Mediterranean Subdivisions and Geology Subdivisions: According to the International Hydrographic Organization (IHO) treaties, the Mediterranean Sea is subdivided into a number of smaller seas, each with their own designation (from west to east): A view of Raouché off the coast of Beirut, Lebanon. A view across the straits of Gibraltar. A point between Minorca and Barcelona. Mediterranean coast in Israel.the Alboran Sea, between Spain and Morocco, the Balearic Sea, between mainland Spain and its Balearic Islands[6], the Ligurian Sea between Corsica and Liguria (Italy), the Adriatic Sea between Italy, Slovenia, Croatia, Bosnia and Herzegovina, Montenegro and Albania the Ionian Sea between Italy, Greece, and Albania, the Aegean Sea between Greece and Turkey the Sea of Marmara between the Aegean and Black Sea Other Seas: Although not recognized by the IHO treaties, there are some other seas that are in common use from the ancient times or in present: the Sea of Sardinia, between Sardinia and Balearic Islands, as a part of the Balearic Sea the Tyrrhenian Sea enclosed by Sardinia, Italian peninsula and Sicily, the Sea of Sicily between Sicily and Tunisia, the Libyan Sea between Libya and Crete, In the Aegean Sea, the Thracian Sea in its north, the Myrtoan Sea between the Cyclades and the Peloponnese, the Sea of Crete north of Crete the Cilician Sea between Turkey and Cyprus Geology : The geology of the Mediterranean is complex, involving the break-up and then collision of the African and Eurasian plates and the Messinian Salinity Crisis in the late Miocene when the Mediterranean dried up. The Mediterranean Sea has an average depth of 1,500 metres (4,920 ft) and the deepest recorded point is 5,267 meters (about 3.27 miles) in the Calypso Deep in the Ionian Sea. The coastline extends for 46,000 kilometres (28,600 mi). A shallow submarine ridge (the Strait of Sicily) between the island of Sicily and the coast of Tunisia divides the sea in two main subregions (which in turn are divided into subdivisions), the Western Mediterranean and the Eastern Mediterranean. The Western Mediterranean covers an area of about 0.85 million km² (0.33 million sq mi) and the Eastern Mediterranean about 1.65 million km² (0.64 million sq mi). Geodynamic: The geodynamic evolution of the Mediterranean Sea was provided by the convergence of European and African plates. This process was driven by the differential spreading along the Atlantic ridge, which led to the closure of the Tethys Ocean and eventually to the Alpine orogenesis. However, the Mediterranean also hosts wide extensional basins and migrating tectonic arcs, in response to its land-locked configuration. Eastern Mediterranean: In middle Miocene times, the collision between the Arabian microplate and Eurasia led to the separation between the Tethys and the Indian Oceans. This process determined profound changes in the oceanic circulation patterns, which shifted global climates towards colder conditions. The Hellenic Arc, which has a land-locked configuration, underwent a widespread extension for the last 20 Myr due to a slab roll-back process. In addition, the Hellenic Arc experienced a rapid rotation phase during the Pleistocene, with a counterclockwise component in its eastern portion and a clockwise trend in the western segment. Central Mediterranean: The opening of small oceanic basins of the central Mediterranean follows a trench migration and back-arc opening process that occurred during the last 30 Myr. This phase was characterized by the counterclockwise rotation of the Corsica-Sardinia block, which lasted until the Langhian (ca.16 Ma), and was in turn followed by a slab detachment along the northern African margin. Subsequently, a shift of this active extentional deformation led to the opening of the Tyrrenian basin. Western Mediterranean: Since Mesozoic to Tertiary times, during convergence between Africa and Iberia, it developed the Betic-Rif mountain belts. Tectonic models for its evolution include: rapid motion of Alboran microplate, subduction zone and radial extentional collapse caused by convective removal of lithosferic mantle. The development of these intramontane Betic and Rif basins led to the onset of two marine gateways which were progressively closed during the late Miocene by an interplay of tectonic and glacio-eustatic processes. Paleoclimatic: Because of its peculiar latitudinal position and its land-locked configuration, the Mediterranean is especially sensitive to astronomically induced climatic variations, which are well documented in its sedimentary record. Since the Mediterranean is involved in the deposition of eolian dust from the Sahara during dry periods, whereas riverine detrital input prevails during wet ones, the Mediterranean marine sapropel-bearing sequences provide high-resolution climatic information. These data have been employed in reconstructing astronomically calibrated time scales for the last 9 Ma of the earth's history. Furthermore, the exceptional accuracy of these paleoclimatic records improved our knowledge of the earth's orbital variations in the past. Paleoenvironmental analysis: Its semi-enclosed configuration makes the oceanic gateways critical in controlling circulation and environmental evolution in the Mediterranean Sea. Water circulation patterns are driven by a number of interactive factors, such as climate and bathymetry, which can lead to precipitation of evaporites. During late Miocene times, a so-called "Messinian Salinity Crisis" (MSC hereafter) occurred, which was triggered by the closure of the Atlantic gateway. Evaporites accumulated in the Red Sea Basin (late Miocene), in the Carpatian foredeep (middle Miocene) and in the whole Mediterranean area (Messinian). An accurate age estimate of the MSC—5.96 Ma—has recently been astronomically achieved; furthermore, this event seems to have occurred synchronously. The beginning of the MSC is supposed to have been of tectonic origin; however, an astronomical control (eccentricity) might also have been involved. In the Mediterranean basin, diatomites are regularly found underneath the evaporitic deposits, thus suggesting (albeit not clearly so far) a connection between their geneses. The present-day Atlantic gateway, i.e. the Strait of Gibraltar, finds its origin in the early Pliocene. However, two other connections between the Atlantic Ocean and the Mediterranean Sea existed in the past: the Betic Corridor (southern Spain) and the Rifian Corridor (northern Morocco). The former closed during Tortonian times, thus providing a "Tortonian Salinity Crisis" well before the MSC; the latter closed about 6 Ma, allowing exchanges in the mammal fauna between Africa and Europe. Nowadays, evaporation is more relevant than the water yield supplied by riverine water and precipitation, so that salinity in the Mediterranean is higher than in the Atlantic. These conditions result in the outflow of warm saline Mediterranean deep water across Gibraltar, which is in turn counterbalanced by an inflow of a less saline surface current of cold oceanic water. In the last few centuries, mankind has done much to alter Mediterranean geology. Structures have been built all along the coastlines, exacerbating and rerouting erosional patterns. Many pollution-producing boats travel the sea that unbalance the natural chemical ratios of the region. Beaches have been mismanaged, and the overuse of the sea's natural and marine resources continues to be a problem. This misuse speeds along and/or confounds natural processes. The actual geography has also been altered by the building of dams and canals. The Mediterranean was once thought to be the remnant of the Tethys Ocean. It is now known to be a structurally younger ocean basin known as Neotethys. Neotethys formed during the Late Triassic and Early Jurassic rifting of the African and Eurasian plates. Ecology and biota: As a result of the drying of the sea during the Messinian Salinity Crisis, the marine biota of the Mediterranean are derived primarily from the Atlantic Ocean. The North Atlantic is considerably colder and more nutrient-rich than the Mediterranean, and the marine life of the Mediterranean has had to adapt to its differing conditions in the five million years since the basin was reflooded. The Alboran Sea is a transition zone between the two seas, containing a mix of Mediterranean and Atlantic species. The Alboran Sea has the largest population of Bottlenose Dolphins in the western Mediterranean, is home to the last population of harbour porpoises in the Mediterranean, and is the most important feeding grounds for Loggerhead Sea Turtles in Europe. The Alboran sea also hosts important commercial fisheries, including sardines and swordfish. In 2003, the World Wildlife Fund raised concerns about the widespread drift net fishing endangering populations of dolphins, turtles, and other marine animals. Environmental problems: Invasive species: The opening of the Suez Canal in 1869 created the first salt-water passage between the Mediterranean and Red Sea. The Red Sea is higher than the Eastern Mediterranean, so the canal serves as a tidal strait that pours Red Sea water into the Mediterranean. The Bitter Lakes, which are hypersaline natural lakes that form part of the canal, blocked the migration of Red Sea species into the Mediterranean for many decades, but as the salinity of the lakes gradually equalized with that of the Red Sea, the barrier to migration was removed, and plants and animals from the Red Sea have begun to colonize the Eastern Mediterranean. The Red Sea is generally saltier and more nutrient-poor than the Atlantic, so the Red Sea species have advantages over Atlantic species in the salty and nutrient-poor Eastern Mediterranean. Accordingly, Red Sea species invade the Mediterranean biota, and not vice versa; this phenomenon is known as the Lessepsian migration (after Ferdinand de Lesseps, the French engineer) or Erythrean invasion. The construction of the Aswan High Dam across the Nile River in the 1960s reduced the inflow of freshwater and nutrient-rich silt from the Nile into the Eastern Mediterranean, making conditions there even more like the Red Sea and worsening the impact of the invasive species. Invasive species originating from the Red Sea and introduced into the Mediterranean by the construction of the canal have become a major component of the Mediterranean ecosystem and have serious impacts on the Mediterranean ecology, endangering many local and endemic Mediterranean species. Up to this day, about 300 species native to the Red Sea have already been identified in the Mediterranean Sea, and there are probably others yet unidentified. In recent years, the Egyptian government's announcement of its intentions to deepen and widen the canal have raised concerns from marine biologists, fearing that such an act will only worsen the invasion of Red Sea species into the Mediterranean, facilitating the crossing of the canal for yet additional species. Pollution: Pollution in this region has been extremely high in recent years. The United Nations Environment Programme has estimated that 650 million tons of sewage, 129,000 tons of mineral oil, 60,000 tons of mercury, 3,800 tons of lead and 36,000 tons of phosphates are dumped into the Mediterranean each year. The Barcelona Convention aims to 'reduce pollution in the Mediterranean Sea and protect and improve the marine environment in the area, thereby contributing to its sustainable development.' Many marine species have been almost wiped out because of the sea's pollution. The Mediterranean Monk Seal is considered to be among the world's most endangered marine mammals. The Mediterranean is also plagued by marine debris. A 1994 study of the seabed using trawl nets around the coasts of Spain, France and Italy reported a particularly high mean concentration of debris; an average of 1,935 items per square kilometre. Plastic debris accounted for 77%, of which 93% was plastic bags. Home, Mediterranean Subdivisions and Geology, Mediterranean History, Mediterranean Diet, Old version of this homepage References: entry µes??a??? at Liddell & Scott Pinet, Paul R. (1996) Invitation to Oceanography, St Paul, MN: West Publishing Co., ISBN (3rd ed.), p.202, 206, 206–207 IHO Codes for Oceans & Seas, and Other Code Systems Limits of Oceans and Seas, Special Publication 23, 3rd Edition 1953, published by the International Hydrographic Organization Galil, B.S. and Zenetos, A. (2002). A sea change: exotics in the eastern Mediterranean Sea, in: Leppäkoski, E. et al. (2002). Invasive aquatic species of Europe: distribution, impacts and management. pp. 325-336. http://www.explorecrete.com/nature/mediterranean.html http://europa.eu/scadplus/leg/en/lvb/l28084.htm http://www.monachus-guardian.org/factfiles/medit01.htm Marine Litter: An analytical overview". United Nations Environment Programme (2005). Retrieved on 2008-08-01. Wikipedia.org

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