The earth's atmosphere consists of 78 parts. Atmosphere of the earth

The role of the atmosphere in the life of the Earth

The atmosphere is the source of oxygen that people breathe. However, as you rise to altitude, the total atmospheric pressure drops, which leads to a decrease in partial oxygen pressure.

The human lungs contain approximately three liters of alveolar air. If atmospheric pressure is normal, then the partial oxygen pressure in the alveolar air will be 11 mm Hg. Art., carbon dioxide pressure - 40 mm Hg. Art., and water vapor - 47 mm Hg. Art. As altitude increases, oxygen pressure decreases, and the total pressure of water vapor and carbon dioxide in the lungs will remain constant - approximately 87 mm Hg. Art. When the air pressure equals this value, oxygen will stop flowing into the lungs.

Due to the decrease in atmospheric pressure at an altitude of 20 km, water and interstitial fluid in the human body will boil here. If you do not use a pressurized cabin, at such a height a person will die almost instantly. Therefore, from the point of view of the physiological characteristics of the human body, “space” originates from a height of 20 km above sea level.

The role of the atmosphere in the life of the Earth is very great. For example, thanks to the dense air layers - the troposphere and stratosphere, people are protected from radiation exposure. In space, in rarefied air, at an altitude of over 36 km, ionizing radiation acts. At an altitude of over 40 km - ultraviolet.

When rising above the Earth's surface to a height of over 90-100 km, a gradual weakening and then complete disappearance of phenomena familiar to humans observed in the lower atmospheric layer will be observed:

No sound travels.

There is no aerodynamic force or drag.

Heat is not transferred by convection, etc.

The atmospheric layer protects the Earth and all living organisms from cosmic radiation, from meteorites, and is responsible for regulating seasonal temperature fluctuations, balancing and leveling daily cycles. In the absence of an atmosphere on Earth, daily temperatures would fluctuate within +/-200C˚. The atmospheric layer is a life-giving “buffer” between the earth’s surface and space, a carrier of moisture and heat; the processes of photosynthesis and energy exchange take place in the atmosphere - the most important biosphere processes.

Layers of the atmosphere in order from the Earth's surface

The atmosphere is a layered structure consisting of the following layers of the atmosphere in order from the Earth's surface:

Troposphere.

Stratosphere.

Mesosphere.

Thermosphere.

Exosphere

Each layer does not have sharp boundaries between each other, and their height is affected by latitude and seasons. This layered structure was formed as a result of temperature changes at different altitudes. It is thanks to the atmosphere that we see twinkling stars.

Structure of the Earth's atmosphere by layers:

What does the Earth's atmosphere consist of?

Each atmospheric layer differs in temperature, density and composition. The total thickness of the atmosphere is 1.5-2.0 thousand km. What does the Earth's atmosphere consist of? Currently, it is a mixture of gases with various impurities.

Troposphere

The structure of the Earth's atmosphere begins with the troposphere, which is the lower part of the atmosphere with an altitude of approximately 10-15 km. The bulk of atmospheric air is concentrated here. A characteristic feature of the troposphere is a temperature drop of 0.6 ˚C as it rises every 100 meters. The troposphere concentrates almost all atmospheric water vapor, and this is where clouds form.

The height of the troposphere changes daily. In addition, its average value varies depending on the latitude and season of the year. The average height of the troposphere above the poles is 9 km, above the equator - about 17 km. The average annual air temperature above the equator is close to +26 ˚C, and above the North Pole -23 ˚C. The upper line of the tropospheric boundary above the equator is an average annual temperature of about -70 ˚C, and above the North Pole in summer -45 ˚C and in winter -65 ˚C. Thus, the higher the altitude, the lower the temperature. The sun's rays pass unhindered through the troposphere, heating the Earth's surface. The heat emitted by the sun is retained by carbon dioxide, methane and water vapor.

Stratosphere

Above the troposphere layer is the stratosphere, which is 50-55 km in height. The peculiarity of this layer is that the temperature increases with height. Between the troposphere and the stratosphere lies a transition layer called the tropopause.

From approximately an altitude of 25 kilometers, the temperature of the stratospheric layer begins to increase and, upon reaching a maximum altitude of 50 km, acquires values ​​from +10 to +30 ˚C.

There is very little water vapor in the stratosphere. Sometimes at an altitude of about 25 km you can find rather thin clouds, which are called “pearl clouds”. In the daytime they are not noticeable, but at night they glow due to the illumination of the sun, which is below the horizon. The composition of nacreous clouds consists of supercooled water droplets. The stratosphere consists mainly of ozone.

Mesosphere

The height of the mesosphere layer is approximately 80 km. Here, as it rises upward, the temperature decreases and at the very top reaches values ​​of several tens of C˚ below zero. In the mesosphere, clouds can also be observed, which are presumably formed from ice crystals. These clouds are called "noctilucent." The mesosphere is characterized by the coldest temperature in the atmosphere: from -2 to -138 ˚C.

Thermosphere

This atmospheric layer acquired its name due to its high temperatures. The thermosphere consists of:

Ionosphere.

Exosphere.

The ionosphere is characterized by rarefied air, each centimeter of which at an altitude of 300 km consists of 1 billion atoms and molecules, and at an altitude of 600 km - more than 100 million.

The ionosphere is also characterized by high air ionization. These ions are made up of charged oxygen atoms, charged molecules of nitrogen atoms, and free electrons.

Exosphere

The exospheric layer begins at an altitude of 800-1000 km. Gas particles, especially light ones, move here at tremendous speed, overcoming the force of gravity. Such particles, due to their rapid movement, fly out of the atmosphere into outer space and dissipate. Therefore, the exosphere is called the sphere of dispersion. Mostly hydrogen atoms, which make up the highest layers of the exosphere, fly into space. Thanks to particles in the upper atmosphere and particles from the solar wind, we can see the northern lights.

Satellites and geophysical rockets have made it possible to establish the presence in the upper layers of the atmosphere of the planet’s radiation belt, consisting of electrically charged particles - electrons and protons.

At sea level 1013.25 hPa (about 760 mmHg). The global average air temperature at the Earth's surface is 15°C, with temperatures varying from approximately 57°C in subtropical deserts to -89°C in Antarctica. Air density and pressure decrease with height according to a law close to exponential.

The structure of the atmosphere. Vertically, the atmosphere has a layered structure, determined mainly by the features of the vertical temperature distribution (figure), which depends on the geographical location, season, time of day, and so on. The lower layer of the atmosphere - the troposphere - is characterized by a drop in temperature with height (by about 6°C per 1 km), its height from 8-10 km in polar latitudes to 16-18 km in the tropics. Due to the rapid decrease in air density with height, about 80% of the total mass of the atmosphere is located in the troposphere. Above the troposphere is the stratosphere, a layer generally characterized by an increase in temperature with height. The transition layer between the troposphere and stratosphere is called the tropopause. In the lower stratosphere, down to a level of about 20 km, the temperature changes little with height (the so-called isothermal region) and often even decreases slightly. Above that, the temperature increases due to the absorption of UV radiation from the Sun by ozone, slowly at first, and faster from a level of 34-36 km. The upper boundary of the stratosphere - the stratopause - is located at an altitude of 50-55 km, corresponding to the maximum temperature (260-270 K). The layer of the atmosphere located at an altitude of 55-85 km, where the temperature again drops with height, is called the mesosphere; at its upper boundary - the mesopause - the temperature reaches 150-160 K in summer, and 200-230 K in winter. Above the mesopause, the thermosphere begins - a layer characterized by a rapid increase in temperature, reaching 800-1200 K at an altitude of 250 km. In the thermosphere, corpuscular and X-ray radiation from the Sun is absorbed, meteors are slowed down and burned, so it acts as a protective layer of the Earth. Even higher is the exosphere, from where atmospheric gases are dispersed into outer space due to dissipation and where a gradual transition from the atmosphere to interplanetary space occurs.

Atmospheric composition. Up to an altitude of about 100 km, the atmosphere is almost homogeneous in chemical composition and the average molecular weight of the air (about 29) is constant. Near the Earth's surface, the atmosphere consists of nitrogen (about 78.1% by volume) and oxygen (about 20.9%), and also contains small amounts of argon, carbon dioxide (carbon dioxide), neon and other permanent and variable components (see Air ).

In addition, the atmosphere contains small amounts of ozone, nitrogen oxides, ammonia, radon, etc. The relative content of the main components of air is constant over time and uniform in different geographical areas. The content of water vapor and ozone is variable in space and time; Despite their low content, their role in atmospheric processes is very significant.

Above 100-110 km, dissociation of molecules of oxygen, carbon dioxide and water vapor occurs, so the molecular mass of air decreases. At an altitude of about 1000 km, light gases - helium and hydrogen - begin to predominate, and even higher the Earth's atmosphere gradually turns into interplanetary gas.

The most important variable component of the atmosphere is water vapor, which enters the atmosphere through evaporation from the surface of water and moist soil, as well as through transpiration by plants. The relative content of water vapor varies at the earth's surface from 2.6% in the tropics to 0.2% in polar latitudes. It falls quickly with height, decreasing by half already at an altitude of 1.5-2 km. The vertical column of the atmosphere at temperate latitudes contains about 1.7 cm of “precipitated water layer”. When water vapor condenses, clouds form, from which atmospheric precipitation falls in the form of rain, hail, and snow.

An important component of atmospheric air is ozone, concentrated 90% in the stratosphere (between 10 and 50 km), about 10% of it is in the troposphere. Ozone provides absorption of hard UV radiation (with a wavelength of less than 290 nm), and this is its protective role for the biosphere. The values ​​of the total ozone content vary depending on the latitude and season in the range from 0.22 to 0.45 cm (the thickness of the ozone layer at pressure p = 1 atm and temperature T = 0°C). In ozone holes observed in the spring in Antarctica since the early 1980s, ozone content can drop to 0.07 cm. It increases from the equator to the poles and has an annual cycle with a maximum in spring and a minimum in autumn, and the amplitude of the annual cycle is small in the tropics and grows towards high latitudes. A significant variable component of the atmosphere is carbon dioxide, the content of which in the atmosphere has increased by 35% over the past 200 years, which is mainly explained by the anthropogenic factor. Its latitudinal and seasonal variability is observed, associated with plant photosynthesis and solubility in sea water (according to Henry’s law, the solubility of a gas in water decreases with increasing temperature).

An important role in shaping the planet's climate is played by atmospheric aerosol - solid and liquid particles suspended in the air ranging in size from several nm to tens of microns. There are aerosols of natural and anthropogenic origin. Aerosol is formed in the process of gas-phase reactions from the products of plant life and human economic activity, volcanic eruptions, as a result of dust rising by the wind from the surface of the planet, especially from its desert regions, and is also formed from cosmic dust falling into the upper layers of the atmosphere. Most of the aerosol is concentrated in the troposphere; aerosol from volcanic eruptions forms the so-called Junge layer at an altitude of about 20 km. The largest amount of anthropogenic aerosol enters the atmosphere as a result of the operation of vehicles and thermal power plants, chemical production, fuel combustion, etc. Therefore, in some areas the composition of the atmosphere is noticeably different from ordinary air, which required the creation of a special service for observing and monitoring the level of atmospheric air pollution.

Evolution of the atmosphere. The modern atmosphere is apparently of secondary origin: it was formed from gases released by the solid shell of the Earth after the formation of the planet was completed about 4.5 billion years ago. During the geological history of the Earth, the atmosphere has undergone significant changes in its composition under the influence of a number of factors: dissipation (volatilization) of gases, mainly lighter ones, into outer space; release of gases from the lithosphere as a result of volcanic activity; chemical reactions between the components of the atmosphere and the rocks that make up the earth’s crust; photochemical reactions in the atmosphere itself under the influence of solar UV radiation; accretion (capture) of matter from the interplanetary medium (for example, meteoric matter). The development of the atmosphere is closely related to geological and geochemical processes, and over the last 3-4 billion years also to the activity of the biosphere. A significant part of the gases that make up the modern atmosphere (nitrogen, carbon dioxide, water vapor) arose during volcanic activity and intrusion, which carried them from the depths of the Earth. Oxygen appeared in appreciable quantities about 2 billion years ago as a result of photosynthetic organisms that originally arose in the surface waters of the ocean.

Based on data on the chemical composition of carbonate deposits, estimates of the amount of carbon dioxide and oxygen in the atmosphere of the geological past were obtained. Throughout the Phanerozoic (the last 570 million years of Earth's history), the amount of carbon dioxide in the atmosphere varied widely depending on the level of volcanic activity, ocean temperature and the rate of photosynthesis. For most of this time, the concentration of carbon dioxide in the atmosphere was significantly higher than today (up to 10 times). The amount of oxygen in the Phanerozoic atmosphere changed significantly, with a prevailing trend towards its increase. In the Precambrian atmosphere, the mass of carbon dioxide was, as a rule, greater, and the mass of oxygen was smaller compared to the Phanerozoic atmosphere. Fluctuations in the amount of carbon dioxide had a significant impact on the climate in the past, increasing the greenhouse effect with increasing concentrations of carbon dioxide, making the climate much warmer throughout the main part of the Phanerozoic compared to the modern era.

Atmosphere and life. Without an atmosphere, the Earth would be a dead planet. Organic life occurs in close interaction with the atmosphere and the associated climate and weather. Insignificant in mass compared to the planet as a whole (about a part in a million), the atmosphere is an indispensable condition for all forms of life. The most important of the atmospheric gases for the life of organisms are oxygen, nitrogen, water vapor, carbon dioxide, and ozone. When carbon dioxide is absorbed by photosynthetic plants, organic matter is created, which is used as a source of energy by the vast majority of living beings, including humans. Oxygen is necessary for the existence of aerobic organisms, for which the flow of energy is provided by oxidation reactions of organic matter. Nitrogen, assimilated by some microorganisms (nitrogen fixers), is necessary for the mineral nutrition of plants. Ozone, which absorbs hard UV radiation from the Sun, significantly weakens this part of solar radiation harmful to life. The condensation of water vapor in the atmosphere, the formation of clouds and subsequent precipitation supply water to land, without which no form of life is possible. The vital activity of organisms in the hydrosphere is largely determined by the amount and chemical composition of atmospheric gases dissolved in water. Since the chemical composition of the atmosphere significantly depends on the activities of organisms, the biosphere and atmosphere can be considered as part of a single system, the maintenance and evolution of which (see Biogeochemical cycles) was of great importance for changing the composition of the atmosphere throughout the history of the Earth as a planet.

Radiation, heat and water balances of the atmosphere. Solar radiation is practically the only source of energy for all physical processes in the atmosphere. The main feature of the radiation regime of the atmosphere is the so-called greenhouse effect: the atmosphere transmits solar radiation to the earth's surface quite well, but actively absorbs thermal long-wave radiation from the earth's surface, part of which returns to the surface in the form of counter radiation, compensating for radiative heat loss from the earth's surface (see Atmospheric radiation ). In the absence of an atmosphere, the average temperature of the earth's surface would be -18°C, but in reality it is 15°C. Incoming solar radiation is partially (about 20%) absorbed into the atmosphere (mainly by water vapor, water droplets, carbon dioxide, ozone and aerosols), and is also scattered (about 7%) by aerosol particles and density fluctuations (Rayleigh scattering). The total radiation reaching the earth's surface is partially (about 23%) reflected from it. The reflectance coefficient is determined by the reflectivity of the underlying surface, the so-called albedo. On average, the Earth's albedo for the integral flux of solar radiation is close to 30%. It varies from a few percent (dry soil and black soil) to 70-90% for freshly fallen snow. Radiative heat exchange between the earth's surface and the atmosphere significantly depends on albedo and is determined by the effective radiation of the earth's surface and the counter-radiation of the atmosphere absorbed by it. The algebraic sum of radiation fluxes entering the earth's atmosphere from outer space and leaving it back is called the radiation balance.

Transformations of solar radiation after its absorption by the atmosphere and the earth's surface determine the heat balance of the Earth as a planet. The main source of heat for the atmosphere is the earth's surface; heat from it is transferred not only in the form of long-wave radiation, but also by convection, and is also released during condensation of water vapor. The shares of these heat inflows are on average 20%, 7% and 23%, respectively. About 20% of heat is also added here due to the absorption of direct solar radiation. The flux of solar radiation per unit time through a single area perpendicular to the sun's rays and located outside the atmosphere at an average distance from the Earth to the Sun (the so-called solar constant) is equal to 1367 W/m2, changes are 1-2 W/m2 depending on cycle of solar activity. With a planetary albedo of about 30%, the time-average global influx of solar energy to the planet is 239 W/m2. Since the Earth as a planet emits on average the same amount of energy into space, then, according to the Stefan-Boltzmann law, the effective temperature of the outgoing thermal long-wave radiation is 255 K (-18 ° C). At the same time, the average temperature of the earth's surface is 15°C. The difference of 33°C is due to the greenhouse effect.

The water balance of the atmosphere generally corresponds to the equality of the amount of moisture evaporated from the Earth's surface and the amount of precipitation falling on the Earth's surface. The atmosphere over the oceans receives more moisture from evaporation processes than over land, and loses 90% in the form of precipitation. Excess water vapor over the oceans is transported to the continents by air currents. The amount of water vapor transferred into the atmosphere from the oceans to the continents is equal to the volume of the rivers flowing into the oceans.

Air movement. The Earth is spherical, so much less solar radiation reaches its high latitudes than the tropics. As a result, large temperature contrasts arise between latitudes. The temperature distribution is also significantly affected by the relative positions of the oceans and continents. Due to the large mass of ocean waters and the high heat capacity of water, seasonal fluctuations in ocean surface temperature are much less than on land. In this regard, in the middle and high latitudes, the air temperature over the oceans in summer is noticeably lower than over the continents, and higher in winter.

Uneven heating of the atmosphere in different regions of the globe causes a spatially inhomogeneous distribution of atmospheric pressure. At sea level, the pressure distribution is characterized by relatively low values ​​near the equator, increases in the subtropics (high pressure belts) and decreases in the middle and high latitudes. At the same time, over the continents of extratropical latitudes, the pressure is usually increased in winter and decreased in summer, which is associated with temperature distribution. Under the influence of a pressure gradient, air experiences acceleration directed from areas of high pressure to areas of low pressure, which leads to the movement of air masses. Moving air masses are also affected by the deflecting force of the Earth's rotation (Coriolis force), the friction force, which decreases with height, and, for curved trajectories, the centrifugal force. Turbulent mixing of air is of great importance (see Turbulence in the atmosphere).

A complex system of air currents (general atmospheric circulation) is associated with the planetary pressure distribution. In the meridional plane, on average, two or three meridional circulation cells can be traced. Near the equator, heated air rises and falls in the subtropics, forming a Hadley cell. The air of the reverse Ferrell cell also descends there. At high latitudes, a straight polar cell is often visible. Meridional circulation velocities are on the order of 1 m/s or less. Due to the Coriolis force, westerly winds are observed in most of the atmosphere with speeds in the middle troposphere of about 15 m/s. There are relatively stable wind systems. These include trade winds - winds blowing from high pressure zones in the subtropics to the equator with a noticeable eastern component (from east to west). Monsoons are fairly stable - air currents that have a clearly defined seasonal character: they blow from the ocean to the mainland in the summer and in the opposite direction in the winter. The Indian Ocean monsoons are especially regular. In mid-latitudes, the movement of air masses is mainly westerly (from west to east). This is a zone of atmospheric fronts on which large vortices arise - cyclones and anticyclones, covering many hundreds and even thousands of kilometers. Cyclones also occur in the tropics; here they are distinguished by their smaller sizes, but very high wind speeds, reaching hurricane force (33 m/s or more), the so-called tropical cyclones. In the Atlantic and eastern Pacific Oceans they are called hurricanes, and in the western Pacific Ocean they are called typhoons. In the upper troposphere and lower stratosphere, in the areas separating the direct Hadley meridional circulation cell and the reverse Ferrell cell, relatively narrow, hundreds of kilometers wide, jet streams with sharply defined boundaries are often observed, within which the wind reaches 100-150 and even 200 m/ With.

Climate and weather. The difference in the amount of solar radiation arriving at different latitudes to the earth's surface, which is varied in its physical properties, determines the diversity of the Earth's climates. From the equator to tropical latitudes, the air temperature at the earth's surface averages 25-30°C and varies little throughout the year. In the equatorial belt, there is usually a lot of precipitation, which creates conditions of excess moisture there. In tropical zones, precipitation decreases and in some areas becomes very low. Here are the vast deserts of the Earth.

In subtropical and middle latitudes, air temperature varies significantly throughout the year, and the difference between summer and winter temperatures is especially large in areas of the continents far from the oceans. Thus, in some areas of Eastern Siberia, the annual air temperature range reaches 65°C. Humidification conditions in these latitudes are very diverse, depend mainly on the regime of general atmospheric circulation and vary significantly from year to year.

In polar latitudes, the temperature remains low throughout the year, even if there is a noticeable seasonal variation. This contributes to the widespread distribution of ice cover on the oceans and land and permafrost, which occupy over 65% of its area in Russia, mainly in Siberia.

Over the past decades, changes in the global climate have become increasingly noticeable. Temperatures rise more at high latitudes than at low latitudes; more in winter than in summer; more at night than during the day. Over the 20th century, the average annual air temperature at the earth's surface in Russia increased by 1.5-2°C, and in some areas of Siberia an increase of several degrees was observed. This is associated with an increase in the greenhouse effect due to an increase in the concentration of trace gases.

The weather is determined by the conditions of atmospheric circulation and the geographical location of the area; it is most stable in the tropics and most variable in the middle and high latitudes. The weather changes most of all in zones of changing air masses caused by the passage of atmospheric fronts, cyclones and anticyclones carrying precipitation and increased wind. Data for weather forecasting are collected at ground-based weather stations, ships and aircraft, and from meteorological satellites. See also Meteorology.

Optical, acoustic and electrical phenomena in the atmosphere. When electromagnetic radiation propagates in the atmosphere, as a result of refraction, absorption and scattering of light by air and various particles (aerosol, ice crystals, water drops), various optical phenomena arise: rainbows, crowns, halo, mirage, etc. The scattering of light determines the apparent height of the vault of heaven and blue color of the sky. The visibility range of objects is determined by the conditions of light propagation in the atmosphere (see Atmospheric visibility). The transparency of the atmosphere at different wavelengths determines the communication range and the ability to detect objects with instruments, including the possibility of astronomical observations from the Earth’s surface. For studies of optical inhomogeneities of the stratosphere and mesosphere, the twilight phenomenon plays an important role. For example, photographing twilight from spacecraft makes it possible to detect aerosol layers. Features of the propagation of electromagnetic radiation in the atmosphere determine the accuracy of methods for remote sensing of its parameters. All these questions, as well as many others, are studied by atmospheric optics. Refraction and scattering of radio waves determine the possibilities of radio reception (see Propagation of radio waves).

The propagation of sound in the atmosphere depends on the spatial distribution of temperature and wind speed (see Atmospheric acoustics). It is of interest for atmospheric sensing by remote methods. Explosions of charges launched by rockets into the upper atmosphere provided rich information about wind systems and temperature variations in the stratosphere and mesosphere. In a stably stratified atmosphere, when the temperature decreases with height slower than the adiabatic gradient (9.8 K/km), so-called internal waves arise. These waves can propagate upward into the stratosphere and even into the mesosphere, where they attenuate, contributing to increased winds and turbulence.

The negative charge of the Earth and the resulting electric field, the atmosphere, together with the electrically charged ionosphere and magnetosphere, create a global electrical circuit. The formation of clouds and thunderstorm electricity plays an important role in this. The danger of lightning discharges has necessitated the development of lightning protection methods for buildings, structures, power lines and communications. This phenomenon poses a particular danger to aviation. Lightning discharges cause atmospheric radio interference, called atmospherics (see Whistling atmospherics). During a sharp increase in the electric field strength, luminous discharges are observed that appear on the tips and sharp corners of objects protruding above the earth's surface, on individual peaks in the mountains, etc. (Elma lights). The atmosphere always contains a greatly varying amount of light and heavy ions, depending on specific conditions, which determine the electrical conductivity of the atmosphere. The main ionizers of air near the earth's surface are radiation from radioactive substances contained in the earth's crust and atmosphere, as well as cosmic rays. See also Atmospheric electricity.

Human influence on the atmosphere. Over the past centuries, there has been an increase in the concentration of greenhouse gases in the atmosphere due to human economic activities. The percentage of carbon dioxide increased from 2.8-10 2 two hundred years ago to 3.8-10 2 in 2005, the methane content - from 0.7-10 1 approximately 300-400 years ago to 1.8-10 -4 at the beginning of the 21st century; about 20% of the increase in the greenhouse effect over the last century came from freons, which were practically absent in the atmosphere until the mid-20th century. These substances are recognized as stratospheric ozone depleters, and their production is prohibited by the 1987 Montreal Protocol. The increase in the concentration of carbon dioxide in the atmosphere is caused by the burning of ever-increasing amounts of coal, oil, gas and other types of carbon fuels, as well as the clearing of forests, as a result of which the absorption of carbon dioxide through photosynthesis decreases. The concentration of methane increases with an increase in oil and gas production (due to its losses), as well as with the expansion of rice crops and an increase in the number of cattle. All this contributes to climate warming.

To change the weather, methods have been developed to actively influence atmospheric processes. They are used to protect agricultural plants from hail by dispersing special reagents in thunderclouds. There are also methods for dispersing fog at airports, protecting plants from frost, influencing clouds to increase precipitation in desired areas, or for dispersing clouds during public events.

Study of the atmosphere. Information about physical processes in the atmosphere is obtained primarily from meteorological observations, which are carried out by a global network of permanently operating meteorological stations and posts located on all continents and on many islands. Daily observations provide information about air temperature and humidity, atmospheric pressure and precipitation, cloudiness, wind, etc. Observations of solar radiation and its transformations are carried out at actinometric stations. Of great importance for studying the atmosphere are networks of aerological stations, at which meteorological measurements are carried out up to an altitude of 30-35 km using radiosondes. At a number of stations, observations of atmospheric ozone, electrical phenomena in the atmosphere, and the chemical composition of the air are carried out.

Data from ground stations are supplemented by observations on the oceans, where “weather ships” operate, constantly located in certain areas of the World Ocean, as well as meteorological information received from research and other ships.

In recent decades, an increasing amount of information about the atmosphere has been obtained using meteorological satellites, which carry instruments for photographing clouds and measuring fluxes of ultraviolet, infrared and microwave radiation from the Sun. Satellites make it possible to obtain information about vertical profiles of temperature, cloudiness and its water supply, elements of the radiation balance of the atmosphere, ocean surface temperature, etc. Using measurements of the refraction of radio signals from a system of navigation satellites, it is possible to determine vertical profiles of density, pressure and temperature, as well as moisture content in the atmosphere . With the help of satellites, it has become possible to clarify the value of the solar constant and planetary albedo of the Earth, build maps of the radiation balance of the Earth-atmosphere system, measure the content and variability of small atmospheric pollutants, and solve many other problems of atmospheric physics and environmental monitoring.

Lit.: Budyko M.I. Climate in the past and future. L., 1980; Matveev L. T. Course of general meteorology. Atmospheric physics. 2nd ed. L., 1984; Budyko M.I., Ronov A.B., Yanshin A.L. History of the atmosphere. L., 1985; Khrgian A. Kh. Atmospheric Physics. M., 1986; Atmosphere: Directory. L., 1991; Khromov S.P., Petrosyants M.A. Meteorology and climatology. 5th ed. M., 2001.

G. S. Golitsyn, N. A. Zaitseva.

STRUCTURE OF THE BIOSPHERE

Biosphere- the geological shell of the Earth, populated by living organisms, under their influence and occupied by the products of their vital activity; “film of life”; global ecosystem of the Earth.

The term " biosphere"was introduced in biology by Jean-Baptiste Lamarck (Fig. 4.18) at the beginning of the 19th century, and in geology it was proposed by the Austrian geologist Eduard Suess (Fig. 4.19) in 1875.

A holistic doctrine of the biosphere was created by the Russian biogeochemist and philosopher V.I. Vernadsky. For the first time, he assigned living organisms the role of the main transformative force on planet Earth, taking into account their activities not only at the present time, but also in the past.

The biosphere is located at the intersection of the upper part of the lithosphere, the lower part of the atmosphere and occupies the entire hydrosphere (Fig. 4.1).

Fig.4.1 Biosphere

Boundaries of the biosphere

• Upper limit in the atmosphere: 15÷20 km. It is determined by the ozone layer, which blocks short-wave UV radiation, which is harmful to living organisms.
• Lower boundary in the lithosphere: 3.5÷7.5 km. It is determined by the temperature of transition of water into steam and the temperature of denaturation of proteins, but generally the distribution of living organisms is limited to a depth of several meters.
• Lower limit in the hydrosphere: 10÷11 km. It is determined by the bottom of the World Ocean, including bottom sediments.

The biosphere is composed of the following types of substances:

1. Living matter- the entire set of bodies of living organisms inhabiting the Earth is physical and chemically united, regardless of their systematic affiliation. The mass of living matter is relatively small and is estimated at 2.4-3.6 10 12 tons (dry weight) and is less than 10 -6 the mass of other shells of the Earth. But this is “one of the most powerful geochemical forces on our planet,” since living matter not only inhabits the biosphere, but transforms the appearance of the Earth. Living matter is distributed very unevenly within the biosphere.
2. Nutrient- a substance created and processed by living matter. During organic evolution, living organisms passed through their organs, tissues, cells, and blood a thousand times through the entire atmosphere, the entire volume of the world's oceans, and a huge mass of mineral substances. This geological role of living matter can be imagined from deposits of coal, oil, carbonate rocks, etc.
3. Inert substance- in the formation of which life does not participate; solid, liquid and gaseous.
4. Bioinert substance, which is created simultaneously by living organisms and inert processes, representing dynamically equilibrium systems of both. These are soil, silt, weathering crust, etc. Organisms play a leading role in them.
5. Substance undergoing radioactive decay.
6. Scattered atoms, continuously created from all kinds of terrestrial matter under the influence of cosmic radiation.
7. Substance of cosmic origin.

Structure of the earth

There is mostly speculative information about the structure, composition and properties of the “solid” Earth, since only the uppermost part of the earth’s crust is accessible to direct observation. The most reliable of them are seismic methods, based on the study of the paths and speed of propagation of elastic vibrations (seismic waves) in the Earth. With their help, it was possible to establish the division of the “solid” Earth into separate spheres and get an idea of ​​the internal structure of the Earth.” It turns out that the generally accepted idea of ​​the deep structure of the globe is an assumption, because it was not created based on direct factual data. In geography textbooks, the earth's crust, mantle and core are reported as real-life objects without a shadow of doubt about their possible fictitiousness. The term “earth’s crust” appeared in the middle of the 19th century, when the hypothesis of the formation of the Earth from a hot gas ball, currently called the Kant-Laplace hypothesis, gained recognition in natural science. The thickness of the earth's crust was assumed to be 10 miles (16 km). Below is the primordial molten material preserved from the formation of our planet.

In 1909 On the Balkan Peninsula, near the city of Zagreb, a strong earthquake occurred. Croatian geophysicist Andrija Mohorovicic, studying a seismogram recorded at the time of this event, noticed that at a depth of about 30 km the wave speed increases significantly. This observation was confirmed by other seismologists. This means that there is a certain section limiting the earth’s crust from below. To designate it, a special term was introduced - the Mohorovicic surface (or Moho section) (Fig. 4.2).

Fig. 4.2 Mantle, asthenosphere, Mohorovicic surface

The Earth is encased in a hard outer shell, or lithosphere, consisting of a crust and a hard upper layer of mantle. The lithosphere is split into huge blocks, or plates. Under the pressure of powerful underground forces, these plates are constantly moving (Fig. 4.3). In some places, their movement leads to the emergence of mountain ranges, in others the edges of the plates are pulled into deep depressions. This phenomenon is called underthrust, or subduction. As the plates shift, they either connect or split, and the zones of their junctions are called boundaries. It is in these weakest points of the earth's crust that volcanoes most often arise.

Fig. 4.3 Earth Plates

Under the crust at depths from 30-50 to 2900 km is the Earth's mantle. It consists mainly of rocks rich in magnesium and iron. The mantle occupies up to 82% of the planet's volume and is divided into upper and lower. The first lies below the Moho surface to a depth of 670 km. A rapid drop in pressure in the upper part of the mantle and high temperature lead to the melting of its substance. At a depth of 400 km under continents and 10-150 km under oceans, i.e. in the upper mantle, a layer was discovered where seismic waves travel relatively slowly. This layer was called the asthenosphere (from the Greek “asthenes” - weak). Here the proportion of melt is 1-3%, more plastic than the rest of the mantle. The asthenosphere serves as a “lubricant” along which rigid lithospheric plates move. Compared to the rocks that make up the earth's crust, the rocks of the mantle are distinguished by their high density and the speed of propagation of seismic waves in them is noticeably higher. In the very “basement” of the lower mantle - at a depth of 1000 km and up to the surface of the core - the density gradually increases. What the lower mantle consists of remains a mystery.

Fig.4.4 Proposed structure of the Earth

It is assumed that the surface of the core consists of a substance with the properties of a liquid. The core boundary is located at a depth of 2900 km. But the inner region, starting from a depth of 5100 km, should behave like a solid body. This must be due to very high blood pressure. Even at the upper boundary of the core, the theoretically calculated pressure is about 1.3 million atm. and in the center it reaches 3 million atm. The temperature here can exceed 10,000 o C. However, how valid these assumptions are can only be guessed at (Fig. 4.4). The very first test by drilling of the structure of the earth's crust of the continental type from the granite layer and below it the basalt layer gave different results. We are talking about the results of drilling the Kola superdeep well (Fig. 4.5). It was founded in the north of the Kola Peninsula for purely scientific purposes to uncover the supposedly predicted basalt layer at a depth of 7 km. There rocks have a velocity of longitudinal seismic waves of 7.0-7.5 km/s. According to these data, the basalt layer is identified everywhere. This location was chosen because, according to geophysical data, the basalt layer within the USSR is located here closest to the surface of the lithosphere. Above are rocks with longitudinal wave velocities of 6.0-6.5 km/s - a granite layer.

Fig. 4.5 Kola superdeep well

The real section opened by the Kola superdeep well turned out to be completely different. To a depth of 6842 m, sandstones and tuffs of basaltic composition with bodies of dolerites (cryptocrystalline basalts) are common, and below - gneisses, granite-gneisses, and less commonly - amphibolites. The most important thing in the results of drilling the Kola superdeep well, the only one drilled on Earth deeper than 12 km, is that they not only refuted the generally accepted idea of ​​​​the structure of the upper part of the lithosphere, but that before they were obtained it was generally impossible to talk about the material structure of these depths globe. However, neither school nor university textbooks on geography and geology report the results of drilling the Kola superdeep well, and the presentation of the Lithosphere section begins with what is said about the core, mantle and crust, which on the continents is composed of a granite layer, and below - a basalt layer.

Earth's atmosphere

Atmosphere Earth - the air shell of the Earth, consisting mainly of gases and various impurities (dust, water drops, ice crystals, sea salts, combustion products), the amount of which is not constant. The atmosphere up to an altitude of 500 km consists of the troposphere, stratosphere, mesosphere, ionosphere (thermosphere), exosphere (Fig. 4.6)

Fig. 4.6 The structure of the atmosphere up to an altitude of 500 km

Troposphere- the lower, most studied layer of the atmosphere, 8-10 km high in the polar regions, up to 10-12 km in temperate latitudes, and 16-18 km at the equator. The troposphere contains approximately 80-90% of the total mass of the atmosphere and almost all water vapor. When rising every 100 m, the temperature in the troposphere decreases by an average of 0.65° and reaches 220 K (−53°C) in the upper part. This upper layer of the troposphere is called the tropopause.

Stratosphere- a layer of the atmosphere located at an altitude of 11 to 50 km. Characterized by a slight change in temperature in the 11-25 km layer (lower layer of the stratosphere) and an increase in temperature in the 25-40 km layer from −56.5 to 0.8 ° C (upper layer of the stratosphere or inversion region). Having reached a value of about 273 K (about 0°C) at an altitude of about 40 km, the temperature remains constant up to an altitude of about 55 km. This region of constant temperature is called the stratopause and is the boundary between the stratosphere and mesosphere. It is in the stratosphere that the ozone layer (“ozone layer”) is located (at an altitude of 15-20 to 55-60 km), which determines the upper limit of life in the biosphere. An important component of the stratosphere and mesosphere is O 3, which is formed as a result of photochemical reactions most intensely at an altitude of ~ 30 km. The total mass of O 3 would be a layer 1.7-4.0 mm thick at normal pressure, but this is enough to absorb life-destructive UV radiation from the Sun. The destruction of O 3 occurs when it interacts with free radicals, NO, and halogen-containing compounds (including “freons”). In the stratosphere, most of the short-wave part of ultraviolet radiation (180-200 nm) is retained and the energy of short waves is transformed. Under the influence of these rays, magnetic fields change, molecules disintegrate, ionization occurs, and new formation of gases and other chemical compounds occurs. These processes can be observed in the form of northern lights, lightning, and other glows. In the stratosphere and higher layers, under the influence of solar radiation, gas molecules dissociate into atoms (above 80 km CO 2 and H 2 dissociate, above 150 km - O 2, above 300 km - H 2). At an altitude of 100-400 km, ionization of gases also occurs in the ionosphere; at an altitude of 320 km, the concentration of charged particles (O + 2, O − 2, N + 2) is ~ 1/300 of the concentration of neutral particles. In the upper layers of the atmosphere there are free radicals - OH, HO 2, etc. There is almost no water vapor in the stratosphere.

Mesosphere begins at an altitude of 50 km and extends to 80-90 km. The air temperature at an altitude of 75-85 km drops to −88°C. The upper limit of the mesosphere is the mesopause.

Thermosphere(another name is the ionosphere) - the layer of the atmosphere following the mesosphere - begins at an altitude of 80-90 km and extends up to 800 km. The air temperature in the thermosphere quickly and steadily increases and reaches several hundred and even thousands of degrees.

Exosphere- dispersion zone, the outer part of the thermosphere, located above 800 km. The gas in the exosphere is very rarefied, and from here its particles leak into interplanetary space

The concentrations of gases that make up the atmosphere in the ground layer are almost constant, with the exception of water (H 2 O) and carbon dioxide (CO 2). The change in the chemical composition of the atmosphere depending on altitude is shown in Fig. 4.7.

The change in pressure and temperature of the atmospheric layer up to a height of 35 km is shown in Fig. 4.8.

Fig. 4.7 Change in the chemical composition of the atmosphere in the number of gas atoms per 1 cm3 in height.

The composition of the surface layer of the atmosphere is given in Table 4.1:

Table 4.1

In addition to the gases indicated in the table, the atmosphere contains SO 2, CH 4, NH 3, CO, hydrocarbons, HCl, HF, Hg vapor, I 2, as well as NO and many other gases in small quantities.

Fig. 4.8 Change in pressure and temperature of the atmospheric layer up to an altitude of 35 km

The primary atmosphere of the Earth was similar to the atmosphere of other planets. Thus, 89% of Jupiter's atmosphere is hydrogen. Another approximately 10% is helium, the remaining fractions of a percent are occupied by methane, ammonia and ethane. There is also “snow” - both water and ammonia ice.

The atmosphere of Saturn also consists mainly of helium and hydrogen (Fig. 4.9)

Fig. 4.9 Atmosphere of Saturn

History of the formation of the Earth's atmosphere

1. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This is the so-called primary atmosphere.

2. Active volcanic activity has led to the saturation of the atmosphere with gases other than hydrogen (hydrocarbons, ammonia, water vapor). This is how it was formed secondary atmosphere.

3. The constant leakage of hydrogen into interplanetary space, chemical reactions occurring in the atmosphere under the influence of ultraviolet radiation, lightning discharges and some other factors led to the formation tertiary atmosphere.

4. With the appearance of living organisms on Earth as a result of photosynthesis, accompanied by the release of oxygen and absorption of carbon dioxide, the composition of the atmosphere began to change and gradually formed the modern quaternary atmosphere (Fig. 4.10). There is, however, data (analysis of the isotopic composition of atmospheric oxygen and that released during photosynthesis) that indicates the geological origin of atmospheric oxygen. The formation of oxygen from water is facilitated by radiation and photochemical reactions. However, their contribution is insignificant. Over the course of various eras, the composition of the atmosphere and oxygen content have undergone very significant changes. It is correlated with global extinctions, glaciations, and other global processes. The establishment of its equilibrium was apparently the result of the appearance of heterotrophic organisms on land and in the ocean and volcanic activity.

Fig. 4.10 Earth's atmosphere in different periods

Contrary to widespread misconception, the content of oxygen and nitrogen in the atmosphere is practically independent of forests. Fundamentally, a forest cannot significantly affect the CO 2 content in the atmosphere because it does not accumulate carbon. The vast majority of carbon is returned to the atmosphere as a result of the oxidation of fallen leaves and trees. A healthy forest is in balance with the atmosphere and gives back exactly as much as it takes into the “breathing” process. Moreover, tropical forests absorb oxygen more often, while the taiga “slightly” releases oxygen. In the 1990s, experiments were carried out to create a closed ecological system (“Biosphere 2”), during which it was not possible to create a stable system with a uniform air composition. The influence of microorganisms led to a decrease in oxygen levels by up to 15% and an increase in the amount of carbon dioxide.

Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the bulk (360 billion tons) coming from fuel combustion (Fig. 4.11). If the growth rate of fuel combustion continues, then

Fig. 4.11 Progress in increasing carbon dioxide concentrations and average temperatures in recent years.

over the next 50-60 years, the amount of CO 2 in the atmosphere will double and could lead to global climate change.

The principle of the greenhouse effect is illustrated in Figure 4.12.

Rice. 4.12 Principles of the greenhouse effect

The ozone layer is located in the stratosphere at altitudes from 15 to 35 km (Fig. 4.13):

Fig. 4.13 Structure of the ozone layer

In recent years, the concentration of ozone in the stratosphere has fallen sharply, which leads to an increase in the UV background on Earth, especially in the Antarctic region (Fig. 4.14).

Figure 4.14 Changes in the ozone layer over Antarctica

Hydrosphere

Hydrosphere(Greek Hydor- water + Sphaira- sphere) - the totality of all water reserves of the Earth, the intermittent water shell of the globe, located on the surface and in the thickness of the earth’s crust and representing the totality of oceans, seas and water bodies of land.

3/4 of the Earth's surface is occupied by oceans, seas, reservoirs, and glaciers. The amount of water in the ocean is not constant and changes over time due to various factors. Level fluctuations amount to up to 150 meters at different periods of the Earth’s existence. Groundwater is the connecting link of the entire hydrosphere. Only groundwater occurring at depths of up to 5 km is taken into account. They close the geological water cycle. Their number is estimated at 10-5 thousand cubic km or about 7% of the entire hydrosphere.

Ice and snow in quantity are one of the most important components of the hydrosphere. The mass of water in glaciers is 2.6x10 7 billion tons.

Soil water plays a huge role in the biosphere, because... It is because of water that biochemical processes occur in the soil that ensure soil fertility. The mass of soil water is estimated at 8x10 3 billion tons.

Rivers have the least amount of water in the biosphere. Water reserves in rivers are estimated at 1-2x10 3 billion tons. River waters are usually fresh, their mineralization is unstable and varies with the seasons. Rivers flow along tectonically formed relief depressions.

Atmospheric water combines the hydrosphere and atmosphere. Atmospheric moisture is always fresh. The mass of atmospheric water is 14x10 3 billion tons. Its importance for the biosphere is very great. The average time for water circulation between the hydrosphere and the atmosphere is 9-10 days.

A significant part of the water is in the biosphere in a bound state in living organisms - 1.1x10 3 billion tons. In an aquatic environment, plants continuously filter water through their surface. On land, plants extract water from the soil with their roots and transpire it with their above-ground parts. To synthesize 1 gram of biomass, plants must evaporate about 100 grams of water (Plankton filters all the ocean water through itself in about 1 year).

The ratio of salty and fresh water in the hydrosphere is shown in Fig. 4.15

Fig. 4.15 The ratio of salt and fresh water in the hydrosphere

Most of the water is concentrated in the ocean, much less in the continental river network and groundwater. There are also large reserves of water in the atmosphere, in the form of clouds and water vapor. Over 96% of the volume of the hydrosphere is made up of seas and oceans, about 2% is groundwater, about 2% is ice and snow, and about 0.02% is land surface water. Some of the water is in a solid state in the form of glaciers, snow cover and permafrost, representing the cryosphere. Surface waters, occupying a relatively small share of the total mass of the hydrosphere, nevertheless play a vital role in the life of our planet, being the main source of water supply, irrigation and water supply. The waters of the hydrosphere are in constant interaction with the atmosphere, the earth's crust and the biosphere. The interaction of these waters and mutual transitions from one type of water to another constitute a complex water cycle on the globe. Life on Earth first originated in the hydrosphere. Only at the beginning of the Paleozoic era did the gradual migration of animals and plant organisms to land begin.

One of the most important functions of the hydrosphere is heat storage, leading to the global water cycle in the biosphere. Heating of surface waters by the Sun (Fig. 4.16) leads to the redistribution of heat throughout the planet.

Fig. 4.16 Temperature of surface ocean waters

Life in the hydrosphere is distributed extremely unevenly. A significant part of the hydrosphere has a weak population of organisms. This is especially true in the ocean depths, where there is little light and relatively low temperatures.

Main surface currents:

In the northern part of the Pacific Ocean: warm - Kuroshio, North Pacific and Alaskan; cold - Californian and Kuril. In the southern part: warm - South Trade Wind and East Australian; cold - Western Winds and Peruvian (Fig. 4.17). The currents of the North Atlantic Ocean are closely coordinated with the currents of the Arctic Ocean. In the central Atlantic, water is heated and moved north by the Gulf Stream, where the water cools and sinks into the depths of the Arctic Ocean.

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The formation of the Earth's atmosphere began in ancient times - during the protoplanetary stage of the Earth's development, during a period of active volcanic eruptions with the release of huge amounts of gases. Later, when oceans and the biosphere appeared on Earth, the formation of the atmosphere continued due to gas exchange between water, plants, animals and the products of their decomposition.

Throughout geological history, the Earth's atmosphere has undergone a number of profound transformations.

The Earth's primary atmosphere. Restorative.

Part Earth's primary atmosphere at the protoplanetary stage of the Earth's development (more than 4.2 billion years ago) it consisted mainly of methane, ammonia and carbon dioxide. Then, as a result of degassing of the Earth's mantle and continuous weathering processes on the earth's surface, the composition of the Earth's primary atmosphere was enriched with water vapor, carbon (CO 2 , CO) and sulfur compounds, as well as strong halogen acids (HCI, HF, HI) and boric acid. The primary atmosphere was very thin.

Secondary atmosphere of the Earth. Oxidative.

Subsequently, the primary atmosphere began to transform into a secondary one. This happened as a result of the same weathering processes that occurred on the surface of the earth, volcanic and solar activity, as well as due to the activity of cyanobacteria and blue-green algae.

The result of the transformation was the decomposition of methane into hydrogen and carbon dioxide, and ammonia into nitrogen and hydrogen. Carbon dioxide and nitrogen began to accumulate in the Earth's atmosphere.

Blue-green algae began to produce oxygen through photosynthesis, which was almost all spent on the oxidation of other gases and rocks. As a result, ammonia was oxidized to molecular nitrogen, methane and carbon monoxide to carbon dioxide, sulfur and hydrogen sulfide to SO 2 and SO 3.

Thus, the atmosphere gradually turned from reducing to oxidizing.

Formation and evolution of carbon dioxide in the primary and secondary atmosphere.

Sources of carbon dioxide in the early stages of the formation of the Earth's atmosphere:

• Methane oxidation,
• Degassing of the Earth's mantle,
• Weathering of rocks.

At the turn of the Proterozoic and Paleozoic (ca. 600 million years ago), the content of carbon dioxide in the atmosphere decreased and amounted to only tenths of a percent of the total volume of gases in the atmosphere.

Carbon dioxide reached its current level in the atmosphere only 10-20 million years ago.

Formation and evolution of oxygen in the primary and secondary atmosphere of the Earth.

Oxygen sources in the early stages of atmospheric formation Lands:

• Degassing of the Earth's mantle - almost all the oxygen was spent on oxidative processes.
• Photodissociation of water (decomposition into hydrogen and oxygen molecules) in the atmosphere under the influence of ultraviolet radiation - as a result, free oxygen molecules appeared in the atmosphere.
• Conversion of carbon dioxide into oxygen by eukaryotes. The appearance of free oxygen in the atmosphere led to the death of prokaryotes (adapted to living in reducing conditions) and the emergence of eukaryotes (adapted to living in an oxidizing environment).

Changes in oxygen concentration in the Earth's atmosphere.

Archean - first half of the Proterozoic – oxygen concentration is 0.01% of the modern level (Yuri point). Almost all of the resulting oxygen was spent on the oxidation of iron and sulfur. This continued until all the divalent iron on the surface of the earth was oxidized. From that moment on, oxygen began to accumulate in the atmosphere.

Second half of the Proterozoic – end of the Early Vendian – oxygen concentration in the atmosphere is 0.1% of the current level (Pasteur point).

Late Vendian - Silurian period. Free oxygen stimulated the development of life - the anaerobic fermentation process was replaced by energetically more promising and progressive oxygen metabolism. From this point on, the accumulation of oxygen in the atmosphere occurred quite quickly. The emergence of plants from the sea onto land (450 million years ago) led to the stabilization of oxygen levels in the atmosphere.

Mid Cretaceous . The final stabilization of oxygen concentration in the atmosphere is associated with the appearance of flowering plants (100 million years ago).

Formation and evolution of nitrogen in the primary and secondary atmosphere of the Earth.

Nitrogen was formed in the early stages of the Earth's development due to the decomposition of ammonia. The fixation of atmospheric nitrogen and its burial in marine sediments began with the appearance of organisms. After living organisms reached land, nitrogen began to be buried in continental sediments. The process of nitrogen fixation especially intensified with the advent of land plants.

Thus, the composition of the Earth’s atmosphere determined the characteristics of the life activity of organisms, contributed to their evolution, development and settlement on the surface of the earth. But in the history of the Earth, there have sometimes been disruptions in the distribution of gas composition. The reason for this was various catastrophes that occurred more than once during the Cryptozoic and Phanerozoic. These failures led to mass extinctions of the organic world.

The composition of the ancient and modern atmosphere of the Earth in percentage terms is given in Table 1.

Table 1. Composition of the primary and modern atmosphere of the Earth.

Gases	Composition of the earth's atmosphere
	Primary atmosphere, %	Modern atmosphere, %
Nitrogen N 2
Oxygen O 2
Ozone O 3
Carbon dioxide CO 2
Carbon monoxide CO
water vapor
Argon Ar

It was the article “Formation of the Earth's atmosphere. Primary and secondary atmosphere of the Earth." Read further: «

The atmosphere is the gaseous shell of the Earth; it is thanks to the atmosphere that the origin and further development of life on our planet became possible. The importance of the atmosphere for the Earth is colossal - the atmosphere will disappear, the planet will disappear. But lately, from television screens and radio speakers, we have been hearing more and more often about the problem of air pollution, the problem of destruction of the ozone layer, and the harmful effects of solar radiation on living organisms, including humans. Here and there, environmental disasters occur that have varying degrees of negative impact on the earth’s atmosphere, directly affecting its gas composition. Unfortunately, we have to admit that with every year of human industrial activity the atmosphere becomes less and less suitable for the normal functioning of living organisms.

The appearance of the atmosphere

The age of the atmosphere is usually equated to the age of planet Earth itself - approximately 5000 million years. At the initial stage of its formation, the Earth warmed up to impressive temperatures. “If, as most scientists believe, the newly formed Earth was extremely hot (had a temperature of about 9000 ° C), then most of the gases that made up the atmosphere would have left it. As the Earth gradually cooled and solidified, gases dissolved in the liquid crust would escape from it.” From these gases the primary earth's atmosphere was formed, thanks to which the origin of life became possible.

As soon as the Earth cooled, an atmosphere formed around it from the released gases. Unfortunately, it is not possible to determine the exact percentage of elements in the chemical composition of the primary atmosphere, but it can be accurately assumed that the gases included in its composition were similar to those that are now emitted by volcanoes - carbon dioxide, water vapor and nitrogen. “Volcanic gases in the form of superheated water vapor, carbon dioxide, nitrogen, hydrogen, ammonia, acid fumes, noble gases and oxygen formed the proto-atmosphere. At this time, the accumulation of oxygen in the atmosphere did not occur, since it was spent on the oxidation of acidic fumes (HCl, SiO 2, H 2 S)” (1).

There are two theories about the origin of the most important chemical element for life - oxygen. As the Earth cooled, the temperature dropped to about 100° C, most of the water vapor condensed and fell to the earth's surface as the first rain, resulting in the formation of rivers, seas and oceans - the hydrosphere. “The water shell on Earth provided the possibility of accumulating endogenous oxygen, becoming its accumulator and (when saturated) supplier to the atmosphere, which by this time had already been cleared of water, carbon dioxide, acidic fumes, and other gases as a result of past rainstorms” (1).

Another theory states that oxygen was formed during photosynthesis as a result of the life activity of primitive cellular organisms, when plant organisms settled throughout the Earth, the amount of oxygen in the atmosphere began to increase rapidly. However, many scientists tend to consider both versions without mutual exclusion.

Changes in the composition of the Earth's atmosphere

Stages of development of life on Earth		Change in atmospheric composition
Education of the planet	4.5 – 5 billion years ago	No atmosphere
The appearance of signs of life on Earth	2.5 – 3 billion years ago	The primary atmosphere contains no oxygen
Active conquest of the Earth by living organisms