What nature was like before our era. Archean era

We present to your attention an article on the classical understanding of the development of our planet Earth, written not boring, understandable and not too long ... .. If any of the people mature age I forgot it - it will be interesting to read, well, for those who are younger, and even for an essay in general, wonderful material.

In the beginning there was nothing. In the endless outer space, there was only a giant cloud of dust and gases. It can be assumed that from time to time through this substance at great speed swept spaceships with representatives of the universal mind. The humanoids looked bored through the windows and did not even remotely suspect that in a few billion years, intelligence and life would arise in these places.

The gas and dust cloud over time transformed into Solar system... And after the star arose, the planets appeared. Our native land became one of them. It happened 4.5 billion years ago. It is from those distant times that the age of the blue planet has been counted, thanks to which we exist in this world.

The entire history of the Earth is divided into two huge stages in time.

The first stage is characterized by the absence of complex living organisms. There were only single-celled bacteria that settled on our planet for about 3.5 billion years back.

The second phase began approximately 540 million years back. This is the time when living multicellular organisms spread across the Earth. This refers to both plants and animals. Moreover, both the sea and the land became their habitat. The second period continues to this day, and man is its crown.

Such huge time stages are called eons... Each eon has its own eonoteme... The latter represents a certain stage in the geological development of the planet, which is fundamentally different from other stages in the lithosphere, hydrosphere, atmosphere, biosphere. That is, each eonoteme is strictly specific and not like the others.

There are 4 eons in total. Each of them, in turn, is subdivided into the eras of the Earth's development, and those are divided into periods. This shows that there is a rigid gradation of large time intervals, and the geological development of the planet is taken as a basis.

Katarchei

The most ancient aeon is called Katarchea. It began 4.6 billion years ago and ended 4 billion years ago. Thus, its duration was 600 million years. Time is very ancient, so it was not divided into either eras or periods. At the time of the Katarchean, there was neither the earth's crust nor the nucleus. The planet was a cold space body. The temperature in its interior corresponded to the melting point of the substance. From above, the surface was covered with regolith, as in our time lunar. The relief was almost flat due to constant powerful earthquakes. Naturally, there was no atmosphere or oxygen.

Archaea

The second aeon is called Archean. It began 4 billion years ago and ended 2.5 billion years ago. Thus, it lasted 1.5 billion years. It is subdivided into 4 eras:

eoarcheus

paleoarchean

mesoarchean

neoarchean

Eoarcheus(4-3.6 billion years) lasted 400 million years. This is the period of the formation of the earth's crust. A huge number of meteorites fell on the planet. This is the so-called Late Heavy Bombardment. It was at that time that the formation of the hydrosphere began. Water appeared on Earth. A large number of it could have been brought in by comets. But the oceans were still far away. There were separate reservoirs, and the temperature in them reached 90 ° Celsius. The atmosphere was high in carbon dioxide and low in nitrogen. There was no oxygen. At the end of this era of Earth development, the first supercontinent, Vaalbara, began to form.

Paleoarchean(3.6-3.2 billion years) lasted 400 million years. In this era, the formation of the solid core of the Earth was completed. A strong magnetic field has appeared. His tension was half of the current one. Consequently, the planet's surface received protection from the solar wind. This period also includes primitive forms of life in the form of bacteria. Their remains, which are 3.46 billion years old, were discovered in Australia. Accordingly, the oxygen content in the atmosphere began to increase, due to the activity of living organisms. The formation of Vaalbar continued.

Mesoarchean(3.2-2.8 billion years) lasted 400 million years. The most remarkable thing about it was the existence of cyanobacteria. They are capable of photosynthesis and release oxygen. Completed the formation of the supercontinent. By the end of the era, it split. A huge asteroid also fell. The crater from it still exists in Greenland.

Neoarchean(2.8-2.5 billion years) lasted 300 million years. This is the time of the formation of the real earth's crust - tectogenesis. Bacteria continued to develop. Traces of their life have been found in stromatolites, the age of which is estimated at 2.7 billion years. These limescale deposits were formed by huge colonies of bacteria. They were found in Australia and South Africa... Photosynthesis continued to improve.

With the end of the Archean era, the Earths received their continuation in the Proterozoic eon. This is a period of 2.5 billion years - 540 million years ago. It is the longest of all the eons of the planet.

Proterozoic

The Proterozoic is divided into 3 eras. The first is called paleoproterozoic(2.5-1.6 billion years). It lasted 900 million years. This huge time frame is subdivided into 4 periods:

siderium (2.5-2.3 billion years)

riasius (2.3-2.05 billion years)

orosirium (2.05-1.8 billion years)

staterium (1.8-1.6 billion years)

Siderius remarkable first of all oxygen disaster... It happened 2.4 billion years ago. It is characterized by a radical change in the Earth's atmosphere. Free oxygen appeared in it in huge quantities. Before that, the atmosphere was dominated by carbon dioxide, hydrogen sulfide, methane and ammonia. But as a result of photosynthesis and the extinction of volcanic activity at the bottom of the oceans, oxygen filled the entire atmosphere.

Oxygen photosynthesis is characteristic of cyanobacteria, which proliferated on Earth 2.7 billion years ago.

Before that, archaebacteria prevailed. They did not produce oxygen during photosynthesis. In addition, oxygen was initially consumed for the oxidation of rocks. V large quantities it accumulated only in biocenoses or bacterial mats.

Eventually, the moment came when the surface of the planet turned out to be oxidized. And cyanobacteria continued to release oxygen. And it began to accumulate in the atmosphere. The process has accelerated due to the fact that the oceans also stopped absorbing this gas.

As a result, anaerobic organisms died, and they were replaced by aerobic ones, that is, those in which the synthesis of energy was carried out through free molecular oxygen. The planet was enveloped in the ozone layer and the greenhouse effect decreased. Accordingly, the boundaries of the biosphere expanded, and sedimentary and metamorphic rocks were completely oxidized.

All these metamorphoses have led to Huron glaciation, which lasted 300 million years. It began in sideria and ended at the end of riasia 2 billion years ago. The next period of the Orosirians is notable for its intensive mountain building processes. At this time, 2 huge asteroids fell on the planet. A crater from one is called Vredefort and is located in South Africa. Its diameter reaches 300 km. Second crater Sudbury located in Canada. Its diameter is 250 km.

Last staterian period notable for the formation of the supercontinent Colombia. It includes almost all continental blocks of the planet. There was a supercontinent 1.8-1.5 billion years ago. At the same time, cells were formed that contained nuclei. That is, eukaryotic cells. It was very important stage evolution.

The second era of the Proterozoic is called mesoproterozoic(1.6-1 billion years). Its duration was 600 million years. It is divided into 3 periods:

potassium (1.6-1.4 billion years)

exatia (1.4-1.2 billion years)

stheny (1.2-1 billion years).

During such an era of the Earth's development as potassium, the supercontinent Columbia disintegrated. And at the time of exation, red multicellular algae appeared. This is indicated by a fossil find on the Canadian island of Somerset. Its age is 1.2 billion years. A new supercontinent, Rodinia, was formed in Stania. It arose 1.1 billion years ago, and disintegrated 750 million years ago. Thus, by the end of the Mesoproterozoic, there was 1 supercontinent and 1 ocean on Earth, called Mirovia.

The last era of the Proterozoic is called neoproterozoic(1 billion - 540 million years). It includes 3 periods:

tonium (1 billion - 850 million years)

cryogeny (850-635 million years)

ediacaran (635-540 million years)

During the time of Tony, the disintegration of the supercontinent Rodinia began. This process ended in cryogeny, and the supercontinent Pannotia began to form from 8 separate pieces of land formed. Cryogeny is also characterized by complete glaciation of the planet (Earth-snowball). The ice reached the equator, and after they retreated, the process of evolution of multicellular organisms sharply accelerated. The last period of the Neoproterozoic Ediacaran is notable for the appearance of soft-bodied creatures. These multicellular animals are named Vendobionts... They represented branching tubular structures. This ecosystem is considered to be the oldest.

Life on Earth originated in the ocean

Phanerozoic

Approximately 540 million years ago, the time of the 4th and last eon, the Phanerozoic, began. There are 3 very important eras of the Earth here. The first is called Paleozoic(540-252 million years). It lasted 288 million years. Divided into 6 periods:

Cambrian (540-480 Ma)

Ordovician (485-443 Ma)

Silurian (443-419 Ma)

Devonian (419-350 Ma)

carbon (359-299 million years)

Permian (299-252 million years)

Cambrian is considered the lifetime of trilobites. These are marine animals similar to crustaceans. Together with them, jellyfish, sponges and worms lived in the seas. Such an abundance of living beings is called Cambrian explosion... That is, before that, there was nothing like this and suddenly appeared abruptly. Most likely, it was in the Cambrian that mineral skeletons began to emerge. Earlier, the living world had soft bodies. Naturally, they have not survived. Therefore, complex multicellular organisms of more ancient eras cannot be detected.

The Paleozoic is notable for the rapid dispersal of organisms with rigid skeletons. From vertebrates appeared fish, reptiles and amphibians. V flora at first, algae prevailed. During silurian plants began to master the land. At the beginning devonian swampy shores are overgrown with primitive flora. They were psilophytes and pteridophytes. Plants propagated by spores that were carried by the wind. Plant shoots developed on tuberous or creeping rhizomes.

Plants began to master the land in the Silurian period

Scorpions and spiders appeared. The real giant was the meganera dragonfly. Its wingspan reached 75 cm. Acanthodes are considered the most ancient bony fish. They lived during the Silurian period. Their bodies were covered with dense diamond-shaped scales. V carbon, which is also called the Carboniferous period, on the shores of lagoons and in countless swamps, the most diverse vegetation developed rapidly. It was its remains that served as the basis for the formation of coal.

This time is also characterized by the beginning of the formation of the Pangea supercontinent. It was fully formed in the Permian period. And it broke up 200 million years ago into 2 continents. These are the northern continent of Laurasia and the southern continent of Gondwana. Subsequently, Laurasia split, and Eurasia and North America were formed. And from Gondwana originated South America, Africa, Australia and Antarctica.

On Permian there were frequent climate changes. Dry times gave way to wet ones. At this time, lush vegetation appeared on the banks. Typical plants were kordaites, calamites, tree and seed ferns. Mesosaurus lizards appeared in the water. Their length reached 70 cm. But by the end of the Permian period, the early reptiles became extinct and gave way to more developed vertebrates. Thus, in the Paleozoic, life reliably and densely settled on the blue planet.

The following eras of the Earth's development are of particular interest to scientists. 252 million years ago came Mesozoic... It lasted 186 million years and ended 66 million years ago. Consisted of 3 periods:

Triassic (252-201 Ma)

Jurassic (201-145 Ma)

chalk (145-66 million years)

The border between the Permian and Triassic periods is characterized by the mass extinction of animals. Killed 96% marine species and 70% of terrestrial vertebrates. The biosphere was hit very hard, and it took a very long time to recover. And it all ended with the appearance of dinosaurs, pterosaurs and ichthyosaurs. These sea and land animals were enormous in size.

But the main tectonic event of those years was the collapse of Pangea. A single supercontinent, as already mentioned, divided into 2 continents, and then disintegrated into those continents that we know now. The Indian subcontinent also broke away. Subsequently, it merged with the Asian plate, but the collision was so violent that the Himalayas arose.

This nature was in the early Cretaceous period

The Mesozoic is notable for what is considered the warmest period of the Phanerozoic eon.... This is the time of global warming. It began in the Triassic and ended at the end of the Cretaceous. For 180 million years even in the Arctic there were no stable pack glaciers. Heat spread evenly over the planet. At the equator, the average annual temperature was 25-30 ° Celsius. The subpolar regions were characterized by a moderately cool climate. In the first half of the Mesozoic, the climate was dry, while the second half was characterized by a humid one. It was at this time that the equatorial climatic zone was formed.

In the animal kingdom, mammals arose from the subclass of reptiles. It was related to improvement nervous system and the brain. The limbs moved from the sides under the body, the reproductive organs became more perfect. They ensured the development of the embryo in the mother's body, followed by feeding it with milk. A fur coat appeared, blood circulation and metabolism improved. The first mammals appeared in the Triassic, but they could not compete with dinosaurs. Therefore, for more than 100 million years, they occupied a dominant position in the ecosystem.

The last era is considered cenozoic(beginning 66 million years ago). This is the current geological period. That is, we all live in the Cenozoic. It is subdivided into 3 periods:

Paleogene (66-23 million years)

neogene (23-2.6 million years)

modern anthropogen or Quaternary period, which began 2.6 million years ago.

There are 2 main events in the Cenozoic... Mass extinction of dinosaurs 65 million years ago and a general cooling on the planet. The death of animals is associated with the fall of a huge asteroid with a high content of iridium. The diameter of the cosmic body reached 10 km. As a result, a crater was formed Chicxulub with a diameter of 180 km. It is located on the Yucatan Peninsula in Central America.

Surface of the Earth 65 million years ago

After the fall, an explosion of enormous power occurred. Dust rose into the atmosphere and blocked the planet from sun rays... The average temperature dropped by 15 °. The dust hung in the air for a whole year, which led to a sharp cold snap. And since the Earth was inhabited by large heat-loving animals, they became extinct. Only small representatives of the fauna remained. It was they who became the ancestors of the modern animal world. This theory is based on iridium. The age of its layer in geological deposits corresponds exactly to 65 million years.

During the Cenozoic, the continents diverged. Each of them formed its own unique flora and fauna. The variety of marine, flying and land animals has increased significantly in comparison with the Paleozoic. They became much more sophisticated, and mammals took the dominant position on the planet. Higher angiosperms appeared in the plant kingdom. This is the presence of a flower and ovule. Cereals also appeared.

The most important thing in the last era is anthropogen or quaternary period, which began 2.6 million years ago. It consists of 2 eras: the Pleistocene (2.6 million years-11.7 thousand years) and the Holocene (11.7 thousand years-now). During the Pleistocene era mammoths, cave lions and bears, marsupial lions, saber-toothed cats and many other species of animals that became extinct at the end of the era lived on Earth. A man appeared on the blue planet 300 thousand years ago. It is believed that the first Cro-Magnons chose the eastern regions of Africa for themselves. At the same time, Neanderthals lived on the Iberian Peninsula.

Notable for the Pleistocene and ice ages... As much as 2 million years, very cold and warm periods of time alternated on Earth. Over the past 800 thousand years, there have been 8 ice ages with an average duration of 40 thousand years. In cold times, glaciers advanced on the continents, and retreated in the interglacial period. At the same time, the level of the World Ocean increased. About 12 thousand years ago, already in the Holocene, the next ice age ended. The climate became warm and humid. Thanks to this, humanity has settled throughout the planet.

Holocene is an interglacial... It has been going on for 12 thousand years. For the last 7 thousand years, human civilization has been developing. The world has changed in many ways. The flora and fauna have undergone significant transformations due to human activity. Nowadays, many species of animals are on the verge of extinction. Man has long considered himself the ruler of the world, but the eras of the Earth have not gone anywhere. Time continues its steady pace, and the blue planet conscientiously revolves around the Sun. In a word, life goes on, but what will happen next - the future will show.

Is a collection of all forms of the earth's surface. They can be horizontal, inclined, convex, concave, complex.

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

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

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

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

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

Table 1. Geochronological table

Era. letter designation, duration	The main stages of life development	Periods, letter designation, duration	Major geological events. The appearance of the earth's surface	The most common minerals
Cenozoic, KZ, about 70 million years old	Dominance of angiosperms. The flourishing of the mammalian fauna. The existence of natural zones close to modern ones, with repeated displacements of boundaries	Quaternary, or anthropogenic, Q, 2 Ma	General uplift of the territory. Repeated glaciation. The appearance of man	Peat. Placer deposits of gold, diamonds, precious stones
		Neogene, N, 25 Ma	The emergence of young mountains in the areas of Cenozoic folding. Revival of mountains in areas of all ancient folds. Dominance of angiosperms (flowering) plants	Brown coals, oil, amber
		Paleogene, P, 41 Ma	Destruction of the Mesozoic mountains. Widespread distribution of flowering plants, development of birds and mammals	Phosphorites, brown coals, bauxite
Mesozoic, MZ, 165 Ma		Cretaceous, K, 70 Ma	The emergence of young mountains in areas of Mesozoic folding. Extinction of giant reptiles (reptiles). Development of birds and mammals	Oil, oil shale, chalk, coal, phosphorites
Mesozoic, MZ, 165 Ma		Jurassic, J, 50 Ma	Formation of modern oceans. Hot, humid climate. The rise of reptiles. Domination gymnosperms... The emergence of primitive birds	Bituminous coals, oil, phosphorites
		Triassic, T, 45 Ma	The largest retreat of the sea and the uplift of continents in the history of the Earth. Destruction of the pre-Mesozoic mountains. Vast deserts. First mammals	Rock salt
Paleozoic, PZ, 330 Ma	The flowering of ferns and other spore plants. Time of fish and amphibians	Perm, R, 45 Ma	The emergence of young mountains in the areas of the Hercynian folding. Dry climate. The emergence of gymnosperms	Rock and potassium salts, gypsum
		Carboniferous (Carboniferous), C, 65 Ma	Widespread swampy lowlands. Hot, humid climate. The development of forests of tree ferns, horsetails and lyres. The first reptiles. The flowering of amphibians	Abundance of coal and oil
		Devonian, D, 55 million	Decrease in the area of the seas. Hot climate. The first deserts. The emergence of amphibians. Numerous fish	Salts, oil
	The appearance of animals and plants on Earth	Silurian, S, 35 Ma	The emergence of young mountains in the areas of the Caledonian folding. The first land plants
		Ordovician, Oh, 60 Ma	Reduction of the area of sea basins. The appearance of the first terrestrial invertebrates
		Cambrian, E, 70 Ma	The emergence of young mountains in the areas of Baikal folding. Flooding of vast spaces by seas. The flourishing of marine invertebrates	Rock salt, gypsum, phosphorites
Proterozoic, PR. about 2000 million years	The origin of life in water. Time of bacteria and algae		The beginning of the Baikal folding. Powerful volcanism. Time of bacteria and algae	Huge reserves of iron ore, mica, graphite
Archean, AR. more than 1000 million years			The oldest folds. Intense volcanic activity. Time of primitive bacteria	Iron ore

Zones are divided into era. Cryptozoic distinguishes Archean(from the Greek. archaios- the original, the most ancient, aion - century, era) and proterozoic(from the Greek. proteros - earlier, zoe - life) era; in the Phanerozoic - paleozoic(from the Greek. ancient and life), Mesozoic(from the Greek. tesos - medium, zoe - life) and Cenozoic(from the Greek. kainos - new, zoe - life).

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

The main stages of the development of the geographic envelope

The geographic envelope has passed a long and difficult path of development. Three qualitatively different stages are distinguished in all development: prebiogenic, biogenic, anthropogenic.

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

At this stage of development, the Earth's atmosphere contained very little oxygen, and there was no ozone shield.

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

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

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

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

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

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

The thesis about the evolution of the Earth, as an exceptional object of its kind in the cosmos, occupies the main stage. 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, geological time counting. The above specialized science is subdivided 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 decay rate of isotopes of radioactive components. This speed is extremely constant and free from the saturation of physical and chemical currents. Age designation is organized in ways that are associated with nuclear physics. Minerals, which contain radioactive components, generate a closed structure when arranging crystal lattices. It is in such a structure that the process of accumulation of elements is carried out. radioactive decay... Therefore, if you have information about the speed of the presented process, then 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 take place over a period of time that is ten times the half-life. Nuclear geochronology has basic methods, namely: lead, potassium-argon, rubidium-strontium and radiocarbon.

It was the presented methods of nuclear geochronology that contributed to the determination 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 presented another method of setting the time, which was called radiological. Relative geochronology carries out activities to determine the relative age of rocks. That is, which accumulations in the earth's crust are younger and which are ancient.

The specialization of relative geochronology is made up of such theses as “early, middle and late age”. A number of techniques for identifying the relative age of rocks have scientific substantiation. It seems possible to divide these methods into two groups. These groups are called paleontological and non-paleontological. Paleontological methods are at the forefront because they are more versatile and widely applied. There are, of course, exceptions. Such a rare case is the lack of natural accumulations in the rocks. They use the presented method when studying fragments of extinct ancient organisms. It should be noted that each rock stratum is characterized by a specific set of natural residues. 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 absolute geochronology is engaged in concretely determining the age in units of time. The purpose of geological time is to discover the temporal chronology of geological phenomena.

Geochronological table

In order to establish age criteria for rocks, scientists use a wide variety of methods. Therefore, it was advisable to create a highly specialized scale for ease of use. Geological time according to this scale is divided into time intervals. A specific 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 contains such subgroups as, eon, era, period, era, century, time. It should be noted that each group is characterized by a certain set of savings. Such an aggregate, in turn, is called a stratigraphic complex, which also has a number of types, namely: eonotema, group, system, department, stage, zone. For example, the system belongs to the stratigraphic category, and the temporary 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 in cases where accumulations in rocks are investigated. Since at any time any geological processes are taking place on the planet. The geochronological scale is used to establish relative times. Since the time the scale was approved, its structure has undergone many changes.

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

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

Archeos is the oldest;
Proteros is primary;
Paleos is ancient;
Mesos - medium;
Kainos is 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 eras 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, these eras are divided into periods. The number of these time intervals is 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 span 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 took place. By this time period, there were already rocks on the planet and the processes of erosion and accumulation of sediments began. 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, the depths were raised, which contributed to the formation of mountains. Unfortunately, most of the fossils were destroyed, but some general information about this era is still preserved. In rocks that existed in the Archean era, scientists have discovered carbon in pure form... Experts believe that these are modified remains of living organisms. In view of the fact that the amount of graphite speaks about the amount of living matter, then in this era there was a lot of it.

Proterozoic era. In terms of time, this is the next period, which contains one billion years. During this epoch, precipitation accumulated and one global glaciation occurred. The fossils that were found in the mountain layers of this time are the main witnesses to the fact that life existed and went through stages of evolution. 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;
Silurian;
Devonian;
Carbon / Coal;
Perm / Perm;

The time span of the Paleozoic era spans 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 bulk of the continents rose above sea level. Climatic conditions gradually changed and became warmer. Arizona has a popular stone forest that has been around since the Triassic period. During the last period, a power-law rise of the sea takes place. The North American continent was completely submerged, as a result of which the Gulf of Mexico joined the Arctic Basin. The end of the Cretaceous period is characterized by the fact that there were large uplifts of the earth's crust. This is how the Rocky Mountains, Alps, Himalayas, 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 become isolated. Two Americas merged. This time period was identified by J. Denoyer in 1829. main feature consists in the fact that a person has appeared.

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

We present to your attention an article on the classical understanding of the development of our planet Earth, written not boring, understandable and not too long ... .. If any of the people of mature age have forgotten a little, it will be interesting to read, well, for those who are younger, and even for an abstract in general, wonderful material ...

In the beginning there was nothing. In the endless outer space, there was only a giant cloud of dust and gases. It can be assumed that from time to time, space ships with representatives of the universal mind rushed through this substance at great speed. The humanoids looked bored through the windows and did not even remotely suspect that in a few billion years, intelligence and life would arise in these places.

The cloud of gas and dust eventually transformed into the solar system. And after the star arose, the planets appeared. Our native land became one of them. It happened 4.5 billion years ago. It is from those distant times that the age of the blue planet has been counted, thanks to which we exist in this world.

The entire history of the Earth is divided into two huge stages in time.

The first stage is characterized by the absence of complex living organisms. There were only unicellular bacteria that settled on our planet about 3.5 billion years ago.
The second stage began about 540 million years ago. This is the time when living multicellular organisms spread across the Earth. This refers to both plants and animals. Moreover, both the sea and the land became their habitat. The second period continues to this day, and man is its crown.

Katarchei

Archaea

The second aeon is called Archean. It began 4 billion years ago and ended 2.5 billion years ago. Thus, it lasted 1.5 billion years. It is subdivided into 4 eras:

eoarcheus
paleoarchean
mesoarchean
neoarchean

Eoarcheus(4–3.6 billion years) lasted 400 million years. This is the period of the formation of the earth's crust. A huge number of meteorites fell on the planet. This is the so-called Late Heavy Bombardment. It was at that time that the formation of the hydrosphere began. Water appeared on Earth. A large number of it could have been brought in by comets. But the oceans were still far away. There were separate reservoirs, and the temperature in them reached 90 ° Celsius. The atmosphere was high in carbon dioxide and low in nitrogen. There was no oxygen. At the end of this era of Earth development, the first supercontinent, Vaalbara, began to form.

Paleoarchean(3.6–3.2 billion years) lasted 400 million years. In this era, the formation of the solid core of the Earth was completed. A strong magnetic field has appeared. His tension was half of the current one. Consequently, the planet's surface received protection from the solar wind. This period also includes primitive forms of life in the form of bacteria. Their remains, which are 3.46 billion years old, were discovered in Australia. Accordingly, the oxygen content in the atmosphere began to increase, due to the activity of living organisms. The formation of Vaalbar continued.

Mesoarchean(3.2–2.8 billion years) lasted 400 million years. The most remarkable thing about it was the existence of cyanobacteria. They are capable of photosynthesis and release oxygen. Completed the formation of the supercontinent. By the end of the era, it split. A huge asteroid also fell. The crater from it still exists in Greenland.

Neoarchean(2.8–2.5 billion years) lasted 300 million years. This is the time of the formation of the real earth's crust - tectogenesis. Bacteria continued to develop. Traces of their life have been found in stromatolites, the age of which is estimated at 2.7 billion years. These limescale deposits were formed by huge colonies of bacteria. They were found in Australia and South Africa. Photosynthesis continued to improve.

Proterozoic

The Proterozoic is divided into 3 eras. The first is called paleoproterozoic(2.5-1.6 billion years). It lasted 900 million years. This huge time frame is subdivided into 4 periods:

siderium (2.5-2.3 billion years)
riasius (2.3-2.05 billion years)
orosirium (2.05-1.8 billion years)
stateria (1.8-1.6 billion years)

Oxygen photosynthesis is characteristic of cyanobacteria, which proliferated on Earth 2.7 billion years ago. Before that, archaebacteria prevailed. They did not produce oxygen during photosynthesis. In addition, oxygen was initially consumed for the oxidation of rocks. In large quantities, it accumulated only in biocenoses or bacterial mats.

The second era of the Proterozoic is called mesoproterozoic(1.6-1 billion years). Its duration was 600 million years. It is divided into 3 periods:

potassium (1.6-1.4 billion years)
exatia (1.4-1.2 billion years)
sthenia (1.2-1 billion years).

The last era of the Proterozoic is called neoproterozoic(1 billion - 540 million years). It includes 3 periods:

tonium (1 billion - 850 million years)
cryogeny (850-635 million years)
Ediacaria (635-540 Ma)

Life on Earth originated in the ocean

Phanerozoic

Cambrian (540-480 Ma)
Ordovician (485–443 Ma)
Silurian (443-419 Ma)
Devonian (419-350 Ma)
carbon (359-299 Ma)
Permian (299-252 million years)

The Paleozoic is notable for the rapid dispersal of organisms with rigid skeletons. From vertebrates appeared fish, reptiles and amphibians. In the plant world, algae predominated at first. During silurian plants began to master the land. At the beginning devonian swampy shores are overgrown with primitive flora. They were psilophytes and pteridophytes. Plants propagated by spores that were carried by the wind. Plant shoots developed on tuberous or creeping rhizomes.

Plants began to master the land in the Silurian period

Triassic (252–201 Ma)
Jurassic (201-145 Ma)
chalk (145-66 million years)

The border between the Permian and Triassic periods is characterized by the mass extinction of animals. Killed 96% of marine species and 70% of terrestrial vertebrates. The biosphere was hit very hard, and it took a very long time to recover. And it all ended with the appearance of dinosaurs, pterosaurs and ichthyosaurs. These sea and land animals were enormous in size.

This nature was in the early Cretaceous period

In the animal kingdom, mammals arose from the subclass of reptiles. This was due to the improvement of the nervous system and the brain. The limbs moved from the sides under the body, the reproductive organs became more perfect. They ensured the development of the embryo in the mother's body, followed by feeding it with milk. A fur coat appeared, blood circulation and metabolism improved. The first mammals appeared in the Triassic, but they could not compete with dinosaurs. Therefore, for more than 100 million years, they occupied a dominant position in the ecosystem.

The last era is considered cenozoic(beginning 66 million years ago). This is the current geological period. That is, we all live in the Cenozoic. It is subdivided into 3 periods:

Paleogene (66-23 million years)
Neogene (23-2.6 million years)
modern anthropogen or Quaternary period, which began 2.6 million years ago.

Surface of the Earth 65 million years ago

After the fall, an explosion of enormous power occurred. Dust rose into the atmosphere and blocked the planet from the sun's rays. The average temperature dropped by 15 °. The dust hung in the air for a whole year, which led to a sharp cold snap. And since the Earth was inhabited by large heat-loving animals, they became extinct. Only small representatives of the fauna remained. It was they who became the ancestors of the modern animal world. This theory is based on iridium. The age of its layer in geological deposits corresponds exactly to 65 million years.

The most important thing in the last era is anthropogen or quaternary period, which began 2.6 million years ago. It consists of 2 eras: the Pleistocene (2.6 million years – 11.7 thousand years) and the Holocene (11.7 thousand years – present). During the Pleistocene era mammoths, cave lions and bears, marsupial lions, saber-toothed cats and many other species of animals that became extinct at the end of the era lived on Earth. A man appeared on the blue planet 300 thousand years ago. It is believed that the first Cro-Magnons chose the eastern regions of Africa for themselves. At the same time, Neanderthals lived on the Iberian Peninsula.

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 appears a large number of living organisms with mineral skeletons. 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. Most significant events this aeon - the Cambrian explosion that occurred about 540 million years ago and the five largest extinctions in the history of the planet.

Eras of the Precambrian Aeon

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

The Proterozoic consists of three great eras:

Paleoproterozoic- that is, the ancient one, which includes the Siderius, the Riasian period, the 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:

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

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

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

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

Tertiary. At the beginning of the period, predators and ungulates reach their dawn, the climate is warm. The forest spreads to its maximum extent, and the most ancient mammals are dying out. Approximately 25 million years ago, humans appear and in the Pliocene epoch.
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.