External forces changing the surface of the earth

14.10.2019

Processes that form the relief. It would be a mistake to assume that only the formation of tectonic structures in the distant geological past influenced the appearance of the modern relief. Like all other components of nature, terrain is constantly changing. Even in such stable areas earth's crust, like platforms, there is a constant change in surface shapes.

Modern relief-forming processes can be divided into two groups: internal (endogenous), caused by movements of the earth's crust (they are called neotectonic or recent), and external (exogenous).

The latest tectonic movements of the earth's crust can manifest themselves both in the mountains and in flat platform areas. In areas of ancient folded structures, where the earth's crust has lost its plasticity, become rigid and rocks have lost the ability to bend into folds, powerful faults and faults have formed under the influence of recent tectonic movements. They divided the territory into monolithic blocks: some of them rose in the form of revived high ridges, others sank, forming intermountain depressions. The latest uplifts are occurring in the Caucasus, with the amplitude of movements reaching several centimeters per year.

Exogenous processes that shape modern relief are associated primarily with the activity of flowing waters, primarily rivers and glaciers, as well as with the characteristics climatic conditions. This is, for example, the relief created by permafrost processes.

Ancient glaciation in Russia. During the Quaternary period, due to changes in climatic conditions, several glaciations occurred in many regions of the Earth. The largest of them was the so-called Dnieper. The centers of glaciation in Eurasia were the mountains of Scandinavia, the Polar Urals, the Putorana Plateau in the north of the Central Siberian Plateau and the Byrranga Mountains on the Taimyr Peninsula. From here the ice spread to other territories.

Rice. 23. Ancient glaciation

Using Figure 23, determine the southern limit of the distribution of glaciation. Which areas of our country experienced the greatest influence of the glacier?

As the glacier moved south, the Earth's surface changed greatly. Stones (boulders) and loose sediments (sand, clay, crushed stone) moved from the center of glaciation along with the ice. On its way, the glacier smoothed the rocks, leaving deep scratches on them. In the warmer climates of the south, the glacier melted, depositing the material it brought with it. Loose clay-boulder glacial deposits are called moraine. Moraine hilly-ridge relief prevails on the Valdai and Smolensk-Moscow uplands of the Russian Plain.

Which landforms predominate in the center of the glaciation, and which in more southern areas where the ice melted?

When the glacier melted, huge masses of water formed, which transported and deposited sandy material, leveling the surface. This is how water-glacial plains were created along the outskirts of the glacier. In the northern regions, melted glacial waters filled depressions deepened by the glacier in solid crystalline rocks. This is how numerous lakes were formed in the north-west of the Russian Plain.

Activity of flowing waters. The land surface is constantly exposed to flowing waters - rivers, groundwater, temporary watercourses associated with precipitation. The activity of flowing waters is especially enhanced in areas with significant slopes and large amounts of precipitation. Therefore, in many mountainous areas, water-erosive terrain predominates.

Flowing waters not only dissect the surface, creating gorges, ravines, hollows, but also deposit destruction products in river valleys, in foothill areas and on gentle mountain slopes.

Rice. 24. Glacial landforms

Wind activity. Where it doesn't fall a large number of precipitation, the wind plays a leading role in changing the relief. Wind activity in the European part of Russia is especially evident in the regions of the Caspian lowland.

Where sands are common, the wind creates an aeolian relief with dunes, as, for example, on the Curonian Spit on the coast Baltic Sea near the city of Kaliningrad.

Human activity. Academician V.I. Vernadsky noted that human activity in mining turned it into a serious relief-forming factor.

Rice. 25. Anthropogenic impacts on the relief

Yes, when open method During mining, huge quarries and pits are created, and the whole area takes on an eerie, fantastic look. People build canals, dams, and railway tunnels, moving huge masses of soil. All this leads to the acceleration of relief-forming processes. Moreover, they are often accompanied by adverse consequences for humans: landslides and collapses form, large areas of fertile land are flooded, etc.

Natural natural phenomena , occurring in the lithosphere and bringing great disasters to people, are earthquakes and volcanic eruptions, as well as landslides, landslides, avalanches and mud-stone flows.

In 1995, as a result of a strong earthquake (about 8 on the Richter scale) in the north of Sakhalin Island, the oil workers’ village of Neftegorsk was literally wiped off the face of the earth in a matter of minutes. Thousands of residents were affected. The destruction was so great that a government commission decided that it was impossible to rebuild the city on this site.

Rice. 26. Belts of earthquakes and volcanism

Using Figure 26, identify the seismically active areas of our country. Remember how powerful earthquakes cause great destruction and are dangerous to human life.

Landslides, landslides, landslides, and avalanches bring big troubles to people. All of them occur most often in mountainous areas, when, under the influence of gravity, rock fragments or masses of snow move along mountain slopes.

Rice. 27. Landslide structure

Sat down- stormy mud-stone flows. Most often, they occur near the end of the glacier after heavy rains or rapid snowmelt, when moisture-saturated soil begins to descend down the valley at an ever-increasing speed, taking with it a mass of stones.

Landslides- This is the displacement of rock masses down a slope under the influence of gravity. They are formed when water-resistant rocks lie shallow or when aquifer-bearing and aquifer-resistant layers alternate. The waterlogged upper layers slide along the aquitard, carrying with them everything that is on the surface. Landslide processes intensify during earthquakes and heavy rainfall.

Questions and tasks

What processes occurring in our time indicate the continuous development of the relief?
When was the ancient glaciation? Show the southern border of the largest glaciation.
What influence did the glacier have on the modern topography?
In which areas of our country is the relief particularly affected by the activity of flowing waters, and in which – by the activity of wind?
What natural phenomena are associated with the lithosphere?
On a contour map, show the areas of our country where earthquakes, volcanic eruptions, mudflows, and landslides can occur.

Final assignments on the topic

What sources of geographic information should be used to characterize the relief of a particular territory?
Explain the patterns of location of the main landforms on the territory of Russia. What cards did you use and why?
Prove that the process of relief formation continues in our time.
Practical work No. 3. Explanation of the dependence of the location of large landforms and mineral deposits on the structure of the earth's crust.
Compose comparative characteristics relief, geological structure and mineral resources of the Russian and West Siberian plains, using the following plan: where the territory is located; what tectonic structure is it confined to; what age rocks make up the territory; average, minimum and maximum heights of the territory; reasons for their placement; what external processes participated and are participating in the formation of the relief; what landforms are created by this or that process; their placement; what mineral resources are there in this area; how to explain their presence here; what natural phenomena are associated with the relief features, as well as with tectonic and geological structure; possible measures to combat them.
Make a description of any of the Russian mountain ranges located in the south of Siberia, using the above plan.
Describe the relief of your region (region, republic).

Until now, we have considered internal relief-forming factors, such as movements of the earth's crust, folding, etc. These processes are caused by the action of the internal energy of the Earth. As a result, large landforms such as mountains and plains are created. During 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 to destroy 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 with water, others (limestone, gypsum) dissolve very intensively. If water penetrates along cracks into layers of soluble rocks, then these cracks widen. In those places where water-soluble rocks are close to the surface, numerous dips, funnels and basins are observed on it. This karst landforms(see Fig. 4).

Rice. 4. Karst landforms

Karst is the process of dissolving rocks.

Karst landforms are developed in the East European Plain, the 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 processes of destruction, the products of destruction are transferred to low areas, thus the relief is smoothed out.

Let's consider how the Quaternary glaciation shaped the modern topography of our country. Glaciers have survived today 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 landform. This type of relief is common in Russia and where there are no modern glaciers - in the northern parts of the East European and West Siberian Plains. This is the result of ancient glaciation that arose in the Quaternary era due to climate cooling (see Fig. 6).

Rice. 6. Territory of ancient glaciers

The largest centers of glaciation at that time were the Scandinavian mountains, the Polar Urals, and 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 approaching the territory of our plains in several waves. Scientists believe that there were approximately 3-4 glaciations, which were followed by interglacial eras. Last glacial period ended about 10 thousand years ago. The most significant glaciation was on the East European Plain, where the southern edge of the glacier reached 48º-50º N. w.

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

In the centers of glaciation, from where ancient glaciers moved, traces of activity in the form of special relief forms - Ram's foreheads - are widespread. These are rock protrusions with scratches and scars on the surface (slopes facing the movement of the glacier are gentle, and those opposite 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 their route, they smoothed out the terrain. A characteristic glacial relief is observed in Russia on the territory of the Kola Peninsula, the Timan Ridge, and 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 ice formed moraine(deposits of rock fragments formed by glaciers as they move and melt). These rocks were deposited in more southern areas where the glacier melted. 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 relief they are represented by curved rows tens or sometimes even hundreds of kilometers long, for example the Northern Uvaly on the East European Plain (see Fig. 8).

When glaciers melted, flows of meltwater 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 “zandra” - sand). Examples of outwash plains are the Meshchera lowland, the Upper Volga, and the Vyatka-Kama lowlands. (see Fig. 9).

Rice. 9. Formation of outwash plains

Among the flat-low hills, water-glacial landforms are widespread, oz(from Swedish “oz” - ridge). These are 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 the settling on the surface of loose sediment formed by rivers flowing along the surface of glaciers (see Fig. 10).

Rice. 10. Formation of eskers

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

Rice. 11. Ravine

Overgrown, the ravine turns into a ravine. The slopes of the hills (Central Russian, Volga, etc.) have the most developed ravine-gully 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 sediments

They consist of river floodplains, stretching in strips along river beds (see Fig. 13).

Rice. 13. Structure of the river valley

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

Rice. 14. Width of the Volga in various sections

Traditional places of human settlement are located along the river valleys and special kind economic activity- livestock farming on floodplain meadows.

In lowlands experiencing slow tectonic subsidence, extensive river floods and wandering of their channels occur. As a result, plains are formed, built by river sediments. This type of 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 streams into the depths and prevails in mountain rivers and rivers of plateaus, which is why deep river valleys with steep slopes are formed here. Lateral erosion is aimed at eroding 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 seas advance on flooded land, sedimentary rocks accumulate in horizontal layers. The surface of the plains, from which the sea retreated long ago, has been greatly altered by flowing waters, wind, and glaciers. (see Fig. 16).

Rice. 16. Sea retreat

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

Wind activity also creates certain forms of relief, which are called aeolian. Aeolian landforms form in open spaces. In such conditions, the wind carries large amounts of sand and dust. Often a small bush is a sufficient barrier, the wind speed decreases and the sand falls to the ground. This is how small and then large sand hills are formed - barchans and dunes. In plan, the dune has the shape of a crescent, with its convex side facing the wind. As the wind direction changes, the orientation of the dune also changes. Landforms associated with wind are distributed mainly in the Caspian lowland (dunes), on the Baltic coast (dunes) (see Fig. 17).

Rice. 17. Formation of a dune

The wind blows a lot of small debris and sand from the bare mountain peaks. Many of the grains of sand it carries out hit the rocks again and contribute to their destruction. You can observe bizarre weathering figures - remnants(see Fig. 18).

Rice. 18. Remnants - bizarre landforms

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

Rice. 19. Forest

Forest covers large areas in the southern parts of the 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. Territories of Russia covered with forest (shown in yellow)

It is believed that the formation of forests is associated with the blowing of dust and strong winds. The most fertile soils form on the forest, but it is easily washed away by water and the deepest ravines appear in it.

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

Bibliography

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

The influence of internal and external processes on the formation of relief ().
External forces that change the terrain. Weathering. ().
Weathering().
Glaciation on the territory of Russia ().
Physics of dunes, or how sand waves are formed ().

Homework

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

Over time, it changes under the influence of various forces. Places where there were once great mountains become plains, and in some areas volcanoes arise. Scientists are trying to explain why this happens. And already a lot modern science known.

Reasons for transformation

The relief of the Earth is one of the most interesting mysteries of nature and even history. Because of the way the surface of our planet changed, the life of mankind also changed. Changes occur under the influence of internal and external forces.

Among all landforms, large and small ones stand out. The largest of them are continents. It is believed that hundreds of centuries ago, when there was no man yet, our planet had a completely different appearance. Perhaps there was only one continent, which over time was split into several parts. Then they separated again. And all those continents that exist now appeared.

Another major form was the oceanic trenches. It is believed that there were also fewer oceans before, but then there were more. Some scientists argue that hundreds of years later new ones will appear. Others say that the water will flood some areas of the land.

The relief of the planet has been changing over many centuries. Even though people sometimes greatly harm nature, their activities are not capable of significantly changing the relief. This requires such powerful forces that only nature has. However, man cannot not only radically transform the planet’s topography, but also stop the changes that nature itself produces. Despite the fact that science has made great strides forward, it is not yet possible to protect all people from earthquakes, volcanic eruptions and much more.

Basic information

The Earth's topography and major landforms attract close attention many scientists. The main varieties include mountains, highlands, shelves and plains.

The shelf is those areas earth's surface, which are hidden under the water column. Very often they stretch along the banks. A shelf is a type of landform that is found only underwater.

Highlands are isolated valleys and even systems of ridges. Much of what is called mountains is actually highlands. For example, the Pamir is not a mountain, as many people believe. Also, the Tien Shan is a highland.

Mountains are the most ambitious landforms on the planet. They rise above the land by more than 600 meters. Their peaks are hidden behind the clouds. It happens that in warm countries you can see mountains whose peaks are covered with snow. The slopes are usually very steep, but some daredevils dare to climb them. Mountains can form chains.

The plains are stability. Residents of the plains are least likely to experience changes in terrain. They hardly know what earthquakes are, which is why such places are considered the most favorable for life. A true plain is the flattest possible surface of the earth.

Internal and external forces

The influence of internal and external forces on the Earth's topography is enormous. If you study how the surface of the planet has changed over several centuries, you will notice how what seemed eternal disappears. It is being replaced by something new. External forces are not capable of changing the Earth's topography as much as internal ones. Both the first and second are divided into several types.

Inner forces

The internal forces that change the Earth's topography cannot be stopped. But in modern world scientists from different countries they are trying to predict when and in what place there will be an earthquake, where a volcanic eruption will occur.

TO internal forces include earthquakes, movements and volcanism.

As a result, all these processes lead to the appearance of new mountains and mountain ranges on land and on the ocean floor. In addition, geysers, hot springs, chains of volcanoes, ledges, cracks, depressions, landslides, volcanic cones and much more appear.

External forces

External forces are not capable of producing noticeable transformations. However, you should not lose sight of them. Those that shape the Earth's relief include the following: the work of wind and flowing water, weathering, melting glaciers and, of course, the work of people. Although man, as mentioned above, is not yet capable of greatly changing the appearance of the planet.

The work of external forces leads to the creation of hills and ravines, basins, dunes and dunes, river valleys, rubble, sand and much more. Water can very slowly destroy even great mountain. And those stones that are now easily found on the shore may turn out to be part of a mountain that was once great.

Planet Earth is grandiose creation, in which everything is thought out to the smallest detail. It has changed over the centuries. Cardinal transformations of the relief took place, and all this was under the influence of internal and external forces. In order to better understand the processes occurring on the planet, it is imperative to know about the life it leads, not paying attention to humans.

Lesson 9. DEVELOPMENT OF RELIEF FORMS

19.08.2014 9786 0

Objectives: to form an idea of the interaction of internal and external processes as a source of relief development; introduce the peculiarities of relief formation on the territory of Russia as a whole and Volgograd region in particular; show the impact of society on changes in the Earth's surface.

During the classes

I. Testing knowledge and skills on the topic “Russian Mineral Resources”.

Possible verification options:

1. Individual written Verification work. Students receive cards with parts glued on them. contour maps individual regions and given tasks for them. It is possible to propose the contours of Western Siberia, the Central Siberian Plateau, the Eastern European plain, Ural mountains. The tasks are to name the tectonic structure, its age, landform, height, mineral deposits, and explain their origin.

2. Individual survey:

1) Tell us about minerals and their connection with the tectonic structure of the territory.

2) Tell us about the minerals associated with platforms and folded areas.

3) Assess the mineral resource base of Russia.

4) Tell us about the rational use of mineral resources and the protection of subsoil.

5) Describe the environmental problems associated with mining.

3. Frontal conversation is carried out on the main questions of the previous lesson:

1) What are minerals?

2) What is a deposit?

3) What is a swimming pool?

4) What determines the location of certain mineral deposits?

5) What mineral resources is Russia rich in?

6) Not far from the Arctic Circle, in Vorkuta and Ukhta, we mine coal and gas. What does their presence in this area indicate? How has the nature of this area changed since the formation of oil and coal?

7) What research methods are used by geologists currently?

8) Name the largest coal and oil and gas deposits in Russia.

9) Where is iron ore mined on the territory of the East European Plain? What tectonic structure are these deposits associated with?

10) What measures should be taken to save minerals?

11) Can dirt be a mineral? Why?

12) What mineral does the teacher use when explaining new material? How was this mineral formed?

13) What is the classification of minerals?

4. Checking the nomenclature of mineral basins.

Students must fill in the blanks in the table:

Studying new topic involves the development and concretization of knowledge about the action of internal and external relief-forming processes. Therefore, during the introductory conversation, it is necessary to update the information received by schoolchildren in the process of studying geography courses in grades 6 and 7. The teacher organizes a conversation, as a result of which he finds out what students know about changes in relief. Based on the students' knowledge, the teacher builds his subsequent lecture.

This stage of the lesson is conducted in the form of a lecture. The teacher accompanies his story with a demonstration of paintings and illustrations of various relief forms. To better assimilate the material, it is necessary to consolidate it during the lecture. Questions and tasks are given in section IV. The result of the lecture is that students compile a table in their notebooks, which indicates the relief-forming factors and the relief forms they create. The teacher needs to ensure that students understand keywords, it is also advisable to write them down in a notebook during the lecture.

1. The relief of the earth’s surface is formed under the influence of processes that can be divided into two groups:

I. Internal or endogenous(from the Greek endon - inside and genes - giving birth, born). Their source is the thermal, chemical, radioactive energy of the Earth's interior. Endogenous processes manifest themselves in the form of mountain-building movements, the introduction of magma into the earth's crust, its outpouring onto the surface, slow vibrations of the earth's crust, etc. Landforms that are created primarily by endogenous processes are called endogenous.

II. External or exogenous(from the Greek exo - outside, outside). They occur almost exclusively due to solar energy entering the Earth. Landforms created as a result of these processes are called exogenous. Anthropogenic factors are often classified as external processes, but they can also be classified as a separate group.

Landforms are created through the interaction of endogenous and exogenous processes, but in most cases it is possible to identify a leading process belonging to one or another group. The larger the landform, the greater the role endogenous processes in its formation. Exogenous processes create details, small forms, to which the mountains and plains owe their uniqueness and diversity. Endogenous and exogenous processes operate continuously and simultaneously; at some time some may be more pronounced, at another period - others, but the action of both groups of processes does not stop.

2. Endogenous landforms are created as a result of movements of the earth's crust. We are accustomed to thinking that we ourselves are moving along the stationary surface of the Earth. But for the Earth to move - no, not like a planet around the Sun, but like the soil under our feet... Well, perhaps in some places and occasionally - during earthquakes, landslides or explosions. But now we will not talk about this. That same unshakable Earth, or rather the earth’s crust, fluctuates and moves everywhere and always. Only we rarely notice it or don’t notice it at all. Literally every point of the earth's crust moves: it rises up or falls down, moves forward, backward, right or left relative to other points. Their joint movements lead to the fact that somewhere the earth's crust slowly rises, somewhere it falls. These slow movements went unnoticed until the end of the 18th century. The famous Swedish physicist and astronomer Anders Celsius laid the foundation for the study of modern movements of the earth's crust (we still use the 100-degree temperature scale he proposed). He made notches on the coastal rocks of the Scandinavian Peninsula to study the mutual movements of land and sea. It soon became clear that the serifs were getting higher and higher above mean sea level. The scientist believed that it was due to lowering sea levels. But later it turned out that the reason was the rise of the land. 250 years have passed since the Celsius experiment, during which time scientists have solved many questions. For example, it was found that Northern Europe (Scandinavian, Kola Peninsulas, Finland, Karelia) is rising from the surrounding seas at a rate of up to 1 cm per year. But the territory of Denmark and the Netherlands, on the contrary, is falling. Already, approximately 1/3 of the territory of the Netherlands is below sea level. The Lower Volga region is also experiencing uplift, because previously these areas were occupied by the sea. Mountain systems also experience uplifts. Despite the fact that rocks have great strength and hardness, they can be folded and torn by tectonic faults, as well as broken by cracks. For example, Lake Baikal is located in a graben. A graben is a parallel system of faults that bound a basin. The greatest depth of the lake reaches 1620 m. Slow movements of the earth's crust often proceed unnoticed: stresses slowly increase, layers of rocks slowly deform, crushing into folds, slowly shifting along fractures, and only sometimes this movement, like an explosion, occurs in seconds. Then the earth “shakes.” A strong earthquake can produce significant changes to the earth's surface. Along the faults of the earth's crust, its blocks shift, and where there was previously a flat place, a cliff appears. Landslides and landslides occur in the mountains.

3. Landforms created by exogenous processes.

In elevated areas of the earth's surface, rock destruction occurs. Then the direct action of gravity, water, wind, and ice transport crushed, destroyed rocks to lower areas of the surface, where they are deposited. The removal of rock particles from elevated areas is called denudation (from the Latin denudation - exposure). Rock deposition is accumulation (from the Latin accumulatio - gathering in a heap, accumulation). The rate of denudation depends on what rocks are destroyed and removed. Sedimentary rocks usually break down more easily, while igneous and metamorphic rocks are more resistant. Denudation reduces the high areas of the earth's surface, accumulation increases the low ones, thus the overall height difference decreases.

Exogenous processes begin with the preparation of rocks for transport, with their destruction. All processes of destruction are called weathering. It occurs under the influence of sunlight, water, air, and organisms.

1) Slope processes. The essence of these processes is that under the influence of gravity - with or without the help of water - the rocks that make up the slope are carried from its upper part to the foot, where they are deposited. At the same time, the slope gradually becomes flatter. The steeper the slope, the more pronounced slope processes are. Slope processes accompany any type of exogenous processes and many types of endogenous ones and are so closely related to them that they seem to be part of these processes. The falling or rolling of small debris (sand, gravel) is called shedding. If large debris falls or rolls down, it is a rockfall; when it goes down the slope large mass rock that is crushed and mixed during movement is a landslide. In case of large collapses they can be moved huge quantities breeds Thus, in 1911, in the Pamirs, as a result of an earthquake, the famous Usoi landslide occurred, which created a dam in the river valley, above which Lake Sarez was formed. The weight of the collapse was 7 billion tons.

2) Landforms created by flowing water.mi. flowing water

The most active factor in the transport of rock particles. The erosion of rocks by flowing water is called erosion (from the Latin erosio

Corrosion), and the landforms formed by this process are erosive. These will include gullies, ravines, and river valleys. A ravine is a steeply sloped pothole on a hill, formed by melt and rainwater, i.e., a temporary watercourse. The length of a ravine can reach several kilometers, depth - several tens of meters, width - tens, sometimes hundreds of meters. The ravines are gradually growing, their upper reaches moving further and further. They do a lot of damage agriculture, dismembering and destroying fields. The areas are dissected by ravines to such an extent that the slopes of neighboring ravines intersect and become unsuitable for any use. They are called bad lands, badlands. The fight against ravines is carried out by securing their slopes with forest plantings. An old, no longer growing ravine turns into a ravine; The gully is wider than the ravine, its slopes are gentler, they are overgrown with grass, sometimes bushes or forest. Permanent watercourses - streams and rivers - flow in valleys developed by flowing water together with slope processes. The relief differs sharply in the valleys of mountain and lowland rivers. Mountain river valleys are narrow, steep, and deeply incised. The valleys of lowland rivers are wide (up to tens of kilometers), their depth is small, and the slopes are gentle. Landforms created by flowing waters are widespread in some territories, for example the Volgograd region.

3) Landforms, created by groundwater. The speed of movement of groundwater is low, so they affect the relief for the most part not mechanically, but by dissolving racerock. Limestones dissolve rock salt, gypsum and some other rocks. By dissolving the rock, water forms cavities, caves, sinkholes, etc. This process is called karst, and the landforms are called karst. Caves are complex systems of passages and halls, the length can reach several kilometers. In Russia, the Kungur Cave in the Urals is widely known. A common form of karst relief is funnels - closed conical, bowl-shaped depressions with a diameter of several meters. They are found in the south of the Volgograd region in the Trans-Volga region.

4) Landforms created by glaciers. A lot of the work of moving rock fragments is done by glaciers - natural accumulations of ice in places where low temperatures prevail. Glaciers move under the force of gravity, since ice is plastic and can flow slowly. The rock fragments carried by a glacier and ultimately deposited by it are called moraine. Mountain glaciers are located in near-summit cup-shaped niches - cirques. When a glacier moves down a mountain valley, it expands and deepens it, forming a trough-shaped valley - a trough. In lower places, where it is warmer, the glacier melts, but the moraine it brought remains. Glaciation covers not only mountainous areas, but also vast areas on the plains. Several glaciations occurred during the Quaternary period. Their centers in Russia were located on the Kola Peninsula, the Polar Urals, the Putorana Plateau, and the Byrranga Mountains. As the climate became warmer, the glaciers became shorter and gradually disappeared completely. In areas where glaciers deposited material, large areas remained occupied by hilly moraine terrain. This type of relief prevails on the Valdai and Smolensk-Moscow uplands of the Russian Plain. The last glaciation reached the Volgograd region.

5) Landforms in areas with a dry climate. The relief of areas with insufficient moisture - deserts and semi-deserts - is usually primarily associated with the action of wind. Landforms formed as a result of the action of wind are called aeolian, named after the ancient Greek god of the wind, Aeolus. The simplest aeolian forms are blowing basins. These are depressions formed in places where small particles are carried away by the wind from a surface not protected by vegetation. The bottom of the basin is strewn with pebbles, rubble and boulders. Dunes are common in deserts. This is an accumulation of loose sand, blown by the wind, ranging from a meter to 100-150 m in height. The dune in plan has the shape of a crescent, with its convex side facing the wind.

6) Coastal relief forms. Unique relief forms are created on the shores of seas and large lakes. Almost all of them are associated with the geological structure of the coast, with the activity of sea or lake waves. On fairly steep banks, a cliff is most often formed - a vertical or almost vertical ledge. Beaches are formed along gently sloping coasts - accumulations of marine sediments.

7) Landforms in areas of permafrost distribution. Permafrost affects the relief, since water and ice have different densities, as a result of which freezing and thawing rocks undergo deformation. The most common type of deformation of frozen soils is heaving, associated with an increase in the volume of water during freezing. The resulting relief forms are called heaving mounds; their height is usually no more than 2 m. During layer-by-layer freezing, ground and river ice dams are formed. Giant aufeis with an area of up to 20 km2 are known. The thickness of the ice dams ranges from several to 500 m.

8) Landforms created by living organisms. On land, such forms are usually small. These are swamp hummocks, marmots, and in tropical countries - termite mounds. Surchins and gophers can often be found in the steppes of the Volga region. In the temperate zone, large areas are occupied by swamps with peat ridges; The height of the ridges is small - usually 0.5 m, sometimes somewhat more; the ridges can extend for hundreds of meters and kilometers. The role of living organisms on the shores of the seas is incomparably greater. Reef-building organisms actively manifest themselves in the tropical zone, the result of which are coral reefs.

9) Landforms created by man. A person can transform the relief of the earth's surface directly (by making an embankment, digging a pit) or by influencing the natural processes of relief formation - accelerating or slowing them down. Landforms created by man are called anthropogenic (from the Greek antropos - man and genes - giving birth, born). The direct impact of humans on the relief is most pronounced in areas of mining. Underground mining is accompanied by the removal of a large amount of waste rock to the surface and the formation of dumps that have a conical shape - waste heaps. Numerous waste heaps create the characteristic landscape of coal mining areas. Open-pit mining creates quarries - vast depressions formed by excavation. Significant changes in relief are made during transport, industrial and civil construction. Sites are leveled for structures, embankments and excavations are created for roads. The indirect influence of man on the relief first began to be felt in agricultural areas. Felling forests and plowing of slopes create conditions for rapid growth of ravines. Construction of buildings and engineering structures contributes to the occurrence or intensification of landslides.

Relief-forming factor	Created landforms
I. Endogenous: 1.Mountain-building movements. 2.Intrusion of magma into the earth's crust. 3.The outpouring of magma to the surface. 4.Folding. 5.Tears and deformations	1. Large landforms
II. Exogenous: 1. Direct action of gravity	1. Scree. 2.Collapse. 3.Landslide
2. Activity of flowing waters	1.Ravines. 2. Beams. 3. Bad lands. 4. River valleys
3. Glacier activity	1. Punishments. 2.Trogs. 3.Hilly-moraine terrain
4. Groundwater activity	1. Caves. 2.Funnels
5. Activity of sea and lake waves	1.Cliff (coast cliff). 2.Beach
6. Wind activity	1.Blowing basins. 2.Dunes, sand dunes. 3. Aeolian cities
7. Impact of permafrost	1. Heaving lumps. 2.Thermokarst depressions
8. Activities of living organisms	1. Swamp hummocks. 2. Surchins. 3. Peat ridges. 4.Termite mounds. 5.Coral reefs
9. Human activity	1.Careers. 2. Dumps. 3. Waste heaps. 4. Embankments. 5.Notches. 6. Excavation pits. 7.Terraced slopes

IV. Fixing the material.

To increase the effectiveness of students' learning activities in the lesson, questions and assignments to reinforce the material must be used during the lecture.

1. Based on Figure 17, determine in which regions of Russia the uplifts of the earth’s crust in the Neogene-Quaternary were the most intense. What tectonic structures are these areas associated with? By physical map determine what kind of relief was formed in these areas and what its heights are. Why are the Ural Mountains lower than Altai?

2. In what regions of Russia are slow subsidences occurring? How will this affect the appearance of the earth's surface?

3. Using the map “Earthquake Distribution Areas”, trace in which areas the most powerful earthquakes are observed. What is this connected with? Within which tectonic structures are earthquakes extremely rare? Why?

4. Using the “Ancient Glaciation” map, determine the southern border of the distribution of sheet glaciation. Which areas of our country experienced the greatest influence of the glacier? Which landforms predominate in the center of the glaciation, and which in more southern areas where the ice melted?

5. Think about whether erosive terrain is most typical for mountainous or flat areas. Which rocks are most susceptible to erosion?

6. In which regions of Russia is the relief particularly affected by the activity of flowing waters, and in which - by the activity of wind?

V. Summing up.

Homework:§ 8 to p. 52, learn key words.

Other forces are also working to destroy rocks - chemical. Seeping through cracks, water gradually dissolves rocks (see Fig. 3).

Rice. 3. Dissolution of rocks

Rice. 4. Karst landforms

Karst is the process of dissolving rocks.

Karst landforms are developed in the East European Plain, the 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 processes of destruction, the products of destruction are transferred to low areas, thus the relief is smoothed out.

Let's consider how the Quaternary glaciation shaped the modern topography of our country. Glaciers have survived today only on the Arctic islands and on the highest peaks of Russia (see Fig. 5).

Rice. 5. Glaciers in the Caucasus Mountains ()

Rice. 6. Territory of ancient glaciers

The largest centers of glaciation at that time were the Scandinavian Mountains, the Polar Urals, the Novaya Zemlya Islands, and the 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 approaching the territory of our plains in several waves. Scientists believe that there were approximately 3-4 glaciations, which were followed by interglacial eras. The last ice age ended about 10 thousand years ago. The most significant glaciation was on the East European Plain, where the southern edge of the glacier reached 48º-50º N. w.

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

Rice. 7. Lamb forehead

Rice. 8. Moraine formation

Rice. 9. Formation of outwash plains

Rice. 10. Formation of eskers

Rice. 11. Ravine

Rice. 12. Accumulation of river sediments

They consist of river floodplains, stretching in strips along river beds (see Fig. 13).

Rice. 13. Structure of the river valley

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

Rice. 14. Width of the Volga in various sections

Traditional places of human settlement are located along the river valleys and a special type of economic activity is being formed - livestock raising on floodplain meadows.

Rice. 15. Western Siberia

Rice. 16. Sea retreat

Rice. 17. Formation of a dune

Rice. 18. Remnants - bizarre landforms

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

Rice. 19. Forest

Forest covers large areas in the southern parts of the 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. Territories of Russia covered with forest (shown in yellow)

It is believed that the formation of the forest is associated with the blowing of dust and strong winds. The most fertile soils form on the forest, but it is easily washed away by water and the deepest ravines appear in it.

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

Bibliography

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

The influence of internal and external processes on the formation of relief ().
External forces that change the terrain. Weathering. ().
Weathering().
Glaciation on the territory of Russia ().
Physics of dunes, or how sand waves are formed ().

Homework

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