Geological periods in chronological order. Geological history of the Earth

And the Universe. For example, the Kant-Laplace hypothesis, O.Yu. Schmidt, Georges Buffon, Fred Hoyle and others. But most scientists are inclined to believe that the Earth is about 5 billion years old.

About the events of the geological past in their chronological sequence The unified international geochronological scale gives an idea. Its main divisions are the eras: Archean, Proterozoic, Paleozoic, Mesozoic. Cenozoic. The oldest interval of geological time (Archean and Proterozoic) is also called Precambrian. It covers long period- almost 90% of the total (the absolute age of the planet, according to modern concepts, is taken to be 4.7 billion years).

Within eras, smaller time periods are distinguished - periods (for example, Paleogene, Neogene and Quaternary in the Cenozoic era).

In the Archean era (from Greek - primordial, ancient), crystalline rocks (granites, gneisses, schists) were formed. During this era, powerful mountain-building processes did not take place. The study of this era allowed geologists to assume the presence of seas and living organisms in them.

Proterozoic era(early life era) is characterized by rock deposits in which the remains of living organisms are found. During this era, the most stable areas - platforms - formed on the surface of the Earth. The platforms - these ancient cores - became centers of formation.

Paleozoic era (era ancient life) is distinguished by several stages of powerful mountain building, . During this era, the Scandinavian mountains, the Urals, Tien Shan, Altai, and Appalachians arose. At this time, animal organisms with a hard skeleton appeared. Vertebrates appeared for the first time: fish, amphibians, reptiles. In the Middle Paleozoic, land vegetation appeared. Tree ferns, moss ferns, etc. served as material for the formation of coal deposits.

The Mesozoic era (the era of middle life) is also characterized by intense folding. Mountains formed in areas adjacent to. Reptiles (dinosaurs, proterosaurs, etc.) dominated among animals; birds and mammals appeared for the first time. The vegetation consisted of ferns, conifers, and angiosperms appeared at the end of the era.

During the Cenozoic era (the era of new life), the modern distribution of continents and oceans took shape, and intense mountain-building movements occurred. Mountain ranges are formed on the shores of the Pacific Ocean, in southern Europe and Asia (the Himalayas, the Cordillera Coastal Ranges, etc.). At the beginning of the Cenozoic era, the climate was much warmer than today. However, the increase in land area due to the rise of continents led to cooling. Extensive ice sheets in the north and . This led to significant changes in the flora and fauna. Many animals became extinct. Plants and animals close to modern ones appeared. At the end of this era, man appeared and began to intensively populate the land.

The first three billion years of Earth's development led to the formation of land. According to scientists, at first there was one continent on Earth, which subsequently split into two, and then another division occurred, and as a result, five continents were formed today.

The last billion years of Earth's history are associated with the formation of folded regions. At the same time, in the geological history of the last billion years, several tectonic cycles (epochs) are distinguished: Baikal (end of the Proterozoic), Caledonian (early Paleozoic), Hercynian (late Paleozoic), Mesozoic (Mesozoic), Cenozoic or Alpine cycle (from 100 million years to present tense).
As a result of all the above processes, the Earth acquired its modern structure.

The emergence of the Earth and the early stages of its formation

One of the important tasks modern natural science in the field of geosciences is the restoration of the history of its development. According to modern cosmogonic concepts, the Earth was formed from gas and dust matter scattered in the protosolar system. One of the most likely options for the emergence of the Earth is as follows. First, the Sun and a flattened rotating circumsolar nebula were formed from an interstellar gas and dust cloud under the influence, for example, of the explosion of a nearby supernova. Next, the evolution of the Sun and the circumsolar nebula occurred with the transfer of angular momentum from the Sun to the planets by electromagnetic or turbulent-convective methods. Subsequently, the “dusty plasma” condensed into rings around the Sun, and the material of the rings formed the so-called planetesimals, which condensed into planets. After this, a similar process was repeated around the planets, leading 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 differentiation of the Earth's substance under the influence of its gravitational field and radioactive heating, shells of the Earth, different in chemical composition, state of aggregation and physical properties, emerged and developed - the Earth's geosphere. The heavier material formed a core, probably composed of iron mixed with nickel and sulfur. Some lighter elements remained in the mantle. According to one hypothesis, the mantle is composed of simple oxides of aluminum, iron, titanium, silicon, etc. The composition of the earth's crust has already been discussed in some detail in § 8.2. It is composed of lighter silicates. Even lighter gases and moisture formed the primary atmosphere.

As already mentioned, it is assumed that the Earth was born from a cluster of cold solid particles that fell out of a gas-dust nebula and stuck together under the influence of mutual attraction. As the planet grew, it heated up due to the collision of these particles, which reached several hundred kilometers, like modern asteroids, and the release of heat not only by the naturally radioactive elements now known to us in the crust, but also by more than 10 radioactive isotopes AI, Be, that have become extinct since then. Cl, etc. As a result, complete (in the core) or partial (in the mantle) melting of the substance could occur. In the initial period of its existence, up to approximately 3.8 billion years, the Earth and other terrestrial planets, as well as the Moon, were subjected to intense bombardment by small and large meteorites. The consequence of this bombardment and the earlier collision of planetesimals could be the release of volatiles and the beginning of the formation of a secondary atmosphere, since the primary one, consisting of gases captured during the formation of the Earth, most likely quickly dissipated into outer space. Somewhat later, the hydrosphere began to form. The atmosphere and hydrosphere thus formed were replenished during the process of degassing of the mantle during volcanic activity.

The fall of large meteorites created extensive and deep craters, similar to those currently observed on the Moon, Mars, and Mercury, where their traces have not been erased by subsequent changes. Cratering could provoke outpourings of magma with the formation of basalt fields similar to those covering the lunar “seas”. This is probably how the primary crust of the Earth was formed, which, however, was not preserved on its modern surface, with the exception of relatively small fragments in the “younger” continental-type crust.

This crust, which already contains granites and gneisses, although with a lower content of silica and potassium than in “normal” granites, appeared at the turn of about 3.8 billion years and is known to us from outcrops within the crystalline shields of almost all continents. The method of formation of the oldest continental crust is still largely unclear. In the composition of this crust, which is everywhere metamorphosed under conditions of high temperatures and pressures, rocks are found whose textural features indicate accumulation in an aquatic environment, i.e. in this distant era the hydrosphere already existed. The emergence of the first crust, similar to the modern one, required the supply of large quantities of silica, aluminum, and alkalis from the mantle, while now mantle magmatism creates a very limited volume of rocks enriched in these elements. It is believed that 3.5 billion years ago, gray gneiss crust, named after the predominant type of rocks composing it, was widespread across the area of ​​modern continents. In our country, for example, it is known on the Kola Peninsula and in Siberia, in particular in the river basin. Aldan.

Principles of periodization of the geological history of the Earth

Subsequent events in geological time are often determined according to relative geochronology, categories “ancient”, “younger”. For example, some era is older than some other. Individual segments of geological history are called (in order of decreasing duration) zones, eras, periods, epochs, centuries. Their identification is based on the fact that geological events are imprinted in rocks, and sedimentary and volcanogenic rocks are located in layers in the earth's crust. In 1669, N. Stenoi established the law of bedding sequence, according to which the underlying layers of sedimentary rocks are older than the overlying ones, i.e. formed before them. Thanks to this, it became possible to determine the relative sequence of formation of layers, and therefore the geological events associated with them.

The main one in relative geochronology is the biostratigraphic, or paleontological, method of establishing the relative age and sequence of occurrence of rocks. This method was proposed by W. Smith at the beginning of the 19th century, and then developed by J. Cuvier and A. Brongniard. The fact is that in most sedimentary rocks you can find the remains of animal or plant organisms. J.B. Lamarck and C. Darwin established that animals and plant organisms Over the course of geological history, they gradually improved in the struggle for existence, adapting to changing living conditions. Some animal and plant organisms died out at certain stages of the Earth's development, and were replaced by others, more advanced ones. Thus, from the remains of previously living, more primitive ancestors found in some layer, one can judge the relatively more ancient age of this layer.

Another method of geochronological division of rocks, especially important for the division of igneous formations of the ocean floor, is based on the property of magnetic susceptibility of rocks and minerals formed in the Earth's magnetic field. With a change in rock orientation relative to magnetic field or the field itself, part of the “innate” magnetization is preserved, and the change in polarity is reflected in a change in the orientation of the remanent magnetization of the rocks. Currently, a scale of change of such eras has been established.

Absolute geochronology - the study 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, since the age of geological events is determined by their age. The main method here is to analyze the ratio of radioactive substances and their decay products in rocks formed in different eras.

The oldest rocks are currently established in Western Greenland (3.8 billion years old). The longest age (4.1 - 4.2 billion years) was obtained from zircons from Western Australia, but the zircon here occurs in a redeposited state in Mesozoic sandstones. Taking into account the ideas about the simultaneous formation of all planets of the Solar system and the Moon and the age of the most ancient meteorites (4.5-4.6 billion years) and ancient lunar rocks (4.0-4.5 billion years), the age of the Earth is taken to be 4.6 billion years

In 1881, at the II International Geological Congress in Bologna (Italy), the main divisions of combined stratigraphic (for separating layered sedimentary rocks) and geochronological scales were approved. According to this scale, the history of the Earth was divided into four eras in accordance with the stages of development organic world: 1) Archean, or Archeozoic - the era of ancient life; 2) Paleozoic - the era of ancient life; 3) Mesozoic - the era of middle life; 4) Cenozoic - era of new life. In 1887 from the composition Archean era identified the Proterozoic - the era of primary life. Later the scale was improved. One of the options for the modern geochronological scale is presented in Table. 8.1. The Archean era is divided into two parts: early (older than 3500 million years) and late Archean; Proterozoic - also into two: early and late Proterozoic; in the latter, the Riphean (the name comes from the ancient name of the Ural Mountains) and Vendian periods are distinguished. The Phanerozoic zone is divided into Paleozoic, Mesozoic and Cenozoic eras 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 an inert substrate on which the diversity of the surrounding nature developed.

INapxee The still quite thin and plastic crust, under the influence of stretching, experienced numerous discontinuities through which basaltic magma again rushed to the surface, filling troughs hundreds of kilometers long and many tens of kilometers wide, known as greenstone belts (they owe this name to the predominant greenschist low-temperature metamorphism of basaltic rocks). breeds). Along with basalts, among the lavas of the lower, most powerful part of the section of these belts, there are high-magnesium lavas, indicating a very high degree of partial melting of mantle matter, which indicates a high heat flow, much higher than today. The development of greenstone belts consisted of a change in the type of volcanism in the direction of an increase in the content of silicon dioxide (SiO 2), in compression deformations and metamorphism of sedimentary-volcanogenic fulfillment, and, finally, in the accumulation of clastic sediments, indicating the formation of mountainous terrain.

After the change of several generations of greenstone belts, the Archean stage of the evolution of the earth's crust ended 3.0 -2.5 billion years ago with the massive formation of normal granites with a predominance of K 2 O over Na 2 O. Granitization, as well as regional metamorphism, which in some places reached the highest level, led to the formation of mature continental crust over most of the area of ​​modern continents. However, this crust also turned out to be insufficiently stable: at the beginning of the Proterozoic era it experienced fragmentation. At this time, a planetary network of faults and cracks arose, filled with dikes (plate-shaped geological bodies). One of them, the Great Dyke in Zimbabwe, is more than 500 km long and up to 10 km wide. In addition, rifting appeared for the first time, giving rise to zones of subsidence, powerful sedimentation and volcanism. Their evolution led to the creation at the end early Proterozoic(2.0-1.7 billion years ago) folded systems that again welded together fragments of the Archean continental crust, which was facilitated by a new era of powerful granite formation.

As a result, by the end of the Early Proterozoic (at the turn of 1.7 billion years ago), mature continental crust already existed on 60-80% of the area of ​​its modern distribution. Moreover, some scientists believe that at this turn the entire continental crust constituted a single massif - the supercontinent Megagaea (big earth), which on the other side of the globe was opposed by an ocean - the predecessor of the modern Pacific Ocean - Megathalassa (big sea). This ocean was less deep than modern oceans, because the growth of the volume of the hydrosphere due to degassing of the mantle in the process of volcanic activity continues throughout the subsequent history of the Earth, although more slowly. It is possible that the prototype of Megathalassa appeared even earlier, at the end of the Archean.

In the Catarchean and early Archean, the first traces of life appeared - bacteria and algae, and in the late Archean, algal calcareous structures - stromatolites - spread. In the Late Archean, a radical change in the composition of the atmosphere began, and in the Early Proterozoic ended: under the influence of plant activity, free oxygen appeared in it, while the Catarchean and Early Archean atmosphere consisted of water vapor, CO 2, CO, CH 4, N, NH 3 and H 2 S with an admixture of HC1, HF and inert gases.

In the Late Proterozoic(1.7-0.6 billion years ago) Megagaia began to gradually split, and this process sharply intensified at the end of the Proterozoic. Its traces are extended continental rift systems buried at the base of the sedimentary cover of ancient platforms. Its most important result was the formation of vast intercontinental mobile belts - the North Atlantic, Mediterranean, Ural-Okhotsk, which divided the continents of North America, Eastern Europe, East Asia and the largest fragment of Megagaea - the southern supercontinent Gondwana. The central parts of these belts developed on the newly formed ocean crust during rifting, i.e. the belts represented ocean basins. Their depth gradually increased as the hydrosphere grew. At the same time, mobile belts developed along the periphery of the Pacific Ocean, the depth of which also increased. Climatic conditions became more contrasting, as evidenced by the appearance, especially at the end of the Proterozoic, of glacial deposits (tillites, ancient moraines and fluvio-glacial sediments).

Paleozoic stage The evolution of the earth's crust was characterized by the intensive development of mobile belts - intercontinental and continental margins (the latter on the periphery of the Pacific Ocean). These belts were divided into marginal seas and island arcs, their sedimentary-volcanogenic strata experienced complex fold-thrust and then normal fault deformations, granites were intruded into them and folded mountain systems were formed on this basis. This process was uneven. It distinguishes a number of intense tectonic epochs and granite magmatism: Baikal - at the very end of the Proterozoic, Salair (from the Salair ridge to Central Siberia) - at the end of the Cambrian, Takovian (from the Takovsky mountains in the eastern USA) - at the end of the Ordovician, Caledonian (from the ancient Roman name for Scotland) - at the end of the Silurian, Acadian (Acadia is the ancient name of the northeastern states of the USA) - in the middle of the Devonian, Sudeten - at the end of the Early Carboniferous, Saale (from the Saale River in Germany) - in the middle of the Early Permian. The first three tectonic eras of the Paleozoic are often combined into the Caledonian era of tectogenesis, the last three - into the Hercynian or Variscan. In each of the listed tectonic epochs, certain parts of the mobile belts turned into folded mountain structures, and after destruction (denudation) they became part of the foundation of young platforms. But some of them partially experienced activation in subsequent eras of mountain building.

By the end of the Paleozoic, the intercontinental mobile belts were completely closed and filled with folded systems. As a result of the withering away of the North Atlantic belt, the North American continent closed with the East European continent, and the latter (after the completion of the development of the Ural-Okhotsk belt) with the Siberian continent, and the Siberian continent with the Chinese-Korean one. As a result, the supercontinent Laurasia was formed, and the death of the western part of the Mediterranean belt led to its unification with the southern supercontinent - Gondwana - into one continental block - Pangea. At the end of the Paleozoic - beginning of the Mesozoic, the eastern part of the Mediterranean belt 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 topography of the Earth, the development of life continued. The first animals appeared in the late Proterozoic, and at the very dawn of the Phanerozoic, almost all types of invertebrates existed, but they were still devoid of shells or shells, which have been known since the Cambrian. In the Silurian (or already in the Ordovician), vegetation began to emerge on land, and at the end of the Devonian, forests existed, which became most widespread in the Carboniferous period. Fish appeared in the Silurian, amphibians - in the Carboniferous.

Mesozoic and Cenozoic eras - 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 the Triassic, Pangea still existed, but already in the early Jurassic period it again split into Laurasia and Gondwana due to the emergence of the latitudinal Tethys Ocean, stretching from Central America to Indochina and Indonesia, and in the west and east it connected with the Pacific Ocean (Fig. 8.6); this ocean included the Central Atlantic. From here, at the end of the Jurassic, the process of continental spreading spread to the north, creating during the Cretaceous and early Paleogene the North Atlantic, and starting from the Paleogene - the Eurasian basin of the Arctic Ocean (the Amerasian basin arose earlier as part of the Pacific Ocean). As a result, North America separated from Eurasia. In the Late Jurassic, the formation of the Indian Ocean began, and from the beginning of the Cretaceous, the South Atlantic began to open from the south. This marked the beginning of the collapse of Gondwana, which existed as a single entity throughout the Paleozoic. At the end of the Cretaceous, the North Atlantic joined the South Atlantic, separating Africa from South America. At the same time, Australia separated from Antarctica, and at the end of the Paleogene the latter separated from South America.

Thus, by the end of the Paleogene, all modern oceans took shape, all modern continents became isolated, and the appearance of the Earth acquired a form that was basically close to the present one. However, there were no modern mountain systems yet.

Intense mountain building began in the late Paleogene (40 million years ago), culminating in the last 5 million years. This stage of the formation of young fold-cover mountain structures and the formation of revived arched block mountains is identified as neotectonic. In fact, the neotectonic stage is a substage of the Mesozoic-Cenozoic stage of the Earth's development, since it was at this stage that the main features of the modern relief of the Earth took shape, starting with 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 the era of reptiles, mammals became dominant in the Cenozoic, and humans appeared in the late Pliocene. At the end of the Early Cretaceous, angiosperms appeared and the land acquired grass cover. At the end of the Neogene and Anthropocene, the high latitudes of both hemispheres were covered by powerful continental glaciation, relics of which are the ice caps of Antarctica and Greenland. This was the third major glaciation in the Phanerozoic: the first took place in the Late Ordovician, the second at the end of the Carboniferous - beginning of the Permian; both of them were distributed within Gondwana.

QUESTIONS FOR SELF-CONTROL

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

What's it like internal structure Earth? On what basis is a conclusion made about its structure?

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

What is the chemical and mineralogical composition of the Earth? On what basis is the conclusion made about chemical composition the entire Earth and the earth's crust?

What are the main types of the earth's crust currently distinguished?

What is the hydrosphere? What is the water cycle in nature? What are the main processes occurring in the hydrosphere and its elements?

What is atmosphere? What is its structure? What processes occur within its boundaries? What is weather and climate?

Define endogenous processes. What endogenous processes do you know? Briefly describe them.

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

10. Define 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 of V. Davis and V. Penk?

What are modern ideas about the origin of the Earth? How did its early formation as a planet occur?

What is the basis for periodization of the geological history of the Earth?

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

LITERATURE

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Dynamic geomorphology / Ed. G.S. Ananyeva, Yu.G. Simonova, A.I. Spiridonova. M., 1992.

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Billions of years ago, our Earth was a bare, lifeless planet. And then life appeared on its surface - those first, most primitive forms of living beings, the development of which led to the endless diversity of the nature around us. How did this development take place? How did animals and plants appear on Earth, how did they change? This book will answer some of these questions. Its author, the outstanding Soviet scientist Academician V.L. Komarov, described in it the history of the plant world of the Earth - from the simplest single-celled bacteria to modern highly developed flowering plants. The author draws this long path of development in close connection with the general history of the Earth, with its changes natural conditions, relief, climate. The book is written popularly, is easy to read and will be of great benefit to the widest range of readers who have basic knowledge of the field of biology in the scope of a school course.

Until now, only geological and climatic forces were at work in nature. As we have seen, they have always had a strong influence on the vegetation and contributed to its greater and greater diversity. Now a completely new factor has appeared: man.

Originating in the Tertiary period, according to various estimates, 600,000 - 1,000,000 years before our time, in ape-like forms, it met the Ice Age still unarmed. But in many places it was impossible to escape from the glacier; the cold drove man into the caves, which became his first home, and forced him to invent devices for maintaining fire. From this moment, man becomes an industrial being and, increasingly intensifying his activity, begins to influence nature more powerfully than any other human being. Living being. He clears forests, raises virgin soil, breaks through canals, blows up and digs up entire mountains, and generally changes the face of the Earth at his own discretion.

In relation to vegetation, man destroys forest flora, destroys steppe plants and many others and creates in their place his own special world, a world of cultivated plants, which would never have existed if not for man. The contemporary period of development of earthly vegetation is precisely characterized by the replacement by man of the flora inherited from previous times by cultivated vegetation.

We have seen that the conditions of plant life on Earth first put forward, as the pioneers of the primary settlement of the earth's crust, a group of bacteria known under the general name chemotrophic, i.e., those whose nutrition is limited to a small number of clearly defined, chemical reactions and does not need previously educated organic matter.

The age of bacteria was subsequently replaced by the age of algae, which in the waters of the ancient oceans reached a significant variety of shapes and colors.

The age of algae gave way on the primary continents to the age of psilophytes, which gave rise to vegetation reminiscent in its general appearance and the size of modern thickets of large mosses.

The age of psilophytes gave way to the age of fern-like plants, which have already formed extensive forests on marshy soils. This vegetation contributed greatly to the fact that both the composition of the air and the accumulation of mass of nutrients made possible occurrence the first land vertebrates. At the same time, the main masses of coal accumulated.

The age of ferns gave way to the age of cone-bearing plants. For the first time, the surface of the continents acquired a modern appearance in some places and the possibility of the existence of higher animals became even closer.

The age of cone-bearing plants was gradually replaced by the age of flowering plants, when, one after another, all the plants that exist today were formed.

It must be said that the onset of a new century or period never completely destroyed the previous one. vegetable world. Always a part of the past population of the Earth was preserved and continued to exist along with the new world. Thus, bacteria not only did not disappear with the appearance of higher vegetation, but also in the soil and in organic matter, so generously created higher plants, found new sources of livelihood for themselves. Algae, once developed, continue to grow and improve along with higher plants. Moreover, they are not competitors to them, since some inhabit coastal sea areas, while others mainly live on land.

Finally, the coniferous forests of our time continue to exist along with deciduous ones, and their shade provides shelter for fern-like plants, since this legacy of the foggy and humid Carboniferous period is afraid of open habitats where it is harmed Sun rays, and looks for shadows.

Thus the history of the earth's crust led to the creation of a rich and varied plant world, beginning its work from the materials provided by the inorganic world and ending with the creation of what surrounds us and provides us with everything we need for life.

“Zoology and botany remain still fact-gathering sciences until paleontology - Cuvier - joins in, and soon afterwards the discovery of the cell and the development of organic chemistry. Thanks to this, comparative morphology and comparative physiology became possible, and since then both have become genuine sciences."

F. Engels

Hello! In this article I want to tell you about the geochronological column. This is a column of periods of the Earth's development. And also in more detail about each era, thanks to which you can paint a picture of the formation of the Earth throughout its history. What types of life appeared first, how they changed, and how much it took.

Geological history The earth is divided into large intervals - eras, eras are divided into periods, periods are divided into epochs. This division was associated with events that took place on. Change abiotic environment influenced the evolution of the organic world on Earth.

Geological eras of the Earth, or geochronological scale:

And now about everything in more detail:

Designations:
Eras;
Periods;
Epochs.

1. Catarchaean era (from the creation of the Earth, about 5 billion years ago, to the origin of life);

2. Archean era , the most ancient era(3.5 billion – 1.9 billion years ago);

3. Proterozoic era (1.9 billion – 570 million years ago);

The Archean and Proterozoic are still combined into the Precambrian. The Precambrian covers the largest portion of geological time. Areas of land and sea were formed, and active volcanic activity occurred. Shields of all continents were formed from Precambrian rocks. Traces of life are usually rare.

4. Palaeozoic (570 million - 225 million years ago) with such periods :

Cambrian period(from the Latin name for Wales)(570 million – 480 million years ago);

The transition to the Cambrian was marked by the unexpected appearance huge amount fossils. This is a sign of the beginning of the Paleozoic era. Marine flora and fauna flourished in numerous shallow seas. Trilobites were especially widespread.

Ordovician period(from the British Ordovician tribe)(480 million – 420 million years ago);

Much of the Earth was soft, and most of the surface was still covered by seas. The accumulation of sedimentary rocks continued, and mountain building occurred. There were reef-formers. There is an abundance of corals, sponges and mollusks.

Silurian (from the British Silure tribe)(420 million – 400 million years ago);

Dramatic events in the history of the Earth began with the development of jawless fish-like fish (the first vertebrates), which appeared in the Ordovician. Another significant event was the appearance of the first land animals in the Late Silurian.

Devonian (from Devonshire in England)(400 million – 320 million years ago);

In the Early Devonian, mountain-building movements reached their peak, but basically it was a period of spasmodic development. The first seed plants settled on land. A large variety and number of fish-like species were noted, and the first terrestrial animals developed. animals- amphibians.

Carboniferous or Carboniferous period (from the abundance of coal in the seams) (320 million – 270 million years ago);

Mountain building, folding, and erosion continued. IN North America and swampy forests and river deltas were flooded, and large coal deposits were formed. The southern continents were covered by glaciation. Insects spread rapidly, and the first reptiles appeared.

Permian period (from the Russian city of Perm)(270 million – 225 million years ago);

On a large part of Pangea - the supercontinent that united everything - conditions prevailed. Reptiles spread widely and modern insects evolved. New terrestrial flora developed, including conifers. Several marine species have disappeared.

5. Mesozoic era (225 million - 70 million years ago) with such periods:

Triassic (from the tripartite division of the period proposed in Germany)(225 million – 185 million years ago);

With the onset of the Mesozoic era, Pangea began to disintegrate. On land, the dominance of conifers was established. Diversity among reptiles was noted, with the first dinosaurs and giant marine reptiles appearing. Primitive mammals evolved.

Jurassic period(from mountains in Europe)(185 million – 140 million years ago);

Significant volcanic activity was associated with the formation Atlantic Ocean. Dinosaurs dominated on land, flying reptiles and primitive birds conquered the air ocean. There are traces of the first flowering plants.

Cretaceous period (from the word "chalk")(140 million – 70 million years ago);

During the maximum expansion of the seas, chalk was deposited, especially in Britain. The dominance of dinosaurs continued until the extinction of them and other species at the end of the period.

6. Cenozoic era (70 million years ago - up to our time) with such periods And epochs:

Paleogene period (70 million – 25 million years ago);

— Paleocene epoch ("the oldest part of the new epoch")(70 million – 54 million years ago);
— Eocene Epoch ("dawn of a new era")(54 million – 38 million years ago);
— Oligocene Epoch ("not very new")(38 million – 25 million years ago);

Neogene period (25 million - 1 million years ago);

— Miocene Epoch ("relatively new")(25 million – 8 million years ago);
— Pliocene Epoch ("very recent")(8 million – 1 million years ago);

The Paleocene and Neogene periods are still combined into the Tertiary period. With the onset of the Cenozoic era (new life), mammals began to spread spasmodically. Many large species evolved, although many became extinct. The number of flowering plants has increased sharply plants. With the cooling of the climate there appeared herbaceous plants. There was a significant uplift of the land.

Quaternary period (1 million – our time);

— Pleistocene epoch (“most recent”)(1 million – 20 thousand years ago);

— Holocene era(“a completely new era”) (20 thousand years ago – our time).

This is the last geological period that includes the present time. Four major glaciations alternated with warming periods. The number of mammals has increased; they have adapted to . The formation of man - the future ruler of the Earth - took place.

There are also other ways of dividing eras, epochs, periods, eons are added to them, and some epochs are still divided, like on this table, for example.

But this table is more complex, the confusing dating of some eras is purely chronological, not based on stratigraphy. Stratigraphy is the science of determining the relative geological age of sedimentary rocks, the division of rock strata, and the correlation of various geological formations.

This division, of course, is relative, since there was no sharp distinction from today to tomorrow in these divisions.

But still, at the turn of neighboring eras and periods, significant geological transformations predominantly took place: processes of mountain formation, redistribution of seas, changing of the climate etc.

Each subsection was, of course, characterized by its unique flora and fauna.

, And You can read it in the same section.

Thus, these are the main eras of the Earth on which all scientists rely 🙂

The history of planet Earth already goes back approximately 7 billion years. During this time our common Home has undergone significant changes, which was a consequence of changing periods. in chronological order they reveal the entire history of the planet from its very appearance to the present day.

Geological chronology

The history of the Earth, presented in the form of eons, groups, periods and eras, is a certain grouped chronology. At the first international congresses of geology, a special chronological scale was developed, which represented the periodization of the Earth. Subsequently, this scale was replenished new information and changed, as a result, now it reflects all geological periods in chronological order.

The largest divisions on this scale are eonothems, eras and periods.

Formation of the Earth

The geological periods of the Earth in chronological order begin their history precisely with the formation of the planet. Scientists have concluded that the Earth was formed approximately 4.5 billion years ago. The process of its formation itself was very long and may have begun 7 billion years ago from small cosmic particles. Over time, the gravitational force grew, and along with it, the speed of the bodies falling onto the forming planet increased. Kinetic energy was transformed into heat, resulting in a gradual warming of the Earth.

The Earth's core, according to scientists, was formed over several hundred million years, after which the gradual cooling of the planet began. Currently, the molten core contains 30% of the Earth's mass. The development of other shells of the planet, according to scientists, has not yet been completed.

Precambrian eon

In the geochronology of the Earth, the first eon is called the Precambrian. It covers the time 4.5 billion - 600 million years ago. That is lion's share The history of the planet is covered first. However, this eon is divided into three more - Katarchean, Archean, Proterozoic. Moreover, often the first of them stands out as an independent eon.

At this time, the formation of land and water occurred. All this happened during active volcanic activity for almost the entire eon. The shields of all continents were formed in the Precambrian, but traces of life are very rare.

Catarchaean Eon

The beginning of the history of the Earth - half a billion years of its existence in science is called catarchaeum. The upper limit of this eon is located at around 4 billion years ago.

Popular literature portrays catarchaea as a time of active volcanic and geothermal changes on the Earth's surface. However, in reality this is not true.

The Catarchaean Eon is a time when volcanic activity did not manifest itself, and the surface of the Earth was a cold, inhospitable desert. Although earthquakes occurred quite often, which smoothed the landscape. The surface looked like dark gray primordial material covered with a layer of regolith. A day at that time was only 6 hours long.

Archean eon

The second main eon of four in the history of the Earth lasted about 1.5 billion years - 4-2.5 billion years ago. At that time, the Earth did not yet have an atmosphere, therefore there was no life yet, however, during this eon, bacteria appeared; due to the lack of oxygen, they were anaerobic. As a result of their activities, today we have deposits of natural resources such as iron, graphite, sulfur and nickel. The history of the term “archaea” dates back to 1872, when it was proposed by the famous American scientist J. Dan. The Archean eon, unlike the previous one, is characterized by high volcanic activity and erosion.

Proterozoic eon

If we consider geological periods in chronological order, the next billion years were occupied by the Proterozoic. This period is also characterized by high volcanic activity and sedimentation, and erosion continues over vast areas.

The formation of the so-called occurs. mountains Currently they are small hills on the plains. The rocks of this eon are very rich in mica, non-ferrous metal ores and iron.

It should be noted that in the Proterozoic period the first living beings appeared - simple microorganisms, algae and fungi. And by the end of the eon, worms, marine invertebrates, and mollusks appear.

Phanerozoic eon

All geological periods in chronological order can be divided into two types - obvious and hidden. Phanerozoic belongs to the obvious ones. At this time it appears a large number of living organisms with mineral skeletons. The era preceding the Phanerozoic was called hidden because practically no traces of it were found due to the lack of mineral skeletons.

The last about 600 million years of the history of our planet are called the Phanerozoic eon. The most significant events of this eon are the Cambrian explosion, which occurred approximately 540 million years ago, and the five largest extinctions in the history of the planet.

Eras of the Precambrian Eon

During the Katarchean and Archean there were no generally recognized eras and periods, so we will skip their consideration.

The Proterozoic consists of three large eras:

Paleoproterozoic- i.e. ancient, including the Siderian, Rhiasian period, Orosirium and Staterium. By the end of this era, oxygen concentrations in the atmosphere had reached modern levels.

Mesoproterozoic- average. Consists of three periods - potassium, ectasia and sthenia. During this era, algae and bacteria reached their greatest prosperity.

Neoproterozoic- new, consisting of Thonium, Cryogenium and Ediacaran. At this time, the formation of the first supercontinent, Rodinia, occurred, but then the plates diverged again. The coldest ice age occurred during an era called the Mesoproterozoic, during which the most of planets.

Eras of the Phanerozoic eon

This eon consists of three large eras, sharply different from each other:

Paleozoic, or the era of ancient life. It began approximately 600 million years ago and ended 230 million years ago. The Paleozoic consists of 7 periods:

1. Cambrian (formed on Earth temperate climate, the landscape is low-lying, during this period the birth of all modern types animals).
2. Ordovician (the climate throughout the planet is quite warm, even in Antarctica, while the land subsides significantly. The first fish appear).
3. Silurian period (large inland seas are formed, while the lowlands become drier due to the rise of land. The development of fish continues. The Silurian period is marked by the appearance of the first insects).
4. Devonian (appearance of the first amphibians and forests).
5. Lower Carboniferous (dominance of pteridophytes, distribution of sharks).
6. Upper and Middle Carboniferous (appearance of the first reptiles).
7. Perm (most ancient animals die out).

Mesozoic, or the time of reptiles. Geological history consists of three periods:

1. Triassic (seed ferns die out, gymnosperms dominate, the first dinosaurs and mammals appear).
2. Jurassic (part of Europe and western America covered with shallow seas, appearance of the first toothed birds).
3. Cretaceous (the appearance of maple and oak forests, the highest development and extinction of dinosaurs and toothed birds).

Cenozoic, or the time of mammals. Consists of two periods:

1. Tertiary. At the beginning of the period, predators and ungulates reach their dawn, the climate is warm. There is a maximum expansion of forests, the oldest mammals are dying out. Approximately 25 million years ago, humans appeared and in the Pliocene era.
2. Quaternary. Pleistocene - large mammals die out, human society emerges, 4 ice ages occur, many plant species become extinct. Modern era- the last ice age ends, the climate gradually takes on its current form. The primacy of man on the entire planet.

The geological history of our planet has a long and contradictory development. In this process, there were several extinctions of living organisms, ice ages were repeated, periods of high volcanic activity were observed, and there were eras of dominance of different organisms: from bacteria to humans. The history of the Earth began approximately 7 billion years ago, it was formed about 4.5 billion years ago, and just less than a million years ago, man ceased to have competitors in all living nature.