Editing Mediterranean Sea (section)

====Desiccation and exchanges of flora and fauna====
{{See also|Pleistocene megafauna|Dwarf elephant}}
The present-day Atlantic gateway, the [[Strait of Gibraltar]], originated in the early Pliocene via the [[Zanclean Flood]]. As mentioned, there were two earlier gateways: the [[Betic Corridor]] across southern Spain and the Rifian Corridor across northern Morocco. The Betic closed about 6 mya, causing the Messinian salinity crisis (MSC); the Rifian or possibly both gateways closed during the earlier [[Tortonian]] times, causing a "[[Tortonian salinity crisis]]" (from 11.6 to 7.2 mya), long before the MSC and lasting much longer. Both "crises" resulted in broad connections between the mainlands of Africa and Europe, which allowed migrations of flora and fauna—especially large mammals including primates—between the two continents. The [[Vallesian|Vallesian crisis]] indicates a typical extinction and replacement of mammal species in Europe during Tortonian times following climatic upheaval and overland migrations of new species:<ref>{{Cite book
 | last1 = Agusti | first1 = J
 | last2 = Moya-Sola | first2 = S
 | title = Mammal extinctions in the Vallesian (Upper Miocene)
 | volume = 30 | year = 1990 | pages = 425–432
 | issn = 1613-2580 | doi = 10.1007/BFb0011163
 | series = Lecture Notes in Earth Sciences
 | isbn = 978-3-540-52605-6
 }} (Abstract)</ref> see Animation: Messinian salinity crisis (and mammal migrations), at right.

The almost complete enclosure of the Mediterranean basin has enabled the oceanic gateways to dominate seawater circulation and the environmental evolution of the sea and basin. Circulation patterns are also affected by several other factors—including climate, bathymetry, and water chemistry and temperature—which are interactive and can induce precipitation of [[evaporite]]s. Deposits of evaporites accumulated earlier in the nearby [[Geology of the Western Carpathians#Foredeep|Carpathian foredeep]] during the [[Middle Miocene]], and the adjacent [[Red Sea Basin]] (during the [[Late Miocene]]), and in the whole Mediterranean basin (during the MSC and the [[Messinian]] age). Many [[diatomite]]s are found underneath the evaporite deposits, suggesting a connection between their{{clarify|date=August 2019}} formations.

Today, evaporation of surface seawater (output) is more than the supply (input) of fresh water by precipitation and coastal drainage systems, causing the salinity of the Mediterranean to be much higher than that of the Atlantic—so much so that the saltier Mediterranean waters sink below the waters incoming from the Atlantic, causing a two-layer flow across the Strait of Gibraltar: that is, an outflow [[Strait of Gibraltar#Inflow and outflow|''submarine current'']] of warm saline Mediterranean water, counterbalanced by an inflow surface current of less saline cold oceanic water from the Atlantic. In the 1920s, Herman Sörgel proposed the building of a hydroelectric dam (the [[Atlantropa]] project) across the Straits, using the inflow current to provide a large amount of hydroelectric energy. The underlying energy grid was also intended to support a political union between Europe and, at least, the Maghreb part of Africa (compare [[Eurafrique|Eurafrika]] for the later impact and [[Desertec]] for a later project with some parallels in the planned grid).<ref>Politische Geographien Europas: Annäherungen an ein umstrittenes Konstrukt, Anke Strüver, LIT Verlag Münster, 2005, p. 43</ref>