To be able to determine what and where of value is on the planet, it is important to know how it turned out there. Let's consider some possible stages in the formation of the face of the Earth. Take at least such a primitive example for comparison, the same chicken egg. At low temperatures, it freezes and breaks the shell despite its relative thickness, which is greater than the thickness of the earth's crust. Of course, this example should not be taken seriously, since the freezing process does not occur inside the planet, leading to the expansion of the contents. The rupture of the egg shell when the liquid freezes only clearly shows how the integrity of the shell is broken when the contents inside the substance expand.
And despite the primitiveness of the given example, it is a vivid example of proof of the phenomena taking place with the earth's crust.
The increase in the size of the planet is only due to the oceans
The emergence of intra-planetary pressure puts the integrity of the petrified earth shell into a critical position. A solid physical body is not rubber, it is capable of stretching. The earth's crust, despite its many thousand-meter thickness, does not withstand elastic stresses and breaks, breaks in the weakest places, in the places where tectonic forces develop. The torn parts never merge, but on the contrary, they diverge further and further. And depending on the nature of the processes occurring in the depths of the upper mantle, it accordingly affects the consequences in the rupture area itself: either this place remains the deepest depression, or it is immediately filled.
The fate of the place of rupture in the earth's crust is determined by the time of the geological development of the planet. Probably, at the present time, the deepest depressions similar to oceanic ones cannot arise on the continents, just as in the Archean period separate water basins, deepened into the earth's crust, could not arise. And the time since then has been counted in billions of years. One can imagine how much earthly heat has evaporated into outer space without a trace. The evaporation of heat had a tremendous impact on the formation of the inner structure of the planet, especially the area of the upper mantle.
The upper mantle at the present time is not at all what it was during the formation of the continents. And the thickness of the earth's crust has undergone significant changes.
They say that understanding the vital activity of the upper mantle region and its influence on the formation of the earth's crust is of very great vital economic importance. This is true and quite natural. However, it should be noted that this time, when the earth's crust (meaning the continental one) was completely and completely dependent on the activity of the upper mantle, has already passed and has passed irrevocably.
Now the area of the upper mantle itself becomes similar to the earth's crust. It is no longer a supplier of building materials for the continents, despite the fact that it lies directly beneath them. Currently, everything is aimed at building the ocean floor and all kinds of superstructures on it. The continents are currently experiencing only an echo of those distant times of stormy deeds that have moved to the area of the ocean floor. And even then, by their nature of action, the forces that form the earth's crust are in many respects distinguishable from the previous ones. With great difficulty, it is possible to push natural superstructures to the surface, despite the fact that such material accumulates no less than before. Most of this material remains in "warehouses". Only in abundant quantities accumulated, is it able to come to the surface, creating the largest structures like the Mid-Oceanic ridges.
Volcanic activity on the continents is just a vent for the ventilation of the inner-planetary laboratory-kitchen. They no longer play any significant role in shaping the external appearance of the planet. Their future is very unenviable and goes on fading all the time. If in the past, somewhere in the Archean, they were so active, modern continents would hardly exist. And it seems to us that they are currently very intense and threatening.
One can be convinced of the conclusion about the decline in volcanic activity on the continents by following the traces of long extinct volcanoes. The situation is different at the bottom of the oceans. As already mentioned, all their activities have been transferred only there now and beyond.
Change of priorities in the search for fossils
Why does a person strive for knowledge of the secrets of nature and its laws? The answer is very simple: to reap the benefits for your life. Nature gives him invaluable material wealth, but does not give him an endless stream, but in certain portions, which are clearly not always enough. The more the development of human society, the more its increase, the more the need for material resources increases. And these were laid in the earth's crust in different ways about inaccessibility. The more available are exhausted or are already being exhausted. The need is proportional to the development of society. If you use only the old methods of prospecting for minerals, then industrial famine will come in the end. What then? But since the planet's wealth is inexhaustible, the whole difficulty in extracting them will lie in new methods of identifying the occurrence of such, in the ability to determine the place in the earth's crust where they are hidden. Until now, the mainland crust is the supplier of the necessary values.
Practice shows that in the end the most accessible places on the continents can be completely depleted. There remain two directions of searching for valuable raw materials: hard-to-reach areas on the continents and at the bottom of the oceans.
But in order to determine the place of occurrence of minerals in hard-to-reach places on the continents, deep knowledge of the processes of their formation is required. A complete understanding of the mechanism of mass motion during the differentiation of matter in the zone melting zone at that other stage of the geological development of the earth's crust is required. After all, the earth's crust is a multistage aggregate of territorial areas of the firmament, sometimes of enormous size. Speaking of this, we mean the continental type of crust, separate from the oceanic one.
How to understand the meaning of the stated thought? At first, this formulation seems incredible. In the literal sense of the formulation, it is clear that the modern continental crust is a heterogeneous junction of sites of different ages.
Vertical determination of age, selectivity of formation of deposits
Undoubtedly, if this formulation fell into the hands of any scientist, it would have caused indignation, etc. After all, the antiquity or youth of certain geological deposits in science is usually counted from the surface of the earth in depth. The deeper the rocks lie, the older they are. This is quite true, and no one denies it. The other side of the coin is the same - it is the horizontal reading. For some reason, this side of the coin is not given proper attention as a reference in depth. Perhaps she remains above suspicion. And therefore, scientists are repeatedly puzzled by the position that, according to the vertical determination of age, it is not always possible to find rocks, for example, Precambrian deposits. In some places they lie at a certain depth, in others - deeper, and in some they are completely absent. This example is inherent in any period.
Doesn't this situation raise a legitimate question: why is this so? Yes, quite naturally. However, it may seem that such a formulation of the question is not given serious attention, thinking is not strained in search of an answer.
And the very interpretation of age deposits is so vague that in essence it does not give any specific ideas about the nature of this or that deposit, except for the time of their occurrence: Precambrian, Devonian, Carboniferous, Cretaceous, Tertiary, etc. only one question: where could these deposits come from, and you can be sure that the answer would not have followed with complete clarity. After all, geological deposits of any period are not a thin layer of dust, but sometimes rather large strata of rocks. And here it is no longer possible to follow a template, they say, these sedimentary rocks are the product of the destruction of bedrocks. In an extreme case, one could agree with such a formulation, if there was a conversation about sedimentary rocks that directly lie on the bedrock type of the crystalline basement. But after all, various layering in bedding is considered and determined by age. How can you imagine the origin of Cretaceous deposits if they are located between thick layers of different rocks and a completely different chemical and mineralogical composition?
Of course, the answer will follow immediately: of marine origin. But modern liners sail the oceans and thoroughly explore it. Do you find similar places of Cretaceous deposits?
Moreover, it is of marine origin. Little because water itself does not generate this sedimentary material. And even if it was dissolved in water, then the solution itself got into the water basin only from the deep bowels of the planet.
This is why a formulaic approach to the nature of sedimentary rocks does not reveal the truth and does not advance our concepts to subsequent knowledge. And all these are grains of which the earth's crust consists.
Translated from Про формування планети - важливість пізнання процесів