Block mountains. Block mountains - formation, features, examples of block mountains Block mountains 1 3 on the world map

Block Mountains

are formed as a result of breaking rock layers into separate blocks (blocks) and raising them to different heights. They arise, as a rule, where rocks, as a result of a long and complex development, have lost their plasticity (consolidated) and, under the influence of endogenous forces, behave like a fragile body, splitting into blocks. The faults separating the blocks can be deep. from 1–3 km to several tens of kilometers, they can be vertical (faults) or inclined (thrusts). In the relief, faults are expressed either as ledges or as linear valleys developed by erosion. Block mountains often have relatively flat, horizontal or slightly inclined peaks, representing the undisturbed surface of raised blocks; They are characterized by steep slopes and relatively sparse dissection. If the raised blocks as a whole form a gently convex shape, such mountains are called vaulted blocky. An example of block mountains is the Sierra Nevada mountains in the western north. America, Northern ridge system. Tien Shan.

Geography. Modern illustrated encyclopedia. - M.: Rosman. Edited by prof. A. P. Gorkina. 2006 .

See what “block mountains” are in other dictionaries:

block mountains- Mountains formed by multidirectional movements of crustal blocks along faults. Syn.: fault mountains... Dictionary of Geography

block mountains- - Topics oil and gas industry EN block type of mountain ... Technical Translator's Guide

Uplifts of the earth's crust limited by tectonic faults. G. is characterized by: massiveness, steep slopes, and relatively weak dissection. They usually appear in folded zones that once had mountainous terrain, but have lost... ...

fold-block mountains- Mountains formed through the combined action of folded and block tectonic processes... Dictionary of Geography

Mountains formed by folded rock strata, broken along young fault lines into blocks raised to different heights. Usually they are so-called. revived mountains formed within epiplatform orogenic belts... ... Great Soviet Encyclopedia

A collection of closely located individual mountains, mountain ranges, mountain spurs, ridges, highlands, as well as the canyons, valleys, and depressions separating them, occupying a certain territory, more or less clearly separated from the surrounding plains. By… … Geographical encyclopedia

1. in Greek mythology ora, in Greek mythology, the goddess of nature and the seasons. There were usually three of them, and they represented spring, summer and winter. They were depicted as young and beautiful maidens, accompanied by nymphs and graces (charites). According to… … Collier's Encyclopedia

Formed by blocks of the earth's crust, raised and moved relative to each other. There are mountains formed by: a) blocks folded horizontally, and b) previously folded structures, later peneplanated and... ... Geological encyclopedia

Formed by the latest text. movements in place of platforms of different ages, ch. arr. in place of foundation protrusions in the form of shields (basement plains). Composed of p., usually metamorphosed to one degree or another, sometimes crystalline, crushed into... ... Geological encyclopedia

Not to be confused with mountains as isolated sharp rises of rock, as well as peaks in mountainous countries. Mountains are strongly dissected parts of land, significantly elevated, by 500 meters or more, above the adjacent plains. From the plains of the mountains... ... Wikipedia

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Block mountains are formed as a result of breaking rock layers into separate blocks (blocks) and raising them to different heights. They arise, as a rule, where rocks, as a result of a long and complex development, have lost their plasticity (consolidated) and, under the influence of endogenous forces, behave like a fragile body, splitting into blocks. The faults separating the blocks can be deep. from 1–3 km to several tens of kilometers, they can be vertical (faults) or inclined (thrusts). In the relief, faults are expressed either as ledges or as linear valleys developed by erosion. often have relatively flat, horizontal or slightly inclined peaks, representing the undisturbed surface of raised blocks; They are characterized by steep slopes and relatively sparse dissection. If the raised blocks as a whole form a gently convex shape, such mountains are called vaulted block mountains. An example of block mountains is the Sierra Nevada mountains in the western north. America, Northern ridge system. Tien Shan.

Meanings in other dictionaries

Glubokoe

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Glukhov

Glukhiv, a city in the Sumy region. (Ukraine), 115 km to the northwest. from Sumy. 36 thousand inhabitants (1996). The city has been known since 1152. It was a center of grain and sugar trade. prom-sti. Anastasyevsky Cathedral, Kyiv Triumphal Gate (1766), Gamaleevsky Monastery; churches (XVII–XVIII centuries) – Nikolaevskaya, Spaso-Preobrazhenskaya, Voznesenskaya. Pedagogical Institute (1874); Research Institute of Bast Crops. Museums: local history and partisan...

Glaciology

Glaciology is the science of natural systems whose properties and dynamics are determined by ice. The subject of its study is natural ice on the Earth's surface, in the atmosphere, hydrosphere and lithosphere - the regime and dynamics of their development, interaction with the environment, the role of ice in the evolution of the Earth. United natural object The study of glaciology is the glaciosphere and its constituent nival-glacial systems...

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. Cordillera region in the west North America includes the Coast Ranges, Cascade Mountains, Sierra Nevada, Rocky Mountains, and many small ranges between the Rocky Mountains and Sierra Nevada in 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 connected mountains in the absence of a clearly defined linear structure characteristic of the ridge. Mount Henry in Utah and Mount Bear Paw in Montana are typical examples of mountain groups. In many areas 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 the folded mountainous country the sedimentary sequence may be completely destroyed, and the core, composed of igneous or metamorphic rocks, may 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 managed to completely transform it into a mountain landscape, but within some large canyons, for example Grand Canyon R. 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. Lava 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, such as Mount Erebus, and mountain ranges, including the mountains of Queen Maud Land and Mary Baird's lands are 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 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 relict of heavily eroded high mountains, 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. So, the Andes were formed during migration 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 last years Much evidence was found for the continental drift hypothesis, and it 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 emerged. 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 geotumours with a length of 3200–4800 km and a width of several hundred kilometers, 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 geotumors 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, everything transport connection carried out through tunnels.

Roads.

Due to the high altitudes and rugged terrain, the construction of road and railways in the mountains it is much more expensive than on the plains. Automotive and railway transport there it wears out faster, 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 clear 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 in small farms They 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 climate and terrain mountainous areas often cannot be populated as densely 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.

Table: Mountain Peaks

MOUNTAIN PEAKS
	Absolute height, m		Absolute height, m
EUROPE		NORTH AMERICA
Elbrus, Russia	5642	McKinley, Alaska	6194
Dykhtau, Russia	5203	Logan, Canada	5959
Kazbek, Russia – Georgia	5033	Orizaba, Mexico	5610
Mont Blanc, France	4807	St. Elias, Alaska - Canada	5489
Ushba, Georgia	4695	Popocatepetl, Mexico	5452
Dufour, Switzerland – Italy	4634	Foraker, Alaska	5304
Weisshorn, Switzerland	4506	Iztaccihuatl, Mexico	5286
Matterhorn, Switzerland	4478	Lukenia, Canada	5226
Bazarduzu, Russia – Azerbaijan	4466	Bona, Alaska	5005
Finsterarhorn, Switzerland	4274	Blackburn, Alaska	4996
Jungfrau, Switzerland	4158	Sanford, Alaska	4949
Dombay-Ulgen (Dombay-Elgen), Russia – Georgia	4046	Wood, Canada	4842
		Vancouver, Alaska	4785
ASIA		Churchill, Alaska	4766
Qomolangma (Everest), China – Nepal	8848	Fairweather, Alaska	4663
Chogori (K-2, Godwin-Austen), China	8611	Bare, Alaska	4520
		Hunter, Alaska	4444
Kanchenjunga, Nepal - India	8598	Whitney, California	4418
Lhotse, Nepal - China	8501	Elbert, Colorado	4399
Makalu, China – Nepal	8481	Massive, Colorado	4396
Dhaulagiri, Nepal	8172	Harvard, Colorado	4395
Manaslu, Nepal	8156	Rainier, Washington	4392
Chopu, China	8153	Nevado de Toluca, Mexico	4392
Nanga Parbat, Kashmir	8126	Williamson, California	4381
Annapurna, Nepal	8078	Blanca Peak, Colorado	4372
Gasherbrum, Kashmir	8068	La Plata, Colorado	4370
Shishabangma, China	8012	Uncompahgre Peak, Colorado	4361
Nandadevi, India	7817	Creston Peak, Colorado	4357
Rakaposhi, Kashmir	7788	Lincoln, Colorado	4354
Kamet, India	7756	Grays Peak, Colorado	4349
Namchabarwa, China	7756	Antero, Colorado	4349
Gurla Mandhata, China	7728	Evans, Colorado	4348
Ulugmuztag, China	7723	Longs Peak, Colorado	4345
Kongur, China	7719	White Mountain Peak, California	4342
Tirichmir, Pakistan	7690	North Palisade, California	4341
Gungashan (Minyak-Gankar), China	7556	Wrangel, Alaska	4317
Kula Kangri, China – Bhutan	7554	Shasta, California	4317
Muztagata, China	7546	Sill, California	4317
Communism Peak, Tajikistan	7495	Pikes Peak, Colorado	4301
Pobeda Peak, Kyrgyzstan – China	7439	Russell, California	4293
Jomolhari, Bhutan	7314	Split Mountain, California	4285
Lenin Peak, Tajikistan – Kyrgyzstan	7134	Middle Palisade, California	4279
Korzhenevsky peak, Tajikistan	7105	SOUTH AMERICA
Khan Tengri Peak, Kyrgyzstan	6995	Aconcagua, Argentina	6959
Kangrinboche (Kailas), China	6714	Ojos del Salado, Argentina	6893
Khakaborazi, Myanmar	5881	Bonete, Argentina	6872
Damavand, Iran	5604	Bonete Chico, Argentina	6850
Bogdo-Ula, China	5445	Mercedario, Argentina	6770
Ararat, Türkiye	5137	Huascaran, Peru	6746
Jaya, Indonesia	5030	Llullaillaco, Argentina – Chile	6739
Mandala, Indonesia	4760	Yerupaja, Peru	6634
Klyuchevskaya Sopka, Russia	4750	Galan, Argentina	6600
Trikora, Indonesia	4750	Tupungato, Argentina – Chile	6570
Belukha, Russia	4506	Sajama, Bolivia	6542
Munkhe-Khairkhan-Uul, Mongolia	4362	Coropuna, Peru	6425
AFRICA		Illhampu, Bolivia	6421
Kilimanjaro, Tanzania	5895	Illimani, Bolivia	6322
Kenya, Kenya	5199	Las Tortolas, Argentina – Chile	6320
Rwenzori, Congo (DRC) – Uganda	5109	Chimborazo, Ecuador	6310
Ras Dasheng, Ethiopia	4620	Belgrano, Argentina	6250
Elgon, Kenya – Uganda	4321	Toroni, Bolivia	5982
Toubkal, Morocco	4165	Tutupaka, Chile	5980
Cameroon, Cameroon	4100	San Pedro, Chile	5974
AUSTRALIA AND OCEANIA		ANTARCTICA
Wilhelm, Papua New Guinea	4509	Vinson array	5140
Giluwe, Papua New Guinea	4368	Kirkpatrick	4528
Mauna Kea, o. Hawaii	4205	Markham	4351
Mauna Loa, o. Hawaii	4169	Jackson	4191
Victoria, Papua New Guinea	4035	Sidley	4181
Capella, Papua New Guinea	3993	Minto	4163
Albert Edward, Papua New Guinea	3990	Wörterkaka	3630
Kosciusko, Australia	2228	Menzies	3313

Mountains are folded, blocky, folded-blocky

Fold mountains are uplifts of the earth's surface that arise in moving zones of the earth's crust. They are most characteristic of young geosynclinal zones. In them, thicker rocks are crushed into folds of varying sizes and steepness, raised to a certain height. First, the relief of folded mountains corresponds to tectonic structures: ridges - anticlines, valleys - synclines; subsequently this correspondence is violated.

Block mountains are uplifts of the earth's surface, separated by tectonic faults. Block mountains are characterized by massiveness, steep slopes, and relatively insignificant dissection. They occur in areas that previously had mountainous terrain and were leveled by denudation, as well as in flat areas.

Folded-block mountains are uplifts of the earth's surface caused by complex deformations of the earth's crust - plastic and discontinuous.

Folded-block mountains arise mainly from the deformation and uplifting of rock strata, which have become folded and have lost their plasticity. Widely distributed in young geosynclinal zones. Examples of folded-block mountains are the mountains of the Tien Shan, Altai, and the mountains of a significant part of the Balkan Peninsula.

Concept of a river valley

River valleys are relatively narrow long basins formed by rivers that have a slope, in accordance with their flow, from the upper reaches to the lower reaches. Valleys can be winding or straight. The components of a young river valley are the bottom and slopes, in a later period of development - the riverbed and bed of the river, floodplains, terraces, and the bedrock bank. The depth, width, and number of terraces in a river valley depend on the age and power of the river, the geological structure of the area, the position of the erosion base, and general changes in physical and geographical conditions. The origin of the river valley is mainly erosional, but many of them, especially large ones, have a tectonic structure. River valleys produced from heterogeneous rocks, and those that reflect features geological structure areas are called structural river valleys. The main structural types of valleys include: synclinal valleys (rock folds are convexly directed downwards) anticlinal valleys (a successively layered convex bend, the core of which is composed of ancient layers of rocks, and the upper part is younger) monoclinal valley (longitudinal, of course asymmetrical valley, produced in rocks , lying with the slope of the layers in one direction) valley-graben (formed in places of rock rupture and subsidence of the central blocks, the side ones remain at the same level or rise).

Plain areas, often inclined towards the channel, and systems of degrees in river valleys, created by the erosive and accumulative work of the river, form river terraces. They are divided: according to height above the valley bottom - into floodplain and above-floodplain terraces; for morphological character and structure - into enclosed and superimposed terraces.

A floodplain is a part of a river valley dotted with vegetation and is inundated only during a flood. The floodplain has many depressions. They alternate with ridges. The riverbed floodplain is the highest, with alluvium; the central floodplain is lower, with less mud; near-terraces - the most reduced, swampy, adjacent to a high bank and composed of silt. Floodplains up to 40 km wide are characteristic of large lowland rivers with uneven flow. Floodplain soils, which are replenished with organic silt, are very fertile.

The importance of relief in human economic activity

The relief of the earth's surface leads to many features of a given territory, and therefore during any construction, mineral exploration, agriculture and military affairs, its specifics always have to be taken into account.

The location and configuration of agricultural land, the use of this or that equipment, the nature of reclamation work, and the placement of agricultural crops depend on the relief.

The slope of the surface affects the conditions of water flow, moisture content, the intensity of soil loss and the formation of ravines. Gullies reduce the area of arable land and cut roads.

The angle of incidence of the sun's rays on the surface of the earth depends on the steepness of the terrain. The southern slope is warm, the western and eastern slopes are intermediate. Therefore, the duration of the frost-free period on convex landforms is slightly longer than in hollows.

Depending on the nature of the relief, rivers are divided into flat and mountainous. Lowland rivers are mainly used for timber rafting and river transport, and the mountainous ones are rich in hydro resources and hydroelectric power stations are being built on them.

The terrain affects the volume of excavation work during road construction. With a slight steepness of the slope and rough terrain, the volume of excavation work and the cost of construction increase. When choosing highway and railway routes and their construction, the possibility of karst phenomena, landslides, etc. is taken into account.

To design industrial facilities, settlements, you need to know well the relief of the surrounding area and the processes that create this relief.

Some areas of the earth's crust are very swampy, although they are quite suitable for agricultural use. When draining swamps (reclamation) work is carried out there, ditches and canals are dug through which swamp water flows into rivers. However, before digging these ditches and canals, the slope of the terrain must be determined. To do this, they use accurate topographic maps and special geodetic techniques called leveling. Leveling determines the heights of neighboring terrain points, that is, the excess of one terrain point over another is determined.

Without knowing the relief and without taking into account its features, it is impossible to use the territory for farming with maximum efficiency.

2. Fold Mountains.

3. Block mountains.

4. Arch Mountains.

5. Remnant plateaus.

6. Distribution and age of mountains.

7. Diversity of structure and structure of mountains.

8. Origin of mountains.

9. Mountains as a human habitat.

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MOUNTAINS, elevated areas of the earth's surface, rising steeply above the surrounding area. Unlike plateaus, peaks in mountains occupy a small area.

1. Classification of mountains

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 smaller 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 TOP OF ARARAT in eastern Turkey on the border with Armenia. On the right is the 17th century monastery.

2. Fold Mountains

STAGES OF OROGENESIS in the Appalachians: initial - accumulation of sediments in an elongated oceanic trough - geosynclines (top). The intrusion of igneous rocks (middle) results in the uplift of primary sedimentary rocks and the formation of mountains, while sedimentation continues. Subsequently, younger sediments (below) are also involved in the uplift, which at the same time experience folding and discontinuous deformations.

The intrusion of igneous rocks (middle) results in the uplift of primary sedimentary rocks and the formation of mountains, while sedimentation continues. Subsequently, younger sediments (below) are also involved in the uplift, which at the same time experience folding and discontinuous deformations.

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.