We all know that the shape of the Earth is spherical. This structure is reflected in the distribution of solar radiation over its surface, which naturally decreases from the equator to the poles. This phenomenon is associated with the thermal regime of the Earth's surface, the consistent distribution of landscapes, and the patterns of the spatial state of the components of nature. This well-known global pattern is called geographic zonation.
The root cause of the formation of geographic zonality is considered to be the uneven distribution of solar radiation over the earth's surface and the unequal receipt of thermal energy per unit area. The existence of geographic zonality on the Earth's surface is not only the result of the uneven distribution of solar radiation, but also the intrinsic properties of the geographic shell. Evidence of this is the boundaries of geographical zones, which are not located at the same latitude, but change depending on one or another feature of the geographical envelope.
At the end of the 19th century, the famous Russian soil scientist V.V. Dokuchaev, having determined the unity and inextricable connection of the components of the geographical envelope, noted that these components naturally change from south to north and create natural (geographical) zones.
The scientist was also the first to notice that the formation of geographical zones is not only influenced by direct solar radiation, but also depends on the distribution of heat and moisture on the earth’s surface, especially on the comparative ratio of the latter two factors. This means that although natural zones are strips of landscapes successively located from the equator to the poles, their boundaries are not lines of parallels. Depending on the structure of the Earth’s surface, the distribution of moisture, the proximity of sea coasts and for other reasons, the signs of zones sometimes appear inconsistently, intermittently, sometimes appear, sometimes disappear temporarily (for example, deserts and semi-deserts, deciduous forests, etc.), and sometimes landscapes are formed not according to the zonal principle, but according to azonal factors.
Geographical zoning has a huge impact on human economic activity and on its relationship with the environment. For example, from the equator to the poles, a person spends more and more labor to ensure his life (construction, transport, production of clothing, food, etc.), his life support becomes more and more expensive.
Geographic zoning accelerates or slows down the course of similar natural processes and phenomena. For example, woody plants in the humid tropics and in the taiga grow at different rates; or take the productivity of 1 km2 of tundra pastures, which allows us to obtain only 800-900 kg of meat per year, while the productivity of African savannas reaches 27-30 tons. Thus, one cannot ignore zonality in the use of animal resources.
The geographic envelope is a natural complex on a global scale. It is divided into natural-territorial complexes of a lower rank (continent, ocean, country, region, etc.). Natural-territorial complexes at the local level are “tract” and “facies”. The main properties of a natural complex are the unity of its components, the continuous exchange of substances between these components and the directed flows of energy inherent in this complex.
According to the law of materialist dialectics: without knowing the whole, it is impossible to know its parts. Therefore, without knowing the patterns of development of the global system - the geographical shell, it is impossible to fully know the properties of natural complexes of the lowest rank, and based on the study of only one of these latter, it is impossible to identify the general patterns of the development of nature. The identified patterns for one of the components of the natural environment or on the basis of local territorial studies cannot be extended to all components or ranks of natural-territorial complexes. Environmental problems are multifaceted, diverse, and different in nature. Modern environmental problems are taking on a global scale, so their resolution must be comprehensive, taking into account the conditions of all components of the natural environment and the complexity of the problems.
Uneven distribution of solar heat on the surface of the Earth, due to its spherical shape and rotation around its axis, forms, as we have already said, climatic zones (p. 54). Each of them is characterized by a certain direction and rhythm of natural phenomena (accumulation of biomass, intensity of soil formation and relief formation under the influence of external factors, etc.). Therefore, based on climate zones, geographic zones can be distinguished.
There are 13 in total geographical zones: one equatorial, two subequatorial (in the northern and southern hemispheres), two tropical, two subtropical, two temperate, two subpolar (subarctic and subantarctic) and two polar (arctic and antarctic).
The very list of names already indicates the symmetrical arrangement of the belts in relation to the equator. Each of them is dominated by certain air masses. Belts bearing names without the prefix “ ” are characterized by their own air masses (equatorial, tropical, temperate, arctic). On the contrary, in three pairs having the prefix “sub”, neighboring geographical zones alternately dominate: in the summer half of the year in the northern hemisphere - the more southern one (and in the southern, on the contrary, - the northern one), in the winter half of the year - the more northern one (and in the southern hemisphere - southern).
Latitudinal geographical zones of land are heterogeneous. This is determined primarily by the position of one or another part of them in oceanic or continental regions. The oceanic ones are better moistened, while the continental, internal ones, on the contrary, are drier: the influence of the oceans no longer extends here. On this basis, belts are divided into sectors - oceanic And continental.
The sectorality is especially well expressed in the temperate and subtropical zones of Eurasia, where the land reaches its maximum size. Here, the humid forest landscapes of the oceanic margins (two oceanic sectors) as they move deeper into the continent are replaced by dry steppe, and then semi-desert and desert landscapes of the continental sector.
The sectorality is least clearly manifested in the tropical, subequatorial and equatorial zones. In the tropics they bring precipitation only to the eastern peripheries of the belts. This is where wet ones are common. As for the inland and western regions, they are distinguished by a dry, hot climate, and the deserts on the western coasts go right to the ocean. Therefore, only two sectors are distinguished in the tropics.
Two sectors are also distinguished in the equatorial and subequatorial belts. In the subequatorial regions, this is a constantly wet sector () with forest landscapes and a seasonally wet sector (including the rest of the part), occupied by woodlands and savannas. In the equatorial belt, part of the territory belongs to the constantly wet sector with wet “rain” forests (hylaea), and only the eastern part belongs to the seasonally wet sector, where predominantly deciduous forests are common.
The sharpest “sector boundary” is where it runs along mountain barriers (for example, in the Cordillera of North America and the Andes of South America). Here, the western oceanic sectors occupy a narrow coastal strip of plains and adjacent mountain slopes.
Large components of belts - sectors are divided into smaller units - natural areas. The basis for this division is the differences in the moisture conditions of the territory. However, it would be wrong to measure only the amount of precipitation. The ratio of moisture and heat is important here, since the amount of precipitation is the same, for example less than 150-200 mm per year. can lead to both the development of swamps (in the tundra) and the formation of deserts (in the tropics).
To characterize moisture, there are many quantitative indicators, more than two dozen coefficients or indices (dryness or humidity). However, they are not all perfect. For our topic - elucidating the influence of the ratio of heat and moisture on the differentiation of natural zones - it is better to take into account not the entire amount of precipitation for the year. but only the so-called gross moisture (precipitation runoff) and its contribution to the radiation balance, since it practically does not participate in biological processes. This indicator is called the “hydrothermal coefficient” (HTC). It expresses the basic zonal patterns more fully than others. If it has a value greater than 10, then wet (mainly forest) landscapes develop, if less than 7, herbaceous-shrub landscapes develop, and in the range from 7 to 10, transitional types; with a GTK less than 2 - deserts.
It is possible to construct heat and moisture relationships in the main natural land areas on the plains (see page 54). The space enclosed within the curve represents an arena for the development of natural landscapes.
The variety of landscapes is especially great in the hot climate zone. This is a result of the large differences here in humidification conditions at high temperatures. Scientists have long drawn attention to the connection between moisture conditions and the productivity of plant mass: it is highest in the deltaic regions of the sub-zknatorial belt - up to 3 thousand centners of dry matter per 1 hectare per year; deltas located at the junction of land and sea are most provided with moisture and necessary chemical elements in the soil, and in conditions of high temperatures the cycle continues here. The names of natural zones are given according to the nature of the vegetation, since it most clearly reflects the zonal features of nature. In the same natural areas on different continents, the vegetation cover has similar features. However, the distribution of vegetation is influenced not only by zonal climate features, but also by other factors: the evolution of continents, the characteristics of the rocks that make up the surface horizons, and human influence. The location of the continents also plays a significant role in the distribution of modern vegetation. Thus, the territorial proximity between Eurasia and North America, especially in the Pacific regions, led to the obvious similarity of vegetation in the polar regions of both continents. On the contrary, the vegetation cover of continents more distant from each other, located in the southern hemisphere, differs significantly in species composition. There are especially many endemics, i.e. species distributed in a limited area, in Australia due to its long-term isolation.
The main barriers to the migration routes of plants were not only the oceans, but also mountain ranges, although it happened that they also served as routes for plant dispersal.
All these factors determined the diversity of vegetation cover on the globe. In the next section, when describing natural zones, we will characterize the zonal type of vegetation, the properties of which most correspond to the climatic conditions of certain zones. However, in terms of species composition, the vegetation of identical natural zones on different continents is characterized by significant differences.
Natural zones of the Arctic, subarctic, temperate and subtropical zones are most pronounced in Eurasia and North America. This is due to the large size of the land in these latitudes and the vastness of the flat areas, since high mountains violate, as we will see below, the general features of zonation. Most of the continents of South America, Africa, as well as the southern part of Asia are located in the equatorial, subequatorial and tropical zones.
Belts and natural zones become more complex as you move from the Arctic regions to the equator. In this direction, against the backdrop of increasing heat, regional differences in humidification conditions are increasing. Hence the much more variegated nature of landscapes in tropical latitudes.
Along with the zonality of natural processes, there is a phenomenon called intrazonality. Intrazonal soils, vegetation cover, and various natural processes can arise in specific conditions and are found in separate areas in different natural zones. Moreover, usually ingrazonal phenomena bear the imprint of the corresponding zone; we will see this below with specific examples.
Natural areas are divided into smaller units - landscapes, which serve as the main cells of the geographical envelope.
In landscapes, all natural components are closely interconnected and interdependent, as if “fitted” to each other, that is, they form! natural. The diversity of landscapes is determined by many factors: the material composition and other features of the lithosphere, features of surface and groundwater, climate, the nature of soil and vegetation cover, as well as inherited, “yesterday’s” features.
At present, when the direct impact on nature of human economic activity is increasing, “virgin” landscapes are becoming “anthropogenic”.
In turn, landscapes, due to differences in microclimate, microrelief, soil subtypes, can be divided into smaller territorial complexes of a lower rank - tracts and facies - specific OBpai or their slopes, etc. Homogeneous landscapes are composed of identical and naturally repeating combinations of facies and tracts. At the same time, landscapes, of course, are not isolated and influence each other due to atmospheric circulation, migration of organisms, etc.
Local landscape features are individual and unique. But landscapes also have common zonal features that can be repeated even on different continents. For example, the Great Plains of North America resemble the steppe areas of temperate continental parts of Eurasia. With some abstraction, land landscapes can be generalized and typified, which makes it possible to trace the regular distribution of zonal types of landscapes not only on each continent separately, but also on a planetary scale.
To make it easier to understand the location of geographical belts and zones on our land, let’s imagine a hypothetical uniformly flat continent with an area equal to half the land area (let another part of the land, similar in surface structure, be located in another hemisphere, beyond the ocean). The outline of this continent in the northern hemisphere may resemble something between North America and Eurasia, and in the southern hemisphere it may resemble something between South America, Africa and Australia. Then, those drawn on the boundaries of geographical zones and zones will reflect their generalized () contours on the plains of real continents.
Geographical zoning
Geographical zoning
(physical-geographical zoning), a change in natural conditions from the poles to the equator, caused by latitudinal differences in the flow of solar radiation to the Earth’s surface. Max. energy is received by the surface perpendicular to the sun's rays (equatorial latitudes); the greater the tilt, the less heating (polar latitudes). Geographic zoning is one of the most universal geographical patterns, which has the status of a law. In accordance with this law, the landscape shell of the Earth is divided into natural zones, repeating in the North. and Yuzh. hemispheres (for example, zones of forests and steppes of the temperate zone, tropical deserts, etc.).
The idea of geographical zoning began to take shape in ancient times (Herodotus, Eudonis, Posidonius); The foundations of the doctrine of bioclimatic zonation were laid by A. Humboldt. In Russia, the greatest contribution to the doctrine of geographic zonation was made by V.V. Dokuchaev, L.S. Berg, A. A. Grigoriev, M.I. Budyko, I.P. Gerasimov, E. N. Lukasheva, A. G. Isachenko and others.
Law of geographical zoning: I R – radiation dryness index; the diameters of the circles are proportional to the biological productivity of landscapes
There are latitudinal, component (climate, soil, vegetation) zoning, sedimentogenesis zonality, exogenous geomorphological processes, hydrological (river flow characteristics zoning), hydrogeological and complex, or landscape. The basis for the differentiation of the geographical envelope into natural (landscape) zones is the ratio of heat and moisture. Latitudinal zoning is most clearly manifested on plains that extend enormously from north to south (Russian and West Siberian plains). Basic form of manifestation of zonality in the mountains - altitudinal zone. The features of latitudinal zonality are characteristic of the surface water masses of the ocean, which is manifested in the temperature of sea water, salinity, oxygen content, bioproductivity, and in the vertical and horizontal speed of movement.
Geography. Modern illustrated encyclopedia. - M.: Rosman. Edited by prof. A. P. Gorkina. 2006 .
See what “geographic zoning” is in other dictionaries:
The main pattern of differentiation of the geographical shell of the Earth, manifested in a consistent and definite change in geographical zones and zones, due mainly to the nature of the distribution of the solar radiant energy by latitude... ... Ecological dictionary
The main pattern of distribution of landscapes on the Earth's surface, consisting of a sequential change of natural zones, due to the nature of the distribution of radiant energy of the Sun across latitudes and uneven moisture. Geographical... ... Financial Dictionary
Differentiation of the earth's surface into zones according to climatic, biogeographical and other features due to the predominantly latitudinal distribution of solar heat. Ecological encyclopedic dictionary. Chisinau: Main editorial office of the Moldavian... ... Ecological dictionary
See geographical zoning. Geography. Modern illustrated encyclopedia. M.: Rosman. Edited by prof. A. P. Gorkina. 2006 ... Geographical encyclopedia
The pattern of differentiation of the geographical shell of the Earth; manifests itself in a consistent and definite change in geographical zones and zones, due mainly to the nature of the distribution of the solar radiant energy by latitude (decreases... Ecological dictionary
geographical zonation- Latitudinal differentiation of the geographical shell of the Earth, manifested in a consistent change of geographical zones, zones and subzones, caused by changes in the arrival of radiant energy from the Sun across latitudes and uneven moisture. → Fig. 367, p.... ... Dictionary of Geography
Geographic, the pattern of differentiation of the geographical (landscape) shell of the Earth, manifested in a consistent and definite change of geographical zones and zones (see Physico-geographical zones), caused primarily by ... Great Soviet Encyclopedia
geographical zonation- geografinė zona statusas T sritis ekologija ir aplinkotyra apibrėžtis Geografinės juostos žemyninė dalis, kurią lemia tam tikras šilumos ir drėgmės derinys. atitikmenys: engl. geographical zone vok. geografische Zonierung, f; globale Zonierung,… … Ekologijos terminų aiškinamasis žodynas
And since all the named elements, water, earth, fire(warmth and light) air, as well as the plant and animal worlds, thanks to the astronomical position, shape and rotation of our planet around her axis, bear in their general character the obvious, sharp and indelible features of the law global zonality, That Not only completely backward, but also completely inevitable, that in the geographical distribution of these eternal soil-formers, both in latitude and in longitude, constant, and, in essence, known to everyone, strictly natural, changes should be observed, especially sharply expressed with north to south, in the nature of countries polar, temperate, equatorial etc.
V. V. Dokuchaev
NATURAL ZONATION AND ITS LANDSCAPE MANIFESTATIONS
From the history of the issue
Natural zonation is one of the earliest patterns in science, ideas about which deepened and improved simultaneously with the development of geography. Zoning, the presence of natural belts, was found by Greek scientists of the 5th century on the Oikoumene, known by that time. BC e., in particular Herodotus (485-425 BC). Eudonyx of Cnidus (400-347 BC) distinguished five zones: tropical, two temperate and two polar. And a little later, the Roman philosopher and geographer Posidoius (135-51 BC) further developed the doctrine of natural zones that differ from one another in climate, vegetation, hydrography, and the characteristics of the composition and occupation of the population. “In Posidonius,” writes A.G. Isachenko (1971a, p. 64), “the doctrine of zones acquired, in a certain sense, an exaggerated form.” Indeed, the latitude of the area affects not only plants, animals, peoples, but also the “ripening” of precious stones. Therefore, it is difficult to agree with N.D. Dobrina (1975, p. 12) to refer to the initial period in the development of the doctrine of zonation (from ancient times to the middle of the 18th century) as simply “Identification of thermal zones based on astronomical data.” The statement of A. B. Ditmar and G. A. Chernova (1967, p. 132) is more correct: “The idea of latitudinal natural zoning, put forward and developed by ancient scientists, was a major achievement of ancient geography.”
The German naturalist A. Humboldt made a great contribution to the doctrine of natural zonation. There is a large literature about the scientist Humboldt. But, perhaps, A. A. Grigoriev (1929, p. 3) said about him better than others: “The main feature of his works was that he considered every phenomenon of nature (and often human life) as part of a single whole, connected with the rest of the environment by a chain of causal dependencies; no less important was the fact that he was the first to use the comparative method and, describing this or that phenomenon of the country he was studying, sought to trace what forms it took in other similar parts of the globe. These ideas, the most fruitful of all ever expressed by geographers, formed the basis of modern regional geography and, at the same time, led Humboldt himself to the establishment of climatic and plant zones, both horizontal (on the plains) and vertical (in the mountains), to identifying differences between the climatic conditions of the western and eastern parts of the first of them and many other very important conclusions.”
A. Humboldt's zones are bioclimatic in content. His views on zonality are most fully reflected in the book “Geography of Plants” [Humboldt A., 1936], thanks to which he is deservedly considered one of the founders of the science of the same name.
The zonal principle was used already in the early period of the physical-geographical zoning of Russia, dating back to the second half of the 18th - early 19th centuries. This refers to the geographical descriptions of Russia by A. F. Bishmnga, WITH. I. Pleshcheeva and E.F. ZyablovskO"Go [Milkov F.N., 1966]. The zones of these authors had a complex, natural-economic character, but due to limited knowledge they were extremely sketchy. Suffice it to say that the boundaries of three or four zones that stood out " them on the territory of Russia were carried out according to degrees of geographic latitude.
Modern ideas about geographic zoning are based on the works of V.V. Dokuchaev. The main provisions about zonality as a universal law of nature were formulated in a condensed form at the very end of the 19th century. Zoning, according to V.V. Dokuchaev, manifests itself in all components of nature, in the mountains and on the plains. It finds its specific expression in natural historical zones, in the study of which the focus should be on soils and soils - “a mirror, a bright and completely truthful reflection” [Dokuchaev "V.V., 1899, p. 6] of the interacting components of nature. Widely recognized the views of V.V. Dokuchaev; and the works of his numerous students - N.M. Sibirtsev, K.D. Glinka, A.N. Krasnov, G.I. Tanfilyev and others contributed greatly.
Further successes in the development of natural zoning are associated with the names of L. S. Berg and A. A. Grigoriev. After the major works of L. S. Berg (1947a, 1952), zones as landscape complexes became a generally recognized geographical reality; Not a single regional study can do without analyzing them; they entered the conceptual apparatus of sciences far removed from geography. In the 30s In some geographical departments, the physical geography course of the USSR was structured in the form of a detailed overview of natural zones identified and described by L. S. Berg *.
· As a student at the Faculty of Geography of the Moscow Regional Pedagogical Institute, I took such a zonal course in the physical geography of the USSR in 1936-III37. at Prof. I. M. Ivanova. Modern curricula for the physical geography course of the USSR "at universities and pedagogical institutes have moved away from zonality as the core problem of the entire curriculum. But in vain. The idea of zonality, used to analyze such a vast territory, turns the regional studies course into a genuine science.
A. A. Grigoriev is responsible for theoretical research on the causes and factors of geographic zoning. He briefly formulates the conclusions obtained “as follows: “Changes in the structure and development of the geographical environment (land) across belts, zones and subzones are based primarily on changes in the amount of heat as the most important energy factor, the amount of moisture, the ratio of the amount of heat and the amount of moisture” [ Grigoriev A. A., 1954, p. 18]. A lot of work was done by A. A. Grigoriev (1970) on the characterization of the nature of the main geographical belts of land. At the center of these largely original characteristics are the physical and geographical processes that determine the landscapes of the belts and zones. .
Certain aspects of the doctrine of natural zonality served as the subject of study in the works of A. D. Gozhev, P. S. Makeev, G. D. Richter, K. K. Markov, M. I. Budyko, A. M. Ryabchikov, E. N. Lukashova, D. V. Bogdanova.
Zone is a word of Greek origin; in Russian it means “a belt, strip, space between something.” two lines... In paleontology and geology - layer, layer" [Ushakov D.N., 1935, p. 1115]. Even the most general acquaintance with zonality in nature allows us to assert that it is the most important property, an expression of the orderliness of the structure of the landscape sphere of the Earth.
Specific manifestations of zonality are extremely diverse and are found both in physical-geographical and economic-geographical objects [Rodoman B.B., 1968]. Below we will talk only about natural (physical-geographical) zoning. It, in turn, falls into two classes - component zoning and landscape zoning.
The establishment of component zoning preceded landscape zoning. The concept of landscape zonation is based on the development of climatic, soil and plant zonation. Great achievements in the development of component zoning are well known. Here I would like to emphasize that landscape zoning does not repeat A uses critically at a new, complex level conclusions obtained by climatologists, soil scientists, geobotanists,
zoogeographers, hydrologists about component zoning. And the point is not only that zonal landscape divisions (zones, belts) do not always coincide territorially with similar divisions of industry sectors, but that their content is different.
Studying the contents of the paragraph provides the opportunity to:
Ø to form an idea of the geographical shell as a natural body;
Ø deepen knowledge about the essence of the periodic law of geographic zoning;
Ø deepen understanding of the peculiarities of the natural conditions of individual geographical zones of the Earth.
Features of the geographical shell. The geographical shell was formed simultaneously with the development of the Earth, therefore its history is part of the general history of the development of the Earth. ( What is the geographic envelope? What components of the geographic envelope have you already studied in your geography and biology course?)
All components of the geographical envelope are in contact, interpenetration and interaction . There is a continuous exchange of matter and energy between them. Life is concentrated in the geographical shell.
In its development, the geographic envelope went through three stages. The beginning of the first - inorganic - can be considered the appearance of the atmosphere. At the second stage, a biosphere was formed in the geographic shell, transforming all the processes that had previously taken place in it. At the third – modern – stage, human society appeared in the geographical shell. Man began to actively transform the geographical envelope.
Due to the fact that the geographical envelope of the Earth represents the environment for human life and activity, and the human impact on nature increases every year, its composition includes: sociosphere With technosphere And anthroposphere.
The sociosphere (from the Latin societas - society) is a part of the geographical envelope, including humanity with its inherent production and production relations, as well as the part of the natural environment developed by man.
Technosphere (from the Greek technе - art, skill) is a set of artificial objects within the geographical envelope of the Earth, created by man from the substance of the surrounding nature. The increasing anthropogenic pressure on the biosphere, which has caused the inclusion of elements of the technosphere and other means and products of human activity in the biosphere, contributes to the transition of the biosphere to a qualitatively new state.
The anthroposphere (from the Greek anthropos - man) embraces humanity as a collection of organisms. The life of any organism in all forms of its manifestation is possible only with constant interaction with the outside world and the continuous flow of energy into the body from the outside. All types of living beings ultimately use the same energy - the energy of the Sun, but the forms of manifestation and use of this energy are different.
Geographical zoning is expressed in the natural change of geographical zones from the equator to the poles and the distribution of geographical zones within these zones. The largest latitude-zonal unit of the geographic envelope is the geographic belt, which is distinguished by its characteristics radiation balance And general atmospheric circulation. Within the belt, the climate is relatively homogeneous, which is reflected in other components of nature (soils, vegetation, fauna, etc.) ( Remember what geographical zones are distinguished on Earth? What is their total number?).
The shape and area of the belts depend on many factors, the main of which are: the proximity of oceans and seas, relief, and sea currents. In geographical zones there are geographical (natural) zones. Their release is associated, first of all, with the uneven distribution of heat and moisture on the Earth's surface. ( Why?) They are often elongated in the latitudinal direction (Africa), but under the influence of the configuration of the continents and orographic factors they can have a meridional direction (North America).
V.V. Dokuchaev and L.S. Berg made a great contribution to the development of the doctrine of geographic zoning. V.V. Dokuchaev based his doctrine of natural zones on the proposition that each natural zone (tundra, taiga, steppe, desert and other zones) represents a natural complex in which the components of living and inanimate nature are interconnected and interdependent. This served as the basis for the classification of natural zones developed by L. S. Berg.
A further development of the law of geographical zonation was periodic law of geographical zonation, which was formulated in 1956 by famous geographers A.A. Grigoriev and M.I. Budyko. The essence of the periodic law is that geographical zones at different latitudes have a number of properties that are periodically repeated (for example, the zone of forest-steppe and savannas, deciduous forests of the temperate zone and forests of the humid subtropics, etc.) According to this law, the basis of differentiation of the geographical envelope lie: the amount of absorbed solar energy (the annual value of the radiation balance of the earth’s surface); amount of incoming moisture (annual precipitation); the ratio of the radiation balance to the amount of heat required to evaporate the annual amount of precipitation (radiation dryness index). The value of the dryness index in different zones ranges from 0 to 4-5. The periodicity is also manifested in the fact that the dryness index value, close to unity, is repeated three times between the pole and the equator (Fig....).
These conditions are characterized by the highest biological productivity of landscapes (with the exception of equatorial forests (hylea).
Thus, geographic zonality is expressed in the natural change of geographic zones from the equator to the poles and the distribution of geographic zones within these zones. The very list of names of geographical zones emphasizes their symmetrical position in relation to the equator. The share of the area of each geographical zone in relation to the total area of the globe is clearly shown in the figure (Fig...).
Along with zonality, azonality or regionality is distinguished. Azonality means the spread of any geographical phenomenon without connection with the zonal characteristics of a given territory. The main reasons for azonality are the geological structure, tectonic features, the nature of the relief, etc. In the presence of these factors, large areas of the geographical envelope acquire individual unique features, which complicates its structure and disrupts the zonation scheme. Azonality is most often and clearly manifested in the mountains and foothills.
Features of the Earth's geographic zones. Equatorial belt occupies 6% of the total land area of the Earth. It is represented by equatorial forests ( Using the map, determine the boundaries of the equatorial belt)
A feature of the equatorial belt is the extremely high intensity of all natural processes (geomorphological, biochemical and others), as a result of which a powerful weathering crust is formed. The reason for the high intensity of the processes is, first of all, the constantly hot and humid climate.
Subequatorial belts occupy about 11% of the total land area. ( Using a map, determine the location of the subequatorial belts). Most of the area of the subequatorial belts, like the equatorial belt, falls on the World Ocean. Here the belts are clearly expressed and can be identified by trade wind currents. The belts of both hemispheres in the Pacific and Atlantic oceans are shifted northward compared to their position on land.
An essential feature of the subequatorial belts is variable atmospheric circulation, when there is a seasonal change from equatorial air to tropical air, and vice versa, which determines the presence of dry and wet (rainy) seasons.
In the subequatorial belts, two natural zones are distinguished: savanna(savannas and woodlands), which is the main area, and the zone variable-humid forests- narrow, transitional from gils to savannas.
The eastern margins of the continents within these belts are under the influence of monsoons and trade winds.
Tropical zones. In total, they occupy 35% of the Earth's total land area. (Locate them on the map). In these latitudes, dry and hot air dominates both on the continents and on the oceans. According to natural features within tropical zones there are zones: forests, savannas And woodlands, semi-deserts and deserts (Using the atlas, determine the boundaries of the natural zones of the tropical zones).
Subtropical zones occupy an area equal to 15% of the total land area (Determine their location on the map and compare their distribution along longitude in the northern and southern hemispheres). The peculiarity of the nature of these belts is determined by their geographical location and is expressed in the predominance here tropical(summer) and moderate(in winter) air masses. In the western oceanic regions of these belts (see map) the nature is Mediterranean with dry summers and wet winters. The eastern coastal territories (see map) have a monsoon climate with high summer humidity. Inland areas have an arid climate. In general, natural zones are distinguished in subtropical zones: forests, forest-steppes, steppes, semi-deserts and deserts.
The natural conditions of the subtropical zones are favorable for human life, so these territories have long been developed and populated. Here the forests have been heavily cleared, and in their place are fields, plantations of cotton, tea, citrus fruits, etc.
Temperate zones characterized by the asymmetry of their location in the Northern and Southern Hemispheres (Use the map to determine the location of the belts in the northern and southern hemispheres). The large extent of the territory from east to west and from north to south causes a wide variety of natural conditions. According to natural features, the temperate zone is divided into moderately warm, dry, and moderately cold, damp. The first identifies natural zones: semi-deserts and deserts, steppes, forest-steppes; in the second: the zone of taiga (coniferous forests), broad-leaved forests, small-leaved and mixed forests. ( Using the atlas, determine the boundaries of the natural zones of the temperate zone of the northern hemisphere)
Subarctic belt located on the northern edges of Eurasia and North America. Its southern border is determined largely by the influence of sea currents. In Europe, under the influence of a warm current, the belt occupies a narrow strip of land and is located north of the Arctic Circle, while in the northeastern part of Eurasia, where there is no effect of this current, it expands and reaches 60° N. w. In North America (Hudson Bay region), under the influence of cold currents, its boundary drops to 50° N. sh., i.e. to the latitude of Kiev. The southern boundary of the belt approximately corresponds to the 10°C isotherm of the warmest month of the year. This is the limit of the northern distribution of forests. Permafrost is widespread, which in some places begins at a depth of 30 cm. Natural zones: tundra, forest-tundra and woodlands.
Subantarctic belt almost entirely located in oceanic spaces. Only a few islands represent land. The largest of them are Falkland, Kerguelen, South Georgia and others. The islands have oceanic tundra conditions, high humidity, strong winds, and poor moss-lichen vegetation. On some islands, tundra can be traced up to 50° S. w.
Arctic And Antarctic belts (Determine their geographical location) although they are located in territories with different underlying surfaces - the first is on the oceanic expanses, the second is on the continent of Antarctica, but they have more common features than different ones: low temperatures in winter and summer ( Determine the temperature of the warmest month), strong winds, lack or little vegetation, etc. The Arctic tundra zone, Arctic and Antarctic deserts are distinguished.
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