The 8 Seas of the Mediterranean
The rapid geographical. climatic and geological changes which are observable across the Mediterranean The western region, for example, includes the Alboran Sea and the huge depression of the Balearic, or Algerian-Provençal, basin. Corsica, Sardinia and Sicily mark the perimeter of the Tyrrhenian basin which is separated in its turn from the Adriatic Sea by the Apennine mountain chain. The lonian and Aegean Seas and the Levant Sea, cut off by deep trenches and archipelagos make up the eastern Mediterranean.
and the considerable variety of seabed topography make it possible to divide the basin into distinct
units which can be considered semisealed. .
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Alboran Sea
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Alboran Sea
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The Alboran Sea opens into the Mediterranean at the mouth of the Strait of Gibraltar and extends right to the Balearic basin, from which it is separated, according to the International Hydrographie Organization, by an ideal line joining Cabo de Gata in Spain and Cape Fegalo in Algeria.
Bordered by Spain, Morocco and Algeria, it covers a surface area of 54,000 square chilometers and has a maximum depth of approximately 1500 meters in the western sector and 1200 meters in the eastern sector. |
The continental shelf which extends to the 100-200 meters bathymetric line, the most interesting part for scuba divers, varies in width from 2 to 10 kilometers along the Spanish coastline and to the south, along the North African coast, has a maximum width of 18 kilometers.
The island of the same name lies in the center of the Alboran Sea; it is a small volcanic island, no higher than 10 meters at any point, surrounded by a seabed which plunges to a depth of 1800 meters in the Alboran trench, which is connected to the Algerian basin. |
Algérian-Provençal Basin
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This is the largest physlographical area of the western Mediterranean, roughly triangular in shape and lying between the Gulf of Valencia, the Ligurian Sea and the Alboran sea. In several points, off the mouth of the Ebro, for example, the continental shelf is as Ovide as 60 kilometers and even 72 km. Its point of minimum width (from 3 to 9 kilometers) is found in the area between Toulon and Genoa, a coastal strip distinguished by a sertes of numerous, deep, canyons, extending for many kilometers into the open sea. |
kilometers in the Gulf of Lions. The islands of Mallorca and Menorca share a common shelf, but Ibiza is separated by a seabed which fans to depths of up to 800 meters. The threshold between Sardinia and Tunisia separates the Tyrrhenian basin from the Algerian one. ln the center of the basin is the vast, Balearic plain, surrounded by a seabed varying in depth from 2600 to 2800 meters, inside which is wedged the fan of sedimentary deposits created by the Rhone.
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Tyrrhenian Basin
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The Tyrrhenian basin is almost 3800 meters and is the deepest part of the western Mediterranean.
The seabed is dominated by a large number of structural ridges and volcanic heights which correspond to underwater mountains like the ones named after Marsili, Vavilov and Magnaghi between Sardinia and Calabria. These summits, once above water, climb to heights of 2900 meters from the surrounding abyssal plains which in ancient times were real plains. Some of these abyssal plains have been revealed as beaches from 15 million years ago.
The abyssal plains cover very small areas. An arc of terrestrial, insular or submarine volcanoes, including Vesuvius, Etna and Stromboli, occupies the south-eastern part of the basin and is connected to the seismic area which traverses Calabria in southern Italy. The width of the continental shelf off Corsica and Sardinia |
varies from 5 to 25 kilometers, while along the coastline of the Italian mainland between La Spezia and the Gulf of Policastro it varies from 5-10 kilometers to over 65 kilometers in the Tuscan archipelago section. The basin is closed except for four communicating passages with the adjacent basins. To the north a deep channel leads to the Ligurian Sea, rising to a threshold at 300-400 meters below the surface. The Strait of Boniface between Corsica and Sardinia ives access to the Algerian basin across a seabed whose depth never exceeds 50 meters. The strip between Sicily and Sardinia which communicates with the Algerian basin is much wider and the channel descends to depths of 2000 meters. The Strait of Messina, which provides a passage to the lonian Sea, has a threshold of approximately 100 meters. |
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The Adriatic Sea covers an area of approximately 135.000 square kilometers, has a maximum depth of 1230 meters and lies in a wedge between Italy and the coastline of the ex-Yugoslav Republic and Albania. It communicates with the Ionan through the Strait of Otranto. It can be divided into three distinct parts based on the main features of its seabed: a continental shelf to the north and the center and a soutèern basin. The northern area is entirely under the influence of the Po delta and from the north right down to the Ancona barrier |
slopes slowly and very gradually to a maximum depth of just 75 meters. The central part (from Ancona to Gargano) on the other hand features a closed, jointed depression known as the Central Adriatic trench (depth 266 meters) which stretches southwards in a channel whose average depth is 160 meters. The southem part is more varied with a continental shelf which widens south of the Gargano to a width of 80 kilometers then narrows to 20 kilometers at the most southerly point of Apulia. In this section the edge of the self has a small series. |
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The black Sea is even more of an inland sea than the Mediterranean, to which it is connected by the Sea of Marmara and the Bosporus Strait (depth 40 meters).
In part at least this relationship can be compared to the one between the main Mediterranean basin and the Atlantic Ocean. Bordered by the countries of eastern Europe and Asia Minor, the Black Sea covers a surface area of 423,000 square kilometers with an averarage depth of 1272 meters, and a |
maximum of 2212 meters.
It is greatly influenced by the freh water of the Danube, it can in fat be compared to a huge estuary,and by its considerably stratified waters, which are the result ofthe difference in salinity between the surface and the deeper layers. Within the Black Sea the continental shelf is wide on the western and northen coastlines. |
Aegian Sea
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The Aegean Sea, which separates Greece and Turkey, is the start of the eastem part of the Mediterranean.
It covers an area of over 180,000 square kilometers and is characterized by the presence of over 200 islands stretching like a necklace across the whole of its surface. It is connected to the Ionian Sea by the shallow (56 meters) Gulf of Corinth. The Crete sub-basin is in the south of the Aegean and is bordered by the islands of Kythera, Crete and Rhodes. The many passages through these islands into the Mediterranean vary in depth between 300 and 800 meters. |
The principal feature in this sector is the Cretan Trench, an arc which runs from the Gulf of Argolis to Rhodes, reaching a maximum depth of 2500 meters.
To the northeast of the Aegean basin is the Sea of Marmara, 10,350 square kilometers, which communicates with the Mediterranean through the Dardanelles Strait and via the Bosporus with the Black Sea. There is a trench in the middle consisting of three small consecutive depressions, the deepest of which reaches 1389 meters and is connected to the Anatolian Trench, which is the continuation of the North Anatolian fault. |
Levant Sea
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This region of the Mediterranean includes the most eastern part and is bordered to the west by an ideal fine running from Cape Rais al Hilal
in Libya to the island of Gavdos facing Crete. It covers a surface area of 320,000 square kilometers with a maximum depth of 4384 meters and is closed to the north by Crete, the Dodecanese archipelago and by Turkey. The continental shelf is particularly developed both off the Gulf of Iskenderun, due to the presence of numerous rivers which together form a wide delta and off the Nile delta , but it is very narrow between Turkey and Syria. |
The continental escarpment has many canyons: the Pliny (4834 meters) and the Strabone (3720meters) trenches run between the Mediterranean Ridge and the underwater peak Ptolemy.
In the Sea of Levant the ridge runs eastnorth-east and rises to 700 meters above the surrounding abyssal plains. It, too, can be divided into several sub-basins, according to the nature of its seabed: Herodotus, Cyprus, Anatolia, Cilicia and Rhodes. |
Ionan Sea
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The lonian Sea is in the central Mediterranean and stretches from the African coast of Libya and Tunisia to Southern Italy and Greece. It covers an area of approximately 616,000 square kilometers and reaches a depth of 5093 meters in the Hellenic Trench, the maximum depth surveyed anywhere in the Mediterranean.
It has the largest abyssal plain in the eastern Mediterranean, but it too is divided into smaller plains separated from each other by underwater mountains and plateaux.
It is, therefore, possible to identify a Sicilian basin, with a maximum depth of around 3600 meters with a peak of 4013 m, closed in the north by the Messina threshold and broken in the south by part of the Mediterranean Ridge.
The southern region includes the plain of Sirte where the seabed reaches depths of 3847 meters The Hellenic Trench runs alongside the Mediterranean Ridge towards the east. It lies at the base of the edge of the Greek continental shelf and stretches for over 300 kilometers at an average depth of |
3000 meters ad is separated from the threshold of the same name by the underwater peak, also of the same name, at 3400 meters. The Herodotus Trench lies along the edge of the Libyan continental shelf at 3000 meters
The continental shelf comprises two main sectors. The first begins with the Avventura Bank between Sicily and Tunisia, continues along the Sicilian coastline until it joins the Maltese elevation, from where it plunges eastwards. The larger of the two parts, the biggest in the Mediterranean, lies along the Tunisian coast (the Gulf of Gabes) and extends right to the Italian island of Lampedusa, which geologically is part of Africa.
The northern sector of the lonian continental shelf gradually narrows along the Libyan coastline to a little under 4 kilometers wide at Cape Rais al Hilal. |
