Relief-forming processes - the movement of matter and energy in the earth's crust and on the earth's surface, causing the formation, modification and destruction of landforms.
Depending on the source of energy, relief-forming processes are divided into endogenous and exogenous. Both those and others always form the relief together, but either one or the other processes prevail in the formation of individual types of relief.

External relief-forming processes

Exogenous forces, excited by the energy of solar rays and gravity, on the one hand, destroy the forms created by endogenous forces, on the other hand, create new forms. In this process, there are:

1) destruction rocks(weathering - it does not create landforms, but prepares the material)

2) removal of broken material, usually downhill drift (denudation)

3) redeposition (accumulation) of demolished material. If this forms an almost flat surface, they speak of peneplanation.

The most important agents of manifestation of external forces are air and water. There are physical, chemical and biogenic weathering.

Physical weathering occurs due to uneven expansion and contraction of rock particles with temperature fluctuations. It is especially intense in transitional seasons and in areas with a continental climate, large daily temperature ranges - in the highlands of the Sahara or in the mountains of Siberia, while entire stone rivers - kurums - are often formed. If water penetrates into the cracks of the rocks, and then, solidifying and expanding, increases these cracks, they speak of frosty weathering.

Chemical weathering is the destruction of rocks and minerals under the action of active substances contained in the air, water, rocks and soils (oxygen, carbon dioxide, salts, acids, alkalis, etc.) as a result of chemical reactions. On the other hand, chemical weathering is favored by humid and warm conditions typical of maritime regions, humid tropics, and subtropics.

Biogenic weathering is often reduced to the chemical and physical impact on rocks of organisms.

Usually several types of weathering are observed simultaneously, and when they talk about physical or chemical weathering, this does not mean that other forces are not involved in this - just the name is given by the leading factor.

Water is "the sculptor of the face of the earth" and one of the most powerful agents of relief reconstruction. Flowing waters affect the relief, destroying rocks. Temporary and permanent water flows, rivers and streams for millions of years "bite" into the earth's surface, erode it (erosion), move and redeposit the washed-out particles. If it were not for the constant uplift of the earth's crust, only 200 million years would be enough for water to wash away all the areas protruding above the sea and the entire surface of our planet would represent a single boundless ocean. The most common erosive landforms are linear erosion forms: river valleys, ravines and gullies.

Ravines and gullies are formed by temporary streams that appear after snow melts or heavy rains fall. They differ from each other in that ravines are constantly growing, cutting into loose rocks, narrow steep ruts, and beams - having a wide bottom and hollows that have ceased to develop, are occupied by meadows or forests.

Rivers create a wide variety of landforms. In river valleys, the following forms are distinguished: the root bank (river sediments do not participate in its structure), floodplain (part of the valley flooded during floods or floods), terraces (former floodplains that rose above the edge as a result of a decrease in the erosion base), oxbow lakes (sections of the river separated from the former channel as a result of meandering).

In addition to natural factors (the presence of surface slopes, easily eroded soils, heavy rainfall, etc.), the formation of erosion forms is facilitated by irrational human activity - clear deforestation and plowing of slopes.

In addition to water, an important factor of exogenous forces is the wind. Usually it has less strength than water, but working with loose material can work wonders. Forms created by the wind are called aeolian. They predominate in dry areas, or where dry conditions have existed in the past (relic aeolian forms). These are dunes (crescent-shaped sandy hills) and dunes (oval-shaped hills), turned rocks.

Internal relief-forming processes

Mountains, plains and uplands differ in height, the nature of the occurrence of rocks, the time and method of formation. Both internal and external forces Earth. All modern relief-forming factors are divided into two groups: internal (endogenous) and external (exogenous).

The energy basis of internal relief-forming processes is the energy coming from the depths of the earth - rotational, radioactive decay and the energy of geochemical accumulators. Rotational energy is associated with the release of energy when the Earth's rotation around its axis slows down due to the influence of friction (fractions of seconds per millennium). The energy of geochemical accumulators is the energy of the Sun accumulated over many millennia in rocks, which is released when rocks sink into the inner layers.

Exogenous (external forces) are called so because the main source of their energy is outside the Earth - this is energy directly coming from the Sun. For the manifestation of the action of exogenous forces, the roughness of the earth's surface must be involved, creating a potential difference and the possibility of moving particles under the action of gravity.

Internal forces tend to create irregularities, and external forces tend to level these irregularities.

Internal forces create the structure (basis) of the relief, and external forces act as a sculptor, processing "roughness created by internal forces. Therefore, endogenous forces are sometimes called primary, and external forces are secondary. But this does not mean that external forces are weaker than internal ones. For geological history, the results manifestations of these forces are comparable.

We can observe the processes occurring inside the Earth in tectonic movements, earthquakes and volcanism. Tectonic movements are the whole set of horizontal and vertical movements of the lithosphere. They are accompanied by the appearance of faults and folds of the earth's crust.

For a long time, the "platform-geosynclinal" concept of the development of the Earth's relief dominated science. Its essence lies in the allocation of calm and moving parts of the earth's crust, platforms and geosynclines. It is assumed that the evolution of the structure of the earth's crust proceeds from geosynclines to platforms. There are two major stages in the development of geosynclines.
The first (main in terms of duration) stage of subsidence with a marine regime, the accumulation of a thick (up to 15-20 km) strata of sedimentary and volcanic rocks, lava outpouring, metamorphism, and subsequently with folding. The second stage (shorter in duration) is folding and ruptures during general uplift (mountain building), as a result of which mountains are formed. Mountains subsequently collapse under the influence of exogenous forces.

In recent decades, most scientists adhere to another hypothesis - the hypothesis of lithospheric plates. Lithospheric plates are vast areas of the earth's crust that move along the asthenosphere at a speed of 2-5 cm / year. A distinction is made between continental and oceanic plates; when they interact, the thinner edge of the oceanic plate sinks under the edge of the continental plate. As a result, mountains, deep-sea trenches, island arcs (for example, the Kuril Trench and the Kuril Islands, the Atakama Trench and the Andes Mountains) are formed. When continental plates collide, mountains are formed (for example, the Himalayas when the Indo-Australian and Eurasian plates collide). Plate movements can be caused by convective movements of the mantle matter. In places where this substance rises, faults form, and the plates begin to move. The magma that intrudes along the faults solidifies and builds up the edges of the diverging plates - this is how the mid-ocean ridges are formed, stretching along the bottom of all the oceans and forming a single system 60,000 km long. Their height reaches 3 km, and the greater the width, the greater the speed of expansion.

The number of lithospheric plates is not constant - they are connected and divided into parts during the formation of rifts, large linear tectonic structures, such as deep gorges in the axial part of the mid-ocean ridges. It is believed that in the Paleozoic, for example, modern southern continents represented one mainland - Gondwana, the northern ones - Laurasia, and even earlier there was a single supercontinent - Pangea and one ocean.

Along with slow horizontal movements, vertical ones also occur in the lithosphere. When plates collide or when surface loads change, for example due to the melting of large ice sheets, uplift occurs (the Scandinavian Peninsula is still uplifting). Such oscillations are called glacioisostatic.

The tectonic movements of the earth's crust of the Neogene-Quaternary time are called neotectonic. These movements were and are being manifested with varying intensity almost everywhere on Earth.

Tectonic movements are accompanied by earthquakes 1 (shocks and rapid oscillations of the earth's surface) and volcanism (the intrusion of magma into the earth's crust and its outpouring to the surface).

Earthquakes are characterized by the depth of the source (places of displacement in the lithosphere, from which seismic waves propagate in all directions) and the strength of the earthquake, estimated by the degree of destruction caused by it in points on the Richter scale (from 1 to 12). The greatest force of an earthquake is reached directly above the source - in the epicenter. In volcanoes, a magma chamber and a channel or cracks are distinguished along which lava rises.

Most earthquakes and active volcanoes are confined to the margins of lithospheric plates - the so-called seismic belts. One of them encircles the Pacific Ocean along the perimeter, the other stretches through Central Asia from Atlantic Ocean to the Pacific.

Relief-forming processes

Relief - it is a set of irregularities of the earth's surface of different scales, called landforms.

The relief is formed as a result of the impact on the lithosphere of internal (endogenous) and external (exogenous) processes.

According to modern concepts, the lithosphere consists of rigid mobile plates moving along the plastic mantle. The boundaries between plates can be of three types: oceanic ridges (along which the mantle material rises to the surface and a new seabed is formed), trenches (along which the edge parts of the plates collapse, sinking into the mantle) and transform faults (formed as a result of the sliding of one plate along another ). Thus, the boundary between the African and American plates runs along the oceanic ridge, between the Antarctic and American plates - along the complaint, and between the Pacific and American plates - along transform faults. In the second half of the 20th century, extensive studies of the bottom of the World Ocean unfolded, as a result of which completely new ideas about the development of oceans and continents appeared, based on the views of the German scientist, the first half of the 20th century. A. Wegener.

The basis of the new theories of lithospheric plates the idea is that the entire lithosphere is divided by narrow active zones - deep faults - into separate rigid plates floating in the plastic layer of the upper mantle.

Internal (endogenous) processes. Internal geological processes cause various tectonic movement, that is, vertical and horizontal movements of individual sections of the earth's crust. They are associated with the formation of the most significant irregularities of the earth's surface, its continuous change. The source of internal processes is the heat generated during the radioactive decay of the elements that make up the Earth's core.

The movement of plates leads to changes in the configuration of the continents and oceans and their position on the Earth's surface. It is assumed that 500-200 million years ago all the continents were united into one, the so-called Pangea (translated from Greek as "the whole Earth"). In the next 70 million years, Pangea split into two continents: Laurasia, which included North America and Eurasia (excluding the Indian and Arabian subcontinents) and Gondwana (the rest of the land). The subsequent movement of the plates led to the convergence of North and South America, the separation of Australia and Antarctica, the movement of the Arabian and Indian subcontinents to Eurasia, and in the zone of collision of Eurasia with the latter, the most high mountains on the planet (Himalayas). Currently, there are six continents: Eurasia (53.4 million km 2), Africa (30.3 million km 2), North America (24.2 million km 2), South America(18.2 million km 2), Australia (7.7 million km 2) and Antarctica (14 million km 2).

According to the prevailing direction, two types of tectonic movements are distinguished: vertical and horizontal. Both types of movements can take place both independently and in conjunction with each other. Often one type of movement breeds another. They manifest themselves not only in the movement of large blocks of the earth's crust in vertical or horizontal directions, but also in the formation of folded and faulty faults of various scales.

Folds- wavy bends of the layers of the earth's crust, created by the combined action of vertical and horizontal movements in the earth's crust. A fold whose layers are curved upwards is called an anticline fold, or anticline. A fold whose layers are bent downwards is called a synclinal fold, or syncline. Synclines and anticlines are the two main forms of folds. Small and relatively simple in structure folds are expressed in the relief by low compact ridges (for example, the Sunzhensky ridge of the northern slope of the Greater Caucasus).

Larger and more complex in structure folded structures are represented in the relief by large mountain ranges and depressions separating them (Main and Lateral ranges of the Greater Caucasus). Even larger folded structures, consisting of many anticlines and synclines, form megaforms of relief such as a mountainous country, for example, the mountains of the Caucasus, the Urals, etc. These mountains are called folded.

Faults (faults)- these are various discontinuities of rocks, often accompanied by the movement of broken parts relative to each other. The simplest type of fractures are single more or less deep cracks. The largest faults that extend over a considerable length and width are called deep fractures.

Depending on how the broken blocks moved in the vertical direction, they distinguish discharges and thrusts(Fig. 7.6).

Rice. 7.6. a - reset; b- thrust

The combinations of faults and thrusts are horsts and grabens(Fig. 7.7).

Depending on their size, they form separate mountain ranges (for example, mesas in Europe) or mountain systems and countries (for example, Altai, Tien Shan).

In these mountains, along with grabens and horsts, folded massifs are also found, so they should be attributed to fold-block mountains.

In the case when the movement of rock blocks was not only in the vertical direction, but also in the horizontal direction, shifts.

In zones of separation of lithospheric plates - zones mid-ocean ridges- a new oceanic crust is born. In zones of collision of lithospheric plates - zones insular arcs and deep-sea trenches associated with them - one plate “dives” (more often with oceanic earth's crust) under another (more often with continental or transitional type of earth's crust). As a result of such “diving”, the edge of the plate bends and a deep-sea trench is formed. A striking example of such arcs are the Kuril and Japanese Islands, next to which are the corresponding deep-water trenches.

The boundaries of lithospheric plates, both in places of their rupture and in places of collision, are moving parts of the earth's crust where the majority is active volcanoes where earthquakes are frequent. These areas, which are areas of new folding, form the seismic belts of the Earth.

The farther from the boundaries of the mobile sections to the center of the plate, the more stable the sections of the earth's crust become. Moscow, for example, is located in the center of the Eurasian plate, and its territory is considered quite stable.

Volcanism- a set of processes and phenomena caused by the introduction of magma into the earth's crust and its outpouring to the surface.

From deep magma chambers, lava, hot gases, water vapor and rock fragments erupt onto the earth.

Three types of volcanic eruptions are distinguished depending on the conditions and ways of penetration of magma to the surface.

areal eruptions led to the formation of vast lava plateaus. The largest of them are the Deccan Plateau on the Hindustan Peninsula and the Columbian Plateau.

fissure eruptions occur along cracks sometimes of great length. At present, volcanism of this type is manifested in Iceland and at the bottom of the oceans in the region of mid-ocean ridges.

Eruptions of the central type are connected to certain areas, usually at the intersection of two faults, and occur along a relatively narrow channel called vent. This is the most common type. Volcanoes that form during such eruptions are called layered or stratovolcanoes. They look like a cone-shaped mountain, on top of which there is a bowl-shaped depression - crater.

Examples of such volcanoes: Kilimanjaro in Africa, Klyuchevskaya Sopka, Fujiyama, Etna, Hekla in Eurasia.

Pacific Ring of Fire. About two-thirds of the Earth's volcanoes are concentrated on islands and coasts. Pacific Ocean. Most powerful eruptions Volcanoes and earthquakes took place in this region: San Francisco (1906), Tokyo (1923), Chile (1960), Mexico City (1985).

Sakhalin Island, the Kamchatka Peninsula and the Kuril Islands, located in the very east of our country, are links in this ring.

In total, there are 130 extinct volcanoes and 36 active. The largest volcano is Klyuchevskaya Sopka. There are 39 volcanoes on the Kuril Islands. These places are characterized by destructive earthquakes, and the surrounding seas are characterized by seaquakes, typhoons, volcanoes and tsunamis.

Tsunami translated from Japanese - "wave in the bay." These are gigantic waves generated by underwater volcanoes, earthquakes or seaquakes. In the open ocean, they are almost invisible to ships. But when the path of the tsunami blocks the mainland and the islands, the wave hits the land from a height of up to 20 meters.

Hot Springs and geysers also associated with volcanism. In Kamchatka, in the famous Valley of Geysers, there are 22 large geysers.

earthquakes are also a manifestation of endogenous terrestrial processes and represent sudden underground shocks, tremors and displacements of layers and blocks of the earth's crust.

At seismic stations, scientists study these terrible natural phenomena, using special instruments, looking for ways to predict them. One of these devices is seismograph- was invented at the beginning of the 20th century. Russian scientist B.V. Golitsyn. The name of the device comes from the Greek words seismos- "fluctuation" graphs- "food". It reflects its purpose - to record the vibrations of the Earth.

earthquakes may be of different strength. Scientists agreed to determine this force on the international 12-point Mercalli scale and the 9-point Richter scale, taking into account the impact of an earthquake on a person and the degree of damage to buildings and changes in the Earth's topography (Table 7.2).

The relief of the 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 - the movements of lithospheric plates, fractures of the earth's crust, intrusions of mantle matter into the earth's crust and its outpouring to 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 the relief of the continents. Under the influence of weathering forces, even the hardest rocks are destroyed and bizarre forms are formed (5.3, 5.4). (Think about why.) Physical weathering of rocks is most pronounced 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. Deepening of river valleys takes place, deep gorges (canyons) are formed in the mountains.

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

Minerals. The earth's crust of our planet contains huge and diverse riches - rocks and minerals that people have been extracting and using for a long time.

Among the mineral wealth that is extracted from the earth's crust and used in the economy, there are more than 200 various kinds mineral. The placement of mineral deposits is subject to natural laws.

Combustible (fuel) fossils (Remember what they include.) Are of sedimentary origin. They play an important role in the economy. Most of them are located in Eurasia and in 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.)

Deposits of ore minerals are formed both in sedimentary and igneous rocks. Most of the ore deposits are associated with platform foundations and ledges of crystalline rocks to the surface. These are platform shields, as well as folded areas of the earth's crust. In such areas, huge ore belts are often formed, for example, a belt of tin deposits in Eurasia, platinum, chromites, uranium in South Africa, and a copper-bearing belt in the Andes (5.6, 5.7, 5.8, 5.9).

Relief features affect the distribution of the population. 4/5 of the world's population lives in lowlands and uplands 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, for example hard coal and iron ore, etc.

The earth's surface is subject to the active influence of various natural and anthropogenic processes. The leading role in this complex is played by geomorphological (relief-forming) processes responsible for changes in the basis of the landscape - relief. The most important is the assessment of the action of these processes over the past 150–200 years, which determines modern tendencies development of the natural environment.

Relief formation (geomorphogenesis) is divided into endogenous and exogenous processes. Endogenous processes operate in the internal and use the energy accumulated in its depths. Among them are tectonic, due to 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 small (millimeters, centimeters per year). An exception is sharp movements along faults that cause 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 Earth's rotation around its own axis. Depending on the nature of the flow, they are divided into fluvial, gravitational, cryogenic, glacial, nival, coastal (coastal-wave), biogenic, karst and eolian. Anthropogenic processes associated with human economic activity represent a special genus. These are the most dynamic processes of relief formation, the role of which in global geomorphogenesis has sharply increased 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 channels, floodplains and deltas of numerous rivers. The activity of temporary streams leads to the formation of ravines, gullies, potholes, furrows (erosion processes), alluvial fans. Flows of rain and melt water erode the soil on the slopes and cause the accumulation of eroded material (deluvium) at their foot.

Gravitational processes are typical for mountainous regions, but are also common on steep, washed-out 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), solifluction (the flow of thawed soils in areas permafrost).
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, heaving of soils, thermokarst (thawing ground ice), thermal erosion (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 the mountainous and polar regions. As a result of exaration, an alpine-type relief is formed (troughs, cirques, carlings), glacial accumulation forms moraine complexes.

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

Biogenic processes are manifested mainly in wetlands, which are abundant in Western Siberia, in the north of the European part of Russia, in areas in the east of the country. Here there is an active accumulation of peat, which is expressed in the formation of gently sloping interfluves and hummocky microrelief.

Areas of distribution of soluble rocks (limestone, dolomite, gypsum, rock salt) are characterized by karst processes. Here arise and continue to develop various forms surface karst (craters, karrs, fields, etc.) and deep (caves, abysses). Often they are accompanied by failures that have catastrophic consequences.
Eolian processes are sporadically distributed, mainly in places of accumulation of large sandy massifs, which are in arid or subarid climate. Barchan ridges and dunes created in previous eras are formed or continue to develop there. In the southern arid regions, deflation (blowing) of the upper fertile layer periodically takes place.

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

At the bottom of the ocean, the accumulation of matter coming from the land occurs, redistribution and erosion of sediments by currents, among which the most significant role is played by turbidity flows concentrating in submarine canyons. In the eastern sector of the Arctic, thermal abrasion of icy deposits that form 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. Mining is accompanied by the formation of different sizes of negative landforms (quarries) and positive ones (dumps, 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 belt location various varieties these processes. In the mountains, a vertical zonality of geomorphogenesis is outlined, which is especially pronounced in the southern high-mountain regions (Caucasus, Altai). In the lower belt of these mountainous regions, as a rule, fluvial processes (erosion, planar washout, mudflow and accumulation) predominate. In the middle belt, gravitational and, to some extent, nival-cryogenic processes acquire significant significance. Nival-glacial processes dominate in the upper, high-alpine belt.

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

The zoning of exomorphogenesis on the plains is subject to global climatic patterns, so it has a latitudinal character. 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 distributed, also falls under the influence of cryogenesis, although fluvial processes also play an important role in it. In zones of mixed and broad-leaved forests, as a rule, fluvial processes predominate. In the steppe and forest-steppe zones, in addition to fluvial processes, anthropogenic erosion is intensively developed and deflation is periodically manifested. Aeolian processes are most widespread, with a subordinate erosion value.

separate ridges and intermountain depressions - in the mountains, uplands and lowlands - on the plains. Mesoforms occupy square kilometers and their first tens. These are ravines, beams, moraine

hills, dunes, etc.

Microforms - karst funnels, riverbed ramparts 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 diverse, ever-increasing economic activity person.

Academician I.P. Gerasimov, who headed the Institute of Geography of the Academy of Sciences from 1951 to 1985

USSR, 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).

Geotectures (Greek ge - Earth, Latin tectura - cover) are the largest landforms of the Earth, due to planetary geophysical and cosmic processes. Geotectures 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, oceanic basins and mid-ocean ridges in the ocean, and transitional zones between continents and oceans. The formation of modern geotectures began at the turn of the Paleozoic and Mesozoic and coincides with the geomorphological stage of the Earth's development.

Morphostructures (Greek morphe - form, Latin structura - structure) - large landforms - 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; geological structures are clearly reflected in their structure. The formation of morphostructures corresponds to the neotectonic stage of the Earth's development.

Morphosculptures(Greek morphe - form, lat. sculptura - sculpture, carving) - these are relatively small (meso-, micro-, etc.) relief forms, which owe their origin primarily to exogenous processes that are closely related to modern and past climatic conditions. Age of morphosculptures for the most part restricted 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 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, that arose mainly under the influence of exogenous processes subject to the law of climatic zoning.

Combinations of landforms that are similar in appearance, internal structure, origin and development conditions, regularly repeating in a certain territory, form morphogenetic landform types(for example, hilly moraine plains, ridged valley-ravine erosional plains, flat outwash plains, etc.).

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

2.2. Relief-forming processes

The starting position of geomorphology is the idea that the relief is formed as a result of the interaction of endogenous and exogenous processes. The source of energy for internal processes is the energy generated in the bowels of the Earth and due to the chemical-density gravitational differentiation of matter, the decay of radioactive elements, and during the deceleration of the Earth's rotation (rotational energy). driving force endogenous processes is a large circulation of matter in the mantle and lithosphere, resulting in heating and subsequent cooling of matter. This is inevitably accompanied by a change in its volume and the stresses arising in connection with this, which, in turn, lead to various horizontal and vertical displacements of the earth's crust and the lithosphere as a whole. Such

movements are called tectonic movements. With they are associated with disturbances in the conditions of occurrence of rock layers and the formation of the main features of the modern relief of the Earth, reflected in geotectures and morphostructures. Endogenous processes include imagmatism, associated both with the primary heating of the mantle and crust, and with temperature fluctuations in the earth's crust, arising due to the friction of the layers during tectonic movements.

Exogenous processes occur on the surface of the Earth. Almost all of them are due to the energy of the Sun (except slope ones due to 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 as directly ( on the slopes), and indirectly, through other exogenous processes. Therefore, gravity can also be included among the agents of relief formation. Anthropogenic processes stand out in a special group of exogenous processes.

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

Endogenous processes are tectonic movements imagmatism. Tectonic movements are characterized by different directions and intensity in time and space. In direction relative to the Earth's surface, vertical (radial) and horizontal (tangential) movements are distinguished, in direction - reversible (oscillatory) and irreversible, in the speed of manifestation - fast (earthquakes) and slow

(secular), according to the time of manifestation - movements of the distant geological past, the latest

(Oligocene-Quaternary) and modern. All types of geotectonic movements are interconnected. Thus, the division of tectonic movements into vertical and horizontal is largely arbitrary.

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

Under vertical oscillatory movements the earth's crust understand constants,

ubiquitous, reversible movements of different scales in area and amplitude, which do not create folded structures. AT foreign literature they are called epeirogenic (Greek epeiros - mainland, dry land, genesis - origin). The relief-forming role of these movements is enormous. Vertical movements of a higher order underlie the formation of planetary landforms on the earth's surface. They cause marine transgressions and regressions and thus control the areas of land and oceans and their configuration.

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

Slow vertical movements different sign occurred in the geological past and continue to the present. Now Scandinavia is slowly rising, and the coast North Sea, on the contrary, falls, which is why in Holland, in order to escape 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 the vertical ones, there are everywhere and constantly horizontal movement, which play a leading role in the development and formation, first of all, of the largest landforms. Thus, the opening of the oceans and the movement of the continents and, accordingly, a change in their areas and outlines are associated with continental rifts and horizontal movements of blocks of the lithosphere to the sides. A young giant expanding graben, i.e. a rift, the future ocean, is considered to be the basin of the Red Sea, the sides of which are displaced by several millimeters per year from the axial zone to different sides. The collision of continental plates, compression and crowding of the sedimentary and volcanic strata of the Tethys Ocean, especially against the Arabian ledge and the Hindustan block of Gondwana, explain 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 deformations of rock layers, leading to two types of dislocations: folded (plicative)– bending of the layers without disturbing their continuity and discontinuous (disjunctive), along

which, as a rule, the blocks of the bark move in the vertical and horizontal directions. Both types of dislocations are characteristic of the mobile belts of the Earth, where mountains are formed. Therefore, tectonic movements leading to disruption of the primary horizontal occurrence of rocks, i.e. to the formation of dislocations, called orogenic, creating mountains (Greek oros - mountain, genesis - origin). Folded and discontinuous dislocations are manifested in the relief.

Folded dislocations are pronounced in geosynclines and young epigeosynclinal areas and are practically absent in the platform mantle. Relatively simple convex folds - anticlines usually form low folded ridges (Tersky, Sunzha ridges in the North Caucasus), and concave folds - synclines - intermountain and foothill depressions.

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

The largest and most complex folds form epigeosynclinal mountainous countries (the Caucasus, the 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 one and, due to the law of isostasy, has buoyancy.

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

Rifts are the largest forms of the Earth's relief, caused by discontinuous tectonics.

- 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 undulating swellings, which, in turn, were formed under the influence of ascending mantle flows. They are characterized by a decrease in the thickness of the earth's crust and the lithosphere as a whole, high seismicity, volcanic activity, and a high heat flux. There are rifts both at the bottom of the oceans and on the continents.

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

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

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

Faults often determine the outlines of the coastline of the continents on the 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 Gondwanan continents.

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

Folded and discontinuous 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 are different in shape and size. Large intrusions, especially elongated batholiths, stretch for hundreds of kilometers (the Chilean batholith in the Andes has a length of more than 1300 km, the batholith in the Cordilleras of Canada is more than 2000 km), reach a width of up to 100 km and a thickness of up to 10 km. Batholiths cause disturbances in the bedding of the overlying rocks. These disturbances can be both folded and discontinuous. Batholiths, usually composed of granites, form the central uplifts of many mountain-folded regions. As a result of subsequent denudation, they often find themselves on the surface, composing massive, hard-to-reach axial mountain ranges (Sierra Nevada, Coast Range in Canada).

Intrusions in the form of domed or loaf-shaped laccoliths give the same shape to the overlying rocks and form groups or single mountains, such as, for example, Zheleznaya, Mashuk, Beshtau and others in the Pyatigorsk region in the North Caucasus, Mount Ayu-Dag in

Crimea. The exposed intrusions are the Khibiny and neighboring massifs with a height of more than

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

A peculiar relief creates effusive magmatism, or volcanism. Depending on the nature of the outlet openings, areal, linear and central eruptions are distinguished. Areal and linear eruptions dominated in the geological past. They formed the bed of the oceans, vast lava plateaus and highlands (the Columbian Plateau, the Fraser Plateau, the Mexican and Ethiopian Highlands, etc.). In historical times, significant outpourings of lavas occurred in Iceland, on the Hawaiian Islands, they are also very characteristic of the mid-ocean ridges.

In the modern geological era on the continents, the most common eruptions of the central type, when magma rises through a narrow channel, which usually occurs 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 a crater. The shape of volcanoes depends on the composition of the magma, its viscosity, and the rate at which it solidifies. Many volcanoes consist of loose eruptions interbedded with hardened lava. These are Klyuchevskaya Sopka, Fujiyama, Elbrus, Ararat, Vesuvius, Krakatau, Chimbaraso and other volcanoes.

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

For fading places volcanic activity(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.

To endogenous processes also include earthquakes - sudden underground shocks, tremors

and displacement of layers and blocks of the earth's crust. Earthquake sources are confined to fault zones. In most cases, the centers of earthquakes, i.e. hypocenters are located at a depth of the first tens

kilometers in the earth's crust. However, sometimes they are located in the upper mantle at a depth of up to 600–700 km, for example, along the coast of the Pacific Ocean, 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, displacement in the horizontal direction. The greatest damage is observed at the epicenter of earthquakes located above the hypocenter. The intensity of earthquakes is estimated on a twelve-point scale based on the deformation of the Earth's layers and the degree of damage to buildings. Every year, hundreds of thousands of earthquakes are recorded on Earth, so we live on a restless planet. During catastrophic earthquakes, the terrain changes in a matter of seconds, collapses and landslides occur in the mountains, cities are destroyed, people die. Earthquakes on the coasts and the bottom of the oceans cause waves - tsunamis. The catastrophic earthquakes of recent decades include 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 general, endogenous processes play a constructive role in relation to the relief: during tectonic uplifts of any genesis, the Earth's surface rises, the relief experiences an upward development, its marks increase, which contributes to the accumulation of masses in the upper ("relief") part of the earth's crust. Obviously, endogenous processes control the nature and intensity of exogenous processes.