Geochronological scale
CLARKEY
Relief
Geographic pole
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This term has other meanings, see Pole.
Geographic pole- the point at which the Earth's axis of rotation intersects the Earth's surface. There are two geographical poles: the North Pole - located in the Arctic (the central part of the Arctic Ocean) and the South Pole - located in Antarctica.
All meridians converge at the geographic pole, and therefore the geographic pole has no longitude. The north pole has a latitude of +90 degrees, and the south pole has a latitude of −90 degrees.
There are no cardinal directions at the geographic poles. There is no change of day and night at the poles, since the poles do not participate in the daily rotation of the Earth.
At the geographic pole, the angle of elevation of the Sun does not exceed 23.5°, which is why the temperature at the pole is very low.
The position of the geographic poles is conditional, since the instantaneous axis of rotation of the Earth moves. Because of this, the movement of geographical poles occurs.
[edit]See Also
Magnetic pole- a conventional point on the earth’s surface at which the earth’s magnetic field is directed strictly at an angle of 90° to the surface.
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Material from Wikipedia - the free encyclopedia
This term has other meanings, see Relief (meanings).
Layout with terrain relief
Relief(fr.
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relief, from lat. relevo- lift) - a set of irregularities on land, the bottom of oceans and seas, varied in outline, size, origin, age and history of development. It is made up of positive (convex) and negative (concave) shapes.
Relief is formed mainly as a result of long-term simultaneous effects on the earth's surface of endogenous (internal) and exogenous (external) processes. Relief is studied by geomorphology.
The main forms of relief are mountain, basin, ridge, and hollow.
On large-scale topographic and sports maps, the relief is depicted with isohypses - horizontal lines, numerical marks and additional symbols. On small-scale topographic and physical maps, relief is indicated by color (hypsometric coloring with clear or blurred steps) and shading.
Denudation plains appear on the site of destroyed mountains.
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Accumulative plains are formed during the long-term accumulation of layers of loose sedimentary rocks at the site of extensive subsidence of the earth's surface.
Fold mountains are uplifts of the earth's surface that arise in moving zones of the earth's crust, most often at the edges of lithospheric plates. Block mountains arise as a result of the formation of horsts, grabens and the movement of sections of the earth's crust along faults. Folded block mountains appeared on the site of sections of the earth's crust that in the past underwent mountain building, transformation into a denudation plain, and repeated mountain building. Volcanic mountains are formed during volcanic eruptions.
Hypsographic curve(from ancient Greek ὕψος - ʼʼheightʼʼ and γράφω ʼʼI writeʼʼ, also hypsometric curve) - empirical integral function of distribution of ocean depths and heights of the earth's surface. It is usually depicted on a coordinate plane, where the height of the relief is plotted along the vertical axis, and the proportion of the surface whose relief height is greater than the specified one is plotted along the horizontal axis. The part of the curve located below sea level is called the bathygraphic curve.
The hypsographic curve was first constructed in 1883 by A. Lapparan and refined in 1933 by E. Kossina. Refinements for the bathygraphic curve were made in 1959 by V. N. Stepanov.
The hypsographic curve of the Earth's relief has two flat sections: one of them at sea level, the other at a depth of 4-5 km. These areas correspond to the presence of two rocks of different densities. The flat section at sea level corresponds to light rocks consisting of granite (density 2800 kg/m³), the lower section corresponds to heavy rocks composed of basalts (3300 kg/m³). Unlike the Earth, the hypsographic curve of the Moon does not contain flat sections, which indicates the absence of differentiation of rocks.
CLARKEY elements, numbers expressing the average chemical content. elements in the earth's crust, hydrosphere, the Earth as a whole, cosmic. bodies, etc.
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geochem. or cosmochemical systems. There are weights (in%, in G/T or in g/ G) and atomic (% of the number of atoms) clarkes. Generalization of data on chemistry. composition of various rocks that make up the earth's crust, taking into account their distribution to depths of 16 km m was first made by Amer.
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scientist F.W. Clark(1889). The figures he obtained for the percentage of chemicals. The elements in the composition of the earth's crust, subsequently somewhat refined by A.E. Fersman, at the latter's suggestion, were called Clarke numbers, or clarke numbers. Average contents of elements in the earth's crust, in modern times.
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understanding it as the upper layer of the planet above the Mohorovicic boundary (see. Mohorovicic surface), calculated by A.P. Vinogradov(1962), Amer.
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scientist S. R. Taylor (1964), German. - K. G. Vedepol (1967) (see table). Elements of small serial numbers predominate: 15 of the most common elements, the clarks of which are above 100 g/ T, have serial numbers up to 26 (Fe). Elements with even serial numbers make up 87% of the mass of the earth's crust, and those with odd numbers make up only 13%. Average chem. The composition of the Earth as a whole was calculated based on data on the content of elements in meteorites (see. Geochemistry).
Since K. elements serve as a standard for comparing reduced or increased concentrations of chemicals. elements in mineral deposits, rocks or entire regions, knowledge of them is important when searching and industrial. assessment of mineral deposits; they also make it possible to judge the violation of the usual relationships between similar elements (chlorobromine, niobium - tantalum) and thereby indicate different physical-chemical properties. factors that disrupt these equilibrium relationships.
In processes element migration K. Elements are quantities, an indicator of their concentration.
The earth's crust contains many elements, but its main part is oxygen and silicon.
The average values of chemical elements in the earth's crust are called clarks. The name was introduced by the Soviet geochemist A.E. Fersman in honor of the American geochemist Frank Wiglesworth Clark, who, after analyzing the results of thousands of rock samples, calculated the average composition of the earth's crust. Clark's calculated composition of the earth's crust was close to granite, a common igneous rock in the Earth's continental crust.
After Clark, the Norwegian geochemist Victor Goldschmidt began determining the average composition of the earth's crust. Goldschmidt made the assumption that the glacier, moving along the continental crust, scrapes off and mixes the rocks that come to the surface. For this reason, glacial deposits or moraines reflect the average composition of the earth's crust. By analyzing the composition of the ribbon clays deposited on the bottom of the Baltic Sea during the last glaciation, the scientist obtained the composition of the earth's crust, which was very similar to the composition of the earth's crust calculated by Clark.
Subsequently, the composition of the earth's crust was studied by Soviet geochemists Alexander Vinogradov, Alexander Ronov, Alexei Yaroshevsky, and the German scientist G. Wedepohl.
After analyzing all scientific works, it was found that the most common element in the earth's crust is oxygen. His clarke is 47%. The next most abundant chemical element after oxygen is silicon with a clarke of 29.5%. Other common elements are: aluminum (clarke 8.05), iron (4.65), calcium (2.96), sodium (2.5), potassium (2.5), magnesium (1.87) and titanium (0.45). Taken together, these elements make up 99.48% of the entire composition of the earth’s crust; they form numerous chemical compounds. The Clarks of the remaining 80 elements are only 0.01-0.0001 and therefore such elements are called rare. If an element is not only rare, but also has a weak ability to concentrate, it is called rare scattered.
In geochemistry, the term “microelements” is also used, which means elements whose clarke in a given system is less than 0.01. A.E. Fersman plotted the dependence of atomic clarkes for even and odd elements of the periodic table. It was revealed that as the structure of the atomic nucleus becomes more complex, the clarke values decrease. But the lines constructed by Fersman turned out to be not monotonous, but broken. Fersman drew a hypothetical middle line: he called the elements located above this line excess (O, Si, Ca, Fe, Ba, Pb, etc.), below - deficient (Ar, He, Ne, Sc, Co, Re etc.).
You can get acquainted with the distribution of the most important chemical elements in the earth's crust using this table:
Age of the Earth- time has passed since the formation of the Earth as an independent planet. According to modern scientific data, the age of the Earth is 4.54 billion years (4.54·10 9 years ± 1%). These data are based on radioisotope dating of not only terrestrial samples, but also meteorite matter. Οʜᴎ were obtained primarily using the lead-lead method. This figure corresponds to the age of the oldest Earth and lunar samples.
After the scientific revolution and the development of radioisotope dating methods, it turned out that many mineral samples are over a billion years old. The oldest found so far are small zircon crystals from the Jack Hills in Western Australia - their age is at least 4404 million years. Based on a comparison of the mass and luminosity of the Sun and other stars, it was concluded that the Solar System should not be much older than these crystals. The calcium- and aluminum-rich nodules found in meteorites are the oldest known samples to have formed within the Solar System, at 4,567 million years old, providing an estimate of the age of the Solar System and an upper limit on the age of the Earth. There is a hypothesis that the accretion of the Earth began shortly after the formation of calcium-aluminum nodules and meteorites. Because the exact time of Earth's accretion is unknown and various models give anywhere from a few million to 100 million years, the exact age of the Earth is difficult to determine. At the same time, it is difficult to determine the absolutely exact age of the oldest rocks exposed on the surface of the Earth, since they are composed of minerals of different ages.
Time in geology
Determining the age of rocks is based on studying the sequence of formation of strata in the earth's crust. Based on data on organic remains, composition, structure and location of layers relative to each other in the vertical and horizontal directions, a geochronological scale has been developed that reflects the geological history of the Earth. In accordance with the geochronological scale, a stratigraphic scale has been created, which indicates rock complexes formed during geological periods of time. Below is the relationship between the basic geochronological and stratigraphic units, ᴛ.ᴇ. intervals of geological time and rock complexes formed in the corresponding time interval. Geological time interval: Era-Period-Era-Century The complex of rocks formed during this interval: Group-System-Department-Tier Thus, during an era a complex of rocks called a group was formed, during a period a complex of rocks called a system was formed, etc. On the geochronological scale (Table 2.1.1.3.1), there are five largest intervals of geological time - eras, each of which is divided into periods, and each period into epochs. Geochronological scales are also compiled with more fractional chronological intervals: epochs are divided into centuries. Divisions of a stratigraphic scale usually have the same names. For example, the Cenozoic era corresponds to the Cenozoic group of rocks, and during the Neogene period complexes of rocks of the Neogene system were formed, etc. Moreover, the names of the eras often do not coincide with the names of the departments.
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Determining the relative age of rocks - this is an establishment of which rocks formed earlier and which later. Relative age of sedimentary ᴦ.p. is established using geological-stratigraphic (stratigraphic, lithological, tectonic, geophysical) and biostratigraphic methods. The stratigraphic method is based on the fact that the age of a layer at normal occurrence is determined - the underlying layers are more ancient, and the overlying ones are younger. This method should also be used for folded layers. It should not be used with overturned folds. The lithological method is based on the study and comparison of the composition of rocks in different outcrops (natural - on the slopes of rivers, lakes, seas, artificial - quarries, pits, etc.). In a limited area, sediments of the same material composition (ᴛ.ᴇ. consist of the same minerals and rocks) are of the same age. When comparing sections of various outcrops, marker horizons are used, which are clearly distinguished from other rocks and are stratigraphically consistent over a large area. The tectonic method is based on the fact that powerful deformation processes ᴦ.p. appear (as a rule) simultaneously over large areas; therefore, strata of the same age have approximately the same degree of dislocation (displacement). In the history of the Earth, sedimentation periodically gave way to folding and mountain building. The mountainous regions that emerged were destroyed, and the sea again invaded the leveled territory, at the bottom of which strata of new sedimentary deposits were already accumulating unconformably. in this case, various unconformities serve as boundaries dividing sections into separate strata. Geophysical methods are based on the use of physical characteristics of sediments (resistivity, natural radioactivity, remanent magnetization, etc.) when dividing them into layers and comparing them. Division rocks in boreholes based on resistivity measurements ᴦ.p. and porosity is usually called electrical logging, based on measurements of their radioactivity - gamma logging. Study of remanent magnetization ᴦ.p. called the paleomagnetic method; it is based on the fact that magnetic minerals, when precipitated, spread out in accordance with the magnetic field of the Earth of that era, which, as is known, was constantly changing over geological time. This orientation is permanently preserved if the rock is not subjected to heating above 500C (the so-called Curie point) or intense deformation and recrystallization. Consequently, in different layers the direction of the magnetic field will be different. Paleomagnetism allows thus. compare deposits that are significantly distant from each other (the western coast of Africa and the eastern coast of Latin America). Biostratigraphic or paleontological methods consist of determining the age of ᴦ.p. through the study of fossil organisms (paleontological methods will be discussed in detail in the next lecture). Determination of the relative age of magmas. And metam. G.p. (ever higher character.
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Methods - for determining the age of sedimentary rocks) is complicated by the lack of paleontological remains. The age of effusive rocks occurring together with sedimentary rocks is determined by the ratio to sedimentary rocks. The relative age of intrusive rocks is determined by the ratio of igneous rocks and host sedimentary rocks, the age of which is established. Determining the relative age of metathromic rocks is similar to determining the relative age of igneous rocks.
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Material from Wikipedia - the free encyclopedia
| Geochronological scale | |||
| Eon | Era | Period | |
| P h a n e r o s e | Cenozoic | Quaternary | |
| Neogene | |||
| Paleogene | |||
| Mesozoic | Chalk | ||
| Yura | |||
| Triassic | |||
| Paleozoic | Permian | ||
| Carbon | |||
| Devonian | |||
| Silur | |||
| Ordovician | |||
| Cambrian | |||
| DOCEMBRIA | Proterozoic | Neo-Proterozoic | Ediacaran |
| Cryogenium | |||
| Tony | |||
| Meso-Proterozoic | Stenius | ||
| Ectasy | |||
| Kalimium | |||
| Paleo-Proterozoic | Staterius | ||
| Orosirium | |||
| Riasiy | |||
| Siderius | |||
| A r h e y | Neoarchaean | ||
| Mesoarchean | |||
| Paleoarchaean | |||
| Eoarchaean | |||
| Katarhey | |||
| Source |
Geochronological scale- a geological time scale of the history of the Earth, used in geology and paleontology, a kind of calendar for periods of time of hundreds of thousands and millions of years.
According to modern generally accepted ideas, the age of the Earth is estimated at 4.5-4.6 billion years. No rocks or minerals have been found on the Earth's surface that could have witnessed the formation of the planet. The maximum age of the Earth is limited by the age of the earliest solid formations in the Solar System - refractory inclusions rich in calcium and aluminum (CAI) from carbonaceous chondrites. The age of CAI from the Allende meteorite, according to the results of modern studies by the U-Pb isotope method, is 4568.5 ± 0.5 million years. This is currently the best estimate of the age of the Solar System. The time of formation of the Earth as a planet must be millions and even many tens of millions of years later than this date.
Subsequent time in the history of the Earth was divided into various time intervals according to the most important events that then occurred.
The boundary between the eras of the Phanerozoic passes through the largest evolutionary events - global extinctions. The Paleozoic is separated from the Mesozoic by the largest extinction event in Earth history, the Permo-Triassic extinction event. The Mesozoic is separated from the Cenozoic by the Cretaceous-Paleogene extinction event.
Geochronological scale depicted as a spiral
[edit] History of the creation of the scale
In the second half of the 19th century, at the II-VIII sessions of the International Geological Congress (IGC) in 1881-1900. the hierarchy and nomenclature of most modern geochronological divisions were adopted. Subsequently, the International Geochronological (Stratigraphic) Scale was constantly refined.
Specific names were given to periods based on various characteristics. Most often, geographical names were used. Thus, the name of the Cambrian period comes from the Latin. Cambria- the names of Wales when it was part of the Roman Empire, Devonian - the county of Devonshire in England, Permian - from ᴦ. Perm, Jurassic - from the Jura Mountains in Europe. The Vendian (Vendians is the German name for the Slavic people of the Lusatian Sorbs), Ordovician and Silurian (Celtic tribes Ordovicians and Silurians) periods are named after the ancient tribes. Names related to the composition of the rocks were used less frequently. The Carboniferous period is named because of the large number of coal seams, and the Cretaceous period is named because of the widespread occurrence of writing chalk.
[edit] The principle of constructing a scale
The geochronological scale was created to determine the relative geological age of rocks. Absolute age, measured in years, is of secondary importance to geologists.
The existence of the Earth is divided into two main intervals (eons): Phanerozoic and Precambrian (Cryptozoic) according to the appearance of fossil remains in sedimentary rocks. Cryptozoic is a time of hidden life; only soft-bodied organisms existed in it, leaving no traces in sedimentary rocks. The Phanerozoic began with the appearance on the border of the Ediacaran (Vendian) and Cambrian of many species of mollusks and other organisms, allowing paleontology to dissect the strata based on finds of fossil flora and fauna.
Another major division of the geochronological scale has its origin in the very first attempts to divide the history of the earth into major time intervals. Then the whole history was divided into four periods: primary, which is equivalent to the Precambrian, secondary - Paleozoic and Mesozoic, tertiary - the entire Cenozoic without the last Quaternary period. The Quaternary period occupies a special position. This is the shortest period, but many events took place in it, the traces of which are better preserved than others.
| Aeon (eonoteme) | Era (erathema) | Period (system) | Epoch (department) | Start, years ago | Main events |
| Phanerozoic | Cenozoic | Quaternary (anthropogenic) | Holocene | 11.7 thousand | The end of the Ice Age. The emergence of civilizations |
| Pleistocene | 2.588 million | Extinction of many large mammals. The emergence of modern man | |||
| Neogene | Pliocene | 5.33 million | |||
| Miocene | 23.0 million | ||||
| Paleogene | Oligocene | 33.9 ± 0.1 million | The appearance of the first apes. | ||
| Eocene | 55.8 ± 0.2 million | The appearance of the first “modern” mammals. | |||
| Paleocene | 65.5 ± 0.3 million | ||||
| Mesozoic | Chalky | 145.5 ± 0.4 million | The first placental mammals. The extinction of dinosaurs. | ||
| Jurassic | 199.6 ± 0.6 million | The appearance of marsupial mammals and the first birds. The Rise of the Dinosaurs. | |||
| Triassic | 251.0 ± 0.4 million | The first dinosaurs and egg-laying mammals. | |||
| Paleozoic | Permian | 299.0 ± 0.8 million | About 95% of all existing species became extinct (Permian Mass Extinction). | ||
| Coal | 359.2 ± 2.8 million | The appearance of trees and reptiles. | |||
| Devonian | 416.0 ± 2.5 million | The appearance of amphibians and spore-bearing plants. | |||
| Silurian | 443.7 ± 1.5 million | Exit of life to land: scorpions; appearance of gnathostomes | |||
| Ordovician | 488.3 ± 1.7 million | Racoscorpions, the first vascular plants. | |||
| Cambrian | 542.0 ± 1.0 million | The emergence of a large number of new groups of organisms (the Cambrian Explosion). | |||
| Precambrian | Proterozoic | Neoproterozoic | Ediacaran | ~635 million | The first multicellular animals. |
| Cryogenium | 850 million | One of the largest glaciations on Earth | |||
| Tony | 1.0 billion | The beginning of the collapse of the supercontinent Rodinia | |||
| Mesoproterozoic | Stenius | 1.2 billion | Supercontinent Rodinia, superocean Mirovia | ||
| Ectasy | 1.4 billion | The first multicellular plants (red algae) | |||
| Kalimium | 1.6 billion | ||||
| Paleoproterozoic | Staterius | 1.8 billion | |||
| Orosirium | 2.05 billion | ||||
| Riasiy | 2.3 billion | ||||
| Siderius | 2.5 billion | Oxygen disaster | |||
| Archaea | Neoarchaean | 2.8 billion | |||
| Mesoarchean | 3.2 billion | ||||
| Paleoarchaean | 3.6 billion | ||||
| Eoarchaean | 4 billion | The emergence of primitive single-celled organisms | |||
| Katarhey | ~4.6 billion | ~4.6 billion years ago - formation of the Earth. |
[edit]Scale diagrams of the geochronological scale
Three chronograms are presented, reflecting different stages of the history of the earth on different scales.
1. The top diagram covers the entire history of the earth;
2. The second is the Phanerozoic, a time of mass emergence of various forms of life;
3. Bottom - Cenozoic, the period of time after the extinction of the dinosaurs.
Millions of years
Geochronological scale - concept and types. Classification and features of the category "Geochronological scale" 2017, 2018.
Q
The geochronological scale is represented by the sequence of the history of the Earth, dividing it into a system of time intervals. It reflects the relative age of layers of sedimentary rocks, determined on the basis of their relative positions and the presence of organic remains.
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 eras. The latter were united into eras. That is, the original scale included three divisions. Later, a fourth, larger category was introduced - aeon. In 2004, the International Union of Geological Sciences approved the model 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, they added an even larger division - Acrons.
Basic principles
The geochronological scale is based on the division of sedimentary rocks or associated igneous massifs by relative age.
Its definition relates 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 connects 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 drawing up geological maps.
In addition, the geochronological scale is of great practical importance. Thus, it is used in regional geological studies aimed at elucidating the tectonic features of the territory, determining the direction of searches and exploration of minerals, especially those confined to strata deposits corresponding to specific stratigraphic levels. Geological maps created on the basis of the geochronological scale are used when carrying out geotechnical work, environmental studies, etc.
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And finally, scientists had to solve one more problem: how did modern continents take their current places? The theory of continental drift answered this question. At first it was expressed as a bold assumption, then it became a hypothesis, and today, on its basis, the theory of lithospheric plate tectonics has been developed - the fundamental concept of modern geology. Thanks to it, we know about the movement of continents, how continental plates move and collide with each other, oceans appear 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 the same process - tectonics. This theory helped test many previously existing ideas about the emergence and subsequent changes of the atmosphere, oceans, the Earth itself and life on it.
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 create a geological time scale - a geochronological scale.
Each era is divided into periods, a period into epochs, and epochs into centuries.
Archean era - the era of the beginning of life
Proterozoic era - the era of primary life
Riphean - era of early life
Paleozoic era of ancient life
Mesozoic - era of middle life
Cenozoic - the era of modern life.
The eras are united into two eons: Cryptose and Phanerozoic.
The Croptozoic era 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 single-celled organisms. 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 strata of sedimentary rocks. First, the platforms of the northern hemisphere and the Australian were formed, later the Indian, South American, African and Antarctic. At the same time, the first geosynclines (folded mountains) took shape.
Geological formations of these eras are represented by igneous, ancient sedimentary and metamorphic rocks: crystalline schists, limestones, marbles, etc. In an unweathered state, these rocks are a good foundation and good building materials. They form the crystalline foundation of the Russian, West Siberian and other plains, and come to the surface in our country south of Voronezh, in Karelia, the Murmansk region, in Eastern Siberia, the Urals, Central Asia and Altai.
Other eras - Pleozoic, Mesozoic and Cenozoic - are combined into the Phanerozoic (approximately 570 million years). The Phaenerozoic is the most important stage in the geological history of the Earth, which is characterized by the emergence and widespread development of skeletal organisms, the flourishing of the organic world and the appearance of man.
Palaeozoic–Pz began approximately 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. When necessary, changes were introduced to the standard stratigraphic scale to reflect regional specifics. For example, in Europe there is a Carboniferous period, and in the USA there are two corresponding periods - the Mississippian and the Pennsylvanian.
The Paleozoic era is characterized 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 of rocks. The first, Caledonian phase occurred in Scotland, Western Scandinavia, Greenland, and in Russia it is the Transbaikalia region. During the second, Hercynian phase, the Ural Mountains, Tien Shan, Altai, etc. were formed. During the era of rock formation, the tropical climate gave way to a sharp cooling, and during the era of the Hercynian phase, glaciation even occurred.
During the Paleozoic era, limestones, marls, and dolomites were formed in the seas, and clays, sands and sandstones were formed on the continents. In the last periods of the Paleozoic - Carboniferous and Permian - thick deposits of coal, limestone, sandstone, shale, 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 were very far from modern ones; these were spore plants and invertebrate animals, and subsequently extinct vertebrates.
Most 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 peace. 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 climate was observed, in which coals and clays were formed.
During the Mesozoic period, marine and continental sediments became equally widespread. Within the Russian plain, thick deposits of chalk, limestone, and clay formed. The possibilities of using rocks of the Mesozoic era for construction purposes are the same as during the Paleozoic period.
During this era, reptiles were very large in size. The fauna and flora were of a transitional nature - from ancient forms of the organic world to modern ones.
Cenozoic eraKz(the era of new life) began 65 million years ago. The flora and fauna are approaching modern forms, and man appears. The era is divided into three periods: Paleogene, Neogene and Quaternary. The first two periods are usually combined into one - tertiary. The Quaternary period takes only 1 million years and has been studied in 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 was observed, which in the Quaternary period turned into the Ice Age with periodic glaciations. Glaciations covered a vast territory of northern Europe and Asia.
In the Cenozoic era, the so-called Alpine folding manifested itself very intensively, the formation of which began in the Jurassic period. 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 Mountains, the Tien Shan, the Himalayas, the Kuril Islands, and Sakhalin-Kamchatka appeared. The Alpine orogeny phase has not yet ended.
In the Tertiary period, rocks of marine and continental origin were formed. Marine tertiary deposits - clays, limestones, shell rocks, etc. are located on the Black Sea coast and in other places. Continental tertiary deposits are ubiquitous.
The overwhelming majority of Quaternary rocks are continental deposits - loose rocks and rocks of organogenic origin. They are usually called Quaternary rocks or sediments in contrast to the earlier rocks, which I call bedrock. Marine Quaternary deposits are rare in Russia - on the coasts of the seas, 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 tertiary ones. A special group among them are marine silts.
The thickness of Quaternary deposits ranges from several centimeters to tens and hundreds of meters. These rocks are less reliable as foundations than roots. Their properties vary widely and largely depend on genetic characteristics.
Bedrock is usually represented by rock and compacted sand and clay rocks, and among Quaternary sediments, loose formations, weakly cemented and cohesive, predominate.
