MOSCOW, February 12 - RIA Novosti. American geologists say that the inner core of the Earth could not have arisen 4.2 billion years ago in the form in which scientists imagine it today, since this is impossible from the point of view of physics, according to an article published in the journal EPS Letters.

“If the core of the young Earth consisted entirely of pure, homogeneous liquid, then the inner nucleolus should not exist in principle, since this matter could not cool to the temperatures at which its formation was possible. Accordingly, in this case the core may be heterogeneous composition, and the question arises of how it became like this. This is the paradox we discovered,” says James Van Orman from Case Western Reserve University in Cleveland (USA).

In the distant past, the Earth's core was completely liquid, and did not consist of two or three, as some geologists now suggest, layers - an inner metallic core and a surrounding melt of iron and lighter elements.

In this state, the core quickly cooled and lost energy, which led to a weakening of the magnetic field it generated. After some time, this process reached a certain critical point, and the central part of the nucleus “froze”, turning into a solid metal nucleolus, which was accompanied by a surge and increase in the strength of the magnetic field.

The time of this transition is extremely important for geologists, as it allows us to roughly estimate at what speed the Earth’s core is cooling today and how long the magnetic “shield” of our planet will last, protecting us from the action of cosmic rays, and the Earth’s atmosphere from the solar wind.

Now, as Van Orman notes, most scientists believe that this happened in the first moments of the Earth's life due to a phenomenon, an analogue of which can be found in the planet's atmosphere or in soda machines in fast food restaurants.

Physicists have long discovered that some liquids, including water, remain liquid at temperatures noticeably below the freezing point, if there are no impurities, microscopic ice crystals or powerful vibrations inside. If you shake it easily or drop a speck of dust into it, then such a liquid freezes almost instantly.

Something similar, according to geologists, happened about 4.2 billion years ago inside the Earth's core, when part of it suddenly crystallized. Van Orman and his colleagues tried to reproduce this process using computer models of the planet's interior.

These calculations unexpectedly showed that the Earth's inner core should not exist. It turned out that the process of crystallization of its rocks is very different from the way water and other supercooled liquids behave - this requires a huge temperature difference, more than a thousand kelvins, and the impressive size of a “speck of dust”, whose diameter should be about 20-45 kilometers.

As a result, two scenarios are most likely - either the planet’s core should have frozen completely, or it should still have remained completely liquid. Both are untrue, since the Earth does have an inner solid and outer liquid core.

In other words, scientists do not yet have an answer to this question. Van Orman and his colleagues invite all geologists on Earth to think about how a fairly large “piece” of iron could form in the planet’s mantle and “sink” into its core, or to find some other mechanism that would explain how it split into two parts.

The earth's core includes two layers with a boundary zone between them: the outer liquid shell of the core reaches a thickness of 2266 kilometers, beneath it there is a massive dense core, the diameter of which is estimated to reach 1300 km. The transition zone has a non-uniform thickness and gradually hardens, turning into the inner core. At the surface of the upper layer, the temperature is around 5960 degrees Celsius, although this data is considered approximate.

Approximate composition of the outer core and methods for its determination

Very little is still known about the composition of even the outer layer of the earth's core, since it is not possible to obtain samples for study. The main elements that may make up the outer core of our planet are iron and nickel. Scientists came to this hypothesis as a result of analyzing the composition of meteorites, since wanderers from space are fragments of the nuclei of asteroids and other planets.

Nevertheless, meteorites cannot be considered absolutely identical in chemical composition, since the original cosmic bodies were much smaller in size than the Earth. After much research, scientists came to the conclusion that the liquid part of the nuclear substance is highly diluted with other elements, including sulfur. This explains its lower density than that of iron-nickel alloys.

What happens on the outer core of the planet?

The outer surface of the core at the boundary with the mantle is heterogeneous. Scientists suggest that it has different thicknesses, forming a peculiar internal relief. This is explained by the constant mixing of heterogeneous deep substances. They differ in chemical composition and also have different densities, so the thickness of the boundary between the core and the mantle can vary from 150 to 350 km.

Science fiction writers of previous years in their works described a journey to the center of the Earth through deep caves and underground passages. Is this really possible? Alas, the pressure on the surface of the core exceeds 113 million atmospheres. This means that any cave would have “slammed shut” tightly even at the stage of approaching the mantle. This explains why there are no caves on our planet deeper than at least 1 km.

How do you study the outer layer of the nucleus?

Scientists can judge what the core looks like and what it consists of by monitoring seismic activity. For example, it was found that the outer and inner layers rotate in different directions under the influence of a magnetic field. The Earth's core conceals dozens more unsolved mysteries and awaits new fundamental discoveries.

The Earth, along with other bodies in the Solar System, was formed from a cold gas and dust cloud through the accretion of its constituent particles. After the emergence of the planet, a completely new stage of its development began, which in science is usually called pre-geological.
The name of the period is due to the fact that the earliest evidence of past processes - igneous or volcanic rocks - is not older than 4 billion years. Only scientists can study them today.
The pre-geological stage of the Earth’s development is still fraught with many mysteries. It covers a period of 0.9 billion years and is characterized by widespread volcanism on the planet with the release of gases and water vapor. It was at this time that the process of separation of the Earth into its main shells began - the core, mantle, crust and atmosphere. It is assumed that this process was provoked by intense meteorite bombardment of our planet and the melting of its individual parts.
One of the key events in the history of the Earth was the formation of its inner core. This probably happened during the pre-geological stage of the planet’s development, when all matter was divided into two main geospheres - the core and the mantle.
Unfortunately, a reliable theory about the formation of the earth’s core, which would be confirmed by serious scientific information and evidence, does not yet exist. How did the Earth's core form? Scientists offer two main hypotheses to answer this question.
According to the first version, the matter immediately after the emergence of the Earth was homogeneous.
It consisted entirely of microparticles that can be observed today in meteorites. But after a certain period of time, this primary homogeneous mass was divided into a heavy core, into which all the iron had flowed, and a lighter silicate mantle. In other words, drops of molten iron and the accompanying heavy chemical compounds settled to the center of our planet and formed a core there, which remains largely molten to this day. As heavy elements tended to the center of the Earth, light slags, on the contrary, floated upward - to the outer layers of the planet. Today, these light elements make up the upper mantle and crust.
Why did such differentiation of matter occur? It is believed that immediately after the completion of the process of its formation, the Earth began to warm up intensively, primarily due to the energy released during the gravitational accumulation of particles, as well as due to the energy of the radioactive decay of individual chemical elements.
Additional heating of the planet and the formation of an iron-nickel alloy, which, due to its significant specific gravity, gradually sank to the center of the Earth, was facilitated by the alleged meteorite bombardment.
However, this hypothesis faces some difficulties. For example, it is not entirely clear how an iron-nickel alloy, even in a liquid state, was able to descend more than a thousand kilometers and reach the region of the planet’s core.
In accordance with the second hypothesis, the Earth's core was formed from iron meteorites that collided with the surface of the planet, and later it was overgrown with a silicate shell of stone meteorites and formed the mantle.

There is a serious flaw in this hypothesis. In this situation, iron and stone meteorites should exist separately in outer space. Modern research shows that iron meteorites could only have arisen in the depths of a planet that disintegrated under significant pressure, that is, after the formation of our Solar System and all the planets.
The first version seems more logical, since it provides for a dynamic boundary between the Earth's core and the mantle. This means that the process of division of matter between them could continue on the planet for a very long time, thereby exerting a great influence on the further evolution of the Earth.
Thus, if we take the first hypothesis of the formation of the planet’s core as a basis, the process of differentiation of matter lasted approximately 1.6 billion years. Due to gravitational differentiation and radioactive decay, the separation of matter was ensured.
Heavy elements sank only to a depth below which the substance was so viscous that iron could no longer sink. As a result of this process, a very dense and heavy annular layer of molten iron and its oxide was formed. It was located above the lighter material of the primordial core of our planet. Next, a light silicate substance was squeezed out from the center of the Earth. Moreover, it was displaced at the equator, which may have marked the beginning of the asymmetry of the planet.
It is assumed that during the formation of the iron core of the Earth, a significant decrease in the volume of the planet occurred, as a result of which its surface has now decreased. The light elements and their compounds that “floated” to the surface formed a thin primary crust, which, like all terrestrial planets, consisted of volcanic basalts, overlain by a thick layer of sediment.
However, it is not possible to find living geological evidence of past processes associated with the formation of the earth's core and mantle. As already noted, the oldest rocks on planet Earth are about 4 billion years old. Most likely, at the beginning of the planet’s evolution, under the influence of high temperatures and pressures, primary basalts metamorphosed, melted and transformed into the granite-gneiss rocks known to us.
What is the core of our planet, which was probably formed at the earliest stages of the Earth’s development? It consists of outer and inner shells. According to scientific assumptions, at a depth of 2900-5100 km there is an outer core, which in its physical properties is close to liquid.
The outer core is a stream of molten iron and nickel that conducts electricity well. It is with this core that scientists associate the origin of the earth's magnetic field. The remaining 1,270 km gap to the center of the Earth is occupied by the inner core, which is 80% iron and 20% silicon dioxide.
The inner core is hard and hot. If the outer is directly connected to the mantle, then the inner core of the Earth exists on its own. Its hardness, despite the high temperatures, is ensured by the gigantic pressure in the center of the planet, which can reach 3 million atmospheres.
Many chemical elements transform into a metallic state as a result. Therefore, it was even suggested that the inner core of the Earth consists of metallic hydrogen.
The dense inner core has a serious impact on the life of our planet. The planetary gravitational field is concentrated in it, which keeps light gas shells, the hydrosphere and geosphere layers of the Earth from scattering.
Probably, such a field was characteristic of the core from the moment the planet formed, whatever its chemical composition and structure might have been then. It contributed to the contraction of the formed particles towards the center.
Nevertheless, the origin of the core and the study of the internal structure of the Earth is the most pressing problem for scientists who are closely involved in the study of the geological history of our planet. There is still a long way to go before a final solution to this issue is achieved. To avoid various contradictions, modern science has accepted the hypothesis that the process of core formation began to occur simultaneously with the formation of the Earth.

Countless ideas have been expressed about the structure of the Earth's core. Dmitry Ivanovich Sokolov, a Russian geologist and academician, said that substances inside the Earth are distributed like slag and metal in a smelting furnace.

This figurative comparison has been confirmed more than once. Scientists carefully studied iron meteorites arriving from space, considering them fragments of the core of a disintegrated planet. This means that the Earth’s core should also consist of heavy iron in a molten state.

In 1922, the Norwegian geochemist Victor Moritz Goldschmidt put forward the idea of ​​a general stratification of the Earth's substance at a time when the entire planet was in a liquid state. He derived this by analogy with the metallurgical process studied in steel mills. “In the stage of liquid melt,” he said, “the substance of the Earth was divided into three immiscible liquids - silicate, sulfide and metallic. With further cooling, these liquids formed the main shells of the Earth - the crust, mantle and iron core!

However, closer to our time, the idea of ​​a “hot” origin of our planet was increasingly inferior to a “cold” creation. And in 1939, Lodochnikov proposed a different picture of the formation of the Earth’s interior. By this time, the idea of ​​phase transitions of matter was already known. Lodochnikov suggested that phase changes in matter intensify with increasing depth, as a result of which the matter is divided into shells. In this case, the core does not necessarily have to be iron. It may consist of overconsolidated silicate rocks that are in a “metallic” state. This idea was picked up and developed in 1948 by the Finnish scientist V. Ramsey. It turned out that although the Earth’s core has a different physical state than the mantle, there is no reason to consider it to be composed of iron. After all, overconsolidated olivine could be as heavy as metal...

This is how two mutually exclusive hypotheses about the composition of the nucleus emerged. One is developed on the basis of E. Wichert's ideas about an iron-nickel alloy with small additions of light elements as a material for the Earth's core. And the second - proposed by V.N. Lodochnikov and developed by V. Ramsey, which states that the composition of the core does not differ from the composition of the mantle, but the substance in it is in a particularly dense metallized state.

To decide which way the scales should tip, scientists from many countries carried out experiments in laboratories and counted and counted, comparing the results of their calculations with what seismic studies and laboratory experiments showed.

In the sixties, experts finally came to the conclusion: the hypothesis of metallization of silicates, at the pressures and temperatures prevailing in the core, is not confirmed! Moreover, the studies carried out convincingly proved that the center of our planet should contain at least eighty percent of the total iron reserve... So, after all, the Earth’s core is iron? Iron, but not quite. Pure metal or pure metal alloy compressed at the center of the planet would be too heavy for Earth. Therefore, it must be assumed that the material of the outer core consists of compounds of iron with lighter elements - oxygen, aluminum, silicon or sulfur, which are most common in the earth's crust. But which ones specifically? This is unknown.

And so the Russian scientist Oleg Georgievich Sorokhtin undertook a new study. Let's try to follow the course of his reasoning in a simplified form. Based on the latest achievements of geological science, the Soviet scientist concludes that in the first period of formation the Earth was most likely more or less homogeneous. All its substance was distributed approximately equally throughout the entire volume.

However, over time, heavier elements, such as iron, began to sink, so to speak, “sinking” into the mantle, going deeper and deeper towards the center of the planet. If this is so, then, comparing young and old rocks, one can expect that in young rocks there will be a lower content of heavy elements, such as iron, which is widespread in the substance of the Earth.

The study of ancient lavas confirmed this assumption. However, the Earth's core cannot be purely iron. It's too light for that.

What was iron's companion on its way to the center? The scientist tried many elements. But some did not dissolve well in the melt, while others turned out to be incompatible. And then Sorokhtin had a thought: wasn’t the most common element, oxygen, a companion of iron?

True, calculations showed that the compound of iron and oxygen - iron oxide - seems to be too light for the nucleus. But under conditions of compression and heating in the depths, iron oxide must also undergo phase changes. Under the conditions existing near the center of the Earth, only two iron atoms are able to hold one oxygen atom. This means that the density of the resulting oxide will become greater...

And again calculations, calculations. But what a satisfaction when the result obtained showed that the density and mass of the earth’s core, built from iron oxide that has undergone phase changes, gives exactly the value required by the modern model of the core!

Here it is - a modern and, perhaps, the most plausible model of our planet in the entire history of its search. “The outer core of the Earth consists of the oxide of the monovalent iron phase Fe2O, and the inner core is made of metallic iron or an alloy of iron and nickel,” writes Oleg Georgievich Sorokhtin in his book. “The transition layer F between the inner and outer cores can be considered to consist of iron sulfide - troillite FeS.”

Many outstanding geologists and geophysicists, oceanologists and seismologists - representatives of literally all branches of science that study the planet - are taking part in the creation of the modern hypothesis about the release of the core from the primary substance of the Earth. The processes of tectonic development of the Earth, according to scientists, will continue in the depths for quite a long time, at least our planet has another couple of billion years ahead. Only after this immeasurable period of time will the Earth cool down and turn into a dead cosmic body. But what will happen by this time?..

How old is humanity? A million, two, well, two and a half. And during this period, people not only got up from all fours, tamed fire and understood how to extract energy from an atom, they sent people into space, automata to other planets of the solar system and mastered near space for technical needs.

The exploration and then the use of the deep bowels of our own planet is a program that is already knocking on the door of scientific progress.

Why has the earth's core not cooled down and remained heated to a temperature of approximately 6000°C for 4.5 billion years? The question is extremely complex, to which, moreover, science cannot give a 100% accurate and intelligible answer. However, there are objective reasons for this.

Excessive secrecy

The excessive, so to speak, mystery of the earth's core is associated with two factors. Firstly, no one knows for sure how, when and under what circumstances it was formed - this happened during the formation of the proto-earth or already in the early stages of the existence of the formed planet - all this is a big mystery. Secondly, it is absolutely impossible to get samples from the earth’s core - no one knows for sure what it consists of. Moreover, all the data that we know about the kernel is collected using indirect methods and models.

Why does the Earth's core remain hot?

To try to understand why the earth's core does not cool down for such a long time, you first need to understand what caused it to heat up initially. The interior of our planet, like that of any other planet, is heterogeneous; they represent relatively clearly demarcated layers of different densities. But this was not always the case: heavy elements slowly sank down, forming the internal and external core, while light elements were forced to the top, forming the mantle and the earth’s crust. This process proceeds extremely slowly and is accompanied by the release of heat. However, this was not the main reason for the heating. The entire mass of the Earth presses with enormous force on its center, producing a phenomenal pressure of approximately 360 GPa (3.7 million atmospheres), as a result of which the decay of long-lived radioactive elements contained in the iron-silicon-nickel core began to occur, which was accompanied by colossal emissions of heat .

An additional source of heating is the kinetic energy generated as a result of friction between different layers (each layer rotates independently of the other): the inner core with the outer and the outer with the mantle.

The interior of the planet (the proportions are not respected). The friction between the three inner layers serves as an additional source of heating.

Based on the above, we can conclude that the Earth and in particular its bowels are a self-sufficient machine that heats itself. But this naturally cannot continue forever: the reserves of radioactive elements inside the core are slowly disappearing and there will no longer be anything to maintain the temperature.

It's getting cold!

In fact, the cooling process has already begun a very long time ago, but it proceeds extremely slowly - at a fraction of a degree per century. According to rough estimates, at least 1 billion years will pass before the core cools completely and chemical and other reactions in it cease.

Short answer: The earth, and in particular the earth's core, is a self-sufficient machine that heats itself. The entire mass of the planet presses on its center, producing phenomenal pressure and thereby triggering the process of decay of radioactive elements, as a result of which heat is released.