§ 10. External processes that form the relief and related natural phenomena

Lesson objectives:-identify cause-and-effect relationships of diversity

relief of Russia;

Explain new concepts (mudflows, glaciation, landslides,

landslides and avalanches);

Develop interest in the subject being studied;

Equipment: physical map of Russia, I.K. - “Structure earth's crust", "Tectonic map of Russia"
Progress of the lesson.

1.Organizing moment.

2. Survey of the covered topic.

1) What relates to the internal processes that change the appearance of the Earth's crust in Russia?

2) On the territory of Russia, where earthquakes and volcanic eruptions can occur? Why?

3) Where in our country are the most ancient breeds found?

3.Study new topic.

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 by sea waters, the activity of the sea (see Fig. 17).

Ancient glaciations. General rise of land. a change in the contours of the Eurasian continent and a cooling of the climate on the globe led to the emergence of cover glaciation in the Quaternary.

There were 3-4 glaciation epochs in total.

The centers of glaciation were the mountains of Scandinavia,

Polar Ural,

Putorana

Mountains of Taimyr.

Hence le; spread to surrounding areas.

As it moved, the glacier greatly changed the surface of the Earth. From the center of the glaciation, he carried away with him stones frozen into the lower layers of ice, like a powerful bulldozer, he removed loose sediment (sand, clay, crushed stone) and even quite large stones from the surface. The glacier smoothed and rounded the rocks, leaving deep longitudinal scratches (striations) on them.

In the more southern regions, where the ice melted, the brought material was deposited on the plains - moraine.

The moraine consists of variable sand, clay, small solid fragments rocks And large stones(boulders) and forms moraine hills on the surface. Where the edge of the glacier passed, the thickness of the moraine turned out to be especially large and terminal moraine ridges appeared. Since there were several glaciations and their boundaries did not coincide, several terminal moraine ridges arose.

When the glaciers melted, huge masses of water were formed, which washed over the moraine, transported and deposited sandy material, leveling the surface. Thus, water-glacial plains were created in low areas along the outskirts of the glacier.

The relief forms created by ancient glaciation are best expressed on the Russian Plain, where the thickness of the glacier was greatest.

The relief of the plains created

sea ​​activities

glacier activity

erosion processes

river sediments

weathering, wind action and erosion

Mountain relief,

dissected by erosion

with forms of mountain glaciation and erosional dissection

About 600 km

Rice. Relief created mainly by external processes.

The ancient glaciation of mountainous areas, mainly in the outer regions, was significant. Its traces are sharp peak-shaped peaks and valleys with steep slopes and wide bottoms (troughs), including where there is no modern mountain glaciation.

Sea activity. Along the shores of the seas of the Arctic Ocean in Russia there are narrow strips of marine sediments. They are composed of flat coastal plains that arose during the advance of the seas in post-glacial times. In the southeastern part of the Russian Plain, the vast Caspian Lowland is composed of marine sediments. In Quaternary times, the sea advanced here several times. During these periods, the Caspian Sea was connected to the Black Sea through the Kuma-Manych depression.

Activity of flowing waters. Flowing waters constantly change the surface of the land. Their relief-forming activities continue to this day. Processes of destruction of rocks and soils flowing waters(erosion processes) are especially vigorous in areas with high precipitation and significant surface slopes

Therefore, erosional relief is especially characteristic of mountains and hills. All mountainous areas are dominated by erosive terrain. A dense network of mountain gorges and deep river valleys dissects the slopes of the ridges.

On the plains, in areas that were not subject to ancient glaciation, erosional dissection of the surface continued throughout the Quaternary period. Here a branched system of river valleys, gullies and deep ravines was formed, dividing watershed surfaces ( Central Russian, Privolzhskayahills).

Flowing waters not only dissect the surface, creating erosional relief, but also deposit destruction products in river valleys and on gentle slopes. Rivers especially transport a lot of material. Flat plains created by fluvial accumulation (accumulation of river sediment) stretch in stripes along river beds. They are especially characteristic of low plains and intermountain basins. These landforms occupy large areas on the West Siberian Plain (Fig. 17).

Processes caused by gravity.IN In areas with highly dissected relief, the action of gravity plays a large role in transforming the relief. It causes rock fragments to move down slopes and accumulate on gentle and concave slopes and in the foothills. In the mountains, when the slope is very steep, large masses of large clastic material often move: stone blocks and crushed stone. arise collapses And scree. Sometimes these processes also occur on plains, on steep slopes of river valleys and ravines.

When aquicluded rocks are shallow and especially when aquifer-bearing and impermeable layers alternate, the waterlogged upper layers slide down the aquitard. arise landslides.

LET'S LANDSLAND called the displacement (sliding) of rock masses down a slope under the influence of gravity.

Landslide relief is characterized by a hilly surface, waterlogging is low between the hillocks. Landslide processes intensify during earthquakes, erosion of landslide slopes by watercourses, heavy rainfall, etc.

Landslides can destroy houses and highways, and destroy gardens and crops. Sometimes landslides resulted in human casualties.

With the accumulation of a large amount of weathering products in depressions on the slopes of mountains, and sometimes on hills, and heavy precipitation, water-stone and mud flows arise - MOUNTINGS , moving at high speed and destroying everything in its path.

4. Consolidation of the covered topic.

Based on Fig. 17, tell us about the location of the relief created by various external processes throughout the country.

Tell us about the spread of natural phenomena throughout the country, explain it.

How does a person influence changes in relief?

5.Homework. Review all topics studied. Prepare for a generalization lesson.

5. Remember what the following concepts mean:relative and absolute height, watershed, river valley, terrace, interfluve, ravine, dune.

As you know, Chuvashia is located in the eastern part of the Eastern European plain. But the word “plain” defines only the general character of the surface of the republic. 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 swampy lowlands.

The main factor in the formation of the modern relief of Chuvashia is erosion processes resulting from water activity. On slopes and watersheds, it constantly washes away material and carries it to low places. The geological structure of the territory of the republic enhances the washout of material. Rocks formed during the Permian period and exposed to the surface are crushed, contain aquifers and feed watercourses. In depressions, flowing water merges into streams, eroding the soil. Gullies appear, growing into ravines, and then into valleys of streams and rivers. And in conditions of a general rise of the territory, the activity of flowing waters intensifies and significantly changes the appearance of our region. It was the activity of rivers that mainly 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-lying left bank and the elevated right-bank.

On left bank The Volga, which makes up 3% of the territory of the republic, has formed terraces. In relief they are represented by lowlands with heights of 80-100 m. On the terraces there are lumpy sands. The mounds are created by the action of the wind and represent dunes, which today are covered with forest. The low altitude and slight slope of the terrain against the backdrop 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 during the Paleogene period. The highest point within Chuvashia is located in its southern part and reaches 286 m.

In the rest of the upland area, the relative height ranges from 150 to 250 m.

On the entire surface of the hill, wide interfluves, cut 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 lands are heavily plowed. The density of the river network in the northern half of the republic is higher than in the southern half. In the southwestern part of Chuvashia, the girder network is denser and is five times larger than the ravine network.

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 material is washed off from the slopes with at different speeds. 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 on the right bank of the republic are plowed and occupied 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 distinguished by stepped ledges. The trees on these slopes are inclined 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. When wet for a long time, for example, in spring or rainy autumn, the layers become unstable and huge masses of soil slide down the slope. Landslides, like ravines, cause enormous damage to the economy of the republic.

They destroy buildings and structures located on the slopes and destroy arable land.

Watersheds in Chuvashia are most often very flat. 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 dunes swampy.

Thus, we are convinced that the relief of Chuvashia is really complex, the gully-beam nature of the relief dominates. The following circumstances contribute to the development of the gully-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 (silts, clays, limestones, sands, etc.);

3) the flow of permanent and temporary watercourses throughout the year is uneven (for example, the flow of Tsivil in April is 75-80% of the annual amount);

4) low forest coverage of the republic (only 31% is covered with forests);

5) a general rise in the territory of the republic;

6) high agricultural development of land, 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 constant struggle With water erosion, weakening the effect of the listed reasons.

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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 by sea waters, the activity of the sea.

geographic latitude determines the amount solar radiation, arriving at the earth's surface and air temperature.
The influence of air masses is determined by atmospheric circulation and the annual course of the main climate characteristics. The climate is formed under the influence of various air masses.
Seas and oceans influence the climate of coastal zones, acting as heat and moisture accumulators. In winter, they heat the air masses passing over them, and in summer, they cool them somewhat. The seas contribute to increased air humidity.
The flat terrain facilitates the unimpeded passage of arctic and temperate air masses. The mountains trap cold air masses from the north and warm air from the south, and retain moisture brought from the Atlantic.
The mountains have a pronounced altitudinal climatic zonation.

4) A cyclone is an atmospheric vortex of huge (from hundreds to several thousand kilometers) diameter with low air pressure in the center.

An anticyclone is an atmospheric mass, a vortex 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, partly cloudy weather. IN winter period characterized by frosty weather and fog.

A cyclone is not just the opposite of an anticyclone; they have a different mechanism of occurrence.

How the relief is formed

Cyclones are constantly and naturally produced by the rotation of the Earth, thanks to the Coriolis force.

An important feature of anticyclones is their formation in certain areas. In particular, anticyclones form over ice fields. And the thicker the ice cover, the more pronounced the anticyclone; That is why the anticyclone over Antarctica is very powerful, but over Greenland it is low-power, and over the Arctic it is average 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 and 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 act on the surface of the Earth, and endogenous processes act on deep-seated processes, the sources of which are located in the bowels of the planet. The gravitational forces of the Moon and the Sun act on the Earth from the outside.

Processes influencing the formation of the earth's crust

The force of attraction of others celestial bodies very small, but some scientists believe that geological history Earth's gravitational influences from space may increase. Many scientists also consider gravity to be an external, or exogenous, force, which causes landslides, mountain falls, and glaciers to move from mountains.

Exogenous forces destroy and transform the earth's crust, transporting loose and soluble products of destruction carried out by water, wind, and glaciers. Simultaneously with destruction, the process of accumulation, or accumulation of destruction products, also occurs. Destructive actions 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, and destroy crops. Landslides are also dangerous, which also lead to the destruction of various buildings, thereby causing damage to the economy and killing people. Among the exogenous processes, it is necessary to note weathering, which leads to relief leveling, as well as the role of wind.

Endogenous processes raise individual sections of the earth's crust. They contribute to the formation of large relief forms - megaforms and macroforms. Main source energy of endogenous processes - internal heat in the bowels of the Earth. These processes cause the movement of magma, volcanic activity, earthquakes, and 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 and 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 relief forms are formed - plains, mountain systems. Exogenous processes predominantly 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.

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 in general and the Volgograd region in particular; show the impact of society on changes in the Earth's surface.

Lesson progress

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

Possible verification options:

1. Individual written test. Students receive cards with parts glued on them. contour maps individual regions and assignments were given to them. We can suggest the contours of Western Siberia, the Central Siberian Plateau, the East European Plain, and the 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 a new topic involves developing and concretizing knowledge about the action of internal and external relief-forming processes. Therefore, within introductory conversation it is necessary to update the information obtained 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 relief form, the greater the role of 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 sun rays, water, air, 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 a large mass of rock descends down a slope, which in the process of movement is crushed and mixed, this is a landslide. Large rockfalls can displace enormous quantities of rock. 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. Travel speed groundwater is small, so they affect the relief for the most part not mechanically, but by dissolving racerock. Limestones, rock salt, gypsum and some other rocks dissolve. 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 geological structure shores, 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 the rapid growth of ravines. The 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.

External processes that change the relief of the earth's surface include weathering, geological activity of flowing waters, glaciers, wind. Energy for all of these processes is provided, on the one hand, by the Sun, on the other – gravitational forces.

Weathering – a set of rock destruction processes. Rocks can be destroyed due to temperature changes due to the fact that the various minerals that make up rocks have different odds thermal expansion. Over time, cracks appear in the once monolithic rock. Water can penetrate into them and negative temperatures freezes. In this case, the expanding ice breaks the rocks, they are destroyed, and at the same time the relief forms that they form are destroyed. Such processes are called physical weathering. They occur most intensely in areas with large annual and daily temperature amplitudes.

Other forces are also working to destroy rocks – chemical. Water seeping into cracks gradually dissolves rocks. The dissolving power of water increases with the content of various gases in it. Limestones, gypsum, and rock salt are subject to the most intense chemical weathering. In those places where water-soluble rocks are close to the surface, numerous failures, shafts, funnels, and basins are observed.

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

All the water flowing from continents to oceans under the influence of gravity, does a great job of washing away and demolishing loosened rocks. The water is slowly but surely destroying its bed – the rocks through which it flows. Permanent drains – rivers – form river valleys stretching from source to mouth. The appearance of ravines is associated with temporary drains.

About a million years ago, the Ice Age began on Earth due to climate cooling. A continuous ice shell covered the northern parts of Eurasia and North America. The thickness of the glacier reached 1-2 km. The movement of such a huge mass of people could not pass without leaving a mark on the relief of the earth's surface. The glacier seemed to be plowing and scraping out the earth. The products of rock destruction froze into the glacier, were transported over vast distances, and then, when the glacier melted, were “projected” onto the earth’s surface. Fjords are common within the boundaries of glaciations – long narrow bays, lake basins with intricately indented coastlines, huge boulders, as well as low hills and ridges arising from glacier deposits – moraines. Glacial landforms are most common in Eurasia and North America.

Geological activity of wind most clearly expressed in open spaces that are completely or partially devoid of vegetation. In such conditions, the wind carries large amounts of sand and dust. Where the wind weakens, the sand falls to the ground and forms a pile. Often even a small bush can become a barrier to the wind and cause the formation of sand mounds. This is how first small and then large sand hills are formed.

The wind blows a lot of small debris and sand from the bare mountain peaks. They hit the rocks again and again and contribute to their destruction. As a result, in open spaces one can observe bizarre whims of blowing – remnants. Landforms associated with wind activity are common on all continents except Antarctica.

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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 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.

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. River valley structure

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.

1. The formation of 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.

References

1. Geography of Russia. Nature. Population. 1 part 8th grade / 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 and methodological set) “SPHERES”. Textbook “Russia: nature, population, economy. 8th grade." Atlas.

1. The influence of internal and external processes on the formation of relief ().
2. External forces that change the terrain. Weathering. ().
3. Weathering().
4. Glaciation on the territory of 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?