Ural mountains
2. Geological structure, relief, minerals
Ural mountains formed in the late Paleozoic during the era of intensive mountain building (Hercynian folding). The formation of the Ural mountain system began in the late Devonian (about 350 million years ago) and ended in the Triassic (about 200 million years ago).
It is an integral part of the Ural-Mongolian folded geosynclinal belt. Within the Urals, deformed and often metamorphosed rocks of predominantly Paleozoic age come to the surface. The strata of sedimentary and volcanic rocks are usually strongly folded, disturbed by ruptures, but in general they form meridional bands, which determine the linearity and zonality of the structures of the Urals. From west to east stand out:
§ Cis-Ural marginal foredeep with a relatively flat bedding of sedimentary strata in the western side and more complex in the eastern side;
§ zone of the western slope of the Urals with the development of intensely folded and disturbed by thrust sedimentary strata of the lower and middle Paleozoic;
§ Central Ural uplift, where among the sedimentary strata of the Paleozoic and Upper Precambrian, older crystalline rocks of the edge of the East European Platform outcrop in places;
§ system of deflections-synclinories east slope(the largest are Magnitogorsk and Tagil), made mainly by Middle Paleozoic volcanic strata and marine, often deep-sea sediments, as well as deep-seated igneous rocks (gabbroids, granitoids, less often alkaline intrusions) breaking through them - the so-called. greenstone belt of the Urals;
§ Ural-Tobolsk anticlinorium with outcrops of older metamorphic rocks and wide development of granitoids;
§ East Ural synclinorium, in many respects similar to Tagil-Magnitogorsk.
At the base of the first three zones, according to geophysical data, an ancient, Early Precambrian, basement, composed mainly of metamorphic and igneous rocks and formed as a result of several epochs of folding. The oldest, presumably Archean, rocks come to the surface in the Taratash ledge on the western slope of the Southern Urals. Pre-Ordovician rocks in the basement of the synclinories of the eastern slope of the Urals are unknown. It is assumed that the Paleozoic volcanic strata of synclinoria are based on thick plates of hypermafic and gabbroids, which in some places come to the surface in the massifs of the Platinum-bearing belt and other related belts; these plates, possibly, are outcasts of the ancient oceanic bed of the Ural geosyncline. In the east, in the Ural-Tobolsk anticlinorium, outcrops of Precambrian rocks are rather problematic.
The Paleozoic deposits of the western slope of the Urals are represented by limestones, dolomites, sandstones, formed in conditions of predominantly shallow seas. To the east, deeper sediments of the continental slope are traced in a discontinuous band. Even further east, within the eastern slope of the Urals, the Paleozoic (Ordovician, Silurian) section begins with altered volcanic rocks of basalt composition and jasper, comparable to bottom rocks. modern oceans. In places above the section, there are thick, also altered spilite-natro-liparitic strata with deposits of copper pyrite ores. Younger deposits of the Devonian and partly Silurian are mainly represented by andesite-basalt, andesite-dacitic volcanics and greywackes, corresponding to the stage in the development of the eastern slope of the Urals, when the oceanic crust was replaced by a transitional type crust. Carboniferous deposits (limestones, grey-wackes, acidic and alkaline volcanics) are associated with the latest, continental stage of development of the eastern slope of the Urals. At the same stage, the main mass of Paleozoic, essentially potassium, granites of the Urals, which formed pegmatite veins with rare valuable minerals, also intruded.
In the Late Carboniferous-Permian, sedimentation on the eastern slope of the Urals almost stopped and a folded mountain structure formed here; on the western slope at that time, the Cis-Ural marginal foredeep was formed, filled with a thick (up to 4-5 km) strata of detrital rocks that were carried down from the Urals - molasse. Triassic deposits have been preserved in a number of depressions-grabens, the occurrence of which in the north and east of the Urals was preceded by basalt (trap) magmatism. Younger strata of Mesozoic and Cenozoic platform deposits gently overlap folded structures along the periphery of the Urals.
It is assumed that the Paleozoic structure of the Urals was laid down in the Late Cambrian - Ordovician as a result of the splitting of the Late Precambrian continent and the expansion of its fragments, as a result of which a geosynclinal depression was formed with crust and oceanic-type sediments in its inner part. Subsequently, the expansion was replaced by compression and ocean trench began to gradually close and "overgrow" with the newly formed continental crust; the nature of magmatism and sedimentation changed accordingly. The modern structure of the Urals bears traces of the strongest compression, accompanied by a strong transverse contraction of the geosynclinal depression and the formation of gentle scaly overthrusts - ridges.
The Urals is a whole system of mountain ranges stretched parallel to one another in a meridional direction. As a rule, there are two or three such parallel ranges, but in some places, with the expansion of the mountain system, their number increases to four or more. So, for example, orographically very complex Southern Urals between 55 0 and 54 ° N. sh., where there are at least six ridges. Between the ridges lie vast depressions occupied by river valleys.
The orography of the Urals is closely related to its tectonic structure. Most often, ridges and ridges are confined to anticlinal zones, and depressions - to synclinal ones. Inverted relief is less common, associated with the presence of rocks more resistant to destruction in synclinal zones than in adjacent anticlinal zones. Such a character has, for example, the Zilair plateau, or the South Ural plateau, within the Zilair synclinorium.
In the Urals, lowered areas are replaced by elevated ones - a kind of mountain nodes, in which the mountains reach not only their maximum heights, but also their greatest width. It is remarkable that such knots coincide with the places where the strike of the Ural mountain system changes. The main ones are Subpolar, Middle Ural and South Ural. In the Subpolar node, lying at 65 ° N. sh., Ural deviates from the south-western direction to the south. Here rises the highest peak of the Ural Mountains - Mount Narodnaya (1894 m). The Middle Urals junction is located at about 60°N. sh., where the strike of the Urals changes from south to southeast. Among the peaks of this knot, Mount Konzhakovsky Kamen (1569 m) stands out. The South Ural node is located between 55 0 and 54 0 s. sh. Here, the direction of the Ural ranges becomes south-western instead of south-western, and Iremel (1582 m) and Yamantau (1640 m) attract attention from the peaks.
common feature relief of the Urals is the asymmetry of its western and eastern slopes. The western slope is gentle, passes into the Russian Plain more gradually than the eastern one, which steeply descends towards the West Siberian Plain. The asymmetry of the Urals is due to tectonics, the history of its geological development.
Another orographic feature of the Urals is associated with asymmetry - the displacement of the main watershed ridge, which separates the rivers of the Russian Plain from the rivers of Western Siberia, to the east, closer to the West Siberian Plain. This ridge is different parts Ural wears different names: Uraltau in the Southern Urals, Belt Stone in the Northern Urals. At the same time, it is not the highest almost everywhere; the largest peaks, as a rule, lie to the west of it. Such a hydrographic asymmetry of the Urals is the result of increased "aggressiveness" of the rivers of the western slope, caused by a sharper and faster uplift of the Cis-Urals in the Neogene compared to the Trans-Urals.
Even with a cursory glance at the hydrographic pattern of the Urals, the presence of sharp, elbow turns in most rivers on the western slope is striking. In the upper reaches of the river flow in the meridional direction, following the longitudinal intermountain depressions. Then they turn sharply to the west, sawing often high ridges, after which they again flow in the meridional direction or retain the old latitudinal direction. Such sharp turns are well expressed in Pechora, Shchugor, Ilych, Belaya, Aya, Sakmara and many others. It has been established that the rivers saw through the ridges in places where the axes of the folds are lowered. In addition, many of them, apparently, are older than mountain ranges, and their incision proceeded simultaneously with the uplift of the mountains.
A small absolute height determines the predominance of low-mountain and mid-mountain geomorphological landscapes in the Urals. The peaks of many ranges are flat, while some mountains are domed with more or less soft outlines of the slopes. In the Northern and Polar Urals near upper bound forests and above it, where frosty weathering is vigorously manifested, stone seas (turmeric) are widespread. These places are also characterized by upland terraces resulting from solifluction processes and frost weathering.
Alpine landforms are extremely rare in the Ural Mountains. They are known only in the most elevated parts of the Polar and Subpolar Urals. The bulk of modern glaciers of the Urals are connected with the same mountain ranges.
"Lednichki" is not an accidental expression in relation to the glaciers of the Urals. Compared to the glaciers of the Alps and the Caucasus, the Urals look like dwarfs. All of them belong to the cirque and cirque-valley type and are located below the climatic snow boundary. Total number glaciers in the Urals - 122, and the entire area of glaciation is only a little over 25 km 2. Most of them are in the polar watershed part of the Urals between 67 0 -68 0 s. sh. Caro-valley glaciers up to 1.5-2.2 km long have been found here. The second glacial region is located in the Subpolar Urals between 64 0 and 65 ° N. sh.
The main part of the glaciers is concentrated on the more humid western slope of the Urals. It is noteworthy that all Ural glaciers lie in cirques of eastern, southeastern, and northeastern exposures. This is explained by the fact that they are inspired, that is, they were formed as a result of the deposition of snowstorm snow in the wind shadow of mountain slopes.
Didn't differ great intensity in the Urals and the ancient Quaternary glaciation. Reliable traces of it can be traced to the south no further than 61 ° N. sh. Such glacial landforms as kars, cirques and hanging valleys are quite well expressed here. At the same time, the absence of ram foreheads and well-preserved glacier-accumulative forms, such as drumlins, eskers, and terminal moraine ridges, draws attention. The latter suggests that ice sheet in the Urals it was low-powered and not active everywhere; significant areas, apparently, were occupied by inactive firn and ice.
A remarkable feature of the Ural relief is the ancient leveling surfaces. They were first studied in detail by V. A. Varsanofyeva in 1932 in the Northern Urals and later by others in the Middle and Southern Urals. Various researchers in different places of the Urals count from one to seven leveled surfaces. These ancient leveling surfaces serve as convincing proof of the uneven uplift of the Urals in time. The highest of them corresponds to the most ancient cycle of peneplanation, falling on the lower Mesozoic, the youngest, lower surface is of Tertiary age.
I.P. Gerasimov denies the existence of leveling surfaces of different ages in the Urals. In his opinion, there is only one leveling surface here, formed during the Jurassic-Paleogene and then subjected to deformation as a result of the latest tectonic movements and erosional erosion.
It is difficult to agree that for such a long time as the Jurassic-Paleogene, there was only one undisturbed denudation cycle. But I.P. Gerasimov is undoubtedly right in emphasizing the great role of neotectonic movements in the formation of the modern relief of the Urals. After the Cimmerian folding, which did not affect the deep Paleozoic structures, the Urals during the Cretaceous and Paleogene existed in the form of a strongly peneplanated country, on the outskirts of which there were also shallow seas. The modern mountain appearance of the Urals acquired only as a result of tectonic movements that took place in the Neogene and Quaternary period. Where they reached a large scale, now the highest mountains rise, and where tectonic activity was weak, ancient peneplains lie little changed.
Karst landforms are widespread in the Urals. They are characteristic of the western slope and Cis-Urals, where Paleozoic limestones, gypsums and salts karst. The intensity of the manifestation of karst here can be judged by the following example: for the Perm region, 15 thousand karst sinkholes have been described in detail surveyed 1000 km2. The largest in the Urals is the Sumgan Cave (Southern Urals), 8 km long, the Kungur Ice Cave with numerous grottoes and underground lakes is very famous. Other large caves are Divya in the area of Polyudova Ridge and Kapova on the right bank of the Belaya River.
The Ural Mountains are a treasure trove of various minerals. There are 48 types of minerals in the Ural Mountains.
The Uraltau anticlinorium forms the axial, highest part of the mountain structure of the Urals. It is composed of rocks of the pre-Ordovician complex (lower structural stage): gneisses, amphibolites, quartzites, metamorphic schists, etc. Strongly compressed linear folds are developed in the anticlinorium, overturned to the west or east, which gives the anticlinorium a fan-shaped structure. Along the eastern slope of the anticlinorium runs the Main Ural Deep Fault, which is associated with numerous intrusions of ultramafic rocks. A large complex of minerals is associated with them: deposits of nickel, cobalt, chromium, platinum, Ural gems. Iron deposits are associated with the thickness of the Riphean deposits.
In the relief, the anticlinorium is represented by a narrow meridionally elongated ridge. In the south it is called Uraltau, to the north - the Ural Range, even further - Poyasovy Stone, Research, etc. This axial ridge has two bends to the east - in the region of the Ufimsky horst and the Bolshezemelsky (Usinsky) vault, i.e. where it goes around the hard blocks of the Russian plate.
The Magnitogorsk-Tagil (Zelenokamenny) synclinorium stretches along the entire Urals up to the coast of Baydaratskaya Bay. It is composed of the Ordovician-Lower Carboniferous sedimentary-volcanogenic complex. Diabases, diabase-porphyries, tuffs, various jaspers (green, meat-red, etc.), extensive acidic intrusive bodies (trachytes, liparites), and in some places very strongly metamorphosed limestones (marbles) are widespread here. In the fault zones that limit the synclinorium, there are intrusions of ultramafic rocks. All rocks are strongly sheared. Often the rocks have undergone hydrothermal alteration. This is a copper-pyrite strip, where there are hundreds of copper deposits. Deposits of iron ore are confined to the contact of granites with limestones of the Lower Carboniferous. There is placer gold and Ural gems (precious and semi-precious stones).
In the relief, this zone is represented by short ridges and individual massifs up to 1000–1200 m and higher, located among vast depressions along which river valleys are laid.
The Ural-Tobolsk, or East Ural, anticlinorium can be traced along the entire folded structure, but is part of the Ural mountain country only its southern part is included, since north of Nizhny Tagil it is hidden under the cover of the Meso-Cenozoic cover of the West Siberian Plate. It is composed of shale and volcanogenic strata of the Paleozoic and Riphean, penetrated by intrusions of granitoids, predominantly of the Upper Paleozoic age. Sometimes the intrusions are enormous. They are associated with deposits of high quality iron and gold. Short chains of ultramafic intrusions are also traced here. Ural gems are widespread.
In the relief, the anticlinorium is represented by a ridged strip of the eastern foothills and the Trans-Ural peneplain. The Ayat synclinorium is part of the Urals only with its western wing on far south region. To the north and east it is overlain by the Meso-Cenozoic sedimentary cover. The siclinorium is composed of highly crushed and crushed deposits, Paleozoic, intruded igneous rocks different composition, protruding from under the cover of Paleogene deposits. Narrow graben-like depressions are developed here, filled with Triassic and Lower Jurassic deposits of the Turin and Chelyabinsk series. Coal deposits are associated with the latter. In the relief, the Ayat synclinorium is presented as part of the Trans-Ural plateau. Thus, the morphotectonic zones of the Urals differ from each other in their geological structure, relief and a set of minerals, so the natural zonal structure of the Urals is perfectly readable not only on a geological map, but also on mineral and hypsometric maps.
In the relief of the Urals, two strips of foothills (western and eastern) and a system of mountain ranges located between them, elongated parallel to each other in a submeridional direction, are clearly distinguished, corresponding to the strike of tectonic zones. There may be two or three such ridges, but in some places their number increases, up to six or eight. The ridges are separated from each other by extensive depressions along which rivers flow. As a rule, the ridges correspond to anticlinal folds, composed of older and more durable rocks, and depressions are synclinal.
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CAUCASUS
Relief and geological structure
The diversity of the relief makes it possible to distinguish within the Caucasus several orographic regions: Ciscaucasia, located between the Kuma-Manych depression and the mountains, and on the actual mountain structure of the Greater Caucasus.
Within Ciscaucasia the Kuban-Azov lowland stands out, the mountains of the Mineralnye Vody group (up to 1400 m.) - in the center, and the Tersko-Kuma lowland in the east.
Ciscaucasia occupies a vast territory, which is based on the Scythian plate. The surface of the slab foundation has a rather complex structure. Along her northern border situated Manych trough(up to 6 km), stretching almost 700 km from the Sea of Azov to the Caspian Sea. In relief it corresponds Kumo-Manych depression. The central part of Ciscaucasia is occupied by Stavropol Upland, reaching the highest heights in the southwest (Mount Strizhament - 831 m). The hill breaks off in clear ledges to the southwest (near Armavir its height reaches 326 m) and to the south. Its slopes, facing the northwest, north and northeast, are gentle. At the heart of the elevation is Stavropol vault, within which the depth of the foundation varies from 0.5 to 2.5 km. In the central part of the dome, the lower horizons of the sedimentary cover (Т-К) are absent, and the Aptian, Albian, and Upper Cretaceous deposits are thin.
To the west of the Stavropol Upland is located Kuban-Azov lowland, which is based on Azov-Kuban depression with a foundation depth of up to 3 km. The eastern part of Ciscaucasia is occupied Tersko-Kuma lowland, dated to the depression of the same name, within which the basement lies at a depth of 6 km or more. The Tersko-Kuma lowland is the southwestern outskirts of the Caspian lowland.
The upper layer of deposits of the lowland plains of Ciscaucasia is represented by loess-like loams, Neogene and Paleogene sandy-argillaceous, sometimes carbonate continental and marine deposits.
South of the Stavropol Upland there is a peculiar Mineral group of island mountains- laccoliths (Beshtau - 1401 m). To the west of it along the foot of the mountains stretches Kuban marginal foredeep, presented Kuban sloping plain, and to the east - Terek-Caspian trough, the northern part of which goes under the Tersko-Kuma lowland, and the southern slope is complicated by anticlinal folds Tersky(up to 664 m) and Sunzhensky(up to 926 m) ridges. From the south, they are adjoined by sloping plains (Kabardinsk, Ossetian, Chechen), gently descending from the foot of the Greater Caucasus to the north and northeast. The sedimentary cover in the marginal troughs reaches a thickness of 10-12 km. The upper part of the cover is represented by thick strata of fluvioglacial and alluvial boulder-pebble deposits overlain by loess-like loams.
The mineral-growing (Pyatigorsk) island mountains, the Tersky and Sunzha ranges occupy an intermediate position between the Greater Caucasus and Ciscaucasia (see Fig. 1). Both genetically (anticlinal folds and intrusions of laccoliths are associated with tectonic movements and volcanism of the Greater Caucasus), and morphologically (rather high mountain ranges and folded ridges), they are close to mountainous areas, but are confined to the marginal foredeep, and therefore are assigned to Ciscaucasia.
The most characteristic orographic area - The Greater Caucasus, a powerful folded system (4-5 thousand m), which is divided into the axial part, the Dividing Range, the Side Range, the Northern and Southern slopes. To the south stretches a strip of intermountain lowlands - Colchis and Kuro-Araks, separated by a low Suram ridge. Further to the south stretches the region of the Transcaucasian Highlands, framed from the north and northeast by chains of ridges of the Lesser Caucasus. In the southeast of Transcaucasia, the Talysh mountains stretch with the Lenkoran lowland adjoining them. The inner regions of the Transcaucasian Highlands are called the Javakhetian-Armenian Highlands, which is part of the vast uplands of Western Asia.
Rice. 1. Orohydrographic scheme of the Caucasus
The position of the Caucasus between regions that are very contrasting in nature, the influence of each of which can be traced primarily in the adjacent territories, increases the diversity of its nature. In the western and central parts Ciscaucasia and on the northern slope of the Greater Caucasus, the influence of the southern Russian steppes is traced. The nature of the Central Asian deserts left its mark on the eastern part of Ciscaucasia (through the Caspian lowland). The nature of the Black Sea coast of the Caucasus and the southwestern slopes of the mountains is influenced by the subtropical eastern Mediterranean. The areas of influence of neighboring territories are quite clearly demarcated by the orographic boundaries of the Greater Caucasus and the transverse uplift: the Stavropol Upland - the Central Caucasus - the Likhi Range, which are climatic divisions.
In the Caucasus, the dependence of hydroclimatic and biogenic components on the relief is very clearly revealed, the influence of the geological structure on other components of nature is clearly traced: runoff, soils, and vegetation. The mountains of the Caucasus are characterized by altitudinal zonality, which varies very significantly from western outskirts to the east. On the example of the Caucasus, the main features of nature and the patterns of their change inherent in mountainous countries are perfectly traced.
The nature of the Caucasus has been studied quite well. Many travelers and researchers of various specialties conducted their research here. At the end XVIII century during a trip to the southern regions of Russia, the North Caucasus was visited by P.S. Pallas. A quarter of a century in the mountains of the Caucasus worked G. Abikh, who published in 1858 and 1859. summary work on the orography and geology of the Caucasus. The accession of the Caucasus to Russia facilitated and accelerated its exploration by Russian travelers. Geologist M.V. worked here. Mushketov, soil scientist V.V. Dokuchaev, biogeographers N.M. Albov, A.N. Krasnov. Later, the geological structure of the Caucasus was studied by I.G. Kuznetsov, V.P. Renhardten, E.E. Milanovsky, V.E. Khain, N.V. Koronovsky and many others; relief - I.S. Schukin, N.V. Dumitrashko, N.A. Gvozdetsky and others; climate - I.V. Figurovsky; glaciers and avalanches - G.K. Tushinsky, S.V. Kalesnik; soil - S.A. Zakharov, A.I. Prasolov, S.V. Zonn and others; organic world- A.A. Grossheim, N.A. Bush, N.I. Kuznetsov, K.A. Satunin and others. A great contribution to the comprehensive study of the nature of the Caucasus was made by B.F. Dobrynin and N.A. Gvozdetsky.
The Greater Caucasus is a majestic mountain structure. Its width varies from 32 km near Novorossiysk to 180 km on the Elbrus meridian and 160 km in Dagestan. The Greater Caucasus is a large asymmetric meganticlinorium. The anticlinal structure is the most characteristic geological feature of the Caucasus. In its core, in the western and central parts of the mountain structure, Precambrian, Paleozoic and Triassic rocks of the lower structural stage are exposed.
Rice. 5. Geological profile through the cuestas of the Caucasus
Rice. 6. Geological profile through Inner Dagestan (according to A.E. Krivolutsky)
They are successively bordered by Jurassic, Cretaceous, Paleogene and Neogene strata of the upper structural stage.
Usually the Greater Caucasus is divided into several cross sections(segments) and three longitudinal zones(belts): axial uplift, represented by the Main, or Watershed, and Lateral Ranges with heights of more than 3000-4000 m (with the exception of the extreme northwest); the northern slope belt, which includes a system of parallel ridges, gradually lowering to the north; belt of the southern slope, located outside of Russia.
Along the strike of the Caucasus, four segments of different heights are usually distinguished. The highest is Central Caucasus located between Elbrus and Kazbek. Here are all the "five-thousanders" of Russia: Elbrus(5642 m), Dykhtau(5204 m), Shkhara(5068 m), Dzhangitau(5058 m), Kazbek(5033 m). Often the peaks of the Lateral Range rise higher than the Watershed Range. Both ranges are composed of solid Precambrian crystalline rocks, and the depression separating them is formed by the Lower Jurassic.
From Elbrus to Mount Fisht stretched Western Caucasus. It is below the central one. The highest point here is Dombay-Ulgen(4046 m). The watershed ridge is composed of crystalline rocks, and the Bokovoy ridge is composed of highly metamorphosed Paleozoic strata. The heights of the ridges decrease to the northwest.
From Fisht to the Taman Peninsula stretches Northwestern Caucasus, represented by the mid- and low-mountainous Black Sea chain. Its heights decrease from Mount Fisht (2868 m) to Novorossiysk to 500 m. The mountain ranges are composed of easily destroyed rocks of the Jurassic, Cretaceous and Paleogene. The Greater Caucasus is also tectonically related to Taman Peninsula, but the absence of mountainous relief there allows it to be attached to Ciscaucasia.
In the axial zone of the Central and Western Caucasus, glacial landforms dominate: sharp rocky ridges, pointed peaks (carlings), glacial cirques and cirques, and trough valleys. To the north and northeast of the Bokovoy ridge there is a system of cuestas of the northern slope: the Rocky ridge, armored by Upper Jura limestones, Pasture, Wooded, composed of Cretaceous and Paleogene strata.
The Eastern Caucasus stretches east of Kazbek. It is lower than the Central, but higher than the Western. A number of its peaks exceed 4000 m. The Vodorazdelny and Bokovoy ridges are also clearly visible here, but they are composed mainly of Jurassic shale. Here, glacial landforms are much less pronounced due to less glaciation in the past and present, as well as the predominance of easily destroyed clay shales, which does not contribute to the preservation of ancient landforms.
In front of the axial ridges within the northern slope of the eastern Caucasus lies an orographically complex mountainous region of Inner Dagestan, almost enclosed by the Andiysky, Salatau, Gimrinsky and other ridges, which is cut by four Koisu, forming the Sulak River. Inner Dagestan is composed mainly of Lower and Middle Jurassic shales (see Fig. 3). Only in its northern part are Upper Jurassic and Cretaceous limestones, which form high cliffs along the sides of river valleys, acquiring the appearance of tight deep canyons. To the north and east of Inner Dagestan lies Outer Dagestan with soft rounded relief forms.
Spreading glacial relief characteristic of the highlands, however, the predominant type of relief in the mountains and in Ciscaucasia is water erosion. Depth of erosional dissection in the Caucasus Mountains - largest in Russia. In the highlands, it averages 1500-2000 m, but in the upper reaches of the Chegem and Teberda it increases to 2500-3000 m. The deep division of the mountains into valleys is a consequence of young uplifts.
In Ciscaucasia, the processes of river accumulation and gully erosion dominate in uplifted areas. AT lower parts mountains, relatively recently former foothill plains, river valleys are expanded and incised by only 100-200 m. In the middle mountains, the incision depth increases to 500-1500 m, narrow steep gorges and canyons dominate. In the highlands, the valleys widen again. Trough-shaped troughs worked by the glacier prevail here. Erosive processes dissect the structure of a mountainous country. The different stability of rocks is due to the presence of cuesta ridges and island mountains in the vicinity of Pyatigorsk.
The great depth of dismemberment leads to an increase in gravitational processes, to frequent landslides, rockfalls, screes. The presence of shales and clays contributes to the development of landslides, and the distribution of carbonate rocks - to the development karst forms relief. On the Terek-Kuma lowland, there are eolian forms relief.
The nature and intensity of modern relief-forming processes depend on tectonic structures, lithological features of rocks, and the altitudinal position of the surface, which determines their spatial distribution within the Caucasus.
Colchis and Kura lowlands - tectonic depressions forming the Transcaucasian megasynclinorium. The Colchis lowland is composed mainly of Quaternary rocks, the Kuro-Araks lowland is composed of Neogene and Quaternary deposits.
To the south, the inner zone of folded structures of the Alpine geosynclinal region extends.
Lesser Caucasus in the west it passes into the Pontic Mountains, and its eastern extension - Talysh - is part of Elburz. In the western part of the M. Caucasus (Shavshetsky, Meskhetsky, Trialetsky ridges), Pg deposits are widely developed. This is roughly the structure of Talysh. The Jurassic, Cretaceous, and intrusive bodies participate in the structure of the eastern ranges of the M. Caucasus. Volcanic sedimentary and effusive rocks are widespread everywhere. Dislocated Jurassic, Cretaceous, Paleogene sedimentary rocks are widespread in the Transcaucasian Highlands, among which the products of volcanic activity that occurred in the sea basins play an important role. Limestones predominate, among Pg rocks there are clays, sandstones, carbonate rocks, and flysch accumulations. In the eastern part of the M. Caucasus, the Jurassic and Cretaceous rocks are penetrated in a number of places by powerful intrusions. A characteristic feature of the geological structure of the Javakheti-Armenian Highlands is the wide distribution of lava covers, tuffs and tuff formations of the Jurassic, Cretaceous, Paleogene and Quaternary period. The Talysh Mountains are a complex anticlinorium composed of flysch and volcanogenic deposits of Pg, in the north - sandy-clayey rocks of N.
Topic: Relief, geological structure and minerals of Eurasia.
Goals:
educational: explore features of the relief of the Eurasian continent, to find out the reasons for these features, to trace the relationship of the tectonic structure andplacement of minerals;
educational: to continue the formation of a scientific worldview when revealing the issue of the nature of the relief and minerals of Eurasia; contribute to the formation of an emotional and valuable attitude to the world.
developing: to develop the ability to work with a textbook, atlas, additional material, interactive whiteboard, contour maps.
Lesson objectives:
- Find out the reasons for the diversity of Eurasian landforms, through the definition of patterns of placement large forms relief and tectonic structuresR;
- To work out and consolidate the method of comparing the map "The structure of the earth's crust" and the physical map of Eurasia;
To acquaint students with the main areas of volcanism and earthquakes in Eurasia;
Continue to develop the ability to aim yourself at the task, exercise self-control and introspection learning activities,
- To continue the formation of the ability to analyze, compare, generalize and draw conclusions.
- Determine personally significant aspects of studying the relief of the mainland
Skills and abilities:
Name and show the main landforms, mineral deposits;
Describe the geographical location of large landforms;
Explain the features of the placement of large landforms on the mainland.
- compare and analyze maps in order to gain new knowledge, characterize the main landforms according to a standard plan, make inputs
Working methods: methods problem learning(partial search, research), methods of organizing educational and cognitive activity (verbal, visual, practical, analytical, synthetic, problem-search, independent work and work under guidance), methods of control and self-control.
Equipment: Interactive whiteboard, multimedia installation, physical map of the world, computer, notebooks, handouts. Atlas for grade 7 in geography, self-assessment sheets
Form of work: in pairs, individual
Lesson type: combined
During the classes.
1. Organizational moment: On each desk of students there is a self-assessment sheet, where tasks and their evaluation criteria, students' achievements are prescribed.1 min
2. Knowledge update. Knowledge check: students are invited to complete the task "Digital dictation". Each group of students has a worksheet. The guys work in pairs. A number of tasks are proposed to be completed on the self-assessment sheet.5 minutes
Exercise: Arrange the numbers corresponding to the seas that belong to these oceans.
Oceans: Arctic_________________
Atlantic______________________
Indian_________________________
Quiet_____________________________
Which oceans do the seas belong to?
1) Kara; 2) Beringovo; 3) Arabian; 4) Baltic; 5) Black; 6) Yellow; 7) Okhotsk, 8) Barents; 9) White; 10) Northern; 11) Mediterranean; 12) East China; 13) Azov; 14) Laptev; 15) Japanese
3. Learning new material:
Introductory speech of the teacher : You learned about the internal structure of the Earth, about the composition, structure and processes occurring in the outer shells, traveled on the earth's surface with the help of maps and mastered the techniques of working with them. We visited the five continents of the Earth and plowed the expanses of the oceans. And today we continue to study the Eurasian continent.
Question : Remembering the topic of the last lesson, please tell me why this is a special continent?
Answer: The largest continent in terms of area, the highest mountains, vast plains, diverse landscapes are located on it, many peoples live, etc.
If we have already studied the geographical location of the mainland, which topic, in accordance with the mainland study plan, will we study next?
Relief, tectonic structure and minerals of Eurasia
In order to study this topic We need:
To master the features of the structure, relief and minerals of Eurasia, to work out and consolidate the method of comparing the map "The structure of the earth's crust" and the physical map of Eurasia.
We will continue to practice the ability to compare, generalize and draw conclusions - that is, we will continue to learn to reflect.
LESSON PLAN
- Why is knowledge of the relief necessary when studying the mainland?
When characterizing the relief. What cards will we use?
Guys, let's remember what you know about the relief?
Exercise: look at the physical map and try to give a figurative description of the relief of Eurasia, highlight the features.
Students answer using leading questions.
Is the relief of Eurasia varied?
What can you say to the height of Eurasia?
Name the largest mountain range the globe.
What can you say about the number and size of the plains?
Find the highest and lowest point of Eurasia
Calculate the elevation fluctuations on the mainland.
Conclusion : Analyzing the map, we can conclude that:
Eurasia is higher than other continents
The highest mountain systems are located on its territory. Himalayas with Mount Chomolungma (Everest, 8848 m)
The plains are large in size and stretch for thousands of kilometers and occupy most of the territory of Eurasia.
Great fluctuations in heights (from the depression Dead Sea to the top of the Himalayas)
- Compare the relief of Eurasia and the relief of other continents. Try to highlight reasons for similarities and differences.
And what's the reason? (in the history of the development of the mainland)
Task 2. The plains and mountains of Eurasia have very different heights. Establish the correct sequence by numbering these territories as the heights increase. Atlas s. 48-49
landform
Height, m
West Siberian Plain
Central Siberian Plateau
over 1000 m
Kamen-1664m
The East European Plain
Khibiny 1191m
Caspian lowland
below 0 m (-28m below sea level)
Ural mountains
Narodnaya 1895 m
Highlands Tibet
Over 5000m
Iranian highlands
We conclude: Thus, we see that the relief of Eurasia is verycontrast andvaried .
The structure of the earth's crust within Eurasia.
With the help of what sources of information can we find out what structure the earth's crust has within Eurasia?(map "The structure of the earth's crust", "lithospheric plates" p. 8-9, 10 atlas)
How was the continent of Eurasia formed?(Pangea-Laurasia (northern) - Gondwana (southern)
If Eurasia is a continent, then what type of earth's crust lies at the base of this section of the earth's surface?Continental type of the earth's crust.
What parts of the earth's crust are continental type?Stable platforms and folded areas.
What is a platform?
What landforms correspond to the platforms?
What is a folded area? (tectonic folded a planetary scale structure separating ancient platforms from each other or from the ocean.)
How were folded regions formed?
What landforms correspond to folded regions?
What determines the structure, height and appearance of mountains?
Analysis of the map of the structure of the earth's crust with. 8-9, 10 atlas
What lies at the base of the Eurasian continent? (Eurasian lithospheric plate)
Are the sections of the Eurasian Plate the same age? (unequal)
- What passes along the boundary of lithospheric plates? (folded belts). We will return to this issue later.
Task 3: Using the map "The structure of the earth's crust" and the physical map of Eurasia, establish the relationship between the structure of the earth's crust and the placement of large landforms in the territory of Eurasia.
What patterns did you notice?(Mountains belong to the fold belts, and platforms - plains and plateaus).
- Why are fold belts located on the southern and eastern margins of the mainland? ( because here is the junction of lithospheric plates)
What plates does it border on? (In the south with the Indo-Australian and African-Arabian plates, in the east with the Pacific)
How does the Eurasian Plate interact with the Pacific Plate?
There is a collision of the continental Eurasian and oceanic Pacific plates - the oceanic plate goes under the continental one, deep-sea trenches with island arcs are formed, active volcanism occurs, earthquakes occur very often.
We formulate the conclusion: The reason for the diversity of the surface of the mainland in the structure and history of the development of the earth's crust.
seismically active belts. Earthquakes and volcanism.
What plates does the Eurasian Plate interact with in the east and south?
How are these parts of the mainland different?
What happens in such zones and what are they called?
- What do you remember about the Pacific ring of fire?
When was the last largest earthquake in this zone?
Give examples of active volcanoes (map work)
What else influenced the relief of Eurasia? Ancient glaciation.
(The relief of the mainland was also greatly influenced by the ancient glaciation, which captured the northern part of the mainland. Descending from the Scandinavian mountains, the ice smoothed their surface. After its melting in the East European Plain, south of Baltic Sea, in the north of Asia there were numerous moraines - accumulations of rock fragments of different sizes)
On the territory of Eurasia, through which the giant seismic belts of the globe pass, most of the earthquakes on Earth occur.The most active Pacific seismic belt many earthquakes are associated with them. European-Asian or the Alpine-Himalayan seismic belt runs along the southern margin of Eurasia. The areas of volcanism are also confined to seismic belts. There are especially many volcanoes in the Pacific Ring of Fire.”
Look at the map on p. 8-9 and 48-49 where does the Pacific seismic belt pass? (from the peninsula of Kamchatka to the Big Sunda Islands). It coincides with the Pacific volcanic ring and the earthquake belt. Therefore, sometimes the tops of mountain ranges are active and extinct volcanoes.
In the mountains of the Alpine-Himalayan fold belt, destructive earthquakes very often occur.
Volcanoes of Kamchatka(viewing the animation "Volcanoes of Kamchatka").
Pacific volcanic ring of fire (Pacific Ring of Fire, Pacific Ring, Pacific Ring of Fire) - perimeter area in which most of the active and a lot happens . In total, there are 328 active terrestrial volcanoes in this zone out of 540 known in the world. .
Task 4. Volcanism is widely developed in folded areas. Using a map, plot the numbers for the location of volcanoes:
1. Vesuvius (Apennine Peninsula)
2. Etna (Sicily)
3. Krakatoa (Great Sunda Islands)
4. Klyuchevskaya Sopka (Kamchatka Peninsula)
5. Fujiyama (Japanese Islands)
So, we examined the relief, the internal structure of the earth's crust. Whatcomponent is missing in this logical chain? ( Minerals. ) Working with the atlas pp. 48-49.
What can we already say about P/I Eurasia ? (P - diverse, p / i - diverse.)
Task 5. Eurasia is rich in minerals. Set match:
1. Gulf region
A. Gems
2. Half of Malacca
B. Iron ore
3. Island of Sri Lanka
B. Oil, gas
4. Scandinavian mountains
G. Tin rivers, D. Copper rivers
5. North of the Great Plain of China
E. Coal
Answer: 1.V., 2.G, 3.A. 4.B, 5.D.
Conclusion:On the plains, sedimentary minerals, and in the folded belts, igneous and metamorphic
4. Consolidation of the studied material.
Task 6: Fill in the missing words.
The relief of Eurasia ... .. (diverse)
Here are large ... (plains)
As well as the largest ... (mountain systems of the world)
The highest point of the peak ... .. (Chomolungma (Everest) 8848m).
The lowest place on the mainland .... (Dead Sea depression)
Altitude amplitude over ... (9000 m)
5. Summing up the lesson: summarize the topics of the lesson, analyze whether all tasks have been completed. Work with the self-assessment sheet. Mood. Results in points. Who got what grades?
6. Homework : § 60-61 to study, mark on the contour map the landforms of Eurasia.
Reflection:
Have we reached our intended goal?
What have we learned in class today?
What is the significance for you personally of the knowledge and skills acquired in the lesson?
Where can you apply the acquired knowledge in life?
Did you help others or were you helped?
What caused the most trouble?
How do you evaluate the knowledge gained today (conscious, deep, to be realized, unconscious)?
The length of the territory also determined the diversity of the relief: the European part of the country has a completely different appearance than the Asian one, and there are great differences across regions. 70% of Russia is occupied by plains, among which the most prominent are the East European Plain
(within which there are small, up to 250 - 400 m, uplands) in the western part of Russia, and West Siberian Plain- East of the Urals. They are divided Ural ridge
Most of which are mountains with a height of 800 - 1200 meters. Between the Yenisei and Lena is located Central Siberian Plateau
Dissected by a dense network of river valleys. Mountainous areas with a highly rugged relief prevail in the east (Aldan highlands, Verkhoyansk ridge, Stanovoye highlands) and in the south of the republic (Northern Caucasus, Altai, Sayans, etc.), as well as along the Pacific coast / 1, c. 422-423 /.
The relief is directly related to the geological structure of the earth's crust, which is also very heterogeneous. So, the East European Plain approximately corresponds to Russian,
a West Siberian - Siberian platform
These are very ancient areas of the crust, having a Precambrian folded foundation /1, p.423/, and active mountain-building processes have already ended there.
Between them is a younger Ural-Altai platform
Formed in the Paleozoic. Air and water did not have time to destroy the Ural and Altai mountains (formed as a result of the movement of the earth's crust in the Cenozoic era) / 2, p. 297 /, although they worked on them very thoroughly.
From the south, a younger region adjoins the Russian platform North Caucasus
which is characterized by a very significant seismic activity. To the east of the Siberian platform is the Primorsko-Chukotka region, which has a Mesozoic folded base. This is a young area in geological time with a predominance of hills /2, p.297/.
The mountainous regions of Kamchatka and the Pacific coast correspond to the belts of recent folding and volcanism. Geosynclinar development there has not yet been completed, which led to seismic and volcanic activity region and left a significant imprint on the life of Kamchatka and the Far East /3, c.100-101/. And there is no bad without good: geothermal springs, directly related to volcanism, represent a solid reserve of cheap energy.
The distribution of underground fossils
So, coal basins
predominantly correspond to the Carboniferous, Permian, Cretaceous periods. The most important coal basins are
Largest deposits oil and gas
are associated with Mesozoic and Tertiary deposits in the North Caucasus and Paleozoic deposits in the Volga-Ural and Ukhta-Pechersk oil and gas regions, as well as in Mesozoic deposits in Eastern Siberia and Yakutia /4, p.76/.
Iron ores
KMA and ore deposits of Karelia correspond to the Precambrian basement. Large ore reserves have also been discovered in the Paleozoic of Siberia and the Urals. Deposits are also associated with the Ural Paleozoic bauxites, copper ores, asbestos, potassium salts
As well as precious and semi-precious stones. Apatity
the Kola Peninsula is also rich (proterozoic), where there are also copper and nickel
In the North Caucasus (Mesozoic) mined tungsten, molybdenum, lead, zinc
In the Far East (Mesozoic) - lead, zinc, tin
Other minerals are also mined (mainly in the Mesozoic) gold, platinum, silver, mercury
The economic significance of these resources for Russia can hardly be overestimated: it is their export that keeps the Russian economy afloat, and it is precisely due to the fact that the cost of energy resources in the country is lower than on the world market that the economic downturn in Russia in recent years has been less sharp than in other republics former Union. However, we must not forget that mineral reserves are by no means unlimited, and many important sources are already close to depletion. Often, mining has a negative impact on the environment. Thus, being an indisputable economic trump card of Russia, they also carry a number of problems, without the solution of which it is impossible to save valuable resources for posterity.
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§ 12. Geological history and geological
structure of the territory of Russia
Earth's crust within modern Russia, it was formed over a long time as a result of various geological processes. Therefore, its parts differ: firstly, in the structure, composition and occurrence of rocks, and secondly, in age and history of development.
According to the structural features, mobile and stable sections of the earth's crust are distinguished. Mountain structures are located on mobile sites. They are composed of rocks crumpled into folds, divided by splits into separate blocks. These blocks move in different directions at different speeds. As a result of these movements, mountain ranges and depressions separating them are formed. Intensive movements of the earth's crust are often accompanied by earthquakes.
Most territory of Russia occupy stable areas of the earth's crust - platforms: East European, West Siberian and Siberian. Platforms have a two-tiered structure. Their lower part is the foundation. These are the remains of the collapsed mountain systems that previously existed on the site of modern platforms. Therefore, it consists of rocks crumpled into folds. Loose sedimentary rocks (sedimentary cover) overlie the foundation. They were formed during the destruction of mountains and the slow sinking of the foundation, when it was flooded with the waters of the seas. There is no sedimentary cover in some parts of the platforms. Such sections of platforms are called shields.
What is the "earth's crust" and what is its structure? What do you know about the theory of lithospheric plates? How do rocks differ in origin? How do mountains differ in height? What are plains? Name their types.
Rocks of folded belts and platforms have different age because they were formed over a long period of time.
The most important stages of the geological history of the territory of Russia and the age of the rocks that make up the earth's crust are reflected in geochronological table(Appendix). The entire geological history of the Earth is divided into 5 large time periods - eras. The name of each era is given in accordance with the type of life characteristic of it: Archean (earliest life), Proterozoic (early life), Paleozoic (ancient life), Mesozoic (average life), Cenozoic ( new life). The length of the eras varies greatly. In turn, eras are subdivided into smaller periods of time - periods. The names of the periods most often come either from the names of those areas where the rocks formed during this period were first studied in detail, or from the names of the rocks themselves.
The age and time of formation of individual rocks can be determined in different ways. If the original occurrence of rocks is not disturbed by subsequent geological processes, then the layers that lie above are younger than those located below. They help to determine the age of rocks and fossil remains of plants and animals. The more complex organisms are, the younger they are. Both of these methods make it possible to estimate the relative age of rocks.
They learned to determine the absolute age of rocks only in the 20th century. To do this, evaluate the process of decay of radioactive elements contained in rocks. The decay process is constant speed and does not depend on external conditions. Therefore, according to the ratio of the content in the rock of a radioactive element and its decay products, one can establish absolute age rock in billions and millions of years.
The earth's crust itself, consisting of a variety of sedimentary, igneous and metamorphic rocks, has a different age. The time of occurrence of sections of the earth's crust is shown in color on tectonic maps (Fig. 17).
The most ancient parts of the earth's crust on the territory of Russia - the East European and Siberian platforms,. Their foundation was formed in the Precambrian more than 1.5 billion years ago.
Late Proterozoic - early Paleozoic(1000-550 million years ago) Baikal folding occurred. In the Paleozoic, there were two foldings - Caledonian (550-400 million years ago) and Hercynian (400-210 million years ago). In the Mesozoic - Mesozoic. About 100 million years ago, the last Cenozoic (Alpine) folding began, which continues to the present. As a result of each folding, a new continental crust was formed and folded mountain belts were formed, bordering and connecting the East European and Siberian platforms. The largest belts stretching through the territory of Russia are the Ural-Mongolian, Alpine-Himalayan (Mediterranean), as well as part of the Pacific belt.
The formation of fold belts is associated with a collision lithospheric plates and crushing into folds of rocks accumulated on their outskirts.
Rice. 17. Tectonic structures of the world
Folding processes are accompanied by magmatism, metamorphism and earthquakes. Cenozoic (Alpine) mountains are formed as a result of the interaction of modern lithospheric plates. Mountains are located on the earth's crust of the Cenozoic age and are currently located.
Folded belts of Mesozoic and Paleozoic age were located on the boundaries of ancient lithospheric plates. Their number, size and shape have repeatedly changed throughout geological history. Many of them were later destroyed. In their place, young platforms were formed, the largest of which is the West Siberian. But some areas of Paleozoic and Mesozoic folding, due to active movements of the earth's crust, again became mountain structures.
Questions and tasks
1. Compare physical-geographical and tectonic maps.
2. According to fig. 17 and the physical map in the atlas, name the mountains located in the areas of the Hercynian and Caledonian folding.
3. According to fig. 17 identify the lithospheric plates that underlie the territory of Eurasia.
4. The collision of what plates led to the emergence of the Caucasus, the mountains of Kamchatka, Sakhalin, the Kuril Islands?
§ 13. Relief of Russia
The definition of relief is familiar to you, starting from the elementary grades.
Relief is the totality of all the irregularities of the earth's surface.
With these irregularities, small and large, easily and difficult to overcome, a person faces almost daily. During its economic activity he fills them up, levels them, overcomes them, decorates them, and sometimes even creates new ones for the Plains of Russia.
Landforms vary in size. Depending on it, they have different natural and economic impacts (Table 5). But different in size landforms are not isolated, but interconnected: smaller landforms are superimposed on larger ones.
The relief of Russia is very diverse. Mount Elbrus (5642 m) and the Caspian lowland (-27 m above sea level) are located on its territory.
From the point of view of the largest forms, the relief of our country is quite simple. It resembles an amphitheater tilted to the north.
Table 5
Dimensions of landforms
Rice. eighteen
Its basis is the three largest plains of the world: Russian, West Siberian and Central Siberian plateau. All of them are located on platforms. Plains occupy more than 70% of the territory of Russia. Therefore, without exaggeration, it can be called a country of gigantic plains. Average Height the territory of Russia is slightly more than 400 m. At the same time, lowlands predominate to the west of the Yenisei River, and highlands predominate to the east (Fig. 18). Russia is different in its relief, degree of human settlement and economic development.
The East European (Russian) Plain has an area of about 4 million km 2, and its average height is 150 m. This rolling plain, with alternating lowlands and uplands.
The area of the West Siberian Plain is about 3 million km2. The average height is 120 m. The West Siberian Plain is one of the world's largest lowlands. Only a few parts of it reach heights of 200 m.
Using the atlas map, determine how these plains differ in terms of: population density, level of development, prevailing types of economy.
The Central Siberian Plateau is also large in size - 3.5 million km 2. It, although it is considered a plain, is strongly elevated. Its average heights are from 500 to 700 m, and the highest parts - the Yenisei Ridge and the Putorana Plateau - rise to more than 1000 m.
Rice. 19. Mountain belts and plains of Russia.
The mountains on the territory of Russia, they are confined to mobile sections of the earth's crust and extend in several narrow strips (Fig. 19). They also differ greatly not only in height, but also in geographical location and natural conditions.
In the European part of the country, mountains from the south and east border the historical cradle of Russia - the Russian Plain. This neighborhood was reflected in the level of development of the Ural and Caucasus mountains. These are the most populated and developed mountain regions of the country.
In the Asian part of Russia, mountains occupy almost 70% of the territory. At the same time, more than a third of the mountainous regions are located at altitudes of more than 1000 m. population.
Questions and tasks
1. Using the maps of the textbook and the atlas, tell us about the placement of large landforms on the territory of our country.
2. What explains the diversity of the relief of Russia?
3. Compare the physical and tectonic maps and indicate: a) on which lithospheric plate all the largest plains of Russia are located; b) why mountains prevail in the eastern regions of the country.
4. Give examples of landforms of different sizes located in your area.
5. Compare in absolute heights, the degree of favorableness for people's lives and population density: the Caucasus and the Verkhoyansk Range, Altai and Dzhigdzhur.
§ 14. How and why the relief of Russia is changing
Relief formation is influenced by various processes. They can be combined into two groups: internal (endogenous) and external (exogenous).
internal processes. Among them, the latest (neotectonic) crustal movements, volcanism and earthquakes. Thus, under the influence internal processes formed the largest, large and medium forms relief.
Neotectonic refers to the movements of the earth's crust that have occurred in it over the past 30 million years. They can be both vertical and horizontal. On the formation of relief greatest influence have vertical movements as a result of which the earth's crust rises and falls (Fig. 20).
Rice. 20. Recent tectonic movements.
The speed and height of vertical neotectonic movements in some areas were very significant. Most of modern mountains on the territory of Russia exist only thanks to the latest vertical uplifts, since even young, relatively recently formed the mountains destroyed over several million years. Caucasus Mountains, despite the destructive impact external forces, were raised to a height of 4000 to 6000 m. Ural by 200-600 m, Altai - by 1000-2000 m. depressions of the seas and lakes, many lowlands.
According to fig. 20 determine what types of movements prevail on the territory of Russia.
Movements of the earth's crust are still taking place. The Greater Caucasus Range continues to rise at a rate of 8-14 mm per year. The Central Russian Upland grows somewhat more slowly - about 6 mm per year. And the territories of Tatarstan and the Vladimir region annually fall by 4-8 mm.
Along with the slow movements of the earth's crust in the formation of large and medium landforms certain role earthquakes and volcanism play.
Earthquakes often lead to significant both vertical and horizontal displacements of rock layers, the occurrence of collapses and failures.
Volcanic eruptions form such specific landforms as volcanic cones, lava sheets and lava plateaus.
External processes, forming modern relief, associated with the activity of the seas, flowing waters, glaciers, vefa. Under their influence, large landforms are destroyed and medium and small landforms are formed.
With the onset of the seas, sedimentary rocks are deposited in horizontal layers. Therefore, many coastal parts of the plains, from which the sea has receded relatively recently, have a flat relief. Thus, the Caspian and the north of the West Siberian lowland were formed.
flowing waters(rivers, streams, temporary water streams) erodes the earth's surface. As a result of their destructive activity, relief forms are formed, called erosional. These are river valleys, beams, ravines.
The valleys of large rivers are wide. For example, the Ob valley in its lower reaches is 160 km wide. Amur is slightly inferior to it - 150 km and Lena - 120 km. River valleys - traditional place resettlement of people, conducting special types farms ( animal husbandry in floodplain meadows, horticulture).
Ravines are a real disaster for agriculture (Fig. 21). By breaking the fields into small sections, they make it difficult to process them. In Russia, there are more than 400 thousand large ravines with with total area 500 thousand hectares.
Glacier activity. In the Quaternary period, due to the cooling of the climate, several ancient ice sheets arose in many regions of the Earth. In some areas - the centers of glaciation - ice has been accumulating for thousands of years. In Eurasia, such centers were the tori of Scandinavia, the Polar Urals, the Putorana Plateau in the north of the Central Siberian Plateau, and the Byrranga Mountains on the Taimyr Peninsula (Fig. 22).
Using the population map in the atlas, compare the population density in the valleys of large Siberian rivers and in the surrounding territories.
The ice thickness in some of them reached 3000 m. Under the influence of its own weight, the glacier slid southward to the adjacent territories. Where the glacier passed earth's surface changed a lot. In places he smoothed it out. In some places, on the contrary, he plowed out depressions. Ice polished the rocks, leaving deep scratches on them. Accumulations of huge stones (boulders), sand, clay, and rubble moved along with the ice. This mixture of various rocks is called moraine. In the southern, warmer regions, the glacier melted. The moraine, which he carried with him, was deposited in the form of numerous hills, ridges, flat plains.
wind activity. The wind forms the relief mainly in arid regions and where sands lie on the surface. Under its influence, dunes, sand hills and ridges are formed. They are common in the Caspian lowland, in Kaliningrad region(Curonian Spit).
Fig.22. The boundaries of the ancient glaciation
Questions and tasks
1. What processes influence the formation of the Earth's relief at the present time? Describe them.
2. What glacial landforms are found in your area?
3. What landforms are called erosional? Give examples of erosional landforms in your area.
4. What modern relief o Forming processes are typical for your area?
§ 15. Natural natural phenomena in the lithosphere
Not all processes occurring in the lithosphere proceed slowly. Many of them are catastrophic and are accompanied by significant destruction, and sometimes human casualties. Since these processes are not subject to human influence, they are called spontaneous. These include earthquakes and volcanic eruptions, mudflows, landslides and landslides. Natural phenomena, like all other processes in lithosphere, arise under the influence of internal and external forces.
In those areas where crustal movements especially intense, they are often accompanied by earthquakes and volcanism (Fig. 24). Such areas occupy about 20% of the territory of Russia.
Strong earthquakes in Russia occur on Caucasus, Kamchatka and the Kuriles, in the mountains of the Baikal region. In 1995, as a result of a strong earthquake (about 8 on the Richter scale) in the north of Sakhalin Island, the oilmen's village of Neftegorsk was literally wiped off the face of the earth in a matter of minutes. Thousands of people suffered. The destruction was so great that it was decided not to rebuild the village on this site.
Far East It is also known for underwater earthquakes that generate waves of enormous destructive power - tsunamis. Their speed can reach 1000 km / h, and the height near the coast - 50 m or more. In 1952, the tsunami that hit the Northern Kuriles caused significant damage and loss of life.
Active volcanoes in Russia are now located only in Kamchatka and the Kuril Islands. There are about sixty of them. But there are extinct volcanoes in the Caucasus (Elbrus, Kazbek), and in the mountains - Siberia, and the Far East.
Rice. 24. Seismically active regions of Russia
The largest active volcano in Russia is Klyuchevskaya Sopka. Its cone rises to 4750 m. The main crater of the volcano with a diameter of 500 m is located at the top. But in its lower part there are more than 60 small lateral cones and craters. Klyuchevskaya Sopka erupts quite often - about 1 time in 7 years. - during eruptions, a huge column of ash and gas is thrown into the atmosphere, and lava pours out of the crater. The roar of the eruption can be heard within a radius of 200-300 km.
Landslides most often occur in the mountains. Under the influence of gravity, huge masses of rocks break away from the slopes and fall down. Causes of collapses are different: tremors, activity of surface or ground waters.
No less dangerous are the streams of stones and mud - mudflows. They are formed in mountain rivers with a sharp rise in the water level associated with heavy precipitation, rapid melting of snow or ice.
If the impervious layer lies shallow, the layers of rocks that lie above it are saturated with water and begin to slide over the impervious layer (Fig. 25). This phenomenon is called a landslide. Landslides occur both on the plains and in the mountains: on the steep banks of rivers, lakes and reservoirs.
Determine from the map seismically active areas our country. Remember how the power of earthquakes is measured, which earthquakes in terms of power cause the greatest destruction.
Questions and tasks
1. What processes taking place in our time testify to the continuous development of the relief?
2. In what areas of our country does the activity of flowing waters especially affect the relief, and in which - the activity of the wind?
3. What natural phenomena are associated with the lithosphere?
4. What measures should be taken to deal with natural phenomena?
§ 16. Man and the lithosphere
Does the earth's crust affect the life and economic activity of people? Undoubtedly! A variety of minerals are located in the bowels of the earth (Fig. 26).
Minerals - mineral formations of the earth's crust, which are used in the economy.
On the map of the atlas, find the largest coal basins in Russia, oil and gas fields.
Minerals are distributed unevenly in the earth's crust, but there are certain patterns in their distribution. Sedimentary minerals have formed in the sedimentary cover of the platforms. Ore minerals predominate in the foundations of the platforms and in the mountains. Thus, differences in structure of the earth's crust largely determine the characteristics of the economy separate territories. Accumulations of minerals form deposits, and large accumulations form basins.
Table 6
Types of minerals
Table 7
Give other reasons for the settlement of people mainly on the plains.
The surface of the earth's crust- this is a place for the human population and a springboard for its activities. First of all, the absolute heights affect the placement and life of people (Table 7).
Harder to assess impact relief but on the life and traditions of people, their history. Nevertheless, such attempts have been made. For example, in the works of the famous Russian historian S. M. Solovyov, one can find arguments that make it possible to build the following scheme.
Life and management in the mountains are determined by the diversity of natural conditions inherent in mountainous regions.
Although Russia is a flat country, the influence of mountains on the economy and the life of people in it is very great. This is not surprising since almost half of the subjects Russian Federation has on its territory the mountains.
Human life in the mountains takes place in difficult, sometimes extreme conditions. This is due to significant absolute heights, difficult terrain and climate. Therefore, the mountains are distinguished by a weaker development of the territory compared to the plains.
Mountains have a peculiar barrier role. It manifests itself both in nature and in human life. The mountains create a natural barrier not only in the way of rivers and air masses. They also impede the movement of people, making it difficult for them to penetrate into new areas, contacts between carriers of mountain and flat territories. But as the technical capabilities of man grow, the development of modern means, this feature of the mountains weakens.
For example, the route of one of the largest railways in Russia - the Baikal-Amur Mainline - crosses 7 high ridges (Baikal, Bureinsky, Kadar, etc.). To overcome them, the ridges were “permeated” with tunnels.
Due to difficult natural conditions, from an economic point of view, the mountains cannot compete with the plains. Therefore, in mountainous regions, the number of types of economic activity is limited. They mainly use special resources associated with the mountainous position: mineral, recreational, hydropower, sometimes rare mountain plants.
The Tyrnyauz metallurgical plant was built in the Caucasus Mountains. Molybdenum and tungsten are mined here. Ore is mined with underground explosions. Then she descends through tunnels cut into the rocks to a special platform. Here it is crushed into powder and fed through pipes to the processing plant. Due to the limited space, waste rock is placed on the slopes of the mountains. This creates the danger of collapses, screes, rockfalls, and in case of heavy rains - mudflows.
But the mountains are gradually acquiring new functions: production, sports, wellness. Even high absolute heights are attractive for lovers of mountaineering, skiing, and adventure tourism.
Economic activity in the mountains is connected altitudinal zonality and variety of landscapes. For example, due to the harsh natural conditions in the mountainous regions of the Asian part of Russia Agriculture limited by seasonal migrations of animals.
In addition, the mountains are multinational regions. Due to the relative inaccessibility, the mountains served as a refuge for the population, forced by various circumstances (political, economic, etc.) to change their place of residence.
In large mountainous regions with high ridges, the population settled in deep and narrow intermountain valleys. Contacts between neighbors were difficult. Therefore, the mountains, as a rule, are characterized by great ethnic diversity. They live in minorities with a specific culture, way of life and features of the economy. More than 40 nationalities live in the North Caucasus. For example, in the Republic of Dagestan there are only 12 official languages, and the number of language dialects is in the tens.
Important social problem The development of mountainous regions lies in the fact that the main consumers of their resources are located on the plains, that is, at a considerable distance from the mountains. Mastering the mountains, you need to remember about negative aspects this process - the degradation of nature, the destruction of cultural and ethnic traditions, etc.
However, not only lithosphere has an effect on the person. The person also affects it. And this impact is multifaceted. The modern technical capabilities of mankind have become so grandiose that, as the great Russian scientist V. I. Vernadsky noted, “man has become a major geological force.”
Disturbances of the lithosphere associated with human economic activity are very diverse. First of all, the structure of the upper part of the lithosphere changes, the occurrence of rock layers. This happens during the extraction of minerals, the construction of quarries, mines, tunnels, other underground communications, and underground nuclear explosions.
Every year, hundreds of millions of tons of various minerals are extracted from the bowels of the earth. At the same time, only mining waste exceeds 3 billion tons per year. In place of the extracted rocks, voids are formed in the lithosphere. Only a part of them is filled or laid, so the total volume of such voids is constantly growing. Their presence leads to the failure of soils, disruption of the normal movement of groundwater. Violates the lithosphere and drilling, which has taken on a huge scale. About 3 million of them have been drilled in Western Siberia alone. The pumping of oil and gas from the depths of the earth increases the mobility of the earth's layers and leads to the occurrence of numerous man-made earthquakes! So, in the region of the largest oil fields Volga region for only 15 recent years More than 200 such earthquakes have been recorded.
Secondly, the surface of the lithosphere changes. It is leveled, small and large depressions (channels, ditches, pits) or embankments (rock heaps, terraces on mountain slopes) are created in it.
So now relief is formed not only by external and internal forces of nature, but also by man (Fig. 27).
Landforms created in the course of human economic activity are called anthropogenic relief.
Thirdly, in the course of their economic activity, a person creates artificial landforms: buildings, towers, dams, bridges. They are just like natural forms relief, change the surface of the lithosphere, affect the movement and temperature of air, runoff surface water etc.
Rice. 27. Types of anthropogenic relief
Tell us about the impact of artificial<|юрм рельефа на различные природные процессы.
This impact is constantly growing as artificial landforms become more and more numerous (Table 8). Their influence is especially significant in the largest cities. For example, summer temperatures in the largest cities of Russia (Moscow, St. Petersburg, Nizhny Novgorod) are the same as in the territories located 200-300 km to the south. For example, in Moscow, with its area of 1000 km2, the total area of artificial landforms is 300 km2. There are practically no large areas of the natural earth's surface left in the city.
Table 8
Growth of the surface of artificial landforms
In many countries of the world, including Russia, huge zones of almost continuous development have formed, stretching for hundreds of kilometers.
Questions and tasks
1. List the features of economic activity in the mountains.
2. Give examples of anthropogenic relief in your area.
Final tasks on the topic
1. What determines the placement of minerals? Name and show on the map the main basins and deposits.
2. How does relief affect human life and economic activity? Give examples of human influence on the lithosphere in our country.
3. Prove that the process of relief formation continues in our time.
4. Make a comparative description of the relief, geological structure and minerals of the Russian and West Siberian Plains using the following plan:
1) where the territory is located;
2) to which tectonic structure it is confined;
3) rocks of what age compose the territory;
4) average, minimum and maximum heights of the territory;
5) what external processes have participated and are participating in the formation of the relief;
6) what landforms are created by this or that process, their placement;
7) what natural phenomena are associated with the tectonic and geological structure, with the features of the relief, possible measures to combat them.
5. Make a description of any of the mountain ranges of Russia, located in the south of Siberia, using the plan above.
6. Give a description of the relief of your region (territory, republic).
7. Give an assessment of the mineral resource base of Russia.
8. Prove the validity of the statement of V. I. Vernadsky: "Man has become a major geological force."
Geography of Russia: Nature. Population. Economy. 8 cells : studies. for 8 cells. general education institutions / V. P. Dronov, I. I. Barinova, V. Ya. Rom, A. A. Lobzhanidze; ed. V. P. Dronova. - 10th ed., stereotype. - M. : Bustard, 2009. - 271 p. : ill., maps.
