How are the plains depicted in physical map? Tell me about a plain that you know well.
1. Flat and hilly plains. Most the globe occupy the plains. Large areas of flat or hilly land separate sections which differ in height are called plains.
Imagine a flat, treeless steppe covered with grassy vegetation. On such a plain, the horizon is visible from all sides and has a rectilinear outline of the boundaries. This is a flat plain.
Eurasia between the rivers Yenisei and Lena is located Central Siberian plateau. Plateaus also occupy most of Africa.
The second type of plains is hilly plains. The relief of the hilly plains is very complex. Here there are separate hills and hills, ravines and depressions.
The surface of plains usually slopes in one direction. The direction of the flow of the rivers corresponds to this slope. The slope of the plain is clearly visible on the plan and on the map. The plains are the most suitable for economic activity person. Most of the settlements are located on the plains. Flat areas are convenient for agriculture, for the construction of transport routes, industrial buildings. Therefore, man has mastered flat areas since ancient times. At present, the overwhelming majority of the peoples of the globe inhabit flat places.
2. According to the absolute height, three types of plains are distinguished (Fig. 43). Plains with a height of up to 200 m above sea level are called lowlands. On the physical map of the lowlands are depicted in green. The lowlands located near the coast of the sea are lower than its level. These include Caspian lowland in the west of our country. The largest lowland in the world is the Amazonian South America.
Rice. 43. Differences of plains in height.
Plains with an absolute height of 200 m to 500 m are called hills (for example, a hill Ustyurt between the Caspian and Aral seas). On physical maps, hills are shown in yellowish color.
Plains with a height of more than 500 m are plateaus. Plateaus on the map are shown in brown.
3. Formation of plains. Plains are divided into several types according to the method of formation. Plains that have been formed as a result of exposure and uplift of the seabed are called primary plains. These plains include the Caspian lowland.
On the globe there are plains formed from river sediments and sediments. On such plains, the thickness of sedimentary rocks, consisting of pebbles, sand, clay, sometimes reaches several hundred meters. These plains are La Plata along the Parana River in South America, in Asia - Great China Plain, Indo-Gangetic And Mesopotage. At the same time, there are plains on the earth's surface formed as a result of the long-term destruction of mountains. Such plains consist of folded layers of hard rocks. Therefore, they are hilly. Examples of rolling plains include the East European Plain And Saryarka plain.
Some plains are formed by lava flows poured onto the earth's surface. In this case, there is a kind of leveling of the existing irregularities. These plains include the following plateaus: Central Siberian, Western Australian, Deccan.
4. Changing the plains. On the plains, slow oscillatory movements are observed due to the influence of internal forces.
Plains undergo various changes under the influence of external forces. Looking at a physical map, you will see how the surface of the earth is indented by rivers and their tributaries. River water, washing away the banks and the sole, forms a valley. Since the lowland rivers flow meandering, they form wide valleys. The greater the slope, the more rivers cut into the surface of the Earth and change its topography.
spring melt water and the waters of heavy rains create temporary surface currents (streams) that form ravines and ditches. Usually ravines are formed on small slopes of hills that are not fastened by plant roots. If you do not take action on ichus in time
friction, then the ravines, branching, grow. This can cause great damage to the economy: fields, arable land, gardens, roads, various buildings. To stop the growth of ravines, they are covered with peat, rubble, stones. The bottom and slopes are covered with peat, which creates conditions for the growth of vegetation.
The moat, like the ravine, is an elongated depression. The only difference is that the moat has gentle slopes. Its bottom and slopes are covered with grass and shrubs.
The plains also change under the influence of the wind. The wind destroys solid rocks and carries away their particles. In deserts, steppes, on arable lands and on the shores of the seas, the effect of the wind is very noticeable. On the coasts of the seas or large lakes, you can see sand ridges formed by waves. The wind blowing from the sea surface easily carries away dry sand from the shores. The grains of sand are moved by the wind until they encounter some kind of obstacle (bush, stone, etc.). Sand, accumulating in this place, gradually takes the form of elongated mounds, on the side where the wind blows, the slopes are gentle, and on the other - steeper. The two lower edges of the mound are elongated and gradually decrease, therefore, they acquire a crescent shape. Such sandy hills are called dunes.
The height of the dunes, depending on the amount of sand and the strength of the wind, reaches from 20-30 m to 50-100 m. The wind, blowing sand grains from the slopes, shifts them towards the slope. Due to this, they are constantly moving forward.
Large dunes, moving from 1 m to 20 m a year, gradually change the terrain, and small dunes move up to 2-3 m per day during a strong storm. Moving dunes cover forests, gardens, fields, settlements.
Sandy hills in the desert are called dunes (Fig. 44). If the dunes are formed by the accumulation of sand brought by the waters of the oceans, seas and rivers, then the dunes arise from the sand during the weathering of local rocks. In our country, dunes are common in the Northern Aral Sea region, in the Kyzylkum, the Caspian lowland, and in the Southern Balkhash region. The height of dunes usually reaches 15-20 m, and in the largest deserts of the globe - the Sahara, Central Asia, Australia - up to 100-120 m.
Rice. 44. Dunes.
The dunes, like the dunes, are moved by the wind. Small dunes move up to 100-200 m per year, and large ones - up to 30-40 m per year. In most cases, the person himself contributes to the movement of sand. Sandy hills turn into wandering sands as a result of deforestation, overgrazing on pastures.
To stop the movement of dunes and dunes, drought-resistant shrubs and plants are planted on their gentle slopes. Trees are planted in the hollows between the hills.
1. What is called the plains? What types of plains exist?
2. How do the plains differ in height?
3. On the physical map, find all the plains named in the text.
4. If your area is flat, describe the topography of the land. By height and relief, determine what type of plains it belongs to. Learn from adults how your area is used for economic purposes?
5. What forces and how do they affect the change in the relief of the plains? Justify your answer with specific examples.
6. Why running water can not wash the soil of the slopes with vegetation?
7*. In what parts of the territory of Kazakhstan is sandy relief common and why?
It is characterized by a predominantly flat landscape, prevailing over the mountain landscape, not only on land, but also under water.
What are plains?
Plains are relatively flat, vast areas in which the heights of neighboring areas fluctuate within 200 m, they have a slight slope (no more than 5 m). Most case in point The West Siberian Lowland is a classic plain: it has an exceptionally flat surface, the elevation difference on which is almost imperceptible.
Relief features
As we already understood from the above definition, plains are terrain with a flat and almost even relief, without noticeable ups and downs, or hilly, with a smooth alternation of surface elevations and depressions.
Flat plains are mostly insignificant in size. They are located near the seas and big rivers. Hilly plains with uneven terrain are more common. For example, the relief of the East European (Russian) Plain is characterized by the presence of both hills over 300 meters high and depressions, whose height is below sea level (Caspian lowland). Other famous plains of the world are Amazonian, Mississippi. They have a similar topography.
Plains Features
A distinctive feature of all plains is a clearly defined, clearly visible horizon line, which can be straight or undulating, which is determined by the relief of a particular area.
People from ancient times preferred to create settlements on the plains. Since these places are rich in forests and fertile soil. Therefore, today the plains are still the most densely populated. Most of the minerals are mined in the plains.
Considering that the plains are an area with a huge area and a large extent, they are characterized by a variety of natural areas. So, on the East European Plain there are territories with mixed and broad-leaved forests, tundra and taiga, steppe and semi-desert. The plains of Australia are represented by savannas, and the Amazonian lowland by selva.
Climatic features
The climate of the plain is a fairly broad concept, since it is determined by many factors. These are geographical location, climatic zone, area of the region, length, relative proximity to the ocean. In general, the flat terrain is characterized by a clear change of seasons due to the movement of cyclones. Often on their territory there is an abundance of rivers and lakes, which also affect climatic conditions. Some plains have their vast area consisting of the continuous desert of the Western Plateau of Australia).
Plains and mountains: what is their difference
Unlike plains, mountains are tracts of land that rise sharply above the adjacent surface. They are characterized by significant fluctuations in heights and large slopes of the relief. But small areas flat terrain are also found in the mountains, between mountain ranges. They are called intermountain basins.
Plains and mountains are landforms whose differences are based on their origin. Most of the mountains were formed under the influence of tectonic processes, the movement of layers that occurs deep in the earth's crust. In turn, the plains lie mainly on platforms - stable areas earth's crust, they were influenced by external forces of the Earth.
Among the differences between mountains and plains, in addition to appearance and origin, we can distinguish:
- maximum height (in the plains it reaches 500 m, in the mountains - over 8 km);
- area (the area of mountains on the entire surface of the Earth is significantly inferior to the area of plains);
- the probability of earthquakes (on the plains it is practically zero);
- degree of development;
- ways of human use.
major plains
Located in South America, it is the largest in the world, its area is about 5.2 million square meters. km. It has a low population density. It is characterized by a hot and humid climate, dense tropical forests, occupying vast areas and teeming with animals, birds, insects and amphibians. Many animal species of the Amazonian lowland are not found anywhere else.
The East European (Russian) Plain is located in the eastern part of Europe, its area is 3.9 million square kilometers. km. Most of the plains are in Russia. It has a gently sloping relief. Here is the bulk major cities, as well as a significant share of the country's natural wealth.
located in Eastern Siberia. Its area is about 3.5 million square meters. km. A feature of the plateau is the alternation of mountain ranges and wide plateaus, as well as the frequent permafrost, the depth of which reaches 1.5 km. The climate is sharply continental, the vegetation is dominated by deciduous forests. The plain is rich in minerals and has an extensive river basin.
Plains of the plains
areas of the land surface, the bottom of the oceans and seas, characterized by slight fluctuations in altitude. On land, plains are distinguished below sea level, low-lying (altitude up to 200 m), elevated (from 200 to 500 m) and upland (above 500 m). According to the structural principle, the plains of the platform and orogenic (mountain) regions are distinguished (mainly within the intermountain and foothill troughs); according to the predominance of certain external processes - denudation, formed as a result of the destruction of elevated landforms, and accumulative, arising from the accumulation of layers of loose deposits. Collectively, plains cover most of the Earth's surface. The greatest plain in the world is the Amazonian (over 5 million km 2).
PLAINSPLAINS, areas of the land surface, the bottom of the oceans and seas, characterized by slight fluctuations in altitude. On land, there are plains lying below sea level. (cm. SEA LEVEL), low-lying (height up to 200 m), elevated (from 200 to 500 m) and upland (above 500 m). According to the structural principle, the plains of the platform and orogenic (mountain) regions are distinguished (mainly within the intermountain and foothill troughs); according to the predominance of certain external processes - denudation, formed as a result of the destruction of elevated landforms, and accumulative, arising from the accumulation of layers of loose deposits. Collectively, plains cover most of the Earth's surface. The greatest plain in the world is the Amazonian (over 5 million km 2).
* * *
Plains, vast, fairly flat areas of the earth's surface. They occupy 15-20% of the land. Altitude fluctuations within them do not exceed 200 m, and slopes are less than 5 °. The plains are one of essential elements relief of both land and the bottom of the seas and oceans.
Types of land plains
Numerous types of plains are distinguished by the nature and height of the surface, geological structure, origin and development history.
Depending on the appearance and size of irregularities, they distinguish: flat, wavy, ridge, stepped and other plains.
According to the shape of the surface, they are distinguished: horizontal (Great Plain of China (cm. GREAT CHINA PLAIN)), inclined (mainly foothills) and concave (plains of intermountain depressions - the Tsaidam basin (cm. TsAYDAM BELL)) plains.
The classification of plains by height relative to sea level is widespread. Negative plains are located below sea level, often in deserts, for example, the Qattara depression (cm. KATTARA) or the lowest place on land - the Ghor depression (cm. GHOR)(up to 395 m below sea level). The low plains, or lowlands (heights from 0 to 200 m above sea level), include greatest plains world: Amazonian lowland (cm. AMAZON LOWLAND), The East European Plain (cm. THE EAST EUROPEAN PLAIN) And West Siberian Plain (cm. WEST SIBERIAN PLAIN). The surface of elevated plains, or hills, is located in the altitude range of 200-500 m (Central Russian Upland (cm. CENTRAL RUSSIAN HIGHLIGHT), Valdai Upland (cm. Valdai hill)). Upland plains rise above 500 m, for example, one of the largest in Central Asia - the Gobi (cm. GOBI (band of deserts and semi-deserts in Mongolia)). Both elevated and upland plains with a flat or undulating surface, separated by slopes or ledges from lower neighboring territories, the term plateau is often used. (cm. PLATEAU).
The role of external processes
The appearance of the plain depends largely on external processes. By the sum of the impact of external processes, the plains are divided into accumulative and denudation. Accumulative plains formed during the accumulation of strata of loose sediments (see accumulation (cm. ACCUMULATION)), are river (alluvial), lake, sea, ash, glacial, water-glacial, etc. For example, the thickness of sediments, mainly river and sea, on the Flanders lowland (coast North Sea) reaches 600 m, and the thickness of silty rocks (loesses ( cm. LESS)) on the Loess Plateau (cm. LESS PLATEAU)- 250-300 m. Accumulative plains also include volcanic plateaus composed of hardened lavas and loose products of volcanic eruptions (Dariganga plateau in Mongolia, Columbian plateau (cm. COLOMBIA PLATEAU) in North America).
Denudation plains arose as a result of the destruction of ancient hills or mountains and removal by water, wind, etc. (see denudation (cm. DENUDATION)) of the resulting material. Depending on the prevailing process, due to which the destruction of the ancient relief and the leveling of the surface occurred, erosional (with the predominance of the activity of flowing waters), abrasion (created by wave processes on the sea coasts), deflationary (leveled by wind) and other denudation plains are distinguished. Many plains have a complex origin, as they were shaped by various processes. Depending on the mechanism of formation, the following are distinguished among the denudation plains: penepleny - in this case, the removal and demolition of material occurred more or less evenly from the entire surface of the ancient mountains, for example, the Kazakh upland (cm. KAZAKH SMALL-SOPOCHNIK) or syrts of the Tien Shan; pediplains arising from the destruction of a previously elevated relief, which begins from the outskirts (many plains at the foot of the mountains, mainly the deserts and savannas of Africa, etc.).
The role of internal processes
The participation of tectonic processes in the formation of plains can be both passive and active. With passive participation, the main role in the formation of structural plains is played by a fairly even - horizontal or inclined (monocline) - occurrence of rock layers (see Turgai Plateau (cm. TURGAI PLATEAU)). Many structural plains are simultaneously accumulative, for example, the Caspian lowland (cm. CASPIAN LOWLAND), North German Plain (cm. NORTH GERMAN LOWLAND). With the predominance of denudation in the formation of structural plains, layered plains are distinguished (Swabian-Franconian Jura (cm. Swabian-Franconian Jura)). The basement plains worked out in the dislocated rocks(Lake plateau in Finland).
In the course of intermittent tectonic uplifts, followed by a period of rest, sufficient for the destruction and leveling of the relief, layered plains are formed, for example, the Great Plains (cm. GREAT PLAINS).
Geological principle of typification
Platform plains are formed in areas of relatively calm tectonic and magmatic activity. These include most of the plains, including the largest ones. Plains of orogenic regions (see orogen (cm. ORogen)) are characterized by intense activity of the earth's interior. These are the plains of intermountain basins (Fergana Valley (cm. FERGANA VALLEY)) and foothill troughs (Podolsk Upland (cm. PODILSKY HIGHLIGHT)). Sometimes the plains are considered parts of the so-called lowland countries - vast spaces where small areas with highly dissected relief are found (for example, the Zhiguli (cm. ZHIGULI) on the Russian plain (cm. RUSSIAN PLAIN)- flat country).
Land plains are the most favorable for comprehensive development by man. They are home to the majority of the world's population. Here are concentrated the largest tracts of forests and arable land with the most fertile soils, full-flowing rivers flow and large lakes are located. On the accumulative plains, oil, gas, coal, salts and other minerals are being extracted. However, part of the plains is characterized by an arid climate, they are occupied giant deserts- Kyzylkum (cm. KYZILKUM) and the Karakum on the Turan lowland (cm. TURAN LOWLAND), Great Sandy Desert (cm. GREAT SANDY DESERT) and the Great Victoria Desert (cm. GREAT VICTORIA DESERT) on the Western Plateau of Australia, etc.
Types of underwater plains
Among the underwater plains, two types are most common: continental shallows and deep-sea abyssal plains. (cm. ABYSSAL PLAINS). Continental shelf, or shelf (cm. SHELF), usually extends from the coast to depths of 200 m and occupies the underwater margin of the continents (cm. UNDERWATER MATERIAL). The most extensive shoals, more than 1000 km wide, are located on the northern outskirts of Eurasia and North America. Deep-water abyssal plains (wavy, flat, hilly) occupy huge basins - the ocean bed and the transition zone depressions (cm. TRANSITION ZONE) at depths of 3000-7000 m. Abyssal plains are especially numerous in Atlantic Ocean; the largest of them are the Som and Demerera plains (cm. DEMERARA).
encyclopedic Dictionary . 2009 .
See what "plains" are in other dictionaries:
Areas of the land surface, the bottom of the oceans and seas, characterized by slight fluctuations in altitude. On land, plains are distinguished below sea level, low-lying (altitude up to 200 m), elevated (from 200 to 500 m) and upland (above 500 m). By… … Big Encyclopedic Dictionary
Rivers differ from highlands in that they are at a low altitude above sea level. It can be approximately assumed that the plains are below 150 soots. or 300 m., or 1000 rus. ft. above sea level, and the highlands are higher. Similar to what has already been seen…… Encyclopedia of Brockhaus and Efron
PLAINS, areas of the land surface, the bottom of the oceans and seas, characterized by small slopes and slight fluctuations in heights. On land, there are plains lying below sea level, low-lying (height up to 200 m), elevated (200-500 m) and upland ... ... Modern Encyclopedia
Rivers differ from uplands (see) in that they are at a low altitude above sea level. It can be approximately assumed that the plains are below 150 soots. or 300 m, or 1000 rus. ft. above sea level, and the highlands are higher. Like what already... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Areas of the land surface, the bottom of the oceans and seas, characterized by insignificant. height fluctuations. On land, R. are distinguished, lying below ur. m., low-lying (height up to 200 m), elevated (from 200 to 500 m) and upland (above 500 m). According to the structural principle ... ... Natural science. encyclopedic Dictionary
Plains- Plains, in: Great Plains (plateau) ... Russian spelling dictionary
- (English Sto Plains) a fictional area in the series of books "The Flat World" by Terry Pratchett. Content 1 general characteristics 2 Cities and countries of the plain Sto 2.1 Sto Lat ... Wikipedia
Lichkov, 1935, vast plains that arise during the era of the existence of high-water streams fed by melting glaciers (for example, Polesie, Meshcherskaya lowland, etc.). Like the great accumulative plains, they are confined to the tect. deflections. The term... ... Geological Encyclopedia
Plains- vast areas of the earth's surface with small (up to 200 m) elevation fluctuations and slight slopes.
Plains occupy 64% of the land area. In tectonic terms, they correspond to more or less stable platforms that have not shown significant activity in recent times, regardless of their age - they are ancient or young. Most of the plains on land are located on ancient platforms (42%).
According to the absolute and height of the surface, plains are distinguished negative-
lying below the level of the World Ocean (Caspian), base- from 0 to 200 m in height (Amazonian, Black Sea, Indo-Gangetic lowlands, etc.), sublime- from 200 to 500 m (Central Russian, Valdai, Volga Uplands, etc.). Plains also include plateau (high plains), which, as a rule, are located above 500 m and are separated from the adjacent plains by ledges (for example, the Great Plains in the USA, etc.). The height of the plains and plateaus determines the depth and degree of their dismemberment by river valleys, gullies and ravines: what
the higher the plain, the more intensely they are dissected.
In appearance, plains can be flat, wavy, hilly, stepped, and according to the general slope of the surface - horizontal, inclined, convex, concave.
Different appearance plains depends on their origin and internal structure, which largely depend on the direction of neotectonic movements. On this basis, all plains can be divided into two types - denudation and accumulative (see Scheme 14-A-1-1). Within the former, the processes of denudation of loose material predominate, within the latter, its accumulation.
It is quite obvious that denudation surfaces experienced ascending tectonic movements for most of their history. It is thanks to them that the processes of destruction and demolition - denudation - prevailed here. However, the duration of denudation can be different, and this is also reflected in the morphology of such surfaces.
With continuous or almost continuous slow (epeirogenic) tectonic uplift, which continued throughout the entire existence of the territories, there were no conditions for the accumulation of sediments on them. There was only a denudation cut of the surface by various exogenous agents, and if thin continental or marine sediments accumulated for a short time, then during subsequent uplifts they were carried outside the territory. Therefore, in the structure of such plains, an ancient plinth comes to the surface - folds cut by denudation, only slightly covered by a thin cover of Quaternary deposits. Such plains are called basement; it is easy to see that the basement plains in tectonic terms correspond to the shields of ancient platforms and the protrusions of the folded basement of young platforms. Basement plains on ancient platforms have a hilly relief, most often they are elevated. Such, for example, are the plains of Fennoscandia - the Kola Peninsula and Karelia. Similar plains are located in northern Canada. Basement hills are widespread in Africa. As a rule, long-term denudation cut off all the structural irregularities of the base, so such plains are astructural.
The plains on the "shields" of young platforms have a more "restless" hilly relief, with residual hill-type elevations, the formation of which is associated either with lithological features - more
hard stable rocks, or with structural conditions - former convex folds, microhorsts or exposed intrusions. Of course, all of them are structurally determined. This is how, for example, the Kazakh upland, partly the Gobi plains look like.
Plates of ancient and young platforms, which experience stable uplift only in the neotectonic stage of development, are composed of layers of sedimentary rocks. high power(hundreds of meters and a few kilometers) - limestone, dolomite, sandstone, siltstone, etc. Over millions of years, the sediments have hardened, become rocky and have become resistant to erosion. These rocks lie more or less horizontally, as they once were deposited. The uplift of territories during the neotectonic stage of development stimulated denudation on them, which made it impossible for young loose rocks to be deposited there. Plains on the plates of ancient and young platforms are called reservoir. From the surface, they are often covered with loose Quaternary continental deposits. low power, which practically do not affect their height and orographic features, but determine them appearance due to morphosculpture (East European, southern part of West Siberian, etc.).
Since the stratal plains are confined to the platform plates, they are pronounced structural - their macro- and even mesoforms of the relief are determined by the geological structures of the cover: the nature of the bedding of rocks of different hardness, their slope, etc.
During the Pliocene-Quaternary subsidence of territories, even if relative, they began to accumulate sediments carried from the surrounding areas. They filled in all the previous surface irregularities. So formed accumulative plains, composed of loose, Pliocene-Quaternary deposits. Usually these are low-lying plains, which sometimes lie even below sea level. According to the conditions of sedimentation, they are divided into marine and continental - alluvial, eolian, etc. An example of accumulative plains is the Caspian, Black Sea, Kolyma, Yano-Indigirskaya lowlands, composed of marine sediments, as well as Pripyat, Leno-Vilyui, La Plata and others. Accumulative plains , as a rule, are confined to syneclises.
In large basins among the mountains and at their foothills, the accumulative plains have a surface inclined from the mountains, cut by the valleys of many rivers flowing down from the mountains and complicated by their alluvial fans. They are difficult
loose continental sediments: alluvium, proluvium, deluvium, lacustrine sediments. For example, the Tarim Plain is composed of sands and loesses, the Dzungarian Plain is composed of thick sand accumulations brought from neighboring mountains. The ancient aluvial plain is the Karakum desert, composed of sands brought by rivers from the southern mountains in the pluvial epochs of the Pleistocene.
Plain morphostructures usually include ridges. These are linearly elongated hills with rounded outlines of peaks, usually no more than 500 m high. They are composed of dislocated rocks of different ages. An indispensable feature of the ridge is the presence of a linear orientation inherited from the structure of the folded area on the site of which the ridge arose, for example, Timansky, Donetsk, Yenisei.
It should be noted that all the listed types of plains (basement, stratal, accumulative), as well as plateaus, plateaus and ridges, according to I. P. Gerasimov and Yu. structure 1 .
Plains on land form two latitudinal series corresponding to the platforms of Laurasia and Gondwana. Northern range of plains formed within relatively stable limits modern times the ancient North American and East European platforms and the young epipaleozoic West Siberian platform - a plate that has experienced even a slight subsidence and is predominantly a low-lying plain expressed in relief.
The Central Siberian Plateau, and in the morphological and structural sense, these are high plains - a plateau, formed on the site of the ancient Siberian platform, activated in modern times due to resonant movements from the east, from the side of the active geosynclinal West Pacific belt. The so-called Central Siberian Plateau includes volcanic plateaus(Putorana and Siverma), tuff plateaus(Central Tunguska), trap plateaus(Tungusskoye, Vilyuiskoye), formation plateaus(Priangarskoe, Prilenskoe), etc.
Peculiar orographic and structural feature plains of the northern row: beyond the North
“Often, plateaus and plateaus are distinguished only by their appearance and degree of dissection, without taking into account their geological structure. Plateaus are considered less dissected landforms and are classified as high plains. Plateaus are usually higher, dissected in the marginal parts more intensely and deeper, therefore they are referred to as mountains.
the Arctic Circle is dominated by low coastal accumulative plains; to the south, along the so-called active 62 ° parallel, there is a strip of basement hills and even plateaus on the shields of ancient platforms - Laurentian, Baltic, Anabar; in middle latitudes along 50° N. sh. - again a strip of stratal and accumulative lowlands - North German, Polish, Polissya, Meshchera, Sredneobskaya, Vilyuyskaya.
On the East European Plain, Yu. A. Meshcheryakov also revealed another pattern: the alternation of lowlands and uplands. Since the movements on the East European Platform were of an undulating nature, and their source in the neotectonic stage was the collisions of the Alpine belt, he established several alternating bands of uplands and lowlands, fanning out from southwest to east and taking on an increasingly meridional direction as they move away from the Carpathians. . The Carpathian strip of uplands (Volynskaya, Podolskaya, Pridneprovskaya) is replaced by the Pripyat-Dnieper lowland strip (Pripyatskaya, Pridneprovskaya), then follows the Central Russian strip of uplands (Belarusian, Smolensk-Moscow, Central Russian); the latter is replaced successively by the Upper Volga-Don strip of lowlands (Meshcherskaya lowland, Oka-Donskaya plain), then by the Volga upland, Zavolzhskaya lowland and, finally, by the strip of Cis-Ural uplands.
In general, the plains of the northern row are inclined to the north, which is consistent with the course of the rivers.
Southern range of plains corresponds to the Gondvan platforms that have experienced activation in recent times. Therefore, within its limits, elevations predominate: layered (in the Sahara) and basement (in southern Africa), as well as plateaus (Arabia, Hindustan). Only within the limits of the inherited troughs and syneclises, stratal and accumulative plains were formed (the Amazonian and La Plata lowlands, the Congo depression, and the Central Lowland of Australia).
Generally largest areas among the plains on the continents belong layered plains, within which the primary plain surfaces are formed by horizontal layers of sedimentary rocks, and the socle and accumulative plains are of subordinate importance.
In conclusion, we emphasize once again that mountains and plains, as the main forms of relief on land, are created by internal processes: mountains gravitate towards mobile folded belts.
Lands, and plains - to platforms (Table 14). Relatively small, relatively short-lived landforms created by external exogenous
processes are superimposed
into large ones and give them a peculiar appearance. They will be discussed below.
Table 14
Areas of the main types of continent morphostructures (%)
Plains - areas of the land surface, the bottom of the oceans and seas, characterized by slight fluctuations in altitude (up to 200 m, slopes less than 5 °). According to the structural principle, the plains of the platform and orogenic (mountain) regions are distinguished (mainly within the intermountain and foothill troughs); according to the predominance of certain external processes - denudation, formed as a result of the destruction of elevated landforms, and accumulative, arising from the accumulation of layers of loose deposits. Together, the plains occupy most of the Earth's surface, 15-20% of the land. The greatest plain in the world is the Amazonian (over 5 million sq. km).
Numerous types of plains are distinguished by the nature and height of the surface, geological structure, origin and history of development. Depending on the appearance and size of irregularities, they distinguish: flat, wavy, ridge, stepped plains. According to the shape of the surface, horizontal plains (Great Chinese Plain), sloping plains (mainly foothills), concave plains (in intermountain depressions - the Tsaidam basin) are distinguished.
The classification of plains by height relative to sea level is widespread. Negative plains are located below sea level, often in deserts, for example, the Qattara depression or the lowest place on land - the Ghor depression (up to 395 m below sea level). The low plains, or lowlands (heights from 0 to 200 m above sea level), include the greatest plains in the world: Amazonian lowland, East European Plain and West Siberian Plain. The surface of elevated plains, or hills, is located in the altitude range of 200-500 m (Central Russian Upland, Valdai Upland). Upland plains rise above 500 m, for example, one of the largest in Central Asia - the Gobi. Both elevated and upland plains with a flat or undulating surface, separated by slopes or ledges from lower neighboring territories, the term plateau is often used.
The appearance of the plain depends largely on external processes. By the sum of the impact of external processes, the plains are divided into accumulative and denudation. Accumulative plains formed during the accumulation of strata of loose deposits (accumulation) are river (alluvial), lacustrine, marine, ash, glacial, water-glacial. For example, the thickness of sediments, mainly river and marine, on the Flanders Lowland (North Sea coast) reaches 600 m, and the thickness of silty rocks (loesses) on the Loess Plateau is 250-300 m. loose products of volcanic eruptions (Dariganga plateau in Mongolia, Columbian plateau in North America).
Denudation plains arose as a result of the destruction of ancient hills or mountains and the removal of water, wind (denudation) of the resulting material. Depending on the prevailing process, due to which the destruction of the ancient relief and the leveling of the surface occurred, erosional (with the predominance of the activity of flowing waters), abrasion (created by wave processes on the sea coasts), deflationary (leveled by wind) and other denudation plains are distinguished. Many plains have a complex origin, as they were shaped by various processes. Depending on the mechanism of formation, among the denudation plains, the following are distinguished: peneplens - in this case, the removal and demolition of material occurred more or less evenly from the entire surface of the ancient mountains, for example, the Kazakh upland or the Tien Shan syrts; pediplains arising from the destruction of a previously elevated relief, which begins from the outskirts (many plains at the foot of the mountains, mainly the deserts and savannas of Africa).
The participation of tectonic processes in the formation of plains can be both passive and active. With passive participation, the main role in the formation of structural plains is played by a fairly even - horizontal or inclined (monocline) - occurrence of rock layers (Turgai plateau). Many structural plains are simultaneously accumulative, such as the Caspian Lowland, the North German Lowland. With the predominance of denudation in the formation of structural plains, layered plains (Swabian-Franconian Jura) are distinguished. The socle plains worked out in dislocated rocks (Lake Plateau in Finland) differ from them. In the course of intermittent tectonic uplifts, followed by a period of rest, sufficient for the destruction and leveling of the relief, layered plains are formed, for example, the Great Plains.
Platform plains are formed in areas of relatively calm tectonic and magmatic activity. These include most of the plains, including the largest ones. The plains of the orogenic regions (see orogen) are distinguished by the intense activity of the earth's interior. These are the plains of intermountain basins (Fergana Valley) and foothill troughs (Podolsk Upland). Sometimes the plains are considered parts of the so-called flat countries - vast spaces where there are small areas with a highly dissected terrain (for example, the Zhiguli on the Russian Plain - a flat country).