According to recent research by German and Portuguese experts published in the Columns of Geology, a journal of the American Geographical Society, geographic fault lines could cut off the Mediterranean Sea from the Atlantic Ocean. The following millennia completely reshaped the surrounding landmasses.
The Earth's crust is made up of pieces, and because of its movement, continents break apart and form. The movement of geological plates sliding apart and sliding under each other is called the Wilson cycle, named after Canadian geologist John Tuzo Wilson, who described the logic of tectonic processes in 1968.
Wilson had the nail on the head that there was a fault line in the middle of the Atlantic Ocean, so his theory included not only the continents, but also the oceans that opened up and disappeared between them. One of the decisive moments in the cycle is when
One piece of crust slides under another, melting and pressing on the Earth's mantle.
The planet's largest ocean, the Pacific Ocean, is currently shrinking, as the tectonic plates surrounding it sink. In these areas, called subduction zones, there are areas called rings of fire, where earthquakes and volcanic eruptions are common.
On the other hand, the coasts of the Atlantic Ocean subside by 4 cm per year, but there are also subduction zones here. One of them extends near the Lesser Antilles, and the other extends at the Scotia Plate, which extends between South America and Antarctica. The third is the Gibraltar Arc, which culminates at the junction of the Eurasian and African plates, and appears to be currently stationary.
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If the Strait of Gibraltar was closed, the Mediterranean Sea would dry up within a few thousand years, according to calculations. This happened once before, 5.8 million years ago, and left behind large layers of salt. There was land between Africa and Europe about half a million years ago, then 5.33 million years ago, the natural barrier broke again and was filled in within a few years by the largest flood ever, creating the current Mediterranean Sea.
The fate of the Strait of Gibraltar is of particular importance. The possibility of it closing again is not a new theory and sparks heated debate. The new study in question adds to the discussion of the issue that the fate of the Strait depends on the development of the subduction zone in Gibraltar – while on its inner side Africa moves one centimeter northward every year, and the activity on the side facing the Atlantic Ocean is unclear.
According to researchers, the area is already active, and one evidence of this is the Lisbon earthquake of 1755, which had a magnitude of 8.5-9 and killed 12 thousand people, one of the strongest earthquakes recorded. The Portuguese capital is shaken by a strong earthquake every two or three centuries. Therefore, researchers warn that local residents
For this recurring event.
The process is currently very slow, because the Atlantic plate is one of the oldest pieces of this Earth's crust, and therefore very rigid. The arc of the Gibraltar subduction zone facing the ocean is narrow, and at the same time it will overcome the plate and move towards it after about twenty million years, and then the process will accelerate and continue. The cycle begins with a new season, during which the Atlantic Ocean begins to shrink instead of grow. All this is important because it will involve increased seismic activity, and on the other hand, if there are still people in the area, they will be the first to notice the creation of the subduction zone.
(Cover photo: Gibraltar on November 30, 2018. Photo: Arthur Fedak/NoorPhoto/Getty Images)
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