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. Diverse, ever-increasing human economic activity also belongs to exogenous processes.

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 different 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.) landforms, which owe their origin primarily to exogenous processes that are closely related to modern and past climatic conditions. The age of the 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 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 an big cycle matter in the mantle and lithosphere, resulting in heating and subsequent cooling of the 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 extension 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. V 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 of different signs occurred in the geological past and continue at the present time. 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 of, first of all, 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 Red Sea basin, 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, mountains 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, eruptions of the central type are most common, when magma rises along 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 places of attenuation of 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 Pacific Ocean, in the Caribbean 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 relief 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 undergoes 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.

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 are of three types: oceanic ridges (along which the mantle material rises to the surface and a new seabed forms), 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) . So, 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 was put forward 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 Pangaea (translated from Greek ʼʼthe whole Earthʼʼ). In the next 70 million years, Pangea split into two continents: Laurasia, which included North America and Eurasia (without 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 collision zone of Eurasia with the latter, the most high mountains on the planet (Himalayas). Today 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, the layers of which are bent downwards, is commonly 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.

Given the dependence 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).

Given the dependence on size, they form separate mountain ranges (for example, table mountains in Europe) or mountain systems and countries (for example, Altai, Tien Shan).

In these mountains, along with grabens and horsts, there are also folded massifs; in this regard, 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 - there is an ʼʼdivingʼʼ of one plate (more often with oceanic earth's crust) under another (more often with continental or transitional type of earth's crust). As a result of this ʼʼdivingʼʼ, 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.

Considering the dependence on the conditions and ways of magma penetration to the surface, three types of volcanic eruptions are distinguished.

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. Today, volcanism of this type occurs in Iceland and at the bottom of the oceans in the region of the mid-ocean ridges.

Eruptions of the central type are associated with certain areas, as a rule, at the intersection of two faults, and occur along a relatively narrow channel, which is commonly called vent. This is the most common type. Volcanoes that form during such eruptions are called layered or stratovolcanoes.Οʜᴎ have the appearance of a cone-shaped mountain, on the 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 ʼʼring of fireʼʼ. About two thirds of the Earth's volcanoes are concentrated on the islands and shores of the Pacific Ocean. The most powerful volcanic eruptions 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 volcanoes in Kamchatka. 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 - ʼʼwave in the bayʼʼ. 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.

The 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 are 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- ʼʼoscillationʼʼ, graphs- ʼʼfoodʼʼ. It reflects its purpose - to record the vibrations of the Earth.

earthquakes are 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).

Table 7.2

Relief-forming processes - concept and types. Classification and features of the category "Relief-forming processes" 2017, 2018.

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 ). So, 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 put 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 highest mountains on the planet (the Himalayas) arose. 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, table mountains 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 on which there are most 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 the islands and shores of the Pacific Ocean. The most powerful volcanic eruptions 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 volcanoes in Kamchatka. 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.

The 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 Earth is the result of a constantly ongoing antagonistic interaction of endogenous and exogenous processes and, because of this, is in a state of constant transformation. Endogenous processes - tectonic movements of the earth's crust and volcanism - play a leading role in this. They create the main irregularities of the earth's surface, which are then subjected to the destructive action of external forces - water, wind, ice, which, obeying the laws of gravity, tend to destroy, even out the rises that have arisen, filling the depressions with destruction products. The action of these exogenous processes leads in general to the leveling of the earth's surface. However, as a result of the constant renewal of endogenous processes, irregularities in the Earth's relief arise again and again. But the influence of external processes is also contradictory, since they lead initially to the dismemberment of the earth's surface and only then to its leveling.

The development of exogenous relief-forming processes is of great importance. It is expressed not only in the destruction of the earth's surface, but also in the formation of continental sedimentary formations, which, being deposited on the surface, form the forms of its relief, which determines the closest connection between the development of the relief and the formation of the sedimentary cover.

endogenous processes. The most important role in the formation of the Earth's relief is played by processes of formation of the earth's crust and tectonic movements. They are associated with the largest forms of the earth's surface. Tectonic movements lead to vertical and horizontal movements of large parts of the crust, to the formation of large folds, expressed in relief, to blocky movements along ruptures, to stretching of the crust - rifting. Of great importance for the formation of the relief is the oscillatory nature of the movements of the earth's crust - the alternation of ups and downs, as well as their uneven manifestation in space and time.

The mountainous relief on the Earth's surface corresponds to tectonically active areas of uplifts, zones of high mobility of the earth's crust. major plains correspond to tectonically stable areas - continental and oceanic platforms. As a result, the basis for the distribution of relief types on the earth's surface is the tectonic zonality of the relief, due to the historical and geological development of the earth's crust, and above all the history of the latest Neogene-Quaternary movements.

Volcanism is closely related to tectonics. Volcanic processes They do not appear everywhere, but in some places they play a decisive role in the formation of the relief.

Exogenous processes usually form smaller forms that complicate the structure of endogenous forms. However, for practical geomorphology, the exogenous relief is of particular importance - both because of its significance for practice and because it reflects the development of larger forms. Therefore, close attention is paid to seemingly secondary exogenous processes. The latter are divided into three groups geological processes- weathering, denudation and accumulation.

Weathering- the process of destruction and transformation of the surface layer of rocks under the influence of the thermodynamic and physico-chemical conditions of the land surface. It leads to loosening of the outer layer of rocks, preparing them for movement under the action of external forces.

Denudation(lat. denudatio - outcrop) is a set of processes for the removal of weathering products and the direct destruction of rocks by denudation agents. Denudation, exposing bedrock, causes further development weathering. Its (the most important consequence is the destruction (destruction) of the earth's surface and the formation of a denudation, or worked out relief. On the other hand, moving masses of clastic material, denudation processes are replaced by its deposition as soon as suitable conditions are created for this. The deposition of destruction products is called accumulation. At the same time, on the one hand, deposits arise, their special genetic types, on the other hand, accumulative landforms are formed. Thus, denudation and accumulation are always two sides of a single exogenous process, although they are often denoted by different terms.

Denudation-accumulation processes differ both in the nature of the forces and agents that cause the movement of mineral masses, and in the nature of the activity of these agents. These include: 1. The group of gravitational processes - the displacement of mineral masses along the slopes under the direct influence of gravity. 2. Deluvial process - planar flushing with thin, channelless jets of water. 3. Fluvial process - the activity of channel water flows. 4. Glacial (glacial) process - the activity of moving glaciers. 5. Fluvioglacial process - the activity of melted glacial waters. 6. Karst process - the removal of a chemically dissolved substance by groundwater. 7. Suffusion - the removal of mechanically suspended particles by groundwater. 8. Wave-surf process - the activity of wave-surf along the shores of seas and lakes. 9. Wind (eolian) process-activity of the wind. 10. Anthropogenic or technogenic process - the movement of mineral masses by technical means.

In addition, the specific processes of destruction of rocks that accompany many denudation processes are corrosion - the mechanical action of mineral particles drawn by water, ice or wind, and corrosion - partial dissolution of a substance on the surface of rocks.

A wide variety of exogenous processes largely determines the huge variety of landforms on Earth. However, not only relief-forming processes determine the shape of the relief. The results of exogenous processes depend on a number of other geological, geographical and other factors.

Geological and geographical factors of relief formation

These factors of relief formation themselves do not create relief forms, but significantly affect its formation. They determine the environment in which the processes take place, the intensity of their manifestation and the very complex of exogenous processes. These factors include tectonic movements, geological structure of the area, climatic conditions, vegetation, mountainous and flat conditions. Time plays an important role - the protection and staging of processes, changes in conditions over time. An ever-increasing role belongs to the people economic activity person.

Tectonic movements cause a change in the height and slopes of the earth's surface, thereby causing a change in the situation and the course of external processes. They intensively influence the activity of water flows and glaciers, the course of slope processes. Sharp tectonic shifts, expressed by earthquakes, lead to catastrophic manifestations of gravitational processes - mountain collapses, landslides.

The role of the tectonic factor is also associated with the distribution of mountains and plains on Earth, which in themselves have big influence on the course of external processes and the relief produced by them. For example, the morphology of river valleys in mountainous and lowland countries is sharply different.

Influence of the geological structure. The earth's crust is extremely heterogeneous in its structure. Its constituent rocks vary greatly in their resistance to weathering and denudation. In addition to the inherent properties of rocks, their stability to a very large extent depends on the forms and conditions of occurrence. The nature of the alternation and thickness of the layers, the size of geological bodies, their shape and tectonic dislocations influence. Breaks, small folds, zones of increased fracturing greatly weaken the resistance of rocks. In weakened zones, as well as at outcrops of weak, unstable rocks, destruction processes develop faster, and here various depressions appear in the relief. Strong rocks with high anti-denudation resistance, on the contrary, are destroyed more slowly, forming various ledges. This phenomenon is called selective, or electoral denudation. As a result, even under the action of any one exogenous process, an extremely large variety of sculptural forms arises.

The effect of selective denudation leads to the formation of a large group of forms of structural and structurally determined relief (Fig. 1).

Beneath the structural relief relief should be understood as directly reflecting the forms of geological bodies. In its occurrence, a large role is played by powerful strata of stable rocks, forming the so-called armor layers, delaying denudation. Armored relief is formed on horizontally occurring rocks with an upper layer resistant to denudation. layered plateaus(see fig. 1, A) Ust-Urt plateau type. In areas of gently sloping monoclinal occurrence of layers, the preparation by denudation of stable layers leads to the formation of a relief of asymmetric ridges or cuest(see fig. 1, B); an example is the cuestas of the second ridge of the Crimean mountains. At a steeper (over 25°) dip of monoclinal formations, monoclinal ridges(see fig. 1 ,V). Small forms of structural relief are represented by layered ledges and structural terraces on slopes (see Fig. I, D), anticlinal vaults, dikes prepared by denudation.

Structural relief reflects the structure of the earth's crust not directly, but indirectly. Fracture valleys belong to this type of relief (see Fig. 1, D) elevations on granite massifs (see Fig. 1, E) and others. In addition, highlighted lithogenetic relief, representing usually smaller forms

we are characteristic of certain types of rocks. Such, for example, are the remains-idols of the Eocene limestones of Bakhchisaray.

The most important factor in relief formation is the climate. Climatic conditions determine the manifestation of certain exogenous processes, their intensity and expression in the relief. The most important external processes, such as weathering, the activity of ice, wind, water flows, are closely related to climate. Therefore, in different climatic conditions different forms of relief appear. The largest changes in the Earth's climate in the past, its sharp cooling led to the accumulation of colossal masses of water on land in the form of glaciers and thereby caused general eustatic lowering of the ocean level, which also influenced the development of the relief. The nature of the vegetation, which strongly influences relief formation, also depends on the climate. A dense sod cover prevents planar washout and reduces the flow of detrital material into rivers and lakes. Forests delay the development of ravines, the destruction of slopes.

In the most in general terms climate depends on the amount of heat received by the Earth's surface from the sun, i.e. on latitude

terrain and its height above sea level. In this regard, in the distribution of climate, latitudinal and vertical zonality is observed, which is reflected in the relief. Therefore, in the distribution of exogenous landforms, there is a complex climatic zoning.

The most important climate types are humid, nival, polar and arid.

Humid climate characterized by a sharp excess of precipitation over evaporation and seepage, which ensures a constant runoff of surface water. Characterized by the dominance of chemical and organic weathering, a large role in the development of the relief of water flows and planar washout, the rich development of vegetation (forests), which delays denudation. Fluvial landforms are widespread - river valleys and ravines. The humid climate is confined to the middle and equatorial latitudes.

Nival climate characterized by precipitation in the solid phase in the form of snow, the accumulation of which leads to the formation of glaciers. Physical weathering and the glacial process dominate. The nival climate is confined to the polar regions. In connection with vertical zonality, it is also developed in mountainous countries.

polar climate characterized by great dryness and low temperatures in winter, which, with a weak development of snow cover, leads to the formation of permafrost. Physical weathering, especially frosty weathering, and specific permafrost and gravitational processes predominate (see chapters III and IV). The polar climate is typical for Northern Asia and Eastern Siberia.

Arid climate characterized by a sharp deficit of moisture, so water runoff occurs extremely rarely. Vegetation is poorly developed. Physical weathering and the wind process predominate, creating the characteristic eolian relief of deserts. The arid climate is confined to tropical zones, but within large continents it shifts significantly to temperate latitudes(Tibet, Mongolia).

Of great geomorphological importance is the transitional semiarid climate, characterized by periodic rain showers, which determine a significant role various kinds water runoff. This is the climate of arid steppes, savannahs.

The latitudinal zonality of the climate is disturbed by vertical zonality due to the altitude of the relief. Climatic zoning is also complicated by the distribution of land and sea. V historical development Earth climatic zones repeatedly shifted, in connection with which there is a combination of different climatic types of relief in one area. So, for example, in Northern Europe, landforms created by Quaternary glaciers are widely developed, while at present it is

zone of humid climate, dominated by fluvial processes.

A large number of factors and processes of relief formation, the variety of their combinations, which change significantly in time and space, determine the richness and diversity of relief forms that is inherent in the Earth.

So far, we have considered internal relief-forming factors, such as movements of the earth's crust, folding, etc. These processes are due to the action internal energy Earth. As a result, large landforms such as mountains and plains are created. In the lesson, you will learn how the relief was formed and continues to form under the influence of external geological processes.

Other forces are also working on the destruction of rocks - chemical. Seeping through cracks, water gradually dissolves rocks (See Fig. 3).

Rice. 3. Dissolution of rocks

The dissolving power of water increases with the content of various gases in it. Some rocks (granite, sandstone) do not dissolve in water, others (limestone, gypsum) dissolve very intensively. If water penetrates along cracks into layers of soluble rocks, then these cracks expand. In those places where water-soluble rocks are close to the surface, numerous sinkholes, funnels and depressions are observed on it. This karst landforms(see Fig. 4).

Rice. 4. Karst landforms

Karst is the process of dissolution of rocks.

Karst landforms are developed on the East European Plain, Cis-Urals, the Urals and the Caucasus.

Rocks can also be destroyed as a result of the vital activity of living organisms (saxifrage plants, etc.). This biological weathering.

Simultaneously with the destruction processes, the destruction products are transferred to lower areas, thus, the relief is smoothed out.

Consider how the Quaternary glaciation shaped the modern relief of our country. Glaciers have survived to this day only on the Arctic islands and on the highest peaks of Russia. (See Fig. 5).

Rice. 5. Glaciers in the Caucasus Mountains ()

Going down steep slopes, glaciers form a special, glacial relief. Such a relief is common in Russia and where there are no modern glaciers - in the northern parts of East European and West Siberian Plains. This is the result of an ancient glaciation that arose in the Quaternary era due to a cooling of the climate. (See Fig. 6).

Rice. 6. Territory of ancient glaciers

The largest centers of glaciation at that time were the Scandinavian mountains, the Polar Urals, the islands New Earth, mountains of the Taimyr Peninsula. The thickness of the ice on the Scandinavian and Kola peninsulas reached 3 kilometers.

Glaciation occurred more than once. It was advancing on the territory of our plains in several waves. Scientists believe that there were about 3-4 glaciations, which were replaced by interglacial epochs. The last ice age ended about 10,000 years ago. The most significant was the glaciation on the East European Plain, where the southern edge of the glacier reached 48º-50º N. sh.

To the south, the amount of precipitation decreased, so in Western Siberia glaciation reached only 60º N. sh., and east of the Yenisei, due to the small amount of snow, it was even less.

In the centers of glaciation, from where the ancient glaciers moved, there are widespread traces of activity in the form of special relief forms - Sheep foreheads. These are ledges of rocks with scratches and scars on the surface (slopes facing towards the movement of the glacier are gentle, and the opposite ones are steep) (See Fig. 7).

Rice. 7. Lamb forehead

Under the influence of their own weight, glaciers spread far from the center of their formation. Along the way, they smoothed out the terrain. A characteristic glacial relief is observed in Russia on the territory of the Kola Peninsula, the Timan Ridge, the Republic of Karelia. The moving glacier scraped soft loose rocks and even large, hard debris from the surface. Clay and hard rocks frozen into the ice formed moraine(deposits of rock fragments formed by glaciers during their movement and melting). These rocks were deposited in more southerly regions where the glacier was melting. As a result, moraine hills and even entire moraine plains were formed - Valdai, Smolensk-Moscow.

Rice. 8. Moraine formation

When the climate did not change for a long time, the glacier stopped in place and single moraines accumulated along its edge. In the relief, they are represented by curved rows tens or sometimes even hundreds of kilometers long, for example, Northern Uvaly on the East European Plain (see fig. 8).

During the melting of glaciers, streams of melt water were formed, which washed over the moraine, therefore, in the areas of distribution of glacial hills and ridges, and especially along the edge of the glacier, water-glacial sediments accumulated. Sandy flat plains that arose along the outskirts of a melting glacier are called - outwash(from German "zander" - sand). Examples of outwash plains are the Meshcherskaya lowland, the Upper Volga, Vyatka-Kama lowland (see fig. 9).

Rice. 9. Formation of outwash plains

Among the flat-low hills, water-glacial landforms are widespread, ozes(from Swedish "oz" - ridge). This narrow ridges, up to 30 meters high and up to several tens of kilometers long, shaped like railway embankments. They were formed as a result of settling on the surface of loose sediments formed by rivers flowing along the surface of glaciers. (see fig. 10).

Rice. 10. Formation of lakes

All water flowing on land, under the influence of gravity, also forms a relief. Permanent streams - rivers - form river valleys. The formation of ravines is associated with temporary streams formed after heavy rains. (see fig. 11).

Rice. 11. Ravine

Overgrown, the ravine turns into a beam. The slopes of uplands (Central Russian, Volga, etc.) have the most developed ravine network. Well-developed river valleys are characteristic of rivers flowing outside the boundaries of the last glaciations. Flowing waters not only destroy rocks, but also accumulate river sediments - pebbles, gravel, sand and silt (see fig. 12).

Rice. 12. Accumulation of river sediment

They consist of river floodplains, stretching in strips along the riverbeds. (see fig. 13).

Rice. 13. The structure of the river valley

Sometimes the latitude of the floodplains varies from 1.5 to 60 km (for example, near the Volga) and depends on the size of the rivers (see Fig. 14).

Rice. 14. The width of the Volga in various sections

Along the river valleys there are traditional places of human settlement and a special type of economic activity is being formed - animal husbandry in floodplain meadows.

On the lowlands, experiencing slow tectonic subsidence, there are extensive floods of rivers and wanderings of their channels. As a result, plains are formed, built by river sediments. This relief is most common in the south of Western Siberia. (see fig. 15).

Rice. 15. Western Siberia

There are two types of erosion - lateral and bottom. Deep erosion is aimed at cutting flows into the depth and prevails near mountain rivers and rivers of plateaus, which is why deep river valleys with steep slopes are formed here. Lateral erosion is aimed at erosion of the banks and is typical for lowland rivers. Speaking about the impact of water on the relief, we can also consider the impact of the sea. When the seas advance on the flooded land, sedimentary rocks accumulate in horizontal layers. The surface of the plains, from which the sea retreated long ago, is greatly changed by flowing waters, wind, glaciers (see fig. 16).

Rice. 16. Retreat of the sea

The plains, relatively recently abandoned by the sea, have a relatively flat relief. In Russia, this is the Caspian lowland, as well as many flat areas along the shores of the Arctic Ocean, part of the low plains of Ciscaucasia.

The activity of the wind also creates certain landforms, which are called eolian. Aeolian landforms are formed in open spaces. In such conditions, the wind carries a large amount of sand and dust. Often a small bush is a sufficient barrier, the wind speed decreases, and the sand falls to the ground. Thus, at first small, and then large sandy hills are formed - dunes and dunes. In terms of plan, the dune has the shape of a crescent, with its convex side facing the wind. As the direction of the wind changes, so does the orientation of the dune. Wind-related landforms are distributed mainly on the Caspian lowland (dunes), on the Baltic coast (dunes) (see fig. 17).

Rice. 17. Formation of a dune

A lot of small debris and sand are blown away by the wind from the bare mountain peaks. Many of the grains of sand he carries out again hit the rocks and contribute to their destruction. You can observe bizarre weathering figures - remnants(see fig. 18).

Rice. 18. Remains - bizarre landforms

The formation of special species - forests - is associated with the activity of the wind. - loose, porous, dusty rock (see fig. 19).

Rice. 19. Forest

Forests cover large areas in southern parts East European and West Siberian plains, as well as in the Lena River basin, where there were no ancient glaciers (see fig. 20).

Rice. 20. Russian territories covered with forest (shown in yellow)

It is believed that the formation of the forest is associated with winding dust and strong winds. On the forest, the most fertile soils, however, it is easily washed out by water and the deepest ravines appear in it.

1. The formation of the relief occurs under the influence of both external and internal forces.
2. Internal forces create large landforms, and external forces destroy them, transforming them into smaller ones.
3. Under the influence of external forces, both destructive and creative work is carried out.

Bibliography

1. Geography of Russia. Nature. Population. 1 hour Grade 8 / V.P. Dronov, I.I. Barinova, V.Ya Rom, A.A. Lobzhanidze.
2. V.B. Pyatunin, E.A. Customs. Geography of Russia. Nature. Population. 8th grade.
3. Atlas. Geography of Russia. population and economy. - M.: Bustard, 2012.
4. V.P. Dronov, L.E. Savelyeva. UMK (educational-methodical set) "SPHERES". Textbook “Russia: nature, population, economy. 8th grade". Atlas.

1. The influence of internal and external processes on the formation of relief ().
2. Outside forces that change the relief. Weathering. ().
3. weathering().
4. Glaciation in Russia ().
5. Physics of dunes, or how sand waves are formed ().

Homework

1. Is the statement true: “Weathering is the process of destruction of rocks under the influence of wind”?
2. Under the influence of what forces (external or internal) did the peaks of the Caucasus Mountains and Altai acquire a pointed shape?