is the totality of all forms of the earth's surface. They can be horizontal, inclined, convex, concave, complex.

The height difference between the highest peak on land, Mount Chomolungma in the Himalayas (8848 m), and the Mariana Trench in the Pacific Ocean (11,022 m) is 19,870 m.

How was the relief of our planet formed? In the history of the Earth, two main stages of its formation are distinguished:

• planetary(5.5-5.0 million years ago), which ended with the formation of the planet, the formation of the core and mantle of the Earth;
• geological, which began 4.5 million years ago and continues to this day. It was at this stage that the formation of the earth's crust occurred.

The source of information about the development of the Earth during the geological stage is primarily sedimentary rocks, which in the vast majority were formed in the aquatic environment and therefore occur in layers. The deeper the layer lies from the earth's surface, the earlier it was formed and, therefore, is more ancient with respect to any layer that is closer to the surface and is younger. This simple reasoning is based on the concept relative age of rocks, which formed the basis for the construction geochronological table(Table 1).

The longest time intervals in geochronology are − zones(from Greek. aion- century, epoch). There are such zones as: cryptozoic(from Greek. cryptos- hidden and zoe- life), covering the entire Precambrian, in the deposits of which there are no remains of skeletal fauna; phanerozoic(from Greek. phaneros- explicit, zoe- life) - from the beginning of the Cambrian to our time, with a rich organic life, including skeletal fauna. The zones are not equal in duration, so if the Cryptozoic lasted 3-5 billion years, then the Phanerozoic lasted 0.57 billion years.

Table 1. Geological table

Era. letter designation, duration	The main stages of the development of life	Periods, letter designation, duration	major geological events. The shape of the earth's surface	Most Common Minerals
Cenozoic, KZ, about 70 Ma	dominance of angiosperms. The rise of the mammalian fauna. The existence of natural zones close to modern ones, with repeated displacements of boundaries	Quaternary, or Anthropogenic, Q, 2 million years	General uplift of the territory. repeated glaciations. The appearance of man	Peat. Alluvial deposits of gold, diamonds, precious stones
		Neogene, N, 25 Ma	The emergence of young mountains in the areas of Cenozoic folding. The revival of mountains in the regions of all ancient foldings. Dominance of angiosperms (flowering) plants	Brown coals, oil, amber
		Paleogene, P, 41 Ma	Destruction of the Mesozoic mountains. Wide distribution of flowering plants, development of birds and mammals	Phosphorites, brown coals, bauxites
Mesozoic, MZ, 165 Ma		Cretaceous, K, 70 Ma	The emergence of young mountains in the areas of Mesozoic folding. Extinction of giant reptiles (reptiles). Development of birds and mammals	Oil, oil shale, chalk, coal, phosphorites
		Jurassic, J, 50 Ma	Formation of modern oceans. Hot, humid climate. The rise of reptiles. dominance of gymnosperms. Appearance of primitive birds	Coals, oil, phosphorites
		Triassic, T, 45 Ma	The greatest retreat of the sea and the rise of the continents in the entire history of the Earth. Destruction of pre-Mesozoic mountains. Vast deserts. First mammals	rock salts
Paleozoic, PZ, 330 Ma	The flowering of ferns and other spore plants. Time for fish and amphibians	Permian, R, 45 Ma	The emergence of young mountains in areas of Hercynian folding. Dry climate. The emergence of gymnosperms	Rock and potash salts, gypsum
		Carboniferous (Carboniferous), C, 65 Ma	Widespread swampy lowlands. Hot, humid climate. Development of forests from tree ferns, horsetails and club mosses. The first reptiles The heyday of amphibians	Abundance of coal and oil
		Devonian, D, 55 million years	Reduction of the seas. Hot climate. First deserts. The appearance of amphibians. Numerous fish	Salt, oil
	The appearance of animals and plants on Earth	Silurian, S, 35 Ma	The emergence of young mountains in the areas of the Caledonian folding. The first land plants
		Ordovician, O, 60 Ma	Decrease in the area of ​​marine basins. Appearance of the first terrestrial invertebrates
		Cambrian, E, 70 Ma	The emergence of young mountains in the areas of Baikal folding. Flooding of vast areas by the seas. The rise of marine invertebrates	Rock salt, gypsum, phosphate rock
Proterozoic, PR. about 2000 Ma	Origin of life in water. Bacteria and algae time		Beginning of the Baikal folding. Powerful volcanism. Bacteria and algae time	Huge reserves of iron ores, mica, graphite
Archean, AR. over 1000 million years			Ancient folding. Intense volcanic activity. Time of primitive bacteria	Iron ores

The zones are divided into era. In the cryptozoic, there are Archean(from Greek. archaios- primordial, ancient aion- century, era) and Proterozoic(from Greek. proteros- earlier, zoe - life) era; in the Phanerozoic Paleozoic(from Greek ancient and life), Mesozoic(from Greek. tesos - middle, zoe - life) and Cenozoic(from Greek. kainos- new, zoe - life).

Eras are divided into shorter periods of time - periods established only for the Phanerozoic (see Table 1).

The main stages in the development of the geographical envelope

The geographical envelope has come a long and difficult path of development. There are three qualitatively different stages in its development: pre-biogenic, biogenic, and anthropogenic.

pre-biogenic stage(4 billion - 570 million years) - the longest period. At this time, the process of increasing the thickness and complicating the composition of the earth's crust took place. By the end of the Archean (2.6 billion years ago), a continental crust about 30 km thick had already formed over vast areas, and in the Early Proterozoic, protoplatforms and protogeosynclines separated. During this period, the hydrosphere already existed, but the volume of water in it was less than now. Of the oceans (and then only by the end of the early Proterozoic) one took shape. The water in it was salty and the salinity level most likely was about the same as now. But, apparently, in the waters of the ancient ocean, the predominance of sodium over potassium was even greater than now, there were also more magnesium ions, which is associated with the composition of the primary earth's crust, the weathering products of which were carried into the ocean.

The Earth's atmosphere at this stage of development contained very little oxygen, and there was no ozone screen.

Life most likely existed from the very beginning of this stage. According to indirect data, microorganisms lived already 3.8-3.9 billion years ago. The discovered remains of the simplest organisms are 3.5-3.6 billion years old. However, organic life from the moment of its inception to the very end of the Proterozoic did not play a leading, determining role in the development of the geographical envelope. In addition, many scientists deny the presence of organic life on land at this stage.

The evolution of organic life to the pre-biogenic stage proceeded slowly, but nevertheless, 650-570 million years ago, life in the oceans was quite rich.

Biogenic stage(570 million - 40 thousand years) lasted during the Paleozoic, Mesozoic and almost the entire Cenozoic, with the exception of the last 40 thousand years.

The evolution of living organisms during the biogenic stage was not smooth: eras of relatively calm evolution were replaced by periods of rapid and deep transformations, during which some forms of flora and fauna died out and others became widespread.

Simultaneously with the appearance of terrestrial living organisms, soils began to form in our modern understanding.

Anthropogenic stage began 40 thousand years ago and continues today. Although man as a biological species appeared 2-3 million years ago, his impact on nature for a long time remained extremely limited. With the advent of Homo sapiens, this impact has increased significantly. It happened 38-40 thousand years ago. From here the anthropogenic stage in the development of the geographic envelope takes its countdown.

Geological chronology, or geochronology, is based on elucidating the geological history of the most well-studied regions, for example, in Central and Eastern Europe. Based on broad generalizations, comparison of the geological history of various regions of the Earth, patterns of evolution of the organic world at the end of the last century, at the first International Geological Congresses, the International Geochronological Scale was developed and adopted, reflecting the sequence of time divisions during which certain sediment complexes were formed, and the evolution of the organic world . Thus, the international geochronological scale is a natural periodization of the history of the Earth.

Among the geochronological divisions are distinguished: eon, era, period, epoch, century, time. Each geochronological subdivision corresponds to a set of deposits, identified in accordance with the change in the organic world and called stratigraphic: eonoteme, group, system, department, stage, zone. Therefore, the group is a stratigraphic unit, and the corresponding temporal geochronological unit is represented by an era. Therefore, there are two scales: geochronological and stratigraphic. The first is used when talking about relative time in the history of the Earth, and the second when dealing with sediments, since some geological events occurred in every place on the globe in any period of time. Another thing is that the accumulation of precipitation was not ubiquitous.

• The Archean and Proterozoic eonotemes, covering almost 80% of the time of the Earth's existence, are distinguished in the Cryptozoic, since the skeletal fauna is completely absent in the Precambrian formations and the paleontological method is not applicable to their division. Therefore, the division of Precambrian formations is based primarily on general geological and radiometric data.
• The Phanerozoic eon covers only 570 million years, and the division of the corresponding eonoteme of deposits is based on a wide variety of numerous skeletal fauna. The Phanerozoic eonoteme is subdivided into three groups: Paleozoic, Mesozoic and Cenozoic, corresponding to major stages in the natural geological history of the Earth, the boundaries of which are marked by rather abrupt changes in the organic world.

The names of eonotems and groups come from Greek words:

• "archeos" - the most ancient, most ancient;
• "proteros" - primary;
• "paleos" - ancient;
• "mesos" - medium;
• "kainos" - new.

The word "cryptos" means hidden, and "phanerozoic" means explicit, transparent, since the skeletal fauna appeared.
The word "zoi" comes from "zoikos" - life. Therefore, "Cenozoic era" means the era of new life, and so on.

Groups are subdivided into systems, the deposits of which were formed during one period and are characterized only by their characteristic families or genera of organisms, and if these are plants, then by genera and species. Systems have been isolated in different regions and at different times since 1822. At present, 12 systems are distinguished, the names of most of which come from the places where they were first described. For example, the Jurassic system - from the Jura Mountains in Switzerland, the Permian - from the Perm province in Russia, the Cretaceous - according to the most characteristic rocks - white writing chalk, etc. The Quaternary system is often called Anthropogenic, since it is in this age interval that a person appears.

The systems are subdivided into two or three divisions, which correspond to the early, middle, and late eras. The departments, in turn, are divided into tiers, which are characterized by the presence of certain genera and species of fossil fauna. And, finally, the stages are subdivided into zones, which are the most fractional part of the international stratigraphic scale, which corresponds to time in the geochronological scale. The names of the stages are usually given according to the geographical names of the regions where this stage was distinguished; for example, the Aldanian, Bashkirian, Maastrichtian stages, etc. At the same time, the zone is designated by the most characteristic type of fossil fauna. The zone covers, as a rule, only a certain part of the region and is developed over a smaller area than the deposits of the stage.

All subdivisions of the stratigraphic scale correspond to the geological sections in which these subdivisions were first identified. Therefore, such sections are standard, typical, and are called stratotypes, which contain only their own complex of organic remains, which determines the stratigraphic volume of a given stratotype. Determining the relative age of any layers consists in comparing the discovered complex of organic remains in the studied layers with the complex of fossils in the stratotype of the corresponding division of the international geochronological scale, i.e. the age of the deposits is determined relative to the stratotype. That is why the paleontological method, despite its inherent shortcomings, remains the most important method for determining the geological age of rocks. Determining the relative age of, for example, the Devonian deposits only indicates that these deposits are younger than the Silurian, but older than the Carboniferous. However, it is impossible to establish the duration of the formation of the Devonian deposits and give a conclusion about when (in absolute chronology) the accumulation of these deposits occurred. Only methods of absolute geochronology are able to answer this question.

Tab. 1. Geological table

Era	Period	Epoch	Duration, Ma	Time from the beginning of the period to the present day, million years	Geological conditions	Vegetable world	Animal world
Cenozoic (time of mammals)	Quaternary	Modern	0,011	0,011	End of the last ice age. The climate is warm	The decline of woody forms, the flowering of herbaceous	Age of Man
		Pleistocene	1	1	repeated glaciations. four ice ages	Extinction of many plant species	Extinction of large mammals. The origin of human society
	Tertiary	Pliocene	12	13	The uplift of mountains in the west of North America continues. Volcanic activity	Decay of forests. Spread of meadows. flowering plants; development of monocots	The emergence of man from the great apes. Types of elephants, horses, camels, similar to modern
		Miocene	13	25	The Sierras and the Cascade Mountains formed. Volcanic activity in the northwestern United States. The climate is cool		The culminating period in the evolution of mammals. The first great apes
		Oligocene	11	30	The continents are low. The climate is warm	Maximum distribution of forests. Strengthening the development of monocotyledonous flowering plants	Archaic mammals are dying out. The beginning of the development of anthropoids; ancestors of most extant genera of mammals
		Eocene	22	58	The mountains are blurred. There are no inland seas. The climate is warm		Diverse and specialized placental mammals. Ungulates and carnivores flourish
		Paleocene	5	63			Distribution of archaic mammals
Alpine orogeny (minor destruction of fossils)
Mesozoic (time of reptiles)	Chalk		72	135	At the end of the period, the Andes, the Alps, the Himalayas, the Rocky Mountains are formed. Prior to this, inland seas and swamps. Deposition of writing chalk, shale	The first monocots. The first oak and maple forests. Decline of gymnosperms	Dinosaurs reach the highest development and die out. Toothed birds are dying out. Appearance of the first modern birds. Archaic mammals are common
	Yura		46	181	The continents are quite elevated. Shallow seas cover parts of Europe and the western United States	The value of dicots increases. Cycadophytes and conifers are common	The first toothed birds. Dinosaurs are large and specialized. Insectivorous marsupials
	Triassic		49	230	Continents are elevated above sea level. Intensive development of arid climate conditions. Widespread continental deposits	The dominance of the gymnosperms, already beginning to decline. Extinction of seed ferns	The first dinosaurs, pterosaurs and egg-laying mammals. Extinction of primitive amphibians
Hercynian orogeny (some destruction of fossils)
Paleozoic (era of ancient life)	Permian		50	280	Continents are raised. Appalachian mountains formed. Dryness is getting worse. Glaciation in the southern hemisphere	Decline of club mosses and ferns	Many ancient animals are dying out. Animal reptiles and insects develop
	Upper and Middle Carboniferous		40	320	The continents are initially low-lying. Vast swamps in which coal was formed	Large forests of seed ferns and gymnosperms	The first reptiles. Insects are common. Distribution of ancient amphibians
	Lower Carboniferous		25	345	The climate is initially warm and humid, later, due to the rise of the land, it becomes cooler.	Club mosses and fern-like plants dominate. Gymnosperms are spreading more and more	Sea lilies reach their highest development. Distribution of ancient sharks
	Devonian		60	405	Inland seas are small. Land elevation; development of an arid climate. Glaciation	First forests. Land plants are well developed. First gymnosperms	The first amphibians. Abundance of lungfish and sharks
	Silurus		20	425	Vast inland seas. Low-lying areas are getting drier as the land rises	The first reliable traces of land plants. Algae dominate	Marine arachnids dominate. The first (wingless) insects. Increased development of fish
	Ordovician		75	500	Significant land sink. The climate is warm, even in the Arctic	Probably the first land plants appear. Abundance of seaweed	The first fish are probably freshwater. Abundance of corals and trilobites. Various clams
	Cambrian		100	600	The continents are low, the climate is temperate. The most ancient rocks with abundant fossils	Seaweed	Trilobites and lechenopods dominate. The origin of most modern animal phyla
Second great orogeny (significant destruction of fossils)
Proterozoic			1000	1600	Intensive process of sedimentation. Later - volcanic activity. Erosion over large areas. Multiple glaciations	Primitive aquatic plants - algae, fungi	Various marine protozoa. By the end of the era - mollusks, worms and other marine invertebrates
First great mountain building (significant destruction of fossils)
archaeus			2000	3600	Significant volcanic activity. Weak sedimentation process. Erosion on large areas	Fossils are absent. Indirect evidence of the existence of living organisms in the form of deposits of organic matter in rocks

The problem of determining the absolute age of rocks, the duration of the existence of the Earth has long occupied the minds of geologists, and attempts to solve it have been made many times, for which various phenomena and processes have been used. Early ideas about the absolute age of the Earth were curious. A contemporary of M. V. Lomonosov, the French naturalist Buffon determined the age of our planet at only 74,800 years. Other scientists gave different figures, not exceeding 400-500 million years. It should be noted here that all these attempts were doomed to failure in advance, since they proceeded from the constancy of the rates of processes, which, as is known, changed in the geological history of the Earth. And only in the first half of the XX century. there was a real opportunity to measure the really absolute age of rocks, geological processes and the Earth as a planet.

Tab.2. Isotopes used to determine absolute ages
parent isotope	Final product	Half-life, billion years
147cm	143 Nd+He	106
238 U	206 Pb+ 8 He	4,46
235 U	208 Pb+ 7 He	0,70
232Th	208 Pb+ 6 He	14,00
87Rb	87 Sr+β	48,80
40K	40 Ar+ 40 Ca	1,30
14C	14 N	5730 years

Life on Earth originated over 3.5 billion years ago, immediately after the completion of the formation of the earth's crust. Throughout time, the emergence and development of living organisms influenced the formation of relief and climate. Also, tectonic and climatic changes that have taken place over the years have influenced the development of life on Earth.

A table of the development of life on Earth can be compiled based on the chronology of events. The entire history of the Earth can be divided into certain stages. The largest of them are the eras of life. They are divided into eras, eras - into - into eras, eras - into centuries.

Ages of life on earth

The entire period of the existence of life on Earth can be divided into 2 periods: the Precambrian, or Cryptozoic (primary period, 3.6 to 0.6 billion years), and Phanerozoic.

Cryptozoic includes the Archean (ancient life) and Proterozoic (primary life) eras.

Phanerozoic includes the Paleozoic (ancient life), Mesozoic (middle life) and Cenozoic (new life) eras.

These 2 periods of development of life are usually divided into smaller ones - eras. The boundaries between eras are global evolutionary events, extinctions. In turn, eras are divided into periods, periods - into epochs. The history of the development of life on Earth is directly related to changes in the earth's crust and the planet's climate.

Era of development, countdown

It is customary to single out the most significant events in special time intervals - eras. Time is counted backwards, from ancient life to the new. There are 5 eras:

1. Archean.
2. Proterozoic.
3. Paleozoic.
4. Mesozoic.
5. Cenozoic.

Periods of development of life on Earth

The Paleozoic, Mesozoic and Cenozoic eras include periods of development. These are smaller periods of time, compared to eras.

Palaeozoic:

• Cambrian (Cambrian).
• Ordovician.
• Silurian (Silur).
• Devonian (Devonian).
• Carboniferous (carbon).
• Perm (Perm).

Mesozoic era:

• Triassic (Triassic).
• Jura (Jurassic).
• Cretaceous (chalk).

Cenozoic era:

• Lower Tertiary (Paleogene).
• Upper Tertiary (Neogene).
• Quaternary, or anthropogen (human development).

The first 2 periods are included in the Tertiary period lasting 59 million years.

Table of the development of life on Earth

era, period	Duration	Live nature	Inanimate nature, climate
Archean era (ancient life)	3.5 billion years	The appearance of blue-green algae, photosynthesis. Heterotrophs	The predominance of land over the ocean, the minimum amount of oxygen in the atmosphere.
Proterozoic era (early life)	2.7 Ga	The appearance of worms, mollusks, the first chordates, soil formation.	The land is a stone desert. Accumulation of oxygen in the atmosphere.
The Paleozoic era includes 6 periods:
1. Cambrian (Cambrian)	535-490 Ma	development of living organisms.	Hot climate. The dry land is deserted.
2. Ordovician	490-443 Ma	The emergence of vertebrates.	Flooding of almost all platforms with water.
3. Silurian (Silur)	443-418 Ma	Exit of plants to land. Development of corals, trilobites.	with the formation of mountains. The seas prevail over the land. The climate is varied.
4. Devonian (Devonian)	418-360 Ma	The appearance of fungi, lobe-finned fish.	Formation of intermountain depressions. The predominance of a dry climate.
5. Carboniferous (carbon)	360-295 Ma	Appearance of the first amphibians.	The sinking of the continents with the flooding of territories and the emergence of swamps. The atmosphere contains a lot of oxygen and carbon dioxide.
6. Perm (Perm)	295-251 Ma	Extinction of trilobites and most amphibians. The beginning of the development of reptiles and insects.	Volcanic activity. Hot climate.
The Mesozoic era includes 3 periods:
1. Triassic (Triassic)	251-200 Ma	Gymnosperm development. The first mammals and bony fishes.	Volcanic activity. Warm and sharply continental climate.
2. Jurassic (Jurassic)	200-145 Ma	The emergence of angiosperms. The spread of reptiles, the appearance of the first bird.	Mild and warm climate.
3. Cretaceous (chalk)	145-60 Ma	The appearance of birds, higher mammals.	Warm climate followed by cooling.
The Cenozoic era includes 3 periods:
1. Lower Tertiary (Paleogene)	65-23 Ma	The flowering of angiosperms. The development of insects, the appearance of lemurs and primates.	Mild climate with the allocation of climatic zones.
2. Upper Tertiary (Neogene)	23-1.8 Ma	The emergence of ancient people.	Dry climate.
3. Quaternary or anthropogen (human development)	1.8-0 Ma	The appearance of man.	Cooling.

The development of living organisms

The table of the development of life on Earth involves the division not only into time intervals, but also into certain stages of the formation of living organisms, possible climatic changes (ice age, global warming).

• Archean era. The most significant changes in the evolution of living organisms are the appearance of blue-green algae - prokaryotes capable of reproduction and photosynthesis, the emergence of multicellular organisms. The appearance of living protein substances (heterotrophs) capable of absorbing organic substances dissolved in water. In the future, the appearance of these living organisms made it possible to divide the world into flora and fauna.

• Mesozoic era.

• Triassic. Distribution of plants (gymnosperms). An increase in the number of reptiles. The first mammals, bony fish.
• Jurassic period. The predominance of gymnosperms, the emergence of angiosperms. The appearance of the first bird, the flowering of cephalopods.
• Cretaceous period. Spread of angiosperms, reduction of other plant species. The development of bony fish, mammals and birds.

• Cenozoic era.
  • Lower Tertiary period (Paleogene). The flowering of angiosperms. The development of insects and mammals, the appearance of lemurs, later primates.
  • Upper Tertiary period (Neogene). The development of modern plants. The appearance of human ancestors.
  • Quaternary period (anthropogen). Formation of modern plants, animals. The appearance of man.

Development of conditions of inanimate nature, climate change

The table of the development of life on Earth cannot be presented without data on changes in inanimate nature. The emergence and development of life on Earth, new species of plants and animals, all this is accompanied by changes in inanimate nature and climate.

Climate Change: Archean Era

The history of the development of life on Earth began through the stage of the predominance of land over water resources. The relief was poorly outlined. The atmosphere is dominated by carbon dioxide, the amount of oxygen is minimal. Salinity is low in shallow water.

The Archean era is characterized by volcanic eruptions, lightning, black clouds. The rocks are rich in graphite.

Climatic changes during the Proterozoic era

Land is a stone desert, all living organisms live in water. Oxygen accumulates in the atmosphere.

Climate change: the Paleozoic era

During various periods of the Paleozoic era, the following occurred:

• Cambrian period. The land is still deserted. The climate is hot.
• Ordovician period. The most significant changes are the flooding of almost all northern platforms.
• Silurian. Tectonic changes, the conditions of inanimate nature are diverse. Mountain building occurs, the seas prevail over the land. Regions of different climates, including areas of cooling, were determined.
• Devonian. Dry climate prevails, continental. Formation of intermountain depressions.
• Carboniferous period. The sinking of the continents, wetlands. The climate is warm and humid, with a lot of oxygen and carbon dioxide in the atmosphere.
• Permian period. Hot climate, volcanic activity, mountain building, drying up of swamps.

In the Paleozoic era, mountains formed. Such changes in the relief affected the world's oceans - the sea basins were reduced, a significant land area was formed.

The Paleozoic era marked the beginning of almost all major deposits of oil and coal.

Climatic changes in the Mesozoic

The climate of different periods of the Mesozoic is characterized by the following features:

• Triassic. Volcanic activity, the climate is sharply continental, warm.
• Jurassic period. Mild and warm climate. The seas prevail over the land.
• Cretaceous period. Retreat of the seas from the land. The climate is warm, but at the end of the period, global warming is replaced by cooling.

In the Mesozoic era, the previously formed mountain systems are destroyed, the plains go under water (Western Siberia). In the second half of the era, the Cordilleras, the mountains of Eastern Siberia, Indochina, partly Tibet, formed the mountains of the Mesozoic folding. A hot and humid climate prevails, contributing to the formation of swamps and peat bogs.

Climate change - Cenozoic era

In the Cenozoic era, there was a general uplift of the Earth's surface. The climate has changed. Numerous glaciations of the earth covers advancing from the north have changed the appearance of the continents of the Northern Hemisphere. Due to such changes, hilly plains were formed.

• Lower Tertiary period. Mild climate. Division into 3 climatic zones. Formation of continents.
• Upper Tertiary period. Dry climate. The emergence of steppes, savannahs.
• Quaternary period. Multiple glaciation of the northern hemisphere. Climate cooling.

All changes during the development of life on Earth can be written in the form of a table that will reflect the most significant stages in the formation and development of the modern world. Despite the already known research methods, even now scientists continue to study history, make new discoveries that allow modern society to find out how life developed on Earth before the appearance of man.

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 after a billion years did the first creatures come 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 of development was the formation of the brain, conditioned and unconditioned reflexes, survival instincts. The further evolution of animals provided the basis for the formation of mankind.

The division of the history of the Earth into eras and periods gives an idea of ​​the features of the development of life on the planet in different time periods. Scientists identify particularly 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 only began 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 origin 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 the Earth's satellite - the Moon. This event became significant in the development of life, stabilized the axis of rotation of the planet, contributed to the purification of water structures. As a result, the first life originated in 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. Remains of unicellular algae, mollusks, annelids were found. Soil is starting to form.

The air at the beginning of the era was not yet saturated with oxygen, but in the process of life, the bacteria that inhabit the seas began to release more and 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 types of plants and animals. The oceans were inhabited by algae, arthropods, mollusks, and the first chordates (Haikouihthys) appeared. The land remained uninhabited. The temperature remained high.

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

Silurian(442 - 418 million years ago). Plants come to land, and rudiments of lung tissue form in arthropods. The formation of the bone skeleton in vertebrates is completed, sensory organs appear. Mountain building is underway, 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 water bodies, amphibians began to land on land, new organisms are formed - insects.

Carboniferous period(353 - 290 million years ago). The appearance of amphibians, the sinking of the continents, 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 resistant 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 division of land into continents.

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

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

The Cenozoic era consists of three periods:

Lower Tertiary period 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 and air. The emergence of Australopithecus - the first ancestors of humans. During this period, the Alps, the Himalayas, the Andes were formed.

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

Archean the era, or archaean, is the oldest era in the geological history of the Earth with a duration of about 1 billion years, the era of the formation of the earth's crust, the appearance of the first water on it, the time of accumulation of the first powerful strata of sedimentary rocks.

All rocks of the Archean group are intensively dislocated, intruded by numerous granite intrusions. The Archean group of rocks is characterized mainly by gneisses, strongly metamorphosed by various crystalline schist quartzites. Archean rocks are characterized by considerable density and strength. In an unweathered state, they are usually an excellent foundation for all kinds of structures.

Proterozoic era, or Proterozoic, - the second era from the beginning of the geological history of the Earth; its duration is 600-800 million years. This era was characterized by a warm tropical climate, an extensive distribution of the sea, where limestone accumulated over vast areas.

Most of the Proterozoic rocks are typical sedimentary sequences, more or less metamorphosed (metamorphic schists, phyllites, quartzites, conglomerates, marbles).

Paleozoic era, or Paleozoic, is the third era from the beginning of the geological history of the Earth, lasting 300-350 million years. This era is divided into periods: 1) Cambrian, or Cambrian (Є); 2) Ordovician, or Ordovician (O); 3) Silurian, or Silurian (S); 4) Devonian, or Devonian (D); 5) coal, or carbon (C); 6) Permian, or Permian (P).

In the Paleozoic time, two powerful foldings appeared: the Caledonian (Ordovician and Silurian) and the Hercynian (Middle and Upper Carboniferous and Lower Permian times). Correspondingly, within the limits of the Paleozoic era, phases of tectonic rest also appeared, characterized by the low standing of continental masses and marine transgressions.

The rocks of the Paleozoic time are distinguished by great diversity both in composition and degree of metamorphization, and in the conditions of occurrence. A variety of limestones, marls and dolomites (marine facies) are widely distributed.

Within the continental platform, Paleozoic rocks are represented (depending on the facies) by various clays, sands, and loose sandstones.

Mesozoic era, or Mesozoic, is the fourth era from the beginning of the geological history of the Earth, which includes three periods: 1) Triassic, or Triassic (T); 2) Jurassic, or Jura (J); 3) chalk, or chalk (K).

The Mesozoic era was an era of relative tectonic calm. In the Jurassic period, Cimmerian folding manifested itself. As a result, the Jurassic is characterized mainly by a continental setting and the accumulation of sediments of the continental facies (coals) and the shallow sea (black or dark gray clays). Nevertheless, the Mesozoic era was characterized by a warm, uniform climate. Among the Mesozoic sediments, marine and continental sediments are distributed approximately equally. Among marine sediments, argillaceous shales are of the greatest importance; characterized by a variety of limestones and marls, less - sandstone conglomerates. The third period of this era is characterized by writing chalk as a manifestation of the intense transgression of the Cretaceous time, as a result of which vast water basins were formed within the continental masses.

Among the rocks of the continental facies, sandstones, shales, lacustrine marls, and even argillaceous limestones predominate.

Cenozoic the era, or Cenozoic, is the fifth from the beginning of the Earth and the late geological era, subdivided into the Paleogene, Neogene and Quaternary periods. In this era, the so-called Alpine folding was extremely intense, with which the history of the birth of the Alps, the Caucasian mountain ranges, the Crimea, the Himalayas and other mountain systems is associated.

The first half of the Cenozoic era (Paleogene) was distinguished by a very warm, almost tropical climate. In the future, as the Alpine orogenic phase develops, the climate worsens. The climate of the Neogene is characterized by a pronounced cooling. During this period, the harbingers of the coming powerful glaciation appeared.