Block mountains 1 3 examples. Mountains are like barriers. The importance of relief in human economic activity

What types of mountains are there?

There were times when mountains were considered a mysterious and dangerous place. However, many of the mysteries associated with the appearance of mountains have been unraveled in the last two decades thanks to the revolutionary theory of lithospheric plate tectonics. Mountains are elevated areas of the earth's surface that rise steeply above the surrounding area.

Peaks in the mountains, unlike plateaus, occupy a small area. Mountains can be classified according to different criteria:

Geographical location and age, taking into account their morphology;

Features of the structure, taking into account the geological structure.

In the first case, mountains are divided into mountain systems, cordilleras, single mountains, groups, chains, and ridges.

The name Cordillera comes from a Spanish word that means "chain". Cordilleras include groups of mountains, ranges and mountain systems of different ages. In western North America, the Cordillera region includes the Coast Ranges, Sierra Nevada, Cascade Mountains, Rocky Mountains, and many small ranges between the Sierra Nevada of Nevada and Utah and the Rocky Mountains.

The cordilleras of Central Asia (you can read more about this part of the world in this article) include, for example, the Tien Shan, Kanlun and the Himalayas. Mountain systems consist of groups of mountains and ranges that are similar in origin and age (the Appalachians, for example). The ridges consist of mountains that stretch in a long, narrow strip. Single mountains, usually of volcanic origin, are found in many areas of the globe.

The second classification of mountains is compiled taking into account endogenous processes of relief formation.

VOLCANIC MOUNTAINS.

Volcanic cones are common in almost all areas of the globe. They are formed by accumulations of rock fragments and lava erupted through vents by forces that operate deep within the Earth.Illustrative examples of volcanic cones are Shasta in California, Fuji in Japan, Mayon in the Philippines, and Popocatepetl in Mexico.Ash cones have a similar structure, but they consist mainly of volcanic scoria, and they are not so high. Such cones exist in northeastern New Mexico and near Lassen Peak.Shield volcanoes form during repeated lava eruptions. They are somewhat not as tall and they do not have such a symmetrical structure as volcanic cones.

There are many shield volcanoes in the Aleutian and Hawaiian Islands. Chains of volcanoes occur in long narrow strips. Where the plates that lie along the ridges stretching along the ocean floor diverge, magma, trying to fill the crevice, rises upward, eventually forming new crystalline rock.Sometimes magma accumulates on the seabed - thus, underwater volcanoes appear, and their peaks rise above the surface of the water like islands.

If two plates collide, one of them lifts the second, and the latter, being pulled deep into the oceanic basin, melts into magma, part of which is pushed to the surface, creating chains of islands of volcanic origin: for example, Indonesia, Japan, and the Philippines arose this way.

The most popular chain of such islands is the Hawaiian Islands, 1600 km long. These islands were formed by the northwestward movement of the Pacific plate over a crustal hot spot. A crustal hot spot is a place where a hot mantle flow rises to the surface and melts the oceanic crust moving above it. If you count from the surface of the ocean, where the depth is about 5500 m, then some of the peaks of the Hawaiian Islands will be among the highest mountains in the world.

FOLDED MOUNTAINS.

Most experts today believe that the cause of folding is the pressure that occurs during the drift of tectonic plates. The plates on which the continents rest move only a few centimeters a year, but their convergence causes the rocks on the edges of these plates and the layers of sediment on the ocean floor that separate the continents to gradually rise up in the ridges of mountain ranges.Heat and pressure are formed during the movement of plates, and under their influence some layers of rock are deformed, lose strength and, like plastic, bend into giant folds, while others, stronger or not so heated, break and are often torn off from their base.

During the mountain building stage, heat also causes magma to appear near the layer that underlies the continental portions of the earth's crust. Huge areas of magma rise and solidify to form the granite core of the folded mountains.Evidence of past collisions of continents is the old folded mountains that stopped growing long ago, but have not yet collapsed.For example, in the east of Greenland, in the northeast of North America, in Sweden, in Norway, in the west of Scotland and Ireland, they appeared at a time when Europe and North America (for more information about this continent, see this article) converged and became one huge continent.

This huge mountain chain, due to the formation of the Atlantic Ocean, was torn apart later, about 100 million years ago. At first, many large mountain systems were folded, but during further development their structure became significantly more complex.Zones of initial folding are limited by geosynclinal belts - huge troughs in which sediments accumulated, mainly in shallow oceanic formations.Often folds are visible in mountainous areas on exposed cliffs, but not only there. Synclinals (troughs) and anticlines (saddles) are the simplest of folds. Some folds are overturned (recumbent).Others are displaced relative to their base so that the upper parts of the folds move out - sometimes by several kilometers, and they are called nappes.

BLOCK MOUNTAINS.

Many large mountain ranges were formed as a result of tectonic uplift that occurred along faults in the earth's crust. The Sierra Nevada Mountains in California are a huge horst about 640 km long and 80 to 120 km wide.The eastern edge of this horst has been raised the highest, where Mount Whitney reaches 418 m above sea level.Much of the modern appearance of the Appalachians was the result of several processes: the original folded mountains were subject to denudation and erosion, and then rose along faults.The Great Basin contains a series of block mountains between the Sierra Nevada Mountains to the west and the Rocky Mountains to the east.Long narrow valleys lie between the ridges; they are partially filled with sediments brought from adjacent blocky mountains.

DOME-SHAPED MOUNTAINS.

domed mountainsIn many areas, land areas that have undergone tectonic uplift have taken on a mountainous appearance under the influence of erosion processes. In those areas where the uplift occurred over a relatively small area and was of a dome-like nature, dome-shaped mountains formed. The Black Hills are a prime example of such mountains, which are about 160 km across.The area was subject to dome uplift and much of the sedimentary cover was removed by further denudation and erosion.The central core was exposed as a result. It consists of metamorphic and igneous rocks. It is surrounded by ridges that consist of more resistant sedimentary rocks.

REMAINING PLATEAUS.

remnant plateaus Due to the action of erosion-denudation processes, a mountain landscape is formed on the site of any elevated territory. Its appearance depends on its original height. When a high plateau like Colorado, for example, was destroyed, a highly dissected mountainous terrain was formed.The Colorado Plateau, hundreds of kilometers wide, was raised to a height of about 3000 m. Erosion-denudation processes have not yet had time to completely transform it into a mountain landscape, but within some large canyons, for example the Grand Canyon of the river. Colorado, mountains several hundred meters high arose.These are erosional remains that have not yet been denuded. With the further development of erosion processes, the plateau will acquire an increasingly pronounced mountain appearance.In the absence of repeated uplift, any territory will eventually be leveled and turn into a plain.

Mountains can be classified according to different criteria: 1) geographical location and age, taking into account their morphology; 2) structural features, taking into account the geological structure. In the first case, mountains are divided into cordilleras, mountain systems, ridges, groups, chains and single mountains.

The name "cordillera" comes from the Spanish word meaning "chain" or "rope". The cordillera includes ranges, groups of mountains and mountain systems of different ages. The Cordillera region of western North America includes the Coast Ranges, Cascade Mountains, Sierra Nevada Mountains, Rocky Mountains, and many small ranges between the Rocky Mountains and Sierra Nevada in the states of Utah and Nevada. The cordilleras of Central Asia include, for example, the Himalayas, Kunlun and Tien Shan.

Mountain systems consist of ranges and groups of mountains that are similar in age and origin (for example, the Appalachians). The ridges consist of mountains stretched out in a long narrow strip. The Sangre de Cristo Mountains, which extend over 240 km in Colorado and New Mexico, are usually no more than 24 km wide, with many peaks reaching heights of 4000–4300 m, are a typical range. The group consists of genetically closely related mountains in the absence of a clearly defined linear structure characteristic of a ridge. Mount Henry in Utah and Mount Bear Paw in Montana are typical examples of mountain groups. In many areas of the globe there are single mountains, usually of volcanic origin. Such are, for example, Mount Hood in Oregon and Mount Rainier in Washington, which are volcanic cones.

The second classification of mountains is based on taking into account endogenous processes of relief formation. Volcanic mountains are formed due to the accumulation of masses of igneous rocks during volcanic eruptions. Mountains can also arise as a result of the uneven development of erosion-denudation processes within a vast territory that has experienced tectonic uplift. Mountains can also be formed directly as a result of tectonic movements themselves, for example, during arched uplifts of sections of the earth's surface, during disjunctive dislocations of blocks of the earth's crust, or during intensive folding and uplift of relatively narrow zones. The latter situation is typical for many large mountain systems of the globe, where orogenesis continues to this day. Such mountains are called folded, although during the long history of development after the initial folding they were influenced by other mountain-building processes.

Fold mountains.

Initially, many large mountain systems were folded, but during subsequent development their structure became very significantly more complex. Zones of initial folding are limited by geosynclinal belts - huge troughs in which sediments accumulated, mainly in shallow oceanic environments. Before folding began, their thickness reached 15,000 m or more. The association of folded mountains with geosynclines seems paradoxical, however, it is likely that the same processes that contributed to the formation of geosynclines subsequently ensured the collapse of sediments into folds and the formation of mountain systems. At the final stage, folding is localized within the geosyncline, since due to the large thickness of sedimentary strata, the least stable zones of the earth's crust arise there.

A classic example of fold mountains is the Appalachians in eastern North America. The geosyncline in which they formed had a much greater extent compared to modern mountains. Over the course of approximately 250 million years, sedimentation occurred in a slowly subsiding basin. The maximum sediment thickness exceeded 7600 m. Then the geosyncline underwent lateral compression, as a result of which it narrowed to approximately 160 km. The sedimentary strata accumulated in the geosyncline were strongly folded and broken by faults along which disjunctive dislocations occurred. During the stage of folding, the territory experienced intense uplift, the speed of which exceeded the rate of impact of erosion-denudation processes. Over time, these processes led to the destruction of the mountains and the reduction of their surface. The Appalachians have been repeatedly uplifted and subsequently denuded. However, not all areas of the original folding zone experienced re-uplift.

Primary deformations during the formation of folded mountains are usually accompanied by significant volcanic activity. Volcanic eruptions occur during folding or shortly after its completion, and large masses of molten magma flow into the folded mountains to form batholiths. They often open up during deep erosional dissection of folded structures.

Many folded mountain systems are dissected by huge thrusts with faults, along which rock covers tens and hundreds of meters thick have shifted for many kilometers. Fold mountains can contain both fairly simple folded structures (for example, in the Jura Mountains) and very complex ones (as in the Alps). In some cases, the process of folding develops more intensively along the periphery of geosynclines, and as a result, two marginal folded ridges and a central elevated part of the mountains with less development of folding are distinguished on the transverse profile. Thrusts extend from the marginal ridges towards the central massif. Massifs of older and more stable rocks that bound a geosynclinal trough are called forelands. Such a simplified structure diagram does not always correspond to reality. For example, in the mountain belt located between Central Asia and Hindustan, there are the sublatitudinal Kunlun Mountains at its northern border, the Himalayas at the southern border, and the Tibetan Plateau between them. In relation to this mountain belt, the Tarim Basin in the north and the Hindustan Peninsula in the south are forelands.

Erosion-denudation processes in folded mountains lead to the formation of characteristic landscapes. As a result of erosional dissection of folded layers of sedimentary rocks, a series of elongated ridges and valleys is formed. The ridges correspond to outcrops of more resistant rocks, while the valleys are carved out of less resistant rocks. Landscapes of this type are found in western Pennsylvania. With deep erosional dissection of a folded mountainous country, the sedimentary layer can be completely destroyed, and the core, composed of igneous or metamorphic rocks, can be exposed.

Block mountains.

Many large mountain ranges were formed as a result of tectonic uplifts that occurred along faults in the earth's crust. The Sierra Nevada Mountains in California are a huge horst of approx. 640 km and width from 80 to 120 km. The eastern edge of this horst was raised most highly, where the height of Mount Whitney reaches 418 m above sea level. The structure of this horst is dominated by granites, which form the core of the giant batholith, but sedimentary strata that accumulated in the geosynclinal trough in which the folded Sierra Nevada mountains were formed were also preserved.

The modern appearance of the Appalachians was largely formed as a result of several processes: the primary fold mountains were exposed to erosion and denudation, and then were uplifted along faults. However, the Appalachians are not typical block mountains.

A series of blocky mountain ranges are found in the Great Basin between the Rocky Mountains to the east and the Sierra Nevada to the west. These ridges were raised as horsts along the faults that bound them, and their final appearance was formed under the influence of erosion-denudation processes. Most of the ridges extend in the submeridional direction and have a width of 30 to 80 km. As a result of uneven uplift, some slopes were steeper than others. Between the ridges lie long narrow valleys, partially filled with sediments carried down from the adjacent blocky mountains. Such valleys, as a rule, are confined to subsidence zones – grabens. It is assumed that the block mountains of the Great Basin were formed in a zone of extension of the earth's crust, since most faults here are characterized by tensile stresses.

Arch Mountains.

In many areas, land areas that experienced tectonic uplift acquired a mountainous appearance under the influence of erosion processes. Where the uplift occurred over a relatively small area and was arched in nature, arched mountains were formed, a striking example of which is the Black Hills Mountains in South Dakota, which are approx. 160 km. The area experienced arch uplift and most of the sedimentary cover was removed by subsequent erosion and denudation. As a result, a central core composed of igneous and metamorphic rocks was exposed. It is framed by ridges consisting of more resistant sedimentary rocks, while the valleys between the ridges are worked out in less resistant rocks.

Where laccoliths (lenticular bodies of intrusive igneous rocks) were intruded into the sedimentary rocks, the underlying sediments could also experience arching uplifts. A good example of eroded arched uplifts is Mount Henry in Utah.

The Lake District in western England also experienced arching, but of somewhat less amplitude than in the Black Hills.

Remnant plateaus.

Due to the action of erosion-denudation processes, mountain landscapes are formed on the site of any elevated territory. The degree of their severity depends on the initial height. When high plateaus, such as Colorado (in the southwestern United States), are destroyed, highly dissected mountainous terrain is formed. The Colorado Plateau, hundreds of kilometers wide, was raised to a height of approx. 3000 m. Erosion-denudation processes have not yet had time to completely transform it into a mountain landscape, however, within some large canyons, for example the Grand Canyon of the river. Colorado, mountains several hundred meters high arose. These are erosional remains that have not yet been denuded. With the further development of erosion processes, the plateau will acquire an increasingly pronounced mountain appearance.

In the absence of repeated uplifts, any territory will eventually be leveled and turn into a low, monotonous plain. Nevertheless, even there, isolated hills composed of more resistant rocks will remain. Such remnants are called monadnocks after Mount Monadnock in New Hampshire (USA).

Volcanic mountains

There are different types. Common in almost every region of the globe, volcanic cones are formed by accumulations of lava and rock fragments erupted through long cylindrical vents by forces operating deep within the Earth. Illustrative examples of volcanic cones are Mount Mayon in the Philippines, Mount Fuji in Japan, Popocatepetl in Mexico, Misti in Peru, Shasta in California, etc. Ash cones have a similar structure, but are not so high and are composed mainly of volcanic scoria - porous volcanic rock, externally like ash. Such cones are found near Lassen Peak in California and northeastern New Mexico.

Shield volcanoes are formed by repeated outpourings of lava. They are usually not as tall and have a less symmetrical structure than volcanic cones. There are many shield volcanoes on the Hawaiian and Aleutian Islands. In some areas, the foci of volcanic eruptions were so close that the igneous rocks formed entire ridges that connected the initially isolated volcanoes. This type includes the Absaroka Range in the eastern part of Yellowstone Park in Wyoming.

Chains of volcanoes occur in long, narrow zones. Probably the most famous example is the chain of volcanic Hawaiian Islands, which extends over 1,600 km. All of these islands were formed as a result of lava outpourings and eruptions of debris from craters located on the ocean floor. If you count from the surface of this bottom, where the depths are approx. 5500 m, then some of the peaks of the Hawaiian Islands will be among the highest mountains in the world.

Thick layers of volcanic deposits can be cut away by rivers or glaciers and turn into isolated mountains or groups of mountains. A typical example is the San Juan Mountains in Colorado. Intense volcanic activity occurred here during the formation of the Rocky Mountains. Lavas of various types and volcanic breccias in this area occupy an area of ​​more than 15.5 thousand square meters. km, and the maximum thickness of volcanic deposits exceeds 1830 m. Under the influence of glacial and water erosion, the volcanic rock masses were deeply dissected and turned into high mountains. Volcanic rocks are currently preserved only on the mountain tops. Below, thick strata of sedimentary and metamorphic rocks are exposed. Mountains of this type are found on areas of lava plateaus prepared by erosion, in particular the Columbia, located between the Rocky and Cascade Mountains.

Distribution and age of mountains.

There are mountains on all continents and many large islands - in Greenland, Madagascar, Taiwan, New Zealand, British, etc. The mountains of Antarctica are largely buried under ice cover, but there are individual volcanic mountains, for example Mount Erebus, and mountain ranges , including the mountains of Queen Maud Land and Mary Baird Land - high and well defined in relief. Australia has fewer mountains than any other continent. In North and South America, Europe, Asia and Africa there are cordilleras, mountain systems, ranges, groups of mountains and single mountains. The Himalayas, located in the south of Central Asia, are the highest and youngest mountain systems in the world. The longest mountain system is the Andes in South America, stretching 7560 km from Cape Horn to the Caribbean Sea. They are older than the Himalayas and apparently had a more complex history of development. The mountains of Brazil are lower and significantly older than the Andes.

In North America, the mountains show very great diversity in age, structure, structure, origin and degree of dissection. The Laurentian Upland, which occupies the territory from Lake Superior to Nova Scotia, is a relic of heavily eroded high mountains that formed in the Archean more than 570 million years ago. In many places, only the structural roots of these ancient mountains remain. Appalachians are intermediate in age. They first experienced uplift in the late Paleozoic c. 280 million years ago and were much higher than now. Then they underwent significant destruction, and in the Paleogene approx. 60 million years ago were re-raised to modern heights. The Sierra Nevada Mountains are younger than the Appalachians. They also went through a stage of significant destruction and re-raising. The Rocky Mountain system of the United States and Canada is younger than the Sierra Nevada, but older than the Himalayas. The Rocky Mountains formed during the Late Cretaceous and Paleogene. They survived two major stages of uplift, the last one in the Pliocene, only 2–3 million years ago. It is unlikely that the Rocky Mountains have ever been higher than they are now. The Cascade Mountains and Coast Ranges of the western United States and most of the Alaskan mountains are younger than the Rocky Mountains. The California Coast Ranges are still experiencing very slow uplift.

Diversity of structure and structure of mountains.

The mountains are very diverse not only in age, but also in structure. The Alps in Europe have the most complex structure. The rock strata there were subjected to unusually powerful forces, which were reflected in the emplacement of large batholiths of igneous rocks and in the formation of an extremely diverse range of overturned folds and faults with enormous amplitudes of displacement. In contrast, the Black Hills have a very simple structure.

The geological structure of the mountains is as diverse as their structures. For example, the rocks that make up the northern part of the Rocky Mountains in the provinces of Alberta and British Columbia are mainly Paleozoic limestones and shales. In Wyoming and Colorado, most of the mountains have cores of granite and other ancient igneous rocks overlain by layers of Paleozoic and Mesozoic sedimentary rocks. In addition, a variety of volcanic rocks are widely represented in the central and southern parts of the Rocky Mountains, but in the north of these mountains there are practically no volcanic rocks. Such differences occur in other mountains of the world.

Although in principle no two mountains are exactly alike, young volcanic mountains are often quite similar in size and shape, as evidenced by the regular cone shapes of Fuji in Japan and Mayon in the Philippines. However, note that many of Japan's volcanoes are composed of andesites (a medium-composition igneous rock), while the volcanic mountains in the Philippines are composed of basalts (a heavier, black-colored rock containing a lot of iron). The volcanoes of the Cascade Mountains in Oregon are composed primarily of rhyolite (a rock containing more silica and less iron compared to basalts and andesites).

ORIGIN OF MOUNTAINS

No one can explain with certainty how mountains were formed, but the lack of reliable knowledge about orogenesis (mountain building) should not and does not hinder scientists' attempts to explain this process. The main hypotheses for the formation of mountains are discussed below.

Submergence of oceanic trenches.

This hypothesis was based on the fact that many mountain ranges are confined to the periphery of continents. The rocks that make up the bottom of the oceans are somewhat heavier than the rocks that lie at the base of the continents. When large-scale movements occur in the bowels of the Earth, oceanic trenches tend to sink, squeezing continents upward, and folded mountains are formed at the edges of the continents. This hypothesis not only does not explain, but also does not recognize the existence of geosynclinal troughs (depressions of the earth's crust) at the stage preceding mountain building. It also does not explain the origin of such mountain systems as the Rocky Mountains or the Himalayas, which are remote from the continental margins.

Kober's hypothesis.

The Austrian scientist Leopold Kober studied in detail the geological structure of the Alps. In developing his concept of mountain building, he attempted to explain the origin of the large thrust faults, or tectonic nappes, that occur in both the northern and southern parts of the Alps. They are composed of thick strata of sedimentary rocks that have been subjected to significant lateral pressure, resulting in the formation of recumbent or overturned folds. In some places, boreholes in the mountains penetrate the same layers of sedimentary rocks three or more times. To explain the formation of overturned folds and associated thrust faults, Kober proposed that central and southern Europe were once occupied by a huge geosyncline. Thick strata of Early Paleozoic sediments accumulated in it under the conditions of an epicontinental sea basin, which filled a geosynclinal trough. Northern Europe and North Africa were forelands composed of very stable rocks. When orogenesis began, these forelands began to move closer together, squeezing upward the fragile young sediments. With the development of this process, which was likened to a slowly tightening vice, the uplifted sedimentary rocks were crushed, formed overturned folds, or were pushed onto the approaching forelands. Kober tried (without much success) to apply these ideas to explain the development of other mountainous areas. In itself, the idea of ​​lateral movement of land masses seems to explain the orogenesis of the Alps quite satisfactorily, but it turned out to be inapplicable to other mountains and therefore was rejected as a whole.

Continental drift hypothesis

comes from the fact that most mountains are located on the continental margins, and the continents themselves are constantly moving in the horizontal direction (drifting). During this drift, mountains form on the edge of the advancing continent. Thus, the Andes were formed during the migration of South America to the west, and the Atlas Mountains as a result of the movement of Africa to the north.

In connection with the interpretation of mountain formation, this hypothesis encounters many objections. It does not explain the formation of the broad, symmetrical folds that occur in the Appalachians and the Jura. In addition, on its basis it is impossible to substantiate the existence of a geosynclinal trough that preceded mountain building, as well as the presence of such generally accepted stages of orogenesis as the replacement of initial folding by the development of vertical faults and the resumption of uplift. However, in recent years, much evidence has been discovered for the continental drift hypothesis, and it has gained many supporters.

Hypotheses of convection (subcrustal) flows.

For more than a hundred years, the development of hypotheses about the possibility of the existence of convection currents in the interior of the Earth, causing deformations of the earth's surface, has continued. From 1933 to 1938 alone, no less than six hypotheses were put forward about the participation of convection currents in mountain formation. However, all of them are based on unknown parameters such as temperatures of the earth’s interior, fluidity, viscosity, crystal structure of rocks, compressive strength of different rocks, etc.

As an example, consider the Griggs hypothesis. It suggests that the Earth is divided into convection cells extending from the base of the earth's crust to the outer core, located at a depth of ca. 2900 km below sea level. These cells are the size of a continent, but usually their outer surface diameter is from 7700 to 9700 km. At the beginning of the convection cycle, the rock masses surrounding the core are highly heated, while at the surface of the cell they are relatively cold. If the amount of heat flowing from the earth's core to the base of the cell exceeds the amount of heat that can pass through the cell, a convection current occurs. As the heated rocks rise upward, the cold rocks from the surface of the cell sink. It is estimated that for matter from the surface of the core to reach the surface of the convection cell, it takes approx. 30 million years. During this time, long-term downward movements occur in the earth's crust along the periphery of the cell. The subsidence of geosynclines is accompanied by the accumulation of sediments hundreds of meters thick. In general, the stage of subsidence and filling of geosynclines continues for ca. 25 million years. Under the influence of lateral compression along the edges of the geosynclinal trough caused by convection currents, the deposits of the weakened zone of the geosyncline are crushed into folds and complicated by faults. These deformations occur without significant uplift of the faulted folded strata over a period of approximately 5–10 million years. When the convection currents finally die out, the compression forces are weakened, the subsidence slows down, and the thickness of the sedimentary rocks that filled the geosyncline rises. The estimated duration of this final stage of mountain building is ca. 25 million years.

Griggs' hypothesis explains the origin of geosynclines and their filling with sediments. It also reinforces the opinion of many geologists that the formation of folds and thrusts in many mountain systems occurred without significant uplift, which occurred later. However, it leaves a number of questions unanswered. Do convection currents really exist? Seismograms of earthquakes indicate the relative homogeneity of the mantle - the layer located between the earth's crust and core. Is the division of the Earth's interior into convection cells justified? If convection currents and cells exist, mountains should arise simultaneously along the boundaries of each cell. How true is this?

The Rocky Mountain systems in Canada and the United States are approximately the same age throughout their entire length. Its uplift began in the Late Cretaceous and continued intermittently throughout the Paleogene and Neogene, but the mountains in Canada are confined to a geosyncline that began to sag in the Cambrian, while the mountains in Colorado are associated with a geosyncline that began to form only in the Early Cretaceous. How does the hypothesis of convection currents explain such a discrepancy in the age of geosynclines, exceeding 300 million years?

Hypothesis of swelling, or geotumor.

The heat released during the decay of radioactive substances has long attracted the attention of scientists interested in the processes occurring in the bowels of the Earth. The release of enormous amounts of heat from the explosion of atomic bombs dropped on Japan in 1945 stimulated the study of radioactive substances and their possible role in mountain building processes. As a result of these studies, J.L. Rich's hypothesis appeared. Rich assumed that somehow large amounts of radioactive substances were locally concentrated in the earth's crust. When they decay, heat is released, under the influence of which the surrounding rocks melt and expand, which leads to swelling of the earth's crust (geotumor). When the land rises between the geotumor zone and the surrounding territory not affected by endogenous processes, geosynclines are formed. Sediment accumulates in them, and the troughs themselves deepen both due to ongoing geotumor and under the weight of precipitation. The thickness and strength of rocks in the upper part of the earth's crust in the geotumor region decreases. Finally, the earth's crust in the geotumor zone turns out to be so high that part of its crust slides along steep surfaces, forming thrusts, crushing sedimentary rocks into folds and uplifting them in the form of mountains. This kind of movement can be repeated until magma begins to pour out from under the crust in the form of huge lava flows. When they cool, the dome settles, and the period of orogenesis ends.

The swelling hypothesis is not widely accepted. None of the known geological processes allows us to explain how the accumulation of masses of radioactive materials can lead to the formation of geotumors 3200–4800 km long and several hundred kilometers wide, i.e. comparable to the Appalachian and Rocky Mountain systems. Seismic data obtained in all regions of the globe do not confirm the presence of such large geotumours of molten rock in the earth's crust.

Contraction, or compression of the Earth, hypothesis

is based on the assumption that throughout the entire history of the existence of the Earth as a separate planet, its volume has constantly decreased due to compression. The compression of the planet's interior is accompanied by changes in the solid crust. Stresses accumulate intermittently and lead to the development of powerful lateral compression and deformation of the crust. Downward movements lead to the formation of geosynclines, which can be flooded by epicontinental seas and then filled with sediment. Thus, at the final stage of development and filling of the geosyncline, a long, relatively narrow wedge-shaped geological body is created from young unstable rocks, resting on the weakened base of the geosyncline and bordered by older and much more stable rocks. When lateral compression resumes, folded mountains complicated by thrust faults form in this weakened zone.

This hypothesis seems to explain both the reduction of the earth's crust, expressed in many folded mountain systems, and the reason for the emergence of mountains in place of ancient geosynclines. Since in many cases compression occurs deep within the Earth, the hypothesis also provides an explanation for the volcanic activity that often accompanies mountain building. However, a number of geologists reject this hypothesis on the grounds that heat loss and subsequent compression were not great enough to produce the folds and faults that are found in modern and ancient mountainous areas of the world. Another objection to this hypothesis is the assumption that the Earth does not lose, but accumulates heat. If this is indeed the case, then the value of the hypothesis is reduced to zero. Further, if the Earth's core and mantle contain a significant amount of radioactive substances that release more heat than can be removed, then the core and mantle expand accordingly. As a result, tensile stresses will arise in the earth's crust, and not compression, and the entire Earth will turn into a hot melt of rocks.

MOUNTAINS AS HUMAN HABITAT

The influence of altitude on climate.

Let's consider some climatic features of mountain areas. Temperatures in the mountains decrease by about 0.6° C for every 100 m of elevation. The disappearance of vegetation cover and the deterioration of living conditions high in the mountains are explained by such a rapid drop in temperature.

Atmospheric pressure decreases with altitude. Normal atmospheric pressure at sea level is 1034 g/cm2. At an altitude of 8800 m, which approximately corresponds to the height of Chomolungma (Everest), the pressure drops to 668 g/cm2. At higher altitudes, more heat from direct solar radiation reaches the surface because the layer of air that reflects and absorbs the radiation is thinner there. However, this layer retains less heat reflected by the earth's surface into the atmosphere. Such heat losses explain the low temperatures at high altitudes. Cold winds, clouds and hurricanes also contribute to lower temperatures. Low atmospheric pressure at high altitudes has a different effect on living conditions in the mountains. The boiling point of water at sea level is 100° C, and at an altitude of 4300 m above sea level, due to lower pressure, it is only 86° C.

The upper border of the forest and the snow line.

Two terms often used in descriptions of mountains are “tree top” and “snow line.” The upper limit of the forest is the level above which trees do not grow or hardly grow. Its position depends on average annual temperatures, precipitation, slope exposure and latitude. In general, the forest line is higher at low latitudes than at high latitudes. In the Rocky Mountains of Colorado and Wyoming it occurs at altitudes of 3400–3500 m, in Alberta and British Columbia it drops to 2700–2900 m, and in Alaska it is located even lower. Quite a few people live above the forest line in conditions of low temperatures and sparse vegetation. Small groups of nomads move throughout northern Tibet, and only a few Indian tribes live in the highlands of Ecuador and Peru. In the Andes in the territories of Bolivia, Chile and Peru there are higher pastures, i.e. at altitudes above 4000 m, there are rich deposits of copper, gold, tin, tungsten and many other metals. All food products and everything necessary for the construction of settlements and mining have to be imported from the lower regions.

The snow line is the level below which snow does not remain on the surface all year round. The position of this line varies depending on the annual amount of solid precipitation, slope exposure, altitude and latitude. Near the equator in Ecuador, the snow line passes at an altitude of approx. 5500 m. In Antarctica, Greenland and Alaska it is raised only a few meters above sea level. In the Colorado Rockies, the height of the snow line is approximately 3,700 m. This does not mean that snowfields are widespread above this level and not below them. In fact, snowfields often occupy protected areas above 3,700 m, but they can also be found at lower altitudes in deep gorges and on northern-facing slopes. Since snowfields, growing every year, can eventually become a source of food for glaciers, the position of the snow line in the mountains is of interest to geologists and glaciologists. In many areas of the world where regular observations of the position of the snow line were carried out at meteorological stations, it was found that in the first half of the 20th century. its level increased, and accordingly the size of snowfields and glaciers decreased. There is now indisputable evidence that this trend has been reversed. It is difficult to judge how stable it is, but if it persists for many years, it could lead to the development of an extensive glaciation similar to the Pleistocene, which ended ca. 10,000 years ago.

In general, the amount of liquid and solid precipitation in the mountains is much greater than on the adjacent plains. This can be both a favorable and a negative factor for mountain residents. Atmospheric precipitation can fully meet the water needs for domestic and industrial needs, but in case of excess it can lead to destructive floods, and heavy snowfalls can completely isolate mountain settlements for several days or even weeks. Strong winds form snow drifts that block roads and railways.

Mountains are like barriers.

Mountains around the world have long served as barriers to communication and some activities. For centuries, the only route from Central Asia to South Asia ran through the Khyber Pass on the border of modern Afghanistan and Pakistan. Countless caravans of camels and foot porters with heavy loads of goods crossed this wild place in the mountains. Famous Alpine passes such as St. Gotthard and Simplon have been used for many years for communication between Italy and Switzerland. Nowadays, the tunnels built under the passes support heavy rail traffic all year round. In winter, when the passes are filled with snow, all transport communications are carried out through tunnels.

Roads.

Due to the high altitudes and rugged terrain, the construction of roads and railways in the mountains is much more expensive than on the plains. Road and rail transport wears out faster there, and rails with the same load fail in a shorter time than on the plains. Where the valley floor is wide enough, the railway track is usually placed along the rivers. However, mountain rivers often overflow their banks and can destroy large sections of roads and railways. If the width of the valley bottom is not sufficient, the roadbed has to be laid along the sides of the valley.

Human activity in the mountains.

In the Rocky Mountains, due to the construction of highways and the provision of modern household amenities (for example, the use of butane for lighting and heating homes, etc.), human living conditions at altitudes up to 3050 m are steadily improving. Here, in many settlements located at altitudes from 2150 to 2750 m, the number of summer houses significantly exceeds the number of houses of permanent residents.

The mountains save you from the summer heat. A good example of such a refuge is the city of Baguio, the summer capital of the Philippines, which is called the “city of a thousand hills.” It is located just 209 km north of Manila at an altitude of approx. 1460 m. At the beginning of the 20th century. The Philippine government built government buildings, housing for employees and a hospital there, since in Manila itself it was difficult to establish effective government work in the summer due to the intense heat and high humidity. The experiment of creating a summer capital in Baguio was very successful.

Agriculture.

In general, terrain features such as steep slopes and narrow valleys limit the development of agriculture in the temperate mountains of North America. There, small farms mainly grow corn, beans, barley, potatoes and, in some places, tobacco, as well as apples, pears, peaches, cherries and berry bushes. In very warm climates, bananas, figs, coffee, olives, almonds and pecans are added to this list. In the north temperate zone of the Northern Hemisphere and in the south of the southern temperate zone, the growing season is too short for most crops to ripen and late spring and early autumn frosts are common.

Pasture farming is widespread in the mountains. Where summer rainfall is abundant, grass grows well. In the Swiss Alps, in the summer, entire families move with their small herds of cows or goats to the high mountain valleys, where they practice cheese making and make butter. In the Rocky Mountains of the United States, large herds of cows and sheep are driven each summer from the plains to the mountains, where they gain weight in the rich meadows.

Logging

- one of the most important sectors of the economy in the mountainous regions of the globe, ranking second after pasture livestock farming. Some mountains are bare of vegetation due to lack of rainfall, but in temperate and tropical zones most mountains are (or were formerly) covered with dense forests. The variety of tree species is very large. Tropical mountain forests produce valuable deciduous wood (red, rosewood, ebony, teak).

Mining industry.

Mining of metal ores is an important sector of the economy in many mountainous regions. Thanks to the development of deposits of copper, tin and tungsten in Chile, Peru and Bolivia, mining settlements arose at altitudes of 3700–4600 m, where the cold, strong winds and hurricanes create the most difficult living conditions. The productivity of miners there is very low, and the cost of mining products is prohibitively high.

Population density.

Due to the peculiarities of climate and topography, mountainous areas often cannot be as densely populated as lowland ones. For example, in the mountainous country of Bhutan, located in the Himalayas, the population density is 39 people per 1 sq. km, while at a short distance from it on the low Bengal plain in Bangladesh it is more than 900 people per 1 sq. km. Similar differences in population density between the highlands and the lowlands exist in Scotland.

Representing a sharp rise among the rest of the territory, with significant differences in elevation - up to several kilometers. Sometimes mountains have a fairly clear base line at the slope, but more often they have foothills.

Finding folded mountains on a map is very easy, because mountains as such are everywhere, on absolutely all continents and even on every island. Somewhere there are more of them, somewhere there are fewer, as, for example, in Australia. In Antarctica, they are hidden by an ice layer. The highest (and youngest) mountain system is the Himalayas, the longest is the Andes, which stretch across South America for seven and a half thousand kilometers.

How old are the mountains?

Mountains are like people, they too can be young, mature and old. But if the younger people are, the smoother they are, then with the mountains it’s the opposite: sharp relief and high altitudes indicate young age.

In old mountains, the relief is worn out, smoothed, and the heights do not have such large differences. For example, the Pamirs are young mountains, and the Ural mountains are old, any map will show this.

Relief characteristics

Fold mountains have an integral structure, but for a more detailed examination you need to know the principles by which the general characteristics of the relief are compiled. This applies not only to literally meter-long deviations from the state of flat lands - this is the so-called mountain microrelief. Accurate knowledge of what types of mountains there are depends on the ability to correctly classify.

Here it is necessary to consider such elements as foothills, valleys, slopes, moraines, passes, ridges, peaks, glaciers and many others, since there are a variety of mountains on earth, including folded mountains.

Classification of mountains by height

The height can be classified very simply - there are only three groups:

• Lowlands with a height of no more than a kilometer. Most often these are old mountains, destroyed by time, or very young, gradually growing. They have rounded tops and gentle slopes on which trees grow. There are such mountains on every continent.
• Srednegorye in height from one thousand to three thousand meters. Here there is a different, changing landscape, depending on the height - the so-called altitudinal zone. Such mountains are in Siberia and the Far East, on the Apennine, Iberian Peninsulas, Scandinavian, Appalachians and many others.
• Highlands- more than three thousand meters. These are always young mountains, subject to weathering, temperature changes and glacial growth. Characteristic features: troughs - trough-shaped valleys, carlings - sharp peaks, glacial cirques - bowl-like depressions on the slopes. Here the altitude is marked by belts - forest at the foot, icy deserts closer to the tops. The term that summarizes these characteristic features is “alpine landscape”. The Alps are a very young mountain system, as are the Himalayas, Karakoram, Andes, Rocky and other folded mountains.

Classification of mountains by geographic location

Geographical location divides the relief into systems, groups of mountains, mountain ranges and single mountains. The largest formations are mountain belts: Alpine-Himalayan - across all of Eurasia, Andean-Cordillera - across both Americas.

A slightly smaller country is a mountainous country, that is, many united mountain systems. In turn, the mountain system consists of groups of mountains and ranges of the same age, most often these are folded mountains. Examples: Appalachia, Sangre de Cristo.

A group of mountains differs from a ridge in that it does not line its peaks in a narrow, long strip. Single mountains are most often of volcanic origin. Based on their appearance, the peaks are divided into peak-shaped, plateau-shaped, dome-shaped and some others. Seamounts can form islands with their peaks.

Formation of mountains

Orogenesis is the most complex of processes, as a result of which rocks are crushed into folds. Scientists know for sure what fold mountains are, but only hypotheses are considered about how they appeared.

• The first hypothesis is oceanic depressions. The map clearly shows that all mountain systems are located on the outskirts of continents. This means that continental rocks are lighter than ocean bottom rocks. Movements inside the Earth seem to squeeze the continent out of its interior, and folded mountains are bottom surfaces that have emerged onto land. This theory has many opponents. For example, the folded mountains are the Himalayas, which are clearly not bottom, since they are located on the mainland itself. And according to this hypothesis, it is impossible to explain the existence of depressions - geosynclinal troughs.
• Leopold Kober's hypothesis, who studied his native Alps. These young mountains have not yet been subjected to destructive processes. It turned out that large tectonic thrusts formed huge layers of sedimentary rocks. The Alpine mountains have clarified their origin, but this path is absolutely not similar to the emergence of other mountains; it was not possible to apply this theory anywhere else.
• Continental drift- a very popular theory, which is also criticized as not explaining the entire process of orogenesis.
• Subcortical currents in the bowels of the Earth cause deformation of the surface and form mountains. However, this hypothesis has not been proven either. On the contrary, humanity does not yet know even such parameters as the temperature of the earth’s interior, much less the viscosity, fluidity and crystalline structure of deep rocks, compressive strength, and so on.
• Earth compression hypothesis- with its own advantages and disadvantages. We do not know whether the planet accumulates heat or loses it; if it loses it, this theory is valid; if it accumulates it, it does not.

What types of mountains are there?

All kinds of sedimentary rocks accumulated in the troughs of the earth's crust, which were then crushed and, with the help of volcanic activity, folded mountains were formed. Examples: Appalachia on the east coast of North America, Zagros Mountains in Turkey.

Block mountains appeared due to tectonic uplifts along faults in the earth's crust. Like, for example, the Californian ones - Sierra Levada. But sometimes the already formed folds suddenly begin to rise along the fault. This is how folded block mountains are formed. The most typical are Appalachians.

Those mountains that were formed as folded strata of rocks, but were broken by young faults into blocks and rose to different heights, are also folded blocky. The Tien Shan Mountains, for example, as well as the Altai Mountains.

The vaulted mountains are a vaulted tectonic uplift plus erosion processes over a small area. These are the mountains of the Lake District in England, as well as the Black Hills in South Dakota.

Volcanic ones were formed under the influence of lava. There are two types: volcanic cones (Fuji and others like them) and shield volcanoes (less tall and not so symmetrical).

Mountain climate

The mountain climate is radically different from the climate of any other areas. Temperatures drop by more than half a degree for every hundred meters of altitude. The wind is also usually very cold, helped by cloud cover. Frequent hurricanes.

As you gain altitude, the atmospheric pressure decreases. On Everest, for example, up to 250 millimeters of mercury. Water boils at eighty-six degrees.

The higher you go, the less vegetation cover, until it is completely absent, and life is almost completely absent in glaciers and snow caps.

Linear zones

Thanks to fault-tectonic analysis, it was possible to create a definition of what fold mountains are, how they were formed, and how dependent they are on deep planetary faults. All - both ancient and modern - mountain areas are included in certain linear zones, which were formed in only two directions - northwest and northeast, repeating the direction of deep faults.

These belts are bordered by platforms. There is a dependence: the position and shape of the platform changes, and the external shapes and orientation in space of the folded belts change. When mountains are formed, everything is decided by fault tectonics (blocks) of the crystalline base. The vertical movements of the foundation blocks form folded mountains.

Examples of the Carpathians or the Verkhoyansk-Chukchi region show various types of tectonic movements during the formation of mountain folds. The Zagros Mountains arose in the same way.

Geological structure

In the mountains, everything is varied - from structure to structure. for example, the same Rocky Mountains change throughout their entire length. In the northern part - Paleozoic shales and limestones, further - closer to Colorado - granites, igneous rocks with Mesozoic sediments. Even further - in the central part - there are volcanic rocks, which are not present at all in the northern areas. The same picture will appear if we consider the geological structure of many other mountain ranges.

They say that no two mountains are alike, but massifs of volcanic origin, for example, often have a number of similar features. The correctness of the outlines of the Japanese cone and for example. But if we now begin a detailed geological analysis, we will see that the saying is quite right. Many Japanese volcanoes are composed of andesite (magma), while the Philippine rocks are basaltic, much heavier due to their high iron content. And the Cascade Mountains of Oregon built their volcanoes with rhyolite (silica).

Time of formation of fold mountains

The formation of mountains in the entire process occurred due to the development of geosynclines in various geological periods, even in the eras of folding before the Cambrian. But modern mountains include only young (relatively, of course) Cenozoic uplifts. More ancient mountains were leveled a long time ago and were again raised by new tectonic movements in the form of blocks and arches.

Vault-block mountains are most often revived. They are as common as the younger, folded ones. Today's is neotectonics. You can study the folding that formed tectonic structures if you consider the difference in the age of the mountains, and not the relief it created. If the Cenozoic is recent, then it is difficult to think about the age of the very first rock formations.

And only volcanic mountains can grow right before our eyes - during the entire eruption. Eruptions most often occur in the same place, so each portion of lava builds up the mountain. In the center of the continent, a volcano is a rarity. They tend to form entire underwater islands, often forming arcs several thousand kilometers long.

How mountains die

The mountains could stand forever. But they are being killed, albeit slowly when compared to human life. This is, first of all, frost, splitting the rock into small pieces. This is how screes are formed, which are then carried down by snow or ice, building moraine ridges. This is water - rain, snow, hail - making its way even through such indestructible walls. The water collects in rivers, which form valleys winding between mountain spurs. The history of the destruction of immutable mountains is, of course, long, but inevitable. And the glaciers! Entire spurs are sometimes completely cut off by them.

Such erosion gradually reduces the mountains, turning them into a plain: somewhere green, with deep rivers, somewhere deserted, polishing all the remaining hills with sand. This surface of the Earth is called "peneplain" - almost a plain. And, I must say, this stage occurs extremely rarely. The mountains are being reborn! The earth's crust begins to move again, the terrain rises, beginning a new phase of relief development.

Mountains occupy about 24% of all land. The most mountains are in Asia - 64%, the least in Africa - 3%. 10% of the world's population lives in the mountains. And it is in the mountains that most rivers on our planet originate.

Characteristics of mountains

According to their geographical location, mountains are united into various communities that should be distinguished.

. Mountain belts- the largest formations, often stretching across several continents. For example, the Alpine-Himalayan belt passes through Europe and Asia or the Andean-Cordilleran belt, stretching through North and South America.
. Mountain system- groups of mountains and ranges similar in structure and age. For example, the Ural Mountains.

. Mountain ranges- a group of mountains stretched in a line (Sangre de Cristo in the USA).

. Mountain groups- also a group of mountains, but not stretched out in a line, but simply located nearby. For example, the Bear Pau Mountains in Montana.

. Single mountains- unrelated to others, often of volcanic origin (Table Mountain in South Africa).

Natural areas of the mountains

Natural zones in the mountains are arranged in layers and change depending on the height. At the foothills there is most often a zone of meadows (in the highlands) and forests (in the middle and low mountains). The higher you go, the harsher the climate becomes.

The change of belts is influenced by climate, altitude, mountain topography and their geographical location. For example, the continental mountains do not have a belt of forests. From the base to the summit, the natural areas vary from deserts to grasslands.

Types of mountains

There are several classifications of mountains according to various criteria: structure, shape, origin, age, geographical location. Let's look at the most basic types:

1. By age old and young mountains are distinguished.

Old are called mountain systems whose age is estimated at hundreds of millions of years. Internal processes in them have calmed down, but external processes (wind, water) continue to destroy, gradually comparing them with the plains. The old mountains include the Ural, Scandinavian, and Khibiny mountains (on the Kola Peninsula).

2. Height There are low mountains, middle mountains and high mountains.

Low mountains (up to 800 m) - with rounded or flat tops and gentle slopes. There are many rivers in such mountains. Examples: Northern Urals, Khibiny Mountains, spurs of the Tien Shan.

Average mountains (800-3000 m). They are characterized by a change in landscape depending on the height. These are the Polar Urals, the Appalachians, the mountains of the Far East.

High mountains (over 3000 m). These are mostly young mountains with steep slopes and sharp peaks. Natural areas change from forests to icy deserts. Examples: Pamirs, Caucasus, Andes, Himalayas, Alps, Rocky Mountains.

3. By origin There are volcanic (Fuji), tectonic (Altai mountains) and denudation, or erosion (Vilyui, Ilim).

4. According to the shape of the top mountains can be peak-shaped (Communism Peak, Kazbek), plateau-shaped and table-shaped (Amba in Ethiopia or Monument Valley in the USA), domed (Ayu-Dag, Mashuk).

Climate in the mountains

The mountain climate has a number of characteristic features that appear with altitude.

Decrease in temperature - the higher it is, the colder it is. It is no coincidence that the peaks of the highest mountains are covered with glaciers.

Atmospheric pressure decreases. For example, at the top of Everest the pressure is two times lower than at sea level. This is why water boils faster in the mountains - at 86-90ºC.

The intensity of solar radiation increases. In the mountains, sunlight contains more ultraviolet radiation.

The amount of precipitation is increasing.

High mountain ranges trap precipitation and influence the movement of cyclones. Therefore, the climate on different slopes of the same mountain may differ. On the windward side there is a lot of moisture and sun, on the leeward side it is always dry and cool. A striking example is the Alps, where on one side of the slopes there are subtropics, and on the other, a temperate climate prevails.

The highest mountains in the world

(Click on the picture to enlarge the diagram in full size)

There are seven highest peaks in the world that all climbers dream of conquering. Those who succeed become honorary members of the Seven Peaks Club. These are mountains such as:

. Chomolungma, or Everest (8848 m). Located on the border of Nepal and Tibet. Belongs to the Himalaya mountain system. It has the shape of a triangular pyramid. The first conquest of the mountain took place in 1953.

. Aconcagua(6962 m). It is the highest mountain in the southern hemisphere, located in Argentina. Belongs to the Andes mountain system. The first ascent took place in 1897.

. McKinley- the highest peak in North America (6168 m). Located in Alaska. First conquered in 1913. It was considered the highest point in Russia until Alaska was sold to America.

. Kilimanjaro- the highest point in Africa (5891.8 m). Located in Tanzania. First conquered in 1889. This is the only mountain where all types of Earth's belts are represented.

. Elbrus- the highest peak in Europe and Russia (5642 m). Located in the Caucasus. The first ascent took place in 1829.

. Vinson Massif- the highest mountain in Antarctica (4897 m). Part of the Ellsworth Mountains system. First conquered in 1966.

. Mont Blanc- the highest point in Europe (many attribute Elbrus to Asia). Height - 4810 m. Located on the border of France and Italy, it belongs to the Alps mountain system. The first ascent in 1786, and a century later, in 1886, Theodore Roosevelt conquered the top of Mont Blanc.

. Pyramid of Carstens- the highest mountain in Australia and Oceania (4884 m). Located on the island of New Guinea. The first conquest was in 1962.

Mountains differ not only in their height, diversity of landscape, size, but also in their origin. There are three main types of mountains: block, fold and dome mountains.

How block mountains are formed

The earth's crust does not stand still, but is in constant motion. When cracks or faults of tectonic plates appear in it, huge masses of rock begin to move not in the longitudinal, but in the vertical direction. Part of the rock may fall, while the other part adjacent to the fault may rise. An example of the formation of block mountains is the Teton mountain range. This ridge is located in the state of Wyoming. On the eastern side of the ridge you can see sheer rocks that rose when the earth's crust fractured. On the other side of the Teton Range is a valley that has dropped down.

How fold mountains form

The parallel movement of the earth's crust leads to the appearance of folded mountains. The appearance of folded mountains can best be seen using the example of the famous Alps. The Alps arose as a result of the collision of the lithospheric plate of the continent of Africa and the lithospheric plate of the continent of Eurasia. For several million years, these plates were in contact with each other under enormous pressure. As a result, the edges of the lithospheric plates were crushed, forming giant folds, which over time were covered with faults. This is how one of the most majestic mountain ranges in the world was formed.

How domed mountains are formed

Inside the earth's crust there is hot magma. Magma, breaking upward under enormous pressure, lifts the rocks that lie above. This results in a dome-shaped bend of the earth's crust. Over time, wind erosion exposes the igneous rock. An example of dome-shaped mountains is the Drakensberg Mountains, located in South Africa. More than a thousand meters high, weathered igneous rock is clearly visible in it.