1.1 The Mediterranean: the birth of a sea

The Mediterranean is a sea situated in the middle of the land, enclosed between Europe, Africa and Asia. It is ancient, his origins are lost in time and as such it has witnessed the birth of many civilizations.

The Cretans were some of the first populations to use the Mediterranean as a strategic commercial route,then the great Phoenician navigators arrived and after them the Greeks. They dominated unchallenged the Mediterranean all through the competition with the Etruscans, Carthaginians and the people of Sicily, but the arrival of the Romans changed everything. For Rome the Mediterranean was its sea, “Mare nostrum”.

The Mediterranean is what remains of a much larger sea than the one we know today: the Tetide, that millions of years ago surrounded a single large block of land, the Pangea. During the course of millions of years this supercontinent has fragmented into various parts that, recombining with each other, gave origin to the modern continents as we know them today (Fig. 1_SES1.1 The Mediterranean Sea today (Mercator Projection, Datum WGS84)).

Fig. 1_SES1.1 The Mediterranean Sea today (Mercator Projection, Datum WGS84). By Eva Turicchia.

Thirty million years ago the Mediterranean Sea was trapped between two plaques: the Eurasian and the African ones. The Mediterranean suffered quite a few subversive events culminating a cataclysm that caused its complete drainage, something really difficult to imagine (Fig. 2_SES1.1 Wikipedia Commons, Paubah). This event is known as the Messinian salinity crisis (Video1_SES1.1) and it gave the opportunity for many terrestrial species, mainly mammals, to migrate into the empty basin, from Africa towards Europe. Fortunately the waters of the Ocean found a way through: the current Strait of Gibraltar worked as a passage for these waters, which formed a giant waterfall, filling the basin again.

Fig. 2_SES1.1 Messinian salinity crisis. By Paubahi – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20096264
Video 1_SES1.1 Messinian salinity crisis – animation.
by Federica Brigida (Arts student) under the direction of Marina Bolado, David Gomez, and Daniel García-Castellanos (Project WikiArS). Based on previous art-work By Mantero, Garcia-Castellanos and Pau Bahí

Nowadays the Mediterranean covers an area of approximately 2’500’000 km2 with an average depth of 1501 m, while the maximum depth off the Greek coast is more than 5000 m. There are 9 large islands: Cyprus, Rhodes, Crete, Sardinia, Sicily, Corsica, Malta, Menorca and Majorca. They were created by the movements of the Eurasian and African plates that originated the Mediterranean during the course of millions of years; for example the current shape of both Sicily and Cyprus is only 12000 years old.

There are numerous physical and chemical variables that play a very important role in the Mediterranean Sea characteristics. For example its salinity, temperature, the tides and its currents are vital to the understanding of our sea. Learn about these important subjects by expanding your exploration!

1.1.1 The relationship between the Phoenician population and the Mediterranean Sea.

The Phoenicians, who lived between 2100 B.C. and 500 B.C, in the current Lebanon, have been the protagonists of their epoque, thanks to an important resource, which they have been able to take advantage of: the Mediterranean Sea. The term "Phoenicians" itself reminds us of royal purple, that they used to extract from murexes, molluskes that live in the Mediterranean Sea coasts. Their relationship with the Mediterranean Sea was very close. In fact, they were not just good fishermen, but they were also good merchants and navigators. Even Herodotus wrote about them, describing them as innovators in naval routes and astronomy. They were the first ones to study stars (in particular the costellation of Ursa Major) in order to orient themselves while navigating during night. Even if they were able to circumnavigate Africa and approach Sardinia's west coasts, they preferred coastal navigation. Thanks to the presence of the Mediterranean Sea, they monopolised world commerce. They gained a lot thanks to taking advantage of marine resources and also transporting other populations' goods, for example between Babilonians and Italian populations (for example Etruscans), Assirians, Greeks, Hittites and Egyptians.
In an epoque where almost the whole population lived on its coasts, the Mediterranean Sea represented an essential resource for every popoulation. Whoever among them had done it they would have been the protagonists of world commerce. This population has been the Phoenicians, who gained from the advantages that their important position brought.

1.1.2 The theory of plate tectonics: development of the theory.

The plate tectonic theory says that, originally, the mantle was covered by magma which began to solidify when the fluid rock reached a temperature lower than that of melting due to the absence of heat sources capable of maintaining the previous conditions. Two supercontinents were formed, which with the progressive cooling and solidification of the magma would be expanded each in the direction of the Equator, to join / collide forming a supercontinent, then fractured in turn due to the reduction in the volume of the underlying magma, both for the solidification, both due to its escape through the thinner points of the crust, the volcanoes. On the basis of geophysical and petrological studies it has been recognized that the earth's crust, together with the outermost part of the upper mantle below, forms the so-called lithosphere. The lithosphere is subdivided into a dozen tectonic plates (also called "tectonic plates") main (of various shape and size) and more numerous other micro plates; these plates can be compared to rafts that "float" on the layer immediately below the upper mantle, the asthenosphere. Fundamental for the recognition of the theory of plate tectonics and its mechanisms was the discovery of the expansion of the ocean floor, confirmed by the study of magnetic anomalies detected near the mid-Atlantic ridge. These anomalies are distributed in symmetrical bands along the two sides of the oceanic ridges, and the analysis of their chronology shows that the geological age of the basalts on the ocean floor increases, on each side, moving away from the ridge. Furthermore, the study of seismic phenomena brought new elements to explain the dynamics of the plates.

1.1.3 The theory of plate tectonics: key principles.

The Theory of plate tectonics was elaborated in the sixties of the twentieth century. It appears to be able to explain the phenomena affecting the earth's crust such as seismic activity, orogenesis and formation of oceanic pits and volcanoes. According to the "Theory of plate tectonics", the lithosphere, the most external rigid shell of the earth's crust, is divided into 20 rigid plates floating in the underlying asthenosphere. The latter one, due to the effect of temperature and pressure, despite being in the solid state behaves like a viscous fluid. The plates, floating, can: move away from each other; approach and clash; approach and scroll next to each other.
When two plates move away from each other, the rift is created or accentuated and two phenomena can occur:
•if the removal ceases after a short time between the two plates it remains only a large fracture, called tectonic pit.
•if the removal continues for a long time it determines the formation of a new sea that can become an ocean, while the two plates, dragged by convective motions, are moving away more and more.
If the plates that collide are two ocean plates, one bends and wedges under the other, dragged by the currents of the mantle. This plate forms, in front of the other, an oceanic pit and, descending towards deeper and warmer areas of the mantle, melts and becomes magma.
If the plates that collide are two continental plates, they have the same density, neither of them sink into the mantle, but they undergo compressions and, overlapping one another, form mountain ranges. This phenomenon is called orogenesis.
When two plates approach and slide one next to the other, along a line of contact that is called fault, there is neither production nor destruction of the earth's crust. This sliding happens in steps and this can cause earthquakes.

1.1.4 The Tethys Ocean: formation and history.

The sea of Tethys was created during the Permian and Triassic periods (about 300-200 million years ago).
It no longer exists.
The Tethys was named in 1893 by the Austrian geologist Eduard Suess. The name derives from the mythological Greek goddess Tethys.
There were actually at least two seas of Tethys. The continents were united in one, the Pangea. The first was an ocean born as Paleo Tethys Sea, about 320 million years ago, in the Paleozoic era.
Evidence of the existence of the Paleo Tethys sea is found in marine settlements extending from northern Turkey through Transcaucasia, northern Iran, and Afghanistan, northern Tibet, China, and Indochina.
Pangea began to break 200 million years ago. It is divided into 2 parts, Laurasia in the north and Gondwanaland in the south.
About 140 million years ago, Gondwana began breaking into four tectonic plates: African, Antarctic, Australian and Indian dishes. The rupture pushed Africa and India north through the Tethys and opened the Indian Ocean. The ocean becomes the Tethys Seaway or the second sea of Tethys. This Seaway became the home of many marine reptiles.
The last part of the Tethys was during the Cenozoic era some 50 million years ago.
During the Oligocene, large parts of central and eastern Europe were covered by a northern branch of the Tethys Ocean, called the Paratethys.
The Paratethys was separated from the Tethys with the formation of the Alps, Carpathians, Dinarides, Taurus, and Elburz mountains during the Alpine orogeny. During the late Miocene, the Paratethys gradually disappeared and became an isolated inland sea.

1.1.5 The Messinian Salinity Crisis: the scientific evidence.

The salinity crisis of the Messinian or Messinian event is a geological event occurred in the last part of the Messinian Miocene period (over 5 million years ago), during which the waters of the Mediterranean Sea evaporated almost completely, due to the closure of the Strait of Gibraltar. The discovery of the phenomenon occurred in 1961,when a strong seismic level of a reflecting type was found, which was going to delineate a geological structure between 100 and 200m deep. This level, called M reflector, faithfully follows the morphology of the current sea floor, suggesting the presence of a level with characteristics of uniformity and high speed of seismic waves. Trials that were carried out ten years later by the oceanographic ship Glomar Challenger, during the 13th campaign of the Deep Sea Drilling Program (DSDP)revealed the nature of the M reflector: it is a level of evaporitic sediments, with thickness up to 3 km.
Samples of sediments taken,including evaporites,soil,and fossil plants,show that about 5.9 million years ago, in the late Miocene, the forerunner of today's Strait of Gibraltar closed and the Mediterranean evaporated and turned into a basin. Mainly dry and deep, whose base in some places reached 3.2 - 4.9 km below the level of the oceans.
The Mediterranean is still a much saltier sea in the North Atlantic since it communicates with this only through the Strait of Gibraltar and it is subject to a high rate of evaporation. All for the closure of the Strait of Gibraltar.
When the strait was reopened(in Pliocene period) the Atlantic waters poured into a relatively narrow channel: this gave rise to cascades of difference in height and power higher than any current waterfall. According to some estimates the filling the Mediterranean may have required no more than a hundred years. Worldwide it causes a rise of 10 m in all the seas of the world. Of the phenomenon of the salinity of the Messinian,there are only poor pages left on History's and Geology's books.

1.1.6 The birth of an island: Sicily

Sicily was created by the movements of the Euroasian and African plaque. Other islands were formed by these movements like: Malta, Cyprus, Sardinia, Corsica, and many others, but Sicily is the biggest of all.
In comparison to other islands in the world, Sicily is one of the youngest because its formation is dated 12000 years ago.
All of these islands, especially Sicily, have witnessed a lot of civilization due to their strategic location, that is the center of the Mediterrean sea, that was the center of the commercial routes. But this same location causes Sicily a lot of troubles beacuse the fact that it is located between two plaques is the main reason that the island suffers of many earthquakes.
Another particularity of Sicily is the presence of carbonates and sulfates, because during the Messinian salinity crisis a lot of water evaporated and the salinity increased. We can prove this by finding them in the gypsum and salt rock mines. Another consequence of the Messinian salinity crisis in Sicily is the presence of animals that originated from Africa, because with the evaporation of the water the land submerged and this created a route for animals to traverse.
We can explain the birth of Sicily even with various myth, but the most famous is the one that talks about Enceladus. Enceladus was an offspring of Gea and a Giant. During the war beetwen the Gods and the Giants, the Gigantomachy, Enceladus tried to run away, but Athena saw him and she thrown him in the center of the Mediterrean sea and after that buried him in a land where with his mouth he formed the volcano Etna and with his right feet formed mount Erice.

1.1.7 Vulcanic islands in the Mediterranean Sea.

Volcanic islands in the Mediterranean Sea are many, we find ,for example, the island of Vulcano and the island of Stromboli.
Vulcano Island in the past Therasia is an Italian island, belonging to the archipelago of the Aeolian Islands near Lipari in Sicily, which houses the anonymous volcano.
The island was born after the merger of some volcanoes where the largest was the volcano of the ditch.
The volcano is still active even if there are no eruptions since 1890.
There are several phenomena that we can record, for example fumaroles and steam jets.
The island is also famous for the presence of hot volcanic muds linked to the sulphurous activity of the island.
Stromboli is an Italian island that, like the island of volcano, belongs to the archipelago of the Aeolian Islands called by its inhabitants "Struògnoli" or "Iddu" for its divine nature linked to its uncontrolled natural phenomena.
It is one of the most famous islands of the Aeolian archipelago and is also an active volcano. It is explosive in nature emitting lavas that do not cause lava flows but accumulations in the mouth of the crater creating more or less conical or dome shaped structures called lava "duomas".
After the lava has accumulated it can burst and an eruptive column of gas and lapilli rises above the volcano, when the thrust of the gas ends that column falls to the sides of the volcano in the form of burning clouds, this phenomenon occurs on the island one hour frequency with the emission of "scoriaceous" bombs, lapilli and ashes.