Influence of internal and external processes on the formation of relief. External forces creating relief
Over time, it changes under the influence of various forces. Places where there were once great mountains are becoming plains, and in some areas there are volcanoes. Scientists are trying to explain why this is happening. And already a lot modern science known.
Reasons for transformations
The relief of the earth is one of the most interesting riddles nature and even history. Because of how the surface of our planet has changed, the life of mankind has also changed. Change occurs under the influence of internal and external forces.
Among all landforms, large and small ones stand out. The largest of them are the continents. It is believed that hundreds of centuries ago, when there was no man yet, our planet had a completely different look. Perhaps there was only one mainland, which eventually broke up into several parts. Then they split up again. And all the continents that exist now appeared.
Another major form was the oceanic depressions. It is believed that earlier there were also fewer oceans, but then there were more of them. Some scientists argue that after hundreds of years new ones will appear. Others say that the water will flood some parts of the land.
The relief of the planet has changed over the centuries. Even despite the fact that a person sometimes greatly harms nature, his activity is not capable of significantly changing the relief. For this we need such powerful forces that only nature has. However, a person cannot not only radically transform the relief of the planet, but also stop the changes that nature itself produces. Despite the fact that science has made a big step forward, it is not yet possible to protect all people from earthquakes, volcanic eruptions and much more.
Basic information
The relief of the Earth and the main landforms attract close attention many scientists. Among the main varieties are mountains, highlands, shelves and plains.
The shelf is those parts of the earth's surface that are hidden under the water column. Very often they stretch along the coast. The shelf is that type of relief that is found only under water.
Uplands are isolated valleys and even range systems. Much of what is called mountains is actually highlands. For example, Pamir is not a mountain, as many people think. The Tien Shan is also a highland.
Mountains are the most grandiose 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, the peaks of which 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. The inhabitants of the plains are the least likely to experience changes in relief. They almost do not know what earthquakes are, because such places are considered the most favorable for life. A real plain is the most flat earthly surface.
Internal and external forces
The influence of internal and external forces on the Earth's relief is grandiose. If you study how the surface of the planet has changed over several centuries, you can see how what seemed eternal disappears. It is being replaced by something new. External forces are not able to change the Earth's relief as much as internal ones. Both the first and the second are divided into several types.
internal forces
internal forces, which change the Earth's relief, cannot be stopped. But in modern world scientists from different countries they try to predict when and where an earthquake will occur, where a volcanic eruption will occur.
Internal forces include earthquakes, movements, and volcanism.
As a result, all these processes lead to the emergence of new mountains and mountain ranges on land and at the bottom of the ocean. In addition, there are geysers, hot springs, chains of volcanoes, ledges, cracks, depressions, landslides, volcano cones and much more.
Outside forces
External forces are not capable of producing noticeable transformations. However, they should not be overlooked. The shaping of the Earth's relief includes the following: the work of wind and flowing waters, weathering, the melting of glaciers and, of course, the work of people. Although man, as mentioned above, is not yet able to greatly change the face of the planet.
The work of external forces leads to the creation of hills and ravines, hollows, 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. There have been cardinal transformations of the relief, and all this - under the influence of internal and external forces. In order to better understand the processes taking place on the planet, it is imperative to know about the life that it leads, not paying attention to man.
So far, we have considered internal relief-forming factors, such as movements earth's crust, folding, etc. These processes are due to the action of the internal energy of the Earth. As a result, large forms terrain such as mountains and plains. In the lesson, you will learn how the relief was formed and continues to form under the influence of external geological processes.
Relief-forming processes
It would be wrong to assume that the relief of our planet was formed in those ancient geological epochs under the influence of internal (endogenous) forces. Even in such stable forms of the earth's surface as platforms, changes occur under the influence of external factors. All relief-forming processes can be divided into two large groups: internal (endogenous) and external (exogenous).
The main exogenous processes that change the relief of our country include weathering, glaciation, the activity of flowing waters and wind processes (see Fig. 1).
Rice. 1. External relief-forming factors
Weathering
Weathering- this is the process of destruction and change of rocks under the influence of mechanical and chemical effects of the atmosphere, soil and surface water and organisms.
Rocks are destroyed by temperature changes due to the fact that the minerals of which they are composed have different coefficients of thermal expansion. Over time, cracks appear in the once monolithic rock. Water penetrates into them, which freezes at negative temperatures and, turning into ice, literally “breaks” the rocks. Their destruction occurs, and along with this, the “smoothing” of the relief forms. Such processes are called physical weathering. They occur most intensively in the mountains, where solid monolithic rocks come to the surface. The rate of physical weathering processes (about 1 mm per year) seems to be very low. However, over millions of years, the mountains will already drop by 1 kilometer. Thus, for complete destruction highest mountains The land of the Himalayas would take 10 million years. By geological standards, this is a very short time period (see Fig. 2).
Rice. 2. Physical weathering
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 forms relief
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.
Glaciation
Consider how the Quaternary glaciation shaped the modern relief 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 relief . Such a 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 an ancient glaciation that arose in the Quaternary 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. Last glacial period ended about 10 thousand 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 protrusions of rocks with scratches and scars on the surface (the 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 "zandr" - sand). Examples of outwash plains are the Meshcherskaya lowland, the Upper Volga, Vyatka-Kama lowlands (see Fig. 9).
Rice. 9. Formation of outwash plains
Among the flat-low hills, water-glacial landforms are widespread, ozes(from the Swedish "oz" - ridge). These are narrow ridges, up to 30 meters high and up to several tens of kilometers long, resembling railway embankments in shape. They were formed as a result of sedimentation on the surface of loose sediments formed by rivers flowing along the surface of glaciers (see Fig. 10).
Rice. 10. Formation of lakes
Activity of flowing waters
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
River floodplains consist of them, 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 kind economic activity - 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 widespread 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, has been greatly altered by flowing waters, wind, and 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.
wind activity
The activity of the wind also creates certain landforms, which are called eolian. Eolian landforms are formed on 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) and on the Baltic coast (dunes) (see Fig. 17).
Rice. 17. Formation of a dune
The wind blows a lot of small fragments and sand 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. - this is a loose, porous, silty rock (see Fig. 19).
Rice. 19. Forest
covered with forest large territories 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. 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. The most fertile soils are formed on the forest, but it is easily washed away by water and the deepest ravines appear in it.
Summing up
The formation of the 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 hour Grade 8 / 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-methodical set) "SPHERES". Textbook “Russia: nature, population, economy. 8th grade". Atlas.
Influence of internal and external processes on the formation of relief. External forces that change the relief. Weathering. . Weathering. Glaciation in 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) the vertices Caucasus mountains and Altai acquired a pointed shape?
5. Remember what the following concepts mean:relative and absolute height, watershed, river valley, terrace, interfluve, beam, dune.
As you know, Chuvashia is located in the eastern part of the East European Plain. But the word "plain" defines only the general character of the republic's surface. In fact, the relief of Chuvashia is complex and varied. On our plain there are numerous elevated areas and depressions, river valleys, deep ravines, dune hills and marshy lowlands.
The main factor in the formation of the modern relief of Chuvashia are erosion processes resulting from the activity of water. On slopes and watersheds, it constantly washes away material and carries it to lower places. Enhances material flush geological structure territory of the republic. Rocks formed in the Permian period and coming to the surface are crumpled, contain aquifers and feed watercourses. In depressions, flowing water merges into streams, eroding the soil. Ravines are born, growing into ravines, and then into the valleys of streams and rivers. And in the conditions of the general uplift of the territory, the activity of flowing waters intensifies and significantly changes the appearance of our region. It was the activity of the rivers that basically shaped the modern relief of Chuvashia.
The Volga divides the territory of our republic into two parts, differing in size and nature of the relief: the low left bank and the elevated right bank.
On left bank The Volga, which makes up 3% of the territory of the republic, formed terraces. In the relief, they are represented by a lowland with a height of 80-100 m. Hilly sands are found on the terraces. The mounds are created by the activity of the wind and represent dunes which are now covered with forest. A small height and a weak slope of the terrain against the background of significant precipitation led to the formation of many peat swamps And lakes.
Modern relief right bank Chuvashia is represented by the northeastern part of the Volga Upland. The hill was formed as a result of tectonic movements of the earth's crust in the Paleogene period. The most high point, within Chuvashia, is located in its southern part and reaches 286 m.
In the rest of the upland, the relative height ranges from 150 to 250 m.
On the entire surface of the hill, wide interfluves, indented by ravines and gullies, alternate with deeply incised valleys. In the eastern part of Chuvashia there are 2.3 times more gullies and 1.4 times more ravines than in the western part. But the northeastern part of Chuvashia has the greatest density of ravines, since there are few forests and the land is heavily plowed. The density of the river network in the northern half of the republic is higher than in the southern. In the southwestern part of Chuvashia, the girder network is denser and exceeds the ravine network by five times.
The ravines and gullies have an asymmetrical shape: the northern and eastern slopes are elongated and gentle, while the southern and western slopes are steep. This is due to uneven heating by the sun and uneven accumulation of snow on the surface, so the material is washed off the slopes with different speed. Due to the extremely dense network of ravines and gullies characteristic of our republic, it is often called the country of ravines. Most of the lands of the right-bank part of the republic are plowed up and occupied by cultivated plants. But ravines cause great harm to our fields, and we have to constantly fight them.
On the steep slopes of river valleys and large ravines of the republic, landslides. Such slopes are characterized by stepped ledges. The trees on these slopes are tilted in different directions. Landslides can be found on the right bank of the Volga, on the steep left bank of the Sura near Alatyr, and in the valleys of other rivers of Chuvashia. They develop because the slopes are composed of layered strata, where waterproof layers alternate with permeable ones. With prolonged moisture, for example, in spring or rainy autumn, the layers become unstable and huge masses of soil slide down the slope. Landslides, like ravines, cause great harm to the economy of the republic.
They destroy buildings and structures located on the slopes, destroy arable land.
Watersheds in Chuvashia are most often very even. But in some areas, where the heights exceed 200 m, there are low hills. This remnants more ancient surface, preserved in the form of islands. They are found in Alatyrsky, Vurnarsky, Kozlovsky, Morgaushsky, Urmarsky, Poretsky and Yalchiksky districts.
In the southwestern part of the republic, especially in the Sura basin, the interfluves are represented by sandy dunes overgrown with forest. depressions between the dunes waterlogged.
Thus, we are convinced that the relief of Chuvashia is really complex, the ravine-beam character of the relief dominates. The following circumstances contribute to the development of the ravine-beam network in the republic:
1) deeply dissected relief (its relative height exceeds 200 m);
2) sedimentary rocks underlying the Quaternary cover are represented by layers that are weakly resistant to erosion (aleurites, clays, limestones, sands, etc.);
3) the runoff of permanent and temporary watercourses is uneven throughout the year (for example, the runoff of Tsivil in April is 75-80% of the annual amount);
4) low forest cover in the republic (forests cover only 31%);
5) general uplift of the territory of the republic;
6) high agricultural development of lands, especially in the northern part of the republic (agricultural lands of the republic occupy 55% of its total area).
Therefore, it is necessary to conduct a constant fight against water erosion, weakening the effect of the listed causes.
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2) Among the external processes of relief formation, the greatest influence on its modern appearance was exerted by ancient glaciations, the activity of flowing waters and in areas covered with sea waters, - activity of the sea.
Geographic latitude determines the amount of solar radiation reaching the earth's surface and air temperature.
The influence of air masses determines the circulation of the atmosphere and the annual course of the main characteristics of the climate. The climate is formed under the influence of various air masses.
Seas and oceans influence the climate of coastal zones, acting as accumulators of heat and moisture. In winter, they heat the air masses passing above them, and in summer, they cool them somewhat. The seas contribute to an increase in air humidity.
The flat relief contributes to the unhindered passage of arctic and temperate air masses. Mountains retain cold air masses from the north and warm from the south, retain moisture brought from the Atlantic.
Altitudinal climatic zonality is pronounced in the mountains.
4) Cyclone - an atmospheric vortex of huge (from hundreds to several thousand kilometers) diameter with reduced air pressure in the center.
An anticyclone is an atmospheric mass, a swirling movement of air with high pressure in the center.
Signs of an anticyclone: stable and moderate weather that lasts for several days. IN summer period the anticyclone brings hot, cloudy weather. In winter, it is characterized by frosty weather and fogs.
A cyclone is not just the opposite of an anticyclone, they have a different mechanism of occurrence.
How relief is formed
Cyclones constantly and naturally appear due to the rotation of the Earth, thanks to the Coriolis force.
An important feature of anticyclones is their formation on certain areas. In particular, anticyclones form over ice fields. And the more powerful the ice cover, the more pronounced the anticyclone; that is why the anticyclone over Antarctica is very powerful, and over Greenland it is low-power, over the Arctic it is medium in severity. Powerful anticyclones also develop in the tropical zone.
PROCESSES AFFECTING THE FORMATION OF THE EARTH'S CRUST
Forces constantly act on the earth's surface, changing the earth's crust, contributing to the formation of relief. All these processes are different, but they can be combined into two groups: external (or exogenous) and internal (or endogenous). Exogenous processes operate on the surface of the Earth, while endogenous processes are deep processes, the sources of which are located in the bowels of the planet. From the outside, the forces of attraction of the Moon and the Sun act on the Earth.
Processes affecting the formation of the earth's crust
The power of attraction of others celestial bodies very small, but some scientists believe that in the geological history of the Earth, gravitational influences from space may increase. Many scientists also refer to external, or exogenous, forces as gravitation, which causes landslides, landslides in the mountains, and glaciers move from the mountains.
Exogenous forces destroy, transform the earth's crust, transfer loose and soluble products of destruction carried out by water, wind, and glaciers. Simultaneously with destruction, there is also a process of accumulation, or accumulation of destruction products. The destructive effects of exogenous processes are often undesirable and even dangerous for humans. Such dangerous phenomena include, for example, mudflows and stone flows. They can demolish bridges, dams, destroy crops. Landslides are also dangerous, which also lead to the destruction of various buildings, thereby causing damage to the economy, taking the lives of people. Among the exogenous processes, it is necessary to note the weathering, which leads to the leveling of the relief, as well as the role of the wind.
Endogenous processes raise individual sections of the earth's crust. They contribute to the formation of large landforms - megaforms and macroforms. Main source the energy of endogenous processes is the internal heat in the bowels of the Earth. These processes cause the movement of magma, volcanic activity, earthquakes, slow vibrations of the earth's crust. Internal forces work in the bowels of the planet and are completely hidden from our eyes.
Thus, the development of the earth's crust, the formation of relief are the result of the combined action of internal (endogenous) and external (exogenous) forces and processes. They act as two opposite sides of a single process. Thanks to endogenous, mainly creative processes, large landforms are formed - plains, mountain systems. Exogenous processes mainly destroy and level the earth's surface, but at the same time form smaller (microforms) relief forms - ravines, river valleys, and also accumulate destruction products.
Home > LessonLesson topic : External processes that form the relief and
associated natural phenomena
Lesson objectives : to form knowledge about the change in landforms as a result of erosion,
weathering and other external relief-forming processes, their role
in shaping the appearance of the surface of our country. Let the students down
to the conclusion about the constant change, the development of the relief under the influence of
only internal and external processes, but also human activities.
1. Repetition of the studied material.
1. As a result of what is the surface of the Earth changing?
2. What processes are called endogenous?
2. What parts of the country experienced the most intense uplifts in the Neogene-Quaternary?
3. Do they coincide with earthquake distribution areas?
4. Name the main active volcanoes in the country.
5. In what parts Krasnodar Territory appear more often internal processes?
2. Learning new material.
Any activity external factor consists of the process of destruction and demolition of rocks (denudation) and the deposition of materials in depressions (accumulation). This is preceded by weathering. There are two main types of exposure: physical and chemical, as a result of which loose deposits are formed that are convenient for moving by water, ice, wind, etc.
As the teacher explains the new material, the table is filled
| External processes | main types | Distribution areas |
| The activity of the ancient glacier | Trogs, sheep's foreheads, curly rocks. Moraine hills and ridges. Introductory glacial plains | Karelia, Kola Peninsula Valdai rise, Smolensk-Moscow rise Meshcherskaya low. |
| Activity of flowing waters | Erosion forms: ravines, beams, river valleys sat down | Central Russian, Volga and others almost everywhere Eastern Transcaucasia, Baikal region, Wed. Asia |
| wind work | Eolian forms: dunes, dunes | deserts and semi-deserts of the Caspian lowlands. South coast Baltic Sea |
| The groundwater | Karst (caves, mines, funnels, etc.) | Caucasus, Central Russian erection, etc. |
| Tidal bore | abrasive | coasts of seas and lakes |
| Processes caused by the activity of gravity | landslides and scree landslides | They predominate in the mountains, often on the steep slopes of river valleys and ravines. Middle course of the Volga river, Black Sea coast |
| human activity | land plowing, f.i. mining, construction, deforestation | in places of human habitation and extraction of natural resources. |
Examples certain types external processes - pp. 44-45 Ermoshkina "Geography Lessons"
3. FIXING THE NEW MATERIAL
1. Name the main types of exogenous processes.
