In the formation of the relief of Foreign Europe, exogenous factors played a significant role, along with endogenous ones. The nature and degree of their manifestation depended on the paleogeographic conditions of the development of the territory and its lithological structure.
Northern Europe is elevated and mountainous. It is composed of crystalline and metamorphic rocks of the Baltic Shield and Caledonides. Pleistocene glaciers and water erosion played a significant role in the creation of the relief. The largest uplifts of Fennoscandia are the Scandinavian Mountains - a gigantic elongated arch, steeply plunging towards the ocean and gently sloping to the east. Plain Fennoscandia occupies the east of the Baltic Shield - part of the Scandinavian Peninsula and Finland. Its relief is modeled by Pleistocene glaciers. The highest position is occupied by the Norland Plateau (600-800 m).
The formation of the island of Iceland is associated with the development of the underwater North Atlantic Ridge. Most of the island consists of basalt plateaus, above which rise dome-shaped volcanic peaks covered with glaciers (the highest point is Hvannadalshnukur, 2119 m). The area of modern volcanism.
The mountains of the northern part of the British Isles, tectonically and morphologically, can be considered a continuation of the Scandinavian mountains, although they are much lower (the highest point is Ben Nevis, 1343 m).
The Central European Plain is located in the zone of syneclises of Precambrian and Caledonian structures. The overlapping of the basement by a thick, undisturbed layer of Mesozoic and Cenozoic sediments is the main factor in the formation of the flat relief. A major role in the formation of the flat relief was played by exogenous processes of the Quaternary period, in particular, glaciers, which left accumulative forms - terminal moraine ridges and outwash. They are best preserved in the east of the lowlands, which were subject to the Rissian and Würm glaciations.
The relief of Hercynian Europe is characterized by the alternation of mid-altitude folded-block massifs and ridges (French Massif Central, Ardennes) with lowlands and basins (London, Paris basins).
Alpine Europe includes both high mountain systems and large lowland piedmont and intermountain plains. In terms of structure and relief, mountains belong to two types: young folded formations of Alpine age and folded-block formations, secondarily uplifted as a result of Alpine and neotectonic movements. Young folded mountains (Alps with the highest point in Europe - Mont Blanc, 4807 m, Carpathians, Stara Planina, Pyrenees, Apennines, Dinara). Folded-block and block mountains of Hercynian age (Rila, Rhodopes). The accumulative plains of Alpine Europe - the Middle Danube and Lower Danube - have a predominantly gently undulating topography. The relief of southern Europe, which includes three large peninsulas (Iberian, Apennine, Balkan), is diverse. For example, on the Iberian Peninsula there are alluvial lowlands (Andalusian), young alpine mountains (Pyrenees) and highlands (Old and New Castilian).
Foreign Europe
The geological structure of Europe is diverse. In the east, ancient platform structures, which are associated with plains, predominate, in the west - various geosynclinal formations and young platforms. In the west, the degree of vertical and horizontal division is much greater.
At the base of the East European Platform lie Precambrian rocks, which are exposed in the northwest in the form of the Baltic Shield. Its territory was not covered by the sea, having a constant tendency to rise.
Beyond the Baltic Shield, the foundation of the European Platform is submerged to a considerable depth and is covered by a complex of marine and continental rocks up to 10 km thick. In the areas of the most active subsidence of the plate, syneclises were formed, within which the Central European Plain and the Baltic Sea basin are located.
To the south and southwest of the European platform in the Archean era, the Mediterranean (Alpine-Himalayan) geosynclinal belt extended. To the west of the platform was the Atlantic geosyncline, bounded by the North Atlantic Land (Eria). Most of it subsequently sank into the waters of the Atlantic, with only small remnants surviving in the north of western Scotland and the Hebrides.
At the beginning of the Paleozoic, sedimentary rocks accumulated in geosynclinal basins. The BAIKAL FOLDING, which occurred at this time, formed small land masses in the north of Fennoscandia.
In the middle of the Paleozoic (end of the Silurian), the Atlantic geosyncline underwent strong mountain building (CALEDONIAN FOLDING). The Caledonian formations stretch from northeast to southwest, covering the Scandinavian mountains and the northern parts of Great Britain and Ireland. The Caledonides of Scandinavia sink into the waters of the Barents Sea and reappear in the western part of Spitsbergen.
Caledonian tectonic movements also manifested themselves partially in the Mediterranean geosyncline, forming there a number of isolated massifs, which were later included in younger folded formations.
In the Upper Paleozoic (mid and late Carboniferous), the entire Central and large parts of Southern Europe were captured by the HERCYNAN OROGENESIS. Powerful folded ridges formed in the southern part of Great Britain and Ireland, as well as in the central part of Europe (Armorican and Central French Massifs, Vosges, Black Forest, Rhine Slate Mountains, Harz, Thuringian Forest, Bohemian Massif). The extreme eastern link of the Hercynian structures is the Lesser Poland Upland. In addition, Hercynian structures can be traced on the Iberian Peninsula (Meseta massif), in certain areas of the Apennine and Balkan peninsulas.
In the Mesozoic, south of the Hercynian formations of Central Europe, a vast Mediterranean geosynclinal basin extended, captured by mountain-building processes in the ALPINE OROGENESIS (Cretaceous and Tertiary periods).
Folding and block uplifts, which led to the formation of modern alpine structures, reached their maximum development in the Neogene. At this time, the Alps, Carpathians, Stara Planina, Pyrenees, Andalusian, Apennine mountains, Dinara, Pindus were formed. The direction of the Alpine folds depended on the position of the middle massifs of Hercynian age. The most significant of them were in the western Mediterranean the Iberian and Tyrrhenian, in the eastern - the Pannonian massif, which lies at the base of the Middle Danube Plain and caused the double bend of the Carpathians. The southern bend of the Carpathians and the shape of the Stara Planina arc were influenced by the ancient Pontida massif, located on the site of the Black Sea and the Lower Danube Plain. The Aegean massif was located in the central part of the Balkan Peninsula and the Aegean Sea.
In the Neogene, alpine structures undergo vertical movements of the earth's crust. These processes are associated with the subsidence of some middle massifs and the formation in their place of depressions, now occupied by sections of the Tyrrhenian, Adriatic, Aegean, Black Seas or low accumulative plains (Middle Danube, Upper Thracian, Padanian). Other central massifs experienced significant uplifts, which led to the formation of such mountainous territories as the Thracian-Macedonian (Rhodope) massif, the mountains of Corsica, Sardinia and the Calabrian peninsula, the Catalan Mountains. Fault tectonics caused volcanic processes, which, as a rule, are associated with deep faults in the contact zones of the middle massifs and young folded ridges (the coasts of the Tyrrhenian and Aegean seas, the internal arc of the Carpathians).
Alpine movements covered not only Southern Europe, but also manifested themselves in Central and Northern Europe. In the Tertiary period, the North Atlantic landmass (Eria) gradually split and sank. Fractures and subsidence of the earth's crust were accompanied by volcanic activity, which caused the outpouring of enormous lava flows; as a result, the island of Iceland and the Faroe archipelago were formed, and some areas of Ireland and Scotland were blocked. Powerful compensation uplifts captured the Caledonides of Scandinavia and the British Isles.
Alpine folding revived tectonic movements in the Hercynian zone of Europe. Many massifs were raised and broken by cracks. At this time, the Rhine and Rhone grabens were founded. The activation of faults is associated with the development of volcanic processes in the Rhine Slate Mountains, the Auvergne massif, the Ore Mountains, etc.
Neotectonic movements that swept across Western Europe affected not only the structure and topography, but also led to climate changes. The Pleistocene was marked by glaciation, which repeatedly covered vast areas of plains and mountains. The main center of continental ice distribution was located in Scandinavia; the centers of glaciation were also the mountains of Scotland, the Alps, the Carpathians, and the Pyrenees. The glaciation of the Alps was fourfold, the continental glaciation was threefold.
FOREIGN EUROPE EXPERIENCED THREE GLACIES IN THE PLEISTOCENE: MINDEL, RISK AND WURMS.
The activity of cover and mountain glaciers of the Middle Pleistocene (Ries) and Upper Pleistocene (Würm) glaciations had the greatest geomorphological significance. During the Rissky (maximum) glaciation, a continuous cover of glaciers reached the mouth of the Rhine, the Hercynids of Central Europe, and the northern foothills of the Carpathians. The Würm glaciation was much smaller in size than the Ris glaciation. It occupied only the eastern part of the Jutland Peninsula, the northeast of the Central European Plain and all of Finland.
Pleistocene glaciations had a diverse impact on nature. The centers of glaciation were predominantly areas of glacial drift. In the marginal areas, the glacier has formed accumulative and fluvio-glacial structures; the activity of mountain glaciers manifested itself in the creation of mountain-glacial relief forms. Under the influence of glaciers, a restructuring of the hydrographic network took place. Over vast areas, glaciers destroyed flora and fauna and created new soil-forming rocks. Outside the glaciation period, the number of heat-loving species decreased.
The geological structures of Foreign Europe correspond to certain mineral complexes.
Inexhaustible resources of building stone are concentrated on the territory of the Baltic Shield and the Scandinavian Mountains; Iron ore deposits are located in the contact zones of the Scandinavian mountains. Oil and gas fields are relatively small and, as a rule, are confined to Paleozoic and Mesozoic sediments (Germany, the Netherlands, Great Britain, adjacent areas of the North Sea), as well as to Neogene sediments of piedmont and intermountain troughs of the Alpine folding (Poland, Romania).
The Hercynides zone is home to a variety of mineral resources. These are coals from the Upper Silesian, Ruhr, Saar-Lorraine basins, as well as from the basins of central Belgium, central England, Wales, Decazville (France), and Asturias (Spain). Large reserves of iron oolitic ores are located in Lorraine and Luxembourg. There are deposits of non-ferrous metals in the mid-altitude mountains of Czechoslovakia, East Germany, Spain (Asturias, Sierra Morena), and bauxite deposits in Hungary, Yugoslavia, and Bulgaria. The Permian-Triassic deposits of the mid-altitude Hercynian Mountains zone include deposits of potassium salts (western Germany, Poland, France).
The complexity of the geological structure of Foreign Europe led to the diversity of its relief, in the formation of which exogenous factors played a significant role, along with endogenous ones. The nature and degree of their manifestation largely depended on the paleogeographic conditions of the development of the territory and its lithological structure.
NORTHERN EUROPE is elevated and mountainous. It is composed of crystalline and metamorphic rocks of the Baltic Shield and Caledonides. Tectonic movements determined the fragmentation of its surface. Pleistocene glaciers and water erosion played a significant role in the creation of the relief.
The largest uplifts of FENNOSCANDIA are the Scandinavian Mountains - a gigantic elongated arch, steeply plunging towards the ocean and gently sloping to the east. The peaks of the mountains are smoothed, most often these are high plateaus (fjelds), above which individual peaks rise (the highest point is the city of Galhepiggen, 2469 m). In sharp contrast to the fjelds are the mountain slopes, in the formation of which faults played a major role. The western slopes are especially steep, dissected by systems of deep fjords and river valleys.
PLAIN FENNOSCANDIA occupies the east of the Baltic Shield - part of the Scandinavian Peninsula and Finland. Its relief is modeled by Pleistocene glaciers. The highest position is occupied by the Norland Plateau (600-800 m), while most of the plains lie at an altitude of less than 200 m. Low ridges and ridges correspond to tectonic shafts and arches in the relief (Manselka, Småland). On the plains of Fennoscandia, glacial landforms are classically represented (eskers, drumlins, moraines).
The formation of the island of ICELAND is associated with the development of the underwater North Atlantic Ridge. Most of the island consists of basalt plateaus, above which rise dome-shaped volcanic peaks covered with glaciers (the highest point is Hvannadalshnukur, 2119 m). Region of modern volcanism.
The mountains of the northern part of the BRITISH ISLANDS, tectonically and morphologically, can be considered a continuation of the Scandinavian mountains, although they are much lower (the highest point is Ben Nevis, 1343 m). Dissected by tectonic valleys that continue into bays, the mountains are replete with glacial landforms, as well as ancient volcanic nappes that created the lava plateaus of Northern Ireland and Scotland.
The south-east of Great Britain and the south-west of Ireland are classified as Hercynides.
The CENTRAL EUROPEAN PLAIN is located in a zone of syneclises of Precambrian and Caledonian structures. The overlapping of the basement by a thick, undisturbed layer of Mesozoic and Cenozoic sediments is the main factor in the formation of the flat relief. A major role in the formation of the flat relief was played by exogenous processes of the Quaternary period, in particular, glaciers, which left accumulative forms - terminal moraine ridges and outwash. They are best preserved in the east of the lowlands, which were subject to the Rissian and Würm glaciations.
The relief of Hercynian EUROPE is characterized by the alternation of mid-altitude folded-block massifs and ridges with lowlands and basins. The mosaic nature of the relief is determined by block and arch post-Hercynian movements, accompanied in some places by lava outpourings. Mountains created by arch movements belong to the massif type (Massif Central). Some of them (Vosges, Black Forest) are complicated by grabens. The horst mountains (Harz, Sudetes) have rather steep slopes, but relatively low heights.
The flat areas within Hercynian Europe are confined to syneclises of the folded foundation, made by a thick Mesozoic-Cenozoic strata (Paris, London, Thuringian, Swabian-Franconian basins) - stratified plains. They are characterized by a cuesta topography.
ALPINE EUROPE includes both high mountain systems and large lowland foothill and intermountain plains. In terms of structure and relief, mountains belong to two types: young folded formations of Alpine age and folded-block formations, secondarily uplifted as a result of Alpine and neotectonic movements.
YOUNG FOLDED MOUNTAINS (Alps, Carpathians, Stara Planina, Pyrenees, Apennines, Dinara) are distinguished by lithological heterogeneity, alternating crystalline, limestone, flysch and molasse belts. The degree of development of the belts is not the same everywhere, which determines a unique combination of relief forms in each mountainous country. Thus, in the Alps and Pyrenees, Paleozoic crystalline massifs are clearly represented, in the Carpathians there is a well-defined strip of flysch deposits, and in the Dinaric Mountains - limestone ones.
FOLDED-BLOCK AND BLOCK MOUNTAINS (Rila, Rhodopes) are plateau-type massifs. Their significant modern height is associated with neotectonic movements. River valleys (Vardar, Struma) are confined to the lines of tectonic faults.
ACCUMULATIVE PLAINS of Alpine Europe - the Middle Danube, Lower Danube and others correspond to foothill troughs or are laid on the site of subsided middle massifs of the Alpine geosyncline. They have a predominantly gently undulating topography, only occasionally complicated by small uplifts, which are protrusions of the folded foundation.
The relief of SOUTH EUROPE, which includes three large peninsulas (Iberian, Apennine, Balkan), is very diverse. For example, in the Iberian Peninsula there are ALLUVIAL LOWS (Andalusian), YOUNG ALPINE MOUNTAINS (Pyrenees) and HIGHLANDS. The relief and geological structure of the Balkan Peninsula are varied. Here, along with young folded formations, ancient Hercynian massifs are found.
Thus, the relief of Foreign Europe is to a large extent a reflection of its structural structure.
Related information.
On the hypsometric map of Russia and on photographs from space, the orographic pattern of the entire territory of our country is clearly visible. It is characterized by a complex combination of low and elevated plains, plateaus, highlands and mountains.
On the vast plains, vast areas are occupied by lowlands with heights of less than 200 m, among which hills and individual island ridges are scattered here and there. Higher up are the plains of the SS; they are more like plateaus strongly indented by valleys, especially at the edges. They form a kind of step in the transition from the lowlands of the west of the country to the highlands of its east. Most plains have a stable foundation and a quiet geological regime for a long time. But in the distant past, the plains either sank or rose, and more than once served as the bottom of the sea, and their very flatness often owes to the strata deposited in ancient seas.
The mountainous regions of the country, in contrast to the plains, are not so calm: the earth’s crust here and now is mobile, subject to compression, distortion, fragmentation, and especially intense uplift and subsidence; it is the scene of ongoing modern mountain building.
The map shows that the mountainous outskirts of our country are divided into three heterogeneous stripes - southern, eastern and diagonal. The southern one is a link in the Alpine-Himalayan belt of geologically young mountain structures (Caucasus). The eastern strip is a link in the even younger East Asian mountain belt, and with it, part of a grandiose ring of mountain systems, which embraces the Pacific Ocean on almost all sides (Sikhote-Alin, Kuril-Kamchatka ridge, Sakhalin). A third band of mountains cuts diagonally across the eastern half of the country from the Chukotka and Kolyma highlands to southern Siberia.
The southern and eastern stripes are zones of not only the newest vertical uplifts, but also the most recent folding. In contrast, the structures of the third stripe are built by folds of various, including ancient ages. However, the latest uplift here also took place a long time ago, as well as in zones of young folding.
But not all links of folded margins rose at the last stage of geological history. Some, on the contrary, sank and in some places found themselves flooded by the Pacific, Caspian, and Black seas. Therefore, the stripes of raised folds do not form continuous barriers, but alternate with depressions, depressions, and here and there, in coastal areas, form islands.
A mountain fringe could have existed in the north of the country, but the land here over a large area sank under the waters of the Arctic seas, and the mountain systems turned into isolated archipelagos. This is how Franz Josef Land and Severnaya Zemlya arose. It emerged in the form of two islands of Novaya Zemlya and the northern continuation of the Ural mountain rampart.
This is, in the most general terms, the picture of the horizontal division of the land surface of our country. But dismemberment in plan is also characteristic of coasts, where there are peninsulas and islands, bays and straits.
The largest bays represent entire seas: the Baltic, the White, the Black and Azov, the Okhotsk, each of them has its own dead-end arches.
The Far Eastern seas - the Bering Sea and the Sea of Japan - in contrast to the “sea-bays” are “sea-straits”. Each of the marginal seas of the Arctic Ocean is also a kind of bay-strait: they are delimited by archipelagos of islands, interrupted by straits.
The bottom of the seas has its own relief, in which one can distinguish both plains and mountain systems (for example, a strip of mountains with the mountain ranges of Mendeleev, Lomonosov and Otto Schmidt in the Central Arctic), and the deepest depressions, including the Kuril-Kamchatka, the third deepest in the world , reaches 10540 m below sea level. The relatively shallow bottom of the Arctic seas rises above the depths of the central parts of the Arctic Ocean like a balcony, forming a continental shoal or shelf.
Plains are concentrated mainly in the western half of Russia, and plateaus, highlands and mountains predominate in the east - from the Yenisei valley to the shores of the Pacific Ocean. Plains make up about 60% of the territory. The two largest of them - BE and ZS - are among the greatest plains in the world. Medium-altitude mountain systems stretch as a continuous barrier parallel to the coasts of the Pacific Ocean. In the south, along the border, there is a belt of high mountains, from which the entire territory descends towards the Arctic Ocean. The largest rivers of Siberia - the Ob, Yenisei, and Lena - flow north along this slope. And powerful currents of cold air pass south from the Arctic across the plains.
The southern belt of mountains is included in the belt of high elevations of Eurasia and consists of separate mountain systems of different ages: the Caucasus, Altai, Sayan, Baikal region and Transbaikalia. The Caucasus and Altai are considered among the highest mountains of Eurasia.
Climate is a long-term weather regime that has developed as a result of the interaction of the atmosphere with all natural geographic factors and is subject to the influence of space and human economic activity.
The climate of Russia is formed under the influence of a number of climate-forming factors and processes. The main climate-forming processes are radiation and circulation, which are determined by the conditions of the territory.
Radiation– incoming solar radiation is the energy base; it determines the main heat flow to the surface. The farther you are from the equator, the lower the angle of incidence of the sun's rays, the smaller the amount received. The expenditure part consists of reflected radiation (from albedo) and effective radiation (increases with decreasing cloudiness, the total - from north to south).
In general, the radiation balance in the country is positive. The only exceptions are some Arctic islands. In winter it is negative everywhere, in summer it is positive.
Circulating. Due to the different physical properties of land and ocean, the air in contact with them is unequally heated and cooled. As a result, movements of air masses of various origins occur - atmospheric circulation. It occurs under the influence of centers of low and high pressure, their position and severity changes seasonally. However, in most of our country, westerly winds prevail, bringing Atlantic air masses, which are associated with the main precipitation.
The influence is especially great in winter, due to the westerly transfer of warm and humid air masses from the Atlantic.
The large size of the territory of our country, the presence of vast valleys and large mountain systems have determined a clear zonal provincial distribution of soils, vegetation and animals. The main conditions for the formation of biocomponents are the ratio of temperature and moisture. Their distribution is significantly influenced by the topography of the territory and the degree of continental climate.
The unity of the biocomplex is determined by the zonal structure of atmospheric processes, the interaction of all components of nature and the long history of the development of the territory in the Phanerozoic.
The distribution of soils, vegetation and animals on the territory of Russia is determined by the law of zonation on the plains and altitudinal zonation in the mountains. Therefore, when moving along meridians or along mountain slopes due to changes in hydro-climatic conditions, there is a gradual replacement of some types of soil and vegetation, as well as animal complexes, by others.
But at the same time, the increasing continentality of the climate to the east (to certain limits) and the different geological history of large geostructures (platforms and folded belts) led to the differentiation of soils, vegetation and fauna, i.e. to the manifestation of provincialism (sectoralism).
The orographic features of the territory are predetermined by the complex geological history and varied geological structure. Large lowlands, plains and plateaus correspond to platforms, and mountain structures correspond to folded belts.
The territory of Russia is located on several lithospheric plates: the northern part of the Eurasian, the western part of the North American, the northern part of the Amur. And only the Sea of Okhotsk plate is almost entirely located on the territory of the country.
The earth's crust within Russia, as elsewhere on Earth, is heterogeneous and of different ages. It is heterogeneous both horizontally and vertically.
Rigid, stable sections of the earth's crust - platforms - differ from more mobile ones - folded belts, which are more susceptible to both compression and vertical swings. Platforms are typically characterized by a two-tier structure, where a crushed crushed base and a cover of horizontal layers covering it are distinguished.
The oldest platforms are considered to be Precambrian. Their foundation is composed not only of the oldest rocks, which are more than 570-600 million years old, but was also folded into folds before the strata of subsequent eras appeared. This is the structure of our two extensive platforms, which are among the most extensive in the world.
In those parts where the oldest structures of the Earth were not flooded by the seas, or where marine sediments were washed away in subsequent eras, ancient foundations come to the surface - the so-called shields. There are also underground foundation outlets that approach the surface closely (Voronezh crystalline massif). Don reached its arch only in one place.
Stable platforms increased in size over time - sections of neighboring folded zones were soldered to them, acquiring rigidity during the process of crushing. At the end of the Precambrian era, i.e. 500-600 million years ago, the Baikal folding sharply increased the Precambrian core of the future Siberian platform: huge folded massifs of the Baikal region and parts of Transbaikalia were attached to the Aldan shield.
During the Paleozoic era, powerful folding shook the earth's crust twice. The first, called the Caledonian folding, occurred in several stages in the early Paleozoic 300-400 million years before the present day. His monuments remain in the folds in the center of the Sayan Mountains. The second, called the Hercynian folding, occurred in the late Paleozoic (200-250 million years ago) and turned a huge trough of the earth’s crust between the Russian and Siberian platforms into the Ural-Tien Shan folded zone. As a result of this folding, the Russian and Siberian platforms united into an integral continent - the basis of the future Eurasia.
In the wide belt adjacent to the Pacific Ocean, the main stage of crushing of the earth's crust was the Mesozoic era - 60-190. its structures, called Pacific, built up the Siberian platform from the east, forming powerful folded areas in Primorye, Amur region, Transbaikalia and in the northeast of Siberia.
Only two vast strips, where the restless regime was preserved, did not lose their pliability to the dislocations after the Mesozoic movements. One stretched through the Alps and the Caucasus to the Himalayas. The second strip, bordering the east of Asia and including the western margins of the Pacific Ocean, is the East Asian folded region. Both areas continued to exist not only in the Mesozoic, but also later. It was in the Cenozoic, i.e. in the last 60 million years, they turned out to be the scene of powerful crumples. Here the last of the foldings unfolded - the Alpine folding, during which the subsoil of the Caucasus, Sakhalin, Kamchatka and the Koryat Highlands were crushed. These active areas continue to exist today, manifesting their activity through numerous earthquakes and, in East Asian mountain-island arcs, volcanism.
In the second half of the Alpine era of folding - in the Neogene, 10-20 ml. years ago, a completely new stage in the history of the earth’s crust began, which had special significance for the modern relief. It is associated with recent, or neotectonic movements, mainly vertical uplifts and subsidences, which covered not only the Alpine mobile zones, but also structures significantly removed from them of very different ages.
The youngest folded zones were subjected to very intense impact: the Caucasus, Sakhalin and the Kuril-Kamchatka arc. All these mountainous countries now exist not so much as a result of recent folding, but as a result of the recency and intensity of these new vertical uplifts. In the general diagonal belt of mountains, the uplift involved structures of different ages, such as Precambrian (southern Aldan Shield, Baikalids of the Stanovoy Range and Highlands), Paleozoic (Hercynides of Altai, Urals), Mesozoic (northeast Asia). The latest movements were expressed not only in uplifts, but also in descents. Depressions in the earth's crust created the modern appearance of sea depressions and large lakes, many lowlands and basins (Baikal). The foothill depressions adjacent to the young mountains were subjected to especially strong subsidence.
The stability of platforms in relation to crushing does not mean immobility in general. Both platforms and folded areas are subject to another type of movement - alternating vertical oscillations (swelling and subsidence).
The relationship between relief and the structure of the earth's crust is approximately as follows: the higher the surface area, the greater the thickness of the crust. The largest is where the mountain formations are (40-45 km), the smallest is the basin of the Sea of Okhotsk. Isostatic equilibrium. At the contact of the Eurasian and North American plates, plates move apart (Moma Rift) and a zone of diffuse seismicity forms. The latter is also characteristic of the margin of the Sea of Okhotsk plate. At the contact of the Eurasian and Amur there is also a movement - the Baikal Rift. The Okhotsk Sea at the contact with the Amur Sea (Sakhalin and the Sea of Japan) plate convergence is 0.3-0.8 cm per year. The Eurasian Sea borders on the Pacific, North American, African (Arabian) and Indian (Indostano-Pamir). The lithospheric compression belts between them are the Alpine-Asian in the south and the Circum-Pacific in the east. The margins of the Eurasian plate are active in the east and south and passive in the north. In the east, the oceanic subducts under the continental: the junction zone consists of marginal seas, island arcs and a deep-sea trench. In the south there are mountain ranges. The passive margins in the north are a huge shelf and a clearly defined continental slope.
Eurasia is characterized by linear and ring structures, established from satellite images, geological, geophysical and geological studies. seismic cores of the continental crust. Nuclears, 14.
The heat flow of the Earth on the territory of Russia has different values: the lowest values are on ancient platforms and the Urals. Increased - on all young platforms (slabs). Maximum values – fold belts, Baikal rift, marginal seas of the TO.
With depth, the temperature in the Earth gradually increases. Under the oceanic plates, the temperature of the mantle reaches the melting point of mantle rocks. Therefore, the surface of the beginning of melting of mantle material is taken as the base of the lithosphere under the oceans. Below the oceanic lithosphere, the mantle material appears to be partially molten and plastic with reduced viscosity. The plastic layer of the mantle stands out as an independent shell - the asthenosphere. The latter is clearly expressed only under oceanic plates; under thick continental plates it is practically absent (basaltic magmatism). In the context of continental plates, it can only appear in the case when hot mantle material, due to the splitting of the plate, can rise to the level at which this substance begins to melt (80-100 km).
The asthenosphere does not have a tensile strength and its substance can deform (flow) under the influence of even very small excess pressures, although very slowly due to the high viscosity of the asthenospheric substance (about 10 18 - 10 20). For comparison, the viscosity of water is 10 -2, liquid basaltic lava is 10 4 - 10 6, ice is about 10 13 and rock salt is about 10 18.
Movements of lithospheric plates along the surface of the asthenosphere occur under the influence of convective currents in the mantle. Individual lithospheric plates can diverge, move closer together, or slide relative to each other. In the first case, tension zones with rift cracks along the boundaries of the plates appear between the plates, in the second - compression zones, accompanied by the thrust of one of the plates onto the other, in the third - shear zones, transform faults, along which the neighboring plates are displaced.
As the main categories of tectonic areas, we will distinguish: 1. relatively stable areas - ancient platforms, mainly possessing a pre-Proterozoic metamorphic basement, 2. mobile mobile Neogean belts, consisting of folded areas of different ages (in place of dead geosynclinal areas) and modern geosynclinal areas, 3. areas, transitional - metaplatforms.
Ancient platforms, or cratons, represent vast areas of ancient continental crust, measuring millions of square kilometers, largely formed in the Archean and almost entirely by the end of the Early Proterozoic. Neogean is a relatively calm tectonic regime: “sluggishness” of vertical movements, their weak differentiation in area, relatively low rates of uplift and subsidence (less than 1 cm/thousand years). At the early megastage of development, most of their area experienced uplift, and subsidence mainly involved narrow linearly elongated graben-like depressions - aulacogens. At the later, slab megastage (Phanerozoic), a significant area of platforms was drawn into the subsidence, on which a cover of almost undisplaced sediments was formed - a slab. Simultaneously with the subsidence of the foundation, areas of platforms became isolated within the plates, which throughout most of their history had a tendency to rise and represented extensive protrusions of the ancient foundation - shields.
The cover of ancient platforms usually does not bear traces of metamorphic changes, which, like the absence or limited development of manifestations of magmatism, is explained by a significant decrease in the thermal regime during the formation of ancient platforms and, as a rule, low heat flow over most of their territory (except for aulacogens). However, in some zones of the ancient platforms, manifestations of magmatism took place, and in certain rare phases, due to the anomalous heating of the upper mantle beneath them, the ancient platforms could become the scene of powerful trap magmatism in effusive and intrusive forms.
Movable belts. They were founded mainly in the ancient Proterozoic. Their development goes through 2 megastages: geosynclinal (the greatest tectonic mobility, expressed in differentiated horizontal and vertical movements and a high, albeit unstable thermal regime in the crust and upper mantle) and postgeosynclinal (in place of dead geosynclinal belts, activity is reduced, but much more, than on ancient platforms).
The total duration of the goesynclinal process is 1-1.5 billion years, but in some areas it ends earlier. “Cycles”, the geosynclinal stage itself and the shorter orogenic stage (orogenesis) are distinguished.
Actually geosynclinal: stretching of the crust, the appearance of elongated graben-like depressions. Wide deflections break up into narrow ones. At the end there is the gesyncle itself. stages stop descending. At the beginning of the orogenic stage, they undergo strong compressive deformations (from the internal zones to the periphery). They turn into folded structures. During the orogenic stage, they experience gradually increasing uplift, not fully compensated by denudation, and at the late orogenic stage they turn into mountain structures. Thus, a complete reversal of the tectonic plan occurs (geosynclinal troughs into mountain uplifts). At the same time, in the zones of growing folded structures, marginal troughs appear, as if compensating for their uplift, and in the rear - internal troughs or depressions filled with fragmentary material.
The “cycles” into which the process of development of geosynclinal belts breaks down end with a relative strengthening of the crust, which acquires over a significant (or entire) area the features of a typical (mature) continental-type crust. At the beginning of the next “cycle”, partial destruction of this crust and regeneration of the geosynclinal regime occurs, while other areas are excluded from the further geosynclinal process.
In most of the North Atlantic mobile belt, the geosynclinal process ended in the middle of the Paleozoic, in the Ural-Mongolian belt - in the late Paleozoic - early Mesozoic, in most of the Mediterranean belt it is close to completion, and significant parts of the Pacific belt are still at different stages of the geosynclinal process.
Metaplatform areas. Something average in the nature of tectonic structures, the degree of crustal mobility and the characteristics of tectonic movements. On the borders. Structurally, it is a combination of two main types of tectonic elements - mobile aulakogeosynclinal zones and relatively “hard” metaplatform massifs, separated by these zones from ancient platforms. Avlacogeosynclinal zones represent linearly elongated zones of an intermediate nature between the aulacogens of ancient platforms and geosynclinal troughs of mobile belts. In the Late Proterozoic, simultaneously with the mobile belts framing the platforms, usually branching off from the latter. Graben-like troughs – compression – metamorphism, intrusion of intrusive bodies – folded zones (Donetsk, Timan).
The role of climate in human life is difficult to overestimate. It determines the ratio of heat and moisture, and, consequently, the conditions for the occurrence of modern relief-forming processes, the formation of internal waters, the development of vegetation, and the placement of plants. Climate features have to be taken into account in human economic life.
Influence of geographical location.
| Latitudinal position | Determines the amount of solar radiation arriving at the surface, as well as its intra-annual distribution. Russia is located between 77 and 41°, but its main area is between 50 and 70°. This determines Russia’s position in high latitudes, in the temperate and subarctic zones, which predetermines sharp changes in the amount of incoming solar radiation according to the seasons of the year. The large extent from north to south determines significant differences between the north and south of the territory. The annual total solar radiation is 60 kcal/cm2, in the extreme south – 120 kcal/cm2. |
| The country's position in relation to the oceans | Directly affects the distribution of cloudiness, and therefore the ratio of diffuse and direct radiation, and the supply of moist air. Russia is washed by seas from the north and east, which is not significant given the prevailing western transport and only affects the coastal strip. In the Far East, a sharp increase in cloudiness reduces the influx of direct solar radiation, amounting to the same value as in the north of the Kola Peninsula, Yamal, and Taimyr. |
| Position of the country in relation to pressure centers (CPC) | Azores and Arctic highs, Aleutian and Icelandic lows. Determine the prevailing wind direction, weather type, and prevailing air masses. |
| Relief | The location of mountains in the south and east and openness to the Arctic Ocean provide the influence of the North Atlantic and Arctic Ocean on most of the territory of Russia, limiting the influence of Ton and Central Asia. - The height of the mountains and their location in relation to the prevailing air currents determine different degrees of influence - Aggravation of cyclones - Mountain climate that changes with altitude - Differences in the climate of windward and leeward slopes, mountain ranges and intermountain basins - On the plains the differences are much weaker |
| Features of the underlying surface | Snow increases the reflectivity of the surface, black soils and forests decrease it. Differences in albedo are one of the reasons for differences in the radiation balance of territories receiving the same total radiation. Moisture evaporation and plant transpiration also vary from place to place. |
Air masses and their frequency. Russia is characterized by three types of air masses: arctic air, temperate air and tropical air.
In most parts of the country, air masses predominate throughout the year moderate latitudes, represented by two sharply different subtypes: continental and maritime. Continental The air is formed directly over the mainland and is dry throughout the year, with low temperatures in winter and fairly high temperatures in summer. Nautical air comes from the North Atlantic, and to the eastern regions - from the northern part of To. Compared to continental air, it is more humid, cooler in summer and warmer in winter. Moving across the territory of Russia, the sea air quickly transforms, acquiring continental features.
Arctic the air is formed above the ice of the Arctic, so it is cold, has low absolute humidity and high transparency. Impact on the northern part of the country, especially SS and NE. During transition seasons it causes frosts. In summer, moving forward and becoming increasingly dry, it brings droughts and hot winds (south EE and WS). The air formed over the Arctic can be designated continental. Only over the Barents Sea does the Arctic sea form.
Tropical air over the southern territories is formed over Central Asia, Kazakhstan, the Caspian lowland, and the eastern regions of the Ciscaucasia and Transcaucasia as a result of the transformation of air in temperate latitudes. Characterized by high temperatures, low humidity and low transparency. Tropical sea air from the central regions sometimes penetrates to the south of the Far East, and to the Caucasus from the Mediterranean. Characterized by high humidity and high temperatures.
Atmospheric fronts.
Physico-geographical conditions of the territory. The underlying surface over which they form and acquire new properties has a great influence. Thus, in winter, moist air masses bring latent heat of vaporization to a cold surface and warming occurs. In summer, moist air masses also bring precipitation, but on the warm underlying surface, evaporation and slight cooling begin.
The influence of relief on climate is great: with altitude, the temperature drops by 0.6°C for every 100 meters (due to a decrease in the radiation balance), and atmospheric pressure decreases. The influence of exposure is felt. Mountains play an important barrier role.
Special role – sea currents. Warm North Atlantic, cold around the Kuril Islands, Kamchatka, Sea of Okhotsk.
Climatic features of the winter period. During the cold season in Russia, from October to April, an area of high pressure (Asian maximum) is established, an area of low pressure develops off the eastern coast (Aleutian minimum) and the Icelandic minimum intensifies, reaching the Kara Sea. Between these main pressure centers of the winter period, the differences in pressure reach the greatest values and this contributes to the aggravation of circulation processes.
In connection with the western transport, the development of cyclones and anticyclones, circulation processes are very pronounced and they largely determine the distribution of heat and moisture. The influence of the Atlantic, Asian High, Aleutian Low and solar radiation is clearly visible.
In winter, air masses from the Atlantic Ocean bring a large amount of heat to the mainland. Therefore, in the EE and northern half of the WS, the temperature decreases not so much from south to north, but from west to east and northeast, which is confirmed by the course of January isotherms.
The impact of the Asian High is reflected in the extremely low temperatures of Central Siberia, the Northeast and the position of the isotherms. In the basins the temperature reaches -70 (the cold pole of the northern hemisphere - Oymyakon and Verkhoyansk).
In the Far East, the Aleutian minimum and the Okhotsk branch of the Arctic front predetermine cyclonic activity, which is reflected in warmer and snowier winters than on the continent, so January isotherms run parallel to the coast.
The greatest amount of winter precipitation falls in the west, where air flows from the Atlantic in cyclones. From west to east and northeast, the amount of precipitation gradually decreases.
Climatic features of the summer period. The ratio of radiation and circulation conditions changes dramatically. The temperature regime is determined by radiation conditions - all land heats up significantly more than the surrounding water areas. Therefore, already from April to October the isotherms extend almost sublatitudinally. In July, throughout Russia, average monthly temperatures are positive.
In summer, the Azores maximum moves north and its eastern branch penetrates the EE plain. From there, the pressure decreases to the north, south and east. The Arctic maximum remains above the Arctic Ocean. Therefore, cold air moves into the interior, warmer territories of Russia, where it heats up and moves away from its saturation point. This dry air contributes to the occurrence of droughts, sometimes with hot winds in the southeast of the EE plain, in the south of the WS plain and in the north of Kazakhstan. The development of dry, clear and warm weather is also associated with the spur of the Azores High. Over TO, the North Pacific High moves north (the Aleutian Low disappears), and sea air rushes toward land. The Far Eastern summer monsoon begins.
In summer, there is also a western transfer - from the Atlantic - of the greatest amount of precipitation.
All air masses entering the country in summer are transformed into continental air of temperate latitudes. On atmospheric fronts (Arctic and polar), cyclonic activity develops. It is most pronounced on the polar front over the EE plain (continental and maritime temperate).
The Arctic front is expressed within the Barents and Kara seas and on the coast of the eastern seas of the Arctic Ocean. Along the Arctic front, cyclonic activity intensifies and causes prolonged drizzle in the subarctic and arctic zones. In summer, maximum precipitation occurs, which is associated with increased cyclonic activity, moisture content of air masses and convection.
Changes in radiation and circulation conditions occur in spring and autumn. In the spring, the negative radiation balance turns into a positive one, and in the fall, vice versa. In addition, the position of areas of high and low pressure, the type of air masses, and, consequently, the position of atmospheric fronts change.
South America has the highest height and contrast of relief. On its territory there are the gigantic high mountain system of the Andes and the vast low-lying plains of the Amazon, Laplat, etc. The lowest continent is Australia (average height 210 meters). has a very high altitude (more than 2000 meters) due to the ice cover, the subglacial surface is raised by an average of 410 meters. Africa as a whole is a fairly high continent (average height 650 meters), but the hypsometric level of its surface is not distinguished by contrast: the relief is dominated by hills, plateaus and plateaus. There are no large mountain systems or extensive lowlands on the mainland.
There are some similar features in the structure of the surface, which are associated, first of all, with the stages of their common geological history. Plains, plateaus and plateaus occupy the main areas of the territory of all the Southern continents, and large mountainous countries are located on the outskirts - in the west of South America and Antarctica, in the east of Australia, in the north and south of Africa. A significant part of the territory of all four Southern continents represents fragments of ancient Gondwana. After the split of Gondwana and the divergence of the continents, it turned out that Africa, which previously occupied the center of the supercontinent, is almost entirely a platform structure, bounded on the east and west by fault lines. Only in the extreme north and south, where the continent once reached the outskirts of Gondwana, are there currently folded structures of the Hercynian and Alpine orogenies. Fold belts are adjacent to the Gondwanan platform structures of South America and Antarctica from the west, and Australia from the east.
The relief of platform blocks of the earth's crust was created by neotectonic movements of an epeirogenic and fault nature. The orographic structure of these parts of the continents is predetermined by ancient tectonic processes. They are dominated by direct relief: in large syneclises there are lowland plains: the Amazonian, Orinoco, Laplata lowlands in South America, the northeast of the Sahara in Africa, the Great Artesian Basin in Australia, the Bentley Basin in Antarctica, and on the shields, in most cases, elevated plains have formed , plateaus and block mountains.
Sometimes the bottoms of basins formed in syneclises are at a fairly high hypsometric level: the basins of North Africa have absolute bottom heights from 250 meters to 400 meters, Congo - from 350 meters to 500 meters, Kalahari - from 950 meters to 1000 meters. But they are still lower than the surrounding plateaus and mountains. The destruction products of the surrounding uplifts accumulated in the basins over a long period of time.
On the Southern continents there are also areas of inverted relief: high plateaus within the Paraná, Karoo, Kimberley, and Canning syneclises. High plains also formed in the areas of foothills and marginal platform troughs along the Andes, Atlas, Cape and East Australian mountain systems.
Main types of endogenous relief (morphostructures)
Morphostructures of ancient platforms
The basis of the relief within the platform structures of the Southern continents are the basement plains and plateaus of the shields of the Precambrian platforms and the stratal and accumulative plains of plates of different hypsometric levels.
Basement plains and plateaus, created by denudation processes within the ancient folded structures of shields, occupy vast areas on all four continents. They are found in the Guiana and Brazilian Highlands, Western Australia and East Antarctica. This type of relief is especially characteristic of High Africa and areas where crystalline rocks emerge on the Leon-Liberian and Regibat shields. Accumulative plains have a limited distribution, located mainly along the margins of continents or in the central and axial parts of intraplatform syneclises. Stratified lowlands, hills and plateaus are much more widespread on platform slabs.
The relief of blocky revived epiplatform mountains, widespread on the Southern continents, was created by differentiated fault movements along faults within platform shields, and in some places, plates. Such mountains are common in the Guiana, Brazilian, East African highlands, marginal escarpments of South Africa, Western Australia and East Antarctica.
Large areas on the Southern continents are occupied by the morphostructures of lava plateaus on effusive covers, since the breakup of Gondwana and differentiated movements along faults throughout the history of the formation of the surface of the Southern continents were accompanied by volcanic processes. These plateaus, usually of a stepped nature, occupy vast areas within the Paraná syneclise, on the Ethiopian Highlands, and there are smaller sections in almost all areas that have experienced differentiated movements in different eras. The ancient Gondwanan platforms also contain volcanic massifs and mountain ranges. In the rift zones of Africa and Antarctica, active and extinct ones are common. Landforms associated with volcanism are characteristic of the Ahaggar and Tibesti highlands, the border of the Red Sea, and the East African Highlands. Large ones are known: Nyira Gonga, individual craters of the Meru and Kilimanjaro massifs, Cameroon, etc. There are even more extinct volcanoes and volcanic formations: cones, shields, calderas, sometimes filled. There are large active volcanoes in Antarctica, for example Erebus. There is no modern volcanism in Australia, but there are areas of volcanic plateaus on the platform plains of the western part of the continent, for example in the east of the Kimberley Plateau.
Morphological structures of moving belts
The relief of the mobile belts adjacent to the Gondwanan platforms is complex, but with all its diversity, some common features and patterns of arrangement of morphostructures can be traced here. In all mountain systems of folded belts of the Southern continents, young tectonic zones of the Alpine and Pacific orogenies border the continents on the ocean side.
Even the Epipaleozoic East Australian belt has such a “young” border in the form of island arcs accompanying the Pacific coast of Australia. In the Andes, the Coastal Cordillera also extends from the Pacific Ocean, in which, apparently, folding processes are still ongoing - the result of the incomplete subduction of oceanic plates. The coastal zone of western South America, like the island arcs along eastern Australia, is accompanied by deep-sea trenches. Low anticlinal or volcanic mountain chains have a very large elevation above the bottom of the trenches. In some places, for example in the Central Andes region, the total amplitude of relief heights is greater than the height of the Himalayas. In these mountain ranges, processes of modern volcanism are developed, there are post-volcanic phenomena, and the degree of seismicity is high.
The volcanoes and geysers of New Zealand are well known, as are the earthquakes, often catastrophic, in the intermittent Coastal Cordillera of Chile and Peru, which are folded into folds of Cenozoic rocks or volcanic material.
The next orotectonic zone of the Andes when moving into the Andean system is the rejuvenated and revived block-folded and folded-block high and medium-altitude ridges of the Western Cordillera.
They stretch continuously from the very north of the Andean system from the Gulf of Darien to the Strait of Magellan in the south. From 28° S. w. this chain of ridges is called Main, and from 42° south. w. - Patagonian Cordillera. Folding took place here during the Alpine orogeny. Neotectonic movements raised the Alpine anticlinoria along faults to great heights (4000-6000 meters). In the Main Cordillera there is the highest point of the Andes - the city of Aconcagua (6960 meters). In this orotectonic zone, manifestations of Meso-Cenozoic volcanism are widespread in the form of granitoid intrusions, lava covers, extinct and active volcanoes of the Western Cordillera of the Central Andes, the Main and Patagonian Cordillera. Some of the volcanoes have a height exceeding 6000 meters, many are still active today.
To the east (from the Guajira Peninsula in the north to 38° S) stretch the ridges of the Eastern Cordillera. These are revived folded block and block mountains, mainly on the Hercynian base.
The ridges reach great heights - 4000-5000 meters, some peaks are over 6000 meters. In the north (about 3° N latitude), the mountains branch, forming the Central and Eastern Cordillera of Colombia and Venezuela. Even further east, where at the junction of the mobile belt and ancient platform structures, the edges of the platform were sometimes involved in active tectonic movements, between 20° and 37° S. w. systems of revived block mountains rise on a Precambrian and Paleozoic folded foundation. These are the Pampino (Pampian) Sierras and Precordillera. Relatively narrow blocky ridges are separated by valleys.
The orotectonic belts of the Andes are separated by depression zones. Between the Coastal and Western Cordilleras there is a strip of subsidence.
Within its boundaries is located, for example, the Atacama depression, to the south is the Longitudinal (Central) Valley of Chile, to which a whole chain of volcanoes along fault lines is confined.
Between the Western and Eastern Cordilleras north of 10° S. w. Narrow graben-shaped longitudinal depressions stretch, occupied by river valleys, the bottoms of which lie at a considerable height.
There are numerous volcanoes along the fault lines, including active ones - Cotopaxi, Sangay, etc.
The Western and Eastern Cordillera in the Central Andes are framed by high-mountain plains - the Punas, which formed within the middle massif, partially covered by lava sheets.
The ancient block is located at a lower hypsometric level than the surrounding mountains (3000-4000 meters). Material from the mountains is carried into this depression, and here weakly undulating accumulative plains and lava plateaus with individual remnant massifs and volcanoes are formed. The basins previously contained numerous lakes, which are now partially dry.
The Northern Andes are separated by a tectonic fault from the so-called Caribbean Andes. These are structures that complete the Caribbean-Antilles mobile zone from the south, which is believed to have formed in the western part of the Tethys Ocean. The zone is seismic, but there is no modern volcanism here.
The Andes in the far south are connected through the island system of South Georgia, South Sandwich and South Orkney to the mountain ranges of West Antarctica. The folded-block mountains of the Antarctic Peninsula, the western coast of the continent and the so-called Antarctic Andes (Antarkands) continue the tectonic zones of the Andean mobile belt (height - 3000-4000 meters, the highest point of the continent is located on Ellsworth Land - the Vinson Massif, 5140 meters). This folded Meso-Cenozoic belt is separated from the Precambrian and Paleozoic structures of East Antarctica by a system of faults running from the Weddell Sea to the Ross Sea. Along them rise the horst ranges of the Transantarctic block mountains. Manifestations of volcanism on the mainland and islands are associated with faults.
The East Australian mountain system, bordering the Gondwanan platforms from the east, is much simpler in orographic structure and lower in absolute altitude than the Andean. It stretches for 4000 km along the east coast of Australia and is separated from the island arcs by marginal seas. Folded-block mountains, low and medium-altitude, predominate here: as a rule, their height is 1000-1500 meters (the highest point of Kosciuszko is 2230 meters).
This mountainous country was created by differentiated neotectonic movements on the site of the post-Hercynian peneplain. The movements were accompanied by lava outpourings, but there is no modern volcanism here. The mountains of Eastern Australia are also characterized by low seismic activity, which indicates their relative tectonic stability at the present time. The ranges have steep eastern slopes, and gently undulating foothills descend to the inland plains, which in Australia are called downs.
The African Platform is also adjacent to the north from the mobile belt, within which the Atlas mountain system was formed. The same pattern is evident here: on the outer side of the continent along the Mediterranean coast there are ridges of young folded mountains - Er Rif and Tel Atlas. Most of the Atlas system consists of restored fold-block mountains and intermountain plateaus on the Hercynian base. A high degree of tectonic activity remains in the northern ranges, and earthquakes occur frequently.
The mountains of the system are low - on average 2000-2500 meters. They reach their greatest height in the High Atlas (Tubkal, 4165 meters - the highest point of the system). The young alpine ranges Er Rif and Tel Atlas barely reach 2500 meters.
The Cape mountain system, which occupies the extreme south of Africa, is a revived mountain range with an inherited folded structure.
Folding movements took place here during the era of the Hercynian orogeny, when Gondwanaland was a single continent and the southern tip of the African continent was part of a mobile belt on its margin. The folding processes ended here in the Triassic period, and immediately after this the intensive subsidence of the territory began. Mountain structures, not yet smoothed out by denudation, were covered by a cover of marine sediments of Mesozoic age. Neotectonic uplifts, which covered the whole of South Africa in Paleogene-Neogene times, led to the fact that the Hercynian anticlinal ridges appeared on the surface. The loose sedimentary rocks that overlaid the folded structures were removed. The rise was accompanied by increased deep erosion. As a result, the Cape Mountains consist of several parallel anticlinal ridges up to 1500 meters high, separated by longitudinal synclinal valleys. They are crossed by narrow, deep river canyons, sometimes associated with tectonic cracks.
Features of exogenous relief (morphosculpture)
Of the exogenous factors shaping the surface of the Southern continents, the leading role belongs to weathering processes (hypergenesis), the work of surface and groundwater, in Africa and Australia - the work of wind, in Antarctica and some areas of the Andes - glaciers.
The role of weathering processes
The activity of all exogenous factors on most of the Southern Tropical continents occurs under conditions of high temperatures. Rocks of various genesis and composition undergo hypergenesis: crystalline, volcanogenic, sedimentary. Their upper layer over large areas represents weathering crusts, which were formed over a long time (starting from the Mesozoic) under changing conditions.
This is a zone of hypergenesis of both ancient rocks of the Precambrian basement and Proterozoic syneclises, as well as younger sedimentary and effusive deposits. Thick, usually loose weathering crusts have different structures and compositions depending on the conditions of their formation and the lithology of the original rocks. Over vast areas, they were formed under conditions of increased moisture, if not year-round, then seasonal, and are a product of biochemical processing (mainly ferralitization) of surface rocks. These crusts consist of fine particles of clay minerals and hydroxides of iron, aluminum and manganese. Depending on the formation conditions, dense ferruginous or ferruginous-alumina laterite layers are formed at different depths. The thickness of such crusts can be from several to hundreds of meters. This depends on the duration of formation, and on the composition and structure of the original rocks, and on modern processes of both their formation and destruction.
In the arid regions of the Southern Tropical continents, there are areas of relict hydromorphic crusts - a legacy of pluvial eras. They are especially widespread on the plains and block mountains of Australia and North Africa. Ferrous lateritic crusts, being destroyed under the influence of physical weathering, turn into placers of red rubble, pebbles, and sand.
Physical weathering processes, widely developed in areas of arid climate due to large temperature differences, destroy rocks. Sharp ridges and peaks, bizarrely shaped rocks with niches, arches, and protrusions are formed. The products of destruction - large fragmentary material - fill the lower parts of the slopes and the surrounding plains. These are rocky deserts - hamads (hamads). They are mostly confined to tectonic uplifts, volcanic massifs, intrusive remnants, etc. and are widespread in all arid zones of the plains and mountains of the Southern continents.
On the surface of solid rocks, processes of desquamation (peeling) develop, and the so-called “desert tan” is formed - rocky ledges are covered with dark films. These processes operate not only in the hot arid regions of the Southern Tropical continents, but also in Antarctica, in its oases and mountainous areas, rising in places above the ice surface.
Fluvial relief
The river network of constantly humid areas with equatorial, tropical and subtropical climates is characterized by shallow erosional incision of channels. On flat stratal and accumulative plains, water erodes weathering crusts, carries a mass of fine earth, and deposits thin silty material. Rivers constantly flood, change channels, wander along wide valley bottoms, branch into branches separated by low islands, and form meanders.
Alluvial plains are systems of floodplains, usually of several levels, and wide above-floodplain terraces - the main type of fluvial morphosculpture within tectonic depressions: Amazonian, Orinoco, Laplata, Pantanal - in South America, basins of the Congo, Okavango, White Nile, middle Niger - in Africa, Murray Basin - in Australia. It is not for nothing that most of these plains are named after the rivers that drain them.
Shallowly incised are the beds of high-water African rivers flowing from mountains and plateaus and crossing the elevated outskirts of the continent, such as, for example, the upper and lower reaches of the river. Congo (Zaire) or the lower reaches of the Zambezi, Orange, Kunene, etc. rivers.
These have a stepped longitudinal fall profile with rapids and waterfalls slowly receding upstream. This cannot be explained only by the youth of the valleys, since some of them, for example the upper reaches of the river. Congo, developed under more or less stable tectonic conditions at least from the Mesozoic. According to the figurative expression of the French geographer Birot, rivers “jump over” uneven terrain, rather than cutting through them. This is apparently due to the fact that river waters carry mainly fine earth. Large clastic material is quickly subjected to decomposition by biochemical processes under conditions of high temperatures and high humidity, so the transported sediment does not have a strong eroding ability, especially since the bottoms of valleys are often composed of hard crystalline rocks. Channels are often armored with ferruginous crusts and films. In areas of the variable humid climate of equatorial-tropical latitudes, laterite shells lie at shallow depths or even directly on the surface. When destroyed, they turn into hard pebbles, which have significant eroding capabilities. But at the same time, lateritic crusts armor the bottom of the channels, making incision difficult. As a result, in both constantly and variablely humid tropics under more or less stable tectonic conditions, the erosional incision is shallow and the relief has soft outlines.
In the deserts of Northern and Southern Africa and Australia, relict erosional landforms have been preserved - the beds of former rivers and streams (wadis or wadis of Africa, similar to Arabian ones, and cries of Australia).
These usually shallow and gently sloping depressions stretch for tens and hundreds of kilometers and end, as a rule, in the basins of dry lakes. During periods of rare rainfall, streams of water flow through them. This prevents the complete disappearance of the channels, which deepen again after each such period. During rains, the former lake basins are briefly filled, turning again into lakes, usually salty ones. Such depressions in the northeast of the Sahara and within the Atlas are called shottas or sebkhas.
Solifluction and landslide relief
With constant or seasonal waterlogging, slope runoff develops. Soaking loose soil literally flows between the roots and stems of plants and moves down slopes, even gentle ones. Solifluction forms appear. The process of landslide formation is widespread. The development of slope processes increases sharply if the vegetation cover disappears, which usually occurs as a result of human economic activity. Cutting down and burning of forests and bushes, excessive grazing of livestock and other impacts on the vegetation cover that holds the soil together and impedes the flow and removal of material down the slopes lead to the rapid development of solifluction and landslide processes. These processes are facilitated by the presence of dense water-resistant layers - laterite shells, and in some places monolithic crystalline rocks lying close to the surface.
On more or less flat and gently sloping areas of the surface, suffusion also develops in loose weathering crusts, forming depressions.
The activity of surface and groundwater generally leads to the formation of a slightly undulating, gently sloping topography with remnant mountains, ridges, and areas of table plateaus. Such planation surfaces were produced during periods of stable tectonic regime throughout geological history.
Ascending neotectonic movements raised them to different heights, during the process of uplift they were subjected to intense dissection, but still, in the relief of the Southern continents, fragments of peneplains and pediplains of various geological ages play a rather large role. The remains of several planation surfaces can be traced on all continents.
Remnant table plateaus 1000-1500 meters high, and in some places 2000-3000 meters high, are fragments of a dissected “Gondwanan” surface, which was created by denudation in the Jurassic period. They are found within the highlands of Africa and South America. Later surfaces are widespread, created by the denudation cycles of the Late Cretaceous - Oligocene, Neogene and, finally, the Pleistocene cycle, which continues to the present day. As a result, on the Southern continents there are often tabletop hills and plateaus, flat-topped mountains and slightly undulating plains, complicated by remnant massifs or low ridges on outcrops of denser bedrock, on intrusive massifs. Peneplain plains with outcrops are very characteristic of Western and Central Australia. Mesa forms are often associated with the presence of armor strata, such as hard sandstones and quartzites: Brazilian chappadas, Guiana highlands tepuyas, South African mesas.
Aeolian relief
Forms of aeolian accumulation: various types of dunes, sand ridges are common in those areas of arid regions that are composed of sand on the surface (usually ancient river or marine alluvium). Barchan topography is characteristic of the coastal deserts of western South America and South Africa. The vast sandy expanses of Australian deserts are mainly ridges, elongated in the direction of the prevailing winds. In African sandy deserts (in the ergs of the Sahara, in the Namib) one can find almost all types of aeolian accumulative relief. In the Sahara there are individual dunes reaching hundreds of meters in height.
In the arid regions of the Southern continents, forms associated with deflation (blowing) and corrosion are also widespread. Rocky outcroppings turn into rock mushrooms, often found in the Brazilian Highlands and in the arid mountainous regions of all the Southern continents. On the dry plateaus of South Africa there are areas where granite rocks are transformed by the combined work of weathering and wind into giant balls and pyramids of almost geometrically regular shape.
Karst terrain
Unlike the Northern continents, it has a limited distribution on the Southern continents. Its formation requires a combination of karst rock outcrops with sufficient precipitation. There are few such areas within the Southern continents.
Karst is most widespread in Australia, where limestone strata emerge on the surface on the Barkly Plateau within a subequatorial climate zone with summer rainfall, in the East Australian Mountains, where rainfall occurs all year round, on the Nullarbor Plain, in a subtropical climate with winter rainfall. In the basin of the Darling and Murray rivers, limestones lie under a layer of alluvial sediments, and covered karst is developed.
Karst forms of different areas vary depending on local conditions. In the north and northeast of Australia, mainly tropical tower karst with conical limestone outcrops forms. On the plains and plateaus of the subtropical zone, a wide variety of forms of bare and covered karst are common. There are numerous caves, grottoes and niches in the mountains and on abrasion ledges. At the foot of the limestone ledge that opens the Nullarbor Plain to the Great Australian Bight, the sea seems to be boiling with the release of underwater karst springs. The coastal cliff has a scalloped shape, as sea water intensively dissolves rock along cracks perpendicular to the shore line. Narrow bays protruding deeply into the land are formed, which separate the rounded protrusions of the coastal ledge.
In Africa and South America, karst forms are found in small areas in the Andes, in the Brazilian Highlands (there are caves there), in East and Southern Africa. Significant areas of karst landforms are occupied in the Atlas mountain system, on the Somali peninsula and in the northern Sahara (for example, in the Tassilli cuesta ridges bordering the Ahagarr highlands). In these arid regions, the formation of karst is associated with the pluvial epochs of the Pleistocene (such relief has a relict character). In the karst caves of Tasilli and other ridges, wall paintings of primitive people who inhabited the Sahara when it was not yet a waterless desert were found.
Coastal relief
The types of coasts of the Southern continents are very diverse. Among them there are both initially flat, and dissected, and those created by abrasion and accumulative activity of the sea, non-wave and wave processes. Coasts formed by fault movements are very widespread, since most of the margins are passive margins of continents. They are usually bordered by narrow strips of accumulative lowlands at the foot of high steep cliffs, usually abraded. Lagoon shores are widely developed, often accompanied by mangroves. The mangrove type of coastline is typical for low coastal areas in the equatorial-tropical regions of the Southern continents.
The eastern edge of Australia is interesting, where the coastline is accompanied by numerous coral structures.
There is a unique formation here - the Great Barrier Reef.
This is an intermittent ridge of coral reefs and islands, stretching along the northeastern coast of the mainland for 2,300 km and separated from the coast by a wide lagoon. Despite the rather large distance from the mainland coast in some places, the reef has a significant impact on the nature and economy of the coast. The Great Barrier Reef breaks the oceans, it rearranges the currents approaching the mainland, creating special conditions for the life of organisms in the calm and warm waters of the lagoon. The destruction of reef structures, occurring under the influence of both natural and anthropogenic processes, can have significant consequences for natural systems and the population of the Australian coast. Coral reefs accompany the northern coast of Australia and South America and are practically absent along the steep coastline of the passive margins of the African continent.
Glacial terrain
Glacial, including relict, landforms, so characteristic of Eurasia and North America, are very limited in distribution on the Southern Tropical continents. Glacial relief, both exaration and accumulative, is found on the plains of the Patagonian Plateau, in the mountains of Eastern Australia (mountain relict forms) and in the Andes. The Andean highlands and almost the entire region of the Southern Andes, where there is a whole complex of forms associated with mountain glaciation, including troughs, glacial lake basins and fjord coasts, were subject to glacial processing in the past and are currently undergoing.
Glaciation is the leading exogenous factor in the formation of the relief of Antarctica. For almost the entire territory of the continent we have to talk about the subglacial relief of the rock bed of a giant ice sheet. Only 0.2-0.3% of the continent's area is free of ice. Mountains protruding above the ice surface, small areas of the so-called Antarctic oases not covered with ice, and rocky cliffs occupying 8% of the length of the sea coast are also affected by other external relief-forming processes. But here, too, mountain-glacial exaration and accumulative relief forms predominate, and in oases, water-glacial relief forms also predominate.
Glacial landforms in the mountains of the continent are apparently of ancient age and have been preserved from times when the climate was warmer, since at the very low temperatures prevailing in Antarctica, ridge and valley glaciers lose their mobility. The processes of physical weathering are in the nature of desquamation of rocks, giving their surface a cellular structure. Some chemical reactions also occur, as a result of which red-brown crusts are formed - “desert tan”, or white discolorations of gypsum and calcite. Wind plays a significant role in the sculptural treatment of surfaces. Products of physical weathering are carried by the wind. Due to the high force of the wind flow, debris rolling over the surface can be up to 10-20 cm in diameter. They have considerable corroding capabilities: the hard material grinds and grinds rocky surfaces. Processes of aeolian accumulation also take place in oases: sand dunes and ridges have been found there along with fluvioglacial relief - mainly depressions for the runoff of melted glacial waters.
Of interest is the relief of the snow-ice surface of the ice sheet with numerous and varied irregularities: snowy hills, sastrugi, glacial cracks, winding “valleys” of streams flowing along the ice plain during periods of melting, etc. This very mobile, rapidly changing relief is formed under the influence of a large number of interacting factors: the movement of ice over an uneven rock bed, the processes of thawing and freezing, the work of wind, melt water and many others.
The coast of Antarctica for thousands of kilometers is a high ice barrier, which has no analogues anywhere on Earth. Icebergs are constantly breaking off from it. Rocky shores (about 8% of the coastline) are usually high, steep cliffs, in the niches of which lie glaciers and snowfields.
Thus, fluvial relief is most characteristic of South America, mainly fluvial and aeolian morphosculpture is developed in Africa, in Australia, in most of the territory, the leading role is played by aeolian processes, in Antarctica, the main surface forms are created by the work of glaciers and wind. At the same time, the fluvial and aeolian relief of the Southern Tropical continents has many common features. This is due to the fact that they have similar climatic conditions: climates of equatorial-tropical latitudes predominate.
On the hypsometric map of Russia and on photographs from space, the orographic pattern of the entire territory of our country is clearly visible. It is characterized by a complex combination of low and elevated plains, plateaus, highlands and mountains.
On the vast plains, vast areas are occupied by lowlands with heights of less than 200 m, among which hills and individual island ridges are scattered here and there. Higher up are the plains of the SS; they are more like plateaus strongly indented by valleys, especially at the edges. They form a kind of step in the transition from the lowlands of the west of the country to the highlands of its east. Most plains have a stable foundation and a quiet geological regime for a long time. But in the distant past, the plains either sank or rose, and more than once served as the bottom of the sea, and their very flatness often owes to the strata deposited in ancient seas.
The mountainous regions of the country, in contrast to the plains, are not so calm: the earth’s crust here and now is mobile, subject to compression, distortion, fragmentation, and especially intense uplift and subsidence; it is the scene of ongoing modern mountain building.
The map shows that the mountainous outskirts of our country are divided into three heterogeneous stripes - southern, eastern and diagonal. The southern one is a link in the Alpine-Himalayan belt of geologically young mountain structures (Caucasus). The eastern strip is a link in the even younger East Asian mountain belt, and with it, part of a grandiose ring of mountain systems, which embraces the Pacific Ocean on almost all sides (Sikhote-Alin, Kuril-Kamchatka ridge, Sakhalin). A third band of mountains cuts diagonally across the eastern half of the country from the Chukotka and Kolyma highlands to southern Siberia.
The southern and eastern stripes are zones of not only the newest vertical uplifts, but also the most recent folding. In contrast, the structures of the third stripe are built by folds of various, including ancient ages. However, the latest uplift here also took place a long time ago, as well as in zones of young folding.
But not all links of folded margins rose at the last stage of geological history. Some, on the contrary, sank and in some places found themselves flooded by the Pacific, Caspian, and Black seas. Therefore, the stripes of raised folds do not form continuous barriers, but alternate with depressions, depressions, and here and there, in coastal areas, form islands.
A mountain fringe could have existed in the north of the country, but the land here over a large area sank under the waters of the Arctic seas, and the mountain systems turned into isolated archipelagos. This is how Franz Josef Land and Severnaya Zemlya arose. It emerged in the form of two islands of Novaya Zemlya and the northern continuation of the Ural mountain rampart.
This is, in the most general terms, the picture of the horizontal division of the land surface of our country. But dismemberment in plan is also characteristic of coasts, where there are peninsulas and islands, bays and straits.
The largest bays represent entire seas: the Baltic, the White, the Black and Azov, the Okhotsk, each of them has its own dead-end arches.
The Far Eastern seas - the Bering Sea and the Sea of Japan - in contrast to the “sea-bays” are “sea-straits”. Each of the marginal seas of the Arctic Ocean is also a kind of bay-strait: they are delimited by archipelagos of islands, interrupted by straits.
The bottom of the seas has its own relief, in which one can distinguish both plains and mountain systems (for example, a strip of mountains with the mountain ranges of Mendeleev, Lomonosov and Otto Schmidt in the Central Arctic), and the deepest depressions, including the Kuril-Kamchatka, the third deepest in the world , reaches 10540 m below sea level. The relatively shallow bottom of the Arctic seas rises above the depths of the central parts of the Arctic Ocean like a balcony, forming a continental shoal or shelf.
Plains are concentrated mainly in the western half of Russia, and plateaus, highlands and mountains predominate in the east - from the Yenisei valley to the shores of the Pacific Ocean. Plains make up about 60% of the territory. The two largest of them - BE and ZS - are among the greatest plains in the world. Medium-altitude mountain systems stretch as a continuous barrier parallel to the coasts of the Pacific Ocean. In the south, along the border, there is a belt of high mountains, from which the entire territory descends towards the Arctic Ocean. The largest rivers of Siberia - the Ob, Yenisei, and Lena - flow north along this slope. And powerful currents of cold air pass south from the Arctic across the plains.
The southern belt of mountains is included in the belt of high elevations of Eurasia and consists of separate mountain systems of different ages: the Caucasus, Altai, Sayan, Baikal region and Transbaikalia. The Caucasus and Altai are considered among the highest mountains of Eurasia.
Climate is a long-term weather regime that has developed as a result of the interaction of the atmosphere with all natural geographic factors and is subject to the influence of space and human economic activity.
The climate of Russia is formed under the influence of a number of climate-forming factors and processes. The main climate-forming processes are radiation and circulation, which are determined by the conditions of the territory.
Radiation– incoming solar radiation is the energy base; it determines the main heat flow to the surface. The farther you are from the equator, the lower the angle of incidence of the sun's rays, the smaller the amount received. The expenditure part consists of reflected radiation (from albedo) and effective radiation (increases with decreasing cloudiness, the total - from north to south).
In general, the radiation balance in the country is positive. The only exceptions are some Arctic islands. In winter it is negative everywhere, in summer it is positive.
Circulating. Due to the different physical properties of land and ocean, the air in contact with them is unequally heated and cooled. As a result, movements of air masses of various origins occur - atmospheric circulation. It occurs under the influence of centers of low and high pressure, their position and severity changes seasonally. However, in most of our country, westerly winds prevail, bringing Atlantic air masses, which are associated with the main precipitation.
The influence is especially great in winter, due to the westerly transfer of warm and humid air masses from the Atlantic.
The large size of the territory of our country, the presence of vast valleys and large mountain systems have determined a clear zonal provincial distribution of soils, vegetation and animals. The main conditions for the formation of biocomponents are the ratio of temperature and moisture. Their distribution is significantly influenced by the topography of the territory and the degree of continental climate.
The unity of the biocomplex is determined by the zonal structure of atmospheric processes, the interaction of all components of nature and the long history of the development of the territory in the Phanerozoic.
The distribution of soils, vegetation and animals on the territory of Russia is determined by the law of zonation on the plains and altitudinal zonation in the mountains. Therefore, when moving along meridians or along mountain slopes due to changes in hydro-climatic conditions, there is a gradual replacement of some types of soil and vegetation, as well as animal complexes, by others.
But at the same time, the increasing continentality of the climate to the east (to certain limits) and the different geological history of large geostructures (platforms and folded belts) led to the differentiation of soils, vegetation and fauna, i.e. to the manifestation of provincialism (sectoralism).
The orographic features of the territory are predetermined by the complex geological history and varied geological structure. Large lowlands, plains and plateaus correspond to platforms, and mountain structures correspond to folded belts.
The territory of Russia is located on several lithospheric plates: the northern part of the Eurasian, the western part of the North American, the northern part of the Amur. And only the Sea of Okhotsk plate is almost entirely located on the territory of the country.
The earth's crust within Russia, as elsewhere on Earth, is heterogeneous and of different ages. It is heterogeneous both horizontally and vertically.
Rigid, stable sections of the earth's crust - platforms - differ from more mobile ones - folded belts, which are more susceptible to both compression and vertical swings. Platforms are typically characterized by a two-tier structure, where a crushed crushed base and a cover of horizontal layers covering it are distinguished.
The oldest platforms are considered to be Precambrian. Their foundation is composed not only of the oldest rocks, which are more than 570-600 million years old, but was also folded into folds before the strata of subsequent eras appeared. This is the structure of our two extensive platforms, which are among the most extensive in the world.
In those parts where the oldest structures of the Earth were not flooded by the seas, or where marine sediments were washed away in subsequent eras, ancient foundations come to the surface - the so-called shields. There are also underground foundation outlets that approach the surface closely (Voronezh crystalline massif). Don reached its arch only in one place.
Stable platforms increased in size over time - sections of neighboring folded zones were soldered to them, acquiring rigidity during the process of crushing. At the end of the Precambrian era, i.e. 500-600 million years ago, the Baikal folding sharply increased the Precambrian core of the future Siberian platform: huge folded massifs of the Baikal region and parts of Transbaikalia were attached to the Aldan shield.
During the Paleozoic era, powerful folding shook the earth's crust twice. The first, called the Caledonian folding, occurred in several stages in the early Paleozoic 300-400 million years before the present day. His monuments remain in the folds in the center of the Sayan Mountains. The second, called the Hercynian folding, occurred in the late Paleozoic (200-250 million years ago) and turned a huge trough of the earth’s crust between the Russian and Siberian platforms into the Ural-Tien Shan folded zone. As a result of this folding, the Russian and Siberian platforms united into an integral continent - the basis of the future Eurasia.
In the wide belt adjacent to the Pacific Ocean, the main stage of crushing of the earth's crust was the Mesozoic era - 60-190. its structures, called Pacific, built up the Siberian platform from the east, forming powerful folded areas in Primorye, Amur region, Transbaikalia and in the northeast of Siberia.
Only two vast strips, where the restless regime was preserved, did not lose their pliability to the dislocations after the Mesozoic movements. One stretched through the Alps and the Caucasus to the Himalayas. The second strip, bordering the east of Asia and including the western margins of the Pacific Ocean, is the East Asian folded region. Both areas continued to exist not only in the Mesozoic, but also later. It was in the Cenozoic, i.e. in the last 60 million years, they turned out to be the scene of powerful crumples. Here the last of the foldings unfolded - the Alpine folding, during which the subsoil of the Caucasus, Sakhalin, Kamchatka and the Koryat Highlands were crushed. These active areas continue to exist today, manifesting their activity through numerous earthquakes and, in East Asian mountain-island arcs, volcanism.
In the second half of the Alpine era of folding - in the Neogene, 10-20 ml. years ago, a completely new stage in the history of the earth’s crust began, which had special significance for the modern relief. It is associated with recent, or neotectonic movements, mainly vertical uplifts and subsidences, which covered not only the Alpine mobile zones, but also structures significantly removed from them of very different ages.
The youngest folded zones were subjected to very intense impact: the Caucasus, Sakhalin and the Kuril-Kamchatka arc. All these mountainous countries now exist not so much as a result of recent folding, but as a result of the recency and intensity of these new vertical uplifts. In the general diagonal belt of mountains, the uplift involved structures of different ages, such as Precambrian (southern Aldan Shield, Baikalids of the Stanovoy Range and Highlands), Paleozoic (Hercynides of Altai, Urals), Mesozoic (northeast Asia). The latest movements were expressed not only in uplifts, but also in descents. Depressions in the earth's crust created the modern appearance of sea depressions and large lakes, many lowlands and basins (Baikal). The foothill depressions adjacent to the young mountains were subjected to especially strong subsidence.
The stability of platforms in relation to crushing does not mean immobility in general. Both platforms and folded areas are subject to another type of movement - alternating vertical oscillations (swelling and subsidence).
The relationship between relief and the structure of the earth's crust is approximately as follows: the higher the surface area, the greater the thickness of the crust. The largest is where the mountain formations are (40-45 km), the smallest is the basin of the Sea of Okhotsk. Isostatic equilibrium. At the contact of the Eurasian and North American plates, plates move apart (Moma Rift) and a zone of diffuse seismicity forms. The latter is also characteristic of the margin of the Sea of Okhotsk plate. At the contact of the Eurasian and Amur there is also a movement - the Baikal Rift. The Okhotsk Sea at the contact with the Amur Sea (Sakhalin and the Sea of Japan) plate convergence is 0.3-0.8 cm per year. The Eurasian Sea borders on the Pacific, North American, African (Arabian) and Indian (Indostano-Pamir). The lithospheric compression belts between them are the Alpine-Asian in the south and the Circum-Pacific in the east. The margins of the Eurasian plate are active in the east and south and passive in the north. In the east, the oceanic subducts under the continental: the junction zone consists of marginal seas, island arcs and a deep-sea trench. In the south there are mountain ranges. The passive margins in the north are a huge shelf and a clearly defined continental slope.
Eurasia is characterized by linear and ring structures, established from satellite images, geological, geophysical and geological studies. seismic cores of the continental crust. Nuclears, 14.
The heat flow of the Earth on the territory of Russia has different values: the lowest values are on ancient platforms and the Urals. Increased - on all young platforms (slabs). Maximum values – fold belts, Baikal rift, marginal seas of the TO.
With depth, the temperature in the Earth gradually increases. Under the oceanic plates, the temperature of the mantle reaches the melting point of mantle rocks. Therefore, the surface of the beginning of melting of mantle material is taken as the base of the lithosphere under the oceans. Below the oceanic lithosphere, the mantle material appears to be partially molten and plastic with reduced viscosity. The plastic layer of the mantle stands out as an independent shell - the asthenosphere. The latter is clearly expressed only under oceanic plates; under thick continental plates it is practically absent (basaltic magmatism). In the context of continental plates, it can only appear in the case when hot mantle material, due to the splitting of the plate, can rise to the level at which this substance begins to melt (80-100 km).
The asthenosphere does not have a tensile strength and its substance can deform (flow) under the influence of even very small excess pressures, although very slowly due to the high viscosity of the asthenospheric substance (about 10 18 - 10 20). For comparison, the viscosity of water is 10 -2, liquid basaltic lava is 10 4 - 10 6, ice is about 10 13 and rock salt is about 10 18.
Movements of lithospheric plates along the surface of the asthenosphere occur under the influence of convective currents in the mantle. Individual lithospheric plates can diverge, move closer together, or slide relative to each other. In the first case, tension zones with rift cracks along the boundaries of the plates appear between the plates, in the second - compression zones, accompanied by the thrust of one of the plates onto the other, in the third - shear zones, transform faults, along which the neighboring plates are displaced.
As the main categories of tectonic areas, we will distinguish: 1. relatively stable areas - ancient platforms, mainly possessing a pre-Proterozoic metamorphic basement, 2. mobile mobile Neogean belts, consisting of folded areas of different ages (in place of dead geosynclinal areas) and modern geosynclinal areas, 3. areas, transitional - metaplatforms.
Ancient platforms, or cratons, represent vast areas of ancient continental crust, measuring millions of square kilometers, largely formed in the Archean and almost entirely by the end of the Early Proterozoic. Neogean is a relatively calm tectonic regime: “sluggishness” of vertical movements, their weak differentiation in area, relatively low rates of uplift and subsidence (less than 1 cm/thousand years). At the early megastage of development, most of their area experienced uplift, and subsidence mainly involved narrow linearly elongated graben-like depressions - aulacogens. At the later, slab megastage (Phanerozoic), a significant area of platforms was drawn into the subsidence, on which a cover of almost undisplaced sediments was formed - a slab. Simultaneously with the subsidence of the foundation, areas of platforms became isolated within the plates, which throughout most of their history had a tendency to rise and represented extensive protrusions of the ancient foundation - shields.
The cover of ancient platforms usually does not bear traces of metamorphic changes, which, like the absence or limited development of manifestations of magmatism, is explained by a significant decrease in the thermal regime during the formation of ancient platforms and, as a rule, low heat flow over most of their territory (except for aulacogens). However, in some zones of the ancient platforms, manifestations of magmatism took place, and in certain rare phases, due to the anomalous heating of the upper mantle beneath them, the ancient platforms could become the scene of powerful trap magmatism in effusive and intrusive forms.
Movable belts. They were founded mainly in the ancient Proterozoic. Their development goes through 2 megastages: geosynclinal (the greatest tectonic mobility, expressed in differentiated horizontal and vertical movements and a high, albeit unstable thermal regime in the crust and upper mantle) and postgeosynclinal (in place of dead geosynclinal belts, activity is reduced, but much more, than on ancient platforms).
The total duration of the goesynclinal process is 1-1.5 billion years, but in some areas it ends earlier. “Cycles”, the geosynclinal stage itself and the shorter orogenic stage (orogenesis) are distinguished.
Actually geosynclinal: stretching of the crust, the appearance of elongated graben-like depressions. Wide deflections break up into narrow ones. At the end there is the gesyncle itself. stages stop descending. At the beginning of the orogenic stage, they undergo strong compressive deformations (from the internal zones to the periphery). They turn into folded structures. During the orogenic stage, they experience gradually increasing uplift, not fully compensated by denudation, and at the late orogenic stage they turn into mountain structures. Thus, a complete reversal of the tectonic plan occurs (geosynclinal troughs into mountain uplifts). At the same time, in the zones of growing folded structures, marginal troughs appear, as if compensating for their uplift, and in the rear - internal troughs or depressions filled with fragmentary material.
The “cycles” into which the process of development of geosynclinal belts breaks down end with a relative strengthening of the crust, which acquires over a significant (or entire) area the features of a typical (mature) continental-type crust. At the beginning of the next “cycle”, partial destruction of this crust and regeneration of the geosynclinal regime occurs, while other areas are excluded from the further geosynclinal process.
In most of the North Atlantic mobile belt, the geosynclinal process ended in the middle of the Paleozoic, in the Ural-Mongolian belt - in the late Paleozoic - early Mesozoic, in most of the Mediterranean belt it is close to completion, and significant parts of the Pacific belt are still at different stages of the geosynclinal process.
Metaplatform areas. Something average in the nature of tectonic structures, the degree of crustal mobility and the characteristics of tectonic movements. On the borders. Structurally, it is a combination of two main types of tectonic elements - mobile aulakogeosynclinal zones and relatively “hard” metaplatform massifs, separated by these zones from ancient platforms. Avlacogeosynclinal zones represent linearly elongated zones of an intermediate nature between the aulacogens of ancient platforms and geosynclinal troughs of mobile belts. In the Late Proterozoic, simultaneously with the mobile belts framing the platforms, usually branching off from the latter. Graben-like troughs – compression – metamorphism, intrusion of intrusive bodies – folded zones (Donetsk, Timan).
The role of climate in human life is difficult to overestimate. It determines the ratio of heat and moisture, and, consequently, the conditions for the occurrence of modern relief-forming processes, the formation of internal waters, the development of vegetation, and the placement of plants. Climate features have to be taken into account in human economic life.
Influence of geographical location.
| Latitudinal position | Determines the amount of solar radiation arriving at the surface, as well as its intra-annual distribution. Russia is located between 77 and 41°, but its main area is between 50 and 70°. This determines Russia’s position in high latitudes, in the temperate and subarctic zones, which predetermines sharp changes in the amount of incoming solar radiation according to the seasons of the year. The large extent from north to south determines significant differences between the north and south of the territory. The annual total solar radiation is 60 kcal/cm2, in the extreme south – 120 kcal/cm2. |
| The country's position in relation to the oceans | Directly affects the distribution of cloudiness, and therefore the ratio of diffuse and direct radiation, and the supply of moist air. Russia is washed by seas from the north and east, which is not significant given the prevailing western transport and only affects the coastal strip. In the Far East, a sharp increase in cloudiness reduces the influx of direct solar radiation, amounting to the same value as in the north of the Kola Peninsula, Yamal, and Taimyr. |
| Position of the country in relation to pressure centers (CPC) | Azores and Arctic highs, Aleutian and Icelandic lows. Determine the prevailing wind direction, weather type, and prevailing air masses. |
| Relief | The location of mountains in the south and east and openness to the Arctic Ocean provide the influence of the North Atlantic and Arctic Ocean on most of the territory of Russia, limiting the influence of Ton and Central Asia. - The height of the mountains and their location in relation to the prevailing air currents determine different degrees of influence - Aggravation of cyclones - Mountain climate that changes with altitude - Differences in the climate of windward and leeward slopes, mountain ranges and intermountain basins - On the plains the differences are much weaker |
| Features of the underlying surface | Snow increases the reflectivity of the surface, black soils and forests decrease it. Differences in albedo are one of the reasons for differences in the radiation balance of territories receiving the same total radiation. Moisture evaporation and plant transpiration also vary from place to place. |
Air masses and their frequency. Russia is characterized by three types of air masses: arctic air, temperate air and tropical air.
In most parts of the country, air masses predominate throughout the year moderate latitudes, represented by two sharply different subtypes: continental and maritime. Continental The air is formed directly over the mainland and is dry throughout the year, with low temperatures in winter and fairly high temperatures in summer. Nautical air comes from the North Atlantic, and to the eastern regions - from the northern part of To. Compared to continental air, it is more humid, cooler in summer and warmer in winter. Moving across the territory of Russia, the sea air quickly transforms, acquiring continental features.
Arctic the air is formed above the ice of the Arctic, so it is cold, has low absolute humidity and high transparency. Impact on the northern part of the country, especially SS and NE. During transition seasons it causes frosts. In summer, moving forward and becoming increasingly dry, it brings droughts and hot winds (south EE and WS). The air formed over the Arctic can be designated continental. Only over the Barents Sea does the Arctic sea form.
Tropical air over the southern territories is formed over Central Asia, Kazakhstan, the Caspian lowland, and the eastern regions of the Ciscaucasia and Transcaucasia as a result of the transformation of air in temperate latitudes. Characterized by high temperatures, low humidity and low transparency. Tropical sea air from the central regions sometimes penetrates to the south of the Far East, and to the Caucasus from the Mediterranean. Characterized by high humidity and high temperatures.
Atmospheric fronts.
Physico-geographical conditions of the territory. The underlying surface over which they form and acquire new properties has a great influence. Thus, in winter, moist air masses bring latent heat of vaporization to a cold surface and warming occurs. In summer, moist air masses also bring precipitation, but on the warm underlying surface, evaporation and slight cooling begin.
The influence of relief on climate is great: with altitude, the temperature drops by 0.6°C for every 100 meters (due to a decrease in the radiation balance), and atmospheric pressure decreases. The influence of exposure is felt. Mountains play an important barrier role.
Special role – sea currents. Warm North Atlantic, cold around the Kuril Islands, Kamchatka, Sea of Okhotsk.
Climatic features of the winter period. During the cold season in Russia, from October to April, an area of high pressure (Asian maximum) is established, an area of low pressure develops off the eastern coast (Aleutian minimum) and the Icelandic minimum intensifies, reaching the Kara Sea. Between these main pressure centers of the winter period, the differences in pressure reach the greatest values and this contributes to the aggravation of circulation processes.
In connection with the western transport, the development of cyclones and anticyclones, circulation processes are very pronounced and they largely determine the distribution of heat and moisture. The influence of the Atlantic, Asian High, Aleutian Low and solar radiation is clearly visible.
In winter, air masses from the Atlantic Ocean bring a large amount of heat to the mainland. Therefore, in the EE and northern half of the WS, the temperature decreases not so much from south to north, but from west to east and northeast, which is confirmed by the course of January isotherms.
The impact of the Asian High is reflected in the extremely low temperatures of Central Siberia, the Northeast and the position of the isotherms. In the basins the temperature reaches -70 (the cold pole of the northern hemisphere - Oymyakon and Verkhoyansk).
In the Far East, the Aleutian minimum and the Okhotsk branch of the Arctic front predetermine cyclonic activity, which is reflected in warmer and snowier winters than on the continent, so January isotherms run parallel to the coast.
The greatest amount of winter precipitation falls in the west, where air flows from the Atlantic in cyclones. From west to east and northeast, the amount of precipitation gradually decreases.
Climatic features of the summer period. The ratio of radiation and circulation conditions changes dramatically. The temperature regime is determined by radiation conditions - all land heats up significantly more than the surrounding water areas. Therefore, already from April to October the isotherms extend almost sublatitudinally. In July, throughout Russia, average monthly temperatures are positive.
In summer, the Azores maximum moves north and its eastern branch penetrates the EE plain. From there, the pressure decreases to the north, south and east. The Arctic maximum remains above the Arctic Ocean. Therefore, cold air moves into the interior, warmer territories of Russia, where it heats up and moves away from its saturation point. This dry air contributes to the occurrence of droughts, sometimes with hot winds in the southeast of the EE plain, in the south of the WS plain and in the north of Kazakhstan. The development of dry, clear and warm weather is also associated with the spur of the Azores High. Over TO, the North Pacific High moves north (the Aleutian Low disappears), and sea air rushes toward land. The Far Eastern summer monsoon begins.
In summer, there is also a western transfer - from the Atlantic - of the greatest amount of precipitation.
All air masses entering the country in summer are transformed into continental air of temperate latitudes. On atmospheric fronts (Arctic and polar), cyclonic activity develops. It is most pronounced on the polar front over the EE plain (continental and maritime temperate).
The Arctic front is expressed within the Barents and Kara seas and on the coast of the eastern seas of the Arctic Ocean. Along the Arctic front, cyclonic activity intensifies and causes prolonged drizzle in the subarctic and arctic zones. In summer, maximum precipitation occurs, which is associated with increased cyclonic activity, moisture content of air masses and convection.
Changes in radiation and circulation conditions occur in spring and autumn. In the spring, the negative radiation balance turns into a positive one, and in the fall, vice versa. In addition, the position of areas of high and low pressure, the type of air masses, and, consequently, the position of atmospheric fronts change.
