Ancient eras. Era of earth development

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 aquatic environment, and only a billion years later 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, pulmonary respiration appeared. An important stage in development was the formation of the brain, conditioned and unconditioned reflexes, survival instincts. Further evolution of animals provided the basis for the formation of mankind.

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

There are five eras:

• Archean;
• proterozoic;
• paleozoic;
• Mesozoic;
• Cenozoic.

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

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

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

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

The Paleozoic era includes six periods.

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

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

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

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

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

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

The Mesozoic era is divided into 3 periods:

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

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

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

The Cenozoic era consists of three periods:

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

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

Quaternary period or anthropogen(2.6 million years ago - today). Significant event period - the appearance of man, first Neanderthals, and soon Homo sapiens. Vegetable and animal world acquired modern features.

The idea of how life was born in the ancient eras of the Earth give us fossil remains of organisms, but they are distributed among individual geological periods extremely uneven.

Geological periods

The era of the ancient life of the Earth includes 3 stages of the evolution of the plant and animal world.

Archean era

Archean era - oldest era in the history of existence. Its origin dates back to about 4 billion years ago. And the duration is 1 billion years. This is the beginning of the formation of the earth's crust as a result of the activity of volcanoes and air masses, abrupt changes in temperature and pressure. There is a process of destruction of primary mountains and the formation of sedimentary rocks.

The most ancient Archaeozoic layers of the earth's crust are represented by strongly altered, otherwise metamorphosed rocks, therefore they do not contain noticeable remains of organisms.
But it is completely wrong on this basis to consider the Archaeozoic as a lifeless era: in the Archaeozoic there were not only bacteria and algae, but also more complex organisms.

Proterozoic era

The first reliable traces of life in the form of extremely rare finds and poor quality preservation are found in proterozoic, otherwise - the era of "primary life". The duration of the Proterozoic era is about 2 million years.

Traces of crawling found in the rocks of the Proterozoic annelids, sponge needles, shells of the simplest forms of brachiopods, arthropod remains.

Shoulder-footed, distinguished by an exceptional variety of forms, were widespread in the ancient seas. They are found in sediments of many periods, especially the next, Paleozoic era.

Brachiopod shell "Horistites Moskvenzis" (ventral valve)

Only certain species of brachiopods have survived to this day. Most of the brachiopods had a shell with unequal valves: the abdominal shell, on which they lie or are attached to the seabed with the help of a "leg", was usually larger than the dorsal one. On this basis, in general, it is not difficult to recognize brachiopods.

The insignificant amount of fossil remains in Proterozoic sediments is explained by the destruction of most of them as a result of alteration (metamorphization) of the containing rock.

Sediments help to judge how much life was represented in the Proterozoic. limestone which then turned into marble... Limestones apparently owe their origin to a special type of bacteria that secreted lime carbonate.

The presence of interlayers in the Proterozoic sediments of Karelia shungite, similar to anthracite coal, suggests that the initial material for its formation was the accumulation of algae and other organic residues.

In this distant time, the most ancient land was still not lifeless. Bacteria settled in the vast expanses of the still deserted primary continents. With the participation of these simplest organisms, the weathering and loosening of the rocks that formed the most ancient earth's crust took place.

According to the assumption of the Russian academician L. S. Berga(1876-1950), who studied how life arose in the ancient eras of the Earth, at this time soils had already begun to form - the basis for the further development of the vegetation cover.

Palaeozoic

Deposits next in time Paleozoic era, in other words, the era of "ancient life", which began about 600 million years ago, sharply differ from the Proterozoic in the abundance and variety of forms even in the most ancient, Cambrian period.

Based on the study of the remains of organisms, it is possible to reconstruct the following picture of the development of the organic world, characteristic of this era.

There are six periods of the Paleozoic era:

Cambrian period

Cambrian period was described for the first time in England, the Cambrian county, where its name came from. During this period, all life was associated with water. These are red and blue-green algae, limestone algae. Algae released free oxygen, which enabled the development of organisms that consume it.

A close look at the blue-green Cambrian clays, which are clearly visible in deep sections of river valleys near St. Petersburg and especially in the coastal regions of Estonia, made it possible to establish in them (through a microscope) the presence of plant spores.

This definitely suggests that some of the species that have existed in water bodies since the earliest times of the development of life on our planet moved to land about 500 million years ago.

Among the organisms that inhabited the most ancient Cambrian reservoirs, invertebrates enjoyed exceptional distribution. Invertebrates, except for the smallest protozoa - rhizopods, were widely represented worms, brachiopods and arthropods.

Among arthropods, these are primarily various insects, especially butterflies, beetles, flies, dragonflies. They appear much later. In addition to insects, this type of animal world also includes arachnids and centipedes.

Among the most ancient arthropods, there were especially many trilobites, similar to modern woodlice, only much larger than them (up to 70 centimeters), and crustaceans, sometimes reaching impressive sizes.

Trilobites - representatives of the animal world of the most ancient seas

In the body of a trilobite, three lobes are clearly distinguished, and it is not for nothing that it is called that: in translation from the ancient Greek "trilobos" - three-lobe. Trilobites not only crawled along the bottom and buried themselves in the silt, but could also swim.

Among trilobites, generally medium-sized forms prevailed.
By the definition of geologists, trilobites - "guiding fossils" - are characteristic of many deposits of the Paleozoic.

Fossils that are dominant at a given geological time are called guiding fossils. The leading fossils are usually easily dated by the age of the deposits in which they are found. Trilobites flourished in the Ordovician and Silurian periods. They disappeared at the end of the Paleozoic era.

Ordovician period

Ordovician period characterized by a warmer and milder climate, as evidenced by the presence of limestone, shale and sandstone in the rock sediments. At this time, the area of ​​the seas increases significantly.

This promotes the multiplication of large trilobites, 50 to 70 cm long. In the seas appear sea ​​sponges, molluscs, and the first corals.

First corals

Silurian

What did the Earth look like in Silurian? What changes have occurred on the pristine continents? Judging by the prints on clay and other stone material, we can definitely say that at the end of the period, the first terrestrial vegetation appeared on the shores of water bodies.

The first plants of the Silurian period

They were small leafy plants, resembling rather sea brown algae, which have neither roots nor leaves. The role of leaves was played by green, sequentially branching stems.

Psilophyte Plants - Naked Plants

The scientific name of these ancient progenitors of all terrestrial plants (psilophytes, otherwise - "naked plants", that is, plants without leaves) conveys them well distinctive features... (Translated from the ancient Greek "psilos" is bald, naked, and "phytos" is a trunk). Their roots were also undeveloped. Psilophytes grew on swampy swampy soils. Imprint in breed (right) and regenerated plant (left).

Inhabitants of reservoirs of the Silurian period

From inhabitants marine Silurian reservoirs it should be noted, apart from trilobites, coral and echinoderms - sea ​​lilies, sea ​​urchins and stars.

Sea lily "Acantocrinus-rex"

The sea lilies, the remains of which were found in the sediments, looked very little like predatory animals. The sea lily "Acantocrinus-rex" means "prickly lily-king" in translation. The first word is formed from two Greek words: "acanthus" - a thorny plant and "crinon" - a lily, the second Latin word "rex" - a king.

A huge number of species were represented by cephalopods, and especially brachiopods. In addition to cephalopods, which had an inner shell, like belemnites, cephalopods with an external shell were widespread in the earliest periods of the life of the Earth.

The shell was straight and bent in a spiral shape. The shell was sequentially divided into chambers. In the largest, outer chamber, the body of a mollusk was placed, the rest were filled with gas. A tube passed through the chambers - a siphon, which allowed the mollusk to regulate the amount of gas and, depending on this, float or sink to the bottom of the reservoir.

At present, of such cephalopods, only one boat with a coiled shell has been preserved. Ship, or nautilus, which is the same thing, translated from Latin - an inhabitant of the warm sea.

The shells of some Silurian cephalopods, such as orthoceras (translated from the ancient Greek "straight horn": from the words "ortoe" - straight and "keras" - horn), reached gigantic proportions and looked more like a straight two-meter pillar than a horn.

Limestones in which orthoceratites are found are called orthoceratite limestones. Square limestone slabs were widely used in pre-revolutionary St. Petersburg for sidewalks, and characteristic cuts of orthoceratite shells were often clearly visible on them.

A remarkable event of the Silurian time was the appearance of clumsy “ shell fish”, Which had an external bone shell and not ossified internal skeleton.

Their spinal column was answered by a cartilaginous cord - a chord. The carapaces did not have jaws or paired fins. They were poor swimmers and therefore stuck more to the bottom; silt and small organisms served as food.

Panzer fish pterichtis

The carapace fish pterichtis was generally a poor swimmer and led a natural lifestyle.

It can be assumed that Botryolepis was already much more mobile than pterychtis.

Silurian sea predators

In later sediments, there are already remnants of marine predators close to sharks. From these lower fish, which also possessed a cartilaginous skeleton, only teeth were preserved. Judging by the size of the teeth, for example, from the deposits of the Carboniferous age of the Moscow region, it can be concluded that these predators reached significant sizes.

In the development of the animal world of our planet, the Silurian period is interesting not only because the distant ancestors of fish appear in its reservoirs. At the same time, another equally important event took place: representatives of arachnids got out of the water onto land, among them ancient scorpions, still very close to crustaceans.

Crayfish inhabitants of shallow seas

On the right, at the top - a predator - pterygotus, armed with strange claws, reaching 3 meters, glory - eurypterus - up to 1 meter long.

Devonian

The dry land - the arena of the future life - gradually takes on new features, especially characteristic of the next, the Devonian period. At this time, woody vegetation already appears, first in the form of undersized shrubs and small trees, and then larger ones. Among the Devonian vegetation, we will meet well-known ferns, other plants will remind us of the graceful herringbone of horsetail and green ropes of lymphoids, only not creeping along the ground, but proudly rising upward.

In the later in age Devonian deposits, fern-like plants also appear, which multiplied not by spores, but by seeds. These are seed ferns, which occupy a transitional position between spore and seed plants.

Fauna of the Devonian period

Animal world seas Devonian period rich in brachiopods, corals and sea lilies; trilobites are beginning to play a secondary role.

Among the cephalopods, new forms appear, only not with a straight shell, like in Orthoceras, but with a spirally twisted one. They are called ammonites. They got their name from the Egyptian sun god Ammon, near the ruins of a temple in Libya (in Africa), these characteristic fossils were first discovered.

By general view it is difficult to confuse them with other fossils, but at the same time it is necessary to warn young geologists about how difficult it is to identify individual types of ammonites, the total number of which is not hundreds, but thousands.

Ammonites flourished especially in the next, Mesozoic era. .

Fish developed significantly in the Devonian period. In armored fish, the bony carapace was shortened, which made them more mobile.

Some armored fish, such as the nine-meter giant dinichtis, were terrible predators (in Greek, "deinos" - terrible, terrible, and "ichthis" - fish).

The nine-meter dinichthis was obviously a great threat to the inhabitants of the reservoirs.

In the Devonian reservoirs, there were also cross-finned fish, from which lungfish came from. This name is explained by the structural features of the paired fins: they are narrow and, moreover, sit on an axis covered with scales. This feature differs, for example, from pikeperch, perch and other bony fish called ray-finned.

Cis-fin is the ancestor of teleost fishes, which appeared much later - at the end of the Triassic.
We would not have had an idea of ​​what exactly the cross-finned fish that lived at least 300 million years ago looked like if it were not for the successful catches of the rarest specimens of their modern generation in the middle of the 20th century off the coast of South Africa.

They live, obviously, at considerable depths, which is why they come across so rarely to fishermen. The captured species was named coelacanth. It reached 1.5 meters in length.
By their organization, lungfish are close to the cross-finned fish. They have lungs that match the swim bladder of a fish.

By their organization, lungfish are close to the cross-finned fish. They have lungs that match the swim bladder of a fish.

How unusual the cross-finned looked can be judged by the specimen, the coelacanth caught in 1952 near the Comoros, west of the island of Madagascar. This 1.5 liter fish weighed about 50 kg.

The descendant of ancient lung-breathing fish - the Australian ceratodus (translated from ancient Greek - horntooth) - reaches two meters. He lives in drying up reservoirs and, while there is water in them, breathes with gills, like all fish, when the reservoir begins to dry out, he switches to pulmonary respiration.

Australian ceratodus - a descendant of ancient lungfish

His respiratory organs are the swim bladder, which has a cellular structure and is equipped with numerous blood vessels. In addition to ceratodus, two more species of lungfish are now known. One of them lives in Africa, and the other in South America.

Transition of vertebrates from water to land

Amphibian transformation table.

The oldest fish

The first picture shows the oldest cartilaginous fish, diplocanthus (1). Below it is a primitive cross-finned eustenopteron (2), below is a supposed transitional form (3). In a huge amphibian eogirinus (about 4.5 m in length), the limbs are still very weak (4), and only as they master the terrestrial lifestyle, they become a reliable support, for example, for a heavy Eriops, about 1.5 m in length (5).

This table helps to understand how, as a result of a gradual change in the organs of movement (and respiration), aquatic organisms moved to land, how the fin of a fish was transformed into a limb of amphibians (4), and then reptiles (5). Along with this, the spine and skull of the animal changes.

The first wingless insects and terrestrial vertebrates appeared in the Devonian period. Hence, it can be assumed that it was at this time, and possibly even somewhat earlier, that the transition of vertebrates from water to land took place.

It was realized through such fish, in which the swim bladder was changed, like in lungs, and limbs, similar to fins, gradually turned into five-toed ones, adapted to a terrestrial lifestyle.

Metopoposaurus still had difficulty getting out onto land.

Therefore, the closest ancestors of the first terrestrial animals should be considered not lung-breathing, but precisely cross-finned fish, adapted to breathing atmospheric air as a result of periodic drying out of tropical reservoirs.

The connecting link of terrestrial vertebrates with cross-finned are ancient amphibians, or amphibians, united by the common name of stegocephaly. Translated from the ancient Greek stegocephaly - "covered head": from the words "stege" - a roof and "mullet" - a head. This name is given because the roof of the skull is a solid shell of closely adjacent bones.

There are five openings in the skull of a stegocephalus: two pairs of openings — the eye and nasal ones, and one — for the parietal eye. By appearance stegocephals somewhat resembled salamanders and often reached considerable sizes. They lived in swampy areas.

The remains of stegocephals were sometimes found in the hollows of tree trunks, where they were obviously sheltered from daylight. In the larval state, they breathed with gills, like modern amphibians.

Stegocephaly found especially favorable conditions for their development in the next Carboniferous period.

Carboniferous period

Warm and humid climate, especially the first half Carboniferous period, favored the lush flourishing of terrestrial vegetation. Coal forests never seen before, of course, were completely different from modern ones.

Among those plants that about 275 million years ago settled in the swampy swampy expanses, giant treelike horsetails and moss were clearly distinguished in their characteristic features.

Of the treelike horsetails, the Kalamites used a significant distribution, and from the ploons - the giant lepidodendrons and the graceful sigillaria somewhat inferior to them in size.

In the seams of coal and the rocks that cover them, well-preserved remains of vegetation are often found, not only in the form of clear imprints of leaves and tree bark, but also whole stumps with roots and huge trunks that have turned into coal.

From these fossil remains, you can not only restore the general appearance of the plant, but also get acquainted with its internal structure, which is clearly visible under a microscope in thin sections of the trunk, as thin as a sheet of paper. The Kalamites derive their name from the Latin word "kalamus" - reed, reed.

Slender, hollow inside calamite trunks, ribbed and with transverse constrictions, as in the well-known horsetails, rose in slender columns 20-30 meters from the ground.

Small, narrow leaves, collected by rosettes on short stalks, gave, perhaps, some resemblance to Kalamite with the Siberian taiga larch, transparent in its elegant attire.

Nowadays, horsetails - field and forest - are common throughout the globe, except for Australia. In comparison with their distant ancestors, they seem to be pitiful dwarfs, who, moreover, especially field horsetail, enjoy a bad reputation with the farmer.

Horsetail is the worst weed, which is difficult to fight, since its rhizome goes deep into the ground and constantly gives new shoots.

Large species of horsetails - up to 10 meters in height are currently preserved only in the tropical forests of South America. However, these giants can only grow leaning against neighboring trees, since they are only 2-3 centimeters across.
Lepidodendrons and sigillaria occupied a prominent place among the Carboniferous vegetation.

Although in appearance they did not look like modern lyres, they nevertheless resembled them in one characteristic feature. The powerful trunks of lepidodendrons, reaching 40 meters in height, with a diameter of up to two meters, were covered with a distinct pattern of fallen leaves.

These leaves, while the plant was still young, sat on the trunk in the same way as its small green scales - leaves - sit on the plow. As the tree grew, the leaves grew old and fell off. From these scaly leaves the giants of the Carboniferous forests got their name - lepidodendrons, otherwise - "scaly trees" (from the Greek words: "lepis" - scales and "dendron" - a tree).

Traces of fallen leaves on the bark of sigillaria had a slightly different shape. They differed from lepidodendrons in their lower height and greater slenderness of the trunk, which branched only at the very top and ended in two huge bunches of hard leaves, one meter each.

Acquaintance with the carboniferous vegetation will be incomplete, if not to mention also the kordaites, which are close to conifers in the structure of their wood. They were tall (up to 30 meters), but relatively thin-stemmed trees.

The Cordaites derive their name from the Latin elephant "kor" - heart, since the seed of the plant had a heart-shaped shape. These beautiful trees crowned lush crown ribbon-like leaves (up to 1 meter in length).

Judging by the structure of the wood, the trunks of the coal giants still did not have the strength that is inherent in the bulk modern trees... Their bark was much stronger than wood, hence the general fragility of the plant, weak resistance to fracture.

Strong winds and especially storms broke trees, felled huge forests, and new lush shoots grew out of the swampy soil again ... The dumped wood served as the initial material from which powerful coal seams were later formed.

Lepidodendrons, otherwise - scaly trees, reached enormous sizes.

It is not correct to attribute the formation of coal only to the Carboniferous period, since coals are also found in other geological systems.

For example, the oldest Donetsk coal basin was formed in the Carboniferous time. The Karaganda basin is the same age as it.

As for the largest Kuznetsk basin, it only in its insignificant part belongs to the Carboniferous system, and mainly to the Permian and Jurassic systems.

One of the largest pools - "Zapolyarnaya Kochegarka" - the richest Pechora basin, was also formed mainly in the Permian time and, to a lesser extent, in the Carboniferous.

Flora and fauna of the Carboniferous period

For marine sediments Carboniferous period representatives of the simplest animals from the class are especially characteristic rhizome... The most typical were the fusulins (from the Latin word "fuzus" - "spindle") and schwagerins, which served as the source material for the formation of strata of fusulin and schwagerin limestones.

Carboniferous rhizomes: 1 - fusulin; 2 - schwagerin

Carboniferous rhizomes - fusulin (1) and schwagerin (2) are increased 16 times.

Oblong, like wheat grains, fusulins and almost spherical schwagerins are clearly visible on the limestones of the same name. Corals and brachiopods developed magnificently, giving many leading forms.

The most widespread were the genus produktus (translated from Latin - "stretched") and spirifer (translated from the same language - "bearing spiral", which supported the soft "legs" of the animal).

Trilobites, which prevailed in previous periods, are much less common, but on land other representatives of arthropods begin to gain a noticeable distribution - long-legged spiders, scorpions, huge centipedes (up to 75 centimeters in length) and especially giant insects, similar to dragonflies, with a wingspan up to 75 centimeters! The largest modern butterflies in New Guinea and Australia reach a wingspan of 26 centimeters.

The oldest coal dragonfly

The oldest Carboniferous dragonfly seems to be an exorbitant giant in comparison with the modern one.

Judging by the fossil remains, sharks have noticeably multiplied in the seas.
Amphibians, firmly entrenched on land in the Carboniferous, go through a further path of development. The dryness of the climate, which increased at the end of the Carboniferous period, gradually forces the ancient amphibians to move away from the aquatic way of life and move mainly to terrestrial existence.

These organisms, transitional to a new way of life, laid eggs on land, and did not spawn into the water, like amphibians. The offspring hatched from eggs acquired such characteristics that sharply distinguished them from their progenitors.

The body was covered, like a shell, with scale-like outgrowths of the skin, which protected the body from moisture loss through evaporation. So reptiles, or reptiles, separated from amphibians (amphibians). In the next, Mesozoic era, they conquered land, water and air.

Permian period

The last period of the Paleozoic - Permian- was much shorter in duration than the coal one. It should be noted, in addition, the great changes that took place in the ancient geographic map world - land, as confirmed by geological research, gains a significant predominance over the sea.

Permian plants

The climate of the northern continents of the Upper Permian was dry and sharply continental. Sandy deserts are widely spread in places, as evidenced by the composition and reddish tint of the rocks that make up the Permian Formation.

This time was marked by the gradual extinction of the giants of the Carboniferous forests, the development of plants close to conifers, and the emergence of cycads and ginkgoids, which became widespread in the Mesozoic.

Cycad plants have a spherical and tuberous stem immersed in the soil, or, conversely, a powerful columnar trunk up to 20 meters high, with a lush rosette of large feathery leaves. In appearance, cycad plants resemble the modern sago palm of tropical forests in the Old and New Worlds.

Sometimes they form impassable thickets, especially on the flooded banks of the rivers of New Guinea and the Malay Archipelago (Great Sunda Islands, Small Sunda, Moluccas and Philippines). Nutritious flour and cereals (sago) are made from the soft heart of the palm tree, which contains starch.

Sigilaria forest

Sago bread and porridge are the daily food of millions of inhabitants of the Malay Archipelago. The sago palm is widely used in housing and household products.

Another very peculiar plant, ginkgo, is also interesting because it has survived in the wild only in some places in southern China. Since time immemorial, Ginkgo has been carefully bred near Buddhist temples.

Ginkgo was brought to Europe in the middle of the 18th century. Now it is found in park culture in many places, including ours on the Black Sea coast. Ginkgo is a large tree up to 30-40 meters in height and up to two meters thick, in general resembles a poplar, and in its youth it looks more like some conifers.

Branch of modern ginkgo biloba with fruits

Leaves are petiolate, like that of an aspen, have a fan-shaped blade with fan-shaped venation without transverse bridges and an incision in the middle. For the winter, the foliage falls. The fruit - a fragrant drupe like a cherry - is as edible as the seeds. In Europe and Siberia, ginkgo disappeared during the Ice Age.

Cordaites, conifers, cycads and ginkgoes belong to the group of gymnosperms (since their seeds lie open).

Angiosperms, monocotyledonous and dicotyledonous, appear somewhat later.

Fauna of the Permian period

Among the aquatic organisms that inhabited the Permian seas, ammonites were prominently distinguished. Many groups of marine invertebrates, such as trilobites, some corals and most brachiopods, have become extinct.

Permian period characterized by the development of reptiles. Particularly noteworthy are the so-called animal-like lizards. Although they possessed some features characteristic of mammals, for example, teeth and skeletal features, they nevertheless retained a primitive structure that brings them closer to stegocephals (from which reptiles originated).

The bestial Permian lizards were of considerable size. The sedentary herbivorous pareiasaurus reached two and a half meters in length, and the formidable predator with the teeth of a tiger, in other words - the "animal-toothed lizard" - foreigners, was even larger - about three meters.

Pareiasaurus in translation from ancient Greek means "chubby lizard": from the words "pareya" - cheek and "zauros" - lizard, lizard; the animal-toothed lizard of foreigners is named so in memory of the famous geologist - prof. A. A. Inostrantseva (1843-1919).

The richest finds from the ancient life of the Earth of the remains of these animals are associated with the name of the enthusiastic geologist prof. V.P. Amalitsky(1860-1917). This persistent researcher, without receiving the necessary support from the treasury, nevertheless achieved remarkable results in his work. Instead of a well-deserved summer vacation, he, together with his wife, who shared all the hardships with him, went in a boat with two oarsmen in search of the remnants of animal-like dinosaurs.

Stubbornly, for four years he conducted his research on the Sukhona, the Northern Dvina and other rivers. Finally, he managed to make discoveries extremely valuable for world science on the Northern Dvina, not far from the city of Kotlas.

Here, in the coastal cliff, the rivers were found in thick lentils of sand and sandstone, among striped junk, nodules of bones of ancient animals (nodules are stone accumulations). The fees of just one year of work of geologists took two freight cars during transportation.

Subsequent developments of these bone-bearing accumulations further enriched the information about the Permian reptiles.

The place where the Permian lizards were found

Place of finds of the Permian lizards discovered by the professor V.P. Amalitsky in 1897, the right bank of the Malaya Severnaya Dvina River near the village of Efimovka, near the town of Kotlas.

The richest collections taken out from here are determined by tens of tons, and the skeletons collected from them represent the richest collection in the Paleontological Museum of the Academy of Sciences, which has no equal in any museum in the world.

Among the ancient animal-like Permian reptiles, the original three-meter predator Dimetrodon stood out, otherwise it was “two-dimensional” in length and height (from the ancient Greek words: “di” - twice and “metron” - measure).

Bestial Dimetrodon

Its characteristic feature is the unusually long processes of the vertebrae, forming a high ridge (up to 80 centimeters) on the animal's back, apparently, were connected by a skin membrane. In addition to predators, this group of reptiles also included plant- or mollusk-eating forms, also of very significant sizes. The fact that they ate molluscs can be judged by the structure of their teeth, suitable for crushing and grinding shells. (No ratings yet)

The history of planet Earth is already about 7 billion years old. During this time, our common home has undergone significant changes, which was a consequence of the change in periods. in chronological order, they reveal the entire history of the planet from its very appearance to the present day.

Geological chronology

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

The largest subdivisions in this scale are eonothems, eras and periods.

Formation of the Earth

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

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

Precambrian aeon

In the geochronology of the Earth, the first eon is called the Precambrian. It spans 4.5 billion to 600 million years ago. That is, the lion's share of the planet's history is covered first. However, this eon is divided into three more - katarchean, archean, proterozoic. And often the first of them stands out as an independent eon.

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

Catarchean eon

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

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

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

Archean eon

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

Proterozoic eon

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

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

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

Phanerozoic eon

All geological periods in chronological order can be divided into two types - explicit and hidden. Phanerozoic refers to the explicit. At this time, a large number of living organisms with mineral skeletons appear. The epoch preceding the Phanerozoic was called hidden because practically no traces of it were found due to the absence of mineral skeletons.

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

Eras of the Precambrian Aeon

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

The Proterozoic consists of three great eras:

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

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

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

Eras of the Phanerozoic aeon

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

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

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

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

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

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

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

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

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

One of the important tasks of modern natural science in the field of earth sciences is the restoration of the history of its development. According to modern cosmogonic concepts, the Earth was formed from gas and dust scattered in the protosolar system. One of the most probable variants of the Earth's origin is as follows. First, the Sun and a flattened rotating circumsolar nebula from an interstellar gas and dust cloud formed under the influence of, for example, an explosion of a nearby supernova. Further, the evolution of the Sun and the circumsolar nebula took place with the transfer of the angular momentum from the Sun to the planets in an electromagnetic or turbulent-convective way. Subsequently, the "dusty plasma" condensed into rings around the Sun, and the material of the rings formed the so-called planetesimals, which condensed to the planets. After that, a similar process was repeated around the planets, which led to the formation of satellites. It is believed that this process took about 100 million years.

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

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

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

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

The principles of periodization of the geological history of the Earth

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

The main thing in relative geochronology is the biostratigraphic, or paleontological, method of establishing the relative age and sequence of rocks. This method was proposed by W. Smith at the beginning of the 19th century, and then developed by J. Cuvier and A. Bronyard. The fact is that in most sedimentary rocks you can find the remains of animals or plant organisms. J. B. Lamarck and C. Darwin found that animals and plant organisms in the course of geological history have gradually improved in the struggle for existence, adapting to changing living conditions. Some animals and plant organisms died out at certain stages of the Earth's development, and others, more advanced ones, came to replace them. Thus, according to the remains of more primitive ancestors who lived earlier, found in any layer, one can judge about the relatively older age of this layer.

Another method of geochronological dissection of rocks, which is especially important for the dissection of magmatic formations of the ocean floor, is based on the property of magnetic susceptibility of rocks and minerals formed in the Earth's magnetic field. With a change in the orientation of the rock relative to the magnetic field or the field itself, part of the "innate" magnetization is retained, and the change in polarity is imprinted in the change in the orientation of the remanent magnetization of the rocks. At present, a scale has been established for the change of such eras.

Absolute geochronology - the study of measuring geological time, expressed in conventional absolute astronomical units(years), - determines the time of occurrence, completion and duration of all geological events, primarily the time of formation or transformation (metamorphism) of rocks and minerals, since the age of geological events is determined by their age. The main method here is to analyze the ratio of radioactive substances and their decay products in rocks formed in different eras.

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

In 1881, at the II International Geological Congress in Bologna (Italy), the main subdivisions of the combined stratigraphic (for separating layered sedimentary rocks) and geochronological scales were approved. On this scale, the history of the Earth was divided into four eras in accordance with the stages of development of the organic world: 1) Archean, or Archeozoic - the era of ancient life; 2) Paleozoic - the era of ancient life; 3) Mesozoic - the era of middle life; 4) Cenozoic - the era of new life. In 1887 from the Archean era identified the Proterozoic - the era of primary life. Later, the scale was improved. One of the options for the modern geochronological scale is presented in table. 8.1. The Archean era is divided into two parts: the early (older than 3500 million years) and the late Archean; Proterozoic - also into two: early and late Proterozoic; in the latter, the Riphean (the name comes from the ancient name of the Ural Mountains) and the Vendian periods are distinguished. The Phanerozoic zones are subdivided into the Paleozoic, Mesozoic and Cenozoic eras and consists of 12 periods.

Table 8.1. Geochronological scale

			Age (beginning),
Phanerozoic	Cenozoic	Quaternary
		Neogene
		Paleogene
	Mesozoic
		Triassic
	Paleozoic	Permian
		Coal
		Devonian
		Silurian
		Ordovician
		Cambrian
Cryptose	Proterozoic	Vendian
		Riphean
		Karelian
	Archean
	Catarchean

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

Let us briefly consider the main stages of the evolution of the earth's crust as an inert substrate, on which the diversity of the surrounding nature has developed.

Vapxee the still rather thin and plastic crust, under the influence of stretching, experienced numerous discontinuities, through which basaltic magma again rushed to the surface, filling troughs hundreds of kilometers long and many tens of kilometers wide, known as green-stone belts (by this name they owe the predominant greenschist low-temperature metamorphism of basaltic rocks). Along with basalts, among the lavas of the lower, the main in terms of the thickness of the section of these belts, there are high-magnesian lavas, which indicate a very large degree of partial melting of mantle material, which indicates a high heat flow, much higher than the modern one. The development of greenstone belts consisted in a change in the type of volcanism in the direction of an increase in the content of silicon dioxide (SiO 2), in compression deformations and metamorphism of sedimentary-volcanogenic filling, and, finally, in the accumulation of clastic sediments, indicating the formation of a mountainous relief.

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

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

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

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

Paleozoic stage The evolution of the earth's crust was characterized by the intensive development of mobile belts - intercontinental and continental margins (the latter on the periphery of the Pacific Ocean). These belts were dissected into marginal seas and island arcs, their sedimentary-volcanic strata underwent complex fold-thrust and then fault-strike-slip deformations, granites were introduced into them, and on this basis folded mountain systems were formed. This process was uneven. A number of intense tectonic epochs and granite magmatism are distinguished in it: Baikal - at the very end of the Proterozoic, Salair (from the Salair ridge in Central Siberia) - at the end of the Cambrian, takovo (from the Takovo mountains in the east of the United States) - at the end of the Ordovician, Caledonian (from the ancient Roman name of Scotland) - at the end of the Silurian, Acadian (Acadia - the old name of the northeastern states of the United States) - in the middle Devonian, Sudeten - at the end of the Early Carboniferous, the Saal (from the Saale River in Germany) - in the middle of the Early Permian. The first three tectonic epochs of the Paleozoic are often combined in the Caledonian era of tectogenesis, the last three in the Hercynian, or Varissian. In each of the listed tectonic epochs, certain parts of the mobile belts turned into folded mountain structures, and after destruction (denudation) they became part of the basement of young platforms. But some of them experienced some revitalization in subsequent orogeny eras.

By the end of the Paleozoic, the intercontinental mobile belts were completely closed and filled with folded systems. As a result of the withering away of the North Atlantic belt, the North American continent closed with the East European, and the latter (after the completion of the development of the Ural-Okhotsk belt) - with the Siberian, Siberian - with the Sino-Korean. As a result, the supercontinent Laurasia was formed, and the withering away of the western part of the Mediterranean belt led to its unification with the southern supercontinent - Gondwana - into one continental block - Pangea. In the late Paleozoic - early Mesozoic, the eastern part of the Mediterranean belt turned into a huge bay of the Pacific Ocean, along the periphery of which folded mountain structures also rose.

Against the background of these changes in the structure and relief of the Earth, the development of life continued. The first animals appeared in the late Proterozoic, and at the very dawn of the Phanerozoic, almost all types of invertebrates existed, but they were still devoid of shells or shells, which are known from the Cambrian. In the Silurian (or already in the Ordovician), vegetation began to emerge on land, and at the end of the Devonian there were forests that were most widespread in the Carboniferous period. Fish appeared in the Silurian, amphibians in the Carboniferous.

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

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

Intensive mountain building began in the Late Paleogene (40 million years ago), culminating in the last 5 million years. This stage of the formation of young folded-cover mountain structures, the formation of revived arched-block mountains is distinguished as neotectonic. In fact, the neotectonic stage is a substage of the Mesozoic-Cenozoic stage of the Earth's development, since it was at this stage that the main features of the Earth's modern relief took shape, starting with the distribution of oceans and continents.

At this stage, the formation of the main features of modern fauna and flora was completed. The Mesozoic era was the era of reptiles, mammals began to predominate in the Cenozoic, and in the late Pliocene, humans appeared. At the end of the Early Cretaceous, angiosperms appeared and the land acquired a grass cover. At the end of the Neogene and Anthropogene, the high latitudes of both hemispheres were covered by a powerful continental glaciation, the relics of which are the ice caps of Antarctica and Greenland. This was the third major glaciation in the Phanerozoic: the first took place in the Late Ordovician, the second in the late Carboniferous - early Permian; both were common within Gondwana.

QUESTIONS FOR SELF-CONTROL

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

What is internal structure Earth? What is the basis for making a conclusion about its structure?

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

What is the chemical and mineralogical composition of the Earth? On the basis of which a conclusion is made about chemical composition the whole earth and the earth's crust?

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

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

What is atmosphere? What is its structure? What processes are taking place within it? What is weather and climate?

Give a definition of endogenous processes. What endogenous processes do you know? Describe them briefly.

What is the essence of plate tectonics? What are its main provisions?

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

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

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

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

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

LITERATURE

Allison A., Palmer D. Geology. The science of the ever-changing Earth. M., 1984.

Budyko M.I. Climate in the past and in the future. L., 1980.

Vernadsky V.I. Scientific thought as a planetary phenomenon. M., 1991.

V.P. Gavrilov Travel to the past of the Earth. M., 1987.

Geological Dictionary. T. 1, 2.M., 1978.

GorodnitskyA. M., Zonenshain L.P., Mirlin E.G. Reconstruction of the position of the continents in the Phanerozoic. M., 1978.

7... Davydov L.K., Dmitrieva A.A., Konkina N.G. General hydrology. L., 1973.

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

Davis V.M. Geomorphological sketches. M., 1962.

10. Earth. Introduction to General Geology. M., 1974.

11. Climatology / Ed. O.A. Drozdova, N.V. Kobysheva. L., 1989.

Koronovskiy N.V., Yakusheva A.F. Fundamentals of Geology. M., 1991.

Leontiev O.K., Rychagov G.I. General geomorphology. M., 1988.

M. I. Lvovich Water and life. M., 1986.

Makkaveev N.I., Chalov P.C. Channel processes. M., 1986.

Mikhailov V.N., Dobrovolsky A.D. General hydrology. M., 1991.

Monin A.C. Introduction to the theory of climate. L., 1982.

Monin A.C. History of the Earth. M., 1977.

Neklyukova N.P., Dushina I.V., Rakovskaya E.M. and etc. Geography. M., 2001.

G.I. Nemkov and etc. Historical geology. M., 1974.

Restless landscape. M., 1981.

General and field geology / Ed. A.N. Pavlova. L., 1991.

Penck W. Morphological analysis. M., 1961.

Perelman A.I. Geochemistry. M., 1989.

Poltaraus B.V., Sour A.B. Climatology. M., 1986.

26. Problems of Theoretical Geomorphology / Ed. L.G. Nikiforova, Yu.G. Simonov. M., 1999.

Saukov A.A. Geochemistry. M., 1977.

Sorokhtin O. G., Ushakov S. A. Global evolution of the Earth. M., 1991.

Ushakov S.A., Yasamanov H.A. Continental drift and the Earth's climate. M., 1984.

Khain V.E., Lomte M.G. Geotectonics with the basics of geodynamics. M., 1995.

Khain V.E., Ryabukhin A.G. History and methodology of geological sciences. M., 1997.

Khromov S.P., Petrosyants M.A. Meteorology and climatology. M., 1994.

Shchukin I.S. General geomorphology. T.I. M., 1960.

Ecological functions of the lithosphere, Ed. V.T. Trofimova. M., 2000.

Yakusheva A.F., Khain V.E., Slavin V.I. General geology. M., 1988.

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

The 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 periods, periods - into eras, epochs - into centuries.

Eras of life on Earth

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

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

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

These 2 periods of the 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 eras. The history of the development of life on Earth is directly related to changes in the earth's crust and the planet's climate.

Eras of development, countdown

It is customary to allocate the most significant events at special time intervals - eras. Time is counted in reverse order, from the oldest life to the new. There are 5 eras:

Periods of development of life on Earth

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

• Cambrian (Cambrian).
• Ordovician.
• Silurian (Silurian).
• Devonian (Devonian).
• Carboniferous (carbonaceous).
• Perm (Perm).

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

The first 2 periods are included in the Tertiary period with a duration of 59 million years.

Proterozoic era (early life)

6. Perm (Perm)

2. Upper Tertiary (Neogene)

3. Quaternary or anthropogen (human development)

Development of living organisms

The table of the development of life on Earth assumes a 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. Subsequently, the appearance of these living organisms made it possible to divide the world into plant and animal.

• 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. Distribution of angiosperms, reduction of other plant species. Development of bony fish, mammals and birds.

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

Development of inanimate conditions, climate change

The table of the development of life on Earth cannot be presented without data on changes 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: the 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 lined. The atmosphere is dominated by carbon dioxide, the amount of oxygen is minimal. Low salinity in shallow water.

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

Climatic changes in the Proterozoic era

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

Climate Change: Paleozoic Era

During different periods of the Paleozoic era, the following climate changes took place:

• 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, conditions of inanimate nature are diverse. Mountain building takes place, the seas prevail over the land. Areas of different climates, including regions of cooling, have been determined.
• Devonian. The climate is dry and continental. Formation of intermontane depressions.
• Carboniferous period. Subsidence of continents, wetlands. Warm and humid climate, the atmosphere is rich in oxygen and carbon dioxide.
• Permian period. Hot climate, volcanic activity, mountain building, drying up of swamps.

In the Paleozoic era, mountains of the Caledonian folding were formed. Such changes in topography affected the world's oceans - sea basins have shrunk, and a significant land area has been formed.

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

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. Seas prevail over land.
• Cretaceous period. Retreat of the seas from land. The climate is warm, but at the end of the period, global warming is replaced by a cold snap.

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 Cordillera, the mountains of Eastern Siberia, Indochina, partly Tibet were formed, the mountains of the Mesozoic folding were formed. A hot and humid climate prevails, favoring 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's covers advancing from the north have changed the appearance of the continents of the Northern Hemisphere. Thanks to these 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, savannas.
• Quaternary period. Multiple glaciation of the northern hemisphere. Cooling climate.

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, and now scientists continue to study history, make new discoveries that allow modern society learn how life developed on Earth before the appearance of man.

Development of life on Earth lasts over 3 billion years. And this process continues to this day.

The first living things in the Archean were bacteria. Then came unicellular algae, animals and fungi. Unicellular organisms have been replaced by multicellular organisms. At the beginning of the Paleozoic, life was already very diverse: representatives of all types of invertebrates lived in the seas, and the first land plants appeared on land. In the following eras, various groups of plants and animals formed and died out over many millions of years. Gradually, the living world became more and more similar to the modern one.

2.6. The history of the development of life

Previously, scientists believed that the living came from the living. Bacterial spores were brought in from space. Some bacteria created organic matter, others consumed and destroyed them. As a result, the most ancient ecosystem arose, the components of which were linked by the cycle of substances.

Modern scientists have proven that living things came from non-living nature. In the aquatic environment, organic substances were formed from inorganic substances under the influence of the energy of the Sun and the internal energy of the Earth. The most ancient organisms, bacteria, were formed from them.

In the history of the development of life on Earth, several eras are distinguished.

Archaea

The first organisms were prokaryotes. In the Archean era, a biosphere already existed, consisting mainly of prokaryotes. The very first living things on the planet are bacteria. Some of them were capable of photosynthesis. Photosynthesis was carried out by cyanobacteria (blue-green).

Proterozoic

As the oxygen content in the atmosphere increased, eukaryotic organisms began to appear. In the Proterozoic, unicellular plants arose in the aquatic environment, and then unicellular animals and fungi. An important event in the Proterozoic was the emergence of multicellular organisms. By the end of the Proterozoic, Various types invertebrates and chordates.

Paleozoic

Plants

Gradually, land appeared in place of the warm shallow seas. As a result, the first terrestrial plants originated from multicellular green algae. Forests arose in the second half of the Paleozoic. They consisted of ancient ferns, horsetails, and lyre, which multiplied by spores.

Animals

In the early Paleozoic, marine invertebrates flourished. In the seas, vertebrates, shell fish, developed and spread.

In the Paleozoic, the first terrestrial vertebrates appeared - the oldest amphibians. From them, at the end of the era, the first reptiles descended.

The most numerous in the seas of the Paleozoic (the era of ancient life) were trilobites - fossil arthropods, outwardly similar to giant woodlice. Trilobites - existed at the beginning of the Paleozoic, completely extinct 200 million years ago. They swam and crawled in shallow bays, feeding on plants and animal remains. There is an assumption that there were also predators among the trilobites.

Arachnids and giant flying insects, the ancestors of modern dragonflies, were the very first animals to master the land. Their wingspan reached 1.5 m.

Mesozoic

In the Mesozoic, the climate became more arid. Ancient forests gradually disappeared. Spore-bearing plants were replaced by seed-propagating plants. Among animals, reptiles, including dinosaurs, flourished. At the end of the Mesozoic, many species of ancient seed plants and dinosaurs became extinct.

Animals

The largest of the dinosaurs were the brachiosaurs. They reached more than 30 m in length and weighed 50 tons. These dinosaurs had a huge body, long tail and neck, and a small head. If they lived in our time, they would be higher than five-story buildings.

Plants

The most complex plants are flowering plants. They appeared in the middle of the Mesozoic (the era of middle life). Material from the site http://wikiwhat.ru

Cenozoic

Cenozoic - the heyday of birds, mammals, insects and flowering plants. Warm-bloodedness arose in birds and mammals due to the more perfect structure of organ systems. They have become less dependent on environmental conditions and have spread widely on Earth.