Everything that concerns the emergence and development of our common home - the Earth, cannot be ignored by everyone who considers himself erudite and civilized. And if during the training everything was quite clear - teachers and teachers (thanks to them), explained well, then with further in-depth - not everything is so smooth. It turns out that some "capital truths" contradict not only the logical state of affairs and common sense, but also indisputable facts. Not all, fortunately, this applies to objects. But geology, with its tangential sciences, is, unfortunately, hooked. Perhaps that is why there are so many specific terms that are beyond the control of ordinary mortals, to make it easier to retouch what experts are unable to explain.
What about those who are interested in the truth
It is much easier for those directly involved in geological sciences. The main thing here is to correctly guess which current or "luminary" to join, everything else is almost decided; even during training.
But what about amateurs who are also interested in the truth. It is the truth, not what is in trend today. They are not interested in either dubious authorities or "generally accepted" thoughts. How should they behave?
And there is probably only one way out, to introduce certain rules (restrictions) - and question everything. Believe in what you do not know well, doubt what you know well. Make friends with the terminology as much as possible. And take into account the opinions of others - it can be decisive. Even the most ridiculous of them is important. It will either show the right path, or warn against the wrong. And the main thing is to rely only on facts.
Everything has its time. So let's decide where to start. Wherever it goes, unfortunately (or fortunately), contradictions (sometimes diametrically opposite) are torn apart. If not mobilists from fixists (and it is still very early to write them off to the archive), then about the origin of carbohydrates - organic and inorganic; the temperature in the center of the planet is predicted from almost absolute zero to hundreds of thousands of degrees and above; the same goes for ... And who to believe? Everyone is sacredly confident that they are right. As the people say: "Each frog praises its swamp." And so that this "swamp" does not "suck in", let us distance ourselves from this with the right to doubt and begin to unravel the tangle. With the hope (necessarily) that this is the thread of Ariadne.
Let's start with what is least realistic to prove, although there is logic in this statement. According to Vladimir Ivanovich Vernadsky (1863-1945) back in the 30s of the last century, the temperature is rapidly decreasing towards the center of the planet. This statement fits into the cosmogonic theory of Otto Yulievich Schmidt (1891 - 1956) about the "cold" formation of planets from a gas-dust cloud. Perhaps this is so, but only with the amendment that this does not apply to our solar system - its components are too different in age. The same Venus, in comparison with other planetary bodies, is much younger - even in human existence it was called a "bearded" planet. Better to draw a parallel with supernova formation. And the substance that lies in the very depths of the planet is most likely to be found in the asteroid belt, or to see the result of its action in regular flares on Mars. But these are all guesses, not even hypotheses. Therefore, over time, you will need to look at them from a different angle.
Further, if possible, we will try to touch the more mundane, accessible "to the touch" and understand the nature of the earth's crust.
What do we know about the bowels of the Earth?
The earth's crust, like a solid and cooled shell of the planet, according to the classical scheme, is divided into three layers: sedimentary, granite and basalt.
The thickness of the sedimentary layer is not the same. It ranges from 0 to 15 km. The thickness of the granite layer is from 5 to 15 km. The basalt layer is 10 to 35 km thick.
All these three layers are separated from the upper mantle by the Mohorovichich line, which determines the thickness of the planet's crust in different places on land and in the oceans. The average thickness of the crust on the continents is 35 km. But in mountainous areas, for example, under the Pamir or Andes, it reaches 70-80 km. Ancient platforms are 30 km thick. A relatively thin layer of the earth's crust beneath the oceans. It reaches a thickness of only 5-6 km. There is a big difference between the continental and oceanic crust. Mainly it is that there is no granite layer under the oceans. If we compare the thickness of the sedimentary layer of the land with the oceanic, then the latter will still be less - in the region of 1 km. Many areas, such as the Pacific Ocean, have no sedimentary layer at all, or in the worst case it is very thin. (The reason, perhaps, lies in his "youth" and too aggressive growth). In the full sense of the word, there is no precipitation in many oceanic faults.
If we talk about the earth's crust, then we mean the hard shell of the entire planet. But in order to understand the essence of the difference between the continental crust and the oceanic crust, it is necessary to analyze in more detail the available data separately about one or another.
The continental crust has an average thickness of 35 km. But it also has a thickness of 70-80 km. This means that there should be places thinner than 35 km. What are the areas of increased and decreased thickness? "As a rule, - noted in special literature - on the continents, the earth's crust is thicker under the young ridges and thinner under the lowlands."
The dissimilarity of processes in the earth's crust
What is the reason for the unevenness thicker than the hardened shell? First of all, one should turn to time. What is older in age, mountain structures or lowlands? How does time affect the evolutionary development of the planet and, in particular, its hard shell?
Let us turn to the conclusions of what V.V. Belousov (1907-1990): "... if it follows from geophysical data that the earth's crust is thicker under young folded zones, thinner under ancient folded zones and even thinner under ancient platforms, then, obviously, it is necessary to conclude that over time there is a decrease in the thickness of the earth's crust. " (Given the specificity of mountain building processes in each geological epoch, this conclusion should probably be questioned).
It has been established that some areas, which were platforms for a long geological time, recently (10-15 million years ago) suddenly regained their mobility and mountains began to grow again within them. They are zones of tectonic activation. This, for example, the Tien Shan, which grew as a result of a significant increase in tectonic vertical movements in the Neogene and Quaternary, whereas before that - throughout the Mesozoic and in the Paleogene - this area was already a platform. Geophysical methods show that the crust in such activation areas is very thick, twice that of the crust on the platforms. "This means that the activation of tectonic movements is associated with an increase in the thickness of the crust" - the conclusion of the same author.
The question is, what depends on what: activation of tectonic movements from an increase in the thickness of the crust, or the thickness of the crust from the activation of tectonic movements?
Simply giving an answer to this question is not so easy to believe in its true meaning. First of all, it is necessary to look into the depths of time and turn to many other data on the evolutionary development of the planet. In addition, a logical approach to deflecting obstacles to research is needed.
Translated from Планета Земля очима дилетанта
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