,000,000 cubic metres per second.[21] Total outflow of all rivers is about 1.2 sverdrup.[22]

References[edit]

^ Blanc, P.-L. (2002). "The opening of the Plio-Quaternary Gibraltar Strait: assessing the size of a cataclysm". Geodinamica Acta. 15 (15): 303–317. Bibcode:2002GeoAc..15..303B. doi:10.1016/S0985-3111(02)01095-1.  ^ a b c Garcia-Castellanos, D., Estrada, F., Jiménez-Munt, I., Gorini, C., Fernàndez, M., Vergés, J., De Vicente, R. (10 December 2009) Catastrophic flood of the Mediterranean
Mediterranean
after the Messinian salinity crisis, Nature 462, pp. 778–781, doi:10.1038/nature08555 ^ M. Roveri et al. (2008). "A high-resolution stratigraphic framework for the latest Messinian
Messinian
events in the Mediterranean
Mediterranean
area" (PDF). Stratigraphy. 5 (3–4): 323–342. Archived from the original (PDF) on 21 January 2012. CS1 maint: Uses authors parameter (link) ^ Gill, Victoria (9 December 2009). "Ancient Mediterranean
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flood mystery solved". BBC News. Retrieved 5 May 2013.  ^ Cipollari et al. 2013, p. 473. ^ a b Periáñez & Abril 2015, p. 49. ^ a b c d e Cipollari et al. 2013, p. 474. ^ Just et al. 2011, p. 51. ^ a b Garcia-Castellanos et al. 2009, p. 778. ^ a b Abril & Periáñez 2016, p. 242. ^ a b c Abril & Periáñez 2016, p. 243. ^ a b Stoica et al. 2016, p. 854. ^ Stoica et al. 2016, p. 867. ^ a b Estrada et al. 2011, p. 362. ^ Loget, Nicolas; Van Den Driessche, Jean (June 2006). "On the origin of the Strait of Gibraltar". Sedimentary Geology. 188–189: 341–356. Bibcode:2006SedG..188..341L. doi:10.1016/j.sedgeo.2006.03.012. ISSN 0037-0738.  ^ a b Estrada et al. 2011, p. 369. ^ Estrada et al. 2011, p. 368. ^ Estrada et al. 2011, p. 371. ^ a b Garcia-Castellanos et al. 2009, p. 779. ^ Cornée et al. 2016, p. 115,116. ^ a b Periáñez & Abril 2015, p. 55. ^ Lagerloef, Gary; Schmitt, Raymond; Schanze, Julian; Kao, Hsun-Ying (1 December 2010). "The Ocean and the Global Water Cycle". Oceanography. 23 (4): 85. doi:10.5670/oceanog.2010.07.  ^ Garcia-Castellanos et al. 2009, p. 780. ^ Garcia-Castellanos et al. 2009, p. 781. ^ Periáñez & Abril 2015, p. 60. ^ Stoica et al. 2016, p. 868. ^ Just et al. 2011, p. 52. ^ Cornée et al. 2016, p. 127. ^ Just et al. 2011, p. 53. ^ a b " Mediterranean
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megaflood confirmed Cosmos". cosmosmagazine.com. Retrieved 2018-03-28.  ^ Marzocchi, Alice; Flecker, Rachel; Baak, Christiaan G.C. van; Lunt, Daniel J.; Krijgsman, Wout (1 July 2016). " Mediterranean
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outflow pump: An alternative mechanism for the Lago-mare and the end of the Messinian
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succession of the Crotone Basin (southern Italy) I: Stratigraphic architecture reconstructed by seismic and well data". Marine and Petroleum Geology. 48: 455. doi:10.1016/j.marpetgeo.2013.08.014. ISSN 0264-8172.  ^ Cornée, Jean-Jacques; Münch, Philippe; Melinte-Dobrinescu, Mihaela; Moussa, Abdelkhalak Ben; Quillévéré, Frédéric; Drinia, Hara; Azdimousa, Ali; Touhami, Abdelouahed Ouazani; Merzeraud, Gilles; Fauquette, Séverine; Corsini, Michel; Moissette, Pierre; Feddi, Najat (March 2014). "The Early Pliocene
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Sources[edit]

Abril, J.M.; Periáñez, R. (December 2016). "Revisiting the time scale and size of the Zanclean flood of the Mediterranean
Mediterranean
(5.33Ma) from CFD simulations". Marine Geology. 382: 242–256. Bibcode:2016MGeol.382..242A. doi:10.1016/j.margeo.2016.10.008. ISSN 0025-3227.  Blanc, Paul-Louis (30 May 2012). "The opening of the Plio-Quaternary Gibraltar Strait: assessing the size of a cataclysm". Geodinamica Acta. 15 (5–6): 303–317. doi:10.1080/09853111.2002.10510763.  Cipollari, Paola; Cosentino, Domenico; Radeff, Giuditta; Schildgen, Taylor F.; Faranda, Costanza; Grossi, Francesco; Gliozzi, Elsa; Smedile, Alessandra; Gennari, Rocco; Darbaş, Güldemin; Dudas, Francis Ö; Gürbüz, Kemal; Nazik, Atike; Echtler, Helmut (1 January 2013). "Easternmost Mediterranean
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evidence of the Zanclean flooding event and subsequent surface uplift: Adana Basin, southern Turkey". Geological Society, London, Special
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Publications. 372 (1): 473–494. Bibcode:2013GSLSP.372..473C. doi:10.1144/SP372.5. ISSN 0305-8719.  Cornée, Jean-Jacques; Münch, Philippe; Achalhi, Mohammed; Merzeraud, Gilles; Azdimousa, Ali; Quillévéré, Frédéric; Melinte-Dobrinescu, Mihaela; Chaix, Christian; Moussa, Abdelkhalak Ben; Lofi, Johanna; Séranne, Michel; Moissette, Pierre (March 2016). "The Messinian erosional surface and early Pliocene
Pliocene
reflooding in the Alboran Sea: New insights from the Boudinar basin, Morocco". Sedimentary Geology. 333: 115–129. Bibcode:2016SedG..333..115C. doi:10.1016/j.sedgeo.2015.12.014. ISSN 0037-0738.  Estrada, Ferran; Ercilla, Gemma; Gorini, Christian; Alonso, Belén; Vázquez, Juan Tomás; García-Castellanos, Daniel; Juan, Carmen; Maldonado, Andrés; Ammar, Abdellah; Elabbassi, Mohammed (1 December 2011). "Impact of pulsed Atlantic water inflow into the Alboran Basin at the time of the Zanclean flooding". Geo-Marine Letters. 31 (5–6): 361–376. Bibcode:2011GML....31..361E. doi:10.1007/s00367-011-0249-8. ISSN 0276-0460.  Garcia-Castellanos, D.; Estrada, F.; Jiménez-Munt, I.; Gorini, C.; Fernàndez, M.; Vergés, J.; Vicente, R. De (2009). "Catastrophic flood of the Mediterranean
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after the Messinian
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salinity crisis". Nature. 462 (7274): 778–781. Bibcode:2009Natur.462..778G. doi:10.1038/nature08555. ISSN 1476-4687.  Just, Janna; Hübscher, Christian; Betzler, Christian; Lüdmann, Thomas; Reicherter, Klaus (1 February 2011). "Erosion of continental margins in the Western Mediterranean
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Salinity Crisis". Geo-Marine Letters. 31 (1): 51–64. Bibcode:2011GML....31...51J. doi:10.1007/s00367-010-0213-z. ISSN 0276-0460.  Periáñez, R.; Abril, J.M. (April 2015). "Computational fluid dynamics simulations of the Zanclean catastrophic flood of the Mediterranean
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(5.33Ma)". Palaeogeography, Palaeoclimatology, Palaeoecology. 424: 49–60. doi:10.1016/j.palaeo.2015.02.017. ISSN 0031-0182.  Silva, P.G.; Elez, Javier; Huerta, Pedro; Llovera, Jorge; Perucha, Maria Angeles; Roquero, Elvira; Rodriguez-Pascua, Miguel; Martínez-Graña, A; Azcárate, Teresa; Reicherter, Klaus (6 November 2017). "Sedimentary record of pre-Quaternary tsunamis in the Gibraltar Strait area after the Zanclean flooding" (PDF). IX Reunião do Quaternário Ibérico, Faro: 137–140 – via ResearchGate.  Stoica, Marius; Krijgsman, Wout; Fortuin, Anne; Gliozzi, Elsa (January 2016). "Paratethyan ostracods in the Spanish Lago-Mare: More evidence for interbasinal exchange at high Mediterranean
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External links[edit]

Media related to Messinian salinity crisis
Messinian salinity crisis
at Wikimedia Commons "Dramatic flood filled Mediterranean
Mediterranean
Sea". Agence France-Presse. 10 December 2009. Retrieved 2 De

.