Large geological cycle of substances. Small biological (geographic) cycle of substances

The large geological circulation of substances is caused by the interaction of solar energy with the deep energies of the Earth and carries out the redistribution of substances between the biosphere and the deeper horizons of the Earth. Sedimentary rocks are immersed in a zone of high temperatures and pressures in mobile zones of the earth's crust. There they melt and form magma - the source of new igneous rocks. After these rocks rise to the earth's surface and undergo weathering processes, they are again transformed into new sedimentary rocks.

The Great Cycle also includes the circulation of water between land and ocean through the atmosphere. Moisture that has evaporated from the surface of the world's oceans is transferred to land, where it falls in the form of precipitation, which is returned to the ocean in the form of surface runoff and underground runoff. The water cycle also occurs according to a simpler scheme: evaporation of moisture from the ocean surface - condensation of water vapor - precipitation on the ocean surface. More than 500 thousand cubic meters participate in the water cycle every day. km. water. The entire supply of water on Earth decays and is restored in 2 million years.

The small cycle of substances (biogeochemical) occurs only within the biosphere. Its essence lies in the formation of living matter from inorganic compounds during the process of photosynthesis and in the transformation of organic matter during decomposition back into inorganic compounds. This cycle for the life of the biosphere is the main one and is a continuation of life itself. By changing, being born and dying, living matter supports life on our planet, ensuring the biogeochemical cycle of substances. The main source of energy in the cycle is sunlight, which provides photosynthesis.

The essence of the biogeochemical cycle is that chemical elements absorbed by an organism subsequently leave it and go into the abiotic environment, after some time they again enter the living organism. In biogeochemical cycles, it is customary to distinguish between a reserve fund, or substances not associated with organisms; exchange fund due to the direct exchange of nutrients between organisms and their immediate environment. If we consider the biosphere as a whole, we can distinguish the cycle of gaseous substances with a reserve fund in the atmosphere and hydrosphere and the sedimentary cycle with a reserve fund in the earth's crust in the geological cycle.

As a whole, cycles ensure the fulfillment of the following most important functions of living matter in the biosphere:

• o Gas: a product of the decomposition of dead organic matter.
• o Concentration: organisms accumulate many chemical elements.
• o Redox: organisms living in water bodies regulate the acid regime.
• o Biochemical: reproduction, growth and movement of living matter in space
• o Biogeochemical human activity: the involvement of natural substances for economic and domestic needs of humans.

The only process on Earth that does not consume, but accumulates solar energy is the creation of organic matter as a result of photosynthesis. The binding and storage of solar energy is the main planetary function of living matter on Earth. The most important nutrients are carbon, nitrogen, oxygen, phosphorus, and sulfur.

Trophic network

Usually, for each link in the chain, you can specify not one, but several other links connected to it by the “food-consumer” relationship. So, not only cows, but also other animals eat grass, and cows are food not only for humans. The establishment of such connections turns the food chain into a more complex structure - food web.

Trophic level

Trophic level is a conventional unit indicating the distance from producers in the trophic chain of a given ecosystem. In some cases, in a trophic network, it is possible to group individual links into levels in such a way that links at one level act only as food for the next level. This grouping is called a trophic level.

Cycle of substances and energy flows in ecosystems

Nutrition is the main way of movement of substances and energy. Organisms in an ecosystem are connected by a commonality of energy and nutrients that are necessary to sustain life. The main source of energy for the vast majority of living organisms on Earth is the Sun. Photosynthetic organisms (green plants, cyanobacteria, some bacteria) directly use the energy of sunlight. In this case, complex organic substances are formed from carbon dioxide and water, in which part of the solar energy is accumulated in the form of chemical energy. Organic substances serve as a source of energy not only for the plant itself, but also for other organisms in the ecosystem. The release of energy contained in food occurs during the process of breathing. Respiration products - carbon dioxide, water and inorganic substances - can be reused by green plants. As a result, substances in this ecosystem undergo an endless cycle. At the same time, the energy contained in food does not cycle, but gradually turns into thermal energy and leaves the ecosystem. Therefore, a necessary condition for the existence of an ecosystem is a constant flow of energy from outside. Thus, the basis of the ecosystem is made up of autotrophic organisms - producers (producers, creators), which, through the process of photosynthesis, create energy-rich food - primary organic matter. In terrestrial ecosystems, the most important role belongs to higher plants, which, forming organic substances, give rise to all trophic relationships in the ecosystem, serve as a substrate for many animals, fungi and microorganisms, and actively influence the microclimate of the biotope. In aquatic ecosystems, the main producers of primary organic matter are algae. Ready-made organic substances are used to obtain and accumulate energy by heterotrophs, or consumers. Heterotrophs include herbivores (consumers of the 1st order), carnivores that live off herbivorous forms (consumers of the 2nd order), consuming other carnivores (consumers of the 3rd order), etc. A special group of consumers consists of decomposers (destroyers, or destructors), decomposing organic remains of producers and consumers to simple inorganic compounds, which are then used by producers. Decomposers include mainly microorganisms - bacteria and fungi. In terrestrial ecosystems, soil decomposers are especially important, drawing organic matter from dead plants into the general cycle (they consume up to 90% of the primary forest production). Thus, each living organism within an ecosystem occupies a certain ecological niche (place) in a complex system of ecological relationships with other organisms and abiotic environmental conditions.

Biological and geological cycles.

The processes of photosynthesis of organic matter from inorganic components continues for millions of years, and during this time the chemical elements must have passed from one form to another. However, this does not happen due to their circulation in the biosphere. Every year, photosynthetic organisms assimilate about 350 billion tons of carbon dioxide, release about 250 billion tons of oxygen into the atmosphere and break down 140 billion tons of water, forming more than 230 billion tons of organic matter (calculated by dry weight). Enormous quantities of water pass through plants and algae during transport and evaporation. This leads to the fact that the water of the surface layer of the ocean is filtered by plankton in 40 days, and the rest of the ocean water is filtered in about a year. All carbon dioxide in the atmosphere is renewed in several hundred years, and oxygen in several thousand years. Every year, photosynthesis includes 6 billion tons of nitrogen, 210 billion tons of phosphorus and a large number of other elements (potassium, sodium, calcium, magnesium, sulfur, iron, etc.) into the cycle. The existence of these cycles gives the ecosystem a certain stability.

There are two main cycles: large (geological) and small (biotic). The great cycle, which continues for millions of years, consists in the fact that rocks are destroyed, and weathering products (including water-soluble nutrients) are carried by water flows into the World Ocean, where they form marine strata and only partially return to land with precipitation . Geotectonic changes, the processes of continental subsidence and seabed rise, the movement of seas and oceans over a long period of time lead to the fact that these strata return to land and the process begins again. The small cycle (part of the large one) occurs at the ecosystem level and consists in the fact that nutrients, water and carbon accumulate in the substance of plants, are spent on building the body and on the life processes of both these plants themselves and other organisms (usually animals), that eat these plants (consumers). The decay products of organic matter under the influence of decomposers and microorganisms (bacteria, fungi, worms) again decompose into mineral components that are accessible to plants and are drawn into the flow of matter by them. The circulation of chemicals from the inorganic environment through plant and animal organisms back into the inorganic environment using solar energy and the energy of chemical reactions is called the biogeochemical cycle. Almost all chemical elements are involved in such cycles, and primarily those that are involved in the construction of a living cell. Thus, the human body consists of oxygen (62.8%), carbon (19.37%), hydrogen (9.31%), nitrogen (5.14%), calcium (1.38%), phosphorus (0. 64%) and about 30 more elements.

The role of Man.

A person has the power to change the strength of action and the number of limiting factors, as well as expand or, conversely, narrow the boundaries of the optimal values ​​of environmental factors. For example, harvesting is inevitably associated with the depletion of soil elements of mineral nutrition of plants and the transfer of some of them to the category of limiting factors. Various types of land reclamation (watering, drainage, fertilization, etc.) optimize factors and remove their limiting effect. Man has immeasurably expanded his adaptive capabilities by conditioning the conditions of his environment (clothing, housing, new materials, etc.) and thereby sharply reduced his dependence on the natural environment and the resources it represents. For example, in the human diet, wild food resources make up only 10-15%. The remaining food needs are met through cultural farming. The consequence of reducing dependence on environmental factors is the expansion of man’s range to the entire planet and the removal of natural mechanisms for regulating population numbers.

Man has changed this principle of food chains and ecological pyramids in relation to both his own population and other species (varieties, breeds), especially those grown in cultural farming. This discrepancy with natural ecosystems is made possible by the appropriation and investment of additional energy into systems. Violating the rules of ecological pyramids turns out to be unreasonably expensive. It is inevitably accompanied by changes in the cycles of substances, the accumulation of waste and environmental pollution. An example is livestock farms with their environmental problems. Violation of the rules of the pyramids is also due to the fact that human consumer interests have gone beyond the limits of biological resources as a whole. Its interests include products (resources) of previous geological eras, and many of the products produced become dead ends (waste and pollutants). The people of Earth alone, as a biological species, require about 2 million tons of food and 10 billion m3 of oxygen every day. In addition, almost 30 million tons of substances are extracted and processed, about 30 million tons of fuel are burned, 2 billion m3 of water and 65 billion m3 of oxygen are used for technical needs

Due to their omnivorous nature, people begin to eat more and more diverse organisms, which requires a variety of methods of catching prey or searching for plants. Of course, you also have to come up with ways to make the prey edible. It's one thing to fry a rabbit and quite another to cook a jellyfish for dinner. Only a sophisticated mind could think of eating, for example, cassava, the tubers of which are bitter and also contain hydrocyanic acid. However, throughout Brazil, and not only there, cassava is grown and eaten in quantities comparable to potatoes eaten in Russia. But coming up with a technology for processing it was a very difficult task.

By eating a wide variety of organisms, a person becomes involved in many food chains, removing additional organic matter and ending these chains with himself. He turns out to be an apex predator everywhere. So man began to shorten food chains in many ecosystems, and the shorter such a chain, the faster the turnover of matter and energy.

Also, human activity is associated with a strong transformation of natural habitats. Modern man prefers not to change in accordance with environmental conditions, but to change these conditions themselves. Therefore, he devotes considerable intellectual and technical effort to transforming the environment. Having plowed the meadow space and sowed it with the necessary plants, the plowman has already radically changed the environment. Of the many plants in the meadow, he left only one, and even then, most often, it was alien. He transformed the soil and its fauna, formed here over many hundreds of years, in a few hours. As a result, the resource of almost all animal species was eliminated, and their food plants disappeared. The converted space became unsuitable for many native plants and unattainable for others. The owner of the crop protects his field, waters it with herbicides, and fights with competing consumers.

As we remember, in ecosystems a person lives not alone, but with a huge number of neighbors - plant and animal organisms. This transformed environment is not suitable for all of them. Many, especially primitive forms of life, easily adapt to changing conditions. For the vast majority of complex organisms, the new environment is not suitable. They leave these places or die. So any transformation of nature always leads to the death of many organisms.

Eating. The range of food for this zoological species is probably the widest on the planet. Man is an amazing euryphage (polyphagous) and eats almost everything. The list of animals on his menu is huge, which, along with the traditional cows, sheep and poultry, includes termites, locusts, locusts and centipedes, and some spiders. The larvae of various insects - bees, tree beetles - are eaten by many peoples as a delicacy. Residents of Africa eagerly eat the huge larvae of the goliath beetle, where it is found. A variety of lizards, snakes, turtles and frogs are also firmly established in human diets. The inhabitants of the water - fish and shellfish - have been traditional food since the time of the Cro-Magnon man. However, here too the diet of the species expanded, including a huge number of animals from whales to some jellyfish and euphausids.

Ecologists, studying the diets of animals, especially those that are food competitors for humans, note that many of them have a striking diversity of food. For example, a typical polyphagous water vole, which destroys the crops of peasants in the southern part of Western Siberia, is capable of eating more than 300 species of plants. As this animal is studied, ever longer lists of food suitable for it are compiled. Man, in the role of a herbivorous animal (the primary consumer), has far surpassed all other species. No one has yet compiled a complete list of its food plants on the planet, but their length is easy to guess. Thus, in Japanese cuisine, flower buds of about 300 plant species are used to prepare various dishes. Chinese cuisine is even more sophisticated and varied. And if we add here lists of food plant species from the cookbooks of the inhabitants of the tropical zone!?

People use both animals and plants for food purposes with increasing intensity. If he does not eat some animals directly, he feeds them to his food animals or fertilizes the fields with them. Man is wasteful and often uses even delicious species, along with food, as feed and even as fertilizer. For example, the history of fishing for sea striped bass - fish almost 2 meters in length and 50 - 70 kg in weight. It is superior in taste to Atlantic salmon. This perch was caught in huge quantities at the beginning of the 17th century off the coast of New England. Most of these catches were used to fertilize the land plots of local residents. Colonial farmers buried hundreds of tons of this fish in their corn fields. In the Newfoundland area, many tons of Atlantic salmon were used to fertilize fields in the early 19th century. The same thing happened with overfishing of cod and sturgeon. Huge factories were built to process mackerel, herring, capelin and other marine fish into fertilizers and animal feed. In Newfoundland at the beginning of the 18th century, the meat of huge lobster sea crayfish (they weighed up to 10 - 12 kg) was used for bait when fishing for cod, as well as for fattening domestic animals. Each potato field was strewn with the shells of these crustaceans, because 2-3 lobsters were placed under each potato bush for fertilizer. Until the mid-20th century, these giant and very tasty crayfish were fed to livestock in some areas of Newfoundland. Even such an enlightened country as Russia acted wastefully until the very end of the 20th century. In 1998, on television, its not very well-fed population was shown how hundreds of tons of delicious salmon fish were buried in the ground by bulldozers in the Russian Far East. People were unable to dispose of their catches!

Man ensured his transformation into a hypereurybiont not through biological mechanisms, but through technical means, and therefore he has largely lost the potential for biological adaptation. This is the reason that a person is among the first candidates for leaving the arena of life as a result of environmental changes caused by him. Hence an important conclusion: if the modern niche of man is primarily the result of intelligent activity, power over the environment, therefore, the mind must be the main driving force behind its change.

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All substances on our planet are in the process of circulation. Solar energy causes two cycles of substances on Earth:

1) Large (geological or abiotic);

2) Small (biotic, biogenic or biological).

Cycles of matter and flows of cosmic energy create the stability of the biosphere. The cycle of solid matter and water that occurs as a result of the action of abiotic factors (inanimate nature) is called great geological cycle. During a large geological cycle (lasting millions of years), rocks are destroyed, weathered, substances dissolve and enter the World Ocean; geotectonic changes, continental subsidence, and seabed uplift occur. The water cycle time in glaciers is 8,000 years, in rivers - 11 days. It is the great cycle that supplies living organisms with nutrients and largely determines the conditions of their existence.

Great geological cycle in the biosphere is characterized by two important points:

a) is carried out throughout the entire geological development of the Earth;

b) is a modern planetary process that takes a leading part in the further development of the biosphere.

At the present stage of human development, as a result of the large cycle, pollutants such as sulfur and nitrogen oxides, dust, and radioactive impurities are also transported over long distances. The areas of temperate latitudes of the Northern Hemisphere were the most contaminated.

Small, biogenic or biological cycle of substances occurs in solid, liquid and gaseous phases with the participation of living organisms. The biological cycle, as opposed to the geological cycle, requires less energy. The small cycle is part of a large one and occurs at the level of biogeocenoses (within ecosystems) and lies in the fact that soil nutrients, water, and carbon accumulate in plant matter and are spent on building the body. Decay products of organic matter decompose into mineral components. The small gyre is not closed, which is associated with the flow of substances and energy into the ecosystem from the outside and with the release of some of them into the biosphere cycle.

Many chemical elements and their compounds are involved in the large and small cycles, but the most important of them are those that determine the current stage of development of the biosphere, associated with human economic activity. These include gyres carbon, sulfur and nitrogen(their oxides - major air pollutants), and also phosphorus (phosphates are the main pollutant of continental waters). Almost all pollutants are considered harmful and are classified as xenobiotics.

Currently, the cycles of xenobiotics - toxic elements - are of great importance mercury (a food contaminant) products) and lead (a component of gasoline). In addition, many substances of anthropogenic origin (DDT, pesticides, radionuclides, etc.) that cause harm to biota and human health come from the large cycle to the small one.

The essence of the biological cycle lies in the occurrence of two opposite, but interconnected processes - creation organic matter and its destruction living substance.

Unlike the large gyre, the small gyre has a different duration: seasonal, annual, perennial and secular small gyres are distinguished.

The cycling of chemicals from the inorganic environment through vegetation and animals back into the inorganic environment using solar energy chemical reactions is called biogeochemical cycle .

The present and future of our planet depends on the participation of living organisms in the functioning of the biosphere. In the cycle of substances, living matter, or biomass, performs biogeochemical functions: gas, concentration, redox and biochemical.

The biological cycle occurs with the participation of living organisms and consists in the reproduction of organic matter from inorganic and the decomposition of this organic to inorganic through the food trophic chain. The intensity of production and destruction processes in the biological cycle depends on the amount of heat and moisture. For example, the low rate of decomposition of organic matter in polar regions depends on heat deficiency.

An important indicator of the intensity of the biological cycle is the rate of circulation of chemical elements. The intensity is characterized index , equal to the ratio of the mass of forest litter to litter. The higher the index, the lower the intensity of the circulation.

Index in coniferous forests - 10 - 17; broad-leaved 3 - 4; savanna no more than 0.2; in tropical rainforests no more than 0.1, i.e. Here the biological cycle is most intense.

The flow of elements (nitrogen, phosphorus, sulfur) through microorganisms is an order of magnitude higher than through plants and animals. The biological cycle is not completely reversible; it is closely related to the biogeochemical cycle. Chemical elements circulate in the biosphere along various pathways of the biological cycle:

are absorbed by living matter and charged with energy;

leave living matter, releasing energy into the external environment.

These cycles are of two types: the cycle of gaseous substances; sedimentary cycle (reserve in the earth's crust).

The gyres themselves consist of two parts:

- reserve fund(this is the part of the substance that is not associated with living organisms);

- mobile (exchange) fund(a smaller portion of the substance associated with direct exchange between organisms and their immediate environment).

Gyres are divided into:

Gyres gas type with reserve fund in the earth's crust (carbon, oxygen, nitrogen cycles) - capable of rapid self-regulation;

Gyres sedimentary type with reserve fund in the earth's crust (cycles of phosphorus, calcium, iron, etc.) - are more inert, the bulk of the substance is in a form “inaccessible” to living organisms.

Gyres can also be divided into:

- closed(the circulation of gaseous substances, for example, oxygen, carbon and nitrogen, is a reserve in the atmosphere and hydrosphere of the ocean, so the shortage is quickly compensated);

- open(creating a reserve fund in the earth's crust, for example, phosphorus - therefore losses are poorly compensated, i.e. a deficit is created).

The energy basis for the existence of biological cycles on Earth and their initial link is the process of photosynthesis. Each new cycle is not an exact repetition of the previous one. For example, during the evolution of the biosphere, some of the processes were irreversible, resulting in the formation and accumulation of biogenic sediments, an increase in the amount of oxygen in the atmosphere, changes in the quantitative ratios of isotopes of a number of elements, etc.

The circulation of substances is usually called biogeochemical cycles . Basic biogeochemical (biosphere) cycles of substances: water cycle, oxygen cycle, nitrogen cycle(involvement of nitrogen-fixing bacteria), carbon cycle(participation of aerobic bacteria; annually about 130 tons of carbon are released into the geological cycle), phosphorus cycle(involvement of soil bacteria; 14 million tons of phosphorus), sulfur cycle, metal cation cycle.

All substances on our planet are in the process of circulation. Solar energy causes two cycles of substances on Earth, large or biosphere (encompassing the entire biosphere), and small or biological (within ecosystems).

The biosphere circulation of substances was preceded by a geological one, associated with the formation and destruction of rocks and the subsequent movement of destruction products - clastic material and chemical elements. The thermal properties of the surface of land and water played and continue to play a significant role in these processes: absorption into reflection of sunlight, thermal conductivity into heat capacity. Water absorbs more solar energy, and the land surface in the same latitudes heats up more. The unstable hydrothermal regime of the Earth's surface, together with the planetary atmospheric circulation system, determined the geological circulation of substances, which at the initial stage of the Earth's development, along with endogenous processes, was associated with the formation of continents, oceans and modern geospheres. Its geological manifestation is also indicated by the transfer of weathering products by air masses, and by water - mineral compounds dissolved in it. With the formation of the biosphere, the waste products of organisms were included in the large cycle. The geological cycle, without ceasing its existence, acquired new features: it is the initial stage of the biosphere movement of matter. It is he who supplies living organisms with nutrients and largely determines the conditions of their existence.

The large cycle of substances in the biosphere is characterized by two important points:

Carried out throughout the entire geological development of the Earth;

It is a modern planetary process that takes a leading part in the further development of the biosphere (Radkevich, 1983).

At the present stage of human development, as a result of the large cycle, pollutants such as sulfur and nitrogen oxides, dust, and radioactive impurities are also transported over long distances. The territory of temperate latitudes of the Northern Hemisphere was subjected to the greatest contamination.

The small or biological cycle of substances unfolds against the background of a large, geological one, covering the biosphere as a whole. It occurs within ecosystems, but is not closed, which is associated with the entry of matter and energy into the ecosystem from the outside and with the release of some of them into the biosphere cycle. For this reason, people sometimes talk not about the biological cycle, but about the exchange of energy in ecosystems and individual organisms.

Plants, animals and soil cover on land form a complex world system that forms biomass, binds and redistributes solar energy, atmospheric carbon, moisture, oxygen, hydrogen, nitrogen, phosphorus, sulfur, calcium and other elements involved in the life of organisms. Plants, animals and microorganisms of the aquatic environment form another planetary system that performs the same function of linking solar energy and the biological cycle of substances.

The essence of the biological cycle lies in the occurrence of two opposite but interconnected processes - the creation of organic matter and its destruction. The initial stage of the formation of organic matter is due to photosynthesis of green plants, i.e. the formation of this substance from carbon dioxide, water and mineral compounds using the radiant energy of the Sun. Plants extract sulfur, phosphorus, calcium, potassium, magnesium, manganese, silicon, aluminum, copper, zinc and other elements from the soil in dissolved form. Herbivorous animals already absorb compounds of these elements in the form of food of plant origin. Predators feed on herbivorous animals, consume food of a more complex composition, including proteins, fats, amino acids, etc. In the process of destruction by microorganisms of the organic matter of dead plants and animal remains, simple mineral compounds enter the soil and aquatic environment, available for assimilation by plants, and the next round begins biological cycle.

Unlike the large gyre, the small gyre has a different duration: seasonal, annual, perennial and secular small gyres are distinguished. When studying the biological cycle of substances, the main attention is paid to the annual rhythm, determined by the annual dynamics of the development of vegetation.

TO endogenous processes include: magmatism, metamorphism (action of high temperatures and pressure), volcanism, movement of the earth's crust (earthquakes, mountain building).

TO exogenous– weathering, activity of atmospheric and surface waters of seas, oceans, animals, plant organisms and especially humans – technogenesis.

The interaction of internal and external processes forms large geological cycle of substances.

During endogenous processes, mountain systems, hills, and oceanic depressions are formed; during exogenous processes, igneous rocks are destroyed, destruction products move into rivers, seas, oceans, and sedimentary rocks are formed. As a result of the movement of the earth's crust, sedimentary rocks sink into deep layers, undergo metamorphism processes (the action of high temperatures and pressure), and metamorphic rocks are formed. In deeper layers they turn into molten...
state (magmatization). Then, as a result of volcanic processes, they enter the upper layers of the lithosphere, onto its surface in the form of igneous rocks. This is how soil-forming rocks and various landforms are formed.

Rocks, from which soil is formed, are called soil-forming or parent. According to the conditions of formation, they are divided into three groups: igneous, metamorphic and sedimentary.

Igneous rocks consist of compounds of silicon, Al, Fe, Mg, Ca, K, Na. Depending on the ratio of these compounds, acidic and basic rocks are distinguished.

Acidic (granites, liparites, pegmatites) have a high content of silica (more than 63%), potassium and sodium oxides (7-8%), calcium and Mg oxides (2-3%). They are light and brown in color. The soils formed from such rocks have a loose texture, high acidity and low fertility.

Basic igneous rocks (basalts, dunites, periodites) are characterized by a low content of SiO 2 (40-60%), high content of CaO and MgO (up to 20%), iron oxides (10-20%), Na 2 O and less K 2 O less than 30%.

Soils formed on the products of weathering of basic rocks have an alkaline and neutral reaction, a lot of humus and high fertility.

Igneous rocks make up 95% of the total mass of rocks, but as soil-forming rocks they occupy small areas (in the mountains).

Metamorphic rocks, are formed as a result of recrystallization of igneous and sedimentary rocks. These are marble, gneisses, quartz. They occupy a small proportion as soil-forming rocks.

Sedimentary rocks. Their formation is due to the processes of weathering of igneous and metamorphic rocks, the transfer of weathering products by water, glacial and air flows and deposition on the land surface, at the bottom of oceans, seas, lakes, and in floodplains of rivers.

Based on their composition, sedimentary rocks are divided into clastic, chemogenic and biogenic.

Clastic deposits The debris and particles vary in size: these are boulders, stones, gravel, crushed stone, sand, loam and clay.

Chemogenic deposits formed as a result of the precipitation of salts from aqueous solutions in sea bays, lakes in hot climates or as a result of chemical reactions.

These include halides (rock and potassium salt), sulfates (gypsum, anhydride), carbonates (limestone, marl, dolomite), silicates, phosphates. Many of them are raw materials for the production of cement, chemical fertilizers, and are used as agricultural ores.

Biogenic sediments formed from accumulations of plant and animal remains. These are: carbonate (biogenic limestone and chalk), siliceous (dolomite) and carbonaceous rocks (coal, peat, sapropel, oil, gas).

The main genetic types of sedimentary rocks are:

1. Eluvial deposits- products of weathering of rocks remaining on the sheet of their formation. Eluvium is located at the tops of watersheds, where erosion is weakly expressed.

2. Colluvial deposits– erosion products deposited by temporary streams of rain and melt water in the lower part of the slopes.

3. Proluvial deposits– formed as a result of the transfer and deposition of weathering products by temporary mountain rivers and floods at the foot of the slopes.

4. Alluvial deposits– are formed as a result of the deposition of weathering products by river waters entering them with surface runoff.

5. Lake sediments– bottom sediments of lakes. Silts with a high content of organic matter (15-20%) are called sapropels.

6. Marine sediments– bottom sediments of the seas. During the retreat (transgression) of the seas, they remain as soil-forming rocks.

7. Glacial (glacial) or moraine deposits- weathering products of various rocks, transported and deposited by the glacier. This is an unsorted coarse material of red-brown or gray color with inclusions of stones, boulders, and pebbles.

8. Fluvioglacial (fluvio-glacial) deposits temporary watercourses and closed reservoirs formed when the glacier melts.

9. Cover clays belong to extraglacial deposits and are considered as deposits of shallow periglacial meltwater floods. They cover the madder on top with a layer of 3-5 m. They are yellow-brown in color, well sorted, and do not contain stones and boulders. Soils on cover loams are more fertile than on madder.

10. Loess and loess-like loams They are characterized by a fawn color, a high content of dusty and silty fractions, a loose composition, high porosity, and a high content of calcium carbonates. They formed fertile gray forest, chestnut soils, chernozems and gray soils.

11. Aeolian deposits formed as a result of wind activity. The destructive activity of wind consists of corrosion (sharpening, sand grinding of rocks) and deflation (blown away and transport of small soil particles by wind). Both of these processes taken together constitute wind erosion.

Basic diagrams, formulas, etc., illustrating the content: presentation with photographs of weathering types.

Questions for self-control:

1. What is weathering?

2. What is magmatization?

3. What is the difference between physical and chemical weathering?

4. What is the geological cycle of substances?

5. Describe the structure of the Earth?

6. What is magma?

7. What layers does the Earth's core consist of?

8. What are breeds?

9. How are breeds classified?

10. What is loess?

11. What is a faction?

12. What characteristics are called organoleptic?

Main:

1. Dobrovolsky V.V. Geography of soils with the basics of soil science: Textbook for universities. — M.: Humanite. ed. VLADOS Center, 1999.-384 p.

2. Soil Science / Ed. I.S. Kauricheva. M. Agropromiadat ed. 4. 1989.

3. Soil Science / Ed. V.A. Kovdy, B.G. Rozanov in 2 parts M. Higher school 1988.

4. Glazovskaya M.A., Gennadiev A.I. Geography of soils with fundamentals of soil science MSU. 1995

5. Rode A.A., Smirnov V.N. Soil science. M. Higher School, 1972

Additional:

1. Glazovskaya M.A. General soil science and soil geography. M. Higher School 1981

2. Kovda V.A. Fundamentals of the study of soils. M. Nauka.1973

3. Liverovsky A.S. Soils of the USSR. M. Mysl 1974

4. Rozanov B. G. Soil cover of the globe. M. ed. U. 1977

5. Aleksandrova L.N., Naydenova O.A. Laboratory and practical classes in soil science. L. Agropromizdat. 1985