How mountains appeared on earth. How are mountains formed and what are they like? Mechanisms for the formation of mountain ranges

First, let's see what is currently known about the structure and development of mountain systems. Mountains have some peculiarities. The first of these is the staging of development. There are usually three stages.

First - period of subsidence and accumulation of thick sedimentary strata.

Second - stage of formation and formation of mountains.

And finally, the third - the stage of aging and destruction of mountains. Such a sequence of the process of mountain building was noticed even in the period of the formation of the doctrine of geosynclines (late XIX - early XX century).

However, in our opinion, in the doctrine of the development of mountains, a very significant, albeit outwardly hardly noticeable, stage was omitted, which can be conditionally called prageosynclinal, i.e., preceding the appearance of the geosynclinal basin. It was revealed only now, at the stage of widespread use of deep drilling and seismic methods, which made it possible to better understand the structure of mountains and foothills. The presence of this stage is confirmed, for example, by analysis of the geological structure of the northwestern part of the Appalachians and the Swiss Jura. So, on the northwestern margin of the Appalachians, the folds are located directly on the Precambrian basement (left side of the figure). Moreover, the lower layers lie almost horizontally, and if they did not gradually sink to the southeast into the depths of the Appalachian Mountains, then it would be impossible to assume their connection with the Appalachian fold zone. But such a connection exists, and, obviously, weakly disturbed strata underlying the sedimentary rocks characterize some preliminary phase of the formation of the geosyncline. This stage differs from the next one, the actual geosynclinal one, by a calm, gradual subsidence. Thus, the full cycle of mountain development does not consist of three, but of four stages.

The second feature of mountains is the complexity and diversity of structures within a single mountain system.

Structural variegation is often so great that it seems that neighboring areas are not part of a single mountain structure.

Finally, the third feature of mountains is that within their limits the earth's crust is thickened. With an average thickness on the continents of 30-35 km in young folded systems - the Pamirs, the Caucasus, the Alps, the Cordillera, the Hades - it reaches 50-62 km. And since the mountains do not rise above 7-8 km above sea level, the crust within them is, as it were, pressed into the peridotite shell, forming “mountain roots”.

According to the geophysicist I.P. Kosmiiskaya, the thickening of the crust in young mountain ranges occurs due to a more powerful granite layer.

Indeed, in terms of the speed of propagation of seismic waves, this part is quite close to granites. But is it granite?

As already mentioned, the thickness of the sedimentary strata crumpled into folds in mountainous areas reaches twenty or more kilometers, in any case, it is almost always at least fifteen. This is probably just the value that corresponds to the thickness of the granitic part of the crust that is absent here, and sedimentary rocks in the mountainous regions apparently lie directly on the basalts. This is confirmed by geophysical data on typical geosynclinal depressions - the Black Sea and the Caspian.

Do all mountains have roots? No, this belongs only to young fold systems, therefore, at the stage of subsidence and in the era of mountain aging, there are no roots. Consequently, only when the mountains rise upwards, and their bases sink down into the peridotite zone, do the roots of the mountains appear.

These are the facts. They demand an explanation.

Let's look at the aforementioned stages in the development of mountain systems, how these facts are linked with the idea of ​​the expansion of the Earth. The first stage is prageosynclinal. It is characterized by the accumulation, sometimes very significant, of sedimentary strata lying horizontally, and the complete absence of volcanism. Consequently, there is still no direct connection with the deep layers of the Earth. The accumulation of sediments is obviously caused by extension (but not rupture) and deflection of the granite layer of the earth's crust.

The second stage, actually geosynclinal, is the time of prolonged subsidence and accumulation of thick sedimentary strata, accompanied by intense outpourings of lavas and active volcanic activity. The stage under consideration is due to further stretching and rupture of the granite part of the crust, which leads to direct contact of sedimentary rocks with deep crystalline ones. From the basalt strata, now overlain by crushed rocks of the granite layer and relatively loose sedimentary rocks, magma is easily released, literally stuffed with expanded (due to pressure reduction) gases.

The third stage - the stage of formation of folds and mountains - can also be explained by accepting the expansion hypothesis, although it would seem that this is where its Achilles' heel is located. After all, it is usually believed that the folds are the result of lateral pressure or pressure coming from below. And suddenly - the denial of both.

Why, in our opinion, is it impossible to consider lateral pressure as the main factor leading to the formation of folds? Because it cannot be transmitted over a distance equal to many hundreds of kilometers, and will be extinguished already a few kilometers from the pressing object.

In addition, the neighborhood of diverse sites found in some mountainous regions can serve as confirmation that there were probably no single mountain-building movements that formed the entire mountain system at once, and each site arose on its own, individually.

Then, perhaps, the mechanism of "vertically moving pistons" worked here? It is unlikely, since simultaneously with the rise of the tops of the mountains to transcendental heights, their roots penetrated downward, i.e., the movement simultaneously went in opposite directions.

So, we can assume that neither horizontal compression nor vertical uplift could lead to the formation of mountains. Therefore, one thing remains: it is likely that mountains are formed as a result of deconsolidation of crystalline and sedimentary rocks that make up the upper part of the earth's crust.

Is it not surprising that now we have to return to the conclusion made back in 1899 by Datton, who pointed out that one of the causes of mountain building is "... the gradual expansion or decrease in the density of underground magmas."

To the idea of ​​"swelling" as possible cause the formation of mountains, I. V. Kirillov also came. His idea formed the basis of our development.

Under what conditions and how, from our point of view, does the “swelling process” take place? It should go especially vigorously at the base of the mountains, since magmas saturated with expanded gases “act” there. But "swelling" alone is not enough for mountains to appear, since the rocks "swell" first under conditions of stretching of the crust and, therefore, cannot rise up, all the while spreading to the sides. And only at the moments of suspension of tension, when the rocks that have increased in volume no longer have an exit to the sides, they rise up with force and are pressed down into the plastic basalt mass, forming mountains and their roots.

Since the history of the Earth is dominated by extension, and its temporary suspensions are not very long, the epochs of mountain building turn out to be much shorter than the periods of formation of geosynclinal troughs preceding them. No wonder the epochs of mountain building are called revolutionary stages in the development of the Earth, during which its face is dramatically transformed.

Finally, the last stage is the stage of mountain aging. This process is also explained in terms of the expansion hypothesis.

Aging is a slowdown of some active processes, due to which destruction begins to prevail over creation. This is what happens in this case as well. We have seen that the intrusion of magmas saturated with expanded gases is the result of an imbalance, and as soon as it is restored - and this happens at a time when magmas are degassed and sedimentary rocks are granitized - the very process of growth of mountains and their roots dies out and begins destruction occurring under the action of water, weathering and other factors.

The tops of the mountains disappear, and their roots are pulled up. After several stages of folding, the geosynclinal zones turn into young platform areas.

1. Legends about the formation of mountains
The question of how mountains were formed occupied people already in ancient times, but they could not answer it, since they knew too little the composition and structure of the earth's crust. Therefore, they thought that the masses supporting the clouds were created by gods or spirits. People believed that the gods built mountains in order to support the vault of heaven. We have already talked about Mount Olympus, on which, according to legend, the gods of ancient Greece lived. People also thought that mountains were not fixed in one place and that the gods could pick them up and throw them at each other during their battles.
The inhabitants of Kamchatka have the following legend about Mount Shiveluch. This mountain is a volcano; it stands completely apart from other volcanoes of Kamchatka. Local Kamchadal residents believe that once this volcano was located among other volcanoes on the site of the current Kronotsky Lake. But the groundhogs, which were found in abundance in this area, disturbed the volcano so much by digging their holes on its slopes that he finally decided to leave them. The volcano broke away from the ground, leaving behind a large depression, in which water later accumulated and a lake formed. The volcano flew north, but during the flight it caught on the top of a neighboring mountain and broke it off, and descending to the ground, squeezed out depressions for two more lakes before choosing a place for itself 220 kilometers from the old one. In this new place, the volcano strengthened forever.
Many peoples have similar legends about the formation of mountains. They certainly have nothing to do with the actual formation of mountains.

2. Mountains - wrinkles of the cooling Earth
Many people compare mountains on Earth to the wrinkles that form on the skin of a drying apple or potato. It is sometimes said that the mountains on Earth arose in exactly the same way as these wrinkles.
This is not entirely true. The earth does not shrink, but decreases in its volume, because it is constantly cooling, cooling down. This cooling began even when the substance that makes up the Earth began to condense into a ball of hot gases, and then into a fiery-liquid ball; it continued, albeit more slowly, after the formation of the solid earth's crust, and is also happening at the present time. Volcanoes, ejecting hot gases and fiery liquid lava, as well as forming numerous hot springs, constantly bring a lot of heat from the earth's interior to the surface, and this heat is lost to the Earth irretrievably; the heat that the sun's rays give the Earth penetrates only a few meters deep into the earth's crust. Thus, the Earth loses more heat than it receives, and therefore slowly cools.
Volcanic eruptions, hot springs, as well as observations in boreholes and deep mines ah show that with the deepening into the earth's crust, the temperature of the rocks increases markedly. This proves that a lot of heat has been preserved in the bowels of the Earth, and this heat continues to be consumed. But, as is known, any body during cooling decreases in its volume; the earth's core (the inner part of the globe) is also decreasing. Therefore, the earth's crust, adapting to the shrinking core, must wrinkle, its layers form folds-wrinkles, which represent mountain ranges. If we recall that the diameter of the globe is approximately 13 thousand kilometers, and the highest mountains reach only 7-8 kilometers, then they are completely insignificant wrinkles compared to the Earth, much smaller than the wrinkles of the peel of a dried apple compared to its size. .
This explanation for the formation of mountains is still very common among scientists; it is, in general, correct, but not sufficient. The formation of mountains is more complex than has just been described. It will become clear to us if we get to know more closely the structure of these "wrinkles" or, as scientists call them, the folds of the earth's crust.

3. What do mountain folds tell?
Folds can be very well seen and studied on the slopes of mountains and hills, in gorges, in steep cliffs of the banks of rivers, lakes and seas - in general, almost everywhere where layers of sedimentary rocks protrude. It is precisely such rocks, consisting of separate regular layers lying on top of each other like the leaves of a book, that well show the folded formation of mountains. The layers were originally formed in the water at the bottom of some reservoir and, during their formation, lay flat - horizontally or with a very gentle slope in one direction or another. But in the mountains we see that these layers are inclined steeply or stand even vertically - "set on their heads." It means that some terrible force lifted them, moved them from their place.
Let's follow the same rock layer in a fold (Fig. 10). We will see that it rises, gradually bends, forming an arch, then falls down, then rises again. And all the other layers lying under it and above it repeat the same movement. Sometimes such a fold is completely isolated, lonely, but usually one fold is followed by others. The forms of the folds are different - either flat (Fig. 11, a), then steep (Fig. 11, b), then with smooth bends, then with fractures at an angle (Fig. 11, c). There are folds in which the inflection is turned neither up nor down, but sideways; such folds are called recumbent (Fig. 11, d). Sometimes very complex folding is obtained, which can also often be seen in the mountains (Fig. 11, e); it shows that in this place the earth's crust was compressed, wrinkled very strongly, and the folds were bent, forming mountains.

Various forms of folds:
a - flat; b - cool; c - with a sharp fracture; g - recumbent; d - complex

The reader, who has never been in the mountains and who has not seen these folds with his own eyes, will say with disbelief: this cannot be! Layers of such hard rocks as sandstones, limestones, shales are not paper, not cloth, not leather, which can be bent in any way. Scientists used to think so too, and therefore believed that the folds were formed at a time when the rocks were still soft and consisted of sand, clay, and silt. But the study of the mountains showed that the rocks did bend in a solid state. This can be seen from the fact that the layers suffered greatly during bending - they are torn apart by small cracks, in some places even crushed, and parts of the torn layers are often moved away from each other (Fig. 12). Such broken folds can be seen in the mountains; shifts sometimes reach a huge value.

The bends of solid rocks are explained as follows. The layers now raised high in the mountains formerly lay at a shallow depth and were under the pressure of all the layers lying above. And under strong pressure, even solid bodies can change their shape. So, for example, lead under strong pressure can pass through a narrow hole in a jet, like water, and thick sheets of iron, steel, copper bend like a sheet of paper. Glass and ice are very fragile bodies, but they can also be bent without breaking if you press on them very slowly and gradually. In the depths of the earth's crust, rocks could bend very strongly, tearing only slightly; of course, these bends happened very slowly. But when the pressure force was already too great, the fold was torn in one place or another, and its parts moved towards each other, as we saw in Fig. 12.

4. Faults of the earth's crust
The ruptures of rock layers occurred not only from the pressure of the upper layers on the lower ones. In addition to these pressure forces, which crushed layered rocks and folds, other forces acted, lifting molten masses from the depths of the earth from the bottom up to the surface of the Earth. They tore the earth's crust with large cracks, along which one side rose up or the other fell down. Such breaks and movements of the earth's crust are called faults (Fig. 13); they can often be seen both in the mountains and in the mines, both near folds, and in such areas where there are no folds. The faults are well known to both the miner and the miner from bitter experience. Encountering a crack along which a displacement has occurred, he sees that a layer of coal or a vein with ore behind the crack suddenly disappears, as if cut off, and the face rests on empty rock. The disappeared continuation of the layer or vein has to be looked for at the top, bottom or side.

When dumping, sometimes entire sections, huge blocks of the earth's crust move; they also form mountains, but these mountains are of a different kind than those produced by the formation of folds.
The ruptures of the earth's crust with deep cracks created convenient ways for the molten masses located at a depth to climb up; along the cracks of the gaps, an easier road was prepared for them. Molten masses used this road and penetrated the surface of the Earth, creating volcanoes, or stopped at some depth, where they solidified, forming massifs of deep rocks. That is why along the large cracks that cut through the earth's crust, we especially often see extinct and active volcanoes. Such areas, where the earth's crust is strongly cut by cracks and where there are many volcanoes, we see along the coasts of the Pacific Ocean - there, from New Zealand to Kamchatka and from Alaska to Tierra del Fuego, fire-breathing mountains stretch in a long chain.

5. What forces formed the mountains?
Now we know how the mountains were formed, how they rose up. It remains to answer the question - what forces created these irregularities on the surface of the continents?
There are several scientific assumptions (or, as scientists call them, hypotheses) about the reasons for the formation of mountains. We will not consider all these hypotheses here - this would require a lot of time. We will confine ourselves to presenting one hypothesis proposed by the Soviet scientist Usov and the American geologist Becher. This hypothesis is called "pulsating" from the word "pulsate", that is, to act in jolts. It consists of the following.
It is well known that all bodies expand when heated and contract when cooled. This also applies to the particles of substances that make up the Earth.
As the globe cools all the time, its particles are compressed, attracted to each other. This compression causes the particles to move faster; scientists have established that such an increase in movement leads to an increase in temperature, to heating of bodies. And this heating causes the expansion of bodies and the repulsion of particles from each other. Thus, in the depths of the Earth, from the beginning of its formation to the present, there has been a struggle between the forces of attraction and repulsion of particles. As a result of this struggle, the solid earth's crust oscillates, and all those irregularities that we spoke about are created on its surface. According to the Usov-Becher theory, compression and expansion do not occur simultaneously, but alternately, in the form of shocks - the earth's interior "pulsates". A sharp contraction is usually followed by a more or less sharp expansion. Folding of rocks is caused by compression, and fractures and penetration of molten masses into them are a consequence of expansion.
In the earth's crust, periods (times) of compression are expressed in different ways in its different parts: in geosynclines, where thick strata of sedimentary rocks have accumulated, compression creates strong and complex folding.
On stable platforms, individual blocks protrude along fault cracks, as well as weaker folding of less thick sedimentary rocks formed on land in lakes and shallow inland and coastal seas, and gentle upward bending of individual more or less large areas.
Periods of stretching of the earth's crust during the expansion of the Earth's core also cause various consequences: platforms are cut by new cracks of ruptures, old cracks expand, and volcanic rocks pour out onto the surface through both; individual blocks and squares rise. In geosynclines, strata of sedimentary rocks, strongly compressed during the period of compression, bulge upward and form mountain ranges, and molten masses penetrate these strata from the depths through cracks and form massifs and veins of deep rocks, partly also reaching the surface and creating volcanoes.
Near the old geosynclines, advanced in the form of mountain systems, on the outskirts of the platforms, trough-shaped depressions often form in the stretched crust, which then often turn into new geosynclines.
The study of the structure of mountains in different countries has shown that periods of strong compression and the formation of folds occur almost simultaneously on the Earth almost simultaneously and consist of several separate shocks separated from each other by periods of comparative rest. A lot of time elapses from one push to the next.
But even in these intervals between shocks, the earth's crust does not remain completely at rest, since compression shocks are replaced by expansion shocks, and each shock begins and ends with weaker movements of the earth's crust, indicating an ongoing struggle between the forces of attraction and repulsion in the bowels of the Earth.
The last strong movements on Earth occurred, as scientists have established, more than a million years ago.
At present, the Earth is experiencing a quieter period, but accurate observations have shown that weak movements of the earth's crust are still ongoing. By measuring the level of the oceans, scientists have found that in some places the shores are rising, in others they are lowering.
On the slopes of river valleys, so-called terraces are formed, that is, steps that are caused by the elevation of the terrain. Strong earthquakes occurring in different countries from time to time are undoubtedly caused by a sudden displacement of strata in the depths of the crust, and at times repeated eruptions of the same volcano prove that weak movements of the earth's crust are still taking place.
On the site of internal and coastal geosynclines, mountains arise, which join the continents and increase their size; this is repeated in every period of expansion, so that during such past periods the continents gradually grew larger.
On the other hand, large areas of the earth's crust may sink below ocean level and be flooded by the sea; near the mountain range that has risen from the geosyncline, a new depression is formed, which can also be flooded with water. The sea advances on land and its retreat occurs when the earth's crust rises and geosynclines turn into mountain structures. So there is a constant struggle between land and water.
Studies have shown that, in general, the area of ​​the continents has increased significantly against the original.

Mountains are the most picturesque regions of the world. Majestic and beautiful are the peaks of the Tien Shan, the Caucasus, the Alps sparkling with eternal snows, the impregnable snow-white masses of the Himalayas; the harsh ridges of the Urals are also beautiful, crowned with intricately weathered rocks rising like watchtowers above the chaos of boulders; green slopes and valleys of the Carpathians with fast-flowing rivers are good.

Mountains attract people not only for their beauty. In their depths are hidden ore riches, with the extraction and use of which the cultural development of mankind is connected. Fast mountain - a powerful source of energy. Clean mountain air and a variety of which young mountains are especially rich in restore the strength and health of sick and tired people.

You can get to know the structure of mountains quite well without laying boreholes and without digging deep mines: the structure of mountains is revealed in gorges and on exposed slopes in river valleys.

Let's make a mental journey through the valleys of the rivers of the Northern Urals and get acquainted with the structure of this ridge. To cross the Northern Urals, one must take a boat up one of the tributaries of the Pechora escaping from it, cross the mountain watershed on foot and go down on a raft along one of the rivers of the eastern slope belonging to the basin of the river. Obi. Along the banks of the Ural rivers, picturesque rocks and exposed cliffs, or outcrops, protrude. You will see that they are composed of sedimentary rocks: limestones, sandstones, conglomerates, clay and siliceous shales. In these rocks there are imprints and fossilized remains of extinct organisms; they are especially numerous in limestones.

Limestone deposits indicate that millions of years ago there was an open, shallow warm area, at the bottom of which there were marine animals that had calcareous skeletons.

Sandstones with the remains of marine organisms and plant imprints that are visible here were deposited in the area of ​​the sea coast or sea islands, and sandstones and clays with the remains of plants and freshwater - river or lake sediments. In the coastal outcrops of the rivers of the western slope of the Urals, layers of marine sediments protrude mainly.

The remains of organisms found in rocks make it possible not only to determine the conditions under which these rocks were formed, but also make it possible to find out which of the layers were deposited earlier and which later.

Geologists divide the history of the Earth into five major periods of time, or eras: the Archeozoic (the era of ancient life), the Proterozoic (the era of primary life), the Paleozoic (the era of ancient life), the Mesozoic (the era of middle life) and the Cenozoic (the era of new life). The duration of eras is measured in hundreds of millions of years. They, in turn, are divided into periods, the duration of which is measured in tens of millions of years.

The study of the fossil remains of animals and plants found in the strata that make up the Ural Range shows that they were deposited during the Paleozoic era of the Earth's history. As you move east, layers of more and more ancient sediments of the Paleozoic era will appear in the coastal rocks of the Ural rivers.

Along the westernmost outskirts of the Urals stretches from north to south a strip of sediments formed in the last, Permian period of this era. The rocks deposited at the beginning of the Permian period consist of sandstones, conglomerates and shales with marine fauna, and the sediments of the second half of the Permian period were formed not in the sea, but in rivers and lakes; they contain the remains of plants, freshwater mollusks and fish, and in one outcrop on the shore of the Upper Pechora, bones of large extinct reptiles were found.

In the Polar Urals, in the basin of the tributary of the Pechora river. Mustache, among the Permian deposits are numerous seams of coal. Here in 1926 prof. A. A. Chernov discovered the richest coal-bearing Pechora basin. Within the Upper Pechora, the Permian deposits do not contain coal at all. But deposits of rock salt and valuable potash salts have been discovered here.

The thickness of the Permian deposits on the western slope of the Northern Urals is very high; it reaches several kilometers.

Further east of the band of Permian rocks in the foothills of the western slope of the Urals, a band of deposits of the Carboniferous period that preceded the Permian extends. It is mainly with the remains of marine animals. In these regions of the Urals, the places are especially picturesque. Looking closely at the water-smoothed surface of limestone, one can, as it were, look at the bottom of the carboniferous, where various shells, large colonies of corals or whole layers of rocks, consisting of segments of stems of sea lilies and needles, are visible. sea ​​urchins. Looking through a magnifying glass, you can be sure that it often consists entirely of the smallest shells of rhizomes - foraminifers.

Among the deposits formed at the beginning of the Carboniferous period, in addition to limestones, there are layers of sandstones with plant remains, and in some places with layers of coal. This means that at that time there was a shallowing of the sea and in some places land appeared, covered with rich vegetation, which provided material for the formation of coal.

Behind the band of carboniferous limestones, an area of ​​more ancient deposits appears - the Devonian, and then the Silurian periods. They also consist partly of limestones, partly of sandstones. Among them are siliceous and - monuments of the deeper regions of the sea.

Examining the rocks of the Paleozoic rocks protruding along the banks of the rivers, one can notice that the layers do not lie horizontally. Limestone strata in coastal cliffs are usually inclined, or "fall", in one direction or another at a smaller or larger angle to the horizon. Sometimes the layers are vertical. These. inclined and vertical layers are parts of large, dilapidated folds. The sizes of the folds are very diverse: from the smallest, measured in centimeters, to the huge ones, having tens of kilometers in length, hundreds and thousands of meters in width. Such large folds can form high mountain ranges.

The most ancient and most altered sediments form the main Ural Range. Looking at the exposed rocks and scree on the peaks Ural mountains, you can see crystalline schists formed as a result of changes in sedimentary rocks, mica schists, less often marbles. It is often possible to observe how these rocks are interbedded with green shales of a different origin, formed due to the metamorphism of basaltic lavas.

It is assumed that the ancient crystalline schists of the Urals belong to the deposits of the Cambrian period and even part of the Proterozoic era.

A number of peaks of the Ural Mountains consist of deep igneous rocks: granites, gabbro, etc.

In the area of ​​ancient shales of the mountain strip, especially where granites and gabbro are common, there are various ore deposits for which the Urals are so famous. There are lead and zinc ores, and a number of other metals.

On the eastern slope of the Urals, the area of ​​Paleozoic deposits is again opened. They will differ from the sediments of the western slope corresponding to them in age by abundance.

At the very outskirts of the eastern foothills of the Urals, on their border with the vast West Siberian lowland, younger deposits emerge, formed during the Mesozoic and Cenozoic eras. These marine and continental sediments are covered with Ice Age Quaternary rocks. Unlike Paleozoic deposits, they lie horizontally.

What can be said about the origin of the Ural Range based on what we had to see while crossing it?

In what direction did the forces that caused the folding act? Oblique, overturned and recumbent folds in the mountains directly indicate in which direction the forces that crushed the layers acted. Such folds undoubtedly formed under the influence of lateral, horizontal pressure. This pressure was most often one-sided, since in each mountainous region the folds usually overturn and lie down in one predominant direction. On the western slope of the Urals, the folds are tilted and overturned to the west under the influence of pressure that came from the east. A straight crease can result from pressure both from the bottom up and from the sides, in a horizontal direction. This is easy to verify with a simple experiment. If you put a stack of sheets of paper on the table, bring a stick under it and lift it, then the paper will bend; and forms a straight line anticlinal fold. The same fold can be obtained by carefully squeezing sheets of paper lying on the table from both sides with your hands. As can be seen, the folds are formed as a result of the disruption of the original bedding. Such disturbances in the occurrence of earth layers are called dislocations.

As can be seen, the Ural Range is composed of a thick layer of sedimentary rocks of Paleozoic age and almost exclusively of marine origin. Among the latter, there are many erupted volcanic rocks in the mountain belt and on the eastern slope. This indicates that in the place of the Urals in the Paleozoic there was a sea, at the bottom of which underwater eruptions and powerful outpourings of lavas occurred.

The thickness of the Paleozoic deposits in the Urals is great; it reaches 10-12 km. How could a layer of sediments of such enormous thickness be formed? This can only be explained by the fact that in the region of the sea basin, which was located on the site of the present Urals, as precipitation accumulated, the seabed was lowered.

At the end of the Paleozoic era, layers deposited over many millions of years were folded into folds and mighty mountain ranges rose from the bottom of the Ural Sea. Particularly significant uplifts occurred in the area of ​​the current mountain strip.

The folds that can be found in many outcrops of the Urals have a rather complex structure. Geologists have long been interested in the conditions under which they form. For the occurrence of bends in thick layers of sandstones and limestones, the rocks had to be in a particularly pliable, plastic state. On the surface of the earth, these rocks, under the conditions familiar to us, are rigid: they are not capable of giving smooth bends and must split under the pressure of the internal forces of the Earth. The plasticity of the rock is acquired in the depths of the earth's crust, so geologists have concluded that the folds, forming mountains, arise in the deep bowels of the Earth.

The formation of the Ural Mountains was accompanied by the introduction of molten, which formed slowly cooling underground foci -. From these cooling hearths, incandescent vapors and hot solutions rose and penetrated into the cracks of the surrounding rocks. The formation of those deposits of ores and precious stones for which the Urals are famous is associated with them. The destruction of the Ural Range, which has been going on for many millions of years, has revealed batholiths frozen in the depths, which now protrude to the surface.

Getting acquainted with the history of the formation of the Urals, south to make sure that in its place during the Paleozoic era there was a region of long-term subsidence, flooded. At the bottom of this sea, there was an accumulation of thick layers of sediments that could be folded into folds. Such areas are called geosynclines. At the end of the Paleozoic (in the Permian period) and at the beginning of the Mesozoic (in the Triassic), major mountain-building processes took place in the Ural geosyncline and high mountain ranges arose.

The emergence of mountains on the site of geosynclines is the basic law of mountain building, which is confirmed by the study of any mountainous country.

After the formation of folds, the intrusion of molten magma and the uplift of mountains, the geosyncline changes its properties. It turns into a more stable, rigid area of ​​the earth's crust, where folds can no longer appear, and under the pressure of mountain-building forces, the rocks split, cracks appear, along which the layers move. This is how faults, grabens and horsts are formed. Areas of the Earth that are not capable of crushing are called platforms. On them, slow uplifts of vast spaces are observed, followed by slow lowerings. These fluctuations are associated with the advances and retreats of the sea.

Splits on the platforms, leading to the formation of normal faults, occur under the influence of pressure coming from geosynclines. In some cases, the movement along the faults reaches a large scale: horsts appear, raised to a height of up to 3-4 km. Fault faults still take place in many mountains on Earth. In the mountains of Central Asia, for example, there are often associated with rupture of earth layers and the formation of faults.

Horst uplifts lead to the fact that mountain ranges are formed in place of the platforms. These mountains are called blocky(resurrected), as opposed to folded(Urals, Caucasus, Alps), where fold processes play the main role.

Anyone who has not yet been in the mountains, I think it is necessary to go there at least once. Only by climbing to a height, even if not very high, you can enjoy a real sense of freedom. The world looks very different from the top of the mountain. How did nature create all this beauty? I will tell you a little about how mountains are formed, which so attract with their beauty and grandeur.

How mountains are formed

Depending on how the mountains were educated, they can be divided into 3 types:

• tectonic;
• volcanic;
• erosive.

tectonic mountains formed by collision of lithospheric plates. During this process, so-called folds appear on the surface of the earth. Such formations are called folded mountains. Over time, under the influence of the forces of nature, cracks and faults form in such mountains. If there is a repeated shift, then the folds of the mountains can fall or rise. Such mountains are already called fold-block.

It's easy to guess that volcanic mountains became a consequence volcanic eruptions. There are areas on our planet where a whole chain has formed from volcanoes. This indicates high volcanic activity.

Erosive type of mountains formed due to active destruction of stratal plains and plateaus with fast streams of water. In these mountains one often finds canyons. As a rule, eroded mountains are an integral part of mountain ranges.

Appearance Mountains depend not only on how they were formed, but also on the age, type of rock, as well as on various kinds of influences of the planet itself.

Mountain height

Many do not consider hills less than 2000 m to be mountains, but in fact mountains can be up to 800 m. They are called low mountains. Mountains of medium height are those that rise 800–3000 meters above sea level. It turns out that the top of Rosa Peak with a height of 2320 m refers specifically to middle mountains.

Mountains are considered higher 3000 meters. As a rule, their age is young, and the relief is actively changing. It is believed that the mountains do not like the weak and cowards. People who have made more than one trip to the mountain peaks together become best friends.

Mountains occupy 24% of the land surface. They also exist at the bottom of the oceans. 10% of the representatives of the human race, who live in the mountains, are slightly puzzled by the reasons for the appearance of such "giants". Moreover, when the next earthquake occurs. Naturally, if the mountains are young, prone to tectonism, volcanism and seismism.

How mountains are formed - all versions

Each people living in the mountains created their own legend about mountain building. The popular version is giant people, frozen or punished for their deeds by higher powers. From time to time they come to life, showing their bad temper

Fortunately, today we have a complete list of reasons for the formation of mountains, so the fear of this form of relief can be left only to those who violate safety precautions during trekking, mountain hiking, climbing. Let's explore together the question of how mountains are actually "born". Consider that the genesis of the mountain system has become a key classifier of this landform.

Types of mountain building

Fold mountains

The first option - folded mountains, became the result of the work of the internal forces of the Earth. The discussed relief form is obtained in the case of convergence (collision) of two lithospheric plates. The most striking example is the "cutting" of the Indo-Australian plate into the Eurasian one, as a result of which the earth's crust was crumpled into folds, forming the Himalayas.

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Interesting facts about mountains

As a bonus, we can recall the Alps, resulting from the interaction of the African-Arabian platform with the same Eurasian one.

Or the Cordillera, resulting from the "collision" of the North American platform on a plate lying under the water masses of the Pacific Ocean. The "design" of folded mountains is several rows of mountain ranges running parallel to one another. With a developed fantasy or during an airplane flight, you can “see” how the earth's crust was crumpled into folds, forming modern mountain systems.

Blocky-folded mountains

Another option for the formation of mountains is two-phase tectonism. In the first phase, we get typical folded mountains. The process is familiar - described above. But! The mountain range can be long. And the earth's crust is everywhere divided into blocks. Which can move up and down, regardless of the overall movement of the platform. Therefore, in the second phase of this type of mountain building, a long, long mountain range is broken into fragments. One begins to slowly move up, the other - down, the third - also down, but at a different speed.

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