How does the earth's topography change over time? The main forms of the earth's relief. Why does the earth's topography change? Reasons for the transformation of the earth's surface

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

The action of gravity

Under the influence of gravity, rocks that are destroyed move but the surface of the Earth from elevated areas to lower ones. Stone blocks, crushed stone, sand often rush down from steep mountain slopes, giving rise to landslides and screes.

Under the influence of gravity, 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 water bodies, on the slopes of hills and mountains after heavy rains or snow melt. The upper loose layer of rocks becomes heavier when saturated with water and slides along the lower, water-impervious layer. Heavy rains and rapid snowmelt also cause mudflows in the mountains. They move down the slope with destructive force, demolishing everything in their path. Landslides and mudflows lead to accidents and deaths.

Activity of flowing waters

The most important relief changer is moving water, which performs great destructive and creative work. Rivers cut wide river valleys in the plains, deep canyons and gorges in the mountains. Small water streams create a ravine-beam relief on the plains.

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

Karst

In areas close to earth's surface Easily soluble rocks (limestone, gypsum, chalk, rock salt) occur, amazing natural phenomena are observed. Rivers and streams, dissolving rocks, disappear from the surface and rush into the depths of the earth's interior. Phenomena associated with the dissolution of surface rocks and are called karst. The dissolution of rocks leads to the formation of karst landforms: caves, abysses, mines, funnels, sometimes filled with water. The most beautiful stalactites (multi-meter lime "icicles") and stalagmites ("columns" of lime growths) form bizarre sculptures in the caves.

wind activity

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

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

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

Glacier activity

human activities

Man plays an important role in changing the relief. The plains were especially strongly changed by his activity. People have long settled on the plains, they build houses and roads, fill up ravines, build embankments. A person changes the relief during mining: huge quarries are dug out, heaps of waste heaps are poured - heaps of waste rock.

The scale of human activity can be compared with natural processes. For example, rivers develop their valleys, carrying out rocks, and a person builds canals comparable in size.

Landforms created by man are called anthropogenic. Anthropogenic change in relief occurs with the help of modern technology and at a fairly fast pace.

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

Formation of the Earth's relief

Features of the Earth's relief

Rivers and their tributaries are the water arteries of our planet. They carry excess water from land to the ocean and play an active role in the ongoing transformation of the Earth's topography.

The Amazon is the deepest river in the world. Every second it carries about 200 thousand m³ of water into the Atlantic Ocean. It is fed by seventeen large tributaries, and the area of the drainage basin, which occupies almost the entire northern part South America, is approximately 7 million km². The length of the Amazon is about 7000 km, the width is often more than 10 km. The river is navigable for 1600 km from the mouth.

River of Records

The Amazon is the central artery, from which tributaries branch off, in themselves very large rivers. The origins of many of them are in the Andes (Rio Negro, Purus, Madeira). Others flow from the Brazilian plateau in the south (Tapajos, Xingu), and a smaller part from the north, from the Guiana plateau. When a river merges with one or more tributaries, such as the Rio Negro, the volume of water carried increases so much that a kind of inland sea is formed.

The Amazon flows on both sides of the equator, in a region with a humid, hot climate that receives between 1,500 and 3,000 mm of precipitation per year. Watercourses from the slopes of the Andes, fed by melting snow, are replenished by surface runoff water, since soils of rain equatorial forests unable to absorb the entire volume precipitation. Watercourses merge with shallow rivers, and those carry their waters to the main artery. Flowing into the ocean, the Amazon reaches a width of 60 km at the mouth and forms an estuary with many islands.

Terrain change

Flowing waters not only carry excess water from land to sea. Along the way, they also change the terrain of the planet, restrained or violent, smooth or intermittent. This process involves huge volumes of transported rocks, reaching hundreds of millions of tons annually. Even the calmest-looking rivers never cease their activity for a moment, carrying dissolved substances, such as calcium bicarbonate, washed out of the deteriorating limestones.

Water carries loose, unconsolidated material: sand, clay and soil. As a result, rivers often take on a characteristic color. The water of some tributaries of the Amazon, such as the Rio Negro, seems dark due to the presence of iron and organic oxides in it. The waters of others abound in silt and appear whitish (Madeira). Downstream from the confluence with the Rio Negro, the waters of the Amazon flow for a long time in two immiscible multi-colored streams.

Hard way

lowland rivers equatorial belt they carry only small suspended particles and are not able to effectively destroy the strong bedrock lining their bottom. Therefore, the channels of African rivers abound in rapids and waterfalls, which form where the rocks are especially resistant to erosion.

Erosion processes are most noticeable in mountainous regions, where surface slopes are significant. The channels of mountain rivers are often strewn with large fragments of rocks, which, during periods of high water, move, slide, turn over and break up when rubbing against each other. When the watercourse enters the plain, all this clastic material is deposited in the form of fan-shaped accumulations - alluvial fans. When rivers flow into lakes, the same thing happens: a small delta is formed - the first stage in the formation of a lake basin.

large scale work

For many thousands of years, watercourses have carved incised valleys, gorges and canyons in the rocks. Steep-sided valleys usually form in hard rock, which water can only break down with the help of abrasive (abrasive) material - sand, gravel and pebbles. The rotational movement of water in whirlpools leads to the formation of natural depressions in the channel, called giant boilers.

In a similar way, rivers wash away steep banks and, by widening their course, create picturesque meanders. However, further expansion of river valleys requires the intervention of other mechanisms of the erosion process. Weathering, crushing and landslides gradually smooth out the forms created by the stream.

Captive or free

Rivers flowing through vast alluvial plains are freer in the choice of channel configuration than rivers locked in narrow gorges. Plain rivers often change their path, randomly meandering (wandering) within the main direction, such as the Okavango River in Botswana.

Sometimes rivers change course even more abruptly. As a result of the displacement of earth masses and changes in the water level, rivers capture neighboring watercourses and direct them into their own channel. Thus, the Moselle River in France, which once flowed into the Meuse, has now become a tributary of the Merte River.

Delta

River deltas are unstable structures, the ongoing reconstruction of which is based both on the accumulation of sediments carried by rivers and on their removal by the advancing sea. But luck in the battle between sea and land always favors the sea.

The area of the Nile delta in Egypt with an area of 24 thousand km2 is one of the most densely populated in the world, as is the delta of the legendary Ganges flowing in India. People have long settled in these low-lying, fertile regions. However, the boundary between the elements of water and land is changeable. Due to floods, rivers often change their course. Old channels, remaining higher, dry up, forming new lakes and swamps. Even where the sea has already receded, land areas are not protected from the intrusion of water.

The origin of the word "delta" is closely related to the Nile. This name was given to the lower reaches of the Nile by Herodotus in the 5th century BC. BC e., since the mouth of the river is similar in shape to an inverted capital letter D of the Greek alphabet. Since then, this term has been used to denote a lowland composed of river sediments at the mouth of a river flowing into a sea or lake. The Rhone even has two deltas: one, small, formed when the river flows into Lake Geneva, the other, much larger, in the Camargue, when it flows into the Mediterranean Sea.

Deltas can have a different shape. Some rivers, such as the Mississippi, branch into several branches, so that their delta resembles a goose foot, others, such as the Ebro in Spain or the Po in Italy, form arcs. The variety of forms of the delta is determined both by the creative work of the river and by the opposition of the sea, the currents of which either prevent sedimentation or help wash sandbars, as happens in Venice. Thus, the movement of the sediments of the Po River by the sea current led to the formation of a coastal rampart in the northern part of the delta, which cut off the Venetian lagoon from the sea. The study of displacements of the littoral zone shows that the shape coastline, the channels of rivers and their tributaries are changing over the course of several millennia. Archival documents make it possible to trace the movements of the Rhone in the Camargue region and measure them in kilometers.

"Multiple" delta

A delta can be formed by several deltas located one behind the other, such as the Mississippi Delta. Having covered a path of more than 6000 km, the river deposits sediments in the Gulf of Mexico, the annual volume of which is about 20 tons. No wonder the river transports so much material, because it collects water from more than a third of the United States and flows into such large rivers as the Missouri, Arkansas, Red River. In 5,000 years, six interlocking deltas formed at the mouth of the Mississippi, forming one in the shape of a goose foot.

Material quality

To win the battle with the sea and form a delta, the river must deposit a huge amount of alluvium. No less important is the nature of the transferred material. The Amazon basin is dominated by chemical weathering, so there is little sand and gravel. Although the annual solid flow of the river is about 1.3 million tons per day, it is dominated by fine particles, which are carried northward by the coastal current. That is why, when it flows into the Atlantic Ocean, the Amazon forms a huge estuary, and not a delta. However, active deforestation in the region leads to the destruction of the above ground cover and contributes to erosion. This can change the composition of the transported material, the direction of the channel, the speed of the current, and ultimately lead to the transformation of the estuary into a delta.

Although in other regions the amount and quality of sediment transported is sufficient to preserve the delta, the construction of dams and power plants on rivers and their tributaries can reduce sedimentation and lead to the victory of the sea.

Voted Thanks!

You may be interested in:

The health and life of any person directly depend on the processes taking place in the lithosphere. The economic activity of people also depends on these processes. Most of these processes occur under the direct influence of natural forces are of a spontaneous nature.

Natural and natural phenomena can be divided into 2 groups:

Collapses, screes, landslides, mudflows, occurring due to the action of the forces of gravity.
Volcanism and earthquakes occurring due to the internal energy of the Earth.

Volcanism is a very large-scale manifestation. Most of the country's volcanoes are concentrated on the Kuril Islands and Kamchatka. Of the 160 volcanoes existing in Russia, 40 are located on the territory of the Kuril Islands. Active volcanoes include Sarychev, Berg, Bezymyanny, Kizimen, Shiveluch, Klyuchevskaya Sopka, Karymskaya Sopka and Mutnovsky volcano. Columns of volcanic dust and gases emitted into the atmosphere by volcanoes rise to a height of 10-20 km, after which they begin to settle to the ground.

Earthquakes are the most dangerous natural phenomena, which are almost impossible to predict. On the territory of the Russian Federation, frequent and strong earthquakes most often occur in the area of Sakhalin Island, the Kuril Islands and Kamchatka. One of the most recent devastating earthquakes happened in 1995. Because of it, about 2,000 people died and the settlement of Neftegorsk was completely destroyed. Among the Russian mountainous regions, the most dangerous, regarding the occurrence of earthquakes, include: the Trans-Baikal and Baikal mountains, the Sayans, Altai and the Caucasus. About 40% of the territory of the Russian Federation is considered seismically hazardous.

In areas where volcanoes are common, there are also geysers and hot volcanoes. Underground hot water can be used to generate electricity and heat residential premises. For example, an experimental geothermal power plant is successfully operating in Kamchatka.

Landslides and screes most often occur in mountainous areas with a strong intersection of the relief. Rocks that have collapsed, under the action of gravity, collapse and pull new parts of the debris along with them. Mostly, the cause of their occurrence is tremors or water activity. Not uncommon in mountainous areas and mudflows. They are a mixture of stones, clay and mud, which is formed during prolonged rains and rapidly descends. Mudflow moves at a high speed and if there is any settlement, bridge, road, dam or any other structure in its path, it can destroy them. Altai and the Caucasus are much more likely than other mountainous regions to encounter this natural phenomenon.

There is also such a type of natural phenomena as a landslide. Most often, its formation occurs in conditions of alternating impervious and aquiferous rocks. Under such conditions, the upper layers begin to slide along a more slippery aquiclude and a landslide is formed. Most often, landslides can be found on the Volga, as well as on steep banks that are washed away by water.

The impact of human activity on the relief

The terrain is formed not only because of internal and external factors, but also because of human activities. Most of all, the relief is influenced by such types of work as laying roads, mining, construction of underground utilities and structures, development of forestry and agriculture. Because of these reasons, the integrity of the rock is very often violated, and the surface of the earth begins to subside. In some regions, man-made earthquakes may appear, provoked by the extraction of a huge amount of some minerals from the earth. Similar earthquakes often occur in Western Siberia and the Urals. Due to mining, many waste heaps, mines and quarries appear.

Most waste industrial dumps pose a risk to human health. A lot of such dumps are located on the territory of the Kuznetsk coal basin and in some regions of Siberia and Far East. It is in these areas that minerals are mined in an open way. Also, the relief changes during the intake of artesian water and during underground work. Because of this, rather deep funnels can appear in the relief. Several such craters were found in Moscow, they reach a depth of 4 and a diameter of 45 meters. Similar funnels in Kuzbass reach a depth of 70 meters. Soil erosion and ravine activity are an example of how agriculture should not be carried out - with intensive plowing of the land and the removal of natural vegetation.

Thus, human economic activity is actively involved in cardinal changes in the land relief. Together with natural relief forms, today there are many artificial ones: various structures, tunnels, bridges, dams, buildings. For many thousands of years, giant zones of continuous settlement were formed. Man-made forms that have been created by man have completely changed the surface of the earth, while influencing surface water runoff and climate.

Indirect influence on the relief of a person

A person can also influence changes in the land relief indirectly. A person, not planned or unintentionally, can change the conditions of morphogenesis, slow down or intensify the natural processes of accumulation or denudation. As a result, anthropogenic gully formation and soil erosion are significantly increased. Due to the drainage of swamps, the relief of their surface is changing. Unlimited livestock grazing, as well as road digression, are the reason for the revival of the dynamics of ash sandy accumulative landforms. In places where active military operations are carried out, special forms of mesorelief and microrelief may arise - these are bomb craters, defensive ramparts, trenches and trenches.

Actions taken by people consciously or unconsciously are taken in conditions of possible uncertainty, and any specific situation can lead to a threat in some form. Any human activity that takes place at the boundaries of a natural-anthropogenic or natural system can cause geomorphological risk. The risk arises from the feeling or presence of danger emanating from a certain geomorphological object and is associated with the vigorous activity of the subject of danger - a person. For this purpose, ecological geomorphology develops certain methods and principles that make it possible to identify dangerous geomorphological objects and processes and predict their development in order to minimize the cost and degree of risk.

Natural natural processes in most cases are technogenically predetermined. For example, large-scale deforestation in regions with mountainous terrain becomes the reason for the activation of the processes of formation of mudflows and landslides. Recently, gravitational and fluvial-glacial processes have become more frequent, which are formed due to the development of meadows high in the mountains. The frequency of mountain avalanches is increasing and causing agriculture significant damage. Buildings, bridges, mountain roads are destroyed. Usually, phenomena that pose some kind of threat from the environmental side appear suddenly. Specialists, engaged in the study of their emergence and development, identified several important factors that make it possible to predict the course of their development in the future. Their actions are associated not so much with anthropogenic or natural factors, but with the simultaneous activity and influence of people in places prone to these phenomena.

To predict the development of any exogenous processes, remote sensing methods are the most effective. They are able to increase the objectivity of the geographical forecast, as well as significantly improve the quality of the material obtained. Under such conditions, it is possible to predict the nature and strength of exogenous processes.

Answer left Guest

As a result of the rapid development of economic activity, there is an ever-increasing human impact on the relief.

Mining has the greatest impact on the earth's surface and subsoil.
production, especially in open pit mining. How
already noted above, this method removes significant areas
land, pollution occurs environment various
taxicants (especially heavy metals). Local bowing of the earth's crust
in coal mining areas are known in the Silesian region of Poland, in the UK, in
USA, Japan, etc. Man geochemically changes the composition of the earth's crust, mining in
a huge amount of lead, chromium, manganese, copper, cadmium, molybdenum, etc.

Anthropogenic changes in the earth's surface are also associated with construction
large hydraulic structures. The total impact of the weight of the dams, as well as leaching processes, lead to significant settlement of their foundations with the formation of cracks (fractures up to 20 m long were noted in the foundation of the Sayano-Shushenskaya HPP dam) . Most of the Perm region annually settles by 7 mm, since the bowl of the Kama reservoir presses against the earth's crust with great force. The maximum values and rates of subsidence of the earth's surface, caused by the filling of reservoirs, are much less than during oil and gas production, large pumping of groundwater. For comparison, the Japanese cities of Tokyo and Osaka are due to pumping
groundwater and compaction of loose rocks for last years descended 4 m
(with an annual precipitation rate of up to 50 cm).

Ecological state subsoil is determined primarily by the strength and nature of the impact on them of human activity. In the modern period, the scale of anthropogenic impact on the earth's interior is enormous. In just one year, tens of thousands of mining enterprises in the world extract and process more than 150 billion tons of rocks, pump out billions of tons of cubic meters of groundwater, and accumulate mountains of waste.

Man extracts minerals, as a result of which quarries are formed, builds buildings, canals, makes embankments and fills up ravines. In the process of urbanization, the relief of the developed territory undergoes transformations in accordance with the needs of urban development.

The impact of man on the relief today is also reflected in the unintentional creation of undesirable surface forms, as well as in the direct or indirect impact on natural geomorphological processes, accelerating or slowing them down. Thus, during agricultural activities, a person often causes and accelerates harmful processes, such as water (including irrigation), wind and pasture erosion, secondary salinization, swamping, increased thermokarst processes in the polar regions, etc. Agriculture on vast areas is especially threatened by accelerated water and wind erosion of the soil.

To reduce the degree of manifestation of these processes, purposeful activity should be opposed to them.

A person also influences endogenous processes. For example, blasting using charges of enormous power is accompanied, especially in mountainous areas, by artificially caused movements in the earth's crust (earthquakes) and various heaps. Depending on the modifications of the forms of the earth's surface, a fundamental restructuring of the geomorphological basis of many natural landscapes takes place (especially in highly developed economic regions and countries).

A person can transform the relief of the earth's surface directly (making an embankment, pulling out a foundation pit) or acting on natural processes relief formation - accelerating or (less often) slowing them down. Landforms created by man are called anthropogenic(from the Greek. a'ntro-pos - a person and -ge'-nes - giving birth, born).

Direct human impact on the terrain

Man began to interfere in the life of the earth's crust, being a powerful relief-forming factor. Man-made landforms arose on the earth's surface: swells, excavations, mounds, quarries, pits, embankments, waste heaps, etc. Cases of bowing of the earth's crust under large cities and reservoirs were noted, the latter in mountainous areas led to an increase in natural seismicity. Examples of such artificial earthquakes, which were caused by the filling of basins of large reservoirs with water, are found in California, the USA, and on the Hindustan Peninsula. This type of earthquake has been well studied in Tajikistan on the example of the Nuker reservoir. Sometimes earthquakes can be caused by pumping out or pumping waste water with harmful impurities deep underground, as well as intensive oil and gas production at large deposits(USA, California, Mexico). A person using machines and technical means creates new landforms: as denudation - quarries, mines, excavations, canals and drainage networks, terraced and cut slopes, leveled hills and small mountains (for example, during the development minerals), subsidence of the surface (above mine workings and when pumping groundwater), and accumulative - embankments, dams, mounds, dumps, waste heaps, filled ravines, beams and small valleys or depressions. At the same time, he can artificially direct the activity of natural geomorphological processes to create a relief that is convenient for him, for example. fencing off part of the low-lying sinking coasts, the creation of arts. lagoons and their filling not only by technical backfilling of soil, but also by natural accumulation of sediments in lagoons (polders in the Netherlands). Mining has the greatest impact on the earth's surface and subsoil, especially with open pit mining. As noted above, with this method, significant areas of land are withdrawn, the environment is polluted with various toxins (especially heavy metals). Local subsidence of the earth's crust in areas of coal mining is known in the Silesian region of Poland, in Great Britain, in the USA, Japan, and others. Man geochemically changes the composition of the earth's crust, extracting lead, chromium, manganese, copper, cadmium, molybdenum, and others in large quantities.

Anthropogenic changes in the earth's surface are also associated with the construction of large hydraulic structures. By 1988, more than 360 dams (150–300 m high) had been built all over the world, of which 37 were built in our country. Shushenskaya hydroelectric power station marked cracks up to 20 m long). Most of the Perm region annually settles by 7 mm, since the bowl of the Kama reservoir presses against the earth's crust with great force. The maximum values and rates of subsidence of the earth's surface, caused by the filling of reservoirs, are much less than during oil and gas production, large pumping of groundwater.

For comparison, we point out that the Japanese cities of Tokyo and Osaka, due to the pumping of groundwater and the compaction of loose rocks, have sunk by 4 m in recent years (with an annual precipitation rate of up to 50 cm). Thus, only detailed studies of the relationship between natural and anthropogenic relief-forming processes will help to eliminate the undesirable consequences of the impact of human economic activity on the earth's surface.

Indirect influence of man on the relief

Previously, it was most felt in agricultural areas. Deforestation and plowing of slopes, especially irregular, from top to bottom, created conditions for the rapid growth of ravines. The construction of buildings and engineering structures, creating additional loads on the slopes, contributes to the occurrence or intensification of landslides.

Reservoirs are created in natural relief depressions. But water, having created a free surface at a new level, begins processing the banks of reservoirs. Ravine erosion, planar washout, landslides are activated. At the same time, the basis of erosion increases near the rivers flowing into the reservoir, and alluvium accumulates in their channels. Erosion often increases downstream of the reservoir dam, as water flow less loaded with sediment, a significant part of which is deposited in the stagnant water of the reservoir. Dozens of years will pass before the emerged reservoir and the shape of the slopes of its banks, the new regime of watercourses and the shape of their channels will come into line.

Indirect anthropogenic impact on relief formation consists in an intentional or unplanned change in the conditions of morphogenesis, intensification or slowdown natural processes denudation and accumulation in the course of farms, activities; as a result of this, there is increased soil erosion, anthropogenic gully formation or acceleration of the growth of ravines in length and depth, a change in the topography of the surface of swamps as a result of their drainage, increased deflation and a revival of the dynamics of accumulative sandy eolian landforms due to excessive grazing and road degression. Specific forms micro- and mesorelief arise as a result of warfare. actions (trenches and trenches, defensive, ramparts, bomb funnels, etc.).

Geomorphological risk is a particular action of a person (his social, economic and social institutions), carried out at the boundary of the stability of a natural or natural-anthropogenic geomorphological system. This action (conscious or unconscious) is taken under conditions of uncertainty, which in a particular situation leads to some form of risk. The risk is generated by the presence and feeling of danger - in this case coming from one or another geomorphological object (geomorphological hazard. The risk is associated with the active actions and functioning of the subject of danger - a person. In ecological geomorphology, a system of principles of methods for identifying and mapping dangerous geomorphological processes and objects, forecasting their development, methods of prevention, protection and management of hazardous processes in order to reduce the degree and cost of risk.

Unfavorable natural phenomena that create an ecological and geomorphological hazard and are catastrophic in the mountains are such exogeomorphological processes as snow avalanches, mudflows, landslides, landslides, etc. For the most part, these processes and phenomena are inevitable, difficult to predict or practically unpredictable in advance. At the same time, spontaneous destructive processes and phenomena, being natural in nature, often turn out to be technogenically (anthropogenically) predetermined. For example, the deforestation in the mountains due to the energy crisis over the past 10-15 years has been the reason for the intensification of the processes of formation of mudflows and landslides within the South-Eastern Caucasus. Mudflows - mud-stone and mud are typical for all altitudinal belts of this region: the high-altitude parts of the basins of the river. Gudialchay, Jimichay, Babachay, Gusarchay. Their foci in the basins of the river. Gudialchay, Jimichay, Atachay, Tugchay, Shabranchay, Takhtakerpu are confined to zones of anthropogenic impact on the geosystems of these regions.

Intensive development of alpine meadows, which has been taking place in recent years, leads to a sharp increase in fluvial-glacial and gravitational processes. This is an increase in the frequency of descent snow avalanches, formation of landslides, melting and shifts of mountain glaciers on the peaks of Shahdag, Bazarduzi, etc. Avalanche processes are observed in the high and mid-mountain belts of the Greater Caucasus, where they are confined to the steep slopes of the ridges and their peaks (Tufan, Bazarduzi, Shakhdag, Gyzylkaya, Babadag). They occur frequently and in large numbers, thereby causing significant damage to the economy, putting mountain roads, bridges, buildings, and other geomorphological engineering structures out of action.

It is known that northeastern part The Greater Caucasus is a model area for the intensive development of various types of landslide processes. They are most developed in the middle and low-mountain zones, where there is an intensive destruction of the slopes of river valleys, gullies, ravines, as well as landslide displacements intensively destroy the slopes of mountain ranges. Landslides are observed in areas with both humid and relatively arid-arid climates and cause great harm to the economy of this region (especially in the basins of the rivers Gudialchay, Gilgilchay, Atachay, etc.).

In the region under study, the development of landslide and other gravitational-denudation processes is greatly influenced by intensive modern neotectonic movements and active present stage development of disjunctive dislocations, to which the main ecologically dangerous exodynamic processes are confined. The wide distribution of highly elevated horst-synclinal plateaus with steep slopes creates favorable conditions for the development of landslide processes. Large landslides - streams are confined to the slopes of such horst-synclinal plateaus as Afurdzha, Khizinsky, Budugsky, Gyzylkainsky, Girdagh and others (Budagov, 1977).

At present, such a statement of the question is being raised - risk management generated by dangerous natural and man-made phenomena (Seliverstov, 1994; Grigoriev, Kondratiev, 1998, etc.). Ecologically dangerous phenomena usually appear suddenly. Studies of their origin and development, conducted recently within the eastern part of the Greater Caucasus, made it possible to identify some important factors - indicators that make it possible to predict the further course of development of these processes. They are associated not so much with natural or anthropogenic factors, but with their simultaneous influence and the activities of the population in places prone to these phenomena.

In our opinion, remote sensing methods are the most effective for predicting the development of exogenous processes in order to monitor current fluctuations in their distribution area in such remote mountainous regions as the Greater Caucasus. They increase the objectivity of the geographical forecast, improve the quality of the material obtained for detailed analysis, making it possible to judge the nature and strength of exogenous processes in the near future.

Man and the relief of the earth's surface have a comprehensive impact on each other. Since ancient times, relief has determined different kinds human activity, the nature of settlements and migrations depended on it. At present, despite technological progress, the relief continues to have a different impact on a person and his activities. The features of the laying and construction of various engineering structures, as well as the extraction of minerals, depend on the relief and geological structure of the territory. The ecological role of modern relief and relief-forming processes is great. For example, the distribution and migration of pollutants is associated with relief. Great importance have dangerous and unfavorable geomorphological processes. Some of which cause significant harm to a person and objects of his economic activity.

It is necessary to pay attention to the other side of the issue - the anthropogenic factor in relief formation.

A person can transform the relief of the earth's surface directly (making an embankment, pulling out a foundation pit) or by influencing the natural processes of relief formation - accelerating or (less often) slowing them down. Landforms created by man are called anthropogenic.

The direct impact of man on the relief is most pronounced in the areas of mining. Underground mining is accompanied by the removal to the surface a large number waste rock and the formation of dumps, usually having a conical shape - waste heaps(lat.; literally - earthen cones). Numerous waste heaps create a characteristic landscape of coal-mining areas.

In open-pit mining, significant dumps of overburden are usually created first - rocks that lie above the layer that contains the mineral; productive layer development goes the way excavation of vast depressions - quarries, the relief of which is very complex, it is determined by the geological structure (areas with a low content of minerals can remain intact), the need to protect the walls of the quarry from collapsing, to create a relief convenient for transport access (Fig. 59).

Significant changes in the relief are made during transport, industrial and civil construction. Sites are leveled for structures, embankments and excavations are created for roads.

Agriculture has a direct impact on the relief, mainly in the mountainous regions of the tropics. Terracing of slopes to create horizontal platforms is widespread here.

The indirect influence of man on the relief was first felt in agricultural areas. Deforestation and plowing of slopes, especially irregular, from top to bottom, created conditions for the rapid growth of ravines. The construction of buildings and engineering structures, creating additional loads on the slopes, contributes to the occurrence or intensification of landslides.

In areas of underground mining, extensive ground subsidence can be observed, as collapses occur in worked-out mines and adits.

Reservoirs are created in natural relief depressions. But water, having created a free surface at a new level, begins processing the banks of reservoirs. Ravine erosion, planar washout, landslides are activated. At the same time, the basis of erosion increases near the rivers flowing into the reservoir, and alluvium accumulates in their channels. Downstream of the reservoir dam, erosion often increases, since the water flow is less loaded with sediment, a significant part of which is deposited in the stagnant water of the reservoir.

Dozens of years will pass before the emerged reservoir and the shape of the slopes of its banks, the new regime of watercourses and the shape of their channels will come into line.

Human influence is experienced not only by exogenous, but also by endogenous processes. Large reservoirs are masses of water with colossal weight: each cubic kilometer of water has a weight of 1 billion tons, and, for example, the Bratsk reservoir contains more than 169 km3 of water. Under the weight of water, the earth's crust sags, and in earthquake-prone areas, the likelihood of earthquakes increases.

GEOMORPHOLOGICAL RISK - one or another action of a person (his public, economic and social institutions) carried out on the border of the stability of a natural or natural-anthropogenic geomorphological system. This action (conscious or unconscious) is taken under conditions of uncertainty, which in a particular situation leads to some form of risk. The risk is generated by the presence and feeling of danger - in this case coming from one or another geomorphological object (geomorphological hazard. The risk is associated with the active actions and functioning of the subject of danger - a person. In ecological geomorphology, a system of principles of methods for identifying and mapping dangerous geomorphological processes and objects, forecasting their development, methods of prevention, protection and management of hazardous processes in order to reduce the degree and cost of risk.

Previous6789101112131415161718192021Next

VIEW MORE:

Slides and text of this presentation

slide 1

Development of landforms geography teacher: Kildeshova O.V.

slide 2

Goals:
To acquaint students with the influence of external and internal factors on the formation of relief. Show the continuity of the development of the relief. Consider the types of natural phenomena, the causes of occurrence. Tell about the influence of man on the relief. Course of the lesson: 1. Organizational moment.2. Greeting.3. The message of the topic and purpose of the lesson.4. Recording the topic of the lesson in a notebook.5. Work on a new topic. Check homework: Let's remember the definition of minerals and how they are classified? What are the mineral resource bases?

slide 3

The relief is constantly changing under the influence of exogenous (external) and endogenous (internal) factors. Let's draw a diagram in notebooks with explanations:
Relief
Endogenous (internal factors)
Exogenous (external factors)

slide 4

Endogenous processes are called neotectonic or recent. (they can appear both in the mountains and on the plains).
Endogenous factors in folded areas on platforms (the emergence of mountains, mountains - volcanoes, grabens, horsts, intermountain basins)

slide 5

In the mountains, the movements of the earth's crust are most active. In the Caucasus, movements occur at a speed of 5–8 cm per year, in young mountains, where the earth's crust is plastic, movements are accompanied by the formation of folds. 1 cm per year.

slide 6

Exogenous processes are processes that occur under the influence of flowing waters (rivers, glaciers and mudflows), permafrost and wind.

Slide 7

Exogenous processes are processes that occur under the influence of flowing waters (rivers, glaciers and mudflows), permafrost and wind.
Exogenous factors
Glaciation moraines, outwash plains, sheep foreheads, lakes.
flowing water river valleys, ravines, hollows.
wind-eolian relief forms (dunes, dunes).
Human

Slide 8

Man is also a powerful relief-forming force. During the extraction of minerals, huge quarries are formed. Waste rock heaps speak of useful extraction minerals are waste heaps. Quarries and waste heaps create a (lunar) career landscape. People build roads, dams, tunnels, and other economic facilities that change the terrain and often lead to the formation of landslides, landslides, etc. Natural natural phenomena in the lithosphere are earthquakes and volcanism, mudflows (mud streams), collapses. Consider spontaneous natural phenomena, write down definitions in a notebook.

Slide 9

Earthquakes are a manifestation of the latest tectonic movements of the earth's crust.

Slide 10

Mudflows are mud streams rushing from the mountains at great speed, having great destructive consequences.

slide 11

Landslides are the displacement of masses of rocks down a slope under the influence of gravity.

slide 12

Consolidation of the studied material:
What factors influence changes in relief? What landforms form endogenous processes? What processes are classified as exogenous factors? What are mudflows, landslides, earthquakes?

slide 13

Homework:
§ 8 pp. 49-56

Such plains are characterized by a complex relief, the forms of which were formed during the destruction of heights and the redeposition of materials from their destruction. The nature of the relief of the Earth's surface is closely related to these tectonic structures, and to the composition of the rocks that form them.

The activity of human society over many millennia of its existence has had a huge impact on the development of natural geological and relief-forming processes. In the second case, an anthropogenically determined relief arises.

For the first time, anthropogenic landforms arose when hunting tribes began to dig holes for catching animals, caves, and so on. There are intermediate forms of A. r. - harmful, but inevitable: careers, waste heaps, etc. A. r. is a component of the anthropogenic, or cultural, landscape.

Subsidence of the surface by 10-18 m with a diameter of several kilometers was noted. The systems of canals and ditches, laid during irrigation and melioration, belong to the proper anthropogenic landforms. Much attention is paid in our country to the issues of studying and proper regulation of processes caused by human production activities.

As noted above, as a result of diverse economic activities, anthropogenic deposits arise. The concept of the genesis of deposits is embedded in this term, in contrast to the age concept of "Anthropogenic", i.e., Quaternary deposits. As complexes, bulk, alluvial deposits, artificial reservoirs, artificially created and artificially transformed in natural occurrence are distinguished.

Anthropogenic landforms

And since that moment, human activity has played an important role in the transformation of the face of the Earth, which sometimes leads to unexpected results. Their relief is also not the same - these are different morphostructures. flat territories different type with small relief amplitudes are characteristic of platforms. In large expanses of plains, as a rule, the same layers of rocks are exposed, and this causes the appearance of a homogeneous relief.

On the plains, endogenous processes manifest themselves in the form of weak vertical tectonic movements. The diversity of their relief is associated with surface processes. The relief of mountainous countries corresponds to orogenic belts. Various types mountain relief depend on the rocks that make them up, on the height of the mountains, on the modern features of the nature of the area and on the geological history.

Mountains arose in places on the earth's surface that were subjected to intense tectonic uplift. There are 2 forms of weathering: chemical, in which it decomposes, and mechanical, in which it crumbles into pieces. As a result of cooling, deep in the bowels of the Earth, molten magma forms volcanic rocks.

Often in rocks there are multilayer horizontal stratifications and cracks. They eventually rise to the surface of the earth, where the pressure is much lower. The stone expands as the pressure decreases, and all cracks in it, respectively. For example, water that has frozen in a crack expands, pushing its edges apart.

This process is called frost wedging.

Water, flowing over the surface or soaking into the rock, brings into it chemical substances. For example, the oxygen in water reacts with the iron contained in the rock. River erosion is a combination of chemical and mechanical processes. Water not only moves rocks, and even huge boulders, but, as we have seen, it dissolves their chemical components.

Formation of the Earth's relief

The sea (you can read about what the sea is in this article) is constantly and tirelessly working on remaking the coastline. In some places it builds up something, and in others it cuts something off. Landslide gravity causes you to slide down the slope hard rocks changing the terrain. As a result of weathering, fragments of rocks are formed, which make up the bulk of the landslide. Landslides sometimes move slowly, but sometimes they move at a speed of 100 m/sec or more.

Avalanches (rock, snow, or both) result in similar disasters. A large landslide can lead to significant changes in the relief.

Centuries-old climatic fluctuations also led to significant changes in the earth's relief. In the ice polar caps, during the last ice age, huge masses of water were bound. The northern cap extended far south North America and the European continent.

The glacier, as it moves, captures, in the so-called accumulation area, a lot of rock fragments. Not only stones get there, but also water in the form of snow, which turns into ice and forms the body of the glacier. Having passed the border of the snow cover on the mountain slope, the glacier shifts to the ablation zone, that is, gradual melting and erosion.

The place where the glacier finally melts and turns into an ordinary river is often designated as the terminal moraine. Those places where long-vanished glaciers ended their existence can be found along such moraines. The glacial tributary flows into the main channel from the side valley, which is laid by it.

Internal (endogenous) are processes inside the Earth, in the mantle, core, which manifest themselves on the surface of the Earth as destructive and creative. In mountainous countries with complex terrain, individual ridges, mountain ranges and various intermountain depressions stand out. The processes on the earth's surface that affect the main landforms formed by internal, that is, endogenous processes, are also closely related to geological structures.

More interesting:

Human impact on relief and geological processes

The modern impact of man on the relief is very diverse and covers more than 70% of the land.

It manifests itself mainly in the deliberate creation of artificial landforms as a result of economic activity. For example: in the development of minerals - mines, quarries, mine workings, dumps, embankments; in industry - waste dumps, artificial sewage sedimentation tanks, etc.; in agriculture - terracing of slopes, irrigation and drainage canals, ponds and reservoirs, etc. Man radically modifies certain forms of relief, which ultimately leads to the formation of anthropogenic landscapes, which in many areas prevail over natural ones.

The impact of man on the relief is also reflected in the unintentional creation of various, as a rule, undesirable surface forms, as well as in the direct or indirect impact on natural geomorphological processes, accelerating or slowing them down. For example, during agricultural activities, a person often causes and accelerates harmful processes, such as water (including irrigation), wind and pasture erosion, secondary salinization, waterlogging, increased thermokarst processes in the polar regions, etc. Agriculture on vast areas is especially threatened by accelerated water and wind erosion of the soil. To reduce the degree of manifestation of these processes, they should be opposed by purposeful activity - technical melioration.

Man also influences endogenous processes. For example, blasting using charges of enormous power is accompanied, mainly in mountainous areas, by artificially caused movements in the earth's crust (earthquakes), the creation of heaps of various shapes and sizes. Depending on the modifications of the forms of the earth's surface (especially in highly developed countries), a radical restructuring of the geomorphological basis of many natural landscapes also takes place.

The concept of the atmosphere, weather and climate

Atmosphere (from Greek atmos- steam and sphaira- ball) - the airy outer shell of the Earth, connected with it by gravity. The composition, structure and physical processes of the atmosphere are the subject of study of meteorology. Conventionally, an altitude of 3000 km is taken as the upper boundary of the atmosphere. Clean and dry air at sea level is a mechanical mixture of gases: nitrogen - 78.09%, oxygen - 20.95, argon - 0.93, carbon dioxide - 0.03%. The content of other gases (helium, methane, hydrogen, ozone, etc.) is very low - less than 0.1%. The atmosphere contains water vapor, the amount of which varies both in space and in time. An important role in the development of terrestrial landscapes is also played by the "ozone screen", which absorbs a significant part of ultraviolet radiation. The content of carbon dioxide (CO2) in the atmosphere is low. True, its amount has increased over the past hundred years from 0.29 to 0.33%.

In addition to gases, water vapor, aerosol impurities (dust, smoke, microorganisms) are present in the atmosphere, serving as condensation nuclei necessary for the formation of clouds and fogs. According to the nature of temperature changes, the atmosphere is divided into the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The spheres are separated by transitional layers - pauses. The most active layer is the troposphere. Air mixing, cloud formation, precipitation and other physical processes and phenomena take place in it. The troposphere is in continuous interaction with other spheres of the geographic shell and is constantly under the influence of the Sun. The importance of the atmosphere for the formation of landscapes is enormous. It not only absorbs the ultraviolet radiation of the Sun, which is detrimental to all living things, but also creates thermal conditions favorable for life - the climates of the Earth.

The state of the atmosphere in a particular region of the earth's surface is expressed weather And climate.

The physical state of the atmosphere at a given point in time is called weather. It is characterized by a complex of meteorological elements and phenomena: air temperature, humidity, pressure, wind, cloudiness, precipitation, etc. It represents an external manifestation of radiation and circulation conditions, the impact of the underlying surface on them.

Climate - the statistical regime of atmospheric conditions (weather conditions) characteristic of each given place on the Earth. the main role in shaping the climate belongs solar radiation - origin of all atmospheric processes.

The influence of a heterogeneous landscape surface complicates the circulation of the atmosphere, increases the diversity of climates by the globe. There are several classifications of climates, distinguished by one or more leading signs, conditions of origin. In a generalized form, there are seven climatic zones: equatorial, subequatorial, tropical, subtropical, temperate, subpolar and polar. In them, the corresponding climate zones are distinguished, characterized by their own features of the weather regime. For example, among climates temperate zone distinguish between continental, temperate, temperate oceanic, etc.

For daily and annual course air temperatures in the surface layer are influenced by the latitude of the area, the nature of the underlying surface and its physical properties.

The atmosphere exerts pressure on the earth's surface. A very complex distribution of pressure is observed on the earth's surface, determined using isobars (lines connecting points with the same pressure). System of closed isobars with reduced pressure called in the center cyclone, and with increased pressure in the center - anticyclone.

The main reason for the change in pressure is the movement of air, its outflow from one place and inflow to another. This movement is associated with the different nature of the underlying surface, its different heating.

An important characteristic of weather and climate is precipitation, falling in the form of rain, snow, hail, cereals, drizzle. Their number is measured by the thickness of the water layer in mm, and the nature depends on the conditions of formation.

Climate and landscape

The climate influences the formation of the external appearance of the landscape, depending on whether it belongs to one or another climatic region. In addition, it directly or indirectly affects the landscape resource, many geomorphological, geochemical, biophysical and other processes occurring within the landscape and determining its dynamics. The impact of climate on the landscape is manifested in three directions: global, zonal and provincial.

The processes of moisture and heat exchange between the ocean and land determine macroclimate continents and the planet as a whole. Climatic factors also determine the system of natural (landscape) zones on the earth's surface. The degree of participation of one or another landscape component in the formation zonal climate (mesoclimate) depends on the type of landscape. In the literature, one can often find expressions: steppe, taiga, desert and other climates, characterized by features due to the zonal features of landscapes.

Within a particular section of the landscape is formed microclimate. It is interpreted as the weather regime of a small area of the landscape - facies, which is characterized by a homogeneous underlying surface. The microclimate, depending on the size of the facies, covers an area from several tens of square meters to several square kilometers.

Man has a huge impact on the macro-, meso- and microclimate. For example: deforestation, the construction of giant enterprises, the burning of fossil fuels, the plowing of vast areas lead to a change in the balance of solar radiation and the chemical composition of the atmosphere.

The following modern changes in landscapes have the greatest impact on the climate: the growth of urban and urban areas, the construction of artificial reservoirs, the creation of anthropogenic agricultural landscapes, and pollution of the oceans. Ocean pollution disrupts heat, moisture and gas exchange between the atmosphere, oceans and continents. Moreover, all these changes often have consequences that are difficult to foresee, since the system of direct and feedback relationships in the atmosphere is so complex.

Change in the Earth's relief

From the very beginning of the discussion of the problem of the formation of the 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 a little rough. And where did the high mountain ranges and the deepest depressions in the oceans come from?

In the 19th century, the dominant idea was the idea that from time to time, for some reason, red-hot magma from the inside attacks the stone shell and then mountains swell and ridges rise in it. Rise? But why, then, are there so many regions on the surface where the ridges run in parallel folds, one next to the other? When heaving, 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 bowels. The folds required horizontal forces.

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

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

Such a process was proposed to explain the formation of the Earth's surface by the French scientist Elie de Beaumont. He called his hypothesis contraction from the word "contraction", which, translated from Latin, just meant - compression. One Swiss geologist tried to calculate what the size of the globe would be if all the folded mountains were smoothed out. It turned out to be a very impressive figure. In this case, the radius of our planet would increase by almost sixty kilometers!

The new hypothesis has gained many supporters. The most famous scientists supported her. They deepened and developed separate sections, turning the assumption of the French geologist into a single science of 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.

The hypothesis of contraction or compression of the Earth and wrinkling of its crust was especially strengthened when large "overthrusts" were discovered in the Alps and Appalachians. Geologists use this term to designate gaps in underlying rocks, when some of them are, as it were, pushed over others. Experts triumphed, the new hypothesis explained everything!

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

deep mountain roots

Around the middle of the 19th century, or rather in 1855, the English scientist D. Pratt conducted geodetic work on the territory of the "pearl of the British crown", that is, in India. He worked near the Himalayas. Every day, waking up in the morning, the Englishman admired the majestic spectacle of the grandiose mountainous region and involuntarily thought: how much can this colossal mountain range weigh? Its mass must certainly have a noticeable force of attraction. How would you know? Stop, but if so, then an impressive mass should deflect a light weight on a thread from the vertical. The vertical is the direction of the Earth's gravity, and the deviation is the direction of the Himalayas' gravity...

Pratt immediately estimated the total mass of the mountain range. It turned out to be a really decent amount. From it, using Newton's law, he calculated the expected deviation. Then, not far from the slopes of the mountains, he hung a weight on a thread and, using astronomical observations, measured its true deviation. Imagine the scientist's disappointment when, when comparing the results, it turned out that the theory differs from practice by more than five times. The calculated angle turned out to be larger than the measured one.

Pratt could not understand what his mistake was. He turned to the hypothesis put forward once by Leonardo da Vinci. The great Italian scientist and engineer suggested that the earth's crust and the molten subcrustal layer - the mantle are almost everywhere in balance. That is, blocks of bark float on a heavy melt, like ice floes on water. And since, in this case, part of the “floes”-blocks are immersed in the melt, in general, the blocks turn out to be lighter than those taken in the calculation. After all, who does not know that the iceberg has only a smaller part that protrudes above the water, and a large part is submerged ...

Pratt's compatriot J. Erie added his own considerations to his reasoning. “The density of rocks is about the same,” he said. - But higher and more powerful mountains stand, plunging deeper into the mantle. Less high mountains sit smaller. It turned out that the mountains seemed to have roots. Moreover, the root part turned out to be composed of less dense rocks, compared with the density of the mantle.

It's a good hypothesis. For a long time, scientists used it when measuring gravity in different parts of the Earth. Until such time as artificial satellites of the Earth flew over the planet - the most reliable pointers and recorders of the field of attraction. But they are still to be discussed.

At the end of the last century, the American geologist Dutton suggested that the highest and most powerful blocks of the earth's crust are eroded by rains and flowing waters more than the low ones, and therefore, they should become lighter and gradually “float”. Meanwhile, the lighter and lower blocks are subjected to precipitation from the tops of their higher neighbors, and they become heavier. And if they get heavy, then they sink. Is this process one of the possible causes earthquakes in the mountains and new mountain building?..

A lot of interesting hypotheses were put forward by scientists at the end of the last century. But perhaps the most fruitful of them was the creation of the doctrine of geosynclines and platforms.

Specialists call geosynclines rather extensive elongated sections of the earth's crust, where earthquakes and volcanic eruptions are especially often observed. The relief in these places is usually such that, as they say, "the devil himself will break his leg" - a fold on a fold.

Back in 1859, the American geologist J. Hall noticed that in mountainous folded areas the sediments are much thicker than in those places where the rocks lie in calm horizontal layers. Why is that? Perhaps, under the weight of the sediments accumulated here, washed away from the neighboring mountains, the earth's crust caved in? ..

I liked the suggestion. And a few years later, Hall's colleague James Dana developed the views of his predecessor. He called the elongated folds of the crust caused by lateral compression (at that time the contraction hypothesis was already dominant) geosynclines. The complex term comes from the combination of three Greek words: "ge" - earth, "sin" - together and "klino" - tilt.

Not all geologists immediately agreed with the opinion of the American specialist. Other pictures of the development of geosynclines have also been proposed. The dispute about them has not subsided to this day for more than a hundred years. Some believe that the heated subcortical substance is divided into heavy and light fractions. Heavy ones “sink”, squeezing lighter ones upwards. They rise, “float” and rip up, tearing apart the lithosphere. Then fragments of heavy plates slide off and crush the sedimentary layers...

Others propose a different mechanism. They believe that slow currents exist in the hot subcrustal substance of the Earth. They tighten, crush sedimentary rocks. And once in the depths, these rocks are melted down under the influence of pressure and high temperatures.

There are other concepts as well. According to one of them, for example, geosynclinal folds arise along the edges of continental platforms, floating like ice floes in the ocean, along the plastic subcrustal substance. Unfortunately, so far none of the existing proposals on this subject fully satisfies the laws observed in nature. And so the dispute, apparently, is far from over.

An outstanding Russian and Soviet geologist, public figure Alexander Petrovich Karpinsky was born in 1846 in the village of Turinskie mines in the Verkhotursky district in the Urals. Today it is the city that bears his name. His father was a forge / and engineer, and therefore it is not surprising that the young man, after graduating from the gymnasium, entered the famous Petersburg Mining Institute.

At thirty-one, Alexander Petrovich became a professor of geology. And nine years later he was elected a member of the Imperial Academy of Sciences.

He explores the structure and minerals of the Urals and compiles consolidated geological maps of the European part of Russia. Starting with petrography, the science of the composition and origin of rocks, Karpinsky deals with literally all sections of the science of the Earth and leaves a noticeable mark everywhere. He studies fossil organisms. He writes outstanding works on tectonics and on the geological past of the earth - on paleogeography.

The doctrine of geosynclines, despite the progressive ideas at its core, experienced many difficulties at the first stage. And at this time, Alexander Petrovich came to grips with the study of "quiet regions" of the earth's surface. Subsequently, they also received the name "platforms". In these works, Karpinsky summarized the huge material on the geology of Russia, accumulated by generations of Russian geologists. He showed how the outlines of the ancient seas that flooded these areas changed at different times. And he deduced two kinds of "wave-like oscillatory movements" of the earth's crust. One, more grandiose, forms oceanic depressions and continental uplifts. The other, not so majestic in scale, provides the appearance of depressions and bulges within the platform itself. So, for example, local fluctuations of the Russian platform, according to Karpinsky, occurred parallel to the Ural ridge in the meridional direction and parallel to the Caucasus - along the parallels.

After the work of Alexander Petrovich Karpinsky, it became clear that the platforms are not at all immovable and unchanging parts of the earth's surface. They develop and change over time. From time to time, mountain areas join the edges of the platforms, which, freezing, increase them. total area. Thus, the development of platforms turned out to be closely connected with the formation of geosynclines and emphasized the development of the entire Earth.

Alexander Petrovich based his conclusions on the principles of the contraction hypothesis, considering it "the happiest scientific achievement." And although the results of further research more and more clearly proved the inconsistency of this hypothesis, the theory of geosynclines and platforms continued to develop independently, becoming one of the most important provisions of geotectonics.

Expansion instead of compression

Perhaps it is precisely the new ideas about the initially cold earth buried the contraction hypothesis. There are new ideas. One of them was that our planet was formed from a denser substance than existing rocks. And the resulting globe was at first almost half the size of the present one. On such a dense cosmic body there were no special depressions and bulges - a continuous, fairly even shell. But gradually, warming up, the original planetary lump began to "swell". Its surface was cracked. Separate blocks of continents began to form, separated by deep depressions of the oceans.

However, the new hypothesis also had many vulnerabilities. And one of them again were folded mountains. After all, folds could only appear during compression.

To cope with such a contradiction, experts came to the conclusion that periods of expansion could be replaced by periods of contraction. Another “pulsation hypothesis” has appeared. It is still supported by a number of scientists today, believing that it is precisely in the alternate reduction and expansion of the earth's radius that the reasons for the movement of the continents may lie. After all, the epochs of folding in the history of our planet also followed each other.

The reasons for such pulsations are not very clear. The Russian scientist academician M. A. Usov connects them with cosmic factors - with the attraction of the Moon and the Sun, with the influence of other planets. Another scientist, Academician V. A. Obruchev, considered one of the possible reasons for the expansion of the Earth to be the transition of magma from a solid to a liquid state. At the same time, a lot of heat escapes from the depths. The Earth is cooling, and consequently, it is strongly compressed.

The pulsation hypothesis has quite a few supporters among modern scientists. They measured rock pressures at various points on our planet and concluded that in this moment The earth is going through a period of contraction. If so, then the number of earthquakes should be increasing...

I gave several examples so that you understand that the issues of the development of our planet are very complex. People have long been trying to penetrate the secret of the geological history of the Earth, but to this day there is no consensus on all issues among scientists.

Critical zones of the planet

Scientists have seen that various zones of the globe, its mountain systems, lowlands are confined to certain belts. Why not evenly over the entire surface?

For example, Alexander Petrovich Karpinsky noted mountain belts running in the meridional direction. And at the same time, Alexander Ivanovich Voeikov, an outstanding geographer and climatologist, as well as Russian geodesist and geographer Aleksey Andreevich Tillo, made very convincing arguments in favor of the latitudinal location of mountain systems.

Why, after all, special zones do not appear everywhere, but only in some critical areas?

Astronomers have long noticed that the course of the Earth's rotation is gradually slowing down. Our planet is slowed down mainly by tidal friction in its crust, arising from the attraction of the Sun and Moon. At the same time, the forces of the polar compression of the planet gradually decrease. This means that at high latitudes the lithosphere and hydrosphere will gradually rise, and at low latitudes near the equator they will sink. With such a process, the boundary strips that experience especially strong stresses, according to scientists, are the seventieth parallel, sixty-second and thirty-fifth, as well as the equator. It is in these belts that zones of tectonic disturbances are located. On land, these are mountainous regions, deep abysses and volcanoes. At sea - the "roaring forties" and other areas of countless dangerous adventures, more than once or twice ending tragically.

And look at the long Cordilleras of North and South America, the Appalachians, the Urals...

Find on the map the West Siberian Plain, which passes into the lowland of the Turgai trough and into the Turan lowland.

Take a look at how the system of rift troughs goes, crossing the eastern part of Africa from north to south...

All of them are oriented along the meridians or close to them. The Soviet scientist G. N. Katterfeld considers the critical zones of the meridional direction of the belt, located between 105 - 75 °, 60 - 120 ° and 150 - 30 °.

These critical zones are very important for Earth researchers to know. They are of great not only theoretical but also practical significance. Because it is in them that the enhanced magmatic activity of the subcrustal substance is observed. And along with magma, ore elements rise along cracks and faults into the upper zones of the crust, which create deposits of various metals. For example, even today geologists are well aware of the Pacific ore belt with large deposits of tin, silver and other metals. This belt encloses the greatest ocean of the earth in a huge ring. The Mediterranean ore belt is also known, containing copper and lead-zinc ores. From the Atlantic coast of Southern Europe and North Africa it stretches through the Caucasus, the Tien Shan to the very Himalayas...

But what is the source of colossal energy, due to which grandiose tectonic processes are carried out in the earth's crust? On this occasion, even in our time, heated discussions do not stop. Some consider tectonics a property generally inherent in the self-development of any planet. They see the internal heat of the Earth as the source of her strength. Others give preference to cosmic factors: the interaction of the Earth with the Sun, with the Moon, change solar activity, even the position of the solar system relative to the center of the Galaxy...

There is no single point of view and no single opinion! Perhaps a few years will pass and a new hypothesis will appear, uniting the causes of planetary development on the basis of new factors already mined not only on the surface of the Earth, but also on other planets.

"Bomb" by Professor Wegener

Have you ever thought about looking at a globe or geographical map world, why are the eastern coast of South America and the western coast of Africa so surprisingly similar?.. Take a closer look. The picture is amazing. The full impression is that once these separate pieces of land were a single huge blotch on the globe, one giant parent land.

Incidentally, this similarity was first noted back in 1620 by Bacon already known to us, as soon as more or less plausible maps with the New and Old Worlds had time to come out. And forty years later, the French abbot F. Place claimed that "before the Flood" both parts of the world were firmly, firmly connected to each other. True, the venerable father did not expand on the reason for their separation. But it is from this moment, if you wish, that you can begin the history of the development of the hypothesis of the movement of the continents, or the hypothesis of "mobilism", as it is called in science.

The real mobilism is associated with the name of Alfred Wegener, who revived the forgotten assumptions of Bacon and Place, putting them on "scientific feet". In general, the idea of the movement of the continents came to Wegener by chance. He looked at the map of the world and, just like you and me, was struck by the similarity of the coasts of the continents.

Who was Professor Wegener? He graduated from the university with a degree in astronomy. But it was, in his words, "too sedentary work" for his temperament. Having learned how to fly a balloon, he, along with his brother, took up atmospheric research and became interested in meteorology. A few years later he went to Greenland to conduct meteorological observations in its harsh climate.

When the founder of climatology, Corresponding Member of the St. Petersburg Academy of Sciences Alexander Ivanovich Voeikov read the book of the young Wegener "Thermodynamics of the Atmosphere", he exclaimed: new star in meteorology!

And suddenly - Wegener and the structure and evolution of the Earth?

Like others of his contemporaries, Wegener imagined the earth as having come from a huge drop of molten matter. It gradually cooled down, covered with a crust, which rested on a heavy and liquid basalt mass.

While heading to Greenland, the scientist more than once drew attention to the mighty ice floes majestically floating on the cold water. Perhaps this image inspired him to imagine the blurring of the continents. But what forces could move them? But you have not forgotten that Wegener was an astronomer by training. And now, in his imagination, a clear picture arises of how the subcrustal layer is carried away by the rotation of the Earth, how the Moon excites giant tidal waves in the mantle that break open the fragile shell, and how pieces of the crust captured by tidal currents move and pile on top of each other, forming a single parent continent, christened by him Pangea .

Pangea existed for many millions of years.

Meanwhile, under the influence of the same external forces in its depths everything was accumulating and accumulating tensions. And at one fine moment, the pro-continent could not stand it. Cracks ran along it, and it began to fall apart. The Americas broke away from Africa and Europe and sailed west. The Atlantic Ocean opened up between them. Greenland broke away from North America, and Hindustan from Africa. Antarctica split with Australia...

One day, almost by accident, at a meeting of the German Geological Society, Wegener without hesitation outlined his hypothesis to the audience. What has begun here!.. The venerable gentlemen, who had just dozed peacefully on their chairs, did not just wake up. They were furious. They shouted that Wegener's views were wrong and that his ideas were absurd and even ridiculous. And he himself is illiterate and... Let us recall that at that time the contraction hypothesis reigned supreme in the geological world. What kind of horizontal movement of the continents is possible with the general compression of the planet? No, the earth's crust can only rise and fall.

It is worth noting that such an approximate coincidence for many years was a strong argument for the opponents of mobilism - the hypothesis of the movement of the continents. Already in our time, when it was decided to reconstruct Pangea not along the coastline of the continents, but along the border of the continental slope, including the continents and shelves, the picture turned out to be completely different. In 1965, scientists used an electronic computer and picked up such a position of the continents, in which the mismatch zones turned out to be negligible. Isn't that proof? But back to Wegener.

Sharp criticism did not discourage the scientist. He only concluded that in order to prove a new idea, he needed to accumulate a lot of facts, a lot.

At that time, the scientist worked at the University of Marburg. He gave lectures to students, processed the materials of his trip to Greenland and thought. All his thoughts were captured by a new idea. He was looking for forces capable of moving the continents from their place, pulling them apart, looking for ways to move the continents.

Ultimately, Alfred Wegener was never able to find enough evidence to support his hypothesis. The forces of attraction of the Moon and the Sun were clearly not enough to move the lumps of the continents. And the idea of a continuous molten subcortical layer turned out to be untenable. The old school won.

The opinion that continents can move was, if not forgotten, then for a long time (in the understanding of our time - in fact, not for long at all) disappeared from the scene. And only in the fifties of the XX century the desecrated hypothesis was powerfully revived, replenished with new facts and took a leading role in modern science about the earth.

Literature

1.#"#">Balandin R.K. Through the eyes of a geologist. - M., 1973

2.#"#">Gangnus A.A. The mystery of earthly catastrophes. - M., 1985

3. Ivanov V.L. Archipelago of two seas. - M., 2003

4. Katz Ya.G., Kozlov V.V., Makarova N.V. Geologists study the planet. - M., 1984

How does the earth's topography change over time? The main forms of the earth's relief. Why does the earth's topography change? Reasons for the transformation of the earth's surface

The action of gravity

Activity of flowing waters

Karst

wind activity

Glacier activity

human activities

Formation of the Earth's relief

Features of the Earth's relief

Voted Thanks!

You may be interested in:

The impact of human activity on the relief

Indirect influence on the relief of a person

VIEW MORE:

Slides and text of this presentation

slide 1

slide 2

slide 3

slide 4

slide 5

slide 6

Slide 7

Slide 8

Slide 9

Slide 10

slide 11

slide 12

slide 13

Anthropogenic landforms

Formation of the Earth's relief

More interesting:

Human impact on relief and geological processes

You might be interested:

Categories

Latest Articles

Advertising