The history of the development of the planet Earth. Origin of land

Form, dimensions and structure of the globe

The earth has a complex configuration. Its form does not correspond to any of the correct geometric figures. Speaking about the shape of the globe, it is believed that the figure of the Earth is limited to an imaginary surface that coincides with the surface of the water in the world ocean, conditionally continued under the mainland so that the sheer line can be perpendicular to this surface at any point of the globe. Such a form is called geoid, i.e. Form inherent in the earth.

Studying the form of the Earth has a rather long history. The first assumptions about the ferro-shaped form of the Earth belong to the ancient Greek scientist Pythagora (571-497 BC). However, the scientific evidence of the flag-formation of the planet was given by Aristotle (384-322 BC), the first to explaining the nature of the lunar eclipses as the shadow of the Earth.

In the 18th century I. Antyuton (1643-1727) calculated that the rotation of the Earth determines the deviation of its shape from the exact ball and gives it some sustowerness of the poles. The reason for this is centrifugal force.

Determination of the size of the earth is also long offered by the minds of humanity. For the first time, the size of the planet calculated the Alexandrian scientist Eratosthen Kirensky (about 276-194 BC): According to him, the land radius is about 6290 km. In 1024-1039. AD Abu Reichan Biruni calculated the land radius, which was equal to 6340 km.

For the first time, accurate calculation of the shape and dimensions of the geoid was produced in 1940 A.A.Yezotov. The figure calculated by him is named after the famous Russian geodesist F.N. Krasovsky Ellipsoid Krasovsky. These calculations showed that the figure of the Earth is a three-axle ellipsoid and differs from the ellipsoid of rotation.

According to measurements, the Earth is flattened with a ball with poles. Equatorial radius (large ellipsylide semi-axle - a) is 6378 km 245 m, the polar radius (small semi-axis - b) is 6356 km 863 m. The difference between equatorial and polar radius is 21 km 382 m. Ground compression (difference ratio between a and b K a) is (a - b) / a \u003d 1/2 298.3. In cases where it does not require greater accuracy, the average radius of the Earth takes equal to 6371 km.

Modern measurements show that the geoid surface is somewhat exceeds 510 million km, and the volume of land is approximately 1.083 billion km. The definition of other characteristics of the Earth - mass and density - is made on the basis of fundamental laws of physics. So the mass of the Earth is 5.98 * 10 T. Zeznaya density turned out to be 5.517 g / cm.

General structure of land

To date, by seismological data, about ten borders of the section, indicating the concentric nature of its internal structure, are distinguished. The main of these borders are: Mochorovich's surface at depths of 30-70 km on continents and at depths of 5-10 km under the bottom of the ocean; The surface of Vikherta - Gutenberg at a depth of 2900 km. These major borders share our planet for three concentric shells - geospheres:

Ground Craer - the outer shell of the Earth, located above the surface of Mochorovichich;

Earth's mantle - an intermediate shell, limited by the verification of Mochorovichich and Vihert - Gutenberg;

The core of the Earth is the central body of our planet, located deeper the surface of Vikhurt - Gutenberg.

In addition to the main borders, a number of secondary surfaces inside the geosphere are distinguished.

Earth's crust. This geosphere is a small proportion of the total mass of the Earth. Power and compositions are distinguished by three types of earthbow:

The continental bark is characterized by a maximum power reaching 70 km. It is sterin from magmatic, metamorphic and sedimentary rocks that form three layers. The power of the upper layer (sediment) usually does not exceed 10-15 km. Below is a granite-gneisse layer with a capacity of 10-20 km. At the bottom of the cortex, a balste layer with a capacity of up to 40 km.

The ocean bark is characterized by a small capacity - decreased to 10-15 km. It also consists of 3 layers. Upper, sedimentary, does not exceed a few hundred meters. The second, balste, with a total capacity of 1.5-2 km. The lower layer of the oceanic cortex reaches the power of 3-5 km. As part of this type of earth's crust, there is no granite-gneisse layer.

The bark of transitional areas is usually characteristic of the periphery of large continents, where the outskirts are developed, there are islands archipelagoes. Here there is a replacement of the continental cortex on oceanic and, of course, in the structure, power and density of the breeds of the cortex of transition areas occupies an intermediate place between the above two types of Cor.

Mantle earth. This geosphere is the largest element of the Earth - it takes 83% of its volume and is about 66% of its mass. As part of the mantle, a number of section boundaries are distinguished, the main of which are surfaces that occur at depths of 410, 950 and 2700 km. By the values \u200b\u200bof physical parameters, this geosphere is divided into two subobs:

Upper mantle (from the surface of Mochorovichich to a depth of 950 km).

Lower mantle (from the depth of 950 km to the surface of Vihert - Gutenberg).

The upper mantle in turn is divided into layers. The upper, sparing from the surface of Mochorovichich to a depth of 410 km, is called the layer of Gutenberg. Inside this layer is isolated a hard layer and asthenosphere. The earth's crust, together with the solid part of the Gutenberg layer, forms a single hard layer lying on an asthenosphere, which is called a lithosphere.

Below the layer of Gutenberg lies a layer of Golitsin. Which is sometimes called medium mantia.

Lower mantle has a significant capacity, almost 2 thousand km, and consists of two layers.

Earth core. The central geosfra of the Earth takes about 17% of its volume and is 34% of the mass. In the context of the kernel, two boundaries are distinguished - at depths of 4980 and 5120 km. In this connection, it is divided into three elements:

The external kernel - from the surface of Vikhert - Gutenberg to 4980 km. This is a substance that is high pressure and temperatures is not a liquid in the usual understanding. But it has some properties.

Transitional shell - in the intervadium 4980-5120 km.

Subordro - below 5120 km. Perhaps is in a solid state.

The chemical composition of the Earth is similar to the composition of other planets of the earth group<#"justify">· lithosphere (bark and the top of the mantle)

· hydrosphere (liquid shell)

· atmosphere (gas shell)

It covered about 71% of the surface of the earth, its average depth is about 4 km.

The atmosphere of the Earth:

more than 3/4 - nitrogen (N2);

approximately 1/5 - oxygen (O2).

Clouds consisting of the smallest water droplets close approximately 50% of the surface of the planet.

The atmosphere of our planet, like its subsoil, can be divided into several layers.

· The lowest and dense layer is called a troposphere. There are clouds here.

· Meteors are lit in the mesosphere.

· Polar radiances and many orbits of artificial satellites are the inhabitants of the thermosphere. Ghostly silver clouds are so far.

The hypothesis of the origin of the Earth. First cosmogonistic hypothesis

A scientific approach to the issue of the origin of the Earth and the Solar System was possible after the strengthening of the thought of material unity in the Universe in science. There is a science on the origin and development of celestial bodies - cosmogony.

The first attempts to give a scientific justification to the issue of the origin and development of the solar system were made 200 years ago.

All hypothesis about the origin of the Earth can be divided into two main groups: nebular (lat. "Nebula" - fog, gas) and catastrophic. The first group is based on the principle of formation of planets from gas, from dust nebula. The second group is based on various catastrophic phenomena (the collision of the celestial bodies, close to passing apart from each other, etc.).

One of the first hypotheses was expressed in 1745 by the French scientist J. Buthoff. According to this hypothesis, our planet was formed as a result of the cooling of one of the clots of a solar material thrown by the Sun with a catastrophic collision of it with a large comet. J. Buffon's thought on the formation of the Earth (and other planets) from the plasma was used in a whole series of later and more advanced hypotheses of the "hot" origin of our planet.

Nebular theories. Hypothesis of Kant and Laplace

Among them, of course, the leading place occupies a hypothesis developed by the German philosopher I.Kanta (1755). Regardless of him, another scientist - French Mathematics and Astronomer P. Laplas - came to the same conclusions, but developed a hypothesis more deeply (1797). Both hypothesis are similar among themselves essentially and are often considered as one, and the authors consider it the founders of scientific cosmogony.

Kant's hypothesis - Laplace refers to a group of nebular hypotheses. According to their concept, there were previously huge gas-dust nebula (dust nebula from solid particles, according to I. Kant; gas - on the assumption of P.Laplas). The nebula was hot and rotated. Under the influence of laws of matter, it gradually was gradually compacted, flattened, forming in the center of the core. So the primary sun was formed. Further cooling and sealing of the nebula of the prickly increase in the angular velocity of rotation, as a result of which the external part of the nebula was separated from the main mass in the form of a rings rotating in the equatorial plane: several were formed. As an example, Laplace brought the rings of Saturn.

It is unevenly cooling, the rings were broken, and due to attraction between the particles, the planets appeared around the slot. The cooled planets were covered with solid crust, geological processes began to develop on the surface.

I.Kant and P.Laplas correctly noted the basic and characteristic features of the solar system structure:

) The overwhelming part of the mass (99.86%) of the system is concentrated in the sun;

) Planets are treated almost in circular orbits and almost in the same plane;

) All planets and almost all of their satellites are rotating in the same side, all the planets rotate around their axis to the same side.

A significant achievement of I.Kanta and P. Laplas was the creation of a hypothesis, which was based on the idea of \u200b\u200bdeveloping matter. Both scientists believed that the nebula had a rotational movement, as a result of which the particle seal and the formation of the planets and the Sun had occurred. They believed that the movement was inseparable from matter and also forever, like the matter itself.

The hypothesis of Kanta Laplas existed in almost two hundred years. Subsequently, its failure was proved. So, it became known that satellites of some planets, such as uranium and Jupiter, rotate in a different direction than the planets themselves. According to modern physics, the gas separated from the central body should not be filled with the gas rings, and later in the planet. Other significant disadvantages of Cant and Laplace hypothesis are the following:

It is known that the moment of the amount of movement in the rotating body always remains constant and is distributed evenly throughout the body proportionally mass, distance and angular velocity of the corresponding part of the body. This law applies to the nebula, from which the sun and planets were formed. In the solar system, the number of motion does not comply with the law of the distribution of the amount of movement in the mass resulting from one body. The planet of the solar system focuses 98% of the moment of the number of system movement, and the sun has only 2%, while the share of the Sun accounts for 99.86% of the entire mass of the solar system.

If you fold the moments of rotation of the Sun and other planets, then when calculating it turns out that the primary sun rotated at the same speed, with what Jupiter rotates. In this regard, the Sun was to have the same compression as Jupiter. And this, as calculations show, is not enough to cause crushing the rotating sun, which, as Kant and Laplace believed, broke up due to an excess of rotation.

Currently, it is proved that a star with an excess of rotation disintegrates into parts, and does not form a family of planets. An example is the spectral-dual and multiple systems.

Catastrophic theories. Hypothesis Jeans

earth cosmogonical concentric origin

After the hypothesis of Canta Laplace in Cosmogony, several more hypotheses of the formation of the solar system were created.

The so-called catostrophic appear, based on the element of chance, the element of a happy coincidence of circumstances:

Unlike Kant and Laplace, which "borrowed" from J. Buthffon only the idea of \u200b\u200bthe "hot" emergence of the Earth, followers of this flow also developed the aliest katastrophism hypothesis. Buffon believed, the land and planets were formed due to the collision of the Sun with a comet; Chamberlain and Multon - the formation of planets is connected with the tidal exposure to the other star passing by the Sun.

As an example of the hypothesis of the Catostrophic direction, consider the concept of the English Astronoma of Jeans (1919). The basis of his hypothesis is the possibility of passing near the sun another star. Under the action of its attraction from the Sun, a gas stream was escaped, which for further evolution turned into the planet of the solar system. A gas jet for its form resembled a cigar. Large planets were formed in the central part of this rotating body around the sun, Jupiter and Saturn, and at the ends of the "cigar" - the planet of the earth group: Mercury, Venus, Earth, Mars, Pluto.

Jeans believed that the passage of the star by the Sun, which caused the formation of the planets of the solar system, makes it possible to explain the inconsistency in the mass distribution and the moment of movement in the solar system. The star, who escaped the gas stream from the Sun, gave a rotating "cigar" an excess point of movement. Thus, one of the main disadvantages of Canta Laplas hypothesis was eliminated.

In 1943, Russian Astronomer N.I. Pariovsky calculated that with a high speed of a star, which passed by the Sun, the gas protubenets was to leave with the star. At low speed, the star gas jet should have fallen into the sun. Only in the case of a strictly defined star speed, the gas protubenets could become a satellite of the sun. In this case, its orbit should be 7 times less orbit close to the sun planet - Mercury.

Thus, the hypothesis of jeans, as well as the hypothesis of Canta Laplace, could not give a correct explanation to the disproportionate distribution of the moment of movement in the solar system

The biggest disadvantage of this hypothesis is the fact of chance, the exclusivity of the formation of the Family Planets, which contradicts the materialistic worldview and the existing facts speaking about the presence of planets in other star worlds.

In addition, the calculations have shown that the rapprochement of stars in the world space is practically excluded, and even if it happened, the passing star could not give the planet movement in circular orbits.

Modern hypothesis

A fundamentally new idea is laid in the hypothesis of the "cold" origin of the Earth. The most deeply developed meteorite hypothesis proposed by the Soviet scientist O. Yu.Smidt in 1944. From other hypothesis of "cold" origin should be called the hypotheses of K.Wuzzker (1944) and J.Kuper (1951), in many respects close to the theory of O. Yu.Smidt, F. Foil (England), A. Cameron (USA ) And E. Shatzman (France).

The most popular are hypotheses about the origin of the solar system created by O.Yu. Schmidt and V.G.Feshenkov. Both scientists in the development of their hypotheses proceeded from the ideas about the unity of matter in the universe, on the continuous movement and evolution of matter, which are its main properties, about the diversity of the world due to various forms of existence of matter.

Hypothesis O.Yu. Schmidt.

According to the concept of O.Yu.Smidt, the solar system was formed from the accumulation of interstellar matter captured by the Sun in the process of movement in the world space. The sun is moving around the center of the Galaxy, making a complete turn for 180 million. Among the stars of the galaxy there are large accumulations of gas-dust nebulaes. As a visit from this, O. Yu.Smidt believed that the sun had entered one of these clouds during the move and captured him with him. The rotation of the clouds in a strong gravitational field of the Sun led to a complex redistribution of meteorite particles by weight, density and sizes, resulting in part of meteorites, the centrifugal force of which turned out to be weaker than the strength of the power, the sun was absorbed. Schmidt believed that the initial cloud of interstellar matter had some rotation, otherwise his particles would fall out in the sun.

The cloud turned into a flat compacted rotating disk, in which concentration occurred due to an increase in mutual attraction of particles. The formed thickening-body grew due to the minor particles joining them, like a snowball. In the process of circulation, the clouds, when the particles are stacked, their sticking began, the formation of larger on the mass of aggregates and accession to them is the accretion of smaller particles entering the sphere of their gravitational influence. In this way, planets and satellites appearing around them around them. The planets began to rotate in circular orbits due to averaging the orbits of small particles.

Earth, according to O. Y. SMIDTA, also formed from the roa of cold solids. The gradual hearing of the subsoil of the Earth was due to the energy of radioactive decay, which led to the release of water and gas, partitioned in small quantities into solid particles. As a result, oceans and the atmosphere arose, which caused the appearance of life on Earth.

O.Yu.Smidt, and later his disciples gave a serious physico-mathematical substantiation of the meteorite model of formation of the planets of the solar system. The modern meteorite hypothesis explains not only the features of the motion of the planets (the form of orbits, different directions of rotation, etc.), but also the actual observed distribution of them by weight and density, as well as the ratio of planetary moments of the amount of movement with sunny. The scientist believed that the existing inconsistencies in the distribution of moments of the amount of the sun and the planets are explained by different initial moments of the amount of the sun and gas-dusty nebula. Schmidt calculated and mathematically substantiated the distance of the planets from the Sun and among themselves, found out the causes of the formation of large and small planets in different parts of the solar system and the difference in their composition. By calculations, the reasons for the rotational movement of the planets in one direction are justified.

The disadvantage of the hypothesis is the consideration of the origin of the planets is isolated from the formation of the Sun - the system defining member. The concept is not devoid of an accident element: gripping by the sun of interstellar matter. Indeed, the possibility of seizing the sun of a lambidly large meteorite cloud is very small. Moreover, according to calculations, such a seizure is possible only with the gravitational assistance of a drchy, close to the star. The probability of a combination of such conditions is so insignificant that it makes the opportunity to capture the Sun of the interstellar with an exceptional event.

Hypothesis V.G. Fesenkov

The works of Astronomom V.A. Ambartzumian, who proved the continuity of the formation of stars as a result of condensation of a substance from the discharged gas-dust and dust nebulae, allowed Academician V.G.Feshenkov to nominate a new hypothesis (1960), which binds the origin of the solar system with the general patterns of formation of matter in cosmic space. Fesenkov believed that the formation process of the planets was widespread in the universe, where there are many planetary systems. In his opinion, the formation of the planets is associated with the formation of new stars arising from a thickening of the initially sparse substance within one of the gigantic nebulae ("globule"). These nebulae were very sparse matter (about 10 g / cm density) and consisted of hydrogen, helium and a small amount of heavy metals. First, the Sun, which was a hotter, massive and rapidly rotating star, was formed in the Globulu core, which was currently. The evolution of the Sun was accompanied by repeated emissions of matter into the protoplanetic cloud, as a result of ignorance lost part of the mass and transparent planets a significant proportion of its moment of movement. Calculations show that with non-stationary emissions of matter from the subsoil of the sun, the actual observed ratio of the moments of the amount of movement of the sun and the protoplanetic cloud (and, consequently, the planets). Under time the formation of the sun and the planets is proved by the same age of the Earth and the Sun.

As a result of the compaction of the gas-dust cloud, star-shaped condensation was formed. Under the influence of rapid rotation of the nebula, a significant part of the gas-dusty matter was increasingly removed from the center of the nebula on the plane of the equator, forming something like a disk. Gradually, the compaction of the gas-dusty nebula led to the formation of planetary concentrations that subsequently formed modern planets of the solar system. Unlike Schmidt, Fasenkov believes that gas-dust nebula was in a hot state. His great merit is the substantiation of the law of planetary distances depending on the density of the medium. V.G.Feshenkov mathematically substantiated the reasons for the resistance of the moment of the number of movement of the solar system of the loss of the substance of the Sun in the selection of matter, as a result of which its rotation was slowed down. V.G.Feshenkov also argues in favor of the return movement of some satellites of Jupiter and Saturn, explaining this by the capture of asteroid planets.

The major role of the Fesenkov attached to the processes of radioactive decay of isotopes K, u, th and others, the content of which was then significantly higher.

To date, the ordictically calculated a number of options for radiogenic heating of the subsoil, the most detailed of which is proposed by E.A.Lubimova (1958). In accordance with these calculations in one billion years, the temperature of the subsoil of the earth at the depth of several hundred kilometers to reaches iron melting. By this time, apparently, the beginning of the formation of the core of the Earth, presented by the metals and nickel and nickel to its center. Later, with a further increase in temperature, the mantle began to sell the most low-melting silicates, which, as a result of a small density, rose up. This process, theoritically and experimentally studied A.P. Vinogradov, explains the formation of the earth's crust.

It also needs to be noted two hypotheses that developed by the end of the 20th century. They considered the development of the Earth, without affecting the development of the solar system as a whole.

The land was entirely melted and in the process of depleting internal thermal resources (radilating elements) gradually began to cool. In the upper part formed a solid crust. And with a decrease in the volume of the cooled planet, this crust was broken, and folds and other form of relief were formed.

There was no complete melting substance on Earth. In a relatively loose protoplanet, local foci of melting was formed (this term introduced academician of grapes) at a depth of about 100 km.

Gradually, the number of radioactive elements decreased, and the temperature of the LOP decreased. Magma was crystalized and fell to the bottom of the first high-temperature minerals. The chemical composition of these minerals was different from the composition of Magma. Heavy elements were removed from magma. And the residual melt is relatively enriched with light. After 1 phase and further decrease in the temperature from the solution, the following phase of minerals was crystalized, also containing more heavy elements. So there was a gradual cooling and crystalization of bobbs. From the initial ultrabasic composition of the magma, a magma of the main balsovoy composition was formed.

In the upper part of the hop, a fluid hat formed (gas-liquid). Balzat magma possessed mobility and fluidity. She broke out of the bobbins and flowed to the surface of the planet, forming the first rigid basalt crust. The fluid hat also broke through to the surface and, mixed with the remnants of derivable gases, formed the first atmosphere of the planet. As part of the primary atmosphere were nitrogen oxides. N, not, inert gases, CO, CO, NS, HCl, HF, CH, Water Couples. Free oxygen was almost no. The surface temperature of the Earth was about 100 s, there was no liquid phase. The inside of a rather loose protoplanets had a temperature close to melting point. Under these conditions, the processes of heatAssoperenos inside the Earth are intensely protected. They took place for thermal convection flows (TCP). Especially important TCP arising in surface layers. There developed cellular thermal structures, which sometimes rebuilt into the same structure. The ascending TCP passed the pulse of the movement to the surface of the planet (balcovaya crust), and the stretching zone was created on it. As a result of stretching in the zone of the TCP, a powerful long-term long-term length from 100 to 1000 km is formed. They were called rift faults.

The surface temperature of the planet and its atmosphere cools below 100 C. water is condensed from the primary atmosphere and the primary hydrosphere is formed. The landscape of the Earth is a shallow ocean with a depth of 10 m, with separate volcanic pseudo-thestrokes exposed during the sings. There was no constant sushi.

With a further decrease in the temperature of the LOP, the latter was fully sworn and turned into rigid crystalline kernels in the depths of a rather loose planet.

Surface cover of Platya was destroyed by aggressive atmospheric and hydrosphere.

As a result of all these processes, the formation of magmatic, sedimentary and metamorphic rocks was the formation.

Thus, hypotheses about the origin of our planet explain modern data on its structure and position in the solar system. And the development of space, the launches of satellites and space missiles give many new facts for practical testing of hypotheses and further improvement.

Literature

1. Questions of Cosmogony, M., 1952-64

2. Schmidt O. Yu., Four lectures on the theory of origin of the Earth, 3 ed., M., 1957;

Levin B. Yu. The origin of the Earth. "Izv. Academy of Sciences of the USSR Physics of the Earth ", 1972, No. 7;

Safronov V.S., Evolution of the Supplemental Cloud and Earth Education and Planets, M., 1969; .

Kaplan S. A., star physics, 2 ed., M., 1970;

Problems of modern cosmogony, ed. V. A. Ambartsumian, 2 ed., M., 1972.

Arkady Leokum, Moscow, "Julia", 1992

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The story of our planet still keeps a lot of mysteries. Scientists of different areas of natural science invested their contribution to the study of the development of life on earth.

It is believed that the age of our planet is about 4.54 billion years. All this time interval is made to divide into two main stages: plywood and doxcr. These stages are called eoan or eonotable. The aons in turn are divided into several periods, each of which is distinguished by a set of changes in the geological, biological, atmospheric state of the planet.

1. Precambria, or Cryptose - This is Eon (temporary land development interval), covering about 3.8 billion years. That is, Precambria is the development of the planet from the moment of formation, the formation of the earth's crust, the protoocyan and the emergence of life on earth. By the end of the Precambrian on the planet, high-organized organisms with a developed skeleton were already widespread.

The Eon includes two more eonothemes - Qatarhai and Archey. The latter, in turn, includes 4 eras.

1. Qatarhey - this is the time of the formation of the Earth, but there was no nor or earthly crust. The planet was still a cold cosmic body. Scientists suggest that during this period there were already water on Earth. Qatarhey lasted about 600 million years.

2. Archey covers a period of 1.5 billion years. During this period, there were no oxygen on Earth, there was a formation of sulfur, iron, graphite, nickel deposits. The hydrosphere and the atmosphere were a single vapor-gas shell, which covered the globe with a dense cloud. The sun's rays through this veil almost did not penetrate, so darkness reigned on the planet. 2.1 2.1. Eoarhey - This is the first geological era, which lasted about 400 million years. The most important event of EaChea is the formation of the hydrosphere. But there were still few water, the reservoirs existed separately from each other and have not yet merged into the world ocean. At the same time, the earth's bark becomes hard, although the asteroids are still bombarded. On the outcome of Eoarhey, the first in the history of the planet's supercontinent - Vaalbara is formed.

2.2 Paleoarhey - The next era, which also lasted approximately 400 million years. During this period, the kernel of the Earth is formed, the tension of the magnetic field increases. The day on the planet lasted only 15 hours. But the oxygen content increases in the atmosphere due to the activities of the bacteria. The remains of these first forms of Paleoarha's era of life were found in Western Australia.

2.3 Mesoarhey Also lasted about 400 million years. In the Mesoarha Era, our planet covered the shallow ocean. Sushi plots were small volcanic islands. But already during this period the formation of a lithosphere begins and the mechanism of tectonics of plates is launched. At the end of Mesoarhery, the first ice age is observed, during which snow and ice on Earth are formed on Earth. Biological species are still presented by bacteria and microbial forms of life.

2.4 Neoarhey - the final era of the Archean Eon, the duration of which is about 300 million years. Colonies of bacteria at this time forms the first stromatolites (limestone deposits). The essential event of Neoarhey is the formation of oxygen photosynthesis.

II. Proterozoa - One of the longest time segments of the history of the Earth, which is customary to divide for three eras. During the Proterezhoy, the ozone layer appears for the first time, the global ocean reaches almost modern volume. And after a long-lasting Guronian glaciation on Earth, the first multicellular forms of life appear - mushrooms and sponges. It is customary to divide for three eras, each of which contained several months.

3.1 Paleo-Proteroza - The first era of Proterozoy, which began 2.5 billion years ago. At this time, a lithosphere is fully formed. But the former forms of life due to an increase in oxygen content almost extinct. This period was called an oxygen catastrophe. By the end of the era on Earth, the first eukaryotes appear.

3.2 Meso-Proteroza Little approximately 600 million. The most important events of this era: the formation of continental masses, the formation of the supercontinent of the birthplace and the evolution of sexual reproduction.

3.3 Neo-Proteroza. During this era, the birthplace disintegrates about 8 parts, the world's super pool ceases its existence, and on the outcome of the era, the Earth almost to the equator is covered with ice. In the neoproterozoic era, living organisms first begin to acquire a solid shell, which will continue to serve as the basis of the skeleton.

III. Paleozoic - The first era of Puerrozoic Eon, which began approximately 541 million years ago and lasted about 289 million years. This is the era of the appearance of an ancient life. The supercontinent of the Gondwana combines the southern continents, a little later, the rest of the sushi are attached to it and Pangea appears. Climatic belts are beginning to be formed, and the flora and fauna are presented mainly by marine species. Only by the end of the Paleozoa begins the development of sushi, and the first vertebrates appear.

Paleozoic era is conditionally divided by 6 periods.

1. Cambrian period lasted 56 million years. During this period, the main rocks are formed, and the mineral skeleton appears in living organisms. And the most important event of Cambria is the emergence of the first arthropods.

2. Ordovik period - The second period of Paleozoic, which lasted 42 million years. This is the era of the formation of sedimentary breeds, phosphorites and combustible shale. The organic world of Ordovic is represented by sea invertebrates and blue-green algae.

3. Silician period covers the following 24 million years. At this time, almost 60% of living organisms that existed before are extinct. But the first crystal and bone fish appear in the history of the planet. On land, the silicon marks the emergence of vascular plants. Superkontinets come closer and form Laurelasia. By the end of the period, melting of ice was marked, the sea level rose, and the climate became softer.

4. Devonian period It is distinguished by the rapid development of various forms of life and the development of new environmental niches. Devon covers a time interval of 60 million years. The first terrestrial vertebrates appear, spiders, insects. In animals sushi form lungs. Although, still, the fish prevail. The kingdom of flora of this period is represented by the suspension, horsages, plauns and the memorable.

5. Coal period often called carbon. At this time, the laure is faced with Gondwayn and a new supercontinent of Pangea appears. The new ocean - Tetis is formed. This is the time of the appearance of the first amphibians and reptiles.

6. Perm period - The last period of Paleozoic, completed 252 million years ago. It is assumed that at this time a large asteroid fell to Earth, which led to a significant change in climate and extinct almost 90% of all living organisms. Most of the sushi are covered with sands, the most extensive deserts appear, which only existed in the entire history of the earth's development.

IV. Mesoza - The second era of Puerozoic Eon, which lasted almost 186 million years. At this time, continents acquire almost modern outlines. A warm climate contributes to the rapid development of life on Earth. Giant ferns disappear, and coated plants appear on the shift. Mesoza is the era of dinosaurs and the appearance of the first mammals.

In the Mesozoic era, three periods are distinguished: TRIAS, Yura and Chalk.

1. Triassic period lasted just over 50 million years. At this time, Pangea begins to split, and the inner seas gradually minor and dry. The climate is soft, zones are not pronounced. Almost half of the plant sushi disappears, as the deserts are spread. And in the kingdom of fauna, the first warm-blooded and land reptiles appear, which raised the ancestors of dinosaurs and birds.

2. Jurassic covers the gap of 56 million years. The wet and warm climate reigned on Earth. Sushha is covered with thickets of ferns, pines, palm trees, cypresses. Dinosaurs reign on the planet, and numerous mammals were distinguished while small growth and thick wool.

3. Cretaceous period - The longest period of the Mesozoic, which lasted almost 79 million years. The split continents almost ends, the Atlantic Ocean increases significantly in the amount, ice cover are formed on the poles. An increase in the aqueous mass of oceans leads to the formation of a greenhouse effect. At the end of the chalk period there is a catastrophe, the reasons for which are still not clear. As a result, all dinosaurs and most types of reptiles and gifted plants were extinct.

V. Cenozoa - This is the era of animals and a man of reasonable, which began 66 million years ago. The continents at this time acquired their modern outline, Antarctica took the South Pole of the Earth, and the oceans continued to increase. The plants and animals survived after the catastrophe of the Cretaceous period were in a completely new world. Each continent began to form unique communities of life forms.

The Cenozoic Era is divided into three periods: Paleogen, Neogen and Quaternary.

1. Paleogenic period Approximately 23 million years ago ended. At this time, a tropical climate reigned on Earth, Europe hid under the evergreen tropical forests, only deciduous trees grew in the north of the continents. It was during the period of Paleogen that the mammals are rapid development.

2. Neugenic period covers the next 20 million years of the development of the planet. Whales and manochable appear. And, although the saber tigers and Mastodonts still roam the land, the fauna more and more becomes modern features.

3. Quaternary period Began more than 2.5 million years ago and continues until now. Two major events characterize this time segment: the ice age and the appearance of a person. The glacier era fully completed the formation of climate, flora and fauna of continents. And the emergence of man marked the beginning of civilization.

In modern astronomy, a concept has been adopted Cold initial state planetswhich under the influence of electromagnetic and gravitational forces were formed as a result of combining the solid particles of the gas-dust cloud surrounding the sun. The protoplanetic nebula consisted of a dense interstellar substance, which could be formed as a result of an explosion relative to the underground supernova, who accelerated the process of gas condensation.

The pressure level in the protoplanetic cloud was such that the substance from gas condensed immediately into solid particles, bypassing the fluid shape. At some point, the gas density was so high that seals were formed in it. Founding with each other, gas clots continued to shrink and compact, forming the so-called supplemental bodies.

The formation of additional celent bodies continued tens of thousands of years. The collision of these bodies with each other led to the fact that the largest of them began to more increase in size in size, as a result of which planets were formed, including our land.

Early Earth Development History Includes three phases of evolution: accretion (birth); melting the external sphere of the globe; Primary bark (lunar phase).

Phase accretion It was a continuous fallout on the growing land, an increasing number of large bodies, enlightening in flight during collisions between themselves, as well as as a result of attraction of more remote small particles to them. In addition, the largest objects - planezimals, achieved many kilometers in the diameter, fell on Earth. In the accretion phase, the Earth acquired approximately 95% of the modern mass. It took about 17 million years (though, some researchers increase this period to 400 million years). At the same time, the Earth remained a cold cosmic body, and only at the end of this phase, when the extremely intense bombardment began with large objects, a strong heating occurred, and then the full melting of the substance of the surface of the planet.

The melting phase of the external sphere of the globe came in the interval of 4-4.6 billion years ago. At this time, there was a generallylanetary chemical differentiation of a substance, which led to the formation of the central nucleus of the Earth and enveloping his mantle. Later the earth is formed.

In this phase, the surface of the Earth was the ocean of severe molten mass with gases escaped from it. It was continued to rapidly fall small and large cosmic bodies, causing bursts of heavy liquid. Above the hot ocean, I will ring completely tightened with thick clouds of the sky, from which there could not fall a drop of water.

Moon Phase - The cooling time of the molten substance of the Earth as a result of radiation of heat into space and the weakening of the meteorite bombardment. So formed primary bark of basalt composition. At the same time, the formation of the granite layer of the mainland bark took place. True, the mechanism of this process is still not clear. The lunar phase passed the gradual cooling of the surface of the Earth on the melting point of basalts, component of 800-1000 to 100 ° C.

When the temperature dropped below 100 ° C from the atmosphere dropped all the water covered with the earth. As a result, surface and soil drains were formed, water bodies, including the primary ocean, appeared.

In one galaxy there are about 100 billion stars, and there are 100 billion galaxies in our universe. If you were thinking to go on a journey from the ground to the very edge of the Universe, it would take more than 15 billion years old, provided that you will move at the speed of light - 300,000 km per second. But where did the cosmic matter come from? How did the universe originate? The history of the land has about 4.6 billion years. During this time, it arose and died many millions of plants and animals; grew up and treated in dust the highest mountain ranges; Those rushed continuity on the part and ran into different directions, then came across each other, forming new giant sushi arrays. Where do we all know all this? The fact is that, despite all the catastrophes and cataclysms, which is so rich in the history of our planet, surprisingly much of her stormy past is imprinted in rocks that exist and today, in fossils, which are found in them, as well as in the organisms of living beings living on earth these days. Of course, this chronicle is incomplete. We only come across her fragments, the voids are gaping between them, entire chapters fall out of the story, extremely important for understanding what happened in fact. Nevertheless, even in such a trimmed form, the history of our Earth will not give way to fascinating any detective novel.

Astronomers believe that our world arose as a result of a large explosion. Exploding, a giant fireball ranked in the space of matter and energy, which subsequently thickened, forming billions of stars, and those, in turn, united into numerous galaxies.

The Big Bang Theory.

The theory that most modern scientists adheres to, argues that the Universe was formed as a result of the so-called large explosion. An incredibly hot fiery ball, the temperature of which reached billion of degrees, at some point exploded and scattered in all directions of energy flows and particles of matter, giving them a colossal acceleration.
Any substance consists of tiny particles - atoms. Atoms are the smallest material particles that can take part in chemical reactions. However, they, in turn, consist of even smaller, elementary, particles. There are many varieties of atoms that are called chemical elements in the world. Each chemical element includes atoms of certain sizes and weights and differs from other chemical elements. Therefore, during the chemical reactions, each chemical element behaves only in one inherent. All in the universe, from the largest galaxies to the smallest living organisms, consists of chemical elements.

After a big explosion.

Since the fiery ball, scattered apart as a result of a large explosion, had a colossal temperature, tiny particles of matter had at first too much energy and could not connect with each other to form atoms. However, after about a million years, the temperature of the Universe dropped to 4000 "C, and various atoms began to be formed from elementary particles. At first, the easiest chemical elements - helium and hydrogen occurred. Gradually, the universe was cooled and more severe elements were harvested and formed. The process of formation of new atoms and elements It continues to this day in the depths of such stars, like, for example, our sun. Their temperature is extremely high.
The universe cooled. Newly formed atoms gathered in giant clouds of dust and gas. Dust particles faced each other, merged into a single whole. Gravitational forces attracted small objects to larger. As a result, galaxies, stars, planets were formed in the Universe over time.

The land has a molten core, rich in iron and nickel. The earth's crust consists of lighter elements and as it were, it floats on the surface of partially molten rocks forming the land mantle.

Expanding universe.

The big explosion turned out to be so powerful that the whole matter of the universe was scattered at a huge speed on space space. Moreover, the Universe continues to expand to this day. We can confidently assert this because remote galaxies are still postponed from us, and the distances between them are constantly increasing. So, once the galaxies were located much closer to each other than these days.

No one knows exactly how the solar system was formed. The main theory says that the sun and planets were formed from the envious clouds of space gas and dust. More dense parts of this cloud with the help of gravitational forces attracted an increasing amount of substance from the gravitational forces. As a result, the sun arose from it and all his planets.

Microwaves from the past.

Based on the assumption that the universe was formed as a result of a "hot" large explosion, that is, it arose from a giant fiery ball, scientists tried to calculate, to what extent it had to cool to date. They concluded that the temperature of the intergalactic space should be about -270 ° C. The temperature of the Universe scientists determine the intensity of microwave (thermal) radiation, which is from the depths of the cosmos. The measurements confirmed that it actually constitutes about -270 "with.

What is the age of the universe?

To find out the distance to one or another galaxy, the astronomers determine its size, brightness and the color of the light emitted by it. If the theory of a large explosion is correct, then, that means all the existing galaxies now were originally gritted into one super-plate and hot fireball. It is enough for you to divide the distance from one galaxy to the other to the speed, with which they are removed from each other to establish how long ago they constituted a single integer. This will be the age of the universe. Of course, this method does not allow to obtain accurate data, but still it gives reason to believe that the age of the universe is 12 to 20 billion years.

The lava flow follows from the Kilauea Volcano Crater, located on the O-ve Hawaii. When Lava goes to the surface of the Earth, it freezes, forming new rocks.

The formation of the solar system.

The galaxies were formed, in all likelihood, after about 1 - 2 billion years after a large explosion, and the solar system arose about 8 billion years later. After all, the matter was distributed in the space by no means evenly. More dense areas, thanks to the gravitational forces, attracted more and more dust and gas. The dimensions of these areas rapidly increased. They turned into gigantic swirls of dust and gas clouds - the so-called nebula.
One such nebula - namely the solar nebula - thickening, formed our sun. From other parts of the cloud, a bunch of substances occurred, which became planets, including the Earth. They held on their near-air orbits with a powerful gravitational field of the Sun. As the gravitational forces attracted a solar particle closer and closer to each other, the sun became less and more dense. In this case, monstrous pressure occurred in the sunny core. It was transformed into colossal thermal energy, and this, in turn, accelerated the course of thermonuclear reactions inside the Sun. In (a result, new atoms were formed and even more heat was highlighted.

The emergence of conditions for life.

Approximately the same processes, although at a much smaller scale, occurred on Earth. The earth's core was swirling rapidly. Due to nuclear reactions and decay of radioactive elements in the depths of the Earth, so much heat was distinguished that the formulations of its rocks were melted. Lighter substances rich in silicon are similar to glass mineral, they separated in the earth's core from more dense iron and nickel and formed the first earthly bark. After about a billion years, when the Earth cooled significantly, the earth's crust hardened and turned into a strong outer sheath of our planet consisting of solid rocks.
Cooling, the Earth threw many different gases from its core. It usually happened when volcanic eruptions. Light gases, such as hydrogen or helium, mostly disappeared into outer space. However, the force of attraction of the Earth was large enough to keep heavier gases at its surface. They were the basis of the earth's atmosphere. Part of water vapor from the atmosphere was condensed, and oceans arose on Earth. Now our planet was completely ready to become a cradle of life.

Birth and death of rocks.

Ground land is formed by solid rocks, often covered with a layer of soil and vegetation. But where do these rock breeds come from? New rock rocks are formed from a substance that is born deep in the depths of the Earth. In the lower layers of the earth's crust, the temperature is much higher than the surface of the surfaces, and their rock formations are under tremendous pressure. Under the influence of heat and pressure, rock breeds bend and soften, or even melted at all. As soon as in the earth's crust, a weak place is formed, molten rocks - they are called magma - break into the surface of the Earth. Magma follows from the stalls of volcanoes in the form of lava and applies to a large area. Thoroughly, the lava turns into a solid rock.

Explosions and fiery fountains.

In some cases, the birth of rocks is accompanied by ambitious cataclysms, in others it goes quietly and unnoticed. There are many varieties of magma, and different types of rocks are formed. For example, basalt magma is very fluid, easily goes to the surface, spreads wide streams and quickly freezes. Sometimes it breaks out of the vulcan agriculture with a bright "fiery fountain" - this happens when the earth bark does not withstand its pressure.
Other types of magma are much thicker: their density, or consistency, is more like a black molasses. The gases contained in such magma with great difficulty make their way to the surface through its dense mass. Remember how easily air bubbles break out of boiling water and how slowly it happens when you heat something more thick, for example, Kissel. When a more dense magma rises closer to the surface, the pressure on it decreases. Dissolved gases tend to expand, but cannot. When Magma finally breaks out, the gases expand so rapidly that a grand explosion occurs. Lava, wreckage of rocks and ashes scatter in all directions as shells released from guns. Such an eruption happened in 1902 on the O-ve Martinique in the Caribbean. The catastrophic eruption of the volcanic Moptapy Pele completely destroyed the port of Sep-Pierre. About 30,000 people died.

The formation of crystals.

Mountain breeds formed from the cooled lava are called volcanic, or erupted, rocks. While the lava cools, the minerals contained in the molten rocks are gradually converted into solid crystals. If the lava cools fast, the crystals do not have time to grow and remain very small. This happens when the basalt is formed. Sometimes the lava is cooled so quickly that it turns out a smooth glass breed from it, which does not contain crystals, such as obsidian (volcanic glass). A similar, as a rule, it happens during underwater eruption or when small lava particles are thrown out of the vulcan ventilation high in cold air.

Erosion and weathered rocks in Canyon Cydar Breix, Utah, USA. These canyons were formed as a result of the erosion impact of the river, which lasted their channel through the layers of sedimentary rocks, "extruded" up the movements of the earth's crust. The exposed mountain slopes gradually weathered, and the fragments of rocks were formed on them stony scree. In the midst of these shots, protrusions stick out all the solid rocks, which form the edges of the canyons.

Certificate of missing.

The dimensions of the crystals contained in volcanic rocks allow us to judge how quickly the lava cooled and at what distance from the surface of the earth it ran. Before you a piece of granite, as it looks in polarized light under a microscope. Various crystals have different color in this image.

Gneis is a metamorphic rock formation formed from a sedimentary breed under the influence of heat and pressure. A drawing of multi-colored bands that you see on this piece of gneiss, allows you to determine the direction in which the earth's crust, moving, pressed on rock layers. So we get an idea of \u200b\u200bthe events that took place 3.5 billion years ago.
In the rocks and faults (ruptures) in rocks, we can judge in which direction acted with colossal stresses in the earth's crust in the long-lasting geological era. These folds arose as a result of the burning movements of the earth's crust, which began 26 million years ago. In these places, the monstrous forces squeezed the layers of sedimentary rocks - and folds were formed.
Magma does not always reaches the surface of the Earth. It can linger in the lower layers of the earth's crust and then cools much slower, forming amazing major crystals. This is how granite arises. The magnitude of the crystals in some barers allows you to establish how many millions of years ago this breed was formed.

Huduz, Albert Province, Canada. Rain and sand storms destroy soft rocks faster than solid, and as a result, remains (protrusions) with fancy outlines arise.

Sediment "sandwiches".

Not all rocks are similar to volcanic, such as granite or basalt. Many of them consist of a variety of layers and look like a huge stack of sandwiches. They were formed once out of destroyed by the wind, the rains and rivers of other rocks, whose debris was washed into the lake or the sea, and they donkeys on the bottom under the thickness of water. Gradually, such precipitation accumulates a huge amount. They are roughened by each other, forming layers thick hundreds and even thousands of meters. The water of the lake or the sea presses on these sediments with colossal power. Inside them, the water is squeezed out, and they are crushed into a dense mass. At the same time, mineral substances previously dissolved in extruded water, as if cementing all this mass, and as a result, a new rock formation is formed, which is called sediment.
Both volcanic, and sedimentary rocks can be pushed up upward under the influence of the movements of the earth's crust, forming new mining systems. Envasional forces participate in the mountain formation. Under their impact, rock rocks are either very hot, or monstrously compress. At the same time, they are transformed - transform: one mineral can turn into another, the crystals are flattened and take another location. As a result, the place of one mountain breed occurs another. Mountain breeds formed during the transformation of other rocks under the influence of the aforementioned forces are called metamorphic.

Nothing forever, even the mountains.

At first glance, nothing can be stronger and more durable than a huge mountain. Alas, it is just an illusion. If it is based on a geological scale of time, where the account goes to millions and even hundreds of millions of years, then the mountains turn out to be as transient as everything else, including us with you.
Any rock, as soon as it starts to be exposed to the atmosphere, will instantly collapse. If you take a look at the fresh chip of the rock or chuck naked, you will see that the newly formed rock surface is often completely different color than the old, who has long spent the air. This is explained by the effect of oxygen contained in the atmosphere, and in many cases - and rainwater. Because of them, various chemical reactions occur on the surface of the rock, gradually changing its properties.
Over time, these reactions lead to the release of minerals, fastening the breed, and it begins to crumble. Crocheted cracks are formed in the breed, in which water penetrates. Freezing, this water expands and breaks the breed from the inside. When the ice is melted, such a breed is simply falling apart in pieces. Very soon, the falling pieces of the breed will melt rain. This process is called erosion.

Glacier Mwer in Alaska. The destructive impact of the glacier and stones frightened in it from the bottom and from the sides, gradually causes the erosion of the walls and the bottom of the valley, on which it is moving. As a result, long stripes of rock fragments are formed on ice - the so-called moraine. When merging two adjacent glaciers, their moraine are connected.

Water-destroyer.

The pieces of the destroyed rock end up in the river. The current drags them on the river bed and becomes them the rock, which forms itself, until the surviving fragments are finally the quiet refractory at the bottom of the lake or the sea. Frozen water (ice) has even greater destructive power. Glaciers and glacier covers of the fiber behind themselves a variety of large and small wreckage of rocks, frozen in their ice sides and bugs. These debris are made deep furrows in the rocks, which are moving glaciers. The glacier can carry the fragments of the rocks that fall on it from above, for many hundreds of kilometers.

Sculptures created by the wind

The wind also destroys rocks. Especially often it happens in the deserts, where the wind transfers millions of smallest grain. Peschins mostly consist of quartz, extremely durable mineral. The whirlwind of the sand strikes the rock, knocking out all new and new grains from them.
Often the wind sticks out sand into large sandy hills, or dunes. Each gust of the wind applies a new layer of sands on the dune. The location of the slopes and the steepness of these sandy hills allow us to judge the direction and strength of the wind, which created them.

Glaciers do deep U-shaped valleys on their way. In Nantefronkone, Wales, the glaciers disappeared even in prehistoric times, leaving behind a wide valley, which is clearly large for a small river flowing through it now. A small lake in the foreground is overclocked by a strip of a particularly durable rock.