Geological periods in chronological order. The main stages in the development of life on earth

Geological time and methods of its determination

In the study of the Earth as a unique space object, the idea of its evolution occupies a central place, therefore, an important quantitative-evolutionary parameter is geological time... The study of this time is engaged in a special science, which received the name Geochronology- geological chronology. Geochronology may be absolute and relative.

Remark 1

Absolute geochronology deals with determining the absolute age of rocks, which is expressed in units of time and, as a rule, in millions of years.

The determination of this age is based on the decay rate of isotopes of radioactive elements. This speed is constant and does not depend on the intensity of physical and chemical processes. Age determination is based on methods of nuclear physics. Minerals containing radioactive elements form a closed system during the formation of crystal lattices. In this system, the accumulation of radioactive decay products occurs. As a result, the age of the mineral can be determined if the rate of this process is known. The half-life of radium, for example, is $ 1590 years, and the complete decay of the element will occur in $ 10 times the half-life. Nuclear geochronology has its leading methods - lead, potassium-argon, rubidium-strontium and radiocarbon.

Nuclear geochronological methods have made it possible to determine the age of the planet, as well as the duration of eras and periods. Radiological time measurement proposed P. Curie and E. Rutherford at the beginning of the $ XX century.

Relative geochronology operates with such concepts as "early age, middle age, late". There are several developed methods for determining the relative age of rocks. They come together in two groups - paleontological and non-paleontological.

The first play a major role due to their versatility and widespread use. The exception is the absence of organic remains in the rocks. With the help of paleontological methods, the remains of ancient extinct organisms are studied. Each layer of rocks is characterized by its own complex of organic residues. There will be more remains of highly organized plants and animals in each young layer. The higher the layer is, the younger it is. A similar pattern was established by an Englishman W. Smith... He owns the first geological map of England, on which rocks were divided by age.

Non-paleontological methods determination of the relative age of rocks are used in cases where organic remains are absent. More effective then will be stratigraphic, lithological, tectonic, geophysical methods... With the help of the stratigraphic method, it is possible to determine the sequence of the bedding of layers at their normal occurrence, i.e. the underlying layers will be more ancient.

Remark 3

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

Geochronological table

Scientists use various methods to determine the age of rocks and to study them, and for this purpose a special scale has been drawn up. Geological time on this scale is divided into time intervals, each of which corresponds to a certain stage in the formation of the earth's crust and the development of living organisms. The scale was named geochronological table, in which the following divisions are distinguished: eon, era, period, era, century, time... Each geochronological subdivision is characterized by its own complex of deposits, which is called stratigraphic: eonoteme, group, system, department, tier, zone... A group, for example, is a stratigraphic unit, and a temporary geochronological unit corresponding to it represents era. Based on this, there are two scales - stratigraphic and geochronological... The first scale is used when it comes to sediments, because in any period of time some geological events took place on the Earth. The second scale is needed to determine relative time... Since its adoption, the content of the scale has changed and improved.

The largest stratigraphic subdivisions at present are eonothems - Archean, Proterozoic, Phanerozoic... In the geochronological scale, they correspond to zones of different duration. By the time of existence on Earth, there are Archean and Proterozoic eonothems covering almost $ 80% of the time. Phanerozoic eon the time is much shorter than the previous eons and covers only $ 570 million years. This ionotheme is divided into three main groups - Paleozoic, Mesozoic, Cenozoic.

The names of the eonothems and groups are of Greek origin:

Archeos means most ancient;
Proteros is primary;
Paleos is ancient;
Mesos - medium;
Kainos is new.

From the word “ zoiko with ", which means vital, the word" zoey". Based on this, eras of life on the planet are distinguished, for example, the Mesozoic era means the era of average life.

Eras and periods

According to the geochronological table, the history of the Earth is divided into five geological eras: Archean, Proterozoic, Paleozoic, Mesozoic, Cenozoic... In turn, the eras are subdivided into periods... There are much more of them - $ 12. The length of the periods varies from $ 20 - $ 100 million years. The last one indicates its incompleteness. Quaternary Cenozoic, its duration is only $ 1.8 million years.

Archean era. This time began after the formation of the earth's crust on the planet. By this time, there were mountains on Earth, and the processes of erosion and sedimentation began to take effect. Archaea lasted approximately $ 2 billion years. This era is the longest in duration, during which volcanic activity was widespread on Earth, there were deep uplifts, which resulted in the formation of mountains. Most of the fossils were destroyed under the influence of high temperature, pressure, and mass movement, but little data about that time have survived. In the rocks of the Archean era, pure carbon is found in dispersed form. Scientists believe that these are altered remains of animals and plants. If the amount of graphite reflects the amount of living matter, then there was a lot of it in the Archean.

Proterozoic era... In terms of duration, this is the second era, spanning $ 1 billion years. During the era, there was a large amount of sediment deposition and one significant glaciation. Ice sheets spread from the equator to $ 20 $ degrees of latitude. Fossils found in the rocks of this time are evidence of the existence of life and its evolutionary development. Sponge spicules, remains of jellyfish, fungi, algae, arthropods, etc. were found in the Proterozoic sediments.

Palaeozoic... In this era stands out six periods:

Cambrian;
Ordovician,
Silurian;
Devonian;
Carbon or coal;
Perm or Perm.

The duration of the Paleozoic is $ 370 million years. During this time, representatives of all types and classes of animals appeared. Only birds and mammals were missing.

Mesozoic era... The era is divided into three period:

Triassic;

The era began about $ 230 million years ago and lasted $ 167 million years. During the first two periods - Triassic and Jurassic- most of the mainland regions rose above sea level. The Triassic climate is dry and warm, and in the Jurassic it became even warmer, but was already humid. In state Arizona there is a famous stone forest that exists since Triassic period. True, only trunks, logs and stumps remained from the once mighty trees. At the end of the Mesozoic era, or rather in the Cretaceous period, a gradual advance of the sea takes place on the continents. The North American continent at the end of the Cretaceous period experienced submersion and as a result the waters of the Gulf of Mexico merged with the waters of the Arctic basin. The mainland was divided into two parts. The end of the Cretaceous period is characterized by a large uplift, called alpine mountain building... At this time, the Rocky Mountains, Alps, Himalayas, Andes appeared. Intense 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:

Paleogene;
Neogene;
Quaternary.

Quaternary the period has a number of unique features. This is the time of the final formation of the modern face of the Earth and the ice ages. New Guinea and Australia became independent, moving closer to Asia. Antarctica remained where it was. Two Americas have connected. Of the three periods of the era, the most interesting is quaternary period or anthropogenic... It continues today, and was allocated in $ 1829 by a Belgian geologist J. Denoyer... Cold snaps change with warming, but its most important feature is human appearance.

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

The history of planet Earth is already about 7 billion years old. During this time, our common home has undergone significant changes, which was a consequence of the change in 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 with new information and changed, as a result, now it reflects all geological periods in chronological order.

The largest subdivisions 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 come to the conclusion that the Earth formed about 4.5 billion years ago. The very process of its formation was very long and, possibly, began 7 billion years ago from small cosmic particles. Over time, the force of gravity grew, along with it the speed of bodies falling on the forming planet increased. Kinetic energy was transformed into heat, resulting in a gradual heating of the Earth.

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

Precambrian aeon

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, the lion's share of the planet's history is covered first. However, this eon is divided into three more - katarchean, archean, proterozoic. And often the first of them stands out as an independent eon.

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

Katarchean eon

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

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

The Catarchian Eon is a time when volcanic activity did not appear, and the surface of the Earth was a cold inhospitable desert. Although quite often there were earthquakes that smoothed the landscape. The surface looked like a dark gray primary material covered with a layer of regolith. A day at that time was only 6 hours.

Archean eon

The second main eon of the four in the history of the Earth lasted about 1.5 billion years - 4-2.5 billion years ago. Then the Earth did not yet have an atmosphere, therefore there was no life yet, however, bacteria appeared in this eon, 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 the 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 huge areas.

The formation of the so-called. 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 things appeared - the simplest 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 - explicit and latent. Phanerozoic refers to the explicit. At this time, a large number of living organisms with mineral skeletons appear. The epoch preceding the Phanerozoic was called hidden because practically no traces of it were found due to the absence of mineral skeletons.

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

Eras of the Precambrian Aeon

There were no generally recognized eras and periods during the Catarchean and Archean times, so we will skip their consideration.

The Proterozoic consists of three great eras:

Paleoproterozoic- that is, the ancient one, which includes the Siderius, the Riasian period, the Orosirian and Staterias. By the end of this era, the concentration of oxygen in the atmosphere had reached its present level.

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

Neoproterozoic- new, consisting of tonium, cryogeny and ediacaria. At this time, the formation of the first supercontinent, Rodinia, takes place, but then the plates parted again. The coldest ice age took place in an era called the Mesoproterozoic, during which most of the planet froze over.

Eras of the Phanerozoic aeon

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

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

Cambrian (a temperate climate is formed on Earth, the landscape is low, during this period all modern types of animals are born).
Ordovician (the climate on the entire planet is warm enough, even in Antarctica, while the land is sinking significantly. The first fish appear).
The Silurian period (the formation of large inland seas takes place, while the lowlands are becoming drier due to the uplift of the land. The development of fish continues. The Silurian period is marked by the appearance of the first insects).
Devon (emergence of the first amphibians and forests).
Lower Carboniferous (dominance of ferns, distribution of sharks).
Upper and Middle Carboniferous (appearance of the first reptiles).
Perm (most of the ancient animals are dying out).

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

Triassic (seed ferns die out, gymnosperms dominate, the first dinosaurs and mammals appear).
Jura (part of Europe and the western part of America are covered with shallow seas, the appearance of the first toothed birds).
Chalk (the emergence 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:

Tertiary. At the beginning of the period, predators and ungulates reach their dawn, the climate is warm. The forest spreads to its maximum extent, and the most ancient mammals are dying out. About 25 million years ago, humans appear and in the Pliocene epoch.
Quaternary. Pleistocene - large mammals are dying out, human society is emerging, 4 ice ages occur, many plant species are dying out. The modern era - the last ice age ends, gradually the climate takes on its present form. Human supremacy over the entire planet.

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

According to modern concepts, it is 4.5 - 5 billion years old. In the history of its origin, planetary and geological stages are distinguished.

Geological stage- the sequence of events in the development of the Earth as planets since the formation of the earth's crust. In the course of it, relief forms arose and collapsed, land was submerged under water (the advance of the sea), the sea retreated, glaciation, the appearance and disappearance of various species of animals and plants, etc.

Scientists, trying to reconstruct the history of the planet, study the layers of rocks. They divide all deposits into 5 groups, highlighting the following eras: Archean (oldest), Proterozoic (early), Paleozoic (ancient), Mesozoic (middle) and Cenozoic (new). The border between the eras runs along the largest evolutionary events. The last three eras are divided into periods, since in these deposits the remains of animals and plant remains are better preserved and in greater quantities.

Each era is characterized by events that have had a decisive impact on modern relief.

Archean era characterized by violent volcanic activity, as a result of which igneous granite-containing rocks appeared on the surface of the Earth - the basis of future continents. At that time, the Earth was inhabited only by microorganisms that could live without oxygen. It is believed that the deposits of that era cover individual land areas with an almost continuous shield, they contain a lot of iron, gold, silver, platinum and other metal ores.

V proterozoic era volcanic activity was also high; mountains of the so-called Baikal folding were formed. They have practically not survived and now represent only separate small uplifts on the plains. During this period, the planet was inhabited by blue-green algae and the simplest microorganisms, the first multicellular organisms arose. Proterozoic rock strata are rich in minerals: iron and non-ferrous metal ores, mica.

At the beginning paleozoic era formed the mountains Caledonian folding, which led to the reduction of sea basins and the emergence of significant areas of land. Only individual ridges of the Urals, Arabia, Southeast China and Central Europe have survived in the form of mountains. All these mountains are low, "worn out". In the second half of the Paleozoic, the mountains of the Hercynian folding were formed. This era of mountain building was more powerful, extensive mountain ranges arose in Western Siberia and the Urals, Mongolia and Manchuria, most of Central Europe, the east coast of North America and Australia. Now they are represented by low blocky mountains. In the Paleozoic era, the Earth is inhabited by fish, amphibians and reptiles, algae prevail among the vegetation. The main deposits of oil and coal arose precisely during this period.

Mesozoic era began with a period of relative calmness of the internal forces of the Earth, the gradual destruction of previously created mountain systems and submersion under water of smoothed flat territories, for example, most of Western Siberia. In the second half of the era, the mountains of the Mesozoic folding were formed. At this time, vast mountainous countries appeared, which now have the appearance of mountains. These are the Cordillera, the mountains of Eastern Siberia, parts of Tibet and Indochina. The land was covered with lush vegetation, which gradually died out and rotted. In a hot and humid climate, swamps and peat bogs were actively formed. This was the era of the dinosaurs. Giant carnivorous and herbivorous animals have spread almost all over the planet. At this time, the first mammals appeared.

Cenozoic era lasts to this day. Its beginning was marked by an increase in the activity of the internal forces of the Earth, which led to a general uplift of the surface. In the era of Alpine folding, young folded mountains arose within the Alpine-Himalayan belt and acquired the modern outlines of the continent of Eurasia. In addition, there was a rejuvenation of the ancient mountain ranges of the Urals, Appalachians, Tien Shan, Altai. The planet's climate changed dramatically, and a period of powerful ice sheets began. Covering glaciers advancing from the north have changed the topography of the continents of the Northern Hemisphere, forming hilly plains with a large number of lakes.

The entire geological history of the Earth can be traced on a geochronological scale - a table of geological time showing the sequence and co-subordination of the main stages of geology, the history of the Earth and the development of life on it (see Table 4 on pp. 46-49). The geochronological table should be read from bottom to top.

Questions and tasks to prepare for the exam

1. Explain why there are polar days and nights on Earth.
2. What would be the conditions on the Earth if the axis of its rotation was not tilted to the orbital plane?
3. The change of seasons on the Earth is determined by two main reasons: the first is the revolution of the Earth around the Sun; name the second.
4. How many times a year and when is the Sun at its zenith above the equator? Over the Northern Tropic? Over the South Tropic?
5. In which direction do constant winds and sea currents moving in the meridional direction deviate in the Northern Hemisphere?
6. When is the shortest night in the Northern Hemisphere?
7. What are the characteristics of the days of the spring and autumn equinox on Earth? When do they attack in the Northern and Southern Hemispheres?
8. When are the days of the summer and winter solstices in the Northern and Southern Hemispheres?
9. In what zones of illumination is the territory of our country located?
10. List the geological periods of the Cenozoic era, starting with the most ancient.

Table 4

Geochronological scale

Eras (duration - in million years)	Periods (duration in million years)	Major events in the history of the Earth	Characteristic minerals formed at a given time
1	2	3	4
Cenozoic 70 Ma	Quaternary 2 Ma (Q)	General land elevation. Repeated cover glaciations, especially in the Northern Hemisphere. The appearance of man	Peat, placer deposits of gold, diamonds, dredges, stones
	Neogene 25 Ma (N)	The emergence of young mountains in areas of alpine folding. Rejuvenation of mountains in areas of all ancient folds. Dominance of flowering plants	Brown coals, oil, amber
	Paleogene 41 Ma (P)	Destruction of Mesozoic mountains. Widespread development of flowering plants, birds and mammals	Phosphorites, brown coal, bauxite

Mesozoic 165 Ma	Cretaceous 70 Ma (K)	The emergence of young mountains in areas of Mesozoic folding. Extinction of giant reptiles (dinosaurs). Development of birds and mammals	Oil, oil shale, chalk, coal, phosphorites
	Jurassic 50 Ma (J)	Formation of modern oceans. Hot and humid climate over most of the land. The heyday of giant reptiles (dinosaurs). Dominance of gymnosperms	Bituminous coals, oil, phosphorites
	Triassic 40 Ma (T)	The largest sea retreat and land uplift in the history of the Earth. Destruction of the mountains of the Caledonian and Hercynian folds. Vast deserts. The first mammals	Rock salt
1	2	3	4
Paleozoic 330 Ma	Perm 45 Ma (R)	The emergence of young folded mountains in the areas of Hercynean folding. Dry climate on most of the land. The emergence of gymnosperms	Rock and potassium salts, gypsum
	Carboniferous 65 Ma (C)	Hot and humid climate over most of the land. Widespread marshy lowlands in coastal areas. Treelike fern forests. The first reptiles, the flowering of amphibians	Bituminous coal, oil
	Devonian 55 Ma (r)	Hot climate on most of the land. The first deserts. The emergence of amphibians. Numerous fish	Salts, oil
	Silurian 35 Ma (S)	The emergence of young folded mountains in the areas of the Caledonian folding. The first terrestrial plants (moss and ferns)

	Ordovician 60 Ma (O)	Reduction of the area of sea basins. The appearance of the first terrestrial invertebrates
	Cambrian 70 Ma	The emergence of young mountains in the areas of Baikal folding. Flooding of vast areas by seas. The flourishing of marine invertebrates	Rock salt, gypsum, phosphorites
Proterozoic era 600 million years		The beginning of the Baikal folding. Powerful volcanism. Development of bacteria and blue-green algae	Iron ores, mica, graphite
Archean era 900 million years		Formation of the continental crust. Intense volcanic activity. Time of primitive unicellular bacteria	Ores

Maksakovsky V.P., Petrova N.N., Physical and economic geography of the world. - M.: Ayris-press, 2010 .-- 368s.: Ill.

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The origin of life on Earth took place about 3.8 billion years ago, when the formation of the earth's crust ended. Scientists have found that the first living organisms appeared in the aquatic environment, and only a billion years later the first creatures came to the surface of the land.

The formation of terrestrial flora was facilitated by the formation of organs and tissues in plants, the ability to reproduce by spores. Animals also evolved significantly and adapted to life on land: internal fertilization, the ability to lay eggs, and pulmonary respiration appeared. An important stage in development was the formation of the brain, conditioned and unconditioned reflexes, survival instincts. Further evolution of animals provided the basis for the formation of mankind.

Dividing the history of the Earth into eras and periods gives an idea of the peculiarities of the development of life on the planet at different time intervals. Scientists identify especially significant events in the formation of life on Earth in separate periods of time - eras, which are divided into periods.

There are five eras:

Archean;
proterozoic;
paleozoic;
Mesozoic;
Cenozoic.

The Archean era began about 4.6 billion years ago, when the planet Earth was just beginning to form and there were no signs of life on it. The air contained chlorine, ammonia, hydrogen, the temperature reached 80 °, the radiation level exceeded the permissible limits, under such conditions the birth of life was impossible.

It is believed that about 4 billion years ago, our planet collided with a celestial body, and the result was the formation of a satellite of the Earth - the Moon. This event became significant in the development of life, stabilized the axis of rotation of the planet, and contributed to the purification of water structures. As a result, the first life was born at the depths of the oceans and seas: protozoa, bacteria and cyanobacteria.

The Proterozoic era lasted from about 2.5 billion years to 540 million years ago. The remains of unicellular algae, molluscs, annelids were found. Soil begins to form.

The air at the beginning of the era was not yet saturated with oxygen, but in the process of vital activity the bacteria inhabiting the seas began to release more O 2 into the atmosphere. When the amount of oxygen was at a stable level, many creatures took a step in evolution and switched to aerobic respiration.

The Paleozoic era includes six periods.

Cambrian period(530 - 490 million years ago) is characterized by the emergence of representatives of all species of plants and animals. The oceans were inhabited by algae, arthropods, molluscs, and the first chordates (haikouichtis) appeared. The dry land remained uninhabited. The temperature remained high.

Ordovician period(490 - 442 million years ago). The first lichen settlements appeared on land, and the megalograpt (a representative of arthropods) began to go ashore to lay eggs. Vertebrates, coral, and sponges continue to develop in the ocean.

Silurian(442 - 418 million years ago). Plants emerge on land, and the rudiments of lung tissue form in arthropods. The formation of the bone skeleton in vertebrates is completed, sensory organs appear. Mountain building is in progress, different climatic zones are being formed.

Devonian(418 - 353 million years ago). The formation of the first forests, mainly ferns, is characteristic. Bone and cartilaginous organisms appear in reservoirs, amphibians began to emerge on land, new organisms - insects - are formed.

Carboniferous period(353 - 290 million years ago). The appearance of amphibians, the subsidence of the continents occurs, at the end of the period there was a significant cooling, which led to the extinction of many species.

Permian period(290 - 248 million years ago). The earth is inhabited by reptiles, therapsids appeared - the ancestors of mammals. The hot climate led to the formation of deserts, where only hardy ferns and some conifers could survive.

The Mesozoic era is divided into 3 periods:

Triassic(248 - 200 million years ago). The development of gymnosperms, the appearance of the first mammals. The split of the landmass into continents.

Jurassic period(200 - 140 million years ago). The emergence of angiosperms. The appearance of the ancestors of birds.

Cretaceous period(140 - 65 million years ago). Angiosperms (flowering) have become the dominant group of plants. The development of higher mammals, real birds.

The Cenozoic era consists of three periods:

Lower Tertiary or Paleogene(65 - 24 million years ago). The disappearance of most cephalopods, lemurs and primates appear, later parapithecus and dryopithecus. The development of the ancestors of modern mammalian species - rhinos, pigs, rabbits, etc.

Upper Tertiary or Neogene(24 - 2.6 million years ago). Mammals inhabit land, water, air. The appearance of Australopithecus - the first ancestors of humans. During this period, the Alps, Himalayas, and Andes were formed.

Quaternary period or anthropogen(2.6 million years ago - today). A significant event of the period is the appearance of man, first the Neanderthals, and soon Homo sapiens. The flora and fauna acquired modern features.

The periods of the geological history of the Earth are epochs, the successive change of which has shaped it as a planet. At this time, mountains formed and collapsed, seas appeared and dried up, ice ages replaced each other, the evolution of the animal world took place. The study of the geological history of the Earth is carried out on sections of rocks that have retained the mineral composition of the period that formed them.

Cenozoic period

The current period of the geological history of the Earth is the Cenozoic. It began sixty-six million years ago and continues to last. The conditional boundary was drawn by geologists at the end of the Cretaceous period, when there was a mass extinction of species.

The term was coined by the English geologist Phillips back in the middle of the nineteenth century. Its literal translation sounds like "new life". The era is divided into three periods, each of which, in turn, is subdivided into eras.

Geological periods

Any geological era is divided into periods. In the Cenozoic era, three periods are distinguished:

Paleogene;

The Quaternary Period of the Cenozoic Era, or Anthropogen.

In earlier terminology, the first two periods were combined under the name "tertiary period".

On land, which had not yet had time to finally split into separate continents, mammals reigned. Rodents and insectivores, early primates, appeared. In the seas, reptiles have been replaced by predatory fish and sharks, new species of mollusks and algae have appeared. Thirty-eight million years ago, the diversity of species on Earth was amazing, the evolutionary process affected representatives of all kingdoms.

Only five million years ago, the first great apes began to walk on land. Three million years later, in the territory belonging to modern Africa, Homo erectus began to gather in tribes, collect roots and mushrooms. Ten thousand years ago, modern man appeared who began to reshape the Earth to suit his needs.

Paleography

The Paleogene lasted forty-three million years. The continents in their present form were still part of Gondwana, which was beginning to split into separate fragments. South America was the first to sail freely, becoming a reservoir for unique plants and animals. In the Eocene epoch, the continents gradually take their present position. Antarctica separates from South America and India moves closer to Asia. A body of water appeared between North America and Eurasia.

In the Oligocene epoch, the climate becomes cool, India finally consolidates below the equator, and Australia drifts between Asia and Antarctica, moving away from both. Due to temperature changes at the South Pole, ice caps are formed, which leads to a decrease in sea levels.

In the Neogene period, continents begin to collide with each other. Africa "rams" Europe, resulting in the emergence of the Alps, India and Asia forms the Himalayan mountains. The Andes and rocky mountains appear in the same way. In the Pliocene era, the world becomes even colder, forests die out, giving way to steppes.

Two million years ago, a period of glaciation sets in, the sea level fluctuates, the white caps at the poles are growing and then melting again. The flora and fauna are being tested. Today, humanity is going through one of the warming stages, but globally, the ice age continues to last.

Life in the Cenozoic

The Cenozoic periods cover a relatively short period of time. If we put the entire geological history of the earth on the dial, then the last two minutes will be allocated for the Cenozoic.

Extinction, which marked the end of the Cretaceous period and the beginning of a new era, wiped out all animals that were larger than a crocodile from the face of the Earth. Those who managed to survive were able to adapt to new conditions or evolved. The drift of the continents continued until the appearance of people, and on those of them that were isolated, the unique flora and fauna could survive.

The Cenozoic era was distinguished by a large species diversity of flora and fauna. It is called the time of mammals and angiosperms. In addition, this era can be called the era of steppes, savannas, insects and flowering plants. The emergence of Homo sapiens can be considered the crown of the evolutionary process on Earth.

Quaternary period

Modern humanity lives in the Quaternary era of the Cenozoic era. It began two and a half million years ago, when in Africa, great apes began to stray into tribes and get themselves food by gathering berries and digging up roots.

The Quaternary period was marked by the formation of mountains and seas, the movement of continents. The earth has acquired the form that it has now. For geologists, this period is just a stumbling block, since its duration is so short that the methods of radioisotope scanning of rocks are simply not sensitive enough and give out large errors.

The characteristics of the Quaternary period are made up of materials obtained using radiocarbon analysis. This method is based on measuring the amount of rapidly decaying isotopes in soil and rocks, as well as bones and tissues of extinct animals. The entire period of time can be divided into two eras: the Pleistocene and the Holocene. Humanity is now in the second era. There is no exact estimate yet when it will end, but scientists continue to hypothesize.

Pleistocene epoch

The Quaternary period opens the Pleistocene. It began two and a half million years ago and ended only twelve thousand years ago. It was the time of glaciation. Long ice ages were interspersed with short warmings.

A hundred thousand years ago, a thick ice cap appeared in the area of modern Northern Europe, which began to spread in different directions, absorbing more and more territories. Animals and plants were forced to either adapt to new conditions or die. The frozen desert stretches from Asia to North America. In some places, the ice was up to two kilometers thick.

The beginning of the Quaternary period turned out to be too harsh for the creatures that inhabited the earth. They are used to warm, temperate climates. In addition, ancient people began to hunt animals, who had already invented the stone ax and other hand tools. Whole species of mammals, birds and representatives of marine fauna disappear from the face of the Earth. The Neanderthal could not stand the harsh conditions either. Cro-Magnons were more resilient, more successful in hunting, and it was their genetic material that had to survive.

Holocene era

The second half of the Quaternary period began twelve thousand years ago and continues to this day. It is characterized by relative warming and climate stabilization. The beginning of the era was marked by the mass extinction of animals, and it continued with the development of human civilization, its technical flourishing.

Changes in animal and plant composition throughout the era were insignificant. Mammoths finally died out, some species of birds and marine mammals ceased to exist. About seventy years ago, the overall temperature on earth increased. Scientists attribute this to the fact that human industrial activity is causing global warming. In this regard, glaciers in North America and Eurasia have melted, and the ice cover of the Arctic is disintegrating.

ice Age

The Ice Age is a stage in the geological history of the planet, which takes several million years, during which there is a decrease in temperature and an increase in the number of continental glaciers. As a rule, glaciations alternate with warming. Now the Earth is in a period of relative temperature rise, but this does not mean that in half a millennium the situation cannot change dramatically.

At the end of the nineteenth century, the geologist Kropotkin visited the Lena gold mines with an expedition and discovered signs of ancient glaciation there. He was so interested in the findings that he took up large-scale international work in this direction. First of all, he visited Finland and Sweden, as he suggested that it was from there that the ice caps spread to Eastern Europe and Asia. Kropotkin's reports and his hypotheses regarding the modern ice age formed the basis of modern ideas about this period of time.

History of the earth

The Ice Age, in which the Earth is now, is far from the first in our history. Cooling of the climate happened before. It was accompanied by significant changes in the relief of continents and their movement, and also influenced the species composition of flora and fauna. There could be intervals of hundreds of thousands and millions of years between glaciers. Each ice age is divided into ice ages or glacials, which alternate with interglacials - interglacials during the period.

There are four glacial eras in the history of the Earth:

Early Proterozoic.

Late Proterozoic.

Paleozoic.

Cenozoic.

Each of them lasted from 400 million to 2 billion years. This suggests that our ice age has not even reached its equator yet.

Cenozoic Ice Age

Quaternary animals were forced to grow extra fur or seek shelter from ice and snow. The planet's climate has changed again.

The first epoch of the Quaternary was characterized by a cooling, and in the second there was a relative warming, but even now, in the most extreme latitudes and at the poles, the ice cover persists. It covers the territory of the Arctic, Antarctica and Greenland. The thickness of the ice varies from two thousand meters to five thousand.

The most powerful in the entire Cenozoic era is the Pleistocene Ice Age, when the temperature dropped so much that three out of five oceans on the planet were frozen.

Chronology of the Cenozoic glaciations

Quaternary glaciation began recently, if we consider this phenomenon in relation to the history of the Earth as a whole. It is possible to distinguish individual epochs during which the temperature dropped especially low.

End of the Eocene (38 million years ago) - glaciation of Antarctica.
The entire Oligocene.
Middle Miocene.
Mid Pliocene.
Glacial Gilbert, freezing of the seas.
Continental Pleistocene.
Late Upper Pleistocene (about ten thousand years ago).

This was the last major period when, due to the cooling of the climate, animals and humans had to adapt to new conditions in order to survive.

Paleozoic Ice Age

In the Paleozoic era, the Earth was frozen so hard that ice caps reached Africa and South America in the south, and also covered all of North America and Europe. The two glaciers almost converged along the equator. The peak is considered the moment when a three-kilometer layer of ice rose over the territory of northern and western Africa.

Scientists have discovered the remnants and effects of glacial deposits during research in Brazil, Africa (in Nigeria) and the mouth of the Amazon River. Thanks to radioisotope analysis, it was found that the age and chemical composition of these finds are the same. This means that it can be argued that the rock layers were formed as a result of one global process that affected several continents at once.

The planet Earth is still very young by cosmic standards. She is just beginning her journey in the Universe. It is not known whether it will continue with us or whether humanity will simply become an insignificant episode in successive geological eras. If you look at the calendar, we have spent a negligible amount of time on this planet, and it is quite easy to destroy us with the help of another cold snap. People need to remember this and not exaggerate their role in the biological system of the Earth.