2 how a person changes the relief of the earth. How does the Earth's topography change over time? Basic landforms

They change quite quickly (a small ravine can appear in a few months), larger forms change slowly, over centuries. There are, however, factors (such as landslides) that can change the relief: mountains and crevasses appear, and the directions of rivers change. In the summer of 2007, one of these events did not occur: a landslide destroyed a unique geographical formation - a valley of geysers.

The relief changes under the influence of two types of factors: exogenous and endogenous. Endogenous (internal) factors: movements earth's crust, volcanic eruptions are discussed in detail in the relevant sections. Exogenous factors include: the destructive activity of wind and water, heat, flora and fauna.

Water has a serious impact on the terrain. It erodes rocks, forming ravines, washing away entire hills, and washing away rocks, which can then collapse. Rivers can become fuller and lay a new channel, or they can become shallow, and then land areas remain in place of water. All these are changes in relief. In addition, water interacts with rock substances, changing their composition and structure, which can lead to changes in relief.

The wind is especially active where there are no dense growths of plants. The wind is blowing fine particles rocks and brings them to other areas, where they are deposited, retained by water or plants.

Many rocks are destroyed by heat. Either heating up or cooling back, they constantly expand and contract again. This leads to the destruction of bonds between the molecules of the substance, and the rocks crack.

Plants and animals also influence the formation of relief, some more strongly, others less. Plant roots destroy dense rocks and at the same time strengthen looser ones. Microorganisms change the structure of the soil, which can also lead to changes in topography. Animals that build dams on rivers and streams, in particular beavers, have a huge impact on the relief.

Basic landforms

1. Plains are flat or hilly areas of land with sufficient large area. The plains differ in absolute height (above sea level):
2. Lowlands, height does not exceed 200 m.
3. Hills, height from 200 to 500 m.
4. Plateau, altitude more than 500 m.
5. A plateau is a specific landform with a flat top and steep edges, and can reach 3 km.

Plains- more stable areas earth's surface, they are less likely to lowland rivers calmer, the terrain changes much more slowly.

Mountains- areas of land rising to a height of more than 500 m, with a certain peak and steep slopes.

Mountains can form ridges and highlands. A ridge is a group of mountains, apparently elongated in a certain direction and with a slight difference in height. Famous mountain ranges.

>>How and why the relief of Russia is changing

§ 14. How and why the relief of Russia changes

The formation of relief is influenced by various processes. They can be combined into two groups: internal (endogenous) and external (exogenous).

Internal processes. Among them, the most recent (neotectonic) ones had the greatest impact on the formation of modern relief. crustal movements, volcanism and earthquakes. Thus, under the influence internal processes largest, large and medium-sized forms relief.

Neotectonic movements are the movements of the earth's crust that have occurred in it over the past 30 million years. They can be both vertical and horizontal. The formation of relief is most influenced by vertical movements, as a result of which the earth’s crust rises and falls (Fig. 20).

Rice. 20. Newest tectonic movements.

The speed and height of vertical neotectonic movements in some areas were very significant. Most of the modern mountains in Russia exist only thanks to the latest vertical uplifts, since even young, relatively recently formed mountains destroyed within a few million years. Caucasus Mountains, despite the destructive influence of external forces, were raised to a height of 4000 to 6000 m. The Ural plains by 200-600 m, Altai - by 1000-2000 m. The largest plains of Russia also experienced a slight rise - from 100 to 200 m. In those places , where the earth's crust sank, depressions of seas and lakes and many lowlands arose.

According to Fig. 20 determine what types of movements prevail on the territory of Russia.

Movements of the earth's crust are still happening. The Greater Caucasus Range continues to rise at a rate of 8-14 mm per year. The Central Russian Upland is growing somewhat slower - about 6 mm per year. And the territories of Tatarstan and the Vladimir region annually fall by 4-8 mm.

Along with the slow movements of the earth's crust, earthquakes and volcanism play a certain role in the formation of large and medium-sized relief forms.

Earthquakes often lead to significant both vertical and horizontal displacements of rock layers, the occurrence of landslides and failures.

During volcanic eruptions, specific landforms such as volcanic cones, lava sheets and lava plateaus are formed.

External Processes, forming modern relief , are associated with the activity of the seas, flowing waters, glaciers, and waters. Under their influence, large relief forms are destroyed and medium and small relief forms are formed.

When seas advance, sedimentary rocks are deposited in horizontal layers. Therefore, many coastal parts of the plains, from which the sea retreated relatively recently, have a flat topography. This is how the Caspian and northern West Siberian Lowlands were formed.

Flowing waters(rivers, streams, temporary water streams) erode the earth's surface. As a result of their destructive activities, relief forms called erosion are formed. This river valleys, beams, ravines.

Valleys large rivers have a large width. For example, the Ob valley in its lower reaches is 160 km wide. Amur is slightly inferior to it - 150 km and Lena - 120 km. River valleys are a traditional place for people to settle and conduct special types of farming ( livestock farming on floodplain meadows, gardening).

Gullies are a real problem for agriculture(Fig. 21). By dividing fields into small areas, they make them difficult to cultivate. In Russia there are more than 400 thousand large ravines with total area 500 thousand hectares.

Glacier activity. IN quaternary period Due to climate cooling in many areas of the Earth, several ancient ice sheets arose. In some areas - centers of glaciation - ice accumulated over thousands of years. In Eurasia, such centers were the tori of Scandinavia, the Polar Urals, the Putorana plateau in the north of the Central Siberian Plateau and the Byrranga mountains on the Taimyr Peninsula (Fig. 22).

Using the population map in the atlas, compare the population density in the valleys of the major rivers of Siberia and in the surrounding areas.

The ice thickness in some of them reached 3000 m. Under the influence own weight the glacier was sliding south into the surrounding areas. Where the glacier passed, the earth's surface changed greatly. In places he smoothed it out. In some places, on the contrary, there were depressions. The ice polished the rocks, leaving deep scratches on them. Accumulations of huge stones (boulders), sand, clay, and rubble moved along with the ice. This mixture of various rocks is called moraine. In the south, more warm areas the glacier was melting. The moraine he carried with him was deposited in the form of numerous hills, ridges, and flat plains.

Wind activity. The wind shapes the relief mainly in arid areas and where sands lie on the surface. Under its influence, dunes, sand hills and ridges are formed. They are common on Caspian lowland, V Kaliningrad region(Curonian Spit).

Fig.22. Boundaries of ancient glaciation

Questions and tasks

1. What processes influence the formation of the Earth’s topography at the present time? Describe them.
2. What glacial landforms are found in your area?
3. What landforms are called erosional? Give examples of erosional landforms in your area.
4. What modern relief o Formative processes are typical for your area?

Geography of Russia: Nature. Population. Farming. 8th grade : textbook for 8th grade. general education institutions / V. P. Dronov, I. I. Barinova, V. Ya. Rom, A. A. Lobzhanidze; edited by V. P. Dronova. - 10th ed., stereotype. - M.: Bustard, 2009. - 271 p. : ill., map.

Lesson content lesson notes supporting frame lesson presentation acceleration methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures, graphics, tables, diagrams, humor, anecdotes, jokes, comics, parables, sayings, crosswords, quotes Add-ons abstracts articles tricks for the curious cribs textbooks basic and additional dictionary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in a textbook, elements of innovation in the lesson, replacing outdated knowledge with new ones Only for teachers perfect lessons calendar plan for the year methodological recommendations discussion programs Integrated Lessons

Weathering itself does not lead to the formation of relief forms, but only turns hard rocks into loose ones and prepares the material for movement. The result of this movement is various shapes relief.

Effect of gravity

Under the influence of gravity, destroyed rocks move on the surface of the Earth from elevated areas to lower ones. Blocks of stone, crushed stone, and sand often rush down steep mountain slopes, causing landslides and screes.

Under the influence of gravity there are landslides and mudflows. They carry huge masses of rocks. Landslides are the sliding of rock masses down a slope. They form along the banks of reservoirs, on the slopes of hills and mountains after heavy rains or melting snow. The upper loose layer of rocks becomes heavier when saturated with water and slides down the lower, water-impervious layer. Heavy rains and rapid snow melting also cause mudflows in the mountains. They are with destructive force moving down the slope, demolishing everything in its path. Landslides and mudflows lead to accidents and loss of life.

Activity of flowing waters

The most important transformer of relief is moving water, which performs great destructive and creative work. Rivers cut wide river valleys on the plains and deep canyons and gorges in the mountains. Small water flows create gully-gully relief on the plains.

Flowing bottoms not only create depressions on the surface, but also capture rock fragments, transport them and deposit them in depressions or their own valleys. This is how flat plains are formed from river sediments along rivers

Karst

In those areas where readily soluble rocks (limestone, gypsum, chalk, rock salt), amazing natural phenomena. Rivers and streams, dissolving rocks, disappear from the surface and rush deep into the bowels of the earth. Phenomena associated with the dissolution of surface rocks are called karst. Dissolution of rocks leads to the formation karst forms relief: caves, abysses, mines, craters, sometimes filled with water. Beautiful stalactites (multi-meter calcareous “icicles”) and stalagmites (“columns” of limestone growths) form bizarre sculptures in the caves.

Wind activity

In open treeless spaces, the wind moves giant accumulations of sand or clay particles, creating aeolian landforms (Aeolus is the patron god of the wind in ancient Greek mythology). Most of the sandy ones are covered with dunes and sandy hills. Sometimes they reach a height of 100 meters. From above the dune has the shape of a sickle.

Moving with high speed, particles of sand and crushed stone process stone blocks like sandpaper. This process goes faster at the surface of the earth, where there are more grains of sand.

As a result of wind activity, dense deposits of dust particles can accumulate.
Such homogeneous, porous, grayish-yellow rocks are called loess.

Glacier activity

Human activity

Humans play a major role in changing the relief. The plains are especially strongly changed by its activities. People have been settling on the plains for a long time; they build houses and roads, fill up ravines, and construct embankments. Man changes the relief during mining: huge quarries are dug, heaps of heaps are piled up - dumps of waste rock.

Scale human activity can be compared with natural processes. For example, rivers develop their valleys, carrying out rocks, and humans build canals of comparable size.

Landforms created by humans are called anthropogenic. Anthropogenic changes in relief occur with the help of modern technology and at a fairly fast pace.

Moving water and wind perform enormous destructive work, which is called (from Latin word erosio corrosion). Land erosion is a natural process. However, it intensifies as a result economic activity people: plowing slopes, deforestation, excessive grazing, building roads. In the last hundred years alone, a third of all the world's cultivated land has been eroded. These processes reached their greatest extent in large agricultural regions of Russia, China and the USA.

Formation of the Earth's relief

Features of the Earth's relief

The relief of our planet amazes with its diversity and unshakable grandeur. Wide plains, deep river valleys and pointed spiers of the highest peaks - all this, it would seem, has adorned and will always adorn our world. But this is not true at all. In fact, the Earth's topography is changing.

But to notice these changes, even several thousand years are not enough. What can we say about life ordinary person. The development of the earth's surface is a complex and multifaceted process that has been going on for several billion years. So, why and how does the Earth's topography change over time? And what lies behind these changes?

Relief is...

Given scientific term comes from the Latin word relevo, which means “I lift up.” In geomorphology, it means the totality of all existing irregularities of the earth's surface.

Among the key elements of relief, three stand out: a point (for example, a mountain peak), a line (for example, a watershed) and a surface (for example, a plateau). This gradation is very similar to the identification of basic figures in geometry.

The terrain can be different: mountainous, flat or hilly. It is represented by a wide variety of forms, which may differ from each other not only in their appearance, but also origin, age. IN geographical envelope Our planet's topography plays an extremely important role. First of all, it is the basis of any natural-territorial complex, like the foundation of a residential building. In addition, it is directly involved in the redistribution of moisture throughout and also participates in the formation of climate.

How does the Earth's topography change? And what forms of it are known to modern scientists? This will be discussed further.

basic forms and age of relief forms

Landform is a fundamental unit in geomorphological science. If we talk in simple words, then this is a specific unevenness of the earth's surface, which can be simple or complex, positive or negative, convex or concave.

The main forms of landforms include the following: mountain, basin, hollow, ridge, saddle, ravine, canyon, plateau, valley and others. According to their genesis (origin), they can be tectonic, erosional, aeolian, karst, anthropogenic, etc. By scale, it is customary to distinguish planetary, mega-, macro-, meso-, micro- and nanoforms of relief. Planetary (the largest) include continents and the ocean floor, geosynclines and mid-ocean ridges.

One of the main tasks of geomorphological scientists is to determine the age of certain landforms. Moreover, this age can be either absolute or relative. In the first case, it is determined using a special one. In the second case, it is established relative to the age of some other surface (here it is appropriate to use the words “younger” or “older”).

The famous relief researcher V. Davis compared the process of its formation with human life. Accordingly, he identified four stages of development of any relief form:

• childhood;
• youth;
• maturity;
• decrepitude.

How and why does the Earth's topography change over time?

In our world, nothing is eternal or static. In the same way, the topography of the Earth changes over time. But it’s almost impossible to notice these changes, because they last hundreds of thousands of years. True, they manifest themselves in earthquakes, volcanic activity and other earthly phenomena that we are accustomed to calling cataclysms.

The main root causes of relief formation (as, indeed, any other processes on our planet) are the energy of the Sun, Earth, and space. The Earth's topography changes constantly. And any such changes are based on only two processes: denudation and accumulation. These processes are very closely interrelated, like the well-known “yin-yang” principle in ancient Chinese philosophy.

Accumulation is the process of accumulation of loose geological material on land or the bottom of reservoirs. In turn, denudation is the process of destruction and transfer of destroyed rock fragments to other areas of the earth's surface. And if accumulation tends to accumulate geological material, then denudation tries to destroy it.

The main factors of relief formation

The pattern is formed due to the constant interaction of endogenous (internal) and exogenous (external) forces of the Earth. If we compare the process of relief formation with the construction of a building, then endogenous forces can be called “builders”, and exogenous forces can be called “sculptors” of the earth’s relief.

Internal (endogenous) include volcanism, earthquakes, and external (exogenous) - the work of wind, flowing water, glaciers, etc. The latter forces are engaged in the peculiar design of relief forms, sometimes giving them bizarre outlines.

In general, geomorphologists identify only four factors of relief formation:

• internal energy of the Earth;
• universal force of gravity;
• solar energy;
• space energy.

From the very beginning of the discussion of the problem of formation globe It was the mountains that confused scientists. Because if we assume that at first the Earth was a fiery, molten ball, then its surface after cooling should remain more or less smooth... Well, maybe slightly rough. Where did the high mountain ranges and the deepest depressions in the oceans come from?

In the 19th century, the dominant idea became the idea that from time to time, for some reason, hot magma from within attacks the stone shell and then mountains swell in it and ridges rise. Are they rising? But why then are there so many areas on the surface where the ridges run in parallel folds next to each other? When swelling each mountainous region should have the shape of a dome or bubble... It was not possible to explain the appearance of folded mountains by the action of vertical forces coming from the depths. The folds required horizontal forces.

Now take the apple in your hand. Let it be a small, slightly wilted apple. Squeeze it in your hands. Look how the skin has wrinkled, how it is covered with small folds. Imagine that an apple is the size of the Earth. The folds will grow and turn into tall mountain ranges... What forces could compress the earth so much that it becomes covered with folds?

You know that every hot body contracts when it cools. Perhaps this mechanism is also suitable for explaining folded mountains on the globe? Imagine - the molten Earth has cooled and covered with a crust. The crust or bark, like a stone dress, turned out to be “tailored” to a specific size. But the planet is cooling further. And once it cools down, it shrinks. It is no wonder that over time the stone shirt turned out to be too big and began to wrinkle and wrinkle.

This process was proposed by the French scientist Elie de Beaumont to explain the formation of the Earth's surface. He called his hypothesis contraction from the word “contraction,” which translated from Latin means compression. One Swiss geologist tried to calculate what the size of the globe would be if all the folded mountains were smoothed out. The result was a very impressive value. The radius of our planet would increase by almost sixty kilometers!

The new hypothesis gained many supporters. The most famous scientists supported her. They deepened and developed individual sections, turning the assumption of the French geologist into a unified science about the development, movement and deformation of the earth's crust. In 1860, this science, which became the most important section of the complex of earth sciences, was proposed to be called geotectonics. We will continue to call this important section the same way.

The hypothesis of contraction or compression of the Earth and the wrinkling of its crust was especially strengthened when large “thrust faults” were discovered in the Alps and Appalachians. This term is used by geologists to designate discontinuities in underlying rocks. rocks when some of them seem to be pushed over others. The experts rejoiced; the new hypothesis explained everything!

True, a small question arose: why were the fold mountains not evenly distributed over the entire surface of the earth, like on a wrinkled, shriveled apple, but gathered in mountain belts? And why were these belts located only along certain parallels and meridians? The question is trivial, but insidious. Because the contraction hypothesis could not answer it in any way.