Why doesn't the earth's core cool down? What's at the center of the Earth. Who heats up the earth's core? The hot core of the earth

With a thickness of about 2200 km, between which a transition zone is sometimes distinguished. Core mass - 1.932 10 24 kg.

Very little is known about the core - all information is obtained by indirect geophysical or geochemical methods, and images of the core material are not available, and are unlikely to be obtained in the foreseeable future. However, science fiction writers have already described in detail several times travel to the core of the Earth and the untold riches hidden there. The hope for treasures in the core has some basis, since according to modern geochemical models, the content of noble metals and other valuable elements in the core is relatively high.

History of the study

Probably one of the first to suggest the existence of a region of increased density inside the Earth was Henry Cavendish, who calculated the mass and average density of the Earth and found that it was significantly greater than the density characteristic of rocks exposed to the Earth's surface.

The existence was proven in 1897 by the German seismologist E. Wichert, and the depth of occurrence (2900 km) was determined in 1910 by the American geophysicist B. Gutenberg.

Similar calculations can be made for metal meteorites, which are fragments of the nuclei of small planetary bodies. It turned out that the formation of the nucleus in them occurred much faster, over a period of about several million years.

Theory of Sorokhtin and Ushakov

The described model is not the only one. So, according to the model of Sorokhtin and Ushakov, set out in the book “Development of the Earth,” the process of formation of the earth’s core lasted approximately 1.6 billion years (from 4 to 2.6 billion years ago). According to the authors, the formation of the nucleus occurred in two stages. At first the planet was cold, and no movements occurred in its depths. It was then heated by radioactive decay enough for the metallic iron to begin to melt. It began to flock to the center of the earth, while due to gravitational differentiation a large amount of heat was released, and the process of separating the core only accelerated. This process only went to a certain depth, below which the substance was so viscous that the iron could no longer sink. As a result, a dense (heavy) annular layer of molten iron and its oxide was formed. It was located above the lighter substance of the primordial “core” of the Earth.

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.

Our planet Earth has a layered structure and consists of three main parts: the earth's crust, mantle and core. What is the center of the Earth? Core. The depth of the core is 2900 km, and the diameter is approximately 3.5 thousand km. Inside there is a monstrous pressure of 3 million atmospheres and an incredibly high temperature - 5000°C. It took scientists several centuries to find out what was in the center of the Earth. Even modern technology could not penetrate deeper than twelve thousand kilometers. The deepest borehole, located on the Kola Peninsula, has a depth of 12,262 meters. It's a long way from the center of the Earth.

History of the discovery of the earth's core

One of the first to guess about the presence of a core in the center of the planet was the English physicist and chemist Henry Cavendish at the end of the 18th century. Using physical experiments, he calculated the mass of the Earth and, based on its size, determined the average density of the substance of our planet - 5.5 g/cm3. The density of known rocks and minerals in the earth's crust turned out to be approximately half as much. This led to the logical assumption that in the center of the Earth there is a region of denser matter - the core.

In 1897, the German seismologist E. Wichert, studying the passage of seismological waves through the interior of the Earth, was able to confirm the assumption of the presence of a core. And in 1910, the American geophysicist B. Gutenberg determined the depth of its location. Subsequently, hypotheses about the process of nucleus formation were born. It is assumed that it was formed due to the settling of heavier elements towards the center, and initially the substance of the planet was homogeneous (gaseous).

What does the core consist of?

It is quite difficult to study a substance of which a sample cannot be obtained in order to study its physical and chemical parameters. Scientists only have to assume the presence of certain properties, as well as the structure and composition of the nucleus based on indirect evidence. The study of the propagation of seismic waves was especially helpful in studying the internal structure of the Earth. Seismographs located at many points on the planet's surface record the speed and types of passing seismic waves resulting from shaking of the earth's crust. All these data make it possible to judge the internal structure of the Earth, including its core.

At the moment, scientists assume that the central part of the planet is heterogeneous. What is at the center of the Earth? The part adjacent to the mantle is the liquid core, consisting of molten matter. Apparently it contains a mixture of iron and nickel. Scientists were led to this idea by a study of iron meteorites, which are pieces of asteroid cores. On the other hand, the resulting iron-nickel alloys have a higher density than the expected core density. Therefore, many scientists are inclined to assume that in the center of the Earth, the core, there are lighter chemical elements.

Geophysicists explain the existence of a magnetic field by the presence of a liquid core and the rotation of the planet around its own axis. It is known that an electromagnetic field around a conductor arises when current flows. The molten layer adjacent to the mantle serves as such a giant current-carrying conductor.

The inner part of the core, despite the temperature of several thousand degrees, is a solid substance. This is because the pressure at the center of the planet is so high that hot metals become solid. Some scientists suggest that the solid core consists of hydrogen, which, under the influence of incredible pressure and enormous temperature, becomes like metal. Thus, even geophysicists still do not know for certain what the center of the Earth is. But if we consider the issue from a mathematical point of view, we can say that the center of the Earth is approximately 6378 km away. from the surface of the planet.

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 we 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 of 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 the 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 has been characteristic of the core since the formation of the planet, whatever its chemical composition and structure may 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. 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.

I will try to explain using the example of a basin.

The first mistake is that the facts are not collected.

They are very heterogeneous and themselves cluster into systems at different distances from the historically established center of knowledge. It's the most important. Science does not collect facts in a bowl, it adjusts the basin to the facts. You think differently and do the opposite, this is a delusion, because you throw out those facts that will inevitably contradict your basin, that is, you simply do not see these facts, you ignore them.

Further, everything depends on the stage of cognition, many basins are found, those that cover the majority of facts are accepted as relatively true and are subsequently used as relative knowledge, which in practice becomes absolute knowledge, and facts that do not fall into focus on practice declared as an error, for example 49%, 30%, etc. to 0% (this is a reflection of the progress of the basins, which is impossible with the thinking that you have). And you see only this, because you are taught this way at school, that this knowledge is constant, it is simply a feature of the teaching method, you are, roughly speaking, constantly deceived, saying that this knowledge is absolute, and science generally says that this knowledge is relative, this is normal, because this is how our brain works, it could not learn otherwise, it is not science that is imperfect, but our brain is imperfect. And only in a narrow specialization the brain begins to think in abstract scientific concepts, these are the specialists, this is exactly what I talked about above.

But this is practice, and the scientific theory that we are talking about is gradually finding more and more new basins, finds the last one, which contains ALL the facts from a given group at a certain distance, before this the basins were called hypotheses, and this megacoxa is called a theory (this is an old classification, today everything is hypotheses), and most importantly, it predicts ALL new facts that appear in a certain group, at a certain distance.

Today we are in the megabasin stage in most areas of knowledge, and what you are citing are old basins that are no longer needed because they are ineffective, that is, it is not the facts that are discarded, but the basins.

Now further, as soon as we comprehended one group of facts, we began to see another group of facts, which cluster at a greater distance than the center of knowledge and which we simply could not measure and see before and built hypotheses about them based on the facts underlying on the borders, that is, there was a mass of basins without practice, which were more or less covered by a set of indirect facts that followed from the facts bordering on observation. Until a basin appeared that would explain them all, all the indirect facts that we cannot see, but we can see their relationship both with the facts known to us before, and with each other. This basin may completely contradict the previous megabasin, since due to the distance, the laws by which groups of facts are clustered are always different, sometimes opposite.

These are, for example, the theories of Newton (megacoxa) and Einstein (new indirect megacoxa), they are opposite and at the same time objective. Gradually, due to progress in the often parallel direction of knowledge, we are already beginning to see direct facts, and not indirect facts, that is, the limit of what is observed is growing and if you are aware, then EVERYTHING in General Relativity is experimentally confirmed today, as soon as a tool appears that can do this confirm, that is, an observed and not an indirect fact.

This cycle is endless, this is the key to the effectiveness of the scientific method of cognition, if we do not see a fact and cannot find it indirectly, then we do not even look in its direction and do not worry, since in practice it is impossible to use it. This is different from faith, when such a fact is invented. That is, to the question whether there is a God, science says I don’t know in theory, but in practice it says no, but this is relative knowledge, as soon as a fact arises in a certain field of knowledge, we will completely reconsider everything.

Another important aspect is predictive, if a new fact appears in a group of facts that were already included in a well-studied group of facts at a certain distance, which has already covered the megacoxa, then the theory is declared invalid and science changes completely, the old megacoxa is thrown out, but not there is an old discarded ordinary basin, which defeated the megabasin, since it does not correspond to many older facts, and a new basin is being made, which may be SIMILAR to the old basins and non-specialists begin to shout that science itself does not know what it wants and all scientific knowledge is bullshit and scientists They always lie. This is also a mistake due to the fact that we think in analogies, we think in similarities, this is how neural circuits are structured.

But we don’t know that these new facts within a known group of facts are part of a new group of facts and, so to speak, the tip of the iceberg or part of the old group.

The first case is general relativity, the second case is, for example, the theory of evolution.

That is why in theory we always say that we don’t know anything, we don’t know whether Newton or Darwin are right, but in practice we say that yes, they are right and objective and this is exactly what is taught at school, which confuses the student even more. Because they found a bunch of facts that refute both Newton and Darwin, but they turned out to be from a different group of facts, mainly on the border between them. This is called clarification of the theory, for example, Darwin’s is a synthetic theory of evolution, the theory of punctuated equilibrium and the modern theory of evolution, in which there is inheritance of acquired characteristics, etc., what all the previous ones denied and denied rightly, the scale was simply different.

Excessive secrecy

Why does the Earth's core remain hot?

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

It's getting cold!

Towards the Severnaya Zemlya archipelago at a speed of 55 kilometers per year. Scientists suggest that a pole change is being prepared due to disturbances in the liquid part of the planet’s core, which is inaccessible to direct observations. It is difficult to understand what exactly is happening there, but there are many hypotheses.

Mission to the "iron world"

In 2022, NASA is going to send a device to the asteroid Psyche, located between Mars and Jupiter. It is called the iron world.

By the reflection of rays from the surface, by how quickly it heats up and cools down, scientists realized that it is, if not completely, then mostly metal. It is possible that iron meteorites fly to us from there. This happens very rarely; no more than two hundred such events are known.

It is assumed that Psyche is the core of a terrestrial planet that has lost its outer shells. Together with Earth and Venus, this planet was formed near the Sun, but then something happened. Maybe it’s a catastrophe, or maybe it’s all due to repeated heating of the planet earth - the clumps of matter from which planets are formed.

Scientists certainly want to get into the “iron world,” and not only for the sake of geological exploration of deposits in the interests of our descendants. First of all, to closely study the analogue of the Earth's core.

Why is the core iron?

The Earth's core is a most interesting object. Its composition and temperature are reflected in the overlying layers and atmosphere. The core is the source of the magnetic field that gave rise to life. There is also the key to the secret of the formation of the terrestrial planets.

The Earth's interior is explored using seismic waves and modeling. Roughly speaking, the planet consists of an upper shell - crust, mantle and core.

Several facts indicate that the core is iron. The Earth has its own magnetic field, as if a dipole is inserted along the axis of rotation. The mantle cannot generate such a field; it conducts electricity too weakly. According to the geodynamo model, only a conducting fluid is capable of this. This means that part of the core is liquid. Iron is one of the most common elements in the solar system. This is confirmed by its abundance in meteorites.

Elastic S-waves do not pass through the outer part of the core, which means it is liquid. The inner part of the core, with a radius of approximately 1221 kilometers, weakly propagates S-waves - accordingly, it is either solid or in a state simulating solidity. The boundary between the two layers in the core is quite clear, as is the boundary between the core and the lower mantle.

The core is believed to be iron, with small admixtures of nickel (this is indicated by the composition of iron meteorites), silicon, sulfides and oxygen.

Some features of the passage of seismic waves suggest that the solid inner core rotates slightly faster than the mantle and crust, by about 0.15 degrees per year.

When and how was the Earth's core formed? What is the ratio of chemical elements in it? Why is it not uniform? What's the temperature there? Where is the source of energy? And most importantly, why did the core form inside the planet in the first place? There are many hypotheses for each of these and many other questions.

Which twin is the lucky one?

Venus is considered the Earth's twin - it is only slightly smaller in mass and size. But the current conditions on its surface are completely different. The Earth has its own magnetic field, atmosphere and biosphere.

Venus on this list only has a toxic atmosphere with clouds of sulfuric acid. There are no traces of the magnetic field in the geological past, although they could have disappeared. It probably all has to do with the origin of the twins.

Venus and Earth formed in one part of the gas and dust nebula surrounding the Sun. The embryos of the planets grew larger, attracting more and more material to themselves. When the mass became critical, heating and melting began. The substance was divided into fractions: heavy elements settled inside, light ones rose to the top.

Scientists from Germany, Japan and France believe that the layering of bodies such as the Earth proceeds evenly and stably, each layer is homogeneous. For the core to be two-layered and heterogeneous, somewhere near the end of the process the planet must have experienced a very strong impact from another massive body. Part of the “alien” substance remained in the bowels of the Earth, part was knocked into orbit, where the Moon was then formed. The impact caused the planet's interior to mix up, leading to partial melting of the core.

But the evolution of Venus went smoothly, without an emergency on a cosmic scale. The delamination was successfully completed with the formation of a solid iron core, unable to generate a magnetic field.

There is another hypothesis: spontaneous crystallization of the iron melt. However, to do this, it needs to cool down to a thousand Kelvin, which is impossible.

This means that the crystallization nuclei penetrated from outside, scientists from the USA concluded. For example, from the lower mantle. These are large pieces of iron measuring tens and hundreds of meters. Where they will come from is a big question.

One answer lies on the Earth's surface in the form of ancient ferruginous quartzites. Perhaps more than three billion years ago, these rocks formed the bottom of the oceans. Due to the movement of plates, it sank into the mantle and from there into the core.

Creating a magnetic shield

The ratio of radioactive lead isotopes indicates the age of the core: about four and a half billion years. It is unknown when the magnetic field appeared. Its traces are already found in the oldest rocks on Earth, 3.5 billion years old.

According to the geodynamo model, the Earth's magnetic field requires a conducting fluid, the rotation of which is accompanied by mixing.

The problem is that the magnetic field of rapidly rotating liquids sooner or later fades. Judging by geological data, over the period of time visible to us, the intensity of the Earth’s magnetic field did not change. There must be some kind of constant powerful source of energy.

There are two candidates for this role. Temperature convection, possible if the inner core is hotter than the outer one, and compositional convection, that is, the movement of elements from one part to another. This means that the hard part of the core increases. But you shouldn’t be afraid of complete freezing. This will take more than one billion years.