The accumulated materials on the geological structure of the earth's crust and the development of life made it possible to divide its geological history into six eras and draw up a scale of geological time - a geochronological scale.

Each era is divided into periods, period into eras, eras into centuries.

Archean era - the era of the beginning of life

Proterozoic era - the era of primary life

Riphean - the era of early life

Palaeozoic ancient life

Mesozoic - era average life

Cenozoic - the era of modern life.

The eras are united into two eons by Kryptose and Phanerosa.

Croptozoic unites the Archean, Proterozoic and Riphean eras. This eon accounts for almost 4 billion years, or 5/6 of the entire geological chronology.

This is the time of the origin of life, the appearance of primitive unicellular organisms. The skeletal fauna is completely absent.

They are characterized by active tectonic activity, as a result of which the geological structure of the earth's crust was formed, the appearance of water and the first simplest forms of life, and the accumulation of the first thick layers of sedimentary rocks. First, the platforms of the northern hemisphere and the Australian were formed, later the Hindustan, South American, African and Antarctic. At the same time, the first geosynclines (folded mountains) took shape.

The geological formations of these eras are represented by igneous, ancient sedimentary and metamorphic rocks: crystalline schists, limestones, marbles, etc. In a non-weathered state, these rocks are a good foundation and good building materials. They form the crystalline foundation of the Russian, West Siberian and other plains, come to the surface in our country south of Voronezh, in Karelia, the Murmansk region, in Eastern Siberia, in the Urals, in Central Asia and in Altai.

Other eras - Pleozoic, Mesozoic and Cenozoic - are combined into the Phanerozoic (approximately 570 million years). Phaenerozoic is the most important stage in the geological history of the Earth, which is characterized by the emergence and wide development of skeletal organisms, the flourishing of the organic world and the emergence of man.

Palaeozoic-Pz began about 525-570 million years ago and lasted about 340 million years. The Paleozoic era is divided into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. If necessary, changes were introduced into the standard stratigraphic scale, reflecting regional specifics. For example, in Europe there is a Carboniferous period, and in the USA two correspond to it - Mississippi and Pennsylvania.

The Paleozoic era is distinguished mainly by a very warm and humid subtropical climate, which led to the formation of many rocks of organogenic origin. During this period, two major phases of mountain building occurred, accompanied by intense crushing rocks. The first, Caledonian phase took place on the territory of Scotland, Western Scandinavia, Greenland, on the territory of Russia, this is the region of Transbaikalia. During the second, Hercynian phase, the Ural Mountains, Tien Shan, Altai, etc. were formed. In the era of rock formation, the tropical climate was replaced by a sharp cooling, and during the era of the Hercynian phase, glaciation even occurred.

In the Paleozoic era, limestones, marls, dolomites were formed in the seas, on the continents - clays, sands and sandstones. In the last periods of the Paleozoic - Carboniferous and Permian - powerful deposits of coal, limestones, sandstones, shales, as well as chemical sedimentary rocks - gypsum, anhydrite, rock salt were formed. The rocks formed during this era contain many remains of fauna and flora. The forms were primitive and very far from modern, these are spore plants and invertebrates, and subsequently extinct vertebrates.

Most of the rocks of the Paleozoic era can serve as a reliable foundation and be used as building materials.

Mesozoic era Mz (the era of middle life) began 190 million years ago and had a duration of about 125 million years, divided into three periods Triassic, Jurassic and Cretaceous. The era is distinguished by a relatively warm, uniform climate and tectonic calm. Only in the Jurassic period did the Cimmerian phase of mountain building take place, as a result of which the formation of the Caucasus and Crimean mountains began. At the same time, a continental climatic situation is observed, in which coals and clays were formed.

During the Mesozoic, marine and continental deposits were equally distributed. Within the Russian plain, powerful deposits of chalk, limestone, and clay were formed. The possibilities of using the rocks of the Mesozoic era for construction purposes are the same as in the Paleozoic period.

During this era, reptiles were very large. Fauna and flora were of a transitional nature - from ancient forms of the organic world to modern ones.

Cenozoic erakz(era of new life) began 65 million years ago. The flora and fauna are approaching modern forms, a person appears. The era is divided into three periods: Paleogene, Neogene and Quaternary. The first two periods are usually combined into one - the tertiary. The Quaternary period takes only 1 million years and has been studied in the most detail. It was at the beginning of the Quaternary period that man appeared.

The Cenozoic era is distinguished by different, sharply different climatic conditions. During the Paleogene period, the climate was warm, almost tropical, during the Neogene period, cooling is observed, which in the Quaternary period turned into an ice age with periodic glaciations. Glaciations captured a vast territory of the northern part of Europe and Asia.

In the Cenozoic era, the so-called Alpine folding, the formation of which began as early as the Jurassic, was very intensively manifested. In the Tertiary period, the formation of the Caucasus and Crimean mountains ended. At the same time, the ridges of North Africa, the Alps, the Carpathians, the Pamir, Tien Shan, Himalev, the Kuril Islands, Sakhalin Kamchatka appeared. The Alpine orogenic phase has not ended yet.

In the Tertiary period, rocks of marine and continental origin were formed. Tertiary marine deposits - clays, shell limestones, etc. are located on the Black Sea coast and in other places. Continental Tertiary deposits are ubiquitous.

The overwhelming majority of rocks of the Quaternary period are continental deposits - loose rocks and rocks of organogenic origin. They are usually called Quaternary rocks or alluvial rocks, in contrast to the earlier rocks, which I call bedrock. Marine Quaternary deposits are rare in Russia - on the coasts of the seas, to the north and east of the Caspian Sea and on the northern coast of the Black Sea. The composition and properties of these deposits are similar to those of the Tertiary. Marine silts form a special group among them.

The thickness of Quaternary deposits varies from a few centimeters to tens and hundreds of meters. These rocks are less reliable as bases than roots. Their properties vary widely and largely depend on genetic characteristics.

The bedrocks are usually represented by rocky and compacted sandy and clayey rocks, and among the Quaternary deposits loose formations, weakly cemented and cohesive, predominate.

Akron (acrotheme)	Aeon (eonoteme)	Era (erathema)	Period (system)	Epoch (the Department)	completion, years ago	Tectonic cycles	Main developments
	fz Phanerozoic	kz Cenozoic	Quaternary	Holocene	Continues these days	Alpine cycle There are only 2 belts on Earth. The Tethys Ocean disappears. From the end of the Neogene, ice cover begins in Antarctica. Tt.o. Neogene - the largest geocratic period of the Earth. The area of ​​the continents was larger than modern. All shelf zones were part of the continents.	Extinction of many large mammals.
				Pleistocene	11 400		The emergence of modern man.
			Neogene	Pliocene	1.81 million
				Miocene	5.33 million
			Paleogene	Oligocene	23.0 million		Appearance of the first great apes.
				Eocene	37.2 million		The emergence of the first "modern" mammals.
				Paleocene	55.8 million
		mz Mesozoic	Chalky		66.5 million	Pacific cycle On Earth there is 1 continent, 2 oceans and 3 belts. The dominance of land on Earth, the climate is hot dry. The split of Gondwana completely.	The first placental mammals. Dinosaur extinction.
			Jurassic		146 million		The appearance of marsupials and the first birds. The rise of the dinosaurs.
			Triassic		200 million		The first dinosaurs and egg-laying mammals.
		pz Paleozoic	Permian		251 million	Herzing cycle In the Carboniferous, a new supercontinent, Angarida, at that time Eria and Gondwana already existed. Eria + Angarida = Laurasia Laurasia + Gondwana = Pangea But immediately a split begins (at the end of Perm). At the end of Perm, the first great extinction of organisms.	About 95% of all existing species died out.
			Coal		299 million		The appearance of trees and reptiles.
			Devonian		359 million		The appearance of amphibians and spore plants.
			S Silurian		416 million	Caledonian cycle At this stage, there were 6 ancient platforms on Earth. The largest transgression with max in the Ordovician, Gondwana remains dry land. At the beginning of the Silurian - glaciation. At the end of the Caledonian phase, the supercontinent Eria formed.	Exit of life to land: scorpions and later the first plants. The appearance of fish.
			O Ordovician		443 million		The pelagial is inhabited by cephalopods
			E Cambrian		488 million		The emergence of a large number of new groups of organisms.
PR Proterozoic	Riphean (Neoproterozoic)		Ediacarus (obsolete Vendian)		542 million	Baikal cycle 5 geosynclinal belts are laid. Formed Pacific Ocean(800 million years ago) At the end of the Riphean, all continents are connected southern hemisphere- Gondwana. The climate is warm everywhere, at the end of the Riphean glaciation. The atmosphere is saturated with oxygen (1% of the current level)	The first multicellular animals.
			cryogeny		600 million
			Tony		850 million
	Late (Mesoproterozoic)		Stenius		1.0 billion
			Ectasia		1.2 billion
			potassium		1.4 billion
	Early (Paleoproterozoic)		Statery		1.6 billion	Karelian cycle Revolutionary stage. At the end of it, huge sections of the ZK become rigid and stable. Real platforms are being formed.
			Orosirium		1.8 billion
			Riasius		2.05 billion
			siderius		2.3 billion
AR archaeus	Late		neoarchean		2.5 billion	White Sea cycle Formation of a real continental ZK.
			Mesoarchean		2.8 billion
	Early		paleoarchaean		3.2 billion	Soami cycle On Earth, a hydrosphere is formed, which is represented by shallow oceans, in the form of islands there are cores of the protocontinental crust.
			Eoarchean		3.6 billion		The emergence of primitive unicellular organisms.
					3.8 billion	Early geological stage The Earth is formed as a result of rotation. Substance differentiation begins. A basaltic crust is formed, but it is phantom.	Formation of the Earth 4.57 billion years ago

Geological table

This is a list of time divisions or intervals, in the order of their hierarchy.

Chronometric scale

This is an isotopic age scale based on the radioactive decay of elements, from their formation to the present day.
Akron is a time interval lasting 2 billion years.
Eon - a gap of 1 billion years.
An era is hundreds of millions of years.
Period - tens of million years
Epoch - tens of millions of years.

Stratigraphic scale

This is the rock scale. Represents a complete perfect section of the Earth's crust

See also: Evolution of the geographic shell of the earth, Geochronological scale (original article).

The evolution of living beings can only be understood in the context of geological time.

Geochronological (stratigraphic) timeline - this is a scale of relative geological time, built on the basis of the stages of formation of the earth's crust and life on the planet, determined by paleontology and historical geology. It is a sequence of stratigraphic elements in the order of their formation, in the form of a complete composite ideal section of all terrestrial deposits without gaps and overlaps, and is a standard for the correlation of any stratigraphic units. The boundaries between stratigraphic elements are drawn by events of marked evolutionary or geological change. The doctrine of the chronological sequence of formation and age of the rocks that make up the earth's crust is called geochronology .

Distinguish between relative and absolute geochronology.

task relative geochronology is the determination of the relative age of rocks: determining which deposits found in the earth's crust are older and which are younger. There are several methods for determining the relative age of rocks.

First method - stratigraphic. He proceeds from the completely unclear and logical notions that each layer of sedimentary rocks was formed before the layer that overlies it.

Second method - paleontological. It allows you to establish the relative age of rocks and compare them in geological sections belonging to different areas or regions. Establishment is made according to the nature of various organic remains found in the layers (petrified sea shells, animal bones, leaf prints, etc.).

task absolute geochronology is to determine the true duration of individual periods and epochs in the life of the Earth, as well as its geological age as a whole.

The geochronological age of rocks is determined by units such as era, period, epoch, and century.

Era - the largest stage in the history of the development of the Earth, in which a group of deposits was formed. There are five eras (starting from the more ancient ones): Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic.

Each era covers several periods. The period corresponds to the time of formation of the rock system. The periods are subdivided into several epochs, which correspond to rock divisions. Epochs are subdivided into centuries, which correspond to tiers as a set of rocks formed in a particular century.

Archean(era of primary life) and Proterozoic(era of ancient life) era farthest from us in time (about 1.5 billion years). At this time, the most ancient rocks were formed that make up the rigid foundation of the earth's crust. The rocks of the Archean era bear only traces of primitive organic forms, testifying to the origin of life on Earth at this time. The Proterozoic era coincides in time with the beginning of the development of various algae, bacteria and invertebrates on Earth.

Palaeozoic(era of ancient life) - a period of time removed from us by about 600 million years and lasting about 350 million years. This era and the breeds related to it have been studied in more detail. The Paleozoic era is characterized by a violent flourishing organic life in the seas and oceans and its access to land. On land, large amphibians become dominant, and at the end of the era, the first reptiles. In the Carboniferous period of the era, tree-like ferns, horsetails, etc.

The Paleozoic era is divided into six periods (starting from the more ancient ones): Cambrian (Cm), Ordovician (O), Silurian (S), Devonian (D), Carboniferous (C) and Permian (P).

Mesozoic era(the era of average life) lasting 185 million years is the heyday of giant reptiles on land (giant lizards - dinosaurs, flying pterodactyls, etc.). The flora and insect world in the Mesozoic have some features in common with our time. At this time, the first representatives of mammals and birds appeared on Earth, which developed in the next, Cenozoic era.

The Mesozoic era is divided into three periods: Triassic (T), Jurassic (J) and Cretaceous (Cr).

Cenozoic era(era of new life) - the youngest (about 40 ... 50 million years BC), replacing mesozoic era. Life at this time takes on forms that are closer and closer to our time.

The Cenozoic era is divided into three periods: Paleogene (Pg), Neogene (N) and Anthropogenic (Ap), or Quaternary (Q). The Quaternary period is the last period in the development of the organic world, during which man appeared.

Rocks up to the Quaternary age are called indigenous, and the continental Quaternary age - coverslips. Within bedrocks, in general, older rocks are more durable than younger ones, while Quaternary cover formations are less durable than bedrocks. But there is no direct connection between the age of rocks and their strength, and sometimes young rocks are more durable than ancient ones.

As a result of studying the age, composition, conditions of occurrence and distribution of rocks, geological maps are compiled that show the outcrops of bedrocks on the surface of the earth. Deposits of the Quaternary time on geological maps, as a rule, do not show; for them, special maps of Quaternary (cover) deposits are compiled. They do this for the reason that the rocks until the Quaternary in the vast majority of cases are of marine origin and are distinguished by a well-identified regularity in the structure of the layers, both in plan and in depth. The rocks of the Quaternary age, on the contrary, in most cases are of continental origin (formed within the land). These rocks are characterized by an extremely variable composition, and the boundaries of their distribution are usually determined by the existing terrain.

For four and a half billion years, the Earth has been revolving around the Sun. Of course, our planet has not always been the way it is now. The face of the Earth, like the face of a living being, ages with age. The composition of the oceans and atmosphere changes, mountains grow and collapse, seas arise and dry up, rivers pave their way new way and cut deep canyons in the ancient mountains. And under the influence of these global changes, life on Earth is also changing. Whatever events took place on Earth, plants, animals and microorganisms managed to adapt to new conditions. How do we know about this? History is the science of humanity. Geology and paleontology (the science of fossils) tell about the origin of the Earth and the development of life on it. People do paleontology to answer one of the fundamental questions: how did the things we see around us come about? What path did our planet go through and how did life develop on it? How did it all come to current state ? Everywhere around us we see traces of the history of the Earth. Here is a mountain range that was once the bottom of the ocean - raised as a result of tectonic processes, eaten away by water and wind, crumpled by glaciers and destroyed by earthquakes. Traces of evolution can also be found in the human body. Many internal organs (primarily the kidneys and the hormonal system) create a liquid brackish environment inside our body, reminding us that once our ancestors lived in the seas. There are two bones in the forearms and shins - a long time ago, in those days when our ancestors learned to move on land, such a structure helped to rotate the limbs. In the human embryo at the intrauterine stages of development, gills appear and then disappear. This evidence of human origins amaze both paleontologists and you and me. The "Atlas of Dinosaurs" consistently outlines all the changes that have occurred over the long history of the Earth. The book begins with a series of excellent maps based on painstaking geological research. They show how the continents have moved over the past 620 million years. Each map is then supplemented with a story about fossils, giving an idea of ​​what plants and animals lived in this era in the sea and on land. In the last, informative part, the complex ideas and principles on which modern geology and paleontology are built are presented in an understandable language. It is worth noting that the scientific study of the Earth in the modern sense of the word began only about two hundred years ago. In those years, there were many "theories" that tried to explain why the stones are so different in shape and composition. Only over time, scientists recognized that fossils are the remains of organic life, and not the creations of human hands or a joke of nature. And after the English scientist William Smith created the science of stratigraphy, it became clear that the fossilized sea shells that are sometimes found in the mountains were not brought there by the waves of the Flood, as previously thought. These findings are explained by the system of geological formations - the layers that make up the rocks around the world. Then scientists faced another problem: how to determine the age of rocks? Obviously, the rocks located at a depth are older than the upper ones, but in almost all regions of the world only separate fragments of the complete sequence are represented. And only after the discovery of radioactivity was created a method based on measuring the decay period of isotopes. This method made it possible to determine the age of rocks to within millions of years, although Darwin and many geologists had made fairly accurate calculations decades earlier.

And finally, scientists had to solve one more problem: how did modern continents take their current places? This question was answered by the theory of continental drift. At first, it was expressed as a bold assumption, then it took shape as a hypothesis, and today, on its basis, the theory of lithospheric plate tectonics, the fundamental concept of modern geology, has been developed. Thanks to it, we know about the movement of continents, about how continental plates move and collide with each other, how oceans arise and disappear again, and we also understand that earthquakes, volcanic eruptions, "hot zones" of the earth's crust and mountain building are manifestations of one and the same process - tectonics. This theory has helped to test many pre-existing ideas about the origin and subsequent change of the atmosphere, oceans, the Earth itself and life on it.

Q

The geochronological scale is represented by the sequence of the history of the Earth, subdividing it into a system of time intervals. It reflects the relative age of sedimentary rock layers, determined from their relative position and the presence of organic residues.

History of creation

The geochronological scale was compiled and approved in 1881 at the International Geological Congress. Initially, it was a sequence of periods divided into epochs. The latter were combined into eras. That is, the original scale included three divisions. Later, a fourth, larger category, the eon, was introduced. In 2004, the International Union of Geological Sciences approved the one developed by the International Commission on Stratigraphy.

In Russia, the geochronological scale, combined with the stratigraphic one, was approved at the end of the 20th century. (1992). At the same time, an even larger division was added - acrons.

Basic principles

The geochronological scale is based on the division of sedimentary rocks or associated igneous massifs by relative age.

Its definition refers to the tasks of geochronology. For this purpose, methods of paleontology and stratigraphy are used.

Application

The use of the geochronological scale is determined by the fact that it relates geological events in the history of the planet. In view of this, it is widely used in the sciences of the geological cycle. In addition, the stratigraphic scale is the basis for compiling geological maps.

In addition, the geochronological scale has a large practical value. Thus, it is used in regional geological studies aimed at clarifying the tectonic features of the territory, determining the direction of prospecting and exploration of minerals, especially those associated with reservoir deposits corresponding to specific stratigraphic levels. Geological maps created on the basis of the geochronological scale are used in engineering and geological work, environmental studies, etc.