ShareThe canals of Venice have become shallow, and after the catastrophic earthquake in Turkey and Syria, social networks are discussing and showing how the coastline of the Mediterranean Sea has moved away, exposing the land. Naturally, they started talking practically about the fact that the earth had collided with the celestial axis: the tectonic plates supposedly moved apart, and the water flowed “inside”. Fontanka asked marine geologist and science journalist Konstantin Ranks questions.
Share“Konstantin, there is a transport collapse in Venice, the canals have become shallow, and it is through them that all services move on boats, from ambulances to taxis. Someone says that the drought is to blame, someone – earthquakes at the bottom of the Mediterranean Sea. Who is right?
– What happened in Venice should be clear to Petersburgers. You are suffering from the fact that the wind “blows you water” – floods occur. A northwest wind, uncharacteristic for it, blew on Venice; it does not “inflate” the water, but “blows it out”.
When a strong wind blows from the direction of the Alps on the shallow Venetian lagoon, the water leaves the channels, because they are also small – it will be waist-deep for a tall person. When I heard that the canals had become shallow, I thought that this should be perceived not only as a transport disaster, but also as a good luck for the local authorities – it is possible to remove the accumulated garbage from the canals without any problems. It is only important not to waste time – the wind will soon change, and they will be filled with water, as usual. And now we also need to take care of the piles on which the city stands, their draining is harmful, they can begin to rot. That is, shallowing is not a one-time problem – it again raises questions about the sustainability of Venice.
– You yourself say that we, as Petersburgers, understand this. But the system of protection against floods and shoals, apparently, is fundamentally different?
“Probably [там] it is believed that the southeast wind is more dangerous, at which there is a risk of flooding. They built a protective system of caissons through which air is blown in, they float up and prevent water from the Adriatic Sea from entering the Venetian Lagoon in a larger volume than necessary. Such a system would not protect St. Petersburg, but they do not have the Neva, which is constantly replenished by water from Ladoga, so such flood protection works for Venice. The system was not designed for the northwest wind, for the current situation, when the water is blown out.
– Some scientists also say that after the earthquake in Turkey, a shallowing of the Mediterranean Sea was discovered – off the coast of Cyprus, Malta, Turkey, Lebanon. Theories are put forward according to which, due to the displacement of tectonic plates, voids were formed into which water flows from the Mediterranean Sea.
– You will listen and believe that the earth has opened up and the sea has glassed into the abyss. In fact, this does not happen. Because the pressure inside the earth is much greater than the pressure of the water in the sea. And everything that is inside, at the slightest opportunity to get out, does this. Therefore, volcanoes, even those located at the bottom of the World Ocean under a water column of kilometers, erupt. Huge mid-ocean ridges – mountains on the seabed, formed during the movement of tectonic plates – live their lives under water. Along the diverging boundary of these plates, lava is constantly squeezed out. And she is not stopped by solid water five kilometers high, because inside the pressure is even higher. That is, if the plates moved apart, the pressure from the earth would not allow water to get inside, on the contrary, magma would pour out from there, thereby expanding the boundaries of the ocean. This means that its depth is decreasing and the global sea level is rising.
Mid-ocean ridges push the seabed apart with lava produced during eruptions. And it, in turn, either slowly pushes our continents, or “drives” under the mainland, as in the Pacific Ocean, where it melts and erupts by volcanoes. The whole perimeter of the Pacific Ocean is full of volcanoes and earthquakes.
– Does this mean that the Mediterranean Sea cannot become shallow?
– As the level of water in the World Ocean rises, it will rise in the Mediterranean Sea.
The Italian world-famous volcanoes Vesuvius, Stromboli or Etna are, as they say, flowers, their “stormy life” flows over water and is not a mystery to modern science. Only there are plenty of volcanoes at the bottom of the Mediterranean Sea, they erupt there constantly. Do you know why? Because Africa is approaching the Eurasian continent. Once between the continents there was the Tethys Ocean, and now the stunted Mediterranean Sea is left of it. The African plate continues to move actively, it wants to move the neighboring continent, rushing directly from south to north. So in a few million years the Mediterranean Sea will eventually collapse, new mountains and new volcanoes will grow on the new land. That is, there is no empty space.
The Mediterranean Sea, figuratively speaking, constantly dries up and fills with water from the Atlantic Ocean. So until the Strait of Gibraltar is blocked, it will not become shallow. Although there have already been cases in the geological history of the Mediterranean Sea when its connection with the Atlantic was broken and the sea dried up completely – it turned into a continuous salt desert with volcanoes sticking out of it and a few saline lakes. This, as you probably guess, happened during the periods of glaciation of the Earth, when the global level of the World Ocean fell.
And then, about 5 million years ago, there was a strong tectonic movement, and the “partition” in the form of the Isthmus of Gibraltar collapsed, a cyclopean-sized waterfall formed, which filled the entire Mediterranean Sea again. That is why there are huge salt deposits at its bottom, and unlike all seas, it has a fairly high temperature to the very bottom – and the depth in some places reaches more than 4 kilometers. It is saltier than the ocean, for people suffering from psoriasis, it is a therapeutic bath, it is more useful to swim in it than, for example, in the Atlantic Ocean.
— The earthquake in Turkey has predictably become a pretext for creating apocalyptic scenarios. Theories of shallowing not just one sea, but the entire World Ocean have already appeared. Is it possible?
Where will this water from the planet go? Only in one case can the water level in the World Ocean decrease – when new glaciers begin to form. And we have, as we remember, global warming: glaciers are melting, the water level is rising – and it is its increase, not a decrease, that is diagnosed throughout the planet. Moreover, due to the rotation of the earth, this is most noticeable as you approach the equator. Centrifugal force moves the volume of air in the atmosphere closer to the equator. Water is also a mobile substance, therefore, in the equatorial zones, the rise in sea level is higher than in the north. All island states – Tahiti, Cocos Islands, Marshall Islands, Maldives – are sounding the alarm, water is gradually taking away huge areas of land from them.
– Okay, the opposite scenario: a global flood on the threshold?
– On one of the Solomon Islands, located between New Guinea and New Zealand, there is a legend similar to the legend of Troy: in order for the hero to rescue his beautiful wife, locked up on the island, the sorcerer ordered to plant taro there, and when it puts out new leaves, immediately grab wife and leave, because the island will immediately go under water. The hero planted taro when it put out new leaves, took his wife, got into a boat with her, and before his eyes the sea swallowed up the island. This story was a local folk tale-horror story. and when they began to explore the underwater world, they discovered that such an island, which had gone under water, really existed. And not alone. We discovered an underwater canyon (such a large ravine under water, more than 5 kilometers deep), which absorbed many islands even in weak, almost imperceptible earthquakes – they sank like a landslide into it almost before our eyes. Yes, water has been conquering territories for a long time, and not vice versa.
— But why can’t there be similar processes in the part of the Mediterranean Sea, located next to the earthquake? Suppose a tectonic fault formed a void that was filled with water.
– Because these tectonic plates do not diverge there, but, on the contrary, converge. They collided like ice floes during an ice drift: the African plate pushes from the south, the Arabian plate from the east, the Eurasian plate from the north, and between them, like a rhombus, there is a small Anatolian plate, which is crushed by everyone.
Are there regions in Russia that are at risk of being under water?
The most famous is Lake Baikal. This is one of the most seismically dangerous places in the Russian Federation. The lake was formed inside a geological fault – and to the north this crack in the earth tends to expand. Therefore, do not be surprised when they say to you: “If you want to see the future ocean, go to Baikal.”
The same process is taking place in Africa, in a fault located in the East African Rift Zone at the site of modern Lakes Kivu and Tanganyika. This rift continues to widen. That is, once Africa will also split. It’s okay – the continents once split, once they are collected. And so it will continue for many hundreds of millions of years. The earth is not old yet.
Irina Baglikova, Fontanka.ru
