What kind of geological period do we live in? The history of the geological development of the Earth.

The emergence of land and early stages of its formation

One of the important tasks of modern natural science in the field of earth science is to restore the history of its development. According to modern cosmogonic ideas, the Earth has formed from a gas-diluted in the protocoule system. One of the most likely options for the occurrence of the Earth is as follows. Initially, the sun was formed and a flattening rotating region of the interstellar gas-free cloud under the influence of, for example, an explosion of a close supernovae. Then the evolution of the Sun and the milk-free nebulae with the transmission of an electromagnetic or turbulent-convective method of the moment of the amount of movement from the sun by the planets was occurring. In the subsequent "dust plasma" condensed into the rings around the Sun, and the material of the rings formed the so-called planezimali, which condensed to the planets. After that, a similar process was repeated around the planets, which led to the formation of satellites. It is believed that this process took about 100 million years.

It is assumed that further as a result of the differentiation of the substance of the Earth under the influence of its gravitational field and radioactive heating, various in the chemical composition, the aggregate state and the physical properties of the shell - the geosphere of the Earth were developed and developed. A heavier material formed a core, which is probably made of iron with an admixture of nickel and sulfur. The mantle remained slightly smaller elements. According to one of the hypotheses, the mantle is composed of simple aluminum oxides, iron, silicon titanium, etc. The composition of the earth's crust has already been mentioned in sufficient detail in § 8.2. It is folded easier silicates. Even lighter gases and moisture have formed a primary atmosphere.

As already mentioned, it is assumed that the Earth was born from the accumulation of cold solids, which dropped out of gas-penetrating nebula and sticking out under the influence of mutual attraction. As the planet grows, it was heated as a result of the collision of these particles that have reached several hundred kilometers, like modern asteroids, and the release of warmth not only known to us now in the crust of natural -radoactive elements, but also more than 10 outlets with the radioactive isotopes AI, BE, Cl and others. As a result, the complete (in the kernel) or partial (in the mantle) melting substance could occur. In the initial period of its existence, about 3.8 billion years, the land and other planets of the earth group, as well as the moon were subjected to enhanced bombardment with small and large meteorites. The consequence of this bombardment and earlier collision of the planezimyli could be the allocation of volatile and the beginning of the formation of a secondary atmosphere, since the primary, consisting of gases captured during the formation of the Earth, most likely quickly dissipated in outer space. A slightly later to form a hydrosphere. The atmosphere and hydrosphere formed in this way were replenished in the process of degassing the mantle at volcanic activity.

The fall of large meteorites created extensive and deep craters like the currently observed at the Moon, Mars, Mercury, where the traces of them are not erased by subsequent changes. Crater formation could provoke magma's outpouring with the formation of basalt fields like covering the lunar "sea". So, probably formed the primary bark of the Earth, which, however, was not preserved on its modern surface, with the exception of relatively small fragments in the "more young" cortex of continental type.

This bark, which contains already granites and GNius, however, with a smaller content of silica and potassium, than in the "normal" granites, appeared at the turn of about 3.8 billion years and is known to us on exposures within the crystal shields of almost all continents. The method of formation of ancient continental bark is still largely unclear. As part of this cortex, ubiquitous metamorphiced in high temperatures and pressures, the breeds are found, the textural features of which indicate the accumulation in the aquatic environment, i.e. This remote era has already existed a hydrosphere. The emergence of the first bark, similar to modern, required the receipt of large amounts of silica, aluminum, alkalis, while mantle magmatism now creates a very limited amount of breeds enriched with these elements. It is believed that 3.5 billion years ago, the sero-coil bark was widespread on the square of modern continents, named as the prevailing type of the solo rocks. In our country, it, for example, is known on the Kola Peninsula and in Siberia, in particular in the r. Aldan.

Principles of Periodization of the Geological History of the Earth

Further events in geological time are often determined, according to relative geochronology,categories of "Ancient", "Younger". For example, some era of an ancient one else. Separate segments of geological history are called (in order to reduce their duration) zones, eras, periods, epochs, centuries. Their detection is based on the fact that geological events are imprinted in rocks, and sedimentary and volcanogenic rocks are located in the earth's crust layers. In 1669, N. The wall set the law of a sequence of simplicity, according to which the underlying seams of sedimentary rocks are ancient overlap, i.e. Formed earlier. Due to this, it was possible to determine the relative sequence of formation of layers, and therefore, the associated geological events.

The main in relative geochronology is biostratigraphic, or paleontological, method of establishing relative age and sequence of rocks. This method was proposed by W. Smith at the beginning of the XIX century, and then developed J. Kuvier and A. Bronaryar. The fact is that in most sedimentary rocks you can meet the remains of animals or plant organisms. J.B. Lamarc and Ch. Darwin found that animals and vegetable organisms during geological history were gradually improved in the struggle for existence, adapting to changing living conditions. Some animals and vegetable organisms at certain stages of the development of the Earth died, they came to replace others, more perfect. Thus, on the remnants of previously living more primitive ancestors found in some plast, one can judge on a relatively more than ancient age of this formation.

Another method of geochronological dismemberment of rocks, especially important to the dismemberment of the magmatic formations of the oceanic bottom, is based on the property of magnetic susceptibility of rocks and minerals formed in the magnetic field of the Earth. With a change in the orientation of the rock relative to the magnetic field or the field itself, a part of the "congenital" magnetization is maintained, and the polarity change is imprinted in changing the orientation of the residual magnetization of rocks. Currently, a transference scale has been established.

Absolute geochronology - the teaching of the measurement of geological time expressed in ordinary absolute astronomical units(years), - determines the time of occurrence, completion and duration of all geological events, primarily the time of formation or transformation (metamorphism) of rocks and minerals, as they are determined by the age of geological events. The main method here is the analysis of the ratio of radioactive substances and the products of their decay in rocks formed in different epochs.

The oldest rocks are currently installed in Western Greenland (3.8 billion years). The greatest age (4.1 - 4.2 billion years) was obtained by zircones from Western Australia, but Zircon here lies in a stirred state in Mesozoic sandstones. Taking into account the ideas about the simulty of education of all the planets of the solar system and the moon and the age of the most ancient meteorites (4.5-4.6 billion years) and the ancient lunar breeds (4.0-4.5 billion years), the age of the earth is taken equal to 4.6 billion years old.

In 1881, at the II International Geological Congress in Bologna (Italy), the main divisions of the combined stratigraphic (for the separation of layered sedimentary rocks) and the geochronological scale were approved. On this scale, the history of the earth was divided into four eras in accordance with the stages of the organic world development: 1) Archean, or Archeozoic - ERA of the most ancient life; 2) Paleozoic - Era of ancient life; 3) Mesozoic - Era of Middle Life; 4) Cenozoic - Era of a new life. In 1887, the Proterozoic - Era of the Primary Life was allocated from the Archean Era. Later, the scale was improved. One of the variants of the modern geochronological scale is presented in Table. 8.1. The Archean Era is divided into two parts: early (ancient 3500 million years) and late Archey; Proterozoic - also in two: early and late proteodes; The latter is distinguished by Rifey (the name happened from the ancient name of the Ural Mountains) and the Vendian periods. Plyozoic zones is divided into Paleozoic, Mesozoic and Cenozoic era and consists of 12 periods.

Table 8.1.Geochronological scale

The main stages of the evolution of the earth's crust

Let us briefly consider the main stages of the evolution of the earth's crust as a bone substrate, which developed the diversity of the surrounding nature.

ATaPXEE. more than a rather thin and plastic bark under the influence of the stretch experienced numerous solid breakdowns, through which basalt magma, filling the brains of hundreds of kilometers and width of many tens of kilometers, known as green-stone belts (these titles, they are obliged to the surface, known as green-stone belts (by this name, they are required to prevail basalt breeds). Along with Basaltami among the lava of the lower, the main part of the section of these belts is found high-charts, indicating a very large degree of partial melting of the mantle substance, which speaks of a high thermal stream, much exceeding modern. The development of greenland belts consisted in changing the type of volcanism in the direction of increasing the content of silicon dioxide in it (SiO 2), in the deformations of compression and metamorphism of sedimentary volcanogenic execution and, finally, in the accumulation of debris precipitation, indicating the formation of mountainous relief.

After changing several generations of greenland belts, the Archean stage of the evolution of the earth's crust ended 3.0 -2.5 billion years ago by the mass formation of normal granites with a predominance of K 2 O over Na 2 O. Granitization, as well as regional metamorphism, reached the highest level, led to The formation of a mature continental bark for most of the square of modern mainland. However, this bark was not sustainable enough: at the beginning of the Proterozoic era, she experienced crushing. At this time, a planetary challenge of faults and cracks, filled with dikes (planing-like geological bodies). One of them is a great dike in Zimbabwe - has a length of more than 500 km and a width of up to 10 km. In addition, for the first time the rift formation was manifested, the granted zones of bending, powerful sedimentation and volcanism. Their evolution led to creating at the end early Proterezhoya(2.0-1.7 billion years ago) folded systems that have reached the fragments of the Archean Continental Cora, which contributed to a new era of powerful granite formation.

As a result, by the end of the early Proterezhoya (by the end of 1.7 billion years ago), the mature continental bark existed for 60-80% of its modern distribution area. Moreover, some scientists believe that at this turn, the entire continental bark was a single array - the supercontinent Megajoy (a large land), which, on the other side of the globe, opposed the ocean - the predecessor of the modern Pacific - Megatalassa (large sea). This ocean was less deep than the modern oceans, because the growth of the hydrosphere due to the degassing of the mantle in the process of volcanic activity continues the entire subsequent history of the Earth, although more slowly. It is possible that the sample megatlass appeared even earlier, at the end of Archey.

In Qatarhey and the beginning of Archey, the first traces of life appeared - bacteria and algae, and in Late Archey, algae lime buildings were spread - Stromatolites. In Late Archee, it began, and in the early Proterozoa, a fundamental change in the composition of the atmosphere was completed: under the influence of the vital activity of plants, free oxygen appeared in it, while Qatarha and the early Archean atmosphere consisted of water vapor, CO 2, CO, CH 4, N, NH 3 and H 2 S with an admixture of NS1, HF and inert gases.

In late proteodes(1.7-0.6 billion years ago) Megagia began to gradually split, and this process was sharply intensified at the end of the proderer. Its trails are extended continental rift systems, buried at the base of the sedimentary cover of ancient platforms. Its the most important result was the formation of extensive intercontinental rolling belts - the North Atlantic, Mediterranean, Ural-Okhotsk, who divided the continents of North America, Eastern Europe, East Asia and the largest debris of Megagia - South Supercontinent Gondwan. The central parts of these belts developed on a newly formed in the process of riftogenesis of the ocean crust, i.e. The belt was ocean pools. Their depth gradually increased as the hydrosphere grows. At the same time, moving belts developed along the periphery of the Pacific Ocean, the depth of which also increased. The climatic conditions became more contrasting, as evidenced by the appearance, especially at the end of the proderer, glacial sediments (Tillites, ancient moraine and water sediments).

Paleozoic stagethe evolution of the earth's crust was characterized by the intensive development of moving belts - intercontinental and outbound-continental (the latter on the periphery of the Pacific Ocean). These belts dismetected to the outskirts of the sea and island arcs, their sedimentary volcanogenic stratas were tested by complex folding-overalls, and then sketch-shift deformations, granites were introduced into them and folded mining systems were formed on this basis. This process proceeded unevenly. It distinguishes a number of intensive tectonic epochs and granite magmatism: Baikal - at the very end of Proterezhoy, Salair (from the Sa Lair Ridge in Central Siberia) - at the end of Cambrian, Takovskaya (from the Takovsky Mountains in the East) - at the end of Ordovik, Caledonian ( From the ancient Roman name of Scotland) - at the end of the silica, the Acadian (Acadia - the old name of the Northeast States of the United States) - in the middle of Devon, Sudechka - at the end of the early carbon, Zalaska (from the r. Zale in Germany) - in the middle of early Perm. The first three tectonic epochs of the Paleozoic are often united in the Caledonian era of tectogenesis, the last three to the Gersinskaya, or Varisian. In each of the listed tectonic epochs, certain parts of moving belts turned into folded mountain structures, and after the destruction (denudation) included the foundation of young platforms. But some of them partially experienced intensification into the subsequent epochs of the property.

By the end of Paleozoic, intercontinental moving belts were completely closed and filled with folded systems. As a result of the dying of the north-Atlantic belt, the North American continent closed with Eastern European, and the last (after the completion of the development of the Ural-Okhotsk belt) - with Siberian, Siberian - with Sino-Korean. As a result, a supercontinent of laure was formed, and the dying of the western part of the Mediterranean belt led to his unification with the southern supercontinent - Gondwan - in one continental blockage - Pangayu. The eastern part of the Mediterranean belt at the end of the Paleozoic - the beginning of the Mesozoic turned into a huge bay of the Pacific Ocean, along the periphery of which folded mountain structures also rose.

Against the background of these changes in the structure and relief of the Earth, the development of life continued. The first animals appeared in the late Proterozoa, and at the very dawn of Puerozoic, there were almost all types of invertebrates, but they were still deprived of the shells or shells, which are known from Cambrian. In the silver (or already in Ordovic), the yield of vegetation on land began, and at the end of Devon there were forests that were the greatest spread in the coal period. Fish appeared in the silver, amphibians - in Carbon.

Mesozoic and Cenozoic era -the last major stage in the development of the structure of the earth's crust, which is marked by the formation of modern oceans and the separation of modern continents. At the beginning of the stage, in Triassa, there was still a Pangea, but already in the early Jurassic period, she split back to Laurelasia and Gondwan due to the emergence of the latitudinal Ocean of Tettis, stretching from Central America to Indochina and Indonesia, and in the West and in the East he was closed with the Pacific Ocean (Fig. 8.6); This ocean included the Central Atlantic. From here at the end of Yura, the process of liding continents spread to the north, creating during the Cretaceous period and the early Paleogen Northern Atlantic, and starting with Paleogen - the Eurasian Basis of the Northern Ocean (amerazian pool originally as part of the Pacific Ocean). As a result, North America separated from Eurasia. In late Yura, the formation of the Indian Ocean began, and since the beginning of the chalk began to reveal from the south of South Atlantic. This meant the beginning of the decay of the Gondwana, which existed as a single whole for the entire Paleozoic. At the end of the chalk, North Atlantic was connected to South, separating Africa from South America. Then Australia separated from Antarctica, and at the end of Paleogen, the latter was separated from South America.

Thus, by the end of Paleogen, all the modern oceans took shape, all modern continents and the appearance of the Earth acquired a kind, mostly close to the current one. However, there were no modern mining systems.

From late Paleogen (40 million years ago), intensive mining began, which has reached the climax in the last 5 million years. This stage of the formation of young fold-to-cover mountainous structures, the formation of revived architectural and lump mountains is isolated as non-stock. In fact, the non-stock stage is a sub-stage of the Mesozoic-Cenozoic stage of the Earth's development, since it was at this stage that the main features of the modern land relief were made, starting from the distribution of oceans and continents.

At this stage, the formation of the main features of modern fauna and flora was completed. The Mesozoic Era was era reptile, mammals began to prevail in Cenozoa, and a man appeared in Late Pliocery. At the end of the early chalk, coated plants appeared and the sushus acquired herbal cover. At the end of Neogene and Anthropogen, the high latitudes of both hemispheres were covered by powerful mainland glaciation, the relics of which are the Ice Caps of Antarctica and Greenland. It was the third large glaciation in plywood: the first took place in the late Ordovik, the second - at the end of Carbon - the beginning of Perm; Both were distributed within the Gondwana.

Questions for self-control

What is a spheroid, ellipsoid and geoid? What are the parameters taken in our country of Ellipsoid? Why is it needed?

What is the internal structure of the Earth? Based on what is done about the conclusion about its structure?

What are the main physical parameters of the Earth and how do they change with the depth?

What is the chemical and mineralogical composition of the Earth? Based on what is done about the chemical composition of the entire Earth and the earth's crust?

What are the main types of earthly cortex currently?

What is a hydrosphere? What is a cycle of water in nature? What basic processes occur in the hydrosphere and its elements?

What is the atmosphere? What is her structure? What processes occur within its limits? What is the weather and climate?

Give the definition of endogenous processes. What endogenous processes do you know? Briefly describe them.

What is the essence of tectonics of lithospheric plates? What are its main provisions?

10. Give the definition of exogenous processes. What is the main essence of these processes? What endogenous processes do you know? Briefly describe them.

11. How do endogenous and exogenous processes interact? What are the results of the interaction of these processes? What is the essence of the theories V. Davis and V. Penka?

What are the modern ideas about the emergence of the Earth? How did her earlier formation occurred as a planet?

Based on what is performed by periodization of the geological history of the Earth?

14. How did the earth bark develop in the geological past of the Earth? What are the main stages of the development of the earth's crust?

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Billions of years ago, our land was bare, lifeless planet. And life appeared on her surface - those the first, the most primitive forms of living beings, the development of which led to an infinite variety of nature around us. How did this development occurred? How appeared on earth animals, plants, how were they modified? This book will be answered for some of these questions. Its author, an outstanding Soviet scientist Academician V. L. Komarov, described in it the history of the plant's plant world - from the simplest single-cell bacteria to modernly highly developed flowering plants. This long development path is drawn in close connection with the overall history of the Earth, with changes in its natural conditions, relief, climate. The book is written popularly, it is easy to read and will bring much benefit to the widest range of readers who have elementary information from the biology field in the scope of the school course.

Until now, in nature, only geological and climatic forces acted. As we have seen, they all the time strongly influenced vegetation and contributed to more and greater and greater variety. Now there was a completely new factor: a person.

Binding in the tertiary period, according to different estimates for 600,000 - 1,000,000 years before our time, in monkey-like forms, he met the Ice Age was still unarmed. But in many localities, it was impossible to flee from the glacier; The cold drove a man into the caves, who became his first dwelling, and forced to invent fixtures to maintain fire. From this point on, the person becomes the creature of industrial and, all overflowing its activities, begins to influence nature more than any living being. He drives the forest, raises the virgin, breaks through the channels, blows and rolls the whole mountains and generally changes the face of the Earth at its discretion.

In relation to vegetation, a person destroys the forest flora, destroys the plants of the steppes and many others and creates its own special world in their place, the world of cultural plants, which would never have ever, if not. The present period of the development of earthly vegetation is also characterized by the replacement of the person inherited from the previous times of flora cultural vegetation.

We have seen that the conditions of plant life on Earth were first put forward as pioneers of the primary settlement of the earth's crust, a group of bacteria known under the general title of chemotrophic, i.e., such, the powered by a small number of clearly pronounced, chemical reactions and does not need formed organic matter.

The age of bacteria was replaced by a century of algae, reaching in the waters of the ancient oceans a significant variety of forms and paintings.

A century of algae was replaced on the primary continuing ages of psulifitis, which gave vegetation, reminiscent of their general form and the size of the largest moss.

The ppilly age of psulfitis was replaced by a century of fervenous plants that have already formed extensive forests on swampy soils. This vegetation has contributed a lot to ensuring that the composition of the air and the accumulation of the mass of food substances made it possible the occurrence of first land vertebrates. Then the main masses of stone coal were accumulated.

A eyelid of fernamed replaced by a century of blocking plants. For the first time, the surface of the mainland has acquired a modern appearance and the possibility of the existence of higher animals has approached.

The eyelid eyelids changed to the gram of the eyelid of the flowering plants when they were formed on others all the existing plants.

It must be said that the onset of the new century or the period never ruined the former floral world. Always part of the past population of the Earth remained and continued to exist along with the new world. So, the bacteria with the appearance of the highest vegetation not only did not disappear, but also in the soil and in the organic matter, so generously created by higher plants, found new sources of existence for themselves. Algae, once developed, continue to grow and improving along with higher plants. They are also not competitors, because some inhabit the coastal seaside areas, others mostly land.

Finally, coniferous forests of our time continue to exist along with deciduous, and the shadow gives them to fern plants, since this heritage of a foggy and wet coal period is afraid of open habitats, where the sun's rays harm him, and is looking for shadows.

So the history of the earth's crust led to the creation of a rich and diverse world of plants, starting its work from the materials provided by the inorganic world, and graduating from the creation of what surrounds us and gives us everything necessary for life.

"Zoology and botany remain still collecting facts, while Paleontology is not joined - Cuvier, and soon the discovery of the cell and the development of organic chemistry. Thanks to this, comparative morphology and comparative physiology have been made possible, and since then both have become genuine sciences. "

F. Engels.

Geological time and methods of its definition

In the study of the Earth as a unique space object, the idea of \u200b\u200bits evolution occupies a central place, so an important quantitatively evolutionary parameter is geological time. Special science has been engaged in studying this time. Geochronology - geological summer. Geochronology may be absolute and relative.

Note 1.

Absolute Geochronology is engaged in determining the absolute age of rock, which is expressed in units of time and, as a rule, in millions of years.

The determination of this age is the rate of decay of the isotopes of radioactive elements. This speed is the magnitude of constant and on the intensity of physical and chemical processes does not depend. The determination of age is based on the methods of nuclear physics. Minerals containing radioactive elements in the formation of crystalline lattices form a closed system. This system accumulates radioactive decay products. As a result, you can determine the age of the mineral, if you know the speed of this process. Radium half-life, for example, is $ 1590 $ years, and a complete decay of the element will occur during $ 10 $ 5 times the superior half-life. Nuclear geochronology has its own leading methods - lead, potassium-argon, rubidium-strontium and radiocarbon.

Methods of nuclear geochronology made it possible to determine the age of the planet, as well as the duration of the ER and periods. Radiological measurement of time offered P. Curie and E. Rootford At the beginning of the $ XX $ century.

Relative geochronology operates such concepts as "early age, middle, late." There are several developed methods for determining the relative age rocks. They are combined into two groups - paleontological and non-remontological.

First Play the main role due to its versatility and widespread use. The exception is the absence of organic residues in the rocks. With the help of paleontological methods, the remains of ancient extinct organisms are studied. For each layer of rocks, its complex of organic residues is characteristic. In each young layer of remnants of high-organized plants and animals will be greater. The higher the layer is, the one is younger. Similar pattern was established by the Englishman W. Smith. It owns the first geological map of England, on which rock rocks were divided by age.

Nepalontological methods The determination of the relative age of rocks is used in cases of absence in them organic residues. More efficient then will be stratigraphic, Lithological, Tectonic, Geophysical Methods. With the help of a stratigraphic method, you can determine the sequence of layers in the normal location, i.e. The underlying layers will be more ancient.

Note 3.

The formation of rock formation determines relative geochronology, and their age in units determines already absolute Geochronology. Task geological time It is to determine the chronological sequence of geological events.

Geochronological table

To determine the age of rock and their research, scientists use various methods, and a special scale was compiled for this purpose. Geological time on this scale is divided into temporary segments to each of which corresponds to a certain stage of the formation of the earth's crust and the development of living organisms. The scale was named geochronological table in which the following units are allocated: eon, Era, period, era, century, time. For each geochronological unit, its deposit complex is characteristic, which is called Stratigraphic: eonothem, Group, System, Department, Tier, Zone. A group, for example, is a stratigraphic division, and the temporary geochronological division of it is relevant era. Based on this, there are two scales - stratigraphic and geochronological. The first scale is used when it comes to sedimentsBecause any geological events took place on Earth in any time on Earth. The second scale is needed to determine relative time. Since the adoption of the content of the scale changed and specified.

The largest stratigraphic divisions are currently eonothemes - archean, Proterozoic, Plyerozoic. In a geochronological scale, they correspond to the zones of various durations. By the time of existence on Earth stand out archean and Proterozoic Eonothemes, engulfed almost $ 80 $% of time. Puerozoic Eon.the time is significantly less than the previous EON and covers only $ 570 $ million. This ion is divided into three main groups - paleozoa, Mesoza, Cenozoa.

The name of the Eonothem and Groups have Greek origin:

• Archaeos means the oldest;
• Water - primary;
• Paleos - ancient;
• Mesos - medium;
• Kaynos - new.

From the word " zoikoc ", which means life, the word happened" zoya" Based on this, the era of life on the planet, for example, the Mesozoic era means the era of average life.

Era and periods

The history of land in a geochronological table is divided into five geological er: archean, Proterozoic, Paleozoic, Mesozoic, Cenozoic. In turn, the era are divided into Periods. They are much more - $ 12 $. The duration of periods is different from $ 20 $ - $ 100 $ million years. On your incompleteness indicates the last quaternary period of Cenozoic era, its duration is only $ 1.8 million years old.

Archean era. This time began after the formation of the earth's crust on the planet. On Earth, by this time there were mountains and processes of erosion and sedimentation. Archey lasted approximately $ 2 $ billion years. This era is the longest for the duration, during which volcanic activity has been widespread on Earth, the depth raising was widespread, the result of which was the formation of mountains. Most of the fossils under the action of high temperature, pressure, mass movement, was destroyed, but small data on the time was preserved. In the rocks of the Archean era, pure carbon is found in the scattered form. Scientists believe that these are altered the remains of animals and plants. If the amount of graphite reflects the number of live matter, it existed a lot in the archey.

Proterozoic era. The duration is the second era that covers $ 1 $ billion. Throughout the era, there was a deposition of a large amount of precipitation and one significant glaciation. Iceprokes spread from equator to $ 20 $ degree latitude. Fossils found in the breeds of this time are evidence of the existence of life and its evolutionary development. Sponges, the remains of jellyfish, mushrooms, algae, arthropods, and others were found in Proterezhoy's sediments.

Palaeozoic. This era stands out six Periods:

• Cambria;
• Ordovik,
• Silica;
• Devonian;
• Carbon or coal;
• Perm or Perm.

Paleozoic duration is $ 370 million years old. During this time, representatives of all types and classes of animals appeared. There were not only birds and mammals.

Mesozoic era. Era is divided by three Period:

• Triassic;

Era began about $ 230 million years ago and lasted $ 1,67 million years old. During the first two periods - triassia and Jurassic - Most of the mainland areas climbed above sea level. The climate of Triass is dry and warm, and in Yura he became still warmer, but was already wet. In the state Arizona there is a famous stone forest existing with triassoy Period. True, only trunks, logs and stumps remained from the once powerful trees. At the end of the Mesozoic era, or rather in the chalk period, the gradual offensive of the sea occurs on the mainland. The North American continent at the end of the chalk period experienced immersion and as a result of the water of the Gulf of Mexican bay with the waters of the Arctic pool. The mainland was divided into two parts. Completion of the Cretaceous Period is characterized by a large raising called name alpine Gorough formation. At this time, Rocky Mountains, Alps, Himalayas, Andes appeared. Intensive volcanic activity began in the west of North America.

Cenozoic Era. This is a new era that has not yet ended and continues at the present time.

The era was divided into three periods:

• Paleogen;
• Neogene;
• Quaternary.

Quaternary The period has a number of unique features. This is the time of the final formation of a modern face of the earth and the glacial periods. We became independent New Guinea and Australia, mixing closer to Asia. Antarctica remained in its place. Two America connected. Of the three periods of the era, the most interesting is quaternary Period or anthropogenic. It continues now, and was allocated at $ 1829 by the Belgian geologist J. Denuayee. Cooling change warming, but its most important feature is appearance of man.

Modern person lives in the Quaternary period of the Cenozoic era.

Causes of the selection of a quaternary period

Starting with oligocene, the climate on Earth began to stable, which was accompanied by an equally stable decrease in the sea level. Both of these processes were not strictly unidirectional - they were oscillatory, but the general trend was preserved. At the same time, the increments of sushi became increasingly modern, close to modern zonor-sectoral landscape-climatic belts were installed. The cooling was accompanied by an increase in the amplitude of the climate fluctuations, and these oscillations began to change markedly on the entire natural setting - during periods of cooling, there was a massive offensive of cold-pepperbing tundmont vegetation, the corresponding fauna was distributed, the configuration of natural zones changed sharply towards the reduction of low-seasual transition zones and the growth of high-seasual. During periods of warming, the blending flora and fauna almost disappeared and low-widespread transition zones were obtained. At the same time, with each new warming of relict tropical plants in moderate belts, it was becoming less and less.

All this led to the fact that for several millions of years, the physico-geographical setting on Earth changed dramatically and turned out to be incomparable with any of those existing previously. It took the allocation of the last stage of the development of the geographic shell into a special geological period. This happened in 1825, when approximately the last million years of the history of the Earth was combined into a special - quaternary period. It is sometimes called anthropogenic period or Pleistocene.

A special period in the history of the Earth has its own unique features that distinguish it from all other geological periods:

1. He is unusually short. Its duration is only 1.8 million years (in Russia - 1.65 million liters).

2. The sediments of the quaternary age are extremely young and therefore: a) they are widely preserved and taught the land with an almost solid cover; b) differ in the extreme genetic diversity, the variety of lithological composition and the facial variability; c) have almost exclusively continental genesis (except, of course, quaternary and modern deposits accumulating in the seas and oceans); d) have low power due to short-term formation.

3. Natural and biotic complexes are well preserved (and not just separate guidelines).

The main events of the Quaternary period are the following:

1. Consistent and multiple climate fluctuations that brought in the second half of the period to glaciation in high latitudes (which was not at least from carbon). Warm epochs are called thermochrones, cold - cryofers. These fluctuations and glaciation are fixed in thousands of outcrops, where special ice deposits are opened - currency loams (moraine) and others, as well as in the analyzes of the fauna and the flora of those times, as part of the oxygen isotopes and other diverse traces of past eras.

2. The appearance of a person. If the glaciations have already met on earth continents in the past, this event is a unique, which has no analogues in either the history of the Earth, nor in the history of other available studies of heavenly bodies. The emergence and development of a person led to the emergence of a fundamentally new overseas generality on Earth - humanity. It was humanity for the first time that the noospheres - the spheres of the mind, which alone consider the highest state of the earthly biosphere (according to V.I. Vernadsky), and others - the substance of the intangible case, which is not part of the geographic shell, but a perceived person and contributing to his geo-forming role (by E.Lerua And P.Tyar de Charden).

A few words must be said about the lower border of the Quaternary period and its periodization. Although the first signs of continental glaciation appeared only 780 thousand liters. N., the lower border of the Quaternary is carried out in the countries of Western Europe, according to 1.8 million years. It was approved in 1932 on the established signs of cooling of seawater in marine cuts of the south of Italy, at the base of the Calabrian tier. In 1948, this border was pronounced everywhere, except for the USSR. But in 1990 and in our country the border of the quaternary period was lowered before the turn of 1.65 million liters. n. And it began to be carried out at the lower border of the Abshero Barus (Calabrian Analogue). The time interval between the new and old borders of the Quaternary period, i.e. between 1.65 and 0.78 million liters. n. He was named with the Eopleestocene, and the former quaternary period is nele-love (although it is often called just Pleistocene) (see 7.1).

And the universe. For example, Kant's hypothesis - Laplas, O.Yu. Schmidt, George Buffon, Freda Hoyle, etc. But most scientists tend to believe that the Earth is about 5 billion years.

On the events of the geological past in their chronological sequence gives an idea of \u200b\u200ba single international geochronological scale. Its main divisions are the era: the Archean, Proterozoic, Paleozoic, Mesozoic. Cenozoic. The oldest geological time interval (Archey and Proterezhoy) is also called the Precarchbright. It covers a long time - almost 90% of the whole (the absolute age of the planet, according to modern ideas, is accepted equal to 4.7 billion years).

Inside the ER, smaller time segments are distinguished - periods (for example, Paleogenic, uncoole and quaternary in the Cenozoic era).

In the Archean Era (from Greek - initial, ancient) crystalline rocks (granites, gneisses, shale) were formed. In this era, there were powerful global processes. The study of this era allowed geologists to assume the presence of seas and living organisms in them.

The Proterozoic Era (Era of Early Life) is characterized by deposits of rocks in which the remains of living organisms are found. In this era on the surface of the Earth, the most sustainable areas were formed - platforms. Platforms - these ancient cores - became centers of formation.

Paleozoic era (the era of an ancient life) is distinguished by several stages of powerful mining ,. The Scandinavian Mountains, Urals, Tien Shan, Altai, Apalachi appeared in this era. At this time, animal organisms with a solid skeleton appeared. For the first time, vertebrates appeared: fish, amphibians, reptiles. On average, Paleozoic appeared ground vegetation. Tree ferns, plane and others. Served as material for the formation of coal deposits.

The Mesozoic Era (Era of Middle Life) is also characterized by intense folding. Mountains were formed in areas adjacent to. Among the animals were predicted with reptiles (dinosaurs, proteroauts, etc.), birds and mammals appeared for the first time. The vegetation consisted of ferns, coniferous, at the end of the era appeared coated plants.

In the Cenozoic Era (era of a new life) there is a modern distribution of continents and oceans, intensive plotting movements occur. Mountain chains are formed on the shores of the Pacific Ocean, in the south of Europe and Asia (, Himalayas, the coastal ridges of Cordiller, etc.). At the beginning of the Cenozoic era, the climate was significantly warmer than modern. However, the increase in land area due to the raising of the mainland led to cooling. Extensive iceclocks appeared in the north and. This led to significant changes in plant and animal world. Many animals have died out. There were plants and animals close to modern. At the end of this era, a man appeared and began to intensively settle the land.

The first three billion years of the development of the Earth led to the formation of land. According to the ideas of scientists, at the beginning, there was one mainland, which was subsequently split into two, and then there was still a division and as a result, five continents were formed to today.

The last billion years of the history of the Earth is associated with the formation of folded areas. At the same time, several tectonic cycles (epochs) are distinguished in the geological history of the last billion: Baikal (End of Proterezhoy), Caledonian (Early Paleozoa), Hercinsky (late Paleozoa), Mesozoic (Mesozoic), Cenozoic or Alpine cycle (from 100 million years and to of the present).
As a result of all the above processes, the Earth acquired a contemporary structure.