What is the core of the earth. Scientists: The Earth's inner core should not exist. Recreating conditions in the Earth's core

In what time immemorial did this happen? All these questions have worried humanity for a long time. And many scientists wanted to quickly find out what was there in the depths? But it turned out that learning all this is not so easy. After all, even today, having all the modern devices for conducting all kinds of research, humanity is able to drill wells into the depths of only some fifteen kilometers - no more. And for full-fledged and comprehensive experiments, the required depth should be an order of magnitude greater. Therefore, scientists have to calculate how the Earth's core was formed using a variety of high-precision instruments.

Exploring the Earth

Since ancient times, people have studied naturally exposed rocks. Cliffs and mountain slopes, steep banks of rivers and seas... Here you can see with your own eyes what existed probably millions of years ago. And in some suitable places, wells are being drilled. One of these is at its depth - fifteen thousand meters. The mines that people dig to also help study the inner Core, of course, they cannot “get” it. But from these mines and wells, scientists can extract rock samples, learning in this way about their changes and origin, structure and composition. The disadvantage of these methods is that they are only able to study land and only the upper part of the Earth's crust.

Recreating conditions in the Earth's core

But geophysics and seismology - the sciences of earthquakes and the geological composition of the planet - help scientists penetrate deeper and deeper without contact. By studying seismic waves and their propagation, it is determined what both the mantle and the core consist of (it is determined similarly, for example, with the composition of fallen meteorites). Such knowledge is based on received data - indirect - about physical properties substances. Also today, modern data obtained from artificial satellites in orbit contribute to the study.

Planet structure

Scientists were able to understand, by summarizing the data obtained, that the structure of the Earth is complex. It consists of at least three unequal parts. In the center there is a small core, which is surrounded by a huge mantle. The mantle occupies approximately five-sixths of the total volume Globe. And on top everything is covered by a rather thin outer crust of the Earth.

Core structure

The core is the central, middle part. It is divided into several layers: internal and external. According to most modern scientists, the inner core is solid, and the outer core is liquid (in a molten state). And the core is very heavy: it weighs more than a third of the mass of the entire planet with a volume of just over 15. The core temperature is quite high, ranging from 2000 to 6000 degrees Celsius. According to scientific assumptions, the center of the Earth consists mainly of iron and nickel. The radius of this heavy segment is 3470 kilometers. And its surface area is about 150 million square kilometers, which is approximately equal to the area of ​​​​all the continents on the surface of the Earth.

How the Earth's core was formed

There is very little information about the core of our planet, and it can only be obtained indirectly (there are no core rock samples). Therefore, theories can only be expressed hypothetically about how the Earth’s core was formed. The history of the Earth goes back billions of years. Most scientists adhere to the theory that at first the planet formed as a fairly homogeneous one. The process of isolating the nucleus began later. And its composition is nickel and iron. How was the Earth's core formed? The melt of these metals gradually sank to the center of the planet, forming the core. This was due to the higher specific gravity of the melt.

Alternative theories

There are also opponents of this theory, who present their own, quite reasonable, arguments. Firstly, these scientists question the fact of the passage of an alloy of iron and nickel into the center of the core (which is more than 100 kilometers). Secondly, if we assume the release of nickel and iron from silicates similar to meteorites, then a corresponding reduction reaction should have occurred. This, in turn, should have been accompanied by the release of a huge amount of oxygen, forming an atmospheric pressure of several hundred thousand atmospheres. But there is no evidence of the existence of such an atmosphere in the past of the Earth. That is why theories were put forward about the initial formation of the core during the formation of the entire planet.

In 2015, Oxford scientists even proposed a theory according to which the core of planet Earth consists of uranium and has radioactivity. This indirectly proves the long existence of the Earth’s magnetic field, and the fact that in modern times our planet emits much more heat than expected by previous scientific hypotheses.

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 additional source 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.

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 this way. 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.

When you drop your keys into a stream of molten lava, say goodbye to them because, well, dude, they're everything.
- Jack Handy

We all know why this is so: because the Earth's oceans float above the rocks and dirt that make up the land. The concept of buoyancy, in which less dense objects float above denser ones that sink below, explains much more than just the oceans.

The same principle that explains why ice floats in water, a helium balloon rises in the atmosphere, and rocks sink in a lake explains why the layers of planet Earth are arranged the way they are.

The least dense part of the Earth, the atmosphere, floats above oceans of water, which float above the Earth's crust, which sits above the denser mantle, which does not sink into the densest part of the Earth: the core.

Ideally, the most stable state of the Earth would be one that would be ideally distributed into layers, like an onion, with the densest elements in the center, and as you move outward, each subsequent layer would be composed of less dense elements. And every earthquake, in fact, moves the planet towards this state.

And this explains the structure of not only the Earth, but also all the planets, if you remember where these elements came from.

When the Universe was young—just a few minutes old—only hydrogen and helium existed. Increasingly heavier elements were created in stars, and only when these stars died did the heavier elements escape into the Universe, allowing new generations of stars to form.

But this time, a mixture of all these elements - not only hydrogen and helium, but also carbon, nitrogen, oxygen, silicon, magnesium, sulfur, iron and others - forms not only a star, but also a protoplanetary disk around this star.

Pressure from the inside out in a forming star pushes lighter elements out, and gravity causes irregularities in the disk to collapse and form planets.

When solar system four inner world are the densest of all the planets in the system. Mercury consists of the densest elements, which could not hold large amounts of hydrogen and helium.

Other planets, more massive and farther from the Sun (and therefore receiving less of its radiation), were able to retain more of these ultra-light elements - this is how gas giants formed.

On all worlds, as on Earth, on average, the densest elements are concentrated in the core, and the light ones form increasingly less dense layers around it.

It is not surprising that iron, the most stable element and the heaviest element created in large quantities at the edge of supernovae, is the most abundant element in the earth's core. But perhaps surprisingly, between the solid core and the solid mantle lies a liquid layer more than 2,000 km thick: the Earth's outer core.

The Earth has a thick liquid layer containing 30% of the planet's mass! And we learned about its existence using a rather ingenious method - thanks to seismic waves originating from earthquakes!

In earthquakes, seismic waves of two types are born: the main compression wave, known as P-wave, which travels along a longitudinal path

And a second shear wave, known as an S-wave, similar to waves on the surface of the sea.

Seismic stations around the world are capable of picking up P- and S-waves, but S-waves do not travel through liquid, and P-waves not only travel through liquid, but are refracted!

As a result, we can understand that the Earth has a liquid outer core, outside of which there is a solid mantle, and inside there is a solid inner core! This is why the Earth's core contains the heaviest and densest elements, and this is how we know that the outer core is a liquid layer.

But why is the outer core liquid? Like all elements, the state of iron, whether solid, liquid, gas, or other, depends on the pressure and temperature of the iron.

Iron is a more complex element than many you are used to. Of course, it may have different crystalline solid phases, as indicated in the graph, but we are not interested in ordinary pressures. We are descending into the earth's core, where pressures are a million times greater than sea level. What does the phase diagram look like for such high pressures?

The beauty of science is that even if you don't have the answer to a question right away, chances are someone has already done the research that might lead to the answer! In this case, Ahrens, Collins and Chen in 2001 found the answer to our question.

And although the diagram shows gigantic pressures of up to 120 GPa, it is important to remember that the atmospheric pressure is only 0.0001 GPa, while in the inner core pressures reach 330-360 GPa. The upper solid line shows the boundary between melting iron (top) and solid iron (bottom). Did you notice how the solid line at the very end makes a sharp upward turn?

In order for iron to melt at a pressure of 330 GPa, an enormous temperature is required, comparable to that prevailing on the surface of the Sun. The same temperatures at lower pressures will easily maintain iron in a liquid state, and at higher pressures - in a solid state. What does this mean in terms of the Earth's core?

This means that as the Earth cools, its internal temperature drops, but the pressure remains unchanged. That is, during the formation of the Earth, most likely, the entire core was liquid, and as it cools, the inner core grows! And in the process, since solid iron has a higher density than liquid iron, the Earth slowly contracts, which leads to earthquakes!

So, the Earth's core is liquid because it is hot enough to melt iron, but only in regions with low enough pressure. As the Earth ages and cools, more and more of the core becomes solid, and so the Earth shrinks a little!

If we want to look far into the future, we can expect the same properties to appear as those observed in Mercury.

Mercury, due to its small size, has already cooled and contracted significantly, and has fractures hundreds of kilometers long that have appeared due to the need for compression due to cooling.

So why does the Earth have a liquid core? Because it hasn't cooled down yet. And each earthquake is a small approach of the Earth to its final, cooled and completely solid state. But don't worry, long before that moment the Sun will explode and everyone you know will be dead for a very long time.

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.

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