The concept of relief, its classification factors of relief formation. reborn mountains

The mountains

Sushi relief. Mountains and plains

The main landforms of the Earth are mountains and plains. Mountains occupy 40% of the land of the globe, plains 60%.

Mountains (mountainous countries)- these are vast, highly elevated above the surrounding area, strongly and deeply dissected areas of the earth's crust with a folded or folded-block structure. The length of the mountains is hundreds and thousands of kilometers, the height is up to several kilometers, the depth of dismemberment is hundreds of meters. Mountain countries consist of separate mountain ranges and intermountain valleys and basins separating them. mountain range - linearly elongated uplift with slopes inclined in opposite directions. The highest part of the ridge at the intersection of the slopes is called comb. Along it are elevations - peaks and downgrades - saddles. The lowest and widest, relatively accessible saddles are used as passes, roads are laid along them. The tops of the mountains are usually pointed, but may be slightly convex. The external appearance of the slopes - their steepness, general shape, features - depends on the material composition of the rocks, the nature of their occurrence, various slope processes, the degree of snow and forest coverage, etc.

The area where two or more mountain ranges meet is called mountain node. They are tall and hard to reach. Isolated mountains are rare. Most often these are volcanoes, less often domes over the solidified magma that has intruded into sedimentary rocks and lifted them - laccoliths: mountains Beshtau, Mashuk, Zheleznaya and others near the city of Pyatigorsk, Mount Ayu-Dag in the Crimea, etc.

Between the ridges, and sometimes across them, are located at different heights intermountain valleys. They are usually laid either along the axes of concave folds or along tectonic faults. Intermountain valleys are used by glaciers and rivers. Villages are located on the slopes of the mountains.

Highlands - extensive mountain uplifts with a single, massive folded base and with ridges towering above it, wide intermountain depressions - basins.

According to the absolute height, the division of mountains into three groups is accepted: low -

up to 1000 m (Middle Urals, etc.), mid-altitude- 1000-2000-m (Carpathians, etc.) and high - more than 2000 m (Tien Shan, etc.). Low mountains are usually characterized by rounded peaks, gentle slopes, and relatively wide river valleys. High mountains are characterized by pointed peaks, usually covered with snow and glaciers, steep stepped slopes, and narrow valleys. Medium-altitude mountains have transitional external features. However, the specific appearance of mountains depends not only on height, but also on their origin, tectonic structure, composition of rocks, location in the climatic zone, and other factors. The highest mountains are the Himalayas with the peak of Everest (Chomolungma) - 8848 m, the Karakoram with three peaks - eight-thousanders, the Pamir mountain country with the Peak of Communism - 7495 m.

By origin, mountains are divided into tectonic and volcanic; The most common on land are tectonic mountains, the formation of which is associated with folded and discontinuous deformations of the earth's crust during the uplift of the territory. In this regard, they are divided according to the tectonic structure (by structure) into two main types: folded and normal (blocky).

Fold mountains are strata of rocks, crumpled and folds of various sizes and steepness and raised to different heights. The main relief forms - mountain ranges and valleys between them - are determined by the conditions of the occurrence of rocks: the ridges usually correspond to convex folds of varying complexity, and intermountain valleys - concave. Discontinuous violations play a subordinate role. Folded mountains are young. They were formed geologically recently - in the Cenozoic, in the Neogene-Quaternary time, that is, over the past 25 million years, during alpine folding. it primary orogens that arose at the site of geosynclines, at the final (orogenic) stage of their development, with a general uplift of the territory and its transformation into a mountainous country. Therefore they are called post-geosynclinal, otherwise epigeosynclinal(from the Greek epi- "after"). Alpine folding has not yet ended.

All other mountains on land belong to secondary, epiplatform, orogens. They were also formed in the Cenozoic, in the Neogene-Quaternary, due to the latest tectonic movements, mainly within the folded belts of the Paleozoic and Mesozoic age. By this time, the former mountains were either completely or to some extent destroyed by various external processes, and the territories developed in a calm platform mode for a long geological time. In the Neogene, tectonic movements became more active. The rise and fall of blocks of the earth's crust along faults began with a total span of up to 10 km or more. This led to the formation of protrusions - horsts and hollows - grabens. As a result of intensive ascending movements, the leveled territories of considerable area regained the character of a mountainous country.

Most epiplatform mountains on Earth fold-block, arising during repeated mountain building on the site of destroyed mountains in the regions Baikal, Caledonian and Hercynian foldings. These mountains were reborn by raising blocks to different heights and are called reborn. Their ancient folded tectonic structure has been significantly altered by recent fault movements. The revived mountains include a huge belt of Central Asia on uneven-aged - from Precambrian to Hercynian - folded structures: Tien Shan, Altai, Sayans, mountains of the Baikal and Transbaikal regions, Greater Khingan, Karakorum, Altyntag, Nanshan,

Kundun and others. The revived mountainous countries are characterized by depressions - basins: Fergana, Minusinsk, Lake Baikal, etc. It is assumed that repeated mountain building in this belt, as well as the formation of young folded mountains to the south in place of the Alpine-Himalayan belt, proceeded under compression under the pressure of the Arabian and Hindustan blocks moving to the north. The revived fold-block mountains also include the Urals, the middle mountains of Central Europe, the Appalachians, the Great Dividing Range in Australia, etc.

In the areas of Mesozoic folding, the mountains did not have time to completely collapse and had the appearance of low mountains by the beginning of the Alpine orogeny. With the latest movements, they were raised to different heights. They are called rejuvenated. At these mountains, the modern relief often inherits the former Mesozoic folded structure. Such mountains are called blocky-folded. These include the Chersky and Verkhoyansky ridges, the Rocky Mountains, the Mackenzie Mountains, the ridges of the Tibet highlands and the Indochina peninsula, etc.

The category of mountainous countries is often referred to as plateaus, formed on ancient platforms. These are vast areas of the earth's crust, sharply elevated along faults (up to 1000 m or more) above the surrounding plains, with a predominance of flat or slightly undulating surfaces, significantly dissected by deep narrow river valleys, especially in the marginal parts. Plateaus are composed of either crumpled or horizontally lying, erosion-resistant, often volcanic rocks. Plateaus are, as it were, a transitional category of relief between mountains and plains (Central Siberian, Western Australian, etc.).

Exogenous processes occurring in mountains, highlands, plateaus are associated with the activity of rivers, streams, glaciers, etc. Glaciers create trough-shaped valleys in the mountains - trogs, recesses on the slopes of the mountains in the form of rounded chairs - circuses, acute-angled peaks - between cirques on opposite slopes of mountains. The mountains are characterized by mud-stone streams, vigorous landslides, talus, icefalls, snow avalanches, etc.

Plains occupy most of the continents. In tectonic terms, they correspond to stable platforms that did not show significant activity in the Neogene-Quaternary.

Plains are vast areas of the earth's surface with small (up to 200 m) elevation fluctuations and slight slopes.

According to the absolute height of the surface, the plains are divided into low - up to a height of 200 m (Amazon, Caspian, Indo-Gangetic lowlands, etc.) and sublime - from 200 to 500 m (Central Russian, Valdai, Volga Uplands, etc.). Plains also include plateau, which, as a rule, are located at heights of more than 500 m. The depth and degree of their dissection by river valleys, gullies and ravines depends on the height of the plains: the higher the plains, the more intensely they are dissected.

In appearance, plains can be flat, wavy, hilly, stepped, and according to the general slope of the surface - horizontal, inclined, convex, concave.

The different appearance of the plains depends on their origin and structure. Most of the plains are located on the plates of ancient and young platforms and are composed of layers of solid sedimentary rocks of great thickness - hundreds of meters and even several kilometers. Such plains are called reservoir. From the surface, they are often covered with loose Quaternary continental deposits of small thickness, on which their modern appearance depends. The largest areas among them are alluvial, glacial and water-glacial plains.

Alluvial plains are composed of river layered sediments (alluvium), the thickness of which reaches tens and even hundreds of meters. As a rule, alluvial plains are low, with shallow river valleys, with dry riverbeds in deserts. For example, a significant part of the Great Plain of China, the sandy deserts of the Karakum, partly the Sahara, Rionskaya, Kura-Araks, Mesopotamian, La Platskaya, Indo-Gangetic and partly the Amazonian lowlands, etc.

Glacial (moraine) plains composed of unsorted loams with boulders and rubble brought by glaciers several tens - hundreds of thousands of years ago. Their relief is hilly. They occupy vast areas in the north of North America to the Great Lakes, the north of foreign Europe up to the mid-altitude mountains, the north of the European part of Russia and partly of Siberia.

Water-glacial plains located in the lowest areas among the moraine plains or along their southern margins. They are composed of sands left in place of water-glacial flows. In general, they are flat and swampy, in some places the sands are winnowed and form dunes, for example, Polesie, Meshchera, the low left bank of the middle Volga from Nizhny Novgorod to Kazan, etc. They are also characteristic in the foothills of the Alps, Altai, the Caucasus and other mountains, but there usually inclined and composed of coarser sands with gravel and pebbles.

Along the coasts of the seas and oceans, low-lying flat sea ​​plains. These are former sections of the seabed that have become land as a result of recent uplift. They are composed of thick (usually several kilometers) loose marine sedimentary rocks (sands, clays). These include the Caspian, Black Sea lowlands, the northern coast of Eurasia, etc.

Plains that have arisen on the site of mountains as a result of their long-term destruction are called denudation. They are composed of hard crystalline rocks, crumpled into folds. In appearance, these are hilly or undulating plains with residual hill-type elevations in place of harder, stable rocks. These are the Kazakh uplands, the plains of the Canadian and Baltic shields, the plains in southwestern Africa, etc.

Plateau - these are elevated, even, slightly dissected areas, bounded by ledges from the low plains adjacent to them. Plateaus are formed on platform slabs as they rise along faults. They are composed of either sedimentary, usually dense rocks (the Ustyurt Plateau in Central Asia, the Putorana Plateau in Eastern Siberia, the Colorado Plateau, etc.) or volcanic rocks (the Deccan Plateau, large areas on the Central Siberian Plateau, etc.).

Thus, mountains and plains, as the main landforms, are created by internal processes. It is not for nothing that the mountains gravitate in general to the mobile folded belts of the Earth, and the plains to stable platforms. External processes form small short-lived landforms, which are superimposed on large ones and give them a peculiar appearance.

The relief of the bottom of the oceans

There are four zones on the bottom of the World Ocean.

First zone - underwater margin of the continents, consisting of continental shelf - shelf, relatively steep continental slope, turning into a gentle continental foot. This is a flooded part of the continent to a depth of about 3.5-4 km with a continental-type earth's crust. On the shelf, there are relief forms that are typical for the coastal part of the land: flooded river valleys, hills - sheep's foreheads, etc. The sediments are dominated by sediments brought from the land - sand, gravel, pebbles, etc. The shelf is rich in oil, gas, alluvial deposits noble metals, diamonds and other minerals.

The continental slope is often stepped, dissected from top to bottom by numerous faults - submarine canyons. Through them, material from the land enters the foot of the slope and forms huge alluvial fans. The thickness of the cone sediments reaches the maximum thickness of sedimentary rocks for the ocean floor - 15 km.

Second - transition zone formed at the junction of continental blocks and oceanic platforms. It consists of basins of marginal seas, chains mainly volcanic islands in the form of arcs and narrow linear depressions - deep-sea trenches, with which coincide with deep faults that go under the mainland. For example, the Sea of ​​Okhotsk - the Kuril Islands - the Kuril-Kamchatka Trench; Sea of ​​Japan - Japanese Islands - Japanese Trench. There are more than thirty-five trenches in total, the deepest Mariana - 11,022 m, the longest - Aleutian 3570 km. The main active volcanoes of the Earth are concentrated in the transition zone. It is characterized by strong and frequent earthquakes, and the earthquake sources lie deep in the upper mantle. The earth's crust of this zone is complex, close in structure and thickness, sometimes to the oceanic, sometimes to the continental. This zone is not traceable everywhere, it is well expressed along the Pacific coast of Asia, in the Mediterranean Sea, in the Antilles-Caribbean and other regions, which are often called modern living geosynclines.

The third, main zone of the ocean floor - bed of the ocean the earth's crust of the oceanic type, occupies more than half of its area at depths of up to 6 km. On the bed of the ocean there are ridges, plateaus, hills that divide it into basins. Bottom sediments are represented by various silts of organogenic origin and red deep-sea clay, which arose from fine insoluble mineral particles, cosmic dust and volcanic ash. Its color is due to iron oxides. At the bottom there are many ferromanganese nodules with impurities of other metals.

The fourth zone stands out in the central parts of the oceans. it mid-ocean ridges with earth's crust of a special type, consisting mainly of basalts. They have been known in some oceans for a long time. In particular, in the North Atlantic, where the island of Iceland is the outlet of such a ridge to the surface. At the turn of the 50s - 60s, a grandiose system of mid-ocean ridges was discovered, the total length of which is more than 60 thousand km. The height of the ridges above the ocean floor is up to 3000-4000 m, the width is 1000-2000 km. Their feature is a deep valley like a gorge - rift - along the axial parts of the ridges several kilometers wide and 1-1.5 km deep. Under the rift zones, the roof of the asthenosphere lies shallow, in some places only 2-3 km from the bottom surface. In some places, these valleys with ridges framing them continue on the continents, for example: the Red Sea - East African grabens up to 5000 km long, the Gulf of California - the California Valley, faults of the Baikal mountainous country, etc. The mid-ocean ridges are crossed by transverse faults, along which horizontal movements are carried out, so they are divided into segments. All ridges are of volcanic origin. There are many active underwater volcanoes along the rifts, earthquakes with shallow sources are frequent, and an increased heat flow is observed.

Origin of continents and oceans

The relief, geological structure and age of the continents (continental protrusions) and oceans (oceanic depressions) - the largest sections of the earth's crust - are not the same. There are different points of view on these issues.

There is as yet no universal concept that would fit all geological facts.

From the second half of the XIX century. Until the 60s of our century, the hypothesis of the primacy of the oceanic crust dominated among scientists, which in geosynclines turns into the continental crust with the formation of complex folded mountainous countries, on the site of which platforms subsequently arise. From this point of view, the Precambrian platforms, formed as a result of repeated ancient folding (more than 1.5 billion years ago), served as the cores of the continents. Subsequently, the area of ​​the continents increased due to the “fouling” of ancient platforms with folded belts in the Baikal, Caledonian, Hercynian, Mesozoic and Cenozoic (Alpine) eras of folding. This concept still has many supporters.

However, there are geological facts in favor of the reverse process - the expansion of oceanic basins and their absorption of parts of the former continents. In both cases, the decisive role in tectonic deformations is assigned not to horizontal, but to vertical movements, and the position of the continents on the Earth's surface is considered more or less stable, relatively unshakable since ancient times.

In recent decades, the mobilism hypothesis has become widespread, according to which blocks of the earth's crust are mobile, capable of moving in a horizontal direction relative to each other and the poles for thousands of kilometers during geological time. The concept of continental drift was formulated by the German geophysicist A. Wegener in 1912 and later elaborated and set out in detail in the book The Emergence of Continents and Oceans, published in Germany in 1915 and translated into Russian in 1925. Its essence is in the swimming of the lungs granite continents along a denser heated basalt layer.

Starting from the 60s of our century, the history of the formation of the face of the Earth by many scientists, both foreign and Soviet, began to be explained from the standpoint of a new theory - tectonics of lithospheric plates. She retained the main idea of ​​A. Wegener about the horizontal movements of the continents. The emergence of this theory became possible in connection with the study and elucidation of the features of the relief and geological structure of the bottom of the World Ocean.

It was found that the most active, mobile zones of the Earth with modern volcanism and earthquakes are fault systems on a planetary scale - rifts of mid-ocean ridges and deep-sea trenches. Planetary faults are interpreted as zones of splitting of the lithosphere into large blocks, which are called lithospheric plates. They are distinguished by the geodynamic, and not by the structural principle. There are seven main large plates: North American, South American, Eurasian, African, Indo-Australian, Antarctic and Pacific. All of them, with the exception of the Pacific, include continental blocks with adjacent sections of the ocean floor. Therefore, the boundaries of the lithospheric plates do not coincide with the boundaries of the continents and oceanic depressions, which have different types of earth's crust. Plate boundaries drawn along faults - rifts and deep-sea trenches, are called seam zones.

Deep-sea drilling has proved that in rift zones, basalt melt pours out from the asthenosphere and solidifies. This is how a new oceanic basaltic crust is formed. Subsequently, the lithospheric plates move apart in both directions from the mid-ocean ridges. In transitional zones at the junction of plates - in deep-water trenches along inclined faults that go under the mainland, a heavier oceanic plate sinks under a relatively light continental one into the mantle, where it is remelted. Deep-focus earthquakes and volcanic eruptions are frequent in places where plates meet, collapse, and move. Here, in geosynclines, young mountains first appear in the form of a chain of islands (for example, the Kuril Islands), the islands then join the mainland, increasing its area (for example, the Andes).

As a result of the described processes, the earth's crust of the oceans is gradually being renewed. Associated with them is the relatively low thickness of the sedimentary cover of the oceans. Moreover, there is a regular increase in the layer of sediments from the mid-ocean ridges, where they practically wedge out, towards the peripheral parts of the oceans, where at the foot of the continental margins they reach about 15 km of thickness. The age of sedimentary rocks is not older than 160-180 million years, i.e., not older than the Jurassic. In this, the sedimentary cover of the oceans fundamentally differs from the sedimentary layer of the continents, where it was formed over more than 1.5 billion years.

When relatively light continental plates collide, their margins warp and secondary folded-block mountains are formed.

The movement of lithospheric plates is explained by convective currents in the mantle, which rise under the mid-ocean ridges and diverge to the sides, dragging the lithospheric plates, and sink in transition zones. The role of the substrate along which the lithospheric plates move is performed by the asthenosphere due to its plasticity. The speed of movement of lithospheric plates is from 1-2 cm/year in the Atlantic Ocean to 10 cm/year in the Pacific. The removal of North America from Europe was recorded by a special American Earth satellite "LAGEOS". In the Japan Trench, the Nautilus submersible is observing the subduction of the oceanic plate with the Kashima volcano, 3.5 km high, under the island of Honshu. A partial absorption of the volcano was recorded, which, according to calculations, is carried out at a rate of 10 cm/year.

The concept of lithospheric plates, despite the incompleteness of the facts and the insufficient clarity of a number of provisions, convincingly explains the process of the birth of continents and oceans, in particular, the almost mirror coincidence of the opposite coasts of South America and Africa, southern Australia and Antarctica along the foot of the continental slope, the origin of large landforms of the oceans and continents, etc.

At present, many researchers admit that in the second half of the Proterozoic (1.7-0.6 billion years ago) there was a giant single mainland Pangea-1(unlike the later Pangea-11), representing the continental hemisphere of the Earth. In the other hemisphere of the Earth, the existence of the Pacific Ocean is allowed.

At the end of the Precambrian, in connection with the formation of intercontinental geosynclinal belts, Pangea-1 broke up into a northern row of continents (ancient platforms) and a huge southern continent - gondwana(its name comes from a historical region in central India). Gondwana included most of South America (without the Andes), Africa (without the Atlas and Cape Mountains), Australia (without the Great Dividing Range), Arabia, Hindustan, most of Antarctica (without the mountains of the Antarctic Peninsula on the continuation of the Andes). Gondwana lasted until the middle of the Mesozoic. In the Paleozoic, as a result of the Baikal, Caledonian and Hercynian stages of folding in the geosynclinal belts that separated the North American, East European and Siberian platforms, a single northern land mass was formed - Laurasia(from the former name of the Laurentian (now Canadian) shield and Asia). He became the antipode of Gondwana. At the end of the Paleozoic, with the addition of the Chinese platform to Laurasia and the entire Gondwana, a giant supercontinent reappeared - Pangea-11, which lasted until the end of the Triassic. Then the formation of a sublatitudinal geosynclinal belt began - Ocean Tethys between former Laurasia and Gondwana. In connection with the subsequent emergence of the depressions of the Atlantic and Indian Oceans, Laurasia broke up into North America and Eurasia, and Gondwana gave rise to the current southern continents.

It is believed that the opening of the Indian Ocean was accompanied by the displacement of Africa with Arabia, Hindustan and Australia to the north. This led to the end of the Mesozoic - the beginning of the Cenozoic to compression and crowding of the crust in the Tethys Ocean. In its place, in the Cenozoic, the highest ridges of the Alpine-Himalayan mountain belt of Eurasia rose, to which the Hindustan and Arabian blocks of Gondwana joined in the south. The collision of the continental masses of Gondwana and Eurasia was accompanied by repeated orogeny and the formation of a belt of epiplatform mountains in Central Asia from the Tien Shan to the Sea of ​​Okhotsk. The highest mountains of Eurasia - the Caucasus, the Hindu Kush, the Pamirs, the Himalayas - are located opposite the Arabian and Hindustan ledges of Gondwana.

At present, active orogenic movements continue in the Pacific marginal continental geooxyclinal belt, in the Antilles-Caribbean and Indonesian regions. Associated with them are changes in the outlines and an increase in the area of ​​the continents adjacent to them. They are called modern (“living”) geosynclines.

Thus, the basis of each modern continent is formed by the ancient Precambrian platform, with the exception of the largest and most complex continent - Eurasia, which includes several cores - platforms.

The age of the ocean trenches is not the same. The basin of the Pacific Ocean, as noted, is considered the oldest Precambrian (Riphean) structure of the earth's crust. The depressions of the rest of the oceans are relatively young, they formed in the Mesozoic - Cenozoic. However, at the bottom of all oceans, including the Pacific, no rocks older than 160-180 million years have been found. From the point of view of lithospheric plate tectonics, this is explained by the origin of the earth's crust in some places (in the mid-ocean ridges) and its absorption in others (in the trenches) during the circulation of the lithosphere matter.

Questions and tasks

1. What is the lithosphere? How does its power compare with the total size of the Earth?

2. Give a comparative description of the two main types of the earth's crust.

3. What do you know about the geological chronology? What eras and periods is the geological history of the Earth divided into?

4. What are platforms, what is their structure? What are the platforms? What are shields and plates?

5. What are geosynclines? Tell us about the structure and stages of development of geosynclines.

6. How platforms and folded belts are depicted on the tectonic map "The structure of the earth's crust" (see the atlas "Geography of continents and oceans"). Give examples of platforms and folded belts of different ages.

7. What is relief and relief-forming processes?

8. Find the volcanoes listed in the text on the map. What are they - active or extinct? What mountains are they associated with?

9. What landforms are called mountains? How do they differ in height, origin, structure? Give examples.

10. What mountains are called young, revived and rejuvenated, what are the patterns of their placement? Using the map "The structure of the earth's surface", determine the time of formation of the folded foundation of such mountains. Give examples.

11. What are plains? How do they differ in absolute height, origin, appearance? What are the patterns of their placement? Give examples.

12. Tell us about the features of the topography of the bottom of the oceans. How are they explained from the standpoint of lithospheric plate tectonics?

13. What patterns in the distribution of minerals do you know?

Final tasks on the topic "Lithosphere"

1. Draw and label the interior parts of the Earth.

2. Underline the correct statements:

1) the lithosphere is the earth's crust;

2) the earth's crust is part of the lithosphere;

3) lithosphere - part of the earth's crust;

4) the lithosphere and the earth's crust are separated from each other by an intermediate layer.

3. Emphasize the properties that characterize the continental and oceanic crust:

4. Underline the two main features that distinguish the continental crust from the oceanic:

1) power;

2) difference and number of main layers;

3) the absence of a layer of sedimentary rocks;

4) the absence of a basalt layer.

5. Metamorphic rocks include (underline as appropriate):

a piece of chalk; marble; pumice; gneiss; quartzite; peat; rock salt; granite.

6. Where these movements occur. Movements of the earth's crust:

1) horizontal;

2) vertical.

7. In what direction does a seismic wave move from the epicenter of an earthquake?

8. Imagine that there are no more volcanoes on Earth. How will this affect the structure of the Earth's surface, the life of people?

9. Why are the mountains and plains of the globe constantly changing? Explain your answer.

10. Name the external processes that affect the surface of the Earth and the bottom of the oceans. What are their results? What are the differences?

11. Under the influence of what forces and processes does the relief change? Explain your answer.

12. What is the highest mountain in the world? What mountain system does it belong to?

13. What are the highest mountains in Europe? in Asia? in Africa? in North America? In South America? What structure do they have? Name their average height and highest peak.

14. Using a physical map of the world, name the lowest plain in Russia. Give a description of the plan.

15. Using the physical map of the atlas, name the highest plain in Russia. Give a description of the plan.

16. What mountains are called "heavenly mountains"? "roof of the world"? "abode of snow"? Why do you think they are called that?

Recent tectonic movements
and their role in the formation of modern relief

As a result of a long history of geological development on the territory of Russia, the main types of geotectures have formed - flat-platform areas and large orogenic mobile belts. However, within the same geotectures, completely different relief is often distributed (the low basement plains of Karelia and the Aldan Highlands on the shields of ancient platforms; the low Ural Mountains and the high mountain Altai within the Ural-Mongolian belt, etc.); on the contrary, a similar relief can form within different geotectures (the high mountains of the Caucasus and Altai). This is due to the great influence on the modern relief of neotectonic movements that began in the Oligocene (Upper Paleogene) and continue to the present.

After a period of relative tectonic calm at the beginning of the Cenozoic, when low plains prevailed and mountains were practically not preserved (only in the area of ​​Mesozoic folding, in some places, apparently, low hills and low mountains were preserved), vast areas of Western Siberia and the south of the East European Plain were covered with waters. shallow sea basins. In the Oligocene, a new period of tectonic activation began - a neotectonic stage, which led to a radical restructuring of the relief.

Recent tectonic movements and morphostructures. Neotectonics, or latest tectonic movements, V.A. Obruchev defined as movements of the earth's crust that created the modern relief. It is with the latest (Neogene-Quaternary) movements that the formation and distribution of morphostructures across the territory of Russia are associated - large landforms that arose as a result of the interaction of endogenous and exogenous processes with the leading role of the former.

The latest tectonic movements are associated with the interaction of modern lithospheric plates (see Fig. 6), along the margins of which they manifested themselves most actively. The amplitude of Neogene-Quaternary movements in the marginal parts reached

several kilometers (from 4-6 km in Transbaikalia and Kamchatka to 10-12 km in the Caucasus), and in the interior of the plates it was measured in tens, less often hundreds of meters. Sharply differentiated movements prevailed in the marginal parts: uplifts of large amplitude were replaced by equally grandiose subsidences of adjacent areas. In the central parts of the lithospheric plates, movements of the same sign occurred over large areas.

Mountains arose in the immediate contact zone of various lithospheric plates. All the mountains that currently exist on the territory of Russia are the product of the latest tectonic movements, i.e. all of them arose in the Neogene-Quaternary time and, therefore, have one age. But the morphostructures of these mountains are very different depending on the mode of their origin, and it is associated with the position of the mountains within the various tectonic structures.

Where mountains arose on the young oceanic or transitional crust of the marginal parts of the plates with a thick cover of sedimentary rocks crumpled into folds (areas of the Alpine and Pacific folding), formed young fold mountains(Greater Caucasus, Sakhalin Ranges) sometimes with sections volcanic mountains(ridges of Kamchatka). The mountain ranges here are linearly extended along the margin of the plate. In those places where, at the boundaries of the lithospheric plate, there were territories that had already experienced folding movements and turned into plains on a folded base, with a rigid continental crust that could not be compressed into folds (areas of pre-Paleozoic and Paleozoic folding), the formation of mountains proceeded differently. Here, with lateral pressure arising from the approach of lithospheric plates, the rigid foundation was broken by deep faults into separate blocks (blocks), some of which were squeezed upwards during further movement, others - downwards. So mountains are reborn in place of the plains. These mountains are called revived blocky, or fold-block. All the mountains of the south of Siberia and the Urals are revived.

The revived mountains are characterized, as a rule, by the absence of a single general orientation of the ridges, a combination of mountain ranges with nodes from which ridges scatter in all directions (Altai), massifs, highlands (East Tuva, Stanovoye, Aldanskoye, etc.). An obligatory element of the revived mountains is the presence intermountain basins irregular outlines corresponding to the lowered blocks (Tuvinskaya, Minusinskaya, Kuznetskaya, Chuiskaya, Uimonskaya, etc.).

On fig. 7:
Morphostructures of the land, the bottom of the oceans and seas. Land - 1 - plains, plateaus ( a) and revived mountains ( b) ancient platforms ( I- East European (Russian) plain, II- Kola-Karelian country, III- Central Siberian plateau, IV- Baikal mountain country); 2 - plains of young platforms ( V- West Siberian Plain, VI- Ciscaucasia); 3 - revived mountains of the Paleozoic folding area ( VII- Ural, Novaya Zemlya, VIII- Altai-Sayan mountain country); 4 - rejuvenated mountains of the Mesozoic folding area ( IX- mountainous country of the Northeast, X- Amur-Primorsko-Sakhalin country); 5 - young mountains of the Alpine folding region ( XI- Caucasus); 6 - young mountains of the Cenozoic (Pacific) folding area ( XII- Koryak-Kamchatka-Kuril country, XIII- Okhotsk-Primorsky volcanic belt). The bottom of the oceans and seas. continental shelf - 7 - plains of the outskirts of the mainland; 8 - plains on intrashelf basins, transitional zone (continental slopes and island arcs); 9 - inclined plains - ledges; 10 - plains of the bottom of the basins; 11 - fold-block ridges and massifs, 12 - fold-block and volcanic ridges of island arcs, 13 - deep sea trenches. Bed of oceans and seas - 14 - plain of the bottom of deep-sea basins, 15 - mid-ocean ridges 16 - shaft and hills, 17 - fold-block ridges

In the areas of Mesozoic folding, where by the time of the onset of intense movements the mountains could not have been completely destroyed, where areas of low-mountain or low-mountain relief were preserved, the orographic pattern of the mountains could not change or change only partially, but the height increased

mountains Such mountains are called rejuvenated blocky-folded. They reveal the features of both folded and blocky mountains with a predominance of one or the other. The rejuvenated ones include the Sikhote-Alin, the mountains of the North-East and partly the Amur region.

The inner parts of the Eurasian lithospheric plate belong to the areas of weak and very weak uplifts and predominantly weak and moderate subsidence. Only the Caspian lowland and the southern part of the Scythian plate were intensively sinking. Most of the territory of Western Siberia experienced weak subsidence (up to 100 m), and only in the north were subsidence moderate (up to 300 m or more). The southern and western outskirts of Western Siberia and the greater eastern part of the East European Plain were a weakly mobile plain. The greatest amplitudes of uplifts on the East European Plain are characteristic of the Central Russian, Volga and Bugulmino-Belebeevskaya Uplands (100-200 m). On the Central Siberian Plateau, the amplitude of uplifts was greater. The Yenisei part of the plateau is raised by 300-500 m, and the Putorana plateau even by 500-1000 m and higher.

The result of the latest movements was the morphostructure of the platform plains. On the shields, which had a constant tendency to rise, formed basement plains(Karelia, Kola Peninsula), plateaus (Anabar massif) and ridges (Timansky, Yenisei, eastern spurs of Donetsk) - uplands that have an elongated shape and are formed by dislocated rocks of a folded base.

On the slabs, where the basement rocks are covered by a sedimentary cover, accumulative plains, stratal plains and plateaus have formed.

Accumulative plains are confined to areas of subsidence in recent times (see Figs. 6 and 7), as a result of which they have a fairly thick cover of Neogene-Quaternary deposits. The accumulative plains are the middle and northern parts of the West Siberian Plain, the Middle Amur Plain, the Caspian Lowland, and the north of the Pechora Lowland.

Reservoir plains and plateaus - morphostructures of sections of plates that have experienced predominant uplifts. With a monoclinal occurrence of rocks of the sedimentary cover, inclined layered plains predominate, with a subhorizontal - layered-stage plains and plateaus. Layered plains are characteristic of most of the East European Plain, the southern and western outskirts of Western Siberia, and partly of Central Siberia. On the territory of Central Siberia, plateaus are widely represented as sedimentary(structural - Angara-Lena, Leno-Aldan, etc.), and volcanic(Putorana, Central Tunguska, Siverma, etc.).

Volcanic plateaus are also characteristic of mountainous regions (the Eastern Sayan, the Vitim Plateau, the Eastern Range in Kamchatka, etc.). Shield morphostructures can also be found in the mountains, and accumulative and, to a lesser extent, stratified plains (Kuznetsk Basin) can be found in intermountain basins.

Earthquakes and modern volcanism. In close connection with the latest tectonic movements are earthquakes and modern volcanic phenomena. Frequent and strong (up to 9 points or more) earthquakes occur in the Kuriles, in the southeastern part of Kamchatka, in the Baikal region (from the Verkhnecharskaya basin to the Tunkinsky graben), in the eastern and southwestern parts of Tuva and in the southeastern part of Altai. In the region of the Greater Caucasus, near the Lena delta and in the region of the Chersky ridge in the North-East, there are earthquakes with a magnitude of up to 7-8 points.

A comparison of the seismic zoning map ("Atlas of the USSR", p. 96) with a map of lithospheric plates shows that all seismic regions of Russia are part of four seismicity belts coinciding with the boundaries of lithospheric plates. They pass:

• 1) along deep-sea trenches framing the Kuril-Kamchatka arc, where the Pacific plate approaches the Eurasian plate at a rate of 8 cm/year;

• 2) from the Gakkel Ridge in the Arctic Ocean through the Chersky Ridge, where the Chukchi-Alaska block of the North American Plate has broken off from the Eurasian Plate and is moving away at a rate of 1 cm/year;
• 3) in the area of ​​the basin of Lake Baikal, the Amur Plate broke away from the Eurasian Plate, which rotates counterclockwise and moves away at a speed of 1-2 mm/year in the Baikal area. For 30 million years, a deep gap arose here, within which the lake is located;
• 4) in the region of the Caucasus, which falls into the seismic belt stretching along the southwestern margin of the Eurasian plate, where it approaches the African-Arabian plate at a rate of 2–4 cm/year.

Earthquakes testify to the existence of deep tectonic stresses in these areas, which are expressed from time to time in the form of powerful earthquakes and ground vibrations. The last catastrophic earthquake in Russia was the earthquake in the north of Sakhalin in 1995, when the city of Neftegorsk was wiped off the face of the earth.

In the Far East, there are also underwater earthquakes, accompanied by seaquakes and giant destructive tsunami waves.

Platform areas with their flat relief, with weak manifestations of neotectonic movements, do not experience significant earthquakes. Earthquakes are extremely rare here and manifest themselves in the form of weak vibrations. So, the earthquake of 1977 is still remembered by many Muscovites. Then the echo of the Carpathian earthquake reached Moscow. In Moscow, on the 6th-10th floors, chandeliers swayed and bunches of keys rang in the doors. The magnitude of this earthquake was 3-4 points.

Not only earthquakes, but also volcanic activity is evidence of tectonic activity in the area. Currently, volcanic phenomena in Russia are observed only in Kamchatka and the Kuril Islands.

The Kuril Islands are volcanic ranges, highlands and solitary volcanoes. In total, there are 160 volcanoes in the Kuril Islands, of which about 40 are currently active. The highest of them is Alaid volcano (2339) on Atlasov Island. In Kamchatka, volcanism gravitates towards the eastern coast of the peninsula, from Cape Lopatka to 56°N, where the northernmost volcano is located. Shiveluch.

The high (up to 500-1000 m above sea level) volcanic plateaus located here serve as a pedestal for volcanic cones located in groups. In total, there are 28 active volcanoes in Kamchatka and about 130 extinct ones. Volcanoes shaped like regular truncated cones predominate. The highest and most beautiful active volcano in Russia - Key Sopka, the snow-covered peak of which rises to 4688 m.

At the beginning of the Quaternary period, volcanism in Kamchatka manifested itself much more widely and more actively, as evidenced by the spread of extensive lava plateaus here. Young Quaternary volcanoes are known in the Anyui Ridge and the Chersky Ridge (North-East). Active volcanoes in the Quaternary were Elbrus and Kazbek. Fresh traces of volcanic activity are very numerous in Sikhote-Alin, they are found in the Koryak Uplands, in the mountains of the Amur Region, on the Vitim Plateau, in the Eastern Sayan and East Tuva Highlands.

1) Why do most of the rivers in Africa flow into the Atlantic Ocean? 2) In what months of the year does the Zambezi River flood? Why? 3) On which river should you make a put

trip to visit almost all natural areas of Africa? 4) By what signs of African lakes can one judge the origin of their basins? Give examples. 5) What is the peculiarity of the location of natural zones on the continent? (Africa)

Southern continents .............. 1. What continents and on what grounds are united into a group of southern continents? 2. Highlight commonalities in

geographic location of Africa, Australia and South America. Name the differences.

3. List the common features in the climates of Africa, Australia and South America and explain the reasons for their similarity. Which continent has the most diverse climates?

4. Which of the southern continents is the richest in inland waters?

5. On what continents is wide zoning well expressed? What are the altitudinal zones?

6. Which of the countries of the southern continents have a high level of economic development?

7. Why is the nature of Antarctica not similar to the nature of other southern continents?

1. How does latitudinal zonality and altitudinal zonality manifest itself on Earth? What is the lithosphere? Composition and structure of the earth's crust. Minerals.

2. Tell us about the typical weather of an equatorial climate and a tropical climate. How is the relationship between air temperature, humidity, type and amount of precipitation manifested? How does this affect the nature of the mainland?

3. Lithospheric plates and their movement. Name the main provisions of the theory of lithospheric plates and illustrate them with examples.

4. Rivers and lakes of mainland Africa. Features of river valleys and water regime

5. Distribution of air temperature, atmospheric pressure and precipitation at the Earth's surface.

6 Australia GP, relief and minerals, climate, nature. In what ways is the nature of Australia different from the nature of Africa?

7. Antarctica. GP, relief, climate, nature, water. Name at least five signs by which one can say about Antarctica: "Antarctica is the most, the most ...".

8. North America. Inland waters, nature. How is their position in different climatic zones reflected in the nutrition and regime of rivers? Give examples.

9. Air masses. Trade winds. Western winds. Types of air masses.

10. South America. Tell us about the minerals of the mainland. How is the origin of minerals and the structure of the mainland related?

11. Using the example of South America, tell us about the role of the relief, prevailing winds and sea currents in the formation of climatic conditions.

12. Pacific Ocean, Indian Ocean. Atlantic Ocean. Arctic Ocean GP, ​​bottom topography, climate, currents, natural resources.

13. North America. Plain East. Mountain West. Minerals.

14. Main climate-forming factors. Tell us about one of the natural zones of North America. Give examples of the adaptation of plants and animals to the natural conditions of this zone.

15. Eurasia. Relief diversity, its causes (internal and external). Useful minerals.

16. What climatic factors shape the climate of Eurasia? How is the influence of each of them manifested?

17. World Ocean. Properties of the waters of the oceans. surface currents.

18. Africa. Geographical position, relief, climate, natural areas.

19. Geographical shell. Circulation of matter and energy.

20. Natural complexes. Geographic zonation

21. Natural zones of Eurasia. What living organisms have adapted to the natural conditions of Eurasia

22. What continents lie only in the northern hemisphere, in the southern, and in the southern and northern?

Flat mountains or even a plain left in the place of the destroyed mountain system are sometimes subjected to a new influence of mountain-building forces; they create new mountains in the old place, which can be called reborn, but these mountains always differ in their forms and in their structure from those destroyed.

A new period of compression of the earth's crust pushes through the old cracks of ruptures whole blocks left from the former mountains and consisting of folded sedimentary rocks and igneous rocks that have intruded into them. These boulders rise to various heights, and the destructive forces immediately begin their work, cut, dismember the boulders and turn them into a mountainous country. In this case, narrow, raised boulders can take on alpine forms, even crowned with snow and glaciers.

The Ural represents such revived mountains. The chains of the Urals, created in its geosyncline at the end of the Paleozoic era, had long ago been turned into a hilly plain, on which then the young movements of the earth's crust again pushed out long and narrow blocks, already turned by destructive forces into rocky ridges, like Taganai, Denezhkin stone, Kara-tau and others. Altai in Siberia is also a revived mountain system, created by young vertical movements on the site of an almost plain left from the Paleozoic Altai. Some narrow and especially highly raised boulders have been turned by destructive forces into the Katun, North and South Chunek Alps with eternal snows and glaciers.

The revived mountains are also the long chains of the Tien Shan in Central Asia. But in these mountains the boulders into which almost the plain was broken, which remained on the site of the old Tien Shan, underwent some additional folding during the epochs of compression that succeeded the epochs of expansion; this complicated their structure. In addition, there are mountains that are more correctly called not reborn, but rejuvenated. These are the mountains that the destructive forces have not yet managed to turn into almost plains, but have already significantly lowered. The renewed movements of the earth's crust cannot completely restore their original appearance; but the long and narrow boulders, into which these mountains were broken by new movements, were raised higher and again dissected deeper, cut by destructive forces and therefore became more picturesque. An example of such mountains is the Chersky Range in the basin of the Indigirka and Kolyma rivers in northeastern Siberia.

But the revived mountains in the distant future will have the same fate - they will be destroyed again, smoothed out by destructive forces, turned a second time into a plain.

This is how the circulation of substances takes place in inanimate nature, in the kingdom of stones. One replaces the other - one grows, ages and seems to disappear, and another appears in its place. But only forms, outlines change and disappear, and the very substance of which the Earth consists, changing its appearance or moving to another place, remains eternal.

reborn mountains

epiplatform mountains, activated platforms, mountain structures that arose on the site of ancient, peneplanated (leveled and lowered) mountain areas as a result of the latest movements of the earth's crust. Highly elevated sections of peneplains (leveling surfaces) remain in the Vg from the epoch that preceded recent mountain building. Examples of V. in the USSR are the Tien Shan, Altai, in North America - the Rocky Mountains, in Africa - the East African Plateau.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

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