Eastern Siberia: the grandeur and severity of nature. Relief and geological structure of northeastern Siberia

29.09.2019

Physiography Russia and USSR
Asian part: middle Asia and Kazakhstan, Siberia, Far East

North-Eastern Siberia

general characteristics

The vast territory lying east of the lower reaches of the Lena, north of the lower reaches of the Aldan and bounded on the east by the mountain ranges of the Pacific watershed, forms the country of North-Eastern Siberia. Its area (together with the islands of the Arctic Ocean that are part of the country) exceeds 1.5 million. km 2. Within North-Eastern Siberia are the eastern part of the Yakut Autonomous Soviet Socialist Republic and the western regions of the Magadan Region.

North-Eastern Siberia is located in high latitudes and is washed in the north by the seas of the Arctic Ocean. The extreme northern point of the mainland - Cape Svyatoy Nos - lies almost at 73° N. w. (and Henrietta Island in the De Longa archipelago - even at 77° N latitude); the southernmost areas in the Mai River basin reach 58° N. w. Approximately half of the country's territory lies north of the Arctic Circle.

North-Eastern Siberia is a country with varied and contrasting topography. Within its borders there are mountain ranges and plateaus, and in the north there are flat lowlands, stretching along the valleys of large rivers far to the south. This entire territory belongs to the Verkhoyansk-Chukotka region of the Mesozoic folding. The main processes of folding occurred here mainly in the second half of the Mesozoic, but the formation of the modern relief is mainly due to the latest tectonic movements.

The climate of the country is harsh, sharply continental. The amplitudes of absolute temperatures are in some places 100-105°; In winter there are frosts down to -60 -68°, and in summer the heat sometimes reaches 30-36°. There is little precipitation on the plains and low mountains of the country, and in the extreme northern regions the annual amount is as small as in the desert regions of Central Asia (100-150 mm). Permafrost is found everywhere, binding the soil to a depth of several hundred meters.

On the plains of North-Eastern Siberia, zonality is clearly expressed in the distribution of soils and vegetation cover: zones of arctic deserts (on islands), continental tundra and monotonous swampy larch woodlands are distinguished.

Mountain regions are characterized by altitudinal zonation. Sparse forests cover only the lower parts of the slopes of the ridges; their upper limit only in the south rises above 600-1000 m. Therefore, significant areas are occupied by mountain tundra and thickets of shrubs - alder, low-growing birch trees and dwarf cedar.

The first information about the nature of the Northeast was delivered in the middle of the 17th century. explorers Ivan Rebrov, Ivan Erastov and Mikhail Stadukhin. IN late XIX V. The expeditions of G. A. Maidel and I. D. Chersky conducted reconnaissance studies of mountainous areas, and the northern islands were studied by A. A. Bunge and E. V. Toll. However, information about the nature of the Northeast remained very incomplete until research in Soviet times.

Expeditions of S. V. Obruchev in 1926 and 1929-1930. significantly changed ideas even about the main features of the country’s orography: the Chersky ridge, more than 1000 in length, was discovered km, Yukaghir and Alazeya plateaus, the position of the sources of the Kolyma was clarified, etc. The discovery of large deposits of gold, and then other metals, necessitated geological research. As a result of the work of Yu. A. Bilibin, S. S. Smirnov, specialists from Dalstroy, the North-Eastern Geological Department and the Arctic Institute, the main features of the geological structure of the territory were clarified and many mineral deposits were discovered, the development of which led to the construction of workers' settlements, roads and the development of shipping on the rivers.

Currently, based on aerial photography materials, detailed topographic maps and the main geomorphological features of North-Eastern Siberia were clarified. New scientific data comes from studies of modern glaciation, climate, rivers and permafrost.

North-Eastern Siberia is a predominantly mountainous country; lowlands occupy slightly more than 20% of its area. The most important orographic elements are mountain systems of marginal ridges Verkhoyansk and Kolyma Highlands- form a convex arc to the south with a length of 4000 km. Inside it there are chains stretched parallel to the Verkhoyansk system Chersky ridge, Tas-Khayakhtakh ridges, Tas-Kystabyt (Sarycheva), Momsky and etc.

The mountains of the Verkhoyansk system are separated from the Chersky ridge by a low strip Jansky, Elginsky And Oymyakon plateau. Eastern are located Nerskoye Plateau and Upper Kolyma Highlands, and in the southeast the Verkhoyansk ridge is adjacent to Sette-Daban and Yudomo-May Highlands.

Most high mountains located in the south of the country. Their average height is 1500-2000 m, however, in the Verkhoyansk, Tas-Kystabyt, Suntar-Hayata and Chersky, many peaks rise above 2300-2800 m, and the highest of them is Mount Pobeda in the ridge Ulakhan-Chistai- reaches 3147 m. The mid-mountain relief here gives way to alpine peaks, steep rocky slopes, deep river valleys, in the upper reaches of which there are firn fields and glaciers.

In the northern half of the country, the mountain ranges are lower and many of them extend in a nearly meridional direction. Along with low ridges ( Kharaulakhsky, Selennyakhsky) there are flat ridge-like hills (ridge Polousny, Ulakhan-Sis) and plateaus (Alazeya, Yukagir). A wide strip of the coast of the Laptev Sea and East Siberian Sea occupied by the Yana-Indigirskaya lowland, from which the intermountain Middle Indigirskaya (Abyyskaya) and Kolyma lowlands extend far to the south along the valleys of the Indigirka, Alazeya and Kolyma. Most of the islands of the Arctic Ocean also have a predominantly flat topography.

Orographic scheme of North-Eastern Siberia

Geological structure and history of development

The territory of present-day North-Eastern Siberia in the Paleozoic and the first half of the Mesozoic was a section of the Verkhoyansk-Chukotka geosynclinal sea basin. This is evidenced by the large thickness of Paleozoic and Mesozoic sediments, in some places reaching 20-22 thousand. m, and the intense manifestation of tectonic movements that created the folded structures of the country in the second half of the Mesozoic. Particularly typical are the deposits of the so-called Verkhoyansk complex, the thickness of which reaches 12-15 thousand. m. It consists of Permian, Triassic and Jurassic sandstones and shales, usually intensely dislocated and intruded by young intrusions. In some areas, terrigenous rocks are interbedded with effusive rocks and tuffs.

The most ancient structural elements are the Kolyma and Omolon middle massifs. Their base is composed of Precambrian and Paleozoic sediments, and the Jurassic formations covering them, unlike other areas, consist of weakly dislocated carbonate rocks lying almost horizontally; Effusives also play a prominent role.

The remaining tectonic elements of the country are of younger age, predominantly Upper Jurassic (in the west) and Cretaceous (in the east). These include the Verkhoyansk folded zone and the Sette-Daban anticlinorium, the Yansk and Indigirka-Kolyma synclinal zones, as well as the Tas-Khayakhtakh and Mom anticlinoriums. The extreme northeastern regions are part of the Anyui-Chukotka anticline, which is separated from the middle massifs by the Oloi tectonic depression, filled with volcanogenic and terrigenous Jurassic deposits. Mesozoic folding movements, as a result of which these structures were formed, were accompanied by ruptures, outpourings of acidic and basic rocks, and intrusions, which are associated with various mineralization (gold, tin, molybdenum).

By the end of the Cretaceous, North-Eastern Siberia was an already consolidated territory, elevated above the neighboring regions. The processes of denudation of mountain ranges in the warm climate of the Upper Cretaceous and Paleogene led to leveling of the relief and the formation of flat leveling surfaces, the remains of which are preserved in many ridges.

The formation of modern mountainous relief is due to differentiated tectonic uplifts of the Neogene and Quaternary times, the amplitude of which reached 1000-2000 m. Particularly high ridges arose in the areas of the most intense uplifts. Their strike usually corresponds to the direction of Mesozoic structures, that is, they are inherited; however, some ridges of the Kolyma Highlands are distinguished by a sharp discrepancy between the strike of folded structures and modern mountain ranges. Areas of Cenozoic subsidence are currently occupied by lowlands and intermountain basins filled with layers of loose sediments.

During the Pliocene, the climate was warm and humid. On the slopes of the then low mountains there were coniferous-deciduous forests, which included oak, hornbeam, hazel, maple, and gray walnut. Among conifers, Californian forms predominated: Western American mountain pine (Pinus monticola), Wollosovich spruce (Picea wollosowiczii), representatives of the family Taxodiaceae.

Early Quaternary uplifts were accompanied by a noticeable cooling of the climate. The forests that covered the southern regions of the country at that time consisted mainly of dark coniferous species, similar to those currently found in the North American Cordilleras and the mountains of Japan. Glaciation began in the middle of the Quaternary. Large valley glaciers appeared on the mountain ranges that continued to rise, and firn fields formed on the plains, where, according to D. M. Kolosov, glaciation was embryonic in nature. In the far north - in the archipelago of the New Siberian Islands and on the coastal lowlands - in the second half of the Quaternary, the formation of permafrost and subsurface ice began, the thickness of which in the cliffs of the Arctic Ocean reaches 50-60 m.

Thus, the glaciation of the plains of the Northeast was passive. Most of the glaciers were inactive formations; they carried little loose material, and their exaration effect had little effect on the relief.

Erosion valley in the low-mountain massif of the Tuora-sis ridge. Photo by O. Egorov

Traces of mountain-valley glaciation are much better expressed in the marginal mountain ranges, where well-preserved forms of glacial gouging occur in the form of cirques and trough valleys, often crossing the watershed parts of the ridges. The length of valley glaciers descending in the Middle Quaternary from the western and southern slopes of the Verkhoyansk Range to neighboring areas of the Central Yakut Lowland reached 200-300 km. According to most researchers, there were three independent glaciations in the mountains of the North-East: the middle Quaternary (Tobychanskoe) and the upper Quaternary - Elga and Bokhapchinskoe.

The fossil flora of interglacial deposits indicates a progressive increase in the severity and continentality of the country's climate. Already after the first glaciation, Siberian coniferous trees, including the now dominant Daurian larch, appeared in the forest vegetation along with some North American species (for example, hemlock).

During the second interglacial epoch, mountain taiga prevailed, now typical of the more southern regions of Yakutia; The vegetation of the last glaciation, among which there were no dark coniferous trees, differed little in species composition from the modern one. According to A.P. Vaskovsky, the firn line and the forest boundary then dropped in the mountains by 400-500 m lower, and the northern limit of forest distribution was noticeably shifted to the south.

Main types of relief

The main types of relief of North-Eastern Siberia form several clearly defined geomorphological stages. The most important features of each of them are associated primarily with the hypsometric position, determined by the nature and intensity of recent tectonic movements. However, the country's location in high latitudes and its harsh, sharply continental climate determine the altitudinal limits of distribution of the corresponding types of mountainous relief that are different from those in more southern countries. Moreover, in their formation higher value acquire the processes of nivation, solifluction and frost weathering. Forms of permafrost relief formation also play a significant role here, and fresh traces of Quaternary glaciation are characteristic even of plateaus and areas with low-mountain relief.

In accordance with the morphogenetic characteristics within the country, the following types of relief are distinguished: accumulative plains, erosion-denudation plains, plateaus, low mountains, mid-mountain and high-mountain alpine relief.

Accumulative plains occupy areas of tectonic subsidence and accumulation of loose Quaternary sediments - alluvial, lake, marine and glacial. They are characterized by slightly rugged terrain and slight fluctuations in relative heights. Forms that owe their origin to permafrost processes, high ice content of loose sediments and the presence of thick underground ice are widespread here: thermokarst basins, frozen heave mounds, frost cracks and polygons, and on the sea coasts intensively collapsing high ice cliffs (for example, the famous Oyegossky Yar, more than 70 km).

Accumulative plains occupy vast areas of the Yana-Indigirsk, Middle Indigirsk and Kolyma lowlands, some islands of the seas of the Arctic Ocean ( Faddeevsky, Lyakhovskys, Bunge Land and etc.). Small areas of them are also found in depressions in the mountainous part of the country ( Momo-Selennyakh and Seymchan basins, Yanskoe and Elga plateaus).

Erosion-denudation plains are located at the foot of some northern ridges (Anyuysky, Momsky, Kharaulakhsky, Kular), on the peripheral sections of the Polousny ridge, the Ulakhan-Sis ridge, the Alazeysky and Yukagirsky plateaus, as well as on Kotelny Island. The height of their surface usually does not exceed 200 m, but near the slopes of some ridges it reaches 400-500 m.

Unlike accumulative plains, these plains are composed of bedrock of various ages; the cover of loose sediments is usually thin. Therefore, there are often gravelly placers, sections of narrow valleys with rocky slopes, low hills prepared by denudation processes, as well as medallion spots, solifluction terraces and other forms associated with the processes of permafrost relief formation.

Flat terrain most typically expressed in a wide strip separating the systems of the Verkhoyansk ridge and the Chersky ridge (Yanskoye, Elga, Oymyakon and Nerskoye plateaus). It is also characteristic of the Upper Kolyma Highlands, the Yukagir and Alazeya plateaus, significant areas of which are covered with Upper Mesozoic effusives, lying almost horizontally. However, most of the plateaus are composed of folded Mesozoic sediments and represent denudation leveling surfaces, currently located at an altitude of 400 to 1200-1300 m. In places, higher remnant massifs rise above their surface, typical, for example, of the upper reaches of the Adycha and especially the Upper Kolyma Highlands, where numerous granite batholiths appear in the form of high dome-shaped hills prepared by denudation. Many rivers in areas with flat mountain topography are mountainous in nature and flow through narrow rocky gorges.

Upper Kolyma Highlands. In the foreground is Jack London Lake. Photo by B. Vazhenin

Lowlands occupy areas that were subjected to uplifts of moderate amplitude in the Quaternary (300-500 m). They are located mainly along the outskirts of high ridges and are dissected by a dense network of deep (up to 200-300 m) river valleys. The low mountains of North-Eastern Siberia are characterized by typical relief forms caused by nival-solifluction and glacial processing, as well as an abundance of rocky placers and rocky peaks.

Mid-mountain terrain is especially characteristic of most of the massifs of the Verkhoyansk ridge system, the Yudomo-Maisky highland, the Chersky, Tas-Khayakhtakh and Momsky ridges. Significant areas are occupied by mid-mountain massifs also in the Kolyma Highlands and the Anyui Range. Modern mid-altitude mountains arose as a result of recent uplifts of denudation plains of planation surfaces, sections of which in some places have been preserved here to this day. Then, in Quaternary times, the mountains were subjected to vigorous erosion by deep river valleys.

The height of mid-mountain massifs is from 800-1000 to 2000-2200 m, and only at the bottom of deeply incised valleys do the elevations sometimes drop to 300-400 m. In the interfluve spaces, relatively flat relief forms predominate, and fluctuations in relative heights usually do not exceed 200-300 m. Forms created by Quaternary glaciers, as well as permafrost and solifluction processes, are widespread throughout. The development and preservation of these forms is facilitated by the harsh climate, since, unlike more southern mountainous countries, many mid-mountain massifs of the Northeast are located above the upper limit of tree vegetation, in a strip of mountain tundra.

River valleys are quite diverse. Most often these are deep, sometimes canyon-like gorges (the depth of the Indigirka valley reaches, for example, 1500 m). However, upper valleys usually have wide, flat bottoms and shallower slopes.

High alpine terrain associated with areas of the most intense Quaternary uplifts, located at an altitude of more than 2000-2200 m. These include the crests of the highest ridges (Suntar-Khayata, Tas-Khayakhtakh, Chersky Tas-Kystabyt ridge, Ulakhan-Chistai), as well as the central regions of the Verkhoyansk ridge. Due to the fact that the most significant role in the formation of the alpine relief was played by the activity of Quaternary and modern glaciers, it is characterized by deep dissection and large amplitudes of heights, the predominance of narrow rocky ridges, as well as cirques, cirques and other glacial landforms.

Climate

The harsh, sharply continental climate of North-Eastern Siberia is due to the fact that this country is located primarily within the Arctic and subarctic climatic zones, at a significant altitude above sea level and is isolated by mountain ranges from the influence of the Pacific seas.

The total solar radiation per year, even in the south, does not exceed 80 kcal/cm 2. Radiation values vary greatly by season: in December and January they are close to 0, in July they reach 12-16 kcal/cm 2. For seven to eight months (from September - October to April), the radiation balance of the earth's surface is negative, and in June and July it is 6-8 kcal/cm 2 .

Average annual temperatures are lower everywhere - 10°, and on the New Siberian Islands and in the highlands even - 15 -16°. Such low temperatures are due to the long duration of winter (six to eight months) and its extreme severity.

Already at the beginning of October, an area of high pressure of the Asian anticyclone begins to form over North-Eastern Siberia. Throughout the winter, very cold continental air dominates here, formed mainly as a result of the transformation of Arctic air masses coming from the north. In conditions of partly cloudy weather, very dry air and short duration of daylight hours, intense cooling of the earth's surface occurs. Therefore, the winter months are characterized by extremely low temperatures and no thaws. Average January temperatures everywhere, with the exception of the northern lowlands, are below -38, -40°. The most severe frosts occur in intermountain basins, where stagnation and especially intense cooling of the air occur. It is in such places that Verkhoyansk and Oymyakon are located, considered the pole of cold of the northern hemisphere. Average January temperatures here are -48 -50°; on some days frosts reach -60 -65° (the minimum temperature observed in Oymyakon was -69.8°).

Mountain areas are characterized by winter temperature inversions in the lower layer of air: the increase in temperature with height reaches in some places 1.5-2°C for every 100 m rise. For this reason, it is usually less cold on the slopes than at the bottom of intermountain basins. In some places this difference reaches 15-20°. Such inversions are typical, for example, for the upper reaches of the Indigirka River, where the average January temperature in the village of Agayakan, located at an altitude of 777 m, equal to -48°, and in the Suntar-Khayata mountains, at an altitude of 2063 m, rises to -29.5°.

Mountain ranges in the north of the Kolyma Highlands. Photo by O. Egorov

During the cold period of the year there is relatively little precipitation - from 30 to 100-150 mm, which is 15-25% of their annual amount. In intermountain depressions, the thickness of the snow cover usually does not exceed 25 (Verkhoyansk) - 30 cm(Oymyakon). It is approximately the same in the tundra zone, but on the mountain ranges of the southern half of the country the snow thickness reaches 50-100 cm. There are great differences between closed basins and the tops of mountain ranges in relation to the wind regime. In winter, very weak winds prevail in the basins and calm weather is often observed for several weeks in a row. During particularly severe frosts near populated areas and highways, such thick fogs that even during the day you have to turn on the lights in houses and turn on the headlights on cars. Unlike basins, peaks and passes are often strong (up to 35-50 m/sec) winds and snowstorms.

Spring is short and friendly everywhere, with little precipitation. The only spring month here is May (in the mountains - early June). At this time, the sun shines brightly, daily air temperatures rise above 0°, and the snow quickly melts. True, at night in early May there are still frosts down to -25, -30°, but by the end of the month the maximum air temperatures during the day sometimes reach 26-28°.

After a short spring comes a short but relatively warm summer. At this time, low pressure is established over the mainland of the country, and higher pressure over the northern seas. The Arctic front located near the northern coast separates the masses of warm continental air and colder air forming over the surface of the seas of the Arctic Ocean. Cyclones associated with this front often break through to the south, into the coastal plains, causing a noticeable drop in temperature and precipitation. Summer is warmest in the intermountain depressions of the upper reaches of the Yana, Indigirka and Kolyma. The average July temperature here is about 14-16°, on some days it rises to 32-35°, and the soil heats up to 40-50°. However, it can be cold at night and frost is possible in any summer month. Therefore, the duration of the frost-free period does not exceed 50-70 days, although the sum of positive average daily temperatures reaches 1200-1650° during the summer months. In the northern tundra regions and on mountain ranges that rise above the tree line, summers are cooler and the average July temperature is below 10-12°.

During the summer months the bulk of precipitation falls (65-75% of the annual amount). Most of them come with air masses arriving in July and August from the west, northwest and north. The greatest amount of precipitation falls on the Verkhoyansk and Chersky ridges, where at altitudes of 1000-2000 m during the summer months their amount reaches 400-600 mm; There are significantly fewer of them in areas of the flat tundra (150-200 mm). There is very little precipitation in closed intermountain basins (Verkhoyansk - 80 mm, Oymyakon - 100 mm, Seymchan - 115 mm), where, due to dry air, high temperatures and significant evaporation, plant growth occurs under conditions of a noticeable lack of moisture in the soil.

The first snowfalls are possible at the end of August. September and the first half of October can still be considered autumn months. In September there are often clear, warm and windless days, although frosts are common at night. At the end of September, average daily temperatures drop below 0°, frosts at night in the north reach -15 -18°, and snowstorms often occur.

Permafrost and glaciation

The harsh climate of the country causes intense freezing of rocks and the continuous spread of permafrost, which has a significant impact on the formation of landscapes. North-Eastern Siberia is distinguished by a very large thickness of permafrost, which in the northern and central regions in some places is more than 500 m, and in most mountainous areas - from 200 to 400 m. Very low temperatures of the rock mass are also characteristic. At the bottom of the layer of annual temperature fluctuations, located at a depth of 8-12 m, they rarely rise above -5 -8°, and within the coastal plain -9 -10°. The depth of the seasonal thawing horizon ranges from 0.2-0.5 m in the north up to 1-1.5 m on South.

In the lowlands and in intermountain depressions, underground ice is widespread - both syngenetic, formed simultaneously with the host rocks, and epigenetic, formed in rocks deposited earlier. Particularly characteristic of the country are syngenetic polygonal ice wedges, which form the largest accumulations of underground ice. In coastal lowlands their thickness reaches 40-50 m, and on Bolshoy Lyakhovsky Island - even 70-80 m. Some of the ice of this type can be considered “fossil”, since their formation began in the Middle Quaternary.

Underground ice has a significant impact on the formation of relief, river regime and conditions economic activity population. For example, the processes of ice melting are associated with the phenomena of soil flow and subsidence, as well as the formation of thermokarst basins.

The climatic conditions of the highest ranges of the country contribute to the formation of glaciers. In some places here at an altitude of more than 2000-2500 m falls up to 700-1000 mm/year precipitation, most of it in solid form. Snow melting occurs only during two summer months, which are also characterized by significant cloudiness, low temperatures (the average temperature in July is from 3 to 6-7°) and frequent night frosts. More than 650 glaciers with a total area of over 380 are known in the Suntar-Khayata, Chersky, Tas-Khayakhtakh, Kharaulakhsky and Orulgan ridges km 2. The centers of the most significant glaciation are located in the Suntar-Khayata ridge and in Buordakh massif. The snow line lies high here - at elevations from 2100 to 2600 m, which is explained by the prevalence of a fairly continental climate even at these altitudes.

Most glaciers occupy slopes of northern, northwestern and northeastern exposure. Among them, dwarves and hanging ones predominate. There are also firn glaciers and large snowfields. However, all the largest glaciers are valley glaciers; their tongues descend to a height of 1800-2100 m. The maximum length of these glaciers reaches 6-7 km, area - 20 km 2, and the ice power is 100-150 m. Almost all glaciers in the Northeast are now in the stage of retreat.

Rivers and lakes

North-Eastern Siberia is dissected by a network of many rivers flowing to the Laptev and East Siberian seas. The largest ones on them - Yana, Indigirka and Kolyma - flow almost in a meridional direction from south to north. Cutting through mountain ranges in narrow deep valleys and receiving numerous tributaries here, they, already in the form of high-water streams, reach the northern lowlands, where they acquire the character of lowland rivers.

In terms of their regime, most of the country's rivers belong to the East Siberian type. They feed mainly from melting snow cover in early summer and summer rains. Some role in the feeding of rivers is played by groundwater and the melting of “eternal” snow and glaciers in high mountains, as well as ice fields, the number of which, according to O. N. Tolstikhin, exceeds 2700, and their total area is 5762 km 2. More than 70% of the annual river flow occurs in three calendar summer months.

Freeze-up on the rivers of the tundra zone begins already at the end of September - beginning of October; mountain rivers freeze at the end of October. In winter, ice forms on many rivers, and small rivers freeze to the bottom. Even on such large rivers as the Yana, Indigirka, Alazeya and Kolyma, the flow during winter ranges from 1 to 5% of the year.

Ice drift begins in the last ten days of May - early June. At this time, most rivers experience their highest water levels. In some places (for example, in the lower reaches of the Yana), as a result of ice jams, the water sometimes rises by 15-16 m above winter level. During the flood period, rivers intensively erode their banks and clutter the riverbeds with tree trunks, forming numerous creases.

The largest river in North-Eastern Siberia - Kolyma(pool area - 643 thousand. km 2, length - 2129 km) - begins in the Upper Kolyma Highlands. Somewhat below the mouth of the Korkodon River, Kolyma enters the Kolyma Lowland; its valley here expands sharply, the fall and speed of the flow decrease, and the river gradually acquires a flat appearance. Near Nizhnekolymsk the width of the river reaches 2-3 km, and the average annual consumption is 3900 m 3 /sec(per year, Kolyma carries about 123 km 3 water). At the end of May, high spring floods begin, but by the end of June the river flows decrease. Summer rains cause a number of less significant floods and ensure a fairly high river level until the onset of freeze-up. The distribution of Kolyma flow in its lower reaches is as follows: in spring - 48%, in summer - 36%, in autumn - 11% and in winter - 5%.

The sources of the second major river - Indigirki(length - 1980 km, pool area - over 360 thousand. km 2) - located in the area of the Oymyakon Plateau. Crossing the Chersky ridge, it flows in the deep (until 1500-2000 m) and a narrow valley with almost vertical slopes; In the riverbed of the Indigirka there are often rapids. Near the village of Krest-Major, the river enters the plain of the Middle Indigirskaya Lowland, where it breaks into branches separated by sandy islands. Below the village of Chokurdakh a delta begins, the area of which is about 7700 km 2. The most prominent role in feeding the river is played by summer rains (78%), melted snow (17%), and in the upper reaches - glacial waters. The Indigirka annually brings about 57 km 3 water (its average annual consumption is 1800 m 3 /sec). The main flow (about 85%) occurs in summer and spring.

Lake of Dancing Graylings. Photo by B. Vazhenin

The western regions of the country are drained by the Yana (length - 1490 km 2, pool area - 238 thousand. km 2). Its sources - the Dulgalakh and Sartang rivers - flow down from the northern slope of the Verkhoyansk Range. After their confluence within the Yana Plateau, the river flows in a wide valley with well-developed terraces. In the middle part of the current, where the Yana crosses the spurs of mountain ranges, its valley narrows, and rapids appear in the riverbed. The lower reaches of the Yana are located in the coastal lowlands; When it flows into the Laptev Sea, the river forms a large delta (with an area of about 5200 km 2).

The Yana belongs to the rivers of the Far Eastern type and is characterized by long summer floods, which is due to the gradual melting of snow cover in the mountainous regions of its basin and the abundance of summer rains. The highest water levels are observed in July and August. The average annual consumption is 1000 m 3 /sec, and the annual flow is over 31 km 3, of which more than 80% occur in summer and spring. Yana's expenses vary from 15 m 3 /sec in winter up to 9000 m 3 /sec during the summer flood period.

Most of the lakes in North-Eastern Siberia are located on the northern plains, in the Indigirka and Alazeya basins. There are places here where the area of lakes is no less than the area of land separating them. The abundance of lakes, of which there are several tens of thousands, is due to the shallow terrain of the lowlands, difficult drainage conditions, and the widespread occurrence of permafrost. Most often, lakes occupy thermokarst basins or depressions in floodplains and on river islands. All of them are small in size, flat shores, shallow depths (up to 4-7 m). For seven to eight months, the lakes are covered with a thick ice cover; many of them freeze to the bottom in the middle of winter.

Vegetation and soils

In accordance with the harsh climatic conditions, landscapes of northern taiga sparse forests and tundra predominate in the territory of North-Eastern Siberia. Their distribution depends on the geographic latitude and altitude of the area above sea level.

In the far north, on the islands of the Arctic Ocean, arctic deserts with poor vegetation on primitive thin arctic soils. To the south, on the mainland coastal plain, is located tundra zone- arctic, hummock and shrub. Gleyed tundra soils, also thin, are formed here. Only south of 69-70° N. w. On the tundra plains of the Yana-Indigirka and Kolyma lowlands, the first groups of low-growing and oppressed Daurian larch appear in river valleys.

In the more southern regions, in the Middle Indigirsk and Kolyma lowlands, such copses emerge from the valleys in the interfluves, forming either larch “open spaces” or very monotonous sparse low-grade forests of the northern taiga appearance on gley-permafrost-taiga soils.

Rare larch forests They usually occupy the lower parts of mountain slopes. Under the sparse cover of low trees (up to 10 - 15 m) larches there are thickets of low-growing shrubs - birches (skinny - Betula exilis, shrubby - B. fruticosa and Middendorf - B. middendorffii), alder (Alnaster fruticosus), juniper (Juniperus sibirica), rhododendrons (Rhododendron parvifolium And R. adamsii), various willows (Salix xerophila, S. glauca, S. lanata)- or the soil is covered with an almost continuous carpet of mosses and bushy lichens - cladonia and cetraria. Under the sparse forests, peculiar mountain taiga-permafrost soils with an acidic reaction and without clearly defined genetic horizons (with the exception of humus) prevail. The features of these soils are associated with shallow permafrost, low temperatures, weak evaporation, and the development of permafrost phenomena in the soil. In summer, such soils experience temporary waterlogging, which causes weak aeration and the appearance of signs of gleying.

The mountains of North-Eastern Siberia are characterized by low vertical distribution limits of tree species. The upper limit of tree vegetation is located at an altitude of only 600-700 m, and in the extreme northern mountainous regions does not rise above 200-400 m. Only in the southernmost regions - in the upper reaches of the Yana and Indigirka, as well as in the Yudomo-Mai Highlands - do larch forests occasionally reach 1100-1400 m.

The forests that occupy the bottom of deep river valleys differ sharply from the monotonous open forests of mountain slopes. Valley forests develop on well-drained alluvial soils and consist mainly of sweet poplar (Populus suaveolens), whose height reaches 25 m, and the trunk thickness is 40-50 cm, and Chosenia (Chosenia macrolepis) having a straight high (up to 20 m), but thin (20-30 cm) trunk.

Above the mountain-taiga zone on the slopes there are dense thickets of dwarf cedar (Pinus pumila) or alder, gradually giving way to a zone mountain tundra, in which in some places there are small areas of sedge-grass alpine meadows. Tundra occupies approximately 30% of the area of mountainous regions.

The ridges of the highest massifs, where climatic conditions prevent the existence of even the most unpretentious plants, represent a lifeless cold desert and are covered with a continuous cloak of stone placers and screes, above which rocky peaks rise.

Animal world

The fauna of North-Eastern Siberia differs markedly from the fauna of neighboring regions of Siberia. To the east of the Lena, some animals common to the Siberian taiga disappear. There are no weasels, Siberian ibex, etc. Instead, mammals and birds appear in the mountains and plains that are close to those widespread in North America. Of the 45 species of mammals living in the mountains of the Kolyma basin, more than half are very closely related to the animals of Alaska. Such as, for example, the yellow-bellied lemming (Lemmus chrysogaster), light wolf, huge Kolyma elk (Alces americanus). Some American fish are found in rivers (for example, dallium - Dallia pectoralis, Chukuchan - Catostomus catostomus). The presence of North American animals in the fauna of the Northeast is explained by the fact that even in the middle of the Quaternary, land existed in the place of the present Bering Strait, which subsided only in the Upper Quaternary.

Other characteristic fauna of the country - the presence in its composition of steppe animals, not found anywhere else so far in the north. In the high-mountain rocky tundra you can often find the Verkhoyansk black-capped marmot - tarbagan (Marmota camtschatica), and in the dry glades of the mountain taiga zone - the long-tailed Kolyma ground squirrel (Citellus undulatus buxtoni). During the winter, which lasts at least seven to eight months, they sleep in their burrows built in the frozen ground. Closest relatives of the black-capped marmot, as well as bighorn sheep (Ovis nivicola) live in the mountains of Central Asia and Transbaikalia.

The study of the remains of fossil animals found in the Middle Quaternary deposits of North-Eastern Siberia shows that even then they lived here woolly rhinoceros and reindeer, musk ox and wolverine, tarbagan and arctic fox are animals of areas with a very continental climate, close to the modern climate of the highlands of Central Asia. According to zoogeographers, within the boundaries of ancient Beringia, which included the territory of the North-East of the USSR, the formation of modern taiga fauna began in Quaternary times. It was based on: 1) local species adapted to the cold climate; 2) immigrants from North America and 3) people from the mountains of Central Asia.

Among mammals in the mountains, various small rodents and shrews now predominate; there are more than 20 species here. Predators include the large Beringian bear, wolverine, East Siberian lynx, arctic fox, Beringian fox, and sable, weasel, ermine and East Siberian wolf. Among the birds, the rock capercaillie is typical (Tetrao urogalloides), hazel grouse (Tetrastes bonasia kolymensis), nutcracker (Nucifraga caryocatactes), tundra partridge (Lagopus mutus), Asian ash snail (Heteractitis incana). In summer, many waterfowl are found on the lakes: scoter (Oidemia fusca), bean goose (Anser fabalis) and etc.

Bighorn sheep. Photo by O. Egorov

Natural resources

Of the natural resources of North-Eastern Siberia, mineral resources are of greatest importance; Ore deposits associated with Mesozoic intrusive rocks are especially important.

In the mountains of the Yana-Kolyma region, which are part of the Pacific metallogenic belt, there are famous gold-bearing areas - Verkhneindigirsky, Allah-Yunsky and Yansky. A large tin-bearing province has been explored within the Yana-Indigirka interfluve. The largest tin deposits - Deputatskoye, Ege-Khaiskoye, Kesterskoye, Ilintas, etc. - are associated with Upper Jurassic and Cretaceous granite intrusions; a lot of tin is found here and in alluvial placers. Deposits of polymetals, tungsten, mercury, molybdenum, antimony, cobalt, arsenic, coal and various building materials are also significant. IN last years Prospects for the discovery of oil and gas fields have been identified in intermountain depressions and coastal lowlands.

Dredge on one of the rivers of the Upper Kolyma Highlands. Photo by K. Kosmachev

The large rivers of North-Eastern Siberia are navigable over a long distance. Total length currently in use waterways- about 6000 km(of which in the Kolyma basin - 3580 km, Yany - 1280 km, Indigirki - 1120 km). The most significant disadvantages of rivers as routes of communication are the short (only three months) navigation period, as well as the abundance of rapids and rifts. Hydropower resources here are also significant (Indigirka - 6 million. kW, Yana - 3 million. kW), but their use is difficult due to extremely large fluctuations in river water content across seasons, freezing in winter and the abundance of inland ice. The engineering and geological conditions for constructing structures on permafrost are also complex. Currently, the first Kolyma hydroelectric power station in the Northeast is being built in the upper reaches of the Kolyma.

Unlike other Siberian countries, the reserves of high-quality timber here are relatively small, since the forests are usually sparse and their productivity is low. The average supply of wood in the forests of even the most developed south-eastern regions is no more than 50-80 m 3 /ha.

The harsh climate also limits the possibilities for agricultural development. In the tundra zone, where the sum of average daily temperatures above 10° even in the south barely reaches 600°, only radishes, lettuce, spinach and onions can be grown. To the south, turnips, turnips, cabbage, and potatoes are also cultivated. In particularly favorable conditions, mainly on gentle slopes with southern exposure, early varieties of oats can be sown. Conditions for livestock farming are more favorable. Significant areas of flat and mountain tundra provide good reindeer pastures, and the meadows of river valleys serve as food sources for cattle and horses.

Before the Great October revolution North-Eastern Siberia was the most backward outskirts of Russia. The development of its natural resources and comprehensive development began only under the conditions of a socialist society. Widespread geological exploration work led to the discovery of ore deposits in the upper reaches of the Kolyma and Yana Rivers and the emergence of numerous mines and large working settlements. Good highways were built through the mountain ranges, and boats and steamships appeared on the large rivers of the region. The mining industry has now become the basis of the economy and provides the country with many valuable metals.

Agriculture has also achieved certain successes. State farms created in the upper reaches of the Indigirka and Kolyma satisfy part of the population's needs for fresh vegetables, milk and meat. In the Yakut collective farms of the northern and mountainous regions, reindeer husbandry, fur farming and fishing are developing, providing significant marketable products. Horse breeding is also developed in some mountainous areas.

1. Geographical location.

2. Geological structure and relief.

3. Climate.

4. Water and permafrost.

5. Soils, flora and fauna.

Geographical position

Northeast Siberia is located east of the Lena Valley and the lower reaches of the Aldan to the shores of the Bering Sea. In the north, the country is washed by the seas of the Arctic Ocean. The far east lies already in the western hemisphere, the 180th meridian crosses the country from Wrangel Island to the Gulf of Anadyr. The territory of this physical-geographical country is a giant peninsula of Eurasia with an area of more than 2.5 million km2. The Arctic Circle runs almost through the middle of the country. F.P. studied this territory. Wrangel, A.F. Middendorf, E.V. Toll, I.D. Chersky, S.V. Obruchev, K.A. Salishchev and others.

Geological structure and relief

Geologically, the entire country belongs to the Mesozoic folding. Mesozoic structures were formed in the Early Cretaceous as a result of the collision of the ancient Siberian platform with the microcontinents of Chukotka and Omolon. The Verkhoyansk anticline, the Yamalo-Kolyma synclinal zone, and the Chukotka anticlinorium are located here. The surface of these structures is covered with marine sandy-clayey sediments, and in some places there are coal-bearing strata. Mesozoic granitoids emerge in places. Mesozoic folded structures and ancient massifs are bordered on the south and east by the Okhotsk-Chukotka volcanogenic belt, which is associated with deposits of tin, tungsten, molybdenum, gold and other metals. The river valleys of the northeast are characterized by a large number (up to 10) river terraces. Traces of ancient glaciation are known in the mountains of the Northeast. The mountains are dominated by relict cryogenic-glacial denudation morphosculptures. The plains are covered with lacustrine-alluvial deposits and erosional landforms. In general, the country's topography is characterized by a combination of medium-high mountain systems, plateaus, highlands and lowlands. In the west of the country, the Verkhoyansk mountain system stretches for 1,500 thousand km, 100-250 km wide and from 500 m in the north to 2,400 m in the south. To the southeast of the Verkhoyansk Range lies the Suntar-Khayata Range. To the east of the Verkhoyansk Range is the Chersky Range, between which are the Yanskoye and Elga Plateaus, and to the south are the Oymyakon Uplands. The Chersky Ridge stretches for 1800 km and consists of three parts. To the east of it lies the Yukagir Plateau. Along the coast Sea of Okhotsk The Kolyma Plateau and the Dzhugdzhur ridge stretch. In the east of the country lie the Anadyr and Chukotka highlands, with an altitude of 1500-1800 m. The lowlands occupy a coastal position or in narrow “bays” enter the intermountain spaces to the south. The largest lowlands here are the Yana-Indigirskaya and Kolyma.

Climate

The climate is sharply continental, arctic in the north, temperate in the extreme south of the country, and the subarctic zone occupies most of the middle part. The structure of the relief facilitates the free penetration of Arctic air into the interior of the country. The influence of the Pacific Ocean is limited to the coastal mountain ranges. Winter is very harsh. North of the Arctic Circle in winter there is a polar night, and to the south of it the sun at noon is low above the horizon, daylight hours are short. The radiation balance from October to March is negative. In winter, the pressure is increased over the northeast of Siberia - a spur of the Asian maximum. Anticyclonic weather conditions prevail. Temperature inversions are characteristic. In the intermountain basins, the average temperature in winter is about -45˚C (in the area of Oymyakon almost -50˚C, and the absolute minimum is -71˚C). But for every 100 m you go up, it becomes 2˚C warmer. East of the Omolon River valley, winter temperatures increase, reaching -20˚C on the Chukotka Peninsula. Strong winds are typical on the coast. Snow cover lasts up to 8-9 months, its height varies from 30 cm in the north to 70 cm in the southeast (on the windward slopes of the mountains - up to 1.5 m). Summer is cool; in the mountains above 1000 meters there is no frost-free period. Average temperatures in summer range from +5˚C on the northern coast to +15˚C in the southern continental regions. Droughts can occur in summer, but there are also very wet periods. The annual precipitation varies from 200 mm in intermountain basins to 700 mm on the windward slopes of the mountains.

Water and permafrost.

Northeast Siberia is rich inland waters. Rivers belong to the basins of two oceans. The watershed runs along the Dzhugdzhur, Suntar-Khayata ridges, Kolyma and Chukotka highlands. Therefore, most of the territory belongs to the Arctic Ocean basin, and not to the Pacific Ocean. Largest rivers: Kolyma, Indigirka, Yana. The Kolyma River originates from the southern slopes of the Chersky ridge, its length is 2130 km, the basin area is 643 thousand km2. The main tributary is the Omolon River (1114 km). The diet is mixed, with snow playing a leading role. High water in early June, when the snow melts. The water rise is very high. The Indigirka originates on the slopes of the Suntar-Khayata ridge, flows through the Oymyakon Highlands and cuts through the Chersky ridge, receives a tributary - the Moma River and goes out onto the Yana-Indigirka lowland. The length of the river is 1726 km, the basin area is about 360 thousand km2. The food is mixed, dominated by snow, in summer rain and glaciers. The Yana River begins in the Verkhoyansk Mountains, its length is 880 km, the basin area is 238 thousand km2. The nutrition and regime are similar to the previous rivers, but the flood is less pronounced, since little snow falls in the river basin. All three rivers at their confluence form extensive deltas in which buried ice lies at a shallow depth from the surface. In winter, in some places the rivers freeze to the bottom. Ice deposits (taryns) often form on rivers, which fill the river floodplain and can persist all summer. There are many lakes and swamps in the lowlands. Most lakes are thermokarst. The lakes are under ice from October to June, the ice thickness reaches 2-3 meters. Mountain glaciation is developed in the mountains (Verkhoyansk Range, Chersky Range, Suntar-Khayata Range, Chukotka Plateau). The area of glaciation and snowfields is about 400 km2. The number of glaciers is more than 650. The snow line runs at an altitude of 2200-2500 m. Permafrost is widespread, its thickness is 300-600 m.

Soils, flora and fauna

Soil formation processes are suppressed by low temperatures, so soil formation proceeds slowly. The soil profile is thin, only 10-30 cm. In the north, in the lowlands, tundra-gley soils are common. Permafrost-taiga soils are developed in river valleys. In the mountains under forests, mountain podburs and gley-taiga permafrost soils predominate. On the Okhotsk coast the soils are podzolic.

The vegetation of North-East Siberia consists of representatives of three floras: Okhotsk-Kamchatka, East Siberian and Chukotka. In the far north, on the coastal lowlands, there is a tundra dominated by mosses, cotton grass, saxifrage, as well as lichens and creeping willow. To the south there is a strip of forest-tundra made up of alder, willow, birch, and low-growing larch shrubs. The entire rest of the country, with the exception of the upper mountain belt, is covered with larch forests. Poplars are found in the floodplains of the rivers; spruce and pine grow on the southern slopes. In the undergrowth of the taiga, dwarf cedar, alder, currant, and skinny birch are common; The ground cover consists of lingonberries, crowberries and lichens and mosses. On the slopes of the southern exposure of valleys and river terraces, areas of steppe vegetation of bluegrass, wheatgrass, steppe sedge, crowberry, cinquefoil, etc. (a relic of the tundra-steppe Beringian north) have been preserved. In the mountains, the forest boundary rises to 600-900 m, above which there is a shrub belt of dwarf cedar. Above 1000-1200 m there are mountain tundras.

The country's fauna consists of tundra and taiga forms. But there are mountain and steppe species. The Chukotka fauna is close to the fauna of Alaska. Mountain tundra species penetrate far to the south into the taiga, and steppe species penetrate north into the tundra. In the north live reindeer, yellow-bellied lemming, bighorn sheep, mountain hare, arctic fox, wolf, black-capped marmot, tundra partridge, pink gull, swans, auks, geese, ducks, falcons (balaban, gyrfalcon, peregrine falcon), etc. In the taiga Typical species are elk and reindeer, bear, wolf, fox, sable, weasel, wood lemming, voles, pika, capercaillie, hazel grouse, pike-perch, kuksha, nutcracker, hawks, golden eagle, etc.

The first information about the nature of the Northeast was delivered in the middle of the 17th century. explorers Ivan Rebrov, Ivan Erastov and Mikhail Stadukhin. At the end of the 19th century. The expeditions of G. A. Maidel and I. D. Chersky conducted reconnaissance studies of mountainous areas, and the northern islands were studied by A. A. Bunge and E. V. Toll. However, information about the nature of the Northeast remained very incomplete until research in Soviet times.

Currently, based on aerial survey materials, detailed topographic maps have been compiled and the main geomorphological features of North-Eastern Siberia have been clarified. New scientific data comes from studies of modern glaciation, climate, rivers and permafrost.

The highest mountains are located in the south of the country. Their average height is 1500-2000 m, however, in the Verkhoyansk, Tas-Kystabyt, Suntar-Hayata and Chersky, many peaks rise above 2300-2800 m, and the highest of them is Mount Pobeda in the ridge Ulakhan-Chistai- reaches 3147 m. The mid-mountain relief here gives way to alpine peaks, steep rocky slopes, deep river valleys, in the upper reaches of which there are firn fields and glaciers.

In the northern half of the country, the mountain ranges are lower and many of them extend in a nearly meridional direction. Along with low ridges ( Kharaulakhsky, Selennyakhsky) there are flat ridge-like hills (ridge Polousny, Ulakhan-Sis) and plateaus (Alazeya, Yukagir). A wide strip of the coast of the Laptev Sea and the East Siberian Sea is occupied by the Yana-Indigirskaya lowland, from which the intermountain Middle Indigirskaya (Abyyskaya) and Kolyma lowlands extend far to the south along the valleys of the Indigirka, Alazeya and Kolyma. Most of the islands of the Arctic Ocean also have a predominantly flat topography.

Orographic scheme of North-Eastern Siberia

Geological structure and history of development

Erosion valley in the low-mountain massif of the Tuora-sis ridge. Photo by O. Egorov

Main types of relief

The main types of relief of North-Eastern Siberia form several clearly defined geomorphological stages. The most important features of each of them are associated primarily with the hypsometric position, determined by the nature and intensity of recent tectonic movements. However, the country's location in high latitudes and its harsh, sharply continental climate determine the altitudinal limits of distribution of the corresponding types of mountainous relief that are different from those in more southern countries. In addition, the processes of nivation, solifluction and frost weathering become more important in their formation. Forms of permafrost relief formation also play a significant role here, and fresh traces of Quaternary glaciation are characteristic even of plateaus and areas with low-mountain relief.

Upper Kolyma Highlands. In the foreground is Jack London Lake. Photo by B. Vazhenin

Climate

Mountain ranges in the north of the Kolyma Highlands. Photo by O. Egorov

During the cold period of the year there is relatively little precipitation - from 30 to 100-150 mm, which is 15-25% of their annual amount. In intermountain depressions, the thickness of the snow cover usually does not exceed 25 (Verkhoyansk) - 30 cm(Oymyakon). It is approximately the same in the tundra zone, but on the mountain ranges of the southern half of the country the snow thickness reaches 50-100 cm. There are great differences between closed basins and the tops of mountain ranges in relation to the wind regime. In winter, very weak winds prevail in the basins and calm weather is often observed for several weeks in a row. During particularly severe frosts, such dense fogs form near populated areas and highways that even during the day you have to turn on the lights in houses and turn on the headlights on cars. Unlike basins, peaks and passes are often strong (up to 35-50 m/sec) winds and snowstorms.

Permafrost and glaciation

Underground ice has a significant impact on the formation of relief, river regime and conditions for economic activity of the population. For example, the processes of ice melting are associated with the phenomena of soil flow and subsidence, as well as the formation of thermokarst basins.

Rivers and lakes

Lake of Dancing Graylings. Photo by B. Vazhenin

Vegetation and soils

Animal world

Another characteristic feature of the country’s fauna is the presence of steppe animals, which are not found anywhere else so far in the north. In the high-mountain rocky tundra you can often find the Verkhoyansk black-capped marmot - tarbagan (Marmota camtschatica), and in the dry glades of the mountain taiga zone - the long-tailed Kolyma ground squirrel (Citellus undulatus buxtoni). During the winter, which lasts at least seven to eight months, they sleep in their burrows built in the frozen ground. Closest relatives of the black-capped marmot, as well as bighorn sheep (Ovis nivicola) live in the mountains of Central Asia and Transbaikalia.

The study of the remains of fossil animals found in the Middle Quaternary deposits of North-Eastern Siberia shows that even then the woolly rhinoceros and reindeer, musk ox and wolverine, tarbagan and arctic fox lived here - animals of areas with a very continental climate, close to the modern climate of the highlands of Central Asia . According to zoogeographers, within the boundaries of ancient Beringia, which included the territory of the North-East of the USSR, the formation of modern taiga fauna began in Quaternary times. It was based on: 1) local species adapted to the cold climate; 2) immigrants from North America and 3) people from the mountains of Central Asia.

Bighorn sheep. Photo by O. Egorov

Natural resources

Of the natural resources of North-Eastern Siberia, mineral resources are of greatest importance; Ore deposits associated with Mesozoic intrusive rocks are especially important.

In the mountains of the Yana-Kolyma region, which are part of the Pacific metallogenic belt, there are famous gold-bearing areas - Verkhneindigirsky, Allah-Yunsky and Yansky. A large tin-bearing province has been explored within the Yana-Indigirka interfluve. The largest tin deposits - Deputatskoye, Ege-Khaiskoye, Kesterskoye, Ilintas, etc. - are associated with Upper Jurassic and Cretaceous granite intrusions; a lot of tin is found here and in alluvial placers. Deposits of polymetals, tungsten, mercury, molybdenum, antimony, cobalt, arsenic, coal and various building materials are also significant. In recent years, prospects for the discovery of oil and gas fields have been identified in intermountain depressions and coastal lowlands.

Dredge on one of the rivers of the Upper Kolyma Highlands. Photo by K. Kosmachev

The large rivers of North-Eastern Siberia are navigable over a long distance. The total length of currently exploited waterways is about 6000 km(of which in the Kolyma basin - 3580 km, Yany - 1280 km, Indigirki - 1120 km). The most significant disadvantages of rivers as routes of communication are the short (only three months) navigation period, as well as the abundance of rapids and rifts. Hydropower resources here are also significant (Indigirka - 6 million. kW, Yana - 3 million. kW), but their use is difficult due to extremely large fluctuations in river water content across seasons, freezing in winter and the abundance of inland ice. The engineering and geological conditions for constructing structures on permafrost are also complex. Currently, the first Kolyma hydroelectric power station in the Northeast is being built in the upper reaches of the Kolyma.

Before the Great October Revolution, North-Eastern Siberia was the most backward outskirts of Russia. The development of its natural resources and comprehensive development began only under the conditions of a socialist society. Widespread geological exploration work led to the discovery of ore deposits in the upper reaches of the Kolyma and Yana Rivers and the emergence of numerous mines and large working settlements. Good highways were built through the mountain ranges, and boats and steamships appeared on the large rivers of the region. The mining industry has now become the basis of the economy and provides the country with many valuable metals.

General characteristics of North-Eastern Siberia

To the east of the lower reaches of the Lena lies a vast territory, bounded on the east by the mountain ranges of the Pacific watershed. This physical-geographical country was named North-Eastern Siberia. Including the islands of the Arctic Ocean, North-Eastern Siberia covers an area of more than $1.5 million sq. km. Within its borders are the eastern part of Yakutia and the western part of the Magadan region. North-Eastern Siberia is located in high latitudes and is washed by the waters of the Arctic Ocean and its seas.

Cape Svyatoy Nos is the extreme northern point. The southern regions are located in the Mai River basin. Almost half of the country’s territory is located north of the Arctic Circle, which is characterized by varied and contrasting topography. There are mountain ranges, plateaus, and flat lowlands along the valleys of large rivers. North-Eastern Siberia belongs to the Verkhoyansk-Chukchi Mesozoic folding, when the main folding processes took place. The modern relief was formed as a result of recent tectonic movements.

The climatic conditions of North-Eastern Siberia are severe, January frosts reach -$60$, -$68$ degrees. Summer temperature +$30$, +$36$ degrees. The temperature range in some places is $100$-$105$ degrees, there is little precipitation, about $100$-$150$ mm. Permafrost binds the soil to a depth of several hundred meters. In flat areas, the distribution of soils and vegetation is well expressed by zonality - on the islands there is a zone of arctic deserts, continental tundra and monotonous swampy larch woodlands. Altitudinal zonation is typical for mountainous regions.

Note 1

Explorers I. Rebrov, I. Erastov, M. Stadukhin brought the first information about the nature of North-Eastern Siberia. It was the middle of the 17th century. The Northern Islands were studied by A.A. Bunge and E.V. Toll, but the information was far from complete. Only in the $30$ years of the expedition of S.V. Obruchev changed ideas about the features of this physical and geographical country.

Despite the diversity of the relief, North-Eastern Siberia is mainly a mountainous country; lowlands occupy $20$% of the area. Here are located the mountain systems of the outlying ridges of the Verkhoyansk, Chersky, and Kolyma Highlands. In the south of North-Eastern Siberia there are the highest mountains, the average height of which reaches $1500$-$2000$ m. Many peaks of the Verkhoyansk ridge and the Chersky ridge rise above $2300$-$2800$ m. The peak is located in the Ulakhan-Chistai ridge - this is Mount Pobeda, whose height is $3147$ m.

Geological structure of North-East Siberia

In the Paleozoic era and at the beginning of the Mesozoic era, the territory of North-Eastern Siberia belonged to the Verkhoyansk-Chukotka geosynclinal sea basin. The main evidence of this is the thick Paleozoic-Mesozoic deposits, reaching $20-$22 thousand meters in places, and strong tectonic movements, which created folded structures in the second half of the Mesozoic. To the most ancient structural elements include the middle Kolyma and Omolon massifs. The remaining tectonic elements have a younger age - Upper Jurassic in the west, and Cretaceous in the east.

These elements include:

Verkhoyansk folded zone and Sette – Daban atiklinorium;
Yana and Indigirka-Kolyma synclinal zones;
Tas-Khayakhtakh and Momsky anticlinoriums.

By the end of the Cretaceous period, North-Eastern Siberia was a territory elevated above neighboring regions. The warm climate of this time and the denudation processes of mountain ranges leveled the relief and formed flat leveling surfaces. The modern mountainous relief was formed under the influence of tectonic uplifts in the Neogene and Quaternary periods. The amplitude of these uplifts reached $1000$-$2000$ m. Particularly high ridges rose in those areas where the uplifts were most intense. Cenozoic depressions are occupied by lowlands and intermountain basins with layers of loose sediments.

Around the middle of the Quaternary period, glaciation began, and large valley glaciers appeared on mountain ranges that continued to rise. According to D.M., glaciation had an embryonic character. Kolosov, on the plains, firn fields were formed here. The formation of permafrost begins in the second half of the Quaternary period in the archipelago of the New Siberian Islands and in the coastal lowlands. The thickness of permafrost and subsoil ice reaches $50$-$60$ m in the cliffs of the Arctic Ocean.

Note 2

The glaciation of the plains of North-Eastern Siberia was thus passive. A significant part of the glaciers were inactive formations that carried little loose material. The exaration effect of these glaciers had little effect on the relief.

Mountain-valley glaciation is better expressed; on the outskirts of mountain ranges there are well-preserved forms of glacial gouging - cirques, trough valleys. Mid-Quaternary valley glaciers reached a length of $200$-$300$ km. The mountains of North-Eastern Siberia, according to most experts, experienced three independent glaciations in the Middle Quaternary and Upper Quaternary times.

These include:

Tobychan glaciation;
Elga glaciation;
Bokhapcha glaciation.

The first glaciation led to the appearance of Siberian conifers, including Daurian larch. During the second interglacial era, mountain taiga was dominant. It is typical for the southern regions of Yakutia at present. The last glaciation had almost no effect on the species composition of modern vegetation. The northern limit of the forest at that time, according to A.P. Vaskovsky, was noticeably shifted to the south.

Relief of North-East Siberia

The relief of North-Eastern Siberia forms several well-defined geomorphological stages. Each tier is associated with a hypsometric position, which was determined by the nature and intensity of recent tectonic movements. The position in high latitudes and the sharp continentality of the climate determine other altitudinal limits for the distribution of the corresponding types of mountainous relief. In its formation, the processes of nivation, solifluction, and frost weathering become more important.

Within North-Eastern Siberia, in accordance with morphogenetic characteristics, the following are distinguished:

Accumulative plains;
Erosion-denudation plains;
Plateau;
Lowlands;
Mid-mountain and low-mountain alpine terrain.

Certain areas of tectonic subsidence occupy accumulative plains, characterized by slightly rugged terrain and slight fluctuations in relative height. Such forms are widespread that owe their formation to permafrost processes, high ice content of loose sediments and thick underground ice.

Among them are:

Thermokarst basins;
Permafrost heaving mounds;
Frost cracks and polygons;
High ice cliffs on the sea coasts.

Accumulative plains include the Yana-Indigirskaya, Sredne-Indigirskaya, and Kolyma lowlands.

At the foot of a number of ridges - Anyuisky, Momsky, Kharaulakhsky, Kular - formed erosion-denudation plains. The surface of the plains has a height of no more than $200$ m, but can reach $400$-$500$ m on the slopes of a number of ridges. The loose sediments here are thin and are composed mainly of bedrock of different ages. As a result, here you can find gravelly placers, narrow valleys with rocky slopes, low hills, medallion spots, and solifluction terraces.

Between the Verkhoyansk ridge and the Chersky ridge there is a pronounced plateau terrain– Yanskoye, Elginskoye, Oymyakonskoye, Nerskoye plateaus. Most of the plateaus are composed of Mesozoic deposits. Their modern height is from $400$ to $1300$ m.

Those areas that were subject to uplifts of moderate amplitude in the Quaternary are occupied low mountains, with a height of $300$-$500$ m. They occupy a marginal position and are dissected by a dense network of deep river valleys. Typical landforms for them are an abundance of rocky placers and rocky peaks.

Mid-mountain terrain mainly characteristic of most of the massifs of the Verkhoyansk Range system. Yudomo-Maysky upland, Chersky ridge, Tas-Khayakhtakh, Momsky. There are also mid-mountain massifs in the Kolyma Highlands and Anyui Range. Their height ranges from $800$-$2200$ m. The mid-mountain massifs of North-Eastern Siberia are located in a strip of mountain tundra, above the upper limit of tree vegetation.

High alpine terrain. These are the ridges of the highest mountain ranges - Suntar-Khayata, Ulakhan-Chistai, Tas-Khayakhtakh, etc. They are associated with the areas of the most intense uplifts of the Quaternary period. The height is more than $2000$-$2200$ m. In the formation of the alpine relief, a significant role is played by the activity of Quaternary and modern glaciers, therefore large amplitudes of heights, deep dissection, narrow rocky ridges, cirques, cirques and other glacial forms of relief will be characteristic.

1. Find on a physical map all the geographical features named in the paragraph.

Answer: the task is completed by the student independently

2. Name the features of the geological structure and relief of Eastern and North-Eastern Siberia.

Eastern and Northeastern Siberia have much in common in natural conditions, primarily climatic. However, the geological structure differs significantly, which is manifested in the topography of these territories. The stepped relief formed by the traps is a characteristic feature of Eastern Siberia.

The entire North-Eastern Siberia is an area of Mesozoic folding, and the relief of this region is predominantly mountainous. Glacial, frozen and erosive landforms are common in both regions. Thermokarst forms, numerous alasses, and thick aufeis on the rivers are developed.

3. Find the odd one out. The largest rivers of Eastern Siberia: a) Lena; b) Ob; c) Kolyma; d) Yenisei.

Answer: a, b

4. Establish a correspondence between minerals and their deposits.

1. Diamonds. A. Yana's pool.

2. Tin. B. Peaceful.

3. Brown coal. V. Norilsk.

4. Copper-nickel ores. G. Tunguska basin.

Answer: 1 – B; 2 – A; 3 – G; 4 – V.

5. Using the map of climatic zones and regions (see Appendix, p. 235), determine in which climatic zone are located: the Putorana plateau, the Anabar plateau, the sources and mouths of the Lena and Angara rivers, the cities of Dudinka, Norilsk, Yakutsk and Krasnoyarsk. Determine which of the named objects experiences the coldest weather. Explain your reasons.

Putorana plateau. The conditional southern border of the Putorana Plateau is the Arctic Circle, so the area is located in a zone of harsh, sharply continental climate, however, in individual lake valleys (for example, Lake Lama) there is a much milder microclimate, protected from the northern winds. Polar day in summer gradually gives way to polar night in winter. Spring, summer and autumn fit into three months: June, July, August, the rest of the time is winter with temperatures down to −40°C. In the warmest month (July) the air temperature reaches +16°C. Precipitation amounts to 500–800 mm, mainly in summer; snow cover is small in winter.

Anabar plateau. The territory belongs to the permafrost zone. The thickness of the permafrost under the Anabar Plateau reaches 1500 m. The plateau is located in the continental region of the subarctic zone and is characterized by a very low precipitation rate - about 250 mm per year. The average annual temperature is about –14ºС, the average January temperature is –34ºС with an absolute minimum of –60ºС, the period with negative average daily temperatures lasts about 260 days. Summer is rainy, July is often hot with maximum temperatures up to +38ºС.

The source of the Lena River. Temperate zone. The region has a sharply continental climate.

Mouth of the Lena River. Arctic belt.

The source of the Angara River. Temperate zone. The region has a sharply continental climate.

Mouth of the Angara River. Temperate zone. Continental climate region.

City of Dudinka. Located on the border of the subarctic and arctic zones. The climate of Dudinka is harsh subarctic. The average annual temperature is −9.4 °C. Winter is long and harsh, frosts can reach −50 °C or more. In winter, thaws are excluded. Frosty days about 280, heating season over 300 days. There have been positive average temperatures in Dudinka for only four months. Summer is short and cool, although individual years Temperatures of 30 °C or more are possible.

City of Norilsk. Of the listed objects, Norilsk is the coldest. Norilsk has an extremely harsh subarctic climate. This is one of the coldest cities in the world, significantly colder than Murmansk, which is located at almost the same latitude.

Winter is long and cold (average January temperature is about −28 °C), characteristic feature which is the frequent establishment of frosty weather combined with strong and very strong winds. The period of persistent frost lasts about 280 days a year; At the same time, there are more than 130 days with blizzards. From November to February, thaws are excluded.

The climatic winter lasts from the beginning of the second ten days of September to the first ten days of May. Snow cover lasts from 7.5 to 9 months a year.

Summer is short (from late June to late August), cool (+10.7 °C) and cloudy; climatic summer occurs only in some warm years.

The average annual air temperature in Norilsk is −9.8 °C, annual variation absolute temperatures− 96 degrees. The average annual relative humidity is about 76%. Norilsk is one of the five windiest settlements on the planet.

City of Yakutsk. Temperate zone. The region has a sharply continental climate. The climate is sharply continental, with little annual precipitation. Winter in Yakutsk is harsh, the average temperature in January is about −40 °C, sometimes frosts can even cross the 60-degree mark (the last time such frosts were observed was on January 2, 1951). Winter lasts from October to April inclusive, spring and autumn are very short. Thaws in the period from December to February have not been recorded in the entire history of meteorological observations. Also, there was a known case of snowfall in June.

In contrast to winter, summer, despite its changeable nature, is characterized by little precipitation and often intense heat. The scorching heat can reach almost +40 °C, which is very high for a relatively northern city.

Krasnoyarsk Temperate climate zone. Continental climate region. The climate of Krasnoyarsk is continental; softened by large water masses (Krasnoyarsk Reservoir), the Yenisei, which does not freeze in winter, and the surrounding mountains. Winters have little snow, with frequent thaws.

6. More than 60% of the territory of Siberia lies in the area of permafrost. Determine what economic problems are associated with permafrost. What benefits do you think the Siberian region would receive if there were no permafrost?

Permafrost significantly complicates the economic development of the territory. Particularly many difficulties arise during civil and road construction, as well as during the development of mineral deposits.

Even at the height of summer, in order to remove the soil, you need to first thaw the frozen soil, and heavily moistened thawed soil is usually a viscous and sticky “quicksand”. When constructing buildings, one has to take into account the threat of swelling of their foundations and their uneven subsidence, since during the operation of buildings the temperature regime of the permafrost is disturbed. Therefore, foundations and supports are buried in frozen soil, and houses are built on stilts.

When laying railways or highways, builders are forced to carry out a lot of additional and expensive work to avoid destruction of the road surface, and especially bridges, by ice.

In the absence of permafrost, Siberia would receive economic advantages:

Increasing the level of accessibility to resources;

Reducing the costs of constructing and maintaining infrastructure (buildings, structures, roads, etc.);

Influx of population, high level of economic activity.

8. In the form of a drawing, collage, poem, etc., reveal the image of Eastern or Northeastern Siberia (optional).

Examples of images of Eastern Siberia.

Valery Kravets.

"Eight months of winter,

Cloudberries instead of dates

You can go crazy here

And you can gain your mind.

If only you don't regret it

Summer is a gift from the sun,

If only you don't get sick,

From lack of tanning;

Lines of a wonderful snow book

If only you don't blame

For fate your palm

If you truly love

Cloudberries instead of dates!