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It is formed as a result of the interaction of internal (endogenous) and external (exogenous) forces. Endogenous and exogenous processes of relief formation operate constantly. In this case, endogenous processes mainly create the main features of the relief, while exogenous processes try to level the relief.

The main sources of energy during relief formation are:

1. Internal energy of the Earth;
2. Solar energy;
3. Gravity;
4. The influence of space.

Source of energy endogenous processes is the thermal energy of the Earth associated with processes occurring in the mantle (radioactive decay). Due to endogenous forces, the earth's crust was separated from the mantle with the formation of two types: continental and oceanic.

Endogenous forces cause: movements of the lithosphere, the formation of folds and faults, earthquakes and volcanism. All these movements are reflected in the relief and lead to the formation of mountains and troughs of the earth's crust.

Faults in the earth's crust distinguished by: size, shape and time of formation. Deep faults form large blocks of the earth's crust that experience vertical and horizontal displacements. Such faults often determine the outlines of continents.

Large blocks of the earth's crust are cut through a network of small faults. River valleys are often associated with them (for example, the Don River valley). The vertical movements of such blocks are always reflected in the relief. Particularly visible are the forms created by modern ( neotectonic) movements. Thus, in our Central Black Earth region, the area of ​​the Central Russian Upland (Belgorod, Voronezh, Kursk regions) is rising at a rate of 4-6 mm/year. At the same time, the Oka-Don lowland (Tambov, Lipetsk and north-eastern Voronezh regions) drops by 2 mm annually. Ancient movements of the earth's crust are usually reflected in the nature of the occurrence of rocks.

Exogenous processes associated with the supply of solar energy to the earth. But they proceed with the participation of gravity. This happens:

1. Weathering of rocks;
2. Movement of material under the influence of gravity (collapses, landslides, screes on slopes);
3. Transfer of material by water and wind.

Weathering is a set of processes of mechanical destruction and chemical change of rocks.

The total impact of all processes of destruction and transport of rocks is called denudation. Denudation leads to leveling of the surface of the lithosphere. If there were no endogenous processes on Earth, then it would have long ago had a completely flat surface. This surface is called main level of denudation.

In reality, there are many temporary levels of denudation at which leveling processes can fade for some time.

The manifestation of denudation processes depends on the composition of rocks, geological structure and climate. For example, the shape of ravines in sand is trough-shaped, and in chalk rocks it is V-shaped. However, the greatest importance for the development of denudation processes is the height of the area above sea level, or the distance to erosion basis.

Thus, the relief of the surface of the lithosphere is the result of the counteraction of endogenous and exogenous processes. The former create uneven terrain, and the latter smooth them out. During relief formation, endogenous or exogenous forces may predominate. In the first case, the height of the relief increases. This upward development of relief. In the second case, positive relief forms are destroyed and the depressions are filled. There is a decrease in surface heights and flattening of slopes. This downward development of relief.

Endogenous and exogenous forces are balanced over long geological time. However, in short periods of time, one of these forces predominates. The change of ascending and descending movements of the relief leads to cyclical processes. That is, first positive forms of relief are formed, then weathering of rocks occurs, material moves under the influence of gravity and water, which leads to leveling of the relief.

Such continuous movement and change of matter is the most important feature of the geographical envelope.

Literature.

1. Smolyaninov V. M. General geoscience: lithosphere, biosphere, geographical envelope. Educational manual / V.M. Smolyaninov, A. Ya. Nemykin. – Voronezh: Origins, 2010 – 193 p.

Each landform consists of relief elements. These include smooth surfaces and slopes, as well as lines that arise at the intersection of two surfaces (edge, sole, thalweg) and angles that arise at the intersection of three or more faces (top).

Landforms vary in different ways.

Based on the inclination of the earth's surface, there are subhorizontal surfaces with tilt angles up to 2° and slopes– more than 2°. Landforms can be closed(hill) and open(ravine), concave(funnel) and convex(barkhan), simple(trap) and complex(mountain range). Based on size, planetary forms, mega-, macro-, meso-, micro- and nano-relief forms are distinguished.

Planetary forms occupy areas of millions of square kilometers. These include: continents (in the geophysical sense), transition zones from continents to the ocean floor, the ocean floor and mid-ocean ridges. All of them differ in the structure of the earth’s crust, which served as a serious basis for identifying the listed forms as planetary.

Megaforms occupy areas of hundreds and tens of thousands of square kilometers. These are mountain belts (Caucasus), plateaus (Central Siberian), plains (West Siberian) within continents, basins and uplifts on the ocean floor, etc.

Macroforms have areas of hundreds and thousands of square kilometers. These are parts of megaforms: individual ridges and intermountain depressions in the mountains, highlands and lowlands in the plains.

Mesoforms occupy square kilometers and their first tens. These are ravines, ravines, moraine hills, dunes, etc.

Microforms– karst sinkholes, riverbed banks on the floodplain, etc.

Nanoforms– hummocks, erosion furrows, sand ripples on dunes, etc.

Planetary and large landforms were formed due to the internal forces of the Earth. Medium - mesoforms - and small forms are due to the action of exogenous processes: the work of surface flowing waters, the dissolving activity of water, glaciers, wind, etc. Exogenous processes also include a variety of ever-increasing human economic activities.

Academician I.P. Gerasimov, who headed the Institute of Geography of the USSR Academy of Sciences from 1951 to 1985, and Yu.A. Meshcheryakov proposed the principle of dividing all forms of the Earth's relief into three categories, differing in order of magnitude (size) and origin, taking into account the age of the relief (the beginning of its formation).

Geotextures (Greek ge- Earth, lat. tectura- cover) - the largest forms of the Earth's relief, caused by planetary geophysical and cosmic processes. Geotextures of the first rank include continental protrusions and oceanic depressions, geotectures of the second rank include the largest megaforms: flat-platform areas and mountain systems of various genesis on land, ocean basins and mid-ocean ridges in the ocean, and transition zones between continents and oceans. The formation of modern geotextures began at the turn of the Paleozoic and Mesozoic and coincides with the geomorphological stage of the Earth's development.

Morphological structures (Greek morphe- form, lat. structura- structure) - large relief forms - megaforms and macroforms, which arose as a result of the interaction of endogenous and exogenous processes with the leading, active role of internal processes - tectonic movements; their structure clearly reflects geological structures. The formation of morphostructures corresponds to the neotectonic stage of the Earth's development.

Morphosculptures (Greek morphe- form, lat. sculptura- sculpture, carving) are relatively small (meso-, micro-, etc.) forms of relief, owing their origin primarily to exogenous processes that are closely related to modern and past climatic conditions. The age of morphosculptures is mostly limited to the Quaternary period.

In genetic terms (not in size!) geotectures and morphostructures are characterized by relative commonality and are combined into the category morphotectonic relief, i.e., relief due to the active role of an endogenous factor. A generalized classification of morphotectonic relief forms (morphostructures) according to their structure, genesis and morphology is shown in Scheme 1. Morphotectonic relief can be contrasted morphosculptural (morphoclimatic) relief, which arose mainly under the influence of exogenous processes subject to the law of climatic zonation.

Combinations of relief forms that are similar in appearance, internal structure, origin and development conditions, naturally repeating in a certain territory, form morphogenetic types of relief(for example, hilly moraine plains, ridged valley-gully erosion plains, flat outwash plains, etc.).

For detailed geomorphological maps either individual relief forms or morphogenetic types of relief are depicted, and on the colored background of the latter, typical relief forms are marked with icons. On small-scale maps, morphostructure is shown with a colored background, and morphosculpture is shown with shading and icons (for example, in the Physiographic Atlas of the World).

2.2. Relief-forming processes

Exogenous processes occur on the surface of the Earth. Almost all of them are due to the energy of the Sun (except for slope ones, caused by gravitational energy) and occur with the help of various agents of relief formation - water, ice, wind, etc. Any manifestation of exogenous relief formation necessarily occurs against the background of gravity, which acts on the movement of material directly ( on slopes) and indirectly, through other exogenous processes. Therefore, gravity can also be included among the agents of relief formation. Anthropogenic processes are included in a special group of exogenous processes.

2.2.1. Internal (endogenous) processes and their relief-forming role

Thus, the division of tectonic movements into vertical and horizontal is largely arbitrary. In nature, as a rule, there is a transition from horizontal movements to vertical ones and vice versa, since one type of movement gives rise to another: horizontal stretching leads to subsidence, horizontal compression leads to the crushing of rocks into folds and their uplift.

Under vertical oscillatory movements The earth's crust is understood as constant, widespread, reversible movements of different scales in area and amplitude, which do not create folded structures. In foreign literature they are called epeirogenic (Greek. epeiros- continent, land, genesis– origin). The relief-forming role of these movements is enormous. Vertical movements of the highest order underlie the formation of planetary landforms of the earth's surface. They determine marine transgressions and regressions and thereby control the areas of land and oceans and their configuration.

Vertical movements of a lower order in tectonically quiet areas (on platforms) form syneclises and anteclises, which, in the case of the inherited nature of these movements in modern times, are directly reflected in the relief in the form of mega- and macroforms: lowlands and hills (the Central Russian Upland mainly corresponds to the Voronezh anteclise, Caspian lowland - Caspian syneclise).

Slow vertical movements of different signs occurred in the geological past and continue today. Now Scandinavia is slowly rising, and the North Sea coast, on the contrary, is falling, which is why in Holland, in order to save themselves from transgression, they are forced to build dams up to 15 m high. The speed of these movements reaches several millimeters per year and is recorded using observations and instrumental measurements.

Along with vertical ones, there are everywhere and constantly horizontal movements, which play a leading role in the development and formation of primarily the largest relief forms. Thus, continental rifts and horizontal sideways movements of lithosphere blocks are associated with the opening of oceans and the movement of continents and, accordingly, changes in their areas and outlines. A young giant expanding graben, i.e. a rift, a future ocean, is considered to be the Red Sea depression, the sides of which shift by several millimeters V year from the axial zone in different directions. The collision of continental plates, compression and crowding of sedimentary and volcanic strata of the Tethys Ocean, especially against the Arabian salient and the Hindustan block of Gondwana, explains the formation of the highest mountain ranges from the Caucasus to the Himalayas.

The earth’s crust reacts to vertical and horizontal tectonic movements by deformation of rock layers, leading to two types of dislocations: folded (plicative)– bending of layers without breaking their continuity and discontinuous (disjunctive), along which, as a rule, the crustal blocks move in vertical and horizontal directions. Both types of dislocations are characteristic of the Earth's mobile belts, where mountains are formed. Therefore, tectonic movements leading to disruption of the primary horizontal occurrence of rocks, i.e. formation of dislocations, are called orogenic, creating mountains (Greek) oros– mountain, genesis– origin). Folded and discontinuous dislocations manifest themselves in relief.

Folded dislocations are clearly expressed in geosynclines and young epigeosynclinal areas and are practically absent in the cover of platforms. Relatively simple convex folds - anticlines - usually form low folded ridges (Tersky, Sunzhensky ridges in the North Caucasus), and concave folds - synclines - intermountain and foothill depressions.

Larger and more complex in internal structure, convex folds (anticlinoria) are expressed in the relief by high ridges, and concave folds (synclinoria) are expressed by large, deep intermountain depressions. However, as a rule, they have a more complex folded-block structure, such as the Main and Side ranges of the Caucasus.

The largest and most complex folds form epigeosynclinal mountainous countries (Caucasus, Alps, etc.). Their formation is accompanied by large arched uplifts of large radius, caused by an increase in the thickness of the earth's crust, which is lighter than the oceanic crust and, due to the law of isostasy, is buoyant.

Rupture dislocations take place not only within fold belts, but also on platforms, both on land and at the bottom of the World Ocean. Since they are accompanied by vertical and horizontal movements of blocks of the earth’s crust, they are a powerful factor in relief formation.

The largest landforms on Earth caused by fault tectonics are rifts– deep, narrow depressions bounded by fault zones. They are formed during the stretching of the earth's crust due to the subsidence of the axial parts of large wave-like swellings, which were formed, in turn, under the influence of ascending mantle flows. They are characterized by a decrease in the thickness of the earth's crust and lithosphere as a whole, high seismicity, volcanic activity, and high heat flow. Rifts exist both at the bottom of the oceans and on continents.

With the vertical displacement of several blocks of the earth's crust along faults up and down in elevated areas - handfuls block mountains are formed, in the lowered areas - grabens– basins. Deep grabens are occupied by lakes.

Education cuesta ridges And ridges also often accompanied by faults, along which one slope of the block rises in the form of a ledge, and a river valley is laid along the fault.

With subhorizontal faults and subsequent displacements of layers in the mountains, one section of the earth’s crust can be pushed onto another by tens of kilometers - this thrusts (overthrusts). They are expressed in the Alps, Pyrenees, Himalayas and other mountain structures.

Faults often determine the outlines of the coastline of continents on platforms: the so-called fault type of coasts is found in the north of the Kola Peninsula, on the Somali Peninsula and other shores of the Gondwana continents.

River valleys are almost always formed along faults, which are zones of increased fracturing of rocks, both in the mountains and on the plains. This is also facilitated by the concentration of surface and groundwater in them.

Folded and fractured dislocations of layers, especially in the mountains, are accompanied by deep (intrusive) And surface (effusive) magmatism And earthquakes, which are also reflected in the relief.

Intrusive bodies come in different shapes and sizes. Large intrusions, especially batholiths, having an elongated shape, stretching for hundreds of kilometers (the Chilean batholith in the Andes is over 1300 km long, the batholith in the Canadian Cordillera is over 2000 km), reaching a width of up to 100 km and a thickness of up to 10 km. Batholiths cause disturbances in the occurrence of overlying rocks. These disturbances can be either folded or discontinuous in nature. Batholiths, usually composed of granites, form the central uplifts of many folded mountain regions. As a result of subsequent denudation, they often end up on the surface, forming massive, inaccessible axial mountain ridges (Sierra Nevada, Coast Range in Canada).

Intrusions in the form laccoliths dome-shaped or loaf-shaped give the same shape to the overlying rocks and form groups or single mountains, such as, for example, the mountains Zheleznaya, Mashuk, Beshtau and others in the Pyatigorsk region in the North Caucasus, Mount Ayu-Dag in the Crimea. The exposed intrusions are the Khibiny and neighboring massifs with a height of more than 1000 m.

Reservoir intrusions are expressed in relief in the form of steps. Prepared (semi-deep) intrusions and basaltic effusives in the form of huge covers (traps) are widespread on plateaus and plateaus within ancient platforms (for example, on the Central Siberian Plateau).

Creates a unique relief effusive magmatism, or volcanism. Depending on the nature of the outlets, areal, linear and central eruptions are distinguished. Area and linear eruptions predominated in the geological past. They formed ocean floors, vast lava plateaus and highlands (Colombian Plateau, Fraser Plateau, Mexican and Ethiopian Highlands, etc.). In historical times, significant lava outpourings occurred in Iceland and the Hawaiian Islands; they are also very typical for mid-ocean ridges.

In the modern geological era on continents, the most common eruptions are of the central type, when magma rises through a narrow channel, usually arising at the intersection of faults. In this case, cone-shaped or shield-shaped mountains are formed - volcanoes with a funnel-shaped extension at the top called crater. The shape of volcanoes depends on the composition of the magma, viscosity and speed of its solidification. Many volcanoes consist of loose eruption products interlayered with hardened lava. These are Klyuchevskaya Sopka, Fuji, Elbrus, Ararat, Vesuvius, Krakatoa, Chimbarazo and other volcanoes.

Some extinct volcanoes have large circus-shaped depressions with steep walls and a flat bottom, called calderas. They are formed due to the collapse of the volcano's summit due to the rapid emptying of the volcanic chamber. One of the largest is the Ngorongoro caldera west of Mount Kilimanjaro in Tanzania. It is a huge bowl, at the bottom of which there is a lake and a green meadow. The diameter of the bottom is 22 km. The walls of the crater rise to 600–700 m. There is a unique reserve with thousands of wild animals. This natural zoo is called the "African Ark".

Places where volcanic activity has subsided (for example, Yellowstone National Park in the USA) are characterized by hot springs, including periodically gushing ones, - geysers, gas emissions from craters and cracks, mud volcanoes, which indicate active processes in the depths of the bowels.

Endogenous processes also include earthquakes– sudden underground impacts, tremors and displacements of layers and blocks of the earth’s crust. The sources of earthquakes are confined to fault zones. In most cases, earthquake centers, i.e. hypocenters, are located at a depth of the first tens of kilometers in the earth's crust. However, sometimes they are located in the upper mantle at depths of up to 600–700 km, for example along the Pacific coast, in the Caribbean Sea and other areas. Elastic waves arising in the source, reaching the surface, cause the formation of cracks, its oscillations up and down, and displacement in the horizontal direction. The greatest destruction is observed in epicenter earthquakes located above the hypocenter. The intensity of earthquakes is rated on a scale of twelve based on the deformation of the Earth's layers and the degree of damage to buildings. Hundreds of thousands of earthquakes are recorded on Earth every year, so we live on a restless planet. During catastrophic earthquakes, the topography changes in a matter of seconds, landslides and landslides occur in the mountains, cities are destroyed, and people die. Earthquakes on the coasts and ocean floors cause waves - tsunamis. The catastrophic earthquakes of recent decades include the Ashgabat (1948), Chilean (1960), Tashkent (1966), China (1976), Mexico City (1985), Armenian (1988), Japanese (1995), Turkish (1999), Indian (2001). Volcanic eruptions are also accompanied by earthquakes, which are limited in nature.

In general, endogenous processes play a constructive role in relation to the relief: during tectonic uplifts of any origin, the Earth’s surface rises, the relief experiences upward development, its elevations increase, which contributes to the accumulation of masses in the upper (“relief”) part of the earth’s crust. It is obvious that endogenous processes control the nature and intensity of exogenous processes.

2.2.2. External (exogenous) processes and their relief-forming role

The role of exogenous processes in relief formation is enormous and commensurate with the role of endogenous processes, since the speed of tectonic movements and the intensity of destruction are measured by values ​​of the same order. According to the research of N.I. Makkaveev, the entire existing earth's surface (with all its mountains) can level out into an ideal plain 50 m high above sea level (with a modern average height of 850 m) in 10–12 million years. However, this is prevented by upward tectonic movements of the earth's crust.

The activity of any external factor consists of processes denudation, i.e. destruction and demolition, and accumulation, i.e., deposits of material in depressions. Denudation can be linear or planar. Linear Denudation, in turn, is divided into deep and lateral. Deep increases the density and depth of the terrain and enhances the contrast of the relief. Lateral accompanied by the expansion of negative forms and softens the relief. Planar(areal) denudation spreads over the entire surface and does not dissect, but, on the contrary, smoothes it out everywhere. The main driving force of denudation is gravity.

Exogenous processes, smoothing out and destroying large unevenness of the earth's surface, at the same time form new smaller relief forms - morphosculpture. But this is preceded weathering– a set of processes of physical destruction and chemical transformation of rocks and minerals on the earth’s surface under the influence of various atmospheric agents.

Physical weathering – mechanical grinding of rocks and minerals under the influence of sharp temperature fluctuations. Temperature insolation weathering very typical for tropical deserts, where there are large daily temperature amplitudes of surface rocks. If the temperature passes through 0°C during the day, at night the water in the cracks of the rocks freezes and, increasing in volume, destroys the rock, weathering is called frosty(it is typical, for example, for Eastern Siberia).

Chemical weathering accompanied by a change in the chemical composition of rocks under the influence of alkalis, salts, acids, gases contained in water and air. During chemical weathering, new (supergene) minerals are formed that are stable under the conditions of the earth's surface (hydromicas, montmorillonite, kaolin). It is very typical for hot, humid climates. Physical and chemical weathering are interrelated. For example, in hot deserts, soil loosening is associated not only with a large daily temperature range, but also with salt weathering due to significant evaporation.

Living organisms also take part in the weathering of rocks, producing mechanical and chemical changes.

As a result of the weathering of rocks, loose deposits are formed that are easily transported by water, ice, wind, etc. At the same time, it must be emphasized that the weathering process itself is not relief-forming - the shape of the surface does not change during weathering.

Rock destroyed as a result of weathering, but not yet transported anywhere, is called eluvium. Its characteristics are a close connection of the chemical and mineral composition with the underlying source rocks.

Undisplaced (residual) weathering products form weathering crust. The thickness of the weathering zone varies, but does not exceed 100–200 m. It is greater in flat areas of the earth’s surface with a stable tectonic regime and slow demolition. The weathering crust has a zonal character. Clastic the crust predominates in polar regions, highlands and rocky deserts; hydromica crust - in cold and temperate latitudes, including permafrost; montmorillonite– in steppes and semi-deserts; kaolinite And red earth– in the subtropics; lateritic- in the equatorial belt.

The variety of exogenous relief-forming processes leads to the formation of denudation and accumulative morphosculpture. Denudation relief forms arise as a result of the destruction and demolition of rocks (ravines, glacial hollows, etc.), accumulative forms - during the deposition of rocks (gully alluvial cones, moraine hills, etc.). Along with them there may be denudation-accumulative landforms (river terraces, landslides).

The exogenous group also includes anthropogenic relief-forming processes, although they are subject to more complex socio-natural patterns. Indeed, they develop in places where one or another human activity occurs, but such places are often predetermined by natural conditions. To a large extent, anthropogenic processes are also subject to natural laws, especially if these are processes not of direct, but of indirect anthropogenic action (i.e., changes in relief occur not directly by an excavator, but due to the removal of turf, an increase or regulated river flow, etc. .). Exogenous relief-forming processes usually do not occur separately on Earth, but nevertheless, as a rule, it is possible to distinguish the leading exogenous process and the resulting denudation and accumulative forms of relief. All of them, together with the correlative deposits that make up the accumulative landforms, are shown in Scheme 2. Thus, in the contradictory activity of internal and external forces, in their struggle, interaction and unity, the dialectic of the historical development of our planet is expressed, and the result of this work is the modern face of the Earth.

Scheme 2

Genetic classification of exogenous relief types

2.3. Relief formation factors

Geological ones include neotectonic (including modern) movements of the earth’s crust, physicochemical properties of rocks, depending on their material composition, and geological structures: the nature of the occurrence of rock layers and their fracturing. Neotectonic movements, being themselves a process of endogenous relief formation, they determine the direction, pace, and sometimes the type of exogenous processes. With positive movements, this occurs through: a) absolute heights and their relation to the snow boundary (the higher, the faster the denudation, as well as the appearance of glaciers); b) excess over erosion bases, depth of incision and slopes of valley slopes (the greater, the stronger the denudation). Negative movements determine the downward development of the relief and the predominance of sediment accumulation. In addition, neotectonic movements determine the lithology of the near-surface rocks that make up the relief (during uplift, hard rocks are often exposed, and when lowering, loose sediments accumulate), as well as their fracturing.

Physicochemical properties of rocks determine the degree of their resistance to weathering and external agents of relief formation. Based on this criterion, three groups of breeds can be distinguished. Quaternary sedimentary rocks are mostly loose and easily destroyed (eroded) by surface waters and wind. Over a long period of time, pre-Quaternary sedimentary rocks managed to become hard (lithified) and are therefore resistant to mechanical destruction and weathering, but a significant part of them (limestones, gypsum, salts) are subject to dissolution. Igneous and metamorphic rocks, on the contrary, are very weakly susceptible to erosion, but are easily weathered, and polymineral rocks are the least resistant to physical temperature weathering, since the minerals included in their composition have different thermal conductivity and heat capacity.

The water properties of the rock are also important - moisture capacity and water permeability. There are numerous erosion forms on clays and other rocks that are poorly permeable to surface water. Sands “quench” erosion by converting surface runoff into underground, so erosion forms are usually less common on them than on clays. When loose permeable and water-resistant rocks alternate on slopes, landslides occur. All of the listed properties manifest themselves differently in a specific physical-geographical environment and find a certain morphological embodiment.

Geological structures are a powerful factor in the formation of relief. When the relief forms correspond to the conditions of rock occurrence, a structural relief, if there is no coincidence between them, - astructural. An example of structural relief is stratified plains and plateaus on platform slabs or, for example, laccolith mountains, formed by the introduction of mushroom-shaped intrusions into the upper sedimentary layers, which take the form of the contours of laccoliths (Fig. 6); intrusions-dykes, expressed ridges, intrusions-stocks in the form of cone-shaped hill

Rice. 8. Block diagram - profile through the Southern Appalachians (according to G. M. Ignatiev)

An example of a peculiar structural-denudation relief is cuestas(cuesta– slope) – asymmetrical ridges and ridges (Fig. 7). They are formed by the monoclinal occurrence of alternating resistant and yielding strata as a result of selective denudation. In cuesta ridges, a gentle slope coincides with the fall of hard rocks (structural slope), while a steep slope cuts the layers in the form of a ledge (astructural slope).

More complex terrain is observed in the mountains in place of folded structures. If the ridges correspond to anticlines, and intermountain valleys correspond to synclines, the relief is called direct. Such a very complete correspondence of mountains to the tectonic structure is observed in the modern Pacific geosynclinal belt and in places among the mountains of Alpine folding, for example, in the Jura ridge. This type of mountainous relief was first described in the Alps and received the common name “Jura-type relief.”

When the relief is inversely related to geological structures, it is called converted. Such inversion relief is very characteristic of the Southern Appalachians and is known under the common name “Appalachian-type relief” (Fig. 8). Even more complex relationships between the topographic surface and folded structures are observed in secondary revived mountains, broken by faults into blocks and raised to different heights.

Fracture rocks is of great importance in the formation of denudation relief. Thus, inverted relief develops well with significant fracturing in the locks of anticlines, because the rocks there are destroyed faster than in the locks of synclines, and valleys are formed in their place. River valleys, especially large ones, generally prefer to be formed in fracture zones and along faults, which is why in the mountains they can have an incongruously large width. The fracturing of rocks often determines the pattern of erosional forms in plan, and in the presence of soluble rocks, karst processes and landforms.

Geographical factors are primarily related to climate. The relationship between relief and climate is diverse and complex; climate affects the relief directly and indirectly. Climate determines a set of exogenous relief-forming processes, their nature and intensity. Therefore, modern morphosculpture to a certain extent zonal.

A. Penkom at the beginning of the 20th century. a classification of climates was proposed according to their relief-forming role, in which he identified three main types: 1) nival (lat. nivalis– snowy); 2) humid (lat. humidis– wet); 3) arid (lat. aridus- dry).

Nival climate characteristic of polar regions and high mountains. In cold climates, frost weathering occurs intensively, and the main relief-forming factors are snow and ice. The predominant landforms are nival-glacial.

Humid climate observed in humid areas with a humidification coefficient greater than one. In a humid climate, chemical weathering occurs intensively. The main factor of exogenous relief formation is surface flowing water. Therefore, typical erosional landforms are river valleys, ravines, and ravines. In the presence of soluble rocks, karst relief is observed. Humid climate zones are distinguished in temperate zones and in the equatorial zone. The manifestation of relief formation in them is somewhat specific. For example, in temperate latitudes negative forms of karst relief predominate, and in equatorial-tropical latitudes - positive forms of karst.

Arid climate characteristic of deserts of tropical, subtropical and temperate latitudes. Low precipitation and dry air lead to sparse vegetation cover or its complete absence. Under these conditions, physical temperature weathering occurs intensively. The main relief-forming factor is wind, and accordingly, various forms of aeolian relief dominate.

This classification of climates in subsequent years was supplemented by transitional semihumid and semiarid (lat. semi– half, half) and other morphoclimatic zones in different latitudes of the Earth. The zoning of the Earth's surface according to the morpho-climatic conditions of relief formation is shown in Figure 9.

Rice. 9. Scheme of modern morphoclimatic zoning (according to K.V. Pashkang)

Along with zonal ones, extrazonal and azonal geomorphological processes and landforms are distinguished. Extrazonal(lat. extra– outside, Greek zone– zone) processes and landforms are those that are not typical, alien to a given zone, but are found in it, for example, river valleys of large transit rivers Nile, Amu Darya and other rivers in deserts. Azonal processes and landforms are those that are common to many natural areas. For example, sea activity and coastal landforms exist in all natural zones, regardless of climate. Zoning, of course, leaves a specific local imprint on azonal phenomena, for example, on river floodplains in different natural zones.

Important for the development and appearance of the relief is time factor, which can be represented through the history of relief development. The relief is not a frozen formation - it is characterized by dynamics, evolution, changes, that is, it develops over time. This is sometimes called terrain functioning. Some of these changes take place before our eyes (almost all anthropogenic landforms, erosional relief, relief of sea coasts, less often slopes, volcanic relief change rapidly), others last for centuries and millennia.

Since it is a relief, then there are concepts of the age of the relief and the history of its development. Relief age– a concept in geomorphology that is important, but very complex. We can only say with certainty that large landforms are older (millions of years) than small ones. In addition, one can speak more or less definitely about the age of accumulative forms based on the age of the rocks composing them, and not on denudation forms. In geomorphology, the concept of “relative” and “absolute” relief age is used.

Under relative age one can understand certain stages of its development - youth, maturity, old age (according to V. Davis) on the basis of morphological characteristics. The concept of “relative age” is also used in the relationship of some forms with others, for example, a river floodplain is younger than a river valley. One can also consider the relative age to be the time interval from which the relief acquired an appearance similar to the modern one, for example, the Holocene age of river floodplains in the area of ​​the Valdai glaciation.

Absolute age relief is established in absolute years on the basis of radioisotope and other precise methods.

Age and development history determine the appearance and dynamics of relief even of the same genesis. Moreover, relief forms do not necessarily have to correspond to modern relief-forming processes - the relief is quite conservative, it is a memory of the geographical envelope. According to the time of formation, i.e., according to age, morphosculpture is divided into three types: modern, inherited and relict.

Modern morphosculpture is currently formed under certain climatic conditions.

TO inherited morphosculpture These include young relief forms that arose in place of similar forms and took on, to a certain extent, their appearance, orientation, and size, for example, river valleys on the site of buried pre-glacial valleys, bottom ravines in gullies.

Relict landforms formed in different climatic conditions and are currently in sharp discrepancy with modern climatic conditions and do not develop, for example, dry valleys in deserts, glacial and water-glacial landforms in the north of temperate latitudes, overgrown dunes on river terraces.

The earth's surface is actively affected by a variety of natural and anthropogenic processes. The leading role in this complex is played by geomorphological (relief-forming) processes that are responsible for changes in the basis of the landscape - the relief. The most important thing is to assess the effect of these processes over the past 150–200 years, which determines current trends in the development of the natural environment.

Relief formation (geomorphogenesis) is divided into endogenous and exogenous processes. Endogenous processes operate internally and use the energy accumulated in its depths. Among them are tectonic, caused by the deformation of the solid matter of the earth's crust, and magmatic, associated with the movement of matter in a liquid and gaseous state and causing volcanic phenomena. Endogenous processes operate over many millions of years and form mainly large relief irregularities (mountains, depressions, etc.). Their speed, as a rule, is low (millimeters, centimeters per year). The exception is sudden movements along faults, causing seismic phenomena.

Exogenous processes are external (in relation to the “solid Earth”) influences that are caused by energy coming mainly from the Sun, as well as gravity and the rotation of the Earth around its own axis. Depending on the nature of their flow, they are divided into fluvial, gravitational, cryogenic, glacial, nival, coastal (coastal wave), biogenic, karst and aeolian. A special type is represented by anthropogenic processes associated with human economic activity. These are the most dynamic processes of relief formation, the role of which in global geomorphogenesis has increased sharply over the past 150–200 years.

Fluvial processes are caused by the activity of water flows. On the territory of Russia they operate almost everywhere, actively forming the channels, floodplains and deltas of numerous rivers. The activity of temporary watercourses leads to the formation of ravines, gullies, potholes, furrows (erosion processes), and alluvial cones. Flows of rain and melt water erode the soil on the slopes and cause the accumulation of washed-out material (colluvium) at their foot.

Gravity processes are typical for mountainous regions, but are also common on steep, eroding banks of rivers, lakes, reservoirs and seas. Their main varieties are landslides, screes, landslides, creep (slow mass movement of loose soil down the slopes). When interacting with nivation or cryogenesis, kurums (moving accumulations of large blocks on slopes) and solifluction (flow of thawed soils in permafrost areas) arise.
Cryogenic processes are associated with seasonal thawing and freezing of soils in areas of permafrost, which is widely developed in Siberia, the Far East and the north of the European part of Russia. They manifest themselves in cracking and deformation of rocks, soil heaving, thermokarst (thawing of underground ice), thermoerosion (formation of ravines in frozen strata) and thermal abrasion (destruction of icy shores).

Glacial processes are caused by the destructive (exaration), transporting and accumulating activity of glaciers in mountainous and polar regions. As a result of gouging, an alpine-type relief is formed (troughs, kars, carlings), and glacial accumulation forms moraine complexes.

Nival processes are caused by the destructive effect of snow on underlying rocks in polar, subpolar and high-mountain regions, leading to the formation of niches, carts, and circuses on the slopes. This is facilitated by alternate freezing and thawing of rocks and increased frost weathering.

Biogenic processes manifest themselves mainly in wetlands, of which there are many in Western Siberia, in the north of the European part of Russia, and in areas in the east of the country. There is active accumulation of peat here, which is expressed in the formation of gently convex interfluves and hummocky microrelief.

Areas of distribution of soluble rocks (limestones, dolomites, gypsum, rock salt) are characterized by karst processes. Here various forms of surface karst (craters, karras, fields, etc.) and deep (caves, abysses) arise and continue to develop. They are often accompanied by failures that have catastrophic consequences.
Aeolian processes are spread sporadically, mainly in places where large sand massifs accumulate, which are located in an arid or subarid climate. There, barchan ridges and dunes created in previous eras are formed or continue to develop. In the southern arid regions, deflation (blowing out) of the upper fertile layer periodically occurs.

Coastal processes. The activity of waves on the shores of seas, lakes, and reservoirs changes the transverse profile of the coastal zone and the configuration of the coastline. On the shores of Bely, tidal processes also play a significant role in the formation of the shores. As a result of destruction (abrasion), ledges (cliffs) and rocky areas at their feet (bench) appear on the banks. The accumulating activity of waves leads to the formation of beaches, coastal bars, underwater bars, spits, bay bars and other forms.

At the bottom of the ocean there is an accumulation of substances coming from land, redistribution and erosion of sediments by currents, among which the most significant role is played by turbidity currents, concentrated in underwater canyons. In the eastern sector of the Arctic, thermal abrasion of ice deposits that make up the bottom is of significant importance.

Anthropogenic geomorphological processes are extremely diverse in nature and intensity of manifestation. First of all, attention is drawn to the redevelopment of the relief in urban areas, in areas of industrial and transport construction. Extraction is accompanied by the formation of varying sizes of negative relief forms (quarries) and positive ones (dumps, waste heaps). Some of them reach several kilometers in diameter with a relative depth (height) of several hundred meters.

The zoning of exogenous processes is expressed in the zonal location of various varieties of these processes. In the mountains, a vertical zonality of geomorphogenesis is outlined, especially pronounced in the southern high-mountain regions (Caucasus, Altai). In the lower belt of these mountain regions, as a rule, fluvial processes (erosion, planar washout, mudflow and accumulation) predominate. In the middle zone, gravitational and partly nival-cryogenic processes become significant. In the upper, high-alpine zone, nival-glacial processes dominate.

In most middle and low mountains of Siberia and the Far East, as well as in the north of the Urals and in, which are in the area of ​​permafrost, the altitudinal zonation is not so clearly expressed. Cryogenic and nival processes predominate in them, and only in places in the summit belt are glacial and gravitational processes added to them.

The zonation of exomorphogenesis on the plains is subject to global climatic patterns, so it is latitudinal in nature. The Arctic belt is dominated by nival-glacial and nival-cryogenic processes. In the tundra zone on the plains, cryogenic morphogenesis predominates. The taiga zone, where frozen soils are predominantly widespread, also falls under the influence of cryogenesis, although fluvial processes also play a significant role in it. In zones of mixed and deciduous forests, as a rule, fluvial processes predominate. In the steppe and forest-steppe zones, in addition to fluvial processes, anthropogenically caused erosion is intensively developed and deflation periodically occurs. The most widespread are aeolian processes, with erosion being of subordinate importance.

The relief of continents is constantly changing under the influence of internal and external processes. The movement of matter in the mantle is manifested in the action of internal processes - movements of lithospheric plates, faults of the earth's crust, intrusions of mantle matter into the earth's crust and its outpouring onto the surface. The movements of the lithosphere are so strong that they move entire layers of rocks, crush them into folds, change the structure of the earth's crust, that is, change its relief.

The manifestation of external processes is associated with the energy of the Sun, the influence of gravity, the action of liquid and solid water, and the vital activity of organisms. External processes destroy rocks, the products of destruction are transferred from higher areas to lower ones, where they are deposited and accumulated.

Weathering plays a huge role in the destruction and leveling of continental topography. Under the influence of weathering forces, even the hardest rocks are destroyed and bizarre shapes are formed (5.3, 5.4). (Think about why.) Physical weathering of rocks is most evident in deserts such as the Sahara.

Internal and external processes affect the relief of the planet simultaneously and constantly. The influence of external processes increases if the action of internal forces is activated. For example, the destructive work of rivers increases if the territory through which they flow begins to slowly rise under the influence of internal processes. River valleys are deepening and deep gorges (canyons) are being formed in the mountains.

If the territory sinks, destruction products are deposited on it, and flat forms are formed. Internal processes mainly create large landforms, while external processes mainly destroy them, modify them and create landforms of different sizes.

Minerals. Our planet's crust contains vast and varied riches - rocks and minerals that have been mined and used by people for a long time.

Among the mineral resources that are extracted from the earth's crust and used in agriculture, there are more than 200 different types of minerals. The distribution of mineral deposits is subject to natural laws.

Combustible (fuel) fossils (Remember what they are classified as.) are of sedimentary origin. They play an important role in the economy. Most of them are located in Eurasia and North America. The main deposits of oil and natural gas are also located on the territory of the northern continents (Find them on the atlas map.)

Ore mineral deposits are formed in both sedimentary and igneous rocks. Most of the ore deposits are associated with platform foundations and projections of crystalline rocks onto the surface. These are platform shields, as well as folded areas of the earth's crust. In such areas, huge ore belts often form, for example, the belt of tin deposits in Eurasia, platinum, chromite, uranium in South Africa, and the copper belt in the Andes (5.6, 5.7, 5.8, 5.9).

Relief features influence the distribution of the population. 4/5 of the Earth's population lives in lowlands and hills with altitudes up to 500 m above sea level. With the development of industry, the population concentrated in areas where there was the most successful combination of mineral wealth, such as coal and iron ore, etc.