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تكنولوجيا استزراع جديدة يعرضها رئيس مجلس ادارة جهاز حماية وتنمية البحيرات والثروة السمكية و د/ أحمد نصر الله مدير المركزالدولي للأسماك
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ورشة العمل الثالثة من "حوار الخبراء" حول قطاع الزراعة والقوانين التشريعية
منصة حوار الخبراء لوثيقة ملكية الدولة تهدف إلى تفعيل حوار بنَّاء بين الحكومة والخبراء والمتخصصين في المجالات الاقتصادية
وثيقة ملكية الدولة لوضع الأسس والمرتكزات الرئيسة لتواجد الدولة في النشاط الاقتصادي و سياسة الملكية التي تتبعها الدولة

 

The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Europe and Anatolia, on the south by North Africa, and on the east by the Levant. The sea is sometimes considered a part of the Atlantic Ocean, although it is often identified as a completely separate body of water.

The name Mediterranean is derived from the Latin mediterraneus, meaning "inland" or "in the middle of the land" (from medius, "middle" and terra, "land"). It covers an approximate area of 2.5 million km² (965,000 sq mi), but its connection to the Atlantic (the Strait of Gibraltar) is only 14 km (8.7 mi) wide. Inoceanography, it is sometimes called the Eurafrican Mediterranean Sea or the European Mediterranean Sea to distinguish it from mediterranean seaselsewhere.[3][4]

The Mediterranean Sea has an average depth of 1,500 m (4,900 ft) and the deepest recorded point is 5,267 m (17,280 ft) in the Calypso Deep in the Ionian Sea.

It was an important route for merchants and travelers of ancient times that allowed for trade and cultural exchange between emergent peoples of the region. Thehistory of the Mediterranean region is crucial to understanding the origins and development of many modern societies. "For the three quarters of the globe, the Mediterranean Sea is similarly the uniting element and the centre of World History

 

Name

The term Mediterranean derives from the Latin word mediterraneus, meaning "in the middle of earth" or "between lands" (medius, "middle, between" + terra, "land, earth"): as it is between the continents of Africa and Europe. The Greek name Mesogeios (Μεσόγειος), is similarly from μέσο, "middle" + γη, "land, earth").[6]

The Mediterranean Sea has historically had several names. For example the Romans commonly called it Mare Nostrum (Latin, "Our Sea"), and occasionally Mare Internum (Sallust, Jug. 17).

In the Bible, it was primarily known as הים הגדול (HaYam HaGadol), the "Great Sea", (Num. 34:6,7; Josh. 1:4, 9:1, 15:47; Ezek. 47:10,15,20), or simply "The Sea" (1 Kings 5:9; comp. 1 Macc. 14:34, 15:11); however, it has also been called the "Hinder Sea", due to its location on the west coast of the Holy Land, and therefore behind a person facing the east, sometimes translated as "Western Sea", (Deut. 11:24;Joel 2:20). Another name was the "Sea of the Philistines" (Exod. 23:31), from the people occupying a large portion of its shores near the Israelites.

In Modern Hebrew, it has been called HaYam HaTikhon (הַיָּם הַתִּיכוֹן), "the middle sea", a literal adaptation of the German equivalent Mittelmeer.[citation needed] In Turkish, it is known as Akdeniz, "the white sea". In modern Arabic, it is known as al-Baḥr al-Abyaḍ al-Mutawassiṭ (البحر الأبيض المتوسط), "the White Middle Sea", while in Islamic and older Arabic literature, it was referenced as Baḥr al-Rūm (بحر الروم), or "the Roman/Byzantine Sea."

History

Main article: History of the Mediterranean regionThe Holy League naval victory over theOttoman Empire at the Battle of Lepanto, 1571, the last battle to be fought primarily between galleys.

Several ancient civilisations were located around its shores; thus it has had a major influence on those cultures. It provided routes for trade, colonisation and war, and provided food (by fishing and the gathering of other seafood) for numerous communities throughout the ages.[7]

The sharing of similar climate, geology and access to a common sea led to numerous historical and cultural connections between the ancient and modern societies around the Mediterranean.

Two of the most notable Mediterranean civilisations in classical antiquity were the Greek city states and the Phoenicians. When[citation neededAugustus founded theRoman Empire, the Mediterranean Sea began to be called Mare Nostrum (literally:"Our Sea") by the Romans.

Darius I of Persia, who conquered Ancient Egypt, built a canal linking the Mediterranean to the Red Sea. Darius's canal was wide enough for two triremes to pass each other with oars extended, and required four days to traverse.[8]

The western Roman empire collapsed around AD 476. Temporarily the east was again dominant as the Byzantine Empire formed from the eastern half of the Roman empire. Another power soon arose in the east: Islam. At its greatest extent, the Arab Empire controlled 75% of the Mediterranean region.

Europe was reviving, however, as more organized and centralized states began to form in the later Middle Ages after the Renaissance of the 12th century.

Ottoman power continued to grow, and in 1453, the Byzantine Empire was extinguished with the fall of Constantinople. The growing naval prowess of the European powers confronted further rapid Ottoman expansion in the region when the Battle of Lepanto checked the power of the Ottoman navy. The development of oceanic shipping began to affect the entire Mediterranean. Once, all trade from the east had passed through the region, but now the circumnavigation of Africa allowed spices and other goods to be imported through the Atlantic ports of western Europe.[9][10][11]

Geography

A satellite image showing the Strait of Gibraltar. Left is the Iberian Peninsula in Europe; on the right, theMaghreb in Africa.The Dardanelles strait. The north side is Europe with the Gelibolu Peninsula in the Thrace region; the south side is Anatolia in Asia.

The Mediterranean Sea is connected to the Atlantic Ocean by the Strait of Gibraltar in the west and to the Sea of Marmara and the Black Sea, by the Dardanelles and the Bosporus respectively, in the east. The Sea of Marmara is often considered a part of the Mediterranean Sea, whereas the Black Sea is generally not. The 163 km (101 mi) long man-made Suez Canal in the southeast connects the Mediterranean Sea to the Red Sea.

Large islands in the Mediterranean include CyprusCreteEuboeaRhodesLesbosChiosKefaloniaCorfuNaxos and Andros in theeastern MediterraneanSardiniaCorsicaSicilyCresKrkBračHvarPagKorčula and Malta in the central Mediterranean; and Ibiza,Majorca and Minorca (the Balearic Islands) in the western Mediterranean.

The typical Mediterranean climate has hot, dry summers and mild, rainy winters. Crops of the region include olivesgrapesoranges,tangerines, and cork.

Extent

The International Hydrographic Organization defines the limits of the Mediterranean Sea as follows:[12]

Stretching from the Strait of Gibraltar in the West to the entrances to the Dardanelles and the Suez Canal in the East, the Mediterranean Sea is bounded by the coasts of Europe, Africa and Asia, and is divided into two deep basins:

  • Western Basin:
    • On the west: A line joining the extremities of Cape Trafalgar (Spain) and Cape Spartel (Africa).
    • On the northeast: The West Coast of Italy. In the Strait of Messina a line joining the North extreme of Cape Paci (15°42'E) with Cape Peloro, the East extreme of the Island of Sicily. The North Coast of Sicily.
    • On the east: A line joining Cape Lilibeo the Western point of Sicily (37°47′N 12°22′E), through the Adventure Bank to Cape Bon (Tunisia).
  • Eastern Basin:
    • On the west: The Northeastern and Eastern limits of the Western Basin.
    • On the northeast: A line joining Kum Kale (26°11'E) and Cape Helles, the Western entrance to the Dardanelles.
    • On the southeast: The entrance to the Suez Canal.
    • On the east: The coasts of Syria and Palestine.

(It should be noted that the coast referred to as belonging to Palestine in this document dating to 1953 has been within the internationally recognised borders of the country known as Israel since 1948. Of the territories administered by the Palestinian Authority, only the Gaza Strip has a sea coast.)

Oceanography

Predominant surface currents for June

Being nearly landlocked affects conditions in the Mediterranean Sea: for instance, tides are very limited as a result of the narrow connection with the Atlantic Ocean. The Mediterranean is characterized and immediately recognised by its deep blue colour.

Evaporation greatly exceeds precipitation and river runoff in the Mediterranean, a fact that is central to the water circulation within the basin.[13] Evaporation is especially high in its eastern half, causing the water level to decrease and salinity to increase eastward.[14] Thispressure gradient pushes relatively cool, low-salinity water from the Atlantic across the basin; it warms and becomes saltier as it travels east, then sinks in the region of the Levant and circulates westward, to spill over the Strait of Gibraltar.[15] Thus, seawater flow is eastward in the Strait's surface waters, and westward below; once in the Atlantic, this chemically distinct Mediterranean Intermediate Water can persist thousands of kilometres away from its source.[16]

Coastal countries

Map of the Mediterranean Sea

Twenty-one modern states have a coastline on the Mediterranean Sea. They are:

Turkey and Egypt are transcontinental countries. The southernmost islands of Italy, the Pelagie islands, are geologically part of the African continent.

Several other territories also border the Mediterranean Sea (from west to east):

Catania, Sicily, with mount Etna in the background.

Capital cities of sovereign countries and major cities (municipalities) with populations larger than 200,000 people bordering the Mediterranean Sea are (capitals with fewer than 200,000 inhabitants are marked with an asterisk):

 

Geology

See also: Geology and paleoclimatology of the Mediterranean BasinA submarine karst spring, calledvrulja, observed through sea surface rippling near Omišmya agoThe closing of GibraltarMessinian salinity crisis, 5.96 to 5.33 myaZanclean flood

The geologic history of the Mediterranean is complex. It was involved in the tectonic break-up and then collision of the African and Eurasian plates. The Messinian Salinity Crisis occurred in the late Miocene (12 million years ago to 5 million years ago) when the Mediterranean dried up. Geologically the Mediterranean is underlain by oceanic crust.

The Mediterranean Sea has an average depth of 1,500 m (4,900 ft) and the deepest recorded point is 5,267 m (17,280 ft) in the Calypso Deep in the Ionian Sea. The coastline extends for 46,000 km (29,000 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 mi²) and the Eastern Mediterranean about 1.65 million km² (0.64 million mi²). A characteristic of the Mediterranean Sea are submarine karst springs or vruljas, which mainly occur in shallow waters[17] and may also be thermal.[18]

Tectonic evolution

The geodynamic evolution of the Mediterranean Sea was provided by the convergence of European and African plates and several smaller microplates. This process was driven by the differential seafloor spreading along the Mid-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.

According to a report published by Nature in 2009, scientists think that the Mediterranean Sea was mostly filled during a time period of less than two years, in a major flood (the Zanclean flood) that happened approximately 5.33 million years ago, in which water poured in from the Atlantic Ocean and through the Strait of Gibraltar, at a rate three times the current flow of the Amazon River.[19]

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 resulted in 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 Ma 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 characterised by the anticlockwise 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 extensional deformation led to the opening of the Tyrrenian basin.

Western Mediterranean

The Betic-Rif mountain belts developed during Mesozoic and Cenozoic times, as Africa and Iberia converged. Tectonic models for its evolution include: rapid motion ofAlboran microplatesubduction zone and radial extensional collapse caused by convective removal of lithospheric 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-eustaticprocesses.

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 evaporitedeposits, 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.

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. The Neotethys formed during the Late Triassic and Early Jurassic rifting of the African and Eurasian plates.

Amany Esmail

Manger of GAFRD Web Site

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الهيئة العامة لتنمية الثروة السمكيةhttp://www.gafrd.org/ [email protected] www.GAFRD.org

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