According to modern concepts, it has an age of 4.5 - 5 billion years. In the history of its occurrence, 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, the land was submerged under water (the advance of the sea), the retreat of the sea, glaciation, the appearance and disappearance of various species of animals and plants, etc.

Scientists, trying to restore the history of the planet, study the layers of rocks. They divide all deposits into 5 groups, distinguishing the following eras: Archean (ancient), Proterozoic (early), Paleozoic (ancient), Mesozoic (middle) and Cenozoic (new). The boundary between 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 numbers.

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

Archean era was distinguished 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 certain areas of land with an almost continuous shield, they contain a lot of iron, gold, silver, platinum and ores of other metals.

AT Proterozoic era Volcanic activity was also high, and mountains of the so-called Baikal folding formed. They have practically not been preserved and now represent only separate small uplifts on the plains. During this period, the planet was inhabited by blue-green algae and protozoa, and the first multicellular organisms arose. Proterozoic rock layers are rich in minerals: iron ores and non-ferrous metal ores, mica.

At the beginning Paleozoic era formed the mountains Caledonian folding, which led to a reduction in sea basins and the emergence of significant land areas. In the form of mountains, only individual ranges of the Urals, Arabia, Southeast China and Central Europe have been preserved. All these mountains are low, "worn out". In the second half of the Paleozoic, mountains of Hercynian folding formed. This era of mountain building was more powerful, vast mountain ranges arose on the territory of Western Siberia and the Urals, Mongolia and Manchuria, most of Central Europe, the eastern 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 predominate among the vegetation. The main deposits of oil and coal appeared during this period.

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

Cenozoic era continues 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 the continent of Eurasia acquired its modern outlines. In addition, there was a rejuvenation of the ancient mountain ranges of the Urals, Appalachians, Tien Shan, Altai. The climate on the planet has changed dramatically, a period of powerful glaciation has begun. Ice sheets advancing from the north have changed the relief 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 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 for preparing for the exam

1. Explain why polar days and nights are observed on Earth.
2. What would be the conditions on the Earth if the axis of its rotation was not inclined to the plane of the orbit?
3. The change of seasons on Earth is determined by two main reasons: the first is the revolution of the Earth around the Sun; name the second one.
4. How many times a year and when is the Sun at its zenith above the equator? Over the Tropic of the North? Over the Southern Tropic?
5. In what 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 characterizes the days of the spring and autumn equinoxes on Earth? When do they advance in the Northern and Southern Hemispheres?
8. When are 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

Geological scale

Eras (duration - in million years)	Periods (duration in million years)	The most important 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 uplift. Repeated ice sheets, especially in the Northern Hemisphere. The appearance of man	Peat, alluvial deposits of gold, diamonds, dredges, stones
	Neogene 25 Ma (N)	The emergence of young mountains in areas of alpine folding. Rejuvenation of mountains in the regions of all ancient foldings. dominance of flowering plants	Brown coals, oil, amber
	Paleogene 41 Ma (P)	Destruction of mountains of Mesozoic folding. Wide development of flowering plants, birds and mammals	Phosphorites, brown coals, bauxites

Mesozoic 165 Ma	Cretaceous 70 Ma (K)	The emergence of young mountains in the 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 rise of giant reptiles (dinosaurs). dominance of gymnosperms	Coals, oil, phosphorites
	Triassic 40 Ma (T)	The greatest retreat of the sea and the rise of land in the history of the Earth. Destruction of the mountains of the Caledonian and Hercynian foldings. Vast deserts. First mammals	rock salts
1	2	3	4
Paleozoic 330 Ma	Permian 45 Ma (P)	The emergence of young folded mountains in areas of Hercynian folding. Dry climate over most of the land. The emergence of gymnosperms	Rock and potash salts, gypsum
	Carboniferous 65 Ma (C)	Hot and humid climate over most of the land. Widespread swampy lowlands in coastal areas. Forests of tree ferns. The first reptiles, the heyday of amphibians	Coal, oil
	Devonian 55 Ma (p)	Hot climate over most of the land. First deserts. The appearance of amphibians. Numerous fish	Salt, oil
	Silurian 35 Ma (S)	The emergence of young folded mountains in the areas of the Caledonian folding. The first land plants (mosses and ferns)

	Ordovician 60 Ma (O)	Decrease in the area of ​​marine 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 the seas. The rise of marine invertebrates	Rock salt, gypsum, phosphate rock
Proterozoic era 600 Ma		Beginning of the Baikal folding. Powerful volcanism. Development of bacteria and blue-green algae	Iron ores, mica, graphite
Archean era 900 Ma		Formation of the continental crust. Intense volcanic activity. Time of primitive unicellular bacteria	ores

Maksakovskiy V.P., Petrova N.N., Physical and economic geography of the world. - M.: Iris-press, 2010. - 368 pp.: ill.

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Archean era. The beginning of this ancient era is considered not the moment of the formation of the Earth, but the time after the formation of the solid earth's crust, when mountains and rocks already existed and the processes of erosion and sedimentation came into play. The duration of this era is approximately 2 billion years, i.e., it corresponds to all other eras taken together. The Archean era seems to have been characterized by catastrophic and widespread volcanic activity, as well as deep uplifts culminating in the formation of mountains. The high temperature, pressure and mass movements that accompanied these movements apparently destroyed most of the fossils, but some data about the life of those times still survived. In the Archeozoic rocks, graphite or pure carbon is found everywhere in scattered form, which probably represent altered remains of animals and plants. If we accept that the amount of graphite in these rocks reflects the amount of living matter (and this, apparently, is true), then in the Archaean this living matter probably existed very much, since there is more carbon in the rocks of this age than in coal seams of the Appalachian Basin.

Proterozoic era. The second era, lasting about 1 billion years, was characterized by the deposition of a large amount of precipitation and at least one significant glaciation, during which ice sheets extended to latitudes less than 20 ° from the equator. A very small number of fossils were found in the Proterozoic rocks, which, however, testify not only to the existence of life in this era, but also to the fact that evolutionary development advanced far ahead by the end of the Proterozoic. Spicules of sponges, remains of jellyfish, fungi, algae, brachiopods, arthropods, etc. have been found in Proterozoic deposits.

Palaeozoic. Between the deposits of the Upper Proterozoic and the initial layers of the third, Paleozoic era, there is a significant break caused by mountain building movements. For 370 million years of the Paleozoic era, representatives of all types and classes of animals appeared, with the exception of birds and mammals. Since different species of animals existed only for certain periods of time, their fossils allow geologists to compare deposits of the same age found in different places.

• Cambrian period [show] .

  Cambrian period- the most ancient department of the Paleozoic era; It is represented by rocks abounding in fossils, so that the appearance of the Earth at this time can be reconstructed with sufficient accuracy. The forms that lived during this period were so diverse and complex that they must have descended from ancestors that existed at least in the Proterozoic, and possibly in the Archaean.

  All modern types of animals, with the exception of chordates, already existed and all plants and animals lived in the sea (the continents, apparently, were lifeless deserts until the late Ordovician or Silurian, when plants moved to land). There were primitive, shrimp-like crustaceans and forms resembling arachnids; some of their descendants have survived, almost unchanged, to the present day (horse crabs). The seabed was covered with solitary sponges, corals, stalked echinoderms, gastropods and bivalves, primitive cephalopods, brachiopods and trilobites.

  Brachiopods - sessile animals with a bivalve shell and feeding on plankton, flourished in the Cambrian and in all other systems of the Paleozoic.

  Trilobites are primitive arthropods with an elongated flat body, covered on the dorsal side with a hard shell. Two grooves stretch along the shell, dividing the body into three parts, or lobes. Each body segment, with the exception of the very last, bears a pair of biramous limbs; one of them served for walking or swimming and it had a gill. Most trilobites were 5-7.5 cm long, but some reached 60 cm.

  In the Cambrian, both unicellular and multicellular algae existed. One of the best preserved collections of Cambrian fossils was collected in the mountains of British Columbia. It includes worms, crustaceans, and a transitional form between worms and arthropods, similar to the living peripatus.

  After the Cambrian, evolution was mainly characterized not by the emergence of completely new types of structure, but by the branching of already existing lines of development and the replacement of the original primitive forms by more highly organized ones. It is probable that pre-existing forms have reached such a degree of adaptability to the environment that they have acquired a significant preponderance over any new, unadapted types.

• Ordovician period [show] .

  During the Cambrian period, the continents began to gradually sink into the water, and in the Ordovician period this sinking reached its maximum, so that a significant part of the current land was covered with shallow seas. Huge cephalopods lived in these seas - animals similar to squid and nautilus - with a straight shell from 4.5 to 6 m long and 30 cm in diameter.

  The Ordovician seas must have been very warm, as warm-water corals spread as far as Lake Ontario and Greenland at this time.

  The first remains of vertebrates were found in the Ordovician deposits. These small animals, called corymbs, were bottom forms, devoid of jaws and paired fins (Fig. 1.). Their carapace consisted of heavy bony plates on the head and thick scales on the body and tail. Otherwise, they were similar to modern lampreys. They apparently lived in fresh water, and their shell served to protect against giant predatory water scorpions called eurypterids, which also lived in fresh water.

• Silurian [show] .

  The Silurian period saw two events of great biological significance: the development of land plants and the appearance of air-breathing animals.

  The first land plants seem to have been more like ferns than mosses; ferns were the dominant plants also in the subsequent Devonian and lower Carboniferous.

  The first air-breathing land animals were arachnids, somewhat reminiscent of modern scorpions.

  The continents that had been low during the Cambrian and Ordovician times rose, especially in Scotland and northeastern North America, and the climate became much cooler.

• Devonian [show] .

  

  

  

  During the Devonian, the first armored fishes gave rise to many different fishes, so that this period is often called the "time of the fishes."

  Jaws and paired fins first developed in armored sharks (Placodermi), which were small, shelled freshwater forms. These animals were characterized by a variable number of paired fins. Some had two pairs of fins, corresponding to the fore and hind limbs of higher animals, while others had up to five pairs of additional fins between these two pairs.

  During the Devonian, real sharks appeared in fresh waters, which showed a tendency to migrate to the ocean and to lose their bulky bone carapace.

  The ancestors of bony fishes also originated in Devonian freshwater streams; by the middle of this period, they had a division into three main types: lungfish, lobe-finned and ray-finned. All these fish had lungs and a shell of bony scales. Only a very few lungfish have survived to this day, and the ray-finned, having gone through a period of slow evolution throughout the remainder of the Paleozoic era and the beginning of the Mesozoic, later, in the Mesozoic, experienced significant divergence and gave rise to modern bony fish (Teleostei).

  The lobe-finned fish, which were the ancestors of terrestrial vertebrates, almost died out by the end of the Paleozoic and, as previously believed, disappeared completely at the end of the Mesozoic. However, in 1939 and 1952 off the east coast of South Africa, live representatives of the lobe-finned about 1.5 m long were caught.

  The upper part of the Devonian was marked by the appearance of the first terrestrial vertebrates - amphibians called stegocephali (meaning "covered heads"). These animals, whose skulls were covered with a bony shell, are in many respects similar to lobe-finned fish, differing from them mainly in the presence of limbs, and not fins.

  The Devonian is the first period that is characterized by true forests. During this period, ferns, club mosses, ferns and primitive gymnosperms flourished - the so-called "seed ferns". It is believed that insects and centipedes arose in the Late Devonian.

• Carboniferous period [show] .

  At this time, large swampy forests were widespread, the remains of which gave rise to the main coal deposits of the world. The continents were covered with low-lying swamps overgrown with ferns, common ferns, seed ferns and broad-leaved evergreens.

  

  

  The first reptiles, called whole-skull and similar to the amphibians that preceded them, appeared in the second half of the Carboniferous period, flourished in the Permian - the last period of the Paleozoic - and died out at the beginning of the Mesozoic era. It is not clear what the most primitive of the reptiles known to us Seymouria (named after the city in Texas near which its fossils were found) was - an amphibian, ready to turn into a reptile, or a reptile that had just crossed the border separating it from amphibians .

  One of the main differences between amphibians and reptiles is the structure of the eggs they lay. Amphibians lay their eggs, covered with a gelatinous membrane, in the water, and reptiles lay their eggs, covered with a strong shell, on the ground. Since the eggs of Seymouria have not been preserved, we may never be able to decide which class this animal should be placed in.

  Seymouria was a large slow lizard-like form. Its short, stump-like legs extended horizontally away from the body, like a salamander's, instead of squeezing closer and going straight down to form column-like supports for the body.

  During the Carboniferous period, two important groups of winged insects appeared - the ancestors of cockroaches, which reached 10 cm in length, and the ancestors of dragonflies, some of which had a wingspan of 75 cm.

• Permian period [show] .

  

  

  The last period of the Paleozoic was characterized by major changes in climate and topography. Continents have risen all over the globe, so that the shallow seas that covered the region from Nebraska to Texas have dried up, leaving behind a salty desert. At the end of the Permian, widespread folding, known as the Hercynian orogeny, took place, during which a large mountain range from Nova Scotia to Alabama was uplifted. This range was originally higher than the modern Rocky Mountains. At the same time, other mountain ranges were forming in Europe.

  Enormous ice sheets extending from the Antarctic covered most of the southern hemisphere, extending into Africa and Brazil almost to the equator.

  North America was one of the few areas that did not undergo glaciation at this time, but even here the climate became much colder and drier than it had been during most of the Paleozoic era. Many Paleozoic organisms, apparently, could not adapt to climate change and died out during the Hercynian orogeny. Due to the cooling of water and the reduction of space suitable for life, as a result of the drying up of shallow seas, even many marine forms have become extinct.

  From the primitive whole-cranial during the Late Carboniferous and Early Permian, that group of reptiles developed from which mammals are believed to have descended in a straight line. These were pelycosaurs - predatory reptiles with a more slender and lizard-like body than those of whole-skull.

  In the late Permian, another group of reptiles, the therapsids, probably developed from pelycosaurs, possessing several other mammalian features. One of the representatives of this group - Cynognathus (reptile with a "dog jaw") was a slender, light animal about 1.5 m long, with a skull intermediate in character between that of a reptile and a mammal. Its teeth, instead of being conical and identical, as is characteristic of reptiles, differentiated into incisors, canines and molars. Since we have no information about the soft parts of the animal, whether it was covered with scales or hair, whether it was warm-blooded or cold-blooded, and whether it suckled its young, we call it reptile. However, if we had more complete data, it might have to be considered a very early mammal. Therapsids, widespread in the late Permian, were replaced by many other reptiles at the beginning of the Mesozoic.

Mesozoic era (time of reptiles). The Mesozoic era, which began about 230 million years ago and lasted about 167 million years, is divided into three periods:

1. Triassic
2. Jurassic
3. chalky

During the Triassic and Jurassic periods, most of the continental regions were raised above sea level. In the Triassic, the climate was dry, but warmer than in the Permian, and in the Jurassic, it was warmer and more humid than in the Triassic. The trees of the famous Stone Forest in Arizona have been around since the Triassic period.

During the Cretaceous period, the Gulf of Mexico, expanding, flooded Texas and New Mexico, and in general the sea gradually moved towards the continents. In addition, vast swamps have developed in the area stretching from Colorado to British Columbia. At the end of the Cretaceous period, the interior of the North American continent experienced further subsidence, so that the waters of the Gulf of Mexico basin joined with the waters of the Arctic basin and divided this continent into two parts. The Cretaceous ended with a great uplift called the Alpine orogeny, during which the Rocky Mountains, the Alps, the Himalayas, and the Andes arose, and which caused volcanic activity in western North America.

The evolution of reptiles . The emergence, differentiation and finally extinction of a great number of reptiles belonging to the six main branches are the most characteristic feature of the Mesozoic era. [show] .

The most primitive branch includes, in addition to the ancient whole-skull, turtles that arose in Perm. Turtles have developed the most complex (among land animals) shell; it consists of plates of epidermal origin, fused with the underlying ribs and breastbone. With this protective device, both sea turtles and tortoises survived from pre-dinosaur times with only a few structural changes. The legs of turtles, which extend from the body in a horizontal direction, which makes it difficult and slow to move, and their skulls, which do not have holes behind the eye sockets, were inherited unchanged from the ancient whole-cranial ones.

The second group of reptiles, coming with relatively few changes from the ancestral whole-skull, are lizards, the most numerous among living reptiles, as well as snakes. Lizards have for the most part retained a primitive type of movement with horizontally diverging legs, although many of them can run quickly. In most cases, they are small, but the Indian monitor reaches 3.6 m in length, and some fossil forms are 7.5 m long. Cretaceous mosasaurs were sea lizards that reached 12 m in length; they had a long tail used for swimming.

During the Cretaceous period, snakes evolved from lizard ancestors. The essential difference between snakes and lizards is not the loss of legs (some lizards also lack legs), but certain changes in the structure of the skull and jaws that allow snakes to open their mouths wide enough to swallow animals larger than themselves.

The representative of the ancient branch, somehow managed to survive to this day in New Zealand, is the tuatara (Shpenodon punctatum). It shares several features with its cotylosaur ancestors; one such feature is the presence of a third eye at the top of the skull.

The main group of Mesozoic reptiles were the archosaurs, the only living representatives of which are alligators and crocodiles. At some early point in their evolution, archosaurs, then 1.5 meters long, adapted to walking on two legs. Their front legs shortened, while their hind legs lengthened, strengthened and greatly changed their shape. These animals rested and walked on all four legs, but in critical circumstances they reared up and ran on two hind legs, using their rather long tail as a balance.

Many different specialized forms evolved from early archosaurs, some of which continued to walk on two legs while others returned to walking on all fours. These descendants include phytosaurs - aquatic, alligator-like reptiles common in the Triassic; crocodiles, which formed in the Jurassic and replaced phytosaurs as aquatic forms, and finally pterosaurs, or flying reptiles, which included animals the size of robins, as well as the largest animal ever flying, Pteranodon, with a wingspan of 8 m

There were two types of flying reptiles; some had a long tail, equipped with a tail blade at the end, others had a short tail. Representatives of both types, apparently, fed on fish and probably flew long distances over water in search of food. Their legs were not adapted for standing, and therefore it is assumed that they, like bats, rested in a suspended state, clinging to some kind of support.

Of all the branches of reptiles, dinosaurs are the most famous, which means "terrible lizards" in translation. They were divided into two main types: ornithischians and lizards.

Saurischia (lizards) first appeared in the Triassic and continued to exist until the Cretaceous. The early lizards were fast, predatory, rooster-sized, bipedal forms that probably preyed on lizards and primitive mammals that had already appeared. During the Jurassic and Cretaceous, this group showed an increasing trend in size, culminating in the giant Cretaceous predator Tyrannosaurus Rex. Other Saurischia, which appeared in the late Triassic, switched to plant foods, again began to walk on four legs, and during the Jurassic and Cretaceous gave rise to a number of giant forms that led an amphibious lifestyle. These largest four-legged animals that have ever lived include brontosaurs up to 20 m long, diplodocus, which reached a length of over 25 m, and brachiosaurus, the largest of all, whose weight is estimated at 50 tons.

Another group of dinosaurs, the Ornitischia (Ornithischians), were herbivores, probably from the very beginning of their evolution. Although some of them walked on their hind legs, most moved on all four legs. Instead of missing front teeth, they developed a strong horny sheath, similar to a bird's beak, which in some forms was wide and flat, like ducks (hence the name "duck-billed" dinosaurs). This type is characterized by webbed feet. Other species developed large armored plates that protected them from predatory lizards. The ankylosaurus, which is called the "reptile tank", had a wide flat body covered with bone plates and large spikes protruding from the sides.

Finally, some Cretaceous ornithischians developed bony plates around their heads and necks. One of them, Triceratops, had two horns above the eyes and a third above the nasal region - all up to almost 1 m long.

Two other groups of Mesozoic reptiles that differ both from each other and from dinosaurs are marine plesiosaurs and ichthyosaurs. The first were characterized by an extremely long neck, which was more than half the length of the animal. Their body was wide, flat, resembling the body of a turtle, and their tail was short. Plesiosaurs swam with flipper-like limbs. Often they reached 13-14 m in length.

Ichthyosaurs (lizard fish) were similar in appearance to fish or whales, with a short neck, a large dorsal fin, and a shark-type tail. They swam with swift tail movements, using their limbs only as controls. It is believed that ichthyosaur cubs were born alive, hatching from an egg in the mother's body, since adults were too specialized and could not go to land to lay eggs, and reptile eggs drown in water. The finding of juvenile skeletons inside the abdominal cavity of adult fossils supports this theory.

At the end of the Cretaceous, many reptiles died out. They obviously could not adapt to the significant changes in environmental conditions caused by the Alpine orogeny. As the climate became colder and drier, many plants that served as food for herbivorous reptiles disappeared. Some herbivorous reptiles were too bulky to move on land when the swamps dried up. The smaller, warm-blooded mammals that had already appeared had an advantage in the competition for food, and many of them even fed on reptile eggs. The extinction of many reptiles was probably the result of the combined action of a number of factors or any one factor.

Other directions of evolution in the Mesozoic . Although reptiles were the dominant animals in the Mesozoic, many other important organisms also developed at this time. [show] .

In the Mesozoic, the number and diversity of gastropods and bivalves increased. Sea urchins have reached the highest point of their development.

In the Triassic, mammals arose, and in the Jurassic, bony fish and birds arose.

Most modern orders of insects appeared in the early Mesozoic.

During the early Triassic, seed ferns, cycads, and conifers were the most common plants, but by the Cretaceous, many other forms resembling modern species appeared - fig trees, magnolias, palm trees, maples and oaks.

From the Jurassic time, magnificent imprints of the most ancient species of birds have been preserved, on which even the outlines of feathers are visible. This creature, called Archeopteryx, was about the size of a crow and had rather weak wings, jaws armed with teeth, and a long reptilian tail covered with feathers.

Fossils of two other birds, Hesperornis and Ichthyornis, have been found in the Cretaceous deposits. The first is an aquatic diving bird that has lost the ability to fly, and the second is a strong flying bird with reptilian teeth, about the size of a dove.

Modern toothless birds formed at the beginning of the next era.

Cenozoic era (time of mammals). The Cenozoic era can justifiably be called the time of birds, the time of insects, or the time of flowering plants, since the development of all these organisms is no less characteristic of it than the development of mammals. It covers the period from the Alpine orogeny (about 63 million years ago) to the present day and is divided into two periods - the Tertiary, which lasted about 62 million years, and the Quaternary, which includes the last 1-1.5 million years.

• Tertiary period. This period is subdivided into five epochs: Paleocene, Eocene, Oligocene, Miocene and Pliocene. The rocky mountains formed at the beginning of the Tertiary period were already strongly eroded by the Oligocene, as a result of which the North American continent acquired a gently undulating relief.

  In the Miocene, another series of uplifts created the Sierra Nevada mountains and new ranges in the Rocky Mountains, which led to the formation of deserts in the west. The climate in the Oligocene was milder than at present, so that palm trees spread as far north as Wyoming.

  The uplift, which began in the Miocene, continued into the Pliocene and, combined with the glaciations of the Pleistocene time, led to the extinction of many pre-existing mammals and other animals. The final uplift of the Colorado Plateau, which created the Grand Canyon, almost ended in a short time of the Pleistocene and modern epochs.

  The oldest fossils of true mammals date back to the Late Triassic, and in the Jurassic, there were already four orders of mammals, all of which were the size of a rat or a small dog.

  The earliest mammals (monotrems) were oviparous animals, and their only representatives that have survived to this day are the platypus and the needle-covered echidna living in Australia. Both of these forms have a coat, and they feed their young with milk, but they also lay eggs, like turtles. The ancestral egg-laying mammals, of course, must have been different from the specialized platypus and echidna, but the fossil record of these ancient forms is incomplete. Living monotremes could only last so long because they lived in Australia, where until recently there were no placental mammals, so they had no one to compete with.

  In the Jurassic and Cretaceous, most mammals were already highly organized enough to produce live young, although in the most primitive of them - the marsupials - the young are born underdeveloped and must remain for several months in the pouch on the mother's abdomen, where the nipples are located. Australian marsupials, like monotremes, did not meet competition from more adapted placental mammals, while on other continents this competition led to the extinction of marsupials and monotremes; therefore, in Australia, marsupials, as a result of divergent development, gave rise to many different forms, outwardly resembling some placentals. There are marsupial mice, shrews, cats, moles, bears, and one kind of wolf, as well as a number of forms that have no placental parallels, such as kangaroos, wombats, and wallabies.

  During the Pleistocene, giant kangaroos and rhinoceros-sized wombats lived in Australia. Opossums are more similar to primitive ancestral marsupials than any of these more specialized forms; they are the only marsupials found outside of Australia and South America.

  Modern highly organized placental mammals, which include humans, characterized by the birth of live young capable of independent existence, descended from insectivorous arboreal ancestors. Fossils of this ancestral form, found in the Cretaceous deposits, show that it was a very small animal, like the living shrew. Some of these ancestral mammals retained an arboreal way of life and, through a series of intermediate forms, gave rise to primates - monkeys and humans. Others lived on the ground or underground, and during the Paleocene all other mammals living today are descended from them.

  Primitive Paleocene mammals had conical reptilian teeth, five-fingered limbs, and a small brain. Also, they were plantigrade, not digitigrade.

  During the Tertiary period, the evolution of herbaceous plants, which served as food, and forests, which sheltered animals, was the most important factor influencing the change in the structure of the body of mammals. Along with a tendency to increase in size, the development of all mammals showed a bias towards an increase in the relative size of the brain and changes in teeth and legs. When new, more adapted forms appeared, primitive mammals died out.

  Although fossil remains of both marsupials and placentals were found in the Cretaceous deposits, the discovery of highly developed mammals in the Early Tertiary deposits was rather unexpected. Whether they really arose at this time or whether they existed earlier in the highlands and simply did not survive as fossils is not known.

  In the Paleocene and Eocene, the first predators, called creodonts, originated from primitive insectivorous placentals. In the Eocene and Oligocene, they were replaced by more modern forms, which over time gave rise to living predators, such as cats, dogs, bears, weasels, as well as pinniped marine predators - seals and walruses.

  

  One of the best-known fossil predators is the saber-toothed tiger, which became extinct only recently, in the Pleistocene. It had extremely long and sharp upper fangs, and the lower jaw could swing down and to the side so that the fangs pierced the prey like sabers.

  Large herbivorous mammals, in most cases with hooves, are sometimes combined into one group called ungulates. However, they are not a single natural group, but consist of several independent branches, so that a cow and a horse, despite the fact that they both have hooves, are no more related to each other than each of them is to a tiger. The molars of ungulates are flattened and enlarged, which facilitates the grinding of leaves and grass. Their legs became long and adapted to the fast running necessary to escape from predators.

  The oldest ungulates, called Condylarthra, appeared in the Paleocene. They had a long body and a long tail, flat grinding molars, and short legs ending in five toes with a hoof on each. A group analogous to primitive predators - creodonts, were primitive ungulates called wintatheria. In the Paleocene and Eocene, some of them reached the size of an elephant, while others had three large horns extending from the top of the head.

  The paleontological record of several evolutionary lines of ungulates - horses, camels and elephants - is so complete that it is possible to trace the entire development of these animals from small primitive five-fingered forms. The main direction of evolution in ungulates was towards an increase in the overall size of the body and a decrease in the number of fingers. Ungulates early fell into two groups, one of which is characterized by an even number of fingers and includes cows, sheep, camels, deer, giraffe, pigs and hippos. Another group is characterized by an odd number of fingers and includes horses, zebras, tapirs and rhinos.

  The development of elephants and their recently extinct relatives - mammoths and mastodons - can be traced back centuries to the Eocene ancestor, which was the size of a pig and did not have a trunk. This primitive form, called Moeritherium, was close to the trunk, from which branched, in addition, such dissimilar forms as hyraxes (a small marmot-like animal found in Africa and Asia) and a sea cow.

  Whales and dolphins are descended from Eocene cetacean forms called zeiglodonts, and these latter in turn are believed to have descended from creodonts.

  The evolution of bats can be traced back to winged animals that lived in the Eocene and were descendants of primitive insectivores.

  The evolution of some other mammals - rodents, rabbits and edentulous (anteaters, sloths and armadillos) - is less well known.

• Quaternary period (human time). The Quaternary period, which covers the last 1-1.5 million years, is usually divided into two epochs - Pleistocene and modern. The latter began approximately 11,000 years ago, from the moment the last glacier retreated. The Pleistocene is characterized by four ice ages, separated by intervals when the glaciers retreated. At the time of maximum distribution, ice sheets occupied almost 10 million square meters in North America. km, extending south to the Ohio and Missouri rivers. The Great Lakes, which have been plowed by moving glaciers, have drastically changed their outlines many times and from time to time connected with the Mississippi. It has been estimated that in the past, when the Mississippi collected water from the lakes, to Duluth in the west and to Buffalo in the east, its discharge was more than 60 times its present day. During the Pleistocene glaciations, such an amount of water was removed from the sea and turned into ice that the sea level dropped by 60-90 m. England and the European mainland.

  Plants and animals of the Pleistocene era were similar to those of our time. It is sometimes difficult to distinguish Pleistocene deposits from Pliocene deposits as well, since the organisms they contain are similar both to each other and to modern forms. During the Pleistocene, after the appearance of primitive man, many mammals became extinct, including the saber-toothed tiger, the mammoth, and the giant ground sloth. The Pleistocene also saw the extinction of many plant species, especially forest species, and the appearance of numerous herbaceous forms.

  The fossil record leaves no doubt that living species evolved from pre-existing other species. This chronicle is not equally clear for all lines of evolution. Plant tissues are in most cases too soft to give good fossils, and the intermediate forms that serve as links between different types of animals were obviously forms without a skeleton, and no traces of them remain. For many evolutionary lines, in particular for vertebrates, successive stages of development are well known. Other lines have gaps that future paleontologists will have to fill.

The history of our planet still holds many mysteries. Scientists from various fields of natural science have contributed to the study of the development of life on Earth.

It is believed that the age of our planet is about 4.54 billion years. This entire time period is usually divided into two main stages: Phanerozoic and Precambrian. These stages are called eons or eonoteme. Eons, in turn, are divided into several periods, each of which is distinguished by a set of changes that have taken place in the geological, biological, atmospheric state of the planet.

1. Precambrian, or Cryptozoic- this is an eon (time interval of the development of the Earth), covering about 3.8 billion years. That is, the Precambrian is the development of the planet from the moment of formation, the formation of the earth's crust, the proto-ocean and the emergence of life on Earth. By the end of the Precambrian, highly organized organisms with a developed skeleton were already widespread on the planet.

The eon includes two more eonotemes - katarche and archaea. The latter, in turn, includes 4 eras.

1. Katarchaeus- this is the time of the formation of the Earth, but there was still neither the core nor the earth's crust. The planet was still a cold cosmic body. Scientists suggest that during this period there was already water on Earth. The Catarchean lasted about 600 million years.

2. Archaea covers a period of 1.5 billion years. During this period, there was no oxygen on Earth yet, deposits of sulfur, iron, graphite, and nickel were being formed. The hydrosphere and the atmosphere were a single vapor-gas shell that enveloped the globe in a dense cloud. The sun's rays practically did not penetrate through this veil, so darkness reigned on the planet. 2.1 2.1. Eoarchean- this is the first geological era, which lasted about 400 million years. The most important event of the Eoarchean is the formation of the hydrosphere. But there was still little water, the reservoirs existed separately from each other and did not yet merge into the world ocean. At the same time, the earth's crust becomes solid, although asteroids are still bombarding the Earth. At the end of the Eoarchean, the first supercontinent in the history of the planet, Vaalbara, is formed.

2.2 Paleoarchaean- the next era, which also lasted approximately 400 million years. During this period, the core of the Earth is formed, the magnetic field strength increases. A day on the planet lasted only 15 hours. But the oxygen content in the atmosphere increases due to the activity of bacteria that have appeared. The remains of these first forms of the Paleoarchean era of life have been found in Western Australia.

2.3 Mesoarchean also lasted about 400 million years. In the Mesoarchean era, our planet was covered by a shallow ocean. Land areas were small volcanic islands. But already during this period, the formation of the lithosphere begins and the mechanism of plate tectonics starts. At the end of the Mesoarchean, the first ice age occurs, during which snow and ice form for the first time on Earth. Biological species are still represented by bacteria and microbial life forms.

2.4 Neoarchean- the final era of the Archean eon, the duration of which is about 300 million years. Colonies of bacteria at this time form the first stromatolites (limestone deposits) on Earth. The most important event of the Neoarchean is the formation of oxygen photosynthesis.

II. Proterozoic- one of the longest time periods in the history of the Earth, which is usually divided into three eras. During the Proterozoic, the ozone layer first appears, the world ocean reaches almost its present volume. And after the longest Huron glaciation, the first multicellular life forms appeared on Earth - mushrooms and sponges. The Proterozoic is usually divided into three eras, each of which contained several periods.

3.1 Paleo-Proterozoic- the first era of the Proterozoic, which began 2.5 billion years ago. At this time, the lithosphere is fully formed. But the former forms of life, due to the increase in oxygen content, practically died out. This period is called the oxygen catastrophe. By the end of the era, the first eukaryotes appear on Earth.

3.2 Mesoproterozoic lasted approximately 600 million years. The most important events of this era: the formation of continental masses, the formation of the supercontinent Rodinia and the evolution of sexual reproduction.

3.3 Neo-proterozoic. During this era, Rodinia breaks up into about 8 parts, the super-ocean of Mirovia ceases to exist, and at the end of the era, the Earth is covered with ice almost to the equator. In the Neoproterozoic era, living organisms for the first time begin to acquire a hard shell, which will later serve as the basis of the skeleton.

III. Paleozoic- the first era of the Phanerozoic eon, which began approximately 541 million years ago and lasted about 289 million years. This is the era of the emergence of ancient life. The supercontinent Gondwana unites the southern continents, a little later the rest of the land joins it and Pangea appears. Climatic zones begin to form, and flora and fauna are represented mainly by marine species. Only towards the end of the Paleozoic does the development of land begin, and the first vertebrates appear.

The Paleozoic era is conditionally divided into 6 periods.

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

2. Ordovician period- the second period of the Paleozoic, which lasted 42 million years. This is the era of the formation of sedimentary rocks, phosphorites and oil shale. The organic world of the Ordovician is represented by marine invertebrates and blue-green algae.

3. Silurian period covers the next 24 million years. At this time, almost 60% of living organisms that existed before die out. But the first cartilaginous and bone fish in the history of the planet appear. On land, the Silurian is marked by the appearance of vascular plants. Supercontinents converge and form Laurasia. By the end of the period, ice melting was noted, the sea level rose, and the climate became milder.

4 Devonian is characterized by the rapid development of various forms of life and the development of new ecological niches. Devon covers a time interval of 60 million years. The first terrestrial vertebrates, spiders, and insects appear. Land animals develop lungs. Although fish still dominate. The kingdom of flora of this period is represented by ferns, horsetails, club mosses and gosperms.

5. Carboniferous period often referred to as carbon. At this time, Laurasia collides with Gondwana and the new supercontinent Pangea appears. A new ocean is also formed - Tethys. This is the time when the first amphibians and reptiles appeared.

6. Permian period- the last period of the Paleozoic, which ended 252 million years ago. It is believed that at this time a large asteroid fell to Earth, which led to significant climate change and the extinction of almost 90% of all living organisms. Most of the land is covered with sand, the most extensive deserts appear that have only existed in the entire history of the Earth's development.

IV. Mesozoic- the second era of the Phanerozoic eon, which lasted almost 186 million years. At this time, the continents acquire almost modern outlines. A warm climate contributes to the rapid development of life on Earth. Giant ferns disappear, and angiosperms appear to replace them. The Mesozoic is the era of dinosaurs and the appearance of the first mammals.

The Mesozoic era is divided into three periods: Triassic, Jurassic and Cretaceous.

1. Triassic period lasted a little over 50 million years. At this time, Pangea begins to split, and the inland seas gradually become smaller and dry up. The climate is mild, the zones are not pronounced. Nearly half of land plants are disappearing as deserts spread. And in the realm of fauna, the first warm-blooded and terrestrial reptiles appear, which became the ancestors of dinosaurs and birds.

2 Jurassic covers a gap of 56 million years. A humid and warm climate reigned on Earth. The land is covered with thickets of ferns, pines, palms, cypresses. Dinosaurs reign on the planet, and numerous mammals have so far been distinguished by their small stature and thick hair.

3 Cretaceous- the longest period of the Mesozoic, lasting almost 79 million years. The split of the continents is practically coming to an end, the Atlantic Ocean is significantly increasing in volume, and ice sheets are forming at the poles. An increase in the water mass of the oceans leads to the formation of a greenhouse effect. At the end of the Cretaceous, a catastrophe occurs, the causes of which are still not clear. As a result, all dinosaurs and most species of reptiles and gymnosperms became extinct.

V. Cenozoic- this is the era of animals and Homo sapiens, which began 66 million years ago. The continents at this time acquired their modern shape, Antarctica occupied the south pole of the Earth, and the oceans continued to grow. Plants and animals that survived the catastrophe of the Cretaceous period found themselves in a completely new world. Unique communities of lifeforms began to form on each continent.

The Cenozoic era is divided into three periods: Paleogene, Neogene and Quaternary.

1. Paleogene period ended approximately 23 million years ago. At that time, a tropical climate reigned on Earth, Europe was hiding under evergreen tropical forests, and deciduous trees grew only in the north of the continents. It was during the Paleogene period that the rapid development of mammals takes place.

2. Neogene period covers the next 20 million years of the planet's development. Whales and bats appear. And, although saber-toothed tigers and mastodons still roam the earth, the fauna is increasingly acquiring modern features.

3. Quaternary period began more than 2.5 million years ago and continues to this day. Two major events characterize this time period: the Ice Age and the advent of man. The Ice Age completely completed the formation of the climate, flora and fauna of the continents. And the appearance of man marked the beginning of civilization.

The thesis about the evolution of the Earth, as an exceptional object of its kind in the cosmos, occupies the main step. In view of this, geological time becomes a special numerical-evolutionary characteristic. The comprehension of this time is engaged in science, which bears the definition of Geochronology, that is, the geological account of time. The above specialized science is divided into two types: absolute geochronology and relative geochronology.

Absolute geochronology carries out activities to determine the absolute age of rocks. This age is transmitted in units of time, namely, in millions of years.

The key link in establishing this age is the rate of decay of isotopes of radioactive components. This speed is extremely constant and is free from the saturation of physical and chemical currents. Age notation is organized in ways that are related to nuclear physics. Minerals that have radioactive components in their composition give rise to a closed structure when arranging crystal lattices. It is in such a structure that the process of accumulation of elements of radioactive decay takes place. Therefore, if you have information about the speed of the presented process, you can find out how old the mineral is. For example, the half-life of radium is about 1590 years. And the final decay of this element will occur in a period of time that is ten times longer than the half-life. Nuclear geochronology has the main methods, namely: lead, potassium-argon, rubidium-strontium and radiocarbon.

It was the presented methods of nuclear geochronology that contributed to the establishment of the age of the planet and the time of eras and periods. At the beginning of the 20th century, P. Curie and E. Rutherford introduced a different method of setting the time, which was called radiological. Relative geochronology carries out the activity of determining the relative age of rocks. That is, which accumulations in the earth's crust are younger and which are ancient.

Relative geochronology specializes in such theses as "early, middle and late age". A number of techniques for identifying the relative age of rocks have scientific justification. These methods can be divided into two groups. These groups are called paleontological and non-paleontological. Paleontological methods occupy a leading position, as they are more multifunctional and are applied on a wide front. Of course, there are exceptions. Such a rare case is the lack of natural accumulations in the rocks. Use the presented method when studying fragments of extinct ancient organisms. It should be noted that each rock layer is characterized by a specific set of natural remains. The Englishman W. Smith discovered a certain chronology in the age characteristics of the breeds. Namely, the higher the layer is, the younger it is in age. Consequently, the content of microorganism residues in it will be an order of magnitude higher. Also, W. Smith owns the first geological map of England. On this map, the scientist divided the rocks by age.

Non-paleontological methods for determining the relative age of rocks are used in cases where there are no organic remains in the rocks under study. In this case, there are stratigraphic, lithological, tectonic and geophysical methods. For example, when using the stratigraphic method, it is possible to establish the chronology of the formation of layers at their standard occurrence, namely, those layers that lie below will be more ancient.

The establishment of the chronology of the formation of rocks is carried out by relative geochronology, while the specific determination of age in units of time is carried out by absolute geochronology. The purpose of geological time is to discover the temporal chronology of geological phenomena.

Geological table

In order to establish the age criteria for rocks, scientists use a wide variety of methods. Therefore, it was expedient to create a highly specialized scale for ease of use. Geological time according to this scale is divided into time intervals. A certain segment is characterized by a specific stage in the structure of the earth's crust and the formation of living organisms. The presented scale has a name - geochronological table. It has such subgroups as eon, era, period, epoch, century, time. It should be noted that each group is characterized by a certain set of savings. Such a collection, in turn, is called a stratigraphic complex, which also has a number of types, namely: eonoteme, group, system, department, stage, zone. For example, the system belongs to the stratigraphic category, and the time group of the geochronological department belongs to its characteristic subgroup, which is called the era. As a consequence, there are two scales: stratigraphic and geochronological. The stratigraphic school is used when accumulations in rocks are studied. Since any geological processes are carried out on the planet at any time. The geochronological scale is used to set relative time. Since the scale was approved, its structure has undergone many changes.

To date, the most voluminous stratigraphic category is eonotemes. It is divided into Archean, Proterozoic and Phanerozoic. In the geochronological scale, these classes are subject to categories of diverse activities. Based on the time of existence on Earth, scientists identified two eonotems: Archean and Proterozoic. It is these eonotemes that comprised about eighty percent of the entire time. The remaining Phanerozoic eonoteme is noticeably smaller than the previous eons, since it covered only about five hundred and seventy million years. This eonoteme is divided into three main classes: Paleozoic, Mesozoic and Cenozoic.

The names of eonotems and classes come from the Greek language:

• Archeos - the most ancient;
• Proteros - primary;
• Paleos - ancient;
• Mezos - medium;
• Kainos - new;

From the word form "zoikos", which has the definition of "life", the word "zoi" was formed. Based on this word formation, scientists have identified the era of life on Earth. For example, the Paleozoic era means the era of ancient life.

Eras and periods

Based on the geochronological table, experts divided the history of the planet into five geological eras. The above eras received the following names: Archean, Proterozoic, Paleozoic, Mesozoic, Cenozoic. Also, era data is divided into periods. The number of these time intervals is equal to twelve, which apparently exceeds the number of eras. The time span of these stages is from twenty to one hundred million years. The last period of the Cenozoic era is not completed, since its time period is about two million years.

Archean era. This era began its existence after the formation and structuring of the earth's crust on the planet. By this time period, there were already rocks on the planet and the processes of erosion and accumulation of precipitation had begun. This era lasted for about two billion years. It is the Archean era that scientists consider the longest in time. During its course, volcanic processes were active on the planet, depths were raised, which contributed to the formation of mountains. Unfortunately, most of the fossils were destroyed, but some general data about this era still survive. In the rocks that existed in the Archean era, scientists have found pure carbon. Experts believe that these are modified remains of living organisms. In view of the fact that the amount of graphite indicates the amount of living matter, there was quite a lot of it in this era.

Proterozoic era. According to the time characteristic, this is the next period, which contains one billion years. During this epoch, precipitation accumulated and one global glaciation occurred. Fossils that were found in the mountain strata of this time are the main witnesses that life existed and went through stages of evolution. The remains of jellyfish, mushrooms, algae and much more were found in the rock layers.

Palaeozoic. This era is divided into six time periods:

• Cambrian;
• Ordovician;
• Silur;
• Devonian;
• Carbon/Coal;
• Perm / Perm;

The time period of the Paleozoic era covers three hundred and seventy million years. During this period, representatives of all classes of the animal world appeared. Only birds and mammals were missing.

Mesozoic era. Experts have identified three stages:

• Triassic;

This period covers a time span of one hundred and sixty-seven million years. During the first two periods, the main part of the continents carried out a rise above sea level. Climatic conditions gradually changed and became warmer. There is a popular stone forest in Arizona that has existed since the Triassic period. During the last period, a gradual rise of the sea occurs. The North American continent was completely submerged, as a result of which the Gulf of Mexico was connected to the Arctic basin. The end of the Cretaceous period is characterized by the fact that large uplifts of the earth's crust occurred. So the Rocky Mountains, the Alps, the Himalayas, the Andes appeared.

Cenozoic era. This period continues to this day. Experts divide it into three periods:

• Paleogene;
• Neogene;
• Quaternary;

The last period is characterized by special features. During this period, the final formation of the planet took place. New Guinea and Australia have separated. The two Americas have merged. This time period was identified by J. Denoyer in 1829. The main feature is that a person appeared.

It is during this period that all of humanity lives today.

I have long been interested in the history of our planet. After all, the world that we see today was not always so. It is difficult to even imagine what was on our planet many millions or even several billion years ago. Each period was characterized by some of its own characteristics.

What were the main eras and periods on our planet

I will briefly touch on the topic of eras and periods in general terms. So, all 4.5 billion years, scientists divide like this.

• The Precambrian era (Catarchean, Archean and Proterozoic periods) - in terms of duration, this is the longest era, which lasted almost 4 billion years.
• The Paleozoic era (includes six periods) - lasted a little less than 290 million years, at which time the conditions for life were finally formed, first in water, and then on land.
• The Mesozoic era (includes three periods) is the era of the dominance of reptiles on our planet.
• The Cenozoic era (consists of the Paleogene, Neogene and Anthropogenic periods) - in this era we now live, and to be more specific, in the Anthropogene.

Each era usually ended with some kind of cataclysm.

Mesozoic era

Almost everyone knows about this era, because many have seen the American film "Jurassic Park", in which different breeds of dinosaurs appear. Yes, yes, it was these animals that dominated at that time.

The Mesozoic consists of the following segments:

• Triassic;
• Jurassic;
• chalky.

During the Jurassic period, dinosaurs reached their greatest development. There were giant species that reached a length of up to thirty meters. There were also very large and tall trees, and there was a minimum of vegetation on the ground. Of the low-growing plants, ferns predominated.

At the beginning of this era, there was a single mainland, but then it split into six parts, which eventually took on a modern look.

Two million years before the extinction of the dinosaurs, the most formidable predator appeared - Tyrannosaurus. And these reptiles died out after the earth collided with a comet. As a result, about 65% of all life on the planet died.

This era ended about sixty-five million years ago.