The result of a hypocollision
The stitch line between the plates which have collided—the
Africa-Arabia block against Eurasia—is very clear in Calabria,
in the Apennines, the Dinarid Alps (North Albania and former Yougoslavia).
It is well marked between the Hellenides (the rest of Albania,
Macedonia, Greece) and the Near-East where
there is the forming of the Egean Arc.
Those lines are clearly marked by the rocks
which compose them (basalte...),
torn away from the oceanic crust of the descending plates in the subduction zone
between Africa and Eurasia
and trapped in the continents under the form of overlapping scales
during their collision.
How deep!
The deplorable accident of the Charm el Cheikh
plane, in Egypt, in January 2004, in the Gulf of Aqaba,
6,000 ft deep (1830 m), has brought the cable-layers, specialists
of oceanic depths, to locate the black boxes of the
damaged plane with great difficulty.
In fact, the Red Sea, 124 to 186 miles wide
(200 to 300 km), is in some places 9,967 ft deep
(3,040 m)!
Its floor is being built from a central recent oceanic rift, and
this accretion causes a pressure on Africa, to
the West, and Arabia, to the East. This young ocean is the unexpected
study ground for the mechanism of the forming of an ocean.
|
What connection is there?
(Click on the map to get a full-screen picture)
Use your Browser to come back to this Page (Previous)
This ocanic rift id linked, to the South-West,
with the low floors or intracontinental rifts
of East Africa, to the East, and, to the North-East, the fault corridor
which starts in the Gulf of Aqaba,
reaches the Dead Sea, the Jordan valley, the Tiberiade Lake, the trenches
of the Bekaa and the Ghab in Syria, and reaches
the slopes of the Taurus Mounts in Turkey, through the Levant fault.
There, we have:
the limits between the Arabic plate and the African plate,
which were geologically joined,
the explanation of the sliding of the Arabic plate towards the North-East,
1 5/8 inch
(4 cm) every year, alonge the Dead Sea fault
and the strong seismic activity in this long corridor
(Alep in Syrie in 1872: 7,2—Beyruth in
Lebanon in 1956: 6—Israel in 2004: 5,1),
the origin of the forming of the Caucasus range,
because the Arabic plate acts like a punch
which distorts Eurasia and pushes Iran and Turkey sideways along the
North-Anatolian fault.
The Red Sea is also communicating with the Mediterranean Sea, through
the Suez Gulf, which is shallow—262 ft
(80 m)—at the end of which has been dug the Suez Canal,
100 miles long (161 km), which was completed in 1869.
The Turkisk microplate
Being pushed by the African and Arabic plates,
the Turkish microplte is blocked along the edge of the
Eurasian plate, and it slides along the North-Anatolian fault which
ranges from the Egean Sea as far as Iran.
It forms a fold on the Anatolian peninsula, and generates the collision
range of Caucasus, the seismic activity of
which is well-marked (Spitak in Armenia in 1988: 7—Bam in Iran
in 2004: 6,3).
It is sucked towards the West because of the progressive plunging of the Egean
plate on which Greece lies, among others.
It is along the North-Anatolian fault that major earthquakes have come
in succesion, during the past sixty-five years
(Erzincan in 1992: 7,1—Izmit in 1999: 7,4).
This plate moves in portions 62 to 93 miles
(100 to 150 km), with two blocks moving 1 inch apart
(2·5 cm) per year,
viz. 20 times faster than the active faults in France. The accumulated
forces are released abruptly on one of the blocks and,
the more time has elapsed, the more energy is accumulated, the stronger
the discharge of energy is.
The tensions move towards the West in the Sea of Marmara, and Istanbul
is all the more threatened as this fault
has not been moving for a long time under the city.
The Egean microplate
The Egean microplate is also located between
the African plate and the Eurasian plate. In this case,
to the South of Crete, a ridge has been found, which is 124 miles
(200 km) wide, and 1,180 miles (1900 km) long,
from Apulia (the Italien Puglie) to Cyprus. To the South of this ridge,
there is principally an abyssal plain,
which is invaded by the alluvial deposits of the Nile, covering an area
of 38,600 sq. miles
(100 000 km2).
Being pushed towards the North by the activity of the ridge,
the rest of the oceanic crust of the Tethys moves by subduction
under the Egean plate, causing the forming of a double island arc
oriented North-West–South-East:
one is outside, it is sedimentary, non-volcanic: Cythere, Crete,
Kassos, Karpathos and Rhodes.
the other is inside, with andesite volcanoes caused by subduction:
the Methana peninsula, the islands of Poros, Milo,
Santorino (with its cataclysmal eruption, in 500 B.C., which destroyed
the Minoan civilization), and Nísiros.
Double faults, oriented North-West—South-East and North-East—South-West
make like a draughtboard of islands
in which the seismisc activity is very important, with seismic centres
155 miles (250 km) deep.
|
In 2000 B.C., Sodome et Gomorrhe, located on the banks of the Dead Sea,
were destroyed by an earthquake, a volcanic
eruption, and they were submerged by the water of the Mediterranean Sea
which, because of the sinking of the Dead
Sea, was swallowed down into this depression.
Then, the water evaporated and an important amount of salt was deposited,
Loth's salt–Loth, the only survivor
of Sodome and Gomorrhe, together with his son. The amount of salf is high,
26 %, and this is perhaps a happy thing
for bad swimmers, who do not have to fear they will be changed into salt statues,
but it does not help the development of life.
The sea, 2623 ft (800 m) deep, is located at the lowest level
on Earth (–1311 ft, or –400 m), and
it is becoming lower and lower regularly.
Downstream, the water of the Jordan River which flows into it is pumped
for cultures, and a canal, several kilometres long,
also plays a part in the dying of this sea which is now parted
into two parts by a strip of land.
The Jordan, which has its springs
in the Antiliban, flows towards the South and goes through the
soft water lake of Tiberiade, to flow into the Dead Sea. The springs
of the Jordan are located in Lebanon, in Syria
(Banias) and above all in Israel, with some fifty springs and artesian wells,
Dan being the more abundant with
8,810,000 gallons (40 000 m3) per hour,
in winter time as well as during the summer.
There is a project to build a canal from the Red Sea to the Dead Sea,
or an underground canal from the Mediterranean Sea
to the Dead Sea, and this could salvage this sea.
|
|
The East basin of the Mediterranean Sea,
TECTONICS : THE EARTH
Haut de Page • [Top of Page]
Part 1: The Mediterranean Sea: a jigsaw puzzle • [Première Partie : La Méditerranée : un puzzle]