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 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 areas 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, 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 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, 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.

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



Geologists call folded-block or simply block mountains orographic structures that formed and rose in ancient geological eras, but much later rejuvenated and split into separate blocks or blocks when the territory was re-uplifted. Most of the mountain systems on the planet are folded and blocky, because folded structures are rare. When ancient mountains rejuvenate, the formation of folds is necessarily accompanied by the appearance of faults and the formation of block formations.

Folded-block mountain systems mostly appear on the site of ancient mountainous countries already destroyed by erosion. With the activation of tectonic processes in places of the most ancient orographic structures that have become peneplains, new uplifts of the earth's crust and vertical displacements of individual block structures that arose during faults occur. That is why the mountain ranges that rise above the surrounding territory have little dissection and steep slopes.

In the structure of folded-block structures, experts distinguish horst-like uplifts, when a separate block of the earth's crust rises above the surrounding territory to a considerable height. Prominent examples of guest-shaped mountains are the Vosges and Besalitsa, the Sierra Nevada, the Black Forest and the Harz. Another element of block mountains are graben-like depressions in the earth’s crust, when an individual block descends to a considerable depth relative to the surrounding area. Most often, grabens in the relief of block mountains are deep, steeply sloped, often.

A characteristic feature of folded-block orographic structures are flat peaks, extensive watersheds and wide flat-bottomed intermountain valleys that appeared as a result of faults in the earth's crust. These structures in the relief are formed with the loss of plasticity of ancient rocks, their inability to fold into folds, and the appearance of deep tectonic faults during the rejuvenation and revival of mountain systems.

Ural

The lithospheric folds lying at the base of the Urals formed within the Ural-Mongolian geosynclinal region into the Paleozoic Hercynian folding. Paleozoic structures in the Urals were formed in the Late Cambrian in a geosynclinal depression, which was gradually filled with continental crust and subsequently subjected to severe compression during strong volcanism.

Later, for a long time during the Mesozoic and Paleogene, processes of severe destruction and leveling of Hercynian structures took place in the Urals. Gradually, the mountain system turned into an ancient peneplain or heavily hilly hill. In the Neogene and Quaternary periods, active mountain-building processes and intensive rejuvenation of the territory began in the Urals. The old mountains rose again and split into separate blocks that rose and fell to different heights. The uneven uplift of lithospheric blocks led to large differences in the external shape and height of individual ridges.

Altai

A complex folded system within the Ural-Mongolian geosynclinal region was formed by highly dislocated and folded Precambrian and Paleozoic rocks during the Caledonian and Hercynian tectogenesis. In the subsequent geological periods that came after the Paleozoic, the mountainous country was severely destroyed and practically turned into a denudation plain or ancient peneplain.

In the Neogene and the subsequent Quaternary geological period, Altai, which had been heavily destroyed by that time, again underwent uplift and rejuvenation. With the general tectonic uplift of the territory, the ancient rocks of the mountainous country, which had lost their plasticity, split into huge blocks under the influence of deep tectonic faults. This process was accompanied by powerful continental glaciation and strong erosional dismemberment of the mountainous country.

Sayan Mountains

A typical example of folded block mountains are the Sayans, which formed partly within the Ural-Mongolian folded system during the ancient Baikal folding, partly during the Caledonian orogeny. After a long period of intense mountain building in the Sayan Mountains, a period of relative tectonic calm began, which continued into the Mesozoic and Paleogene. The mountains that rose were severely eroded and became a vast denudation plain, often called a peneplain by geologists.

But in the Neogene and later in the Quaternary period they again experienced the strongest rejuvenating tectonic movements. This process was accompanied by widespread outpouring of basalts and the formation of numerous volcanoes. The territory was split into separate tectonic blocks, constantly shifting relative to others. This process occurred with glaciation of high horst-shaped mountain peaks and strong erosional dissection of the entire territory.

Tien Shan

The powerful and geologically heterogeneous mountain system of the Tien Shan can serve as a remarkable example of an extensive block structure. It was formed on the territory of the Ural-Mongolian geosyncline with its northern part during the Caledonian orogeny, and its southern part in the Hercynian time. These parts, different in geology and geomorphology, are separated by a deep tectonic suture, which experts call the “Nikolaev line”.

After an active and prolonged mountain-building process, the Tien Shan was destroyed for a long time and turned into a strongly dissected denudation plain. At the end of the Paleogene in the Oligocene, a powerful mountain-building process began again throughout the Tien Shan, splitting the mountainous country into separate blocks and creating the modern high-mountain relief. Powerful tectonic movements led to the formation of stepped relief forms, the development of deep erosive river valleys and the appearance of continental glaciation.

Chersky Ridge

An example of the folded-block structure of a mountain system is the I. D. Chersky ridge. It was formed and rose significantly in Mesozoic times, when a powerful process of mountain building involved the addition of new tectonic structures to the northeastern part of the Siberian Platform. Then, for a long time, at the border of the Mesozoic and Cenozoic periods, the ridge was in a stable state, destroyed and actively peneplained.

During the era of the latest Alpine orogeny, the ridge underwent powerful rejuvenation and widespread uplift, and split into separate block blocks. Some blocks immediately rose into horst-shaped elevated mountain peaks, others sank into graben-shaped depressions of intermountain valleys. Therefore, the relief of the ridge is highly dissected; it alternates high and mid-mountain ridges covered with continental glaciation, extensive intermountain valleys, remnant stone ridges and stepped relief forms.

Stanovoy Ridge

In Transbaikalia, a typical example of a blocky structure of a territory is the Stanovoy Ridge. It was formed in the Precambrian from Archean and Early Proterozoic rocks, intruded by intrusions of ancient porphyrites and coarse-grained multi-colored granites in the south of the Siberian Platform. The oldest Archean and Proterozoic rocks on the planet are overlain here by deposits of the Late Jurassic and Early Cretaceous.

During the subsequent long period of denudation and erosional destruction, the territory of the ridge was leveled and strongly peneplained. In Pliocene-Quaternary geological time, the territory of the ridge rose again, split into separate tectonic blocks, and large ruptures, faults and young intrusions appeared here.

Appalachia

The Caledonian-Hercynian ancient folded-block structure of the Appalachian Mountains underwent strong mountain-building tectonic movements in the Paleozoic. During intense volcanic processes, the mountains rose into high peaks and were crushed into large folds. Subsequent Late Paleozoic long-term erosional denudation smoothed the mountain peaks, exposed ancient folds and greatly dissected the relief.

In the Meso-Cenozoic rejuvenating slow uplift of the Appalachian territory, the appearance of the modern mid-mountain relief gradually took shape, in which the so-called “relief inversion” is observed, where there is no clear correspondence of its forms to the most ancient folded structures. The amplitude of tectonic uplifts and the movement of blocks formed during deep faults varied in individual parts of the mountainous country.

The modern appearance of the mountains is very heterogeneous; high mountain ranges coexist here with vast and flat-bottomed intermountain valleys, erosional outcrop forms, deep gorges and foothill plateaus. In areas that have undergone continental glaciation, the topography here includes terminal moraine ridges, river valleys with a trough profile, high-mountain glacial lakes and many waterfalls on rivers flowing through hanging valleys.

Sierra Nevada

The formation of the American Californian high "snow-capped mountains" of the Sierra Nevada began in the Jurassic "Nevada Orogeny" typical of fold mountains by the movement of the Pacific tectonic plate under the North American plate. The deep magma of the melting oceanic plate created extensive granite intrusions in the cores of the future mountain range. Later, the Sierra Nevada Mountains began a period of prolonged relative calm and great destruction.

In the Oligocene and the subsequent Neogene, a new period of orogenesis began in the Sierra Nevada mountain system, which noticeably raised the territory, split it into blocks, carved V-shaped deep canyons with glaciers, exposed the famous local “batholiths” located on the intrusive bodies in the depths of the earth's crust. The Sierra Nevada is still growing, causing large earthquakes of up to magnitude 8.

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 the features of the geological structure of the area 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, while mountain rivers are rich in hydro resources and hydroelectric power stations are 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 and populated areas, you need to have a good knowledge of the topography of the surrounding area and the processes that create this topography.

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.

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 mountain areas

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 zones 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 (Fujiyama), tectonic (Altai mountains) and denudation, or erosion (Vilyuisky, Ilimsky).

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.

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 little smaller - 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 include 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.