The outer and inner core of the earth consists of. Who warms up the earth's core

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 - a monstrous pressure of 3 million atmospheres and an incredibly high temperature - 5000 ° C. In order to find out what is in the center of the Earth, it took scientists several centuries. 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. Far from the center of the earth.

The history of the discovery of the earth's core

One of the first to guess about the presence of a nucleus in the center of the planet was the English physicist and chemist Henry Cavendish at the end of the 18th century. With the help of 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 two times less. From this followed a logical assumption that in the center of the Earth there is an area of ​​denser matter - the core.

In 1897, the German seismologist E. Wiechert, studying the passage of seismological waves through the inner parts 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 formation of the nucleus were also born. It is assumed that it was formed as a result of the settling of heavier elements to the center, and initially the substance of the planet was homogeneous (gaseous).

What is the core made of?

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

To date, scientists suggest that the central part of the planet is heterogeneous. What is at the center of the earth? The part adjacent to the mantle is a liquid core, consisting of molten matter. Apparently, it contains a mixture of iron and nickel. This idea led scientists to the study of iron meteorites, which are pieces of asteroid nuclei. On the other hand, the obtained iron-nickel alloys have more high density than the estimated core density. Therefore, many scientists tend to assume that in the center of the Earth, the core, there are also lighter chemical elements.

The presence of a liquid core and the rotation of the planet around its own axis of geophysics explain the existence magnetic field. 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 nucleus, despite the temperature of several thousand degrees, is solid. This is due to the fact that the pressure in 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 a metal. Thus, what is the center of the Earth, even geophysicists are still not known for certain. But if we consider the issue from a mathematical point of view, we can say that the center of the Earth is located approximately 6378 km. from the surface of the planet.

After dropping the keys into the molten lava flow, say goodbye to them, because, well, dude, they are everything.
- Jack Handy

We all know why this is so: because the Earth's oceans rise above the rocks and mud that make up the land. The concept of buoyancy, in which less dense objects float above denser objects that sink below, explains much more than just 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 water oceans that float above the earth's crust, which sits above the denser mantle that doesn't sink into the densest part of the Earth: the core.

Ideally, the most stable state of the Earth would be one that would ideally be layered, like an onion, with the densest elements in the center, and as you move outward, each successive layer would consist of less dense elements. And every earthquake actually moves the planet towards that state.

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

When the universe was young - only a few minutes old - only hydrogen and helium existed. More and more heavy elements were created in the stars, and only when these stars died did the heavy elements go out into the Universe, allowing new generations of stars to form.

But this time, the 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 peace are the densest of all planets in the system. Mercury is made up of the densest elements that could not hold a large number of hydrogen and helium.

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

In all worlds, as on Earth, on average, the densest elements are concentrated in the core, while the lungs form progressively less dense layers around it.

Not surprisingly, iron, the most stable element, and the heaviest element created in large quantities on the border of supernovae, and there is the most common element of the earth's core. But perhaps surprisingly, between the solid core and the solid mantle is a liquid layer more than 2,000 km thick: Earth's outer core.

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

Seismic waves of two types are born in earthquakes: the main compressional, known as P-wave, passing along the longitudinal path

And the second shear wave, known as the S-wave, similar to the 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, they are refracted!

As a result, it can be understood that the Earth has a liquid outer core, outside of which there is a solid mantle, and inside - 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, gaseous, or otherwise, depends on the pressure and temperature of the iron.

Iron is a more complex element than many you are familiar with. Of course, it can have different crystalline solids, as shown in the graph, but we are not interested in ordinary pressures. We are descending to the core of the earth, where pressures are a million times higher than at sea level. And what does the phase diagram look like for such high pressures?

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

And although the diagram shows gigantic pressures up to 120 GPa, it is important to remember that the pressure of the atmosphere is only 0.0001 GPa, while in the inner core the pressures reach 330-360 GPa. The top 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 sharp turn up?

In order for iron to melt at a pressure of 330 GPa, an enormous temperature is required, comparable to that which prevails 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, while 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 is slowly shrinking, which leads to earthquakes!

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

If we want to look far into the future, we can expect the same properties that are observed in Mercury.

Mercury, due to its small size, has already cooled and contracted significantly, and has cracks hundreds of kilometers long due to the need for contraction due to cooling.

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

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, under it there is a massive dense core, the diameter of which, according to estimates, reaches 1300 km. The transition zone has a non-uniform thickness and gradually hardens, passing into the inner core. On the surface of the upper layer, the temperature is in the region of 5960 degrees Celsius, although these data are considered approximate.

Approximate composition of the outer core and methods for its determination

Very little is 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 of which the outer core of our planet can consist 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 terms of chemical composition, since the original space bodies were much smaller than Earth to size. 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 it more low density than iron-nickel alloys.

What happens in the outer part of the planet's core?

The outer surface of the core at the boundary with the mantle is inhomogeneous. Scientists suggest that it has a different thickness, forming a kind of internal relief. This is due to the constant mixing of heterogeneous deep substances. They are different 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.

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

How is the outer layer of the nucleus studied?

Scientists can judge what the core looks like and what it consists of by monitoring seismic activity. So, 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 hides dozens more unsolved mysteries and awaits new fundamental discoveries.

With a thickness of about 2200 km, between which a transition zone is sometimes distinguished. The mass of the core is 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 matter are not available, and are unlikely to be obtained in the foreseeable future. However, science fiction writers have already described in detail several times the journey to the core of the Earth and the untold riches hidden there. The hope for the treasures of the core has some grounds, since, according to modern geochemical models, the content of noble metals and other valuable items.

History of study

Probably one of the first assumptions about the existence of an area of ​​increased density inside the Earth was made by Henry Cavendish, who calculated the mass and average density of the Earth and found that it is much higher than the density characteristic of rocks emerging on the earth's surface.

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

Similar calculations can be made for metallic meteorites, which are fragments of the nuclei of small planetary bodies. It turned out that the formation of the core in them occurred much faster, over a time of the order of 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 forth in the book "The Development of the Earth", the process of the formation of the earth's core stretched for approximately 1.6 billion years (from 4 to 2.6 billion years ago). According to the authors, the formation of the core occurred in two stages. At first, the planet was cold, and there was no movement in its depths. Then she warmed up radioactive decay enough to start melting metallic iron. It began to flow to the center of the earth, while due to gravitational differentiation, a large amount of heat was released, and the process of separation of the core only accelerated. This process went only 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 primeval "core" of the Earth.

In what time immemorial did this happen? All these questions have long troubled mankind. And many scientists wanted to quickly find out what is there, in the depths? But it turned out that to study 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 bowels 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 rocks, naked in a natural way. Cliffs and slopes of mountains, steep banks of rivers and seas... Here you can see with your own eyes what existed probably millions of years ago. Wells are being drilled in some suitable places. One of these - at its depth - fifteen thousand meters. The mines that people break through for also help to study the inner Core, of course, they cannot “get it”. But on the other hand, from these mines and wells, scientists can extract rock samples, learning in this way about their change and origin, structure and composition. The disadvantage of these methods is that they are able to explore only land and only upper part the crust of the earth.

Recreating Conditions at the Earth's Core

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

The structure of the planet

Scientists managed to understand, summarizing the data obtained, that the structure of the Earth is complex. It consists of at least three unequal parts. In the center is a small core, which is surrounded by a huge mantle. The mantle occupies about five-sixths of the total globe. And from above everything is covered by a rather thin outer crust of the Earth.

The structure of the nucleus

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 one is liquid (it is 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. In the core, the temperature is quite high, it ranges from 2000 to 6000 degrees Celsius. According to the assumptions of science, 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 was the Earth's core 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 be expressed only hypothetically about how the core of the Earth was formed. The history of the Earth is billions of years old. Most scientists adhere to the theory that in the beginning 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 descended to the center of the planet, forming the core. This was due to more specific gravity melt.

Alternative theories

There are also opponents of this theory, who bring their own, quite reasonable arguments. First, these scientists question the passage of an alloy of iron and nickel to the center of the nucleus (and this is more than 100 kilometers). Secondly, if we assume the release of nickel and iron from silicates similar to meteoric ones, then the corresponding reduction reaction should have occurred. She, in turn, had to be accompanied by the release huge amount oxygen, forming an atmospheric pressure of several hundred thousand atmospheres. And there is no evidence of the existence of such an atmosphere in the past of the Earth. Therefore, 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 the planet Earth consists of uranium and has radioactivity. This indirectly proves both such a long existence of the magnetic field near the Earth, and the fact that at the present time our planet radiates much more heat than was assumed by previous scientific hypotheses.