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The Messinian Salinity Crisis (MSC), also referred to as the Messinian Event, and in its latest stage as the Lago Mare event, was a geological event during which the Mediterranean Sea went into a cycle of partly or nearly complete desiccation throughout the latter part of the Messinian age of the Miocene epoch, from 5.96 to 5.33 Ma (million years ago). It ended with the Zanclean flood, when the Atlantic reclaimed the basin.〔Gautier, F., Clauzon, G., Suc, J.P., Cravatte, J., Violanti, D., 1994. Age and duration of the Messinian salinity crisis. C.R. Acad. Sci., Paris (IIA) 318, 1103–1109.〕 Sediment samples from below the deep seafloor of the Mediterranean Sea, which include evaporite minerals, soils, and fossil plants, show that, about 5.96 million years ago in the late Miocene period, the precursor of the Strait of Gibraltar closed tight and the Mediterranean Sea, for the first time and then repeatedly, partially desiccated. The strait closed 5.6 Ma for the last time and, because of the generally dry climate conditions, within a millennium the Mediterranean basin nearly completely dried out, evaporating into a deep dry basin bottoming at some places below the world ocean level, with a few hypersaline Dead Sea-like pockets. Around 5.5 Ma, less dry climatic conditions allowed the basin to resume receiving more fresh water from rivers, with pockets of Caspian-like brackish waters getting progressively less hyper-saline, until the Strait of Gibraltar finally reopened 5.33 Ma with the Zanclean flood. Even now the Mediterranean is saltier than the North Atlantic because of its near isolation by the Strait of Gibraltar and its high rate of evaporation. If the Strait of Gibraltar closes again, which is likely to happen in the near geological future (though extremely distantly on a human time scale), the Mediterranean would mostly evaporate in about a thousand years.〔"Only the inflow of Atlantic water maintains the present Mediterranean level. When that was shut off sometime between 6.5 to 6 MYBP, net evaporative loss set in at the rate of around 3,300 cubic kilometers yearly. At that rate, the 3.7 million cubic kilometres of water in the basin would dry up in scarcely more than a thousand years, leaving an extensive layer of salt some tens of meters thick and raising global sea level about 12 meters." Cloud, P. (1988). ''Oasis in space. Earth history from the beginning'', New York: W.W. Norton & Co. Inc., 440. ISBN 0-393-01952-7〕 After that, continued northward movement of Africa may obliterate the Mediterranean: see Mediterranean Ridge. ==Naming and first evidence== The Messinian salt deposits that are outcropping (because they were uplifted by tectonic activity during later episodes) in places like Messina in Sicily, northeast Libya, Italy, and southern Spain have been described since the 19th century and it is then that the salinity crisis theory started to be developed. Karl Mayer-Eymar (1826–1907), a Swiss geologist and palaeontologist, studied fossils between gypsum-bearing, brackish and freshwater sediment layers and identified them as having been deposited just before the end of the Miocene Epoch. In 1867, he named the period the Messinian, for the region of Messina, Italy.〔Mayer-Eymar, Karl (1867) ''Catalogue systématique et descriptif des fossiles des terrains tertiaires qui se trouvent du Musée fédéral de Zürich'' (Zürich, Switzerland: Librairie Schabelitz, 1867), (page 13. ) From page 13: ''"Dans ces circonstances, je crois qu'il m'est permis comme créateur d'une classification conséquente et logique de proposer pour l'étage en question un nom qui lui convient en tous points. Ce nom est celui d'Etage messinien."'' (In these circumstances, I think that I am permitted as the creator of a consistent and logical classification to propose for the stage in question a name that suits it in every way. That name is that of the Messinian stage.)〕 Since then, salt-bearing and gypsum-bearing evaporite layers in many Mediterranean countries have been dated to that period.〔Kenneth J. Hsu, ''The Mediterranean Was a Desert,'' Princeton University Press, Princeton, New Jersey 1983. ''A Voyage of the Glomar Challenger.''〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Messinian salinity crisis」の詳細全文を読む スポンサード リンク
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