To start with ....
A broad Overview of the Mediterranean sea.
The Mediterranean Sea.
The Mediterranean
Sea is a 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 usually identified as a completely separate body of
water.
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 travellers of
ancient times that allowed for trade and cultural exchange between emergent
peoples of the region. The history 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."
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.
The International Hydrographic
Organization defines the limits of the Mediterranean Sea as follows:
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 North-eastern 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.)
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. Evaporation is especially high in its eastern half, causing the water
level to decrease and salinity to increase eastward. This pressure
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. 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.
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 sub regions (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 and may also be thermal.
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
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 counter clockwise 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 of Alboran Domain, subduction
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-eustatic
processes.
Pale environmental 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 evaporates. During late Miocene times, a so-called "Messinian Salinity Crisis" (MSC
hereafter) occurred, which was triggered by the closure of the Atlantic
gateway. Evaporates
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 evaporate
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.
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.
Paleoclimate
Because of its 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, helping to
constrain the time of past Geomagnetic Reversals.
Furthermore, the exceptional accuracy of these
paleo-climatic records have improved our knowledge of the Earth's orbital variations
in the past.
So there you have it... A broad overview of the Mediterranean
sea. It is a truly magical place... good times were had by all!
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