A vast territory lying east of the lower reaches of the Lena, north of the lower reaches of the Aldan and bounded in the east by the mountains of the Pacific watershed, forms the country Northeast Siberia. Its area (together with the islands of the Arctic Ocean that make up the country) exceeds 1.5 million square kilometers. km 2. The eastern part of the Yakut Autonomous Soviet Socialist Republic and the western regions of the Magadan Region are located within North-Eastern Siberia.

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

North-Eastern Siberia is a country with a varied and contrasting relief. Within its limits are mountain ranges and plateaus, and in the north - flat lowlands, stretching along the valleys of large rivers far to the south. All this territory belongs to the Verkhoyansk-Chukotka region of the Mesozoic folding. The main processes of folding took place 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 places 100-105°; in winter there are frosts down to -60 -68 °, and in summer the heat sometimes reaches 30-36 °. On the plains and in the low mountains of the country, there is little precipitation, and in the extreme northern regions their annual amount is as small as in the desert regions of Central Asia (100-150 mm). Permafrost is found everywhere, holding down soils to a depth of several hundred meters.

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

Altitude zoning is typical for mountainous regions. 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, undersized birch and elfin 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. At the end of the XIX century. the expeditions of G. A. Maidel and I. D. Chersky conducted reconnaissance studies of mountainous regions, 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 the Soviet era.

Expeditions of S. V. Obruchev in 1926 and 1929-1930. significantly changed the ideas even about the main features of the country's orography: the Chersky Range was discovered with a length of more than 1000 km, the Yukagir 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 Administration 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 caused the construction of workers' settlements, roads and the development of shipping on the rivers.

At present, on the basis of aerial survey materials, detailed topographic maps have been compiled and the main geomorphological features of North-Eastern Siberia have been elucidated. New scientific data have been obtained as a result of studies of modern glaciation, climate, rivers and permafrost.

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

The mountains of the Verkhoyansk system are separated from the Chersky ridge by a lowered strip Jansky, Elginsky and Oymyakon plateau. East located Nerskoye Plateau and Upper Kolyma Highlands, and in the southeast, the Verkhoyansk ridge adjoins the ridge Sette-Daban and the Yudomo-Maya Highlands.

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 Khayata 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 is replaced by 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 stretch in a direction close to meridional. Along with low ridges ( Kharaulakhsky, Selennyakhsky) there are flat ridge-like hills (ridge half-moustache, Ulakhan-Sis) and plateaus (Alazeyskoye, Yukagirskoe). 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 Sredneindigirskaya (Abyiskaya) and Kolyma lowlands protrude 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 relief.

Orographic scheme of North-Eastern Siberia

Geological structure and history of development

The territory of the current North-Eastern Siberia in the Paleozoic and the first half of the Mesozoic was a site of the Verkhoyansk-Chukotka geosynclinal marine basin. This is evidenced by the large thickness of the Paleozoic and Mesozoic deposits, in some places reaching 20-22 thousand km. m, and intensive manifestation of tectonic movements that created the folded structures of the country in the second half of the Mesozoic. Especially typical are deposits of the so-called Verkhoyansk complex, whose thickness reaches 12-15 thousand tons. m. It includes Permian, Triassic, and Jurassic sandstones and shales, usually intensely dislocated and intruded by young intrusions. In some areas, terrigenous rocks are interbedded with effusives and tuffs.

The most ancient structural elements are the Kolyma and Omolon median massifs. Their base is composed of Precambrian and Paleozoic deposits, and the Jurassic suites covering them, unlike other areas, consist of weakly dislocated carbonate rocks, occurring 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-Dabansky anticlinorium, the Yana and Indigirsko-Kolyma synclinal zones, as well as the Tas-Khayakhtakhsky and Momsky anticlinoria. The extreme northeastern regions are part of the Anyui-Chukotka anticline, which is separated from the median massifs by the Oloy tectonic depression filled with volcanic and terrigenous Jurassic deposits. The Mesozoic fold-forming movements, as a result of which these structures were formed, were accompanied by ruptures, outpourings of acidic and basic rocks, intrusions, which are associated with various mineralization (gold, tin, molybdenum).

By the end of the Cretaceous, Northeastern Siberia was already a consolidated territory elevated above the neighboring regions. The processes of denudation of mountain ranges in the conditions of the warm climate of the Upper Cretaceous and Paleogene led to the leveling of the relief and the formation of flat surfaces of alignment, the remains of which have been preserved in many ranges.

The formation of modern mountain relief is due to differentiated tectonic uplifts of the Neogene and Quaternary time, the amplitude of which reached 1000-2000 m. In areas of the most intense uplifts, especially high ridges arose. Their strike usually corresponds to the direction of the Mesozoic structures, i.e., it is 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 strata of loose deposits.

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 prevailed: Western American mountain pine (Pinus monticola), Vollosovich spruce (Picea wollosowiczii), members 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 conifers, close to those currently found in the North American Cordillera and the mountains of Japan. From the middle of the Quaternary, glaciation began. Large valley glaciers appeared on the mountain ranges that continued to rise, and on the plains, where, according to D. M. Kolosov, glaciation was of an embryonic nature, firn fields formed. 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 ground 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 some 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

Significantly better are traces of mountain-valley glaciation in the outlying mountain ranges, where well-preserved forms of glacial exaration are found in the form of kars 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 Northeast: the Middle Quaternary (Tobychansky) and the Upper Quaternary - Elga and Bokhapcha.

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

During the second interglacial epoch, mountain taiga prevailed, which is now typical of the more southern regions of Yakutia; the vegetation of the time of the last glaciation, among which there were no dark coniferous trees, already differed little in species composition from the modern one. According to A.P. Vaskovsky, the firn line and the forest boundary then descended 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 relief types of North-Eastern Siberia form several distinct geomorphological tiers. The most important features of each of them are associated primarily with the hypsometric position, due to the nature and intensity of the latest tectonic movements. However, the location of the country in high latitudes and its harsh, sharply continental climate determine the altitudinal limits of the distribution of the corresponding types of mountain relief, which are different from those in more southern countries. Moreover, in their formation greater value acquire the processes of nivation, solifluction and frost weathering. The 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 morphogenetic features, the following types of relief are distinguished within the country: 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 deposits - alluvial, lacustrine, marine and glacial. They are characterized by slightly rugged topography and slight fluctuations in relative heights. Forms are widespread here, which owe their origin to permafrost processes, the large ice content of loose deposits and the presence of thick underground ice: thermokarst basins, permafrost heaving mounds, frost cracks and polygons, and on the sea coasts, high ice cliffs intensively collapsing (for example, the famous Oyegossky Yar, more than 70 km).

Accumulative plains occupy vast areas of the Yano-Indigirskaya, Sredneindigirskaya and Kolyma lowlands, some islands of the seas of the Arctic Ocean ( Faddeevsky, Lyakhovsky, Land Bunge and etc.). Small areas of them are also found in depressions in the mountainous part of the country ( Momo-Selennyakhskaya and Seimchanskaya depressions, Yanskoye and Elga plateaus).

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

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

Plateau relief it is most typically expressed in a wide strip separating the systems of the Verkhoyansk ridge and the Chersky ridge (Yanskoye, Elginskoye, Oymyakonskoye and Nerskoye plateaus). It is also characteristic of the Upper Kolyma Highlands, the Yukagir and Alazeya Plateaus, large areas of which are covered with Upper Mesozoic effusive rocks, which occur almost horizontally. However, most of the plateaus are composed of folded Mesozoic deposits and represent denudation leveling surfaces currently located at an altitude of 400 to 1200-1300 m. In places, higher remnant massifs also rise above their surface, typical, for example, for the upper reaches of the Adycha and especially the Upper Kolyma Upland, where numerous granite batholiths protrude in the form of high domed hills prepared by denudation. Many rivers in regions with a flat mountainous relief are mountainous in nature and flow in narrow rocky gorges.

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

lowlands occupy areas subjected in the Quaternary to uplifts of moderate amplitude (300-500 m). They are located mainly on 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 relief forms due to nival-solifluction and glacial processing, as well as an abundance of stony placers and rocky peaks.

Middle mountain relief is especially characteristic of most massifs of the Verkhoyansk Range, the Yudomo-Maya Highlands, the Chersky Range, Tas-Khayakhtakh and Momsky. Significant areas are occupied by mid-mountain massifs also in the Kolyma Uplands and the Anyui Range. Modern medium-altitude mountains arose as a result of the latest uplifts of denudation plains of leveling surfaces, parts of which have been preserved here in places to this day. Then, in the Quaternary, the mountains were vigorously eroded by deep river valleys.

The height of the mid-mountain massifs - from 800-1000 to 2000-2200 m, and only at the bottom of deeply incised valleys do the marks sometimes drop to 300-400 m. Relatively gentle relief forms predominate in the interfluve spaces, 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 everywhere. The development and preservation of these forms is facilitated by the harsh climate, since, unlike the more southern mountainous countries, many mid-mountain massifs of the Northeast are located above the upper limit of woody vegetation, in the 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, the upper reaches of the valleys usually have a wide flat bottom and less high slopes.

High Alpine relief 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, the 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 mainly within the Arctic and subarctic climatic zones, at a considerable height above sea level and is isolated by mountain ranges from the influences of the Pacific Ocean 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 everywhere below -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 in early October, an area of ​​increased 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 cloudy weather, high dryness of the air and a short duration of daylight hours, an intensive cooling of the earth's surface occurs. Therefore, the winter months are characterized by extremely low temperatures and the absence of thaws. The average January temperatures are everywhere, except for the northern lowlands, 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, which are considered the pole of cold in the northern hemisphere. Average January temperatures here are -48 -50°; on some days frosts reach -60 -65° (the minimum temperature observed in Oymyakon is -69.8°).

Mountain regions are characterized by winter temperature inversions in the lower layer of air: the temperature rise with altitude reaches in some places 1.5-2° for every 100 m lift. For this reason, it is usually less cold on the slopes than at the bottom of intermountain basins. In places this difference reaches 15-20°. Such inversions are typical, for example, for the upper reaches of the Indigirka, where the average January temperature in the village of Agayakan, located at an altitude of 777 m, equal to -48 °, and in the mountains of Suntar-Khayat, 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, relatively little precipitation falls - 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. Very weak winds prevail in the basins in winter, and calm weather is often observed for several weeks in a row. In especially severe frosts near settlements and highways, fogs are so dense here that even during the day it is necessary to turn on the lights in houses and turn on headlights in cars. Unlike the basins, peaks and passes are often strong (up to 35-50 m/s) winds and blizzards.

Spring everywhere is short, friendly, with little rainfall. The spring month here is only May (in the mountains - the beginning of June). At this time, the sun shines brightly, daily air temperatures rise above 0 °, the snow melts quickly. 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 over northern seas- higher. Located near the northern coast, the Arctic front separates the masses of warm continental air and colder air that forms over the surface of the seas of the Arctic Ocean. The cyclones associated with this front often break south, into the coastal plains, causing a noticeable drop in temperature and precipitation. The warmest summer is 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 warms up to 40-50°. However, it is cold at night, and frosts are 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 rising above the tree line, summers are cooler and the average temperature in July is below 10-12°C.

During the summer months, the main amount of precipitation falls (65-75% of the annual amount). Most of them come with air masses coming 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 sum reaches 400-600 mm; much less of them in areas of 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, the vegetation of plants occurs under conditions of a noticeable lack of moisture in the soil.

The first snowfalls are possible already 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 already common at night. At the end of September, the average daily temperatures drop below 0°, frosts at night in the north reach -15 -18°, blizzards 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. Northeastern Siberia is distinguished by a very large thickness of permafrost, which in places in the northern and central regions 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.

On 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. Especially typical for the country are syngenetic polygonal vein ice, which form the largest accumulations of underground ice. On the coastal lowlands, their thickness reaches 40-50 m, and on Bolshoi Lyakhovsky Island - even 70-80 m. Some ices of this type can be considered "fossils", since their formation began as early as the Middle Quaternary.

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

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

Most of the glaciers occupies the slopes of the northern, northwestern and northeastern exposure. Among them, car and hanging ones predominate. There are also firn glaciers and large snowfields. However, all the largest glaciers are valley ones; 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 retreat.

Rivers and lakes

Northeastern Siberia is dissected by a network of many rivers flowing to the Laptev and East Siberian seas. The largest 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, go to the northern lowlands, where they acquire the character of flat rivers.

In terms of their regime, most of the country's rivers belong to the East Siberian type. They feed mainly on melting snow cover in early summer and summer rains. Groundwater and the melting of "eternal" snow and glaciers in the high mountains, as well as icing, 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 falls on three calendar summer months.

Freezing on the rivers of the tundra zone begins already in late September - early 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 runoff during the winter is from 1 to 5% per annum.

Ice drift begins in the last decade of May - early June. At this time, most rivers have the 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 levels. During the flood period, the rivers intensively erode their banks and clutter up the channels with tree trunks, forming numerous creases.

The largest river in North-Eastern Siberia - Kolyma(basin area - 643 thousand sq. km 2 , length - 2129 km) - begins in the Upper Kolyma Highlands. Somewhat below the mouth of the Korkodon River, the Kolyma enters the Kolyma Lowland; its valley widens sharply here, the fall and speed of the current 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(for a year, Kolyma takes out to the East Siberian Sea about 123 km 3 water). At the end of May, a high spring flood begins, but by the end of June, the flow of the river decreases. Summer rains cause a number of less significant floods and provide a fairly high level of the river until the onset of freeze-up. The distribution of the Kolyma runoff in its lower reaches is as follows: in spring - 48%, in summer - 36%, in autumn - 11% and in winter - 5%.

Sources of the second major river - Indigirki(length - 1980 km, the basin area is over 360 thousand sq. km 2) - located in the area of ​​the Oymyakon Plateau. Crossing the Chersky Range, it flows in a deep (up to 1500-2000 m) and a narrow valley with almost steep slopes; rapids are often found here in the channel of the Indigirka. Near the village of Krest-Mayor, the river enters the plain of the Sredneindigirskaya lowland, where it breaks into branches separated by sandy islands. Below the village of Chokurdakh, the delta begins, the area of ​​\u200b\u200bwhich is about 7700 km 2. In the feeding of the river, the most prominent role is played by summer rains (78%), melted snow (17%), and in the upper reaches - glacial waters. Indigirka annually brings to the Laptev Sea about 57 km 3 water (its average annual consumption is 1800 m 3 /sec). The main runoff (about 85%) falls on summer and spring.

Lake of Dancing Graylings. Photo by B. Vazhenin

The western regions of the country are drained by Yana (length - 1490 km 2, basin area - 238 thousand sq. km 2). Its sources - the Dulgalakh and Sartang rivers - flow down from the northern slope of the Verkhoyansk Range. After their confluence within the Yan 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 the mountain ranges, its valley narrows, and rapids appear in the channel. The lower reaches of the Yana are located on the territory of the coastal lowland; at its confluence with 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 distinguished by a long summer flood, which is due to the gradual melting of the 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 stock for the year 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.

Most of the lakes of North-Eastern Siberia are located on the northern plains, in the basins of the Indigirka and Alazeya. Here there are places where the area of ​​the lakes is not less than the area of ​​the land separating them. The abundance of lakes, of which there are several tens of thousands, is due to the small ruggedness of the lowland relief, difficult runoff conditions, and the widespread permafrost. Most often, lakes occupy thermokarst basins or depressions in floodplains and on river islands. All of them are distinguished by their small size, flat banks, shallow depths (up to 4-7 m). For seven to eight months, the lakes are bound by a powerful ice cover; very many of them freeze to the bottom in the middle of winter.

Vegetation and soils

In accordance with the harsh climatic conditions in the territory of North-Eastern Siberia, landscapes of northern taiga sparse forests and tundra prevail. Their distribution depends on the geographical latitude and height 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, hummocky and shrubby. Here, gleyed tundra soils are formed, which are also thin. Only to the south of 69-70 ° N. sh. on the tundra plains of the Yano-Indigirka and Kolyma lowlands in the river valleys, the first groups of undersized and oppressed Dahurian larch appear.

In the more southern regions, on the Sredne-Indigirskaya and Kolyma lowlands, such copses emerge from the valleys to the interfluves, forming either larch “gap forests” or very monotonous sparse low-quality forests of the northern taiga type on gley-frozen-taiga soils.

Sparse larch forests usually occupy the lower parts of the mountain slopes. Under a sparse cover of low (up to 10 - 15 m) larches are thickets of undersized shrubs - birches (skinny - Betula exilis, shrub - 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. Sparse forests are dominated by peculiar mountain taiga-frozen soils with an acidic reaction and without clearly defined genetic horizons (with the exception of the humus one). The features of these soils are associated with shallow permafrost, low temperatures, low evaporation, and the development of permafrost phenomena in the soil. In summer, such soils experience temporary waterlogging, which causes their weak aeration and the appearance of signs of gleying.

The mountains of North-Eastern Siberia are characterized by low vertical limits of distribution of tree species. The upper limit of woody vegetation is located at a height of only 600-700 m, and in the extreme northern mountainous regions it 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-Maya Highlands - larch forests occasionally reach 1100-1400 m.

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

Above the mountain-taiga zone on the slopes are dense thickets of Siberian dwarf pine (Pinus pumila) or alder forest, gradually changing into a zone mountain tundra, in which in some places there are small areas of sedge-cereal alpine meadows. Tundra occupies approximately 30% of the area of ​​mountainous regions.

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

Animal world

The fauna of North-Eastern Siberia differs markedly from the fauna of the neighboring regions of Siberia. To the east of the Lena, some animals common to the Siberian taiga disappear. There is no Siberian weasel, Siberian ibex, etc. Instead of them, mammals and birds appear in the mountains and on the plains, close to those widely distributed 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, for example, are the yellow-bellied lemming (Lemmus chrysogaster), light wolf, huge Kolyma elk (Alces americanus). Some American fish are found in the 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, there was land on the site of the current Bering Strait, which sank only in the Upper Quaternary.

Another characteristic feature of the country's fauna is the presence of steppe animals in its composition, which are not found anywhere else in the far north. In the high-mountainous rocky tundra, one can often meet the Verkhoyansk black-capped marmot - tarbagan (Marmota camtschatica), and on 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 in the frozen ground. The closest relatives of the black-capped marmot, as well as the 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 regions 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 the Quaternary. It was based on: 1) local species adapted to the cold climate; 2) immigrants from North America; and 3) immigrants from the mountains of Central Asia.

Mammals in the mountains are now dominated by various small rodents and shrews; there are more than 20 species of them. Of the predators, the large Beringian bear, wolverine, East Siberian lynx, arctic fox, Beringian fox are characteristic, there are also sable, weasel, ermine and East Siberian wolf. Among the birds are typical stone capercaillie (Tetrao urogalloides), hazel grouse (Tetrastes bonasia kolymensis), nutcracker (Nucifraga caryocatactes), ptarmigan (Lagopus mutus), Asiatic ash snail (Heteractitis incana). In summer, many waterfowl are found on the lakes: scoter (Oidemia fusca), bean goose (Anser fabalis) and etc.

Snow sheep. Photo by O. Egorov

Natural resources

Of the natural wealth of North-Eastern Siberia, minerals are of the greatest importance; especially important are ore deposits associated with Mesozoic intrusive rocks.

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

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

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

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

The harsh climate also limits the possibilities for the development of agriculture. 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 especially favorable conditions, mainly on the gentle slopes of the southern exposure, it is possible to sow early varieties of oats. More favorable conditions for animal husbandry. Significant areas of the plain and mountain tundra are good reindeer pastures, and the meadows of the river valleys serve as a food base 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 all-round development began only in the conditions of a socialist society. Widespread exploration work led to the discovery of ore deposits in the upper reaches of the Kolyma and Yana and the emergence of numerous mines and large workers' settlements here. Good highways were laid through the mountain ranges, and boats and steamboats 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 made some progress. The state farms set up in the upper reaches of the Indigirka and Kolyma meet part of the population's needs for fresh vegetables, milk and meat. In the Yakut collective farms of the northern and mountainous regions, reindeer breeding, fur trade and fishing are developing, giving significant marketable products. Horse breeding is also developed in some mountainous regions.

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General characteristics of North-Eastern Siberia

To the east of the lower reaches of the Lena lies a vast territory, bounded in the east by the mountain ranges of the Pacific watershed. This physical and 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 is the eastern part of Yakutia and Western part Magadan region. North-Eastern Siberia is located in high latitudes and is washed by the waters of the Arctic Ocean and its seas.

Cape Svyatoi Nos is the northernmost point. The southern regions are in the Mai River basin. Almost half of the country's territory is located north of the Arctic Circle, which is characterized by a diverse and contrasting relief. There are mountain ranges, plateaus, flat lowlands along the valleys of large rivers. Northeastern Siberia belongs to the Verkhoyansk-Chukotka Mesozoic folding, when the main folding processes took place. The modern relief was formed as a result of the latest tectonic movements.

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

Remark 1

Explorers I. Rebrov, I. Erastov, M. Stadukhin delivered the first information about the nature of North-Eastern Siberia. It was the middle of the $XVII$ 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 the 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. The mountain systems of the outlying ranges of the Verkhoyansk, Chersky, Kolyma Uplands are located here. In the south of North-Eastern Siberia there are the highest mountains, the average height of which reaches $1500$-$2000$ m. whose height is $3147$ m.

Geological structure of the North-East of 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 marine 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. The most ancient structural elements include the median massifs Kolyma and Omolon. A younger age - Upper Jurassic in the west, and Cretaceous in the east - have other tectonic elements.

These elements include:

1. Verkhoyansk folded zone and Sette - Dabansky atiklinorium;
2. Yanskaya and Indigirsko-Kolyma synclinal zones;
3. Tas-Khayakhtakhsky and Momsky anticlinoria.

By the end of the Cretaceous, northeastern Siberia was a territory elevated above neighboring regions. The warm climate of that time, and the denudation processes of mountain ranges leveled the relief and formed flat surfaces of leveling. The modern mountain relief was formed under the influence of tectonic uplifts in the Neogene and Quaternary period. The amplitude of these uplifts reached $1000$-$2000m. Cenozoic subsidences are occupied by lowlands and intermountain basins with strata of loose deposits.

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

Remark 2

The glaciation of the plains of northeastern Siberia was thus passive. A significant part of the glaciers were slow-moving formations that carried little loose material. The exaration impact 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 exaration - cirques, trough valleys. Valley Middle Quaternary 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.

These include:

1. Tobychanskoe glaciation;
2. Elga glaciation;
3. Bokhapcha glaciation.

The first glaciation led to the appearance of Siberian conifers, including Dahurian larch. During the second interglacial epoch, mountain taiga prevailed. It is typical for the southern regions of Yakutia at the present time. 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.

The relief of the North-East of Siberia

The relief of North-Eastern Siberia forms several well-defined geomorphological tiers. Each stage is associated with a hypsometric position, which was determined by the nature and intensity of the latest tectonic movements. The position in high latitudes and the sharp continentality of the climate cause different altitudinal limits of the distribution of the corresponding types of mountainous relief. In its formation, the processes of nivation, solifluction, and frost weathering are of greater importance.

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

1. Accumulative plains;
2. Erosion-denudation plains;
3. Plateau;
4. low mountains;
5. Mid-mountain and low-mountain alpine relief.

Separate areas of tectonic subsidence occupy accumulative plains, characterized by a slightly rugged relief and small fluctuations in relative height. Such forms are spreading, which owe their formation to permafrost processes, large ice content of loose deposits and thick underground ice.

Among them are:

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

The accumulative plains include the Yano-Indigirskaya, Sredne-Indigirskaya, and Kolyma lowlands.

At the foot of a number of ridges - Anyuisky, Momsky, Kharaulakhsky, Kulara - formed erosion-denudation plains. The surface of the plains has a height of no more than $200$ m, but can reach $400$-$500$ m near the slopes of a number of ridges. Loose deposits here are thin and they are composed mainly of bedrock of different ages. As a result, gravel placers, narrow valleys with rocky slopes, low hills, spots-medallions, and solifluction terraces can be found here.

Between the Verkhoyansky 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 subjected 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 stony placers and rocky peaks.

Middle mountain relief is mainly characteristic of most of the massifs of the Verkhoyansk Range system. Yudomo-May Highland, Chersky Ridge, Tas-Khayakhtakh, Momsky. In the Kolyma Highlands and the Anyui Range, there are also mid-mountain massifs. Their height is from $800$-$2200$ m. The mid-mountain massifs of North-Eastern Siberia are located in the mountain tundra, above the upper limit of woody vegetation.

High Alpine relief. 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. The activity of Quaternary and modern glaciers plays a significant role in the formation of the Alpine relief, therefore large amplitudes of heights, deep dissection, narrow rocky ridges, cirques, cirques and other glacial landforms will be characteristic.

The vast territory of Eastern Siberia, which occupies a quarter of the area of ​​Russia, stretches from the shores of the Arctic Ocean to the border with Mongolia, from the left bank of the Yenisei to the watershed ranges of the Far East.

The natural features of Eastern Siberia are determined by its size, location in middle and high latitudes, general inclination of the territory towards the low coast of the Arctic Ocean, and greater distance from the Atlantic Ocean. In addition, the barrier of mountain ranges nearly wipes out the influence of the Pacific Ocean.

In contrast to the West Siberian Plate, where flat landforms predominate, the Siberian Platform is dominated by uplands and plateaus. The Siberian platform belongs to the ancient platforms of the Precambrian age, which also distinguishes it from the young (from a geological point of view) West Siberian plate. The region under consideration occupies the central and northern part of eastern Siberia and is located between the Yenisei in the west and the Lena and Aldan in the east. In the west, this territory borders on the West Siberian plate, in the southwest and south it is surrounded by mountain structures of the Yenisei ridge - the Eastern Sayan system and the Baikal-Patom highlands, from the east - by the Verkhoyansk ridge. In the north, the platform is limited by the Taimyr-Severozemelskaya folded area.

Within Eastern Siberia, flat and mountainous territories are clearly distinguished. The most significant plain is the Central Siberian Plateau. Deep river valleys and small uplifts break the uniformity of the surface of this territory. Rivers are the transport system of the landscape. Large and small rivers of Eastern Siberia form a dense network. Despite the insignificant amount of precipitation, the rivers are full of water. This is explained by a short warm period during which a rapid flood occurs. All the rivers of this territory belong to the basin of the Arctic Ocean. The Yenisei flows along the western edge of the Central Siberian Plateau. Its most abundant right tributary is the Angara, flowing from Baikal, which regulates the flow of the river, making it uniform throughout the year. This favors the use of Angara's water energy.

10 km from Baikal, high in the mountains, the Lena River is born. Having received large tributaries, especially Aldan and Vilyui, it turns into a large flat river. When it flows into the sea, the Lena forms a huge delta, the largest in Russia, consisting of more than a thousand islands. Other large rivers, the Indigirka and the Kolyma, also flow into the seas of the Arctic Ocean. Lakes in this area are located unevenly. There are especially many of them in the northern and eastern parts.

Lake Baikal. Photo: Sergey Vladimirov

Lake Baikal has unique features. It has no equal in the world in terms of age, depth, reserves and properties fresh water diversity and endemism of organic life.

A characteristic feature of Eastern Siberia is permafrost. In most of Eastern Siberia, under the top layer of soil there is soil bound by cold, which never thaws. They call it permafrost. A new science emerged - permafrost science, or geocryology. Among all frozen and frosty rocks, the most difficult to study are dispersed rocks, that is, rocks consisting of many different small particles (clay, sand, etc.). Inside such rocks there are many small voids or pores. The water in these pores is in the form of ice, steam and liquid water. In frozen soils, there is indeed unfrozen water. Only there is very little of it and it is distributed over the particles of the soil with a thin film. So thin that it is not visible even with a magnifying glass. The water contained in the frozen rock can migrate, move in the ground, and freeze, forming layers of ice (schlieren) in the rock with a thickness of hundredths of a millimeter or more. Geological processes that occur during the freezing or thawing of rocks, as well as the freezing of groundwater, are called cryogenic. There are many types of perennial heaving mounds. One of them is injectable. It usually occurs in areas of small lakes. In winter, such a lake on permafrost freezes to the bottom. However, under it there are always rocks saturated with water. They also freeze. These rocks are, as it were, in a frozen bag: ice is on top of them, and permafrost is on the bottom. The volume of such a bag gradually decreases as it freezes, and the water of the rocks begins to put pressure on the walls and roof that hold them back. Finally, succumbing to this pressure, the frozen roof bends in the weakest place, forming a helmet-shaped heaving mound. The Yakuts call such hillocks "bulgunnyakhs". Their size can reach a height of 30-60 meters, and at the base of 100-200 meters. Bulgunnyakhs are most often found in Central Yakutia, in the Arctic coastal lowlands of northeastern Siberia.

A serious danger is the process of solifluction, characteristic of the permafrost zone, which develops on the slopes of hills, hills and ravines. Solifluction is the flow of loose, highly waterlogged soil masses along slopes. The usual ground flow rate is 2-10 cm per year. However, with heavy rains or intense melting, landslides occur. Phenomena such as icing are associated with water in the permafrost zone. Frosts are called ice influxes, formed as a result of freezing of river or lake waters poured onto the surface. When the upper part of the rocks freezes, an increasing hydrostatic pressure (water pressure) arises in them. This happens because water, turning into ice, increases in volume, squeezing unfrozen water, and at the same time blocking all exits to the surface. Meanwhile, water presses on the ice crust until it finally breaks through and splashes to the surface. But, once in the wild, the water quickly freezes and covers the hole it has just made with ice. And everything starts over. The thickness of the icing sometimes reaches 7-10 m, and the area is several tens of square kilometers. Only here is the trouble: on such ice, you can’t mark the places of the next exits of under-ice water, and water breaks free sometimes with a real explosion. And it's dangerous.

All these phenomena are widespread in Eastern and Northeastern Siberia.

The ice zone of Eastern Siberia is characterized by the exceptional severity of nature. On Severnaya Zemlya and the New Siberian Islands, large areas are occupied by glaciers. In the areas free from glaciers, in the Arctic desert, there is a "seasonal" snow cover almost all year round. In the summer, when it descends, the processes of frosty weathering proceed vigorously, and large-clastic deposits melt on the surface of the earth. Mosses, lichens and some species of typically arctic flowering, mainly herbaceous, plants dominate in the sparse and poor vegetation cover of the Arctic desert. In the south of the zone there are squat shrubs - polar and arctic willows, etc. The arctic desert is inhabited by: arctic fox, polar bear, lemming, reindeer is rare. In the ice zone, fox, birds, marine animals, and wild reindeer are hunted. There is little population here, the fishing season is short, however, the number of many animals is declining and they need protection. In Russia, reserves have been organized to protect rare animals in the north of the Taimyr Peninsula and on Wrangel Island.

The North Siberian, Yano-Indigirskaya and Kolyma lowlands, the New Siberian Islands are tundras of flat plains. Rugged terrain, stony placers make the conditions for the existence of vegetation and wildlife, and hence the landscapes very diverse. Almost everywhere in the tundra zone, the ground is bound by ice. The first thing that catches your eye when you first see the tundra from the window of an airplane is the sparkling mirrors of many reservoirs. These are thermokarst lakes - they were formed as a result of thawing of permafrost and subsidence of the soil. The northern plains often resemble honeycombs. This is what polygonal tundras look like, which appear as a result of cracks in frozen ground. Life in the tundra adds its own patterns to those drawn by the permafrost, for example, lemming-hunting owls and skuas choose high ground to ambush and fertilize the soil with droppings. Tall grass grows here, and on a sunny summer day, a grid of bright green dots looks very picturesque from the air.

In the south, next to the forest, the tundra is similar to the northern taiga, only consisting of one undergrowth, without tall trees. The same green mosses, shrubs of lingonberries, blueberries, haddock, many dwarf birches, over which mushrooms sometimes rise - a kind of "birch trees". There are many mushrooms, they are clearly visible; thanks to the cool climate, they remain worm-free for a long time. For a mushroom picker, the tundra is a real paradise. The tundra is very beautiful twice a year. The first time is in August, when cloudberries ripen and the landscape changes color, first from green to red, and then to yellow. The second time - in September, when the leaves of dwarf birch and shrubs turn yellow and red. This is a golden autumn in miniature. For Eastern Siberia, the so-called tussock tundras are typical. Tussocks form sedges and cotton grass - a plant very characteristic of this zone. In English, cotton grass is called "cotton grass". Indeed, it is a herb with a fine white fiber tassel. Cotton grass also grows on the border of the tundra with the Arctic deserts. The peculiarity of the permafrost relief is also reflected in the pattern of the vegetation cover. So, for example, shrubs, mosses and sedges can grow along permafrost cracks, while the center of the "polygon" is covered only with algae or lichens, or completely bare. The tundra has a wide variety of insects. There are also ants here that build their dwellings from the hard leaves of shrubs or from the earth. Special mention must be made of mosquitoes and midges. In the tundra, the midge is able to turn life into a real hell. Reindeer climb the blown tops of the hills or descend to the coast: only there the wind saves them from blood-sucking insects. But there are very few of them in the tundra - these are amphibians and reptiles. The most primitive of reptiles, salamanders, are sometimes found in puddles, and representatives of only one species live in bushes - moored frogs. There are no snakes at all, the only reptile - a viviparous lizard - is found near the forest belt. And yet the tundra seems to be filled with life. This impression is created, first of all, by birds, of which there are a lot. And what kind of birds nest here! Large waterfowl - swans, geese, goose, ducks. They breed offspring in the tundra and then fly away in thousands of flocks to the south, to warm countries. The main animals of the tundra are the lemming, the arctic fox and the reindeer.

The forest zone occupies a vast territory of Central Siberia, up to about 60% of its entire area. The taiga of Central Siberia is characterized by a sharply continental climate and slight swampiness. The Central Siberian taiga is predominantly light coniferous taiga, consisting mainly of Naur larch and pine with a slight admixture of dark coniferous species - cedar, spruce and fir. The main reasons for the scarcity of the species composition of the eastern taiga are permafrost and a sharp continental climate. In connection with the elevated relief of the plateau, the flat taiga of Central Siberia merges in the south with the mountain taiga of the Sayan Mountains and the Baikal mountain country.

The Central Siberian taiga, when moving from north to south, is divided into three lanes. The northern strip of sparsely layered wetland forests goes south to the Arctic Circle. Larch swampy forests grow on gley-permafrost-taiga soils. The middle zone of the taiga occupies the basins of the Srednyaya and Nizhnyaya Tunguska and Vilyui rivers. In the basin of the Middle and Lower Tunguska, the taiga is more humid than in the Vilyui basin. The Central Siberian plateau is covered with spruce-cedar-larch taiga. The river valleys are dominated by spruce-cedar moss taiga with a slight admixture of larch. In the Vilyui basin, the Lena valley and the Lena-Aldan interfluve, taiga from Naur larch develops under conditions of insufficient moisture.

The southern strip of taiga occupies the basins of the Angara and the upper reaches of the Lena. In the western part, where the climate is somewhat warmer and wetter, the permafrost lies deep or is completely absent; here, on loamy and sandy soddy-podzolic soils, mainly pine grows. Larch dominates in the eastern part. In pine and deciduous forests, alder and Naur rhododendron grow in the undergrowth. The taiga of Central Siberia is a large raw material base for state procurements for the woodworking and wood-chemical industries. The main tree species are larch, pine, and cedar. Fur trade in the Central Siberian taiga occupies one of the first places among other regions.

The taiga has a more varied and rich animal world than tundra. Of the predators are common: brown bear, wolverine, fox, Siberian weasel, ermine, sable. Wolverine lives everywhere. Sable is rare and spread over stony placers in dense taiga. The lynx is the only animal from the cat family in the taiga. The habitat of the lynx is dense taiga forests. Of the artiodactyls in the taiga, elk and musk deer are common, and on the moss tundra of the Putorana Plateau there is a bighorn sheep. Maral and roe deer are common in the southern part of the Yenisei taiga. There is no continuous forest-steppe and steppe zone in Eastern Siberia. Only a few sections stand out.

The forest-steppe of Transbaikalia consists of steppe forb areas and pine forests or larch and birch copses with an undergrowth of Daurian rhododendron. The development of vegetation is significantly affected by cold and little snowy winters, dry and long springs, and short and rainy summers. Cold types of weather contribute to the development of pillow-shaped forms and curtains in plants. The vegetation of the steppes consists of feather grass, thin-legged, fescue and serpentine. The steppes and forest-steppes of Transbaikalia are the main agricultural regions. The steppes are used as pastures for livestock. Part of the territory is plowed under grain, garden and other crops.

In the mountains of North-Eastern Siberia, the altitudinal zonality of landscapes is clearly manifested. There are three high-altitude landscape zones on the Verkhoyansk Ridge. The first belt of north-taiga sparsely layered deciduous forests rises along the southern slopes up to 1200-1300 m, and up to 600-800 m along the northern slopes. Lichens predominate in the above ground cover; the shrub layer is formed by lingonberries, speedwells and wild rosemary. Along the river valleys, on sand and pebble deposits, gallery forests of fragrant poplar with an admixture of larch, birch, aspen and Siberian mountain ash stretch. Above the upper boundary of the larch forest, thickets of elfin cedar dominate with an admixture of shrubby alder with lichen-shrub cover.

The second belt is mountain-tundra. Its upper boundary should be drawn at the ends of the glaciers (1800-2100 m). This zone has severe climatic conditions: in a long winter, low temperatures prevail in combination with strong winds and blizzards. Climatic conditions contribute to the development of accumulative and wind-blown snowfields, avalanches, frost weathering, solifluction and icing (taryns). The icings are located below the ends of the glaciers at an altitude of 1100-1700 meters. The alpine type of relief prevails. The dominant type of tundra is lichen (cladonia and lecture), on gentle slopes - swampy tundra. The soils are mountain-tundra.

The third belt - perennial snows and glaciers; the snow limit lies at an altitude of 2250-2450 meters. Negative temperatures prevail all year round, but in winter frosts are much less than in neighboring valleys and plateaus. The average temperature of the warmest month at an altitude of 2800 meters is about +3? C. Strong winds prevail. The glaciers are surrounded by permafrost with very little seasonal thawing.

Approximately the same is observed in other mountains of North-Eastern Siberia: larch north-taiga rare-layer forests (on the flat bottoms of basins and valleys) and mountain larch forests (on the slopes of valleys and ridges) dominate in the lower altitudinal zone, higher - mountain tundra and bald mountains . In the south of the territory above larch trees thickets of dwarf pine and alder-cedar thickets are widespread.



Lesson 48 SPECIFICITY OF NATURE

Option 1

Option 2

1) Match: Natural Frontier

a) the Arctic Ocean;

b) Kazakh small hills. Part of the border

south;

north;

west;

East.

The foundation of the West Siberian platform, compared to the East European platform, was formed:

a) earlier;

b) at the same time;

c) later.

Territory Western Siberia has a general bias:

a) to the north

b) south.

The lower flat relief of Western Siberia is associated with:

a) with a greater depth of foundation;

b) with the features of new movements of the earth's crust.

The increase in the continentality of the climate of Western Siberia is manifested:

a) in colder winters;

in colder winters and more rainfall

1) Match:

Part of the border

a) west

b) east.

natural frontier

Ural mountains;

Kazakh small hills;

Yenisei.

The foundation of the West Siberian platform compared to the East European one:

a) younger

b) the same age;

c) more ancient.

The relief of Western Siberia is:

a) the predominance of hills;

b) alternation of uplands and lowlands;

c) the predominance of lowlands.

The thickness of the sedimentary rock cover on the West Siberian platform compared to the East European one:

a) less

b) the same;

c) more.

The main reason for the increase in the degree of continentality of the climate in Western Siberia compared to the Russian Plain is: a) the impact of the Arctic Ocean;

decreasing influence of the Atlantic; c) weakening of the western transference

1

6) Permafrost in Western Siberia compared to the Russian Plain has:

a) wider distribution;

b) less widespread.

In Western Siberia, there is the following range of natural zones:

a) from arctic deserts to forest-steppes;

b) from tundra to steppes;

c) from forest-tundra to semi-deserts.

The predominant soil type in Western Siberia:

a) tundra-gley;

b) podzolic;

c) sod-podzolic

6) The boundary of permafrost distribution in Western Siberia is shifted compared to the East European Plain:

a) to the west

b) to the north;

c) south.

The distribution of natural zones on the territory of Western Siberia is a manifestation of:

a) latitudinal zonality;

b) altitudinal zonation.

The main types of natural resources of Western Siberia are:

a) oil and gas;

b) oil, gas and forest resources;

c) oil, gas, forest and soil resources

Tasks: to form knowledge about the peculiarities of the geographical position of Eastern and North-Eastern Siberia as a factor that determines the natural features of this territory; to develop the ability of students to independently establish the relationship of the geological structure with the relief and minerals; to systematize students' knowledge about the reasons for the formation of a sharply continental climate in Eastern and North-Eastern Siberia; to consolidate the ability to independently determine quantitative climatic indicators for various regions of Siberia and to acquaint them with the peculiarities of the climate; to study the features of the regime and nature of the flow of rivers and their connection with the relief and climate of Siberia.

1. Testing knowledge and skills on the topic "West Siberian Plain".

It is advisable to check the level of assimilation of knowledge and skills in a compacted form. Factual knowledge can be checked frontally in the form of a small test by options

Answers:

Option I - 1 - 1 c, 2a, 2 - c; 3 - a; 4 - b; 5 - a; 6 - a; 7 - b; 8 - c.

II option - 1 - 1a, 2c; 2 - a; 3 - in; 4 - in; 5 - b, c; 6 - in; 7 - a; 8 - b.

II. Getting new knowledge.

The study of this topic is complicated by the lack of study time. In preparing for the lessons, the teacher first of all selects the main thing, prepares tasks for students to work independently. Ways to organize cognitive activity can be varied: solving cognitive problems, heuristic conversation, a seminar on the problems of rational use natural conditions and resources, a game, a competition for the characteristics of individual geographical objects, crossword puzzles, small travel games.

The teacher distributes teaching time at his own discretion. Traditionally, in the first lesson, natural components are considered, in the second, natural complexes are studied.

When studying the nature of Central and North-Eastern Siberia, it is important to draw students' attention to understanding the features of nature, the manifestation of relationships, the characteristic features and integrity of landscapes. To do this, it is advisable to use a heuristic conversation with practical and independent work of students with maps, a textbook, and visual aids.

1. Students characterize the geographic location of the large natural area "Eastern and North-Eastern Siberia" on their own, using the physical map of Russia and the map of large natural areas located in the atlas.

Questions and tasks:

1) What are the boundaries of Eastern and North-Eastern Siberia natural territory in the north, west, south and east.

2) Specify which landforms are part of Eastern and North-Eastern Siberia.

3) Describe geographical position this large natural area.

4) What is the peculiarity of its geographical position compared to the West Siberian Plain?

5) How does the Arctic Ocean affect the natural conditions of Eastern and North-Eastern Siberia?

6) How does the Atlantic Ocean affect the natural conditions of this part of Siberia?

7) Explain why the Pacific Ocean, relatively close to Eastern Siberia, has practically no effect on its natural conditions.

8) Make a generalizing conclusion about how the geographical location of Eastern and North-Eastern Siberia affects the natural conditions of the territory.

Summarizing the students' answers, the teacher talks about the size of this natural area and the reasons for close attention to the study of the natural conditions and resources of Eastern and North-Eastern Siberia at the present time.

1) According to the tectonic map, establish on which geological structures East and North-Eastern Siberia is located.

2) What landforms are located in this area?

3) What is the peculiarity of the surface structure?

When characterizing the relief, students pay attention to the fact that the territory of the region is much higher than neighboring Western Siberia. Elevations rise to 500 m, plateaus - up to 1000 m, highlands - up to 1500 - 2000 m. The highest point is Pobeda peak in the ridge. Chersky with a height of 3147 m. Thus, a conclusion is formed about the diversity of the relief of Eastern and North-Eastern Siberia.

When analyzing a tectonic map, students are convinced that the Siberian Platform lies at the base of the Central Siberian Plateau. How to explain the structure of the surface and the differences in the relief on the plateau? If the students have difficulties, the teacher himself answers this question.

Teacher. The reason for the differences in the relief on the Central Siberian Plateau lies in the unevenness of the foundation of the platform. Where the foundation comes to the surface, the Anabar Plateau was formed. Separate blocks of the foundation are omitted, in the relief this is expressed by the lowlands - the North Siberian and Central Yakut. A feature of the relief of the region is the presence of volcanic plateaus. In the Mesozoic, a huge amount of lava poured out through cracks in the platform, which, solidifying, formed continuous covers. A lot of lava solidified among sedimentary rocks. Subsequently, loose rocks were destroyed, and igneous ones remained, forming a stepped relief - traps. Another feature of the relief is the abundance of kurums. They are formed as a result of intense frost weathering.

4) From the maps, determine which minerals are mined on the Central Siberian Plateau. Explain why minerals of both sedimentary and igneous origin are mined on the plateau.

5) What minerals are the mountains of Mesozoic folding rich in and explain why there are a lot of various minerals in these mountains?

The teacher only explains that deposits of ore minerals are associated with traps, and iron ore and diamonds are associated with kimberlite pipes.

Teacher. Interestingly, the discovery of diamonds on the territory of the Siberian platform is an example of a brilliant confirmation of a scientific forecast. Such a forecast was made by V.S. Sobolev in 1937 based on a comparison of the geology of the Siberian and African platforms. The search for diamonds began in 1940, and in 1947 the first diamonds were found in placers, and in 1954 the first kimberlite pipes were found. A feature of the development of the mountains of North-Eastern Siberia is the formation of placer gold deposits. Placers are located in terraces, valleys and riverbeds. They were formed due to the erosion of granitic igneous rocks. Gold is a common companion of deposits of tin, cobalt, arsenic and other ores.

3. The climatic features of Eastern and North-Eastern Siberia are studied using atlas maps. It is important that schoolchildren independently work out the factual material characterizing the features of the climate, and, relying on it, draw generalizing conclusions about the typical features of the climate of this territory. The teacher organizes the work using the following tasks:

1) For the cities of Norilsk, Irkutsk and Oymyakon, determine the average temperatures in July, January and the annual temperature range; calculate the maximum annual temperature amplitude; calculate the moisture coefficient; identify the types of air masses.

2) Based on the obtained climatic data, draw a conclusion about the typical features of the climate of Eastern and North-Eastern Siberia.

Students write down in a notebook the main features of a sharply continental climate:

large fluctuations in daily, monthly and annual temperatures;

low amount of precipitation;

great evaporation.

Oymyakon and Verkhoyansk are the cold poles of the northern hemisphere, where the average January temperature drops to -50 ° C, and the absolute minimum temperature is about -70 ° C.

3) What are the reasons that explain why on the vast territory of Eastern and North-Eastern Siberia, stretching from north to south for 2000 km and from west to east for more than 3000 km, a sharply continental climate has formed with very cold winters, the warmest summers and a small amount of precipitation compared with other regions of Russia at the same latitudes.

Complete the assignment in writing.

Climate-forming factors:

northern geographic location;

influence of the Arctic;

distance from the Atlantic Ocean;

significant absolute heights of the terrain;

strong cooling of the mainland in winter time, which contributes to the development of stable anticyclones.

4) Remember what kind of weather winter anticyclones are characterized by and what atmospheric processes are observed in them.

Teacher's explanations: The Siberian anticyclone is characterized by stable, very cold, clear, sunny, slightly cloudy, dry and calm weather in winter. The lowest air temperatures are observed in the interior regions of North-Eastern Siberia, in poorly ventilated intermountain basins, where cold air stagnates and cools down especially strongly. It is in such places that Verkhoyansk and Oymyakon are located. These intermontane basins are characterized by winter temperature inversions in the lower air layer. During inversions, an increase in air temperature with height by 2 degrees for every 100 m is observed. For this reason, it is less cold on the slopes of the mountains than in the basins, sometimes this difference is 15-20 °.

4. Describing permafrost, the teacher draws students' attention to cause-and-effect relationships in nature.

In one case, permafrost is a consequence of climatic conditions, a sharp continental climate. It is almost ubiquitous throughout the region. The thickness of the permafrost layer in many places exceeds hundreds of meters (600 m in the Vilyui basin). In summer, the upper horizon of the permafrost thaws in the north by 20-40 cm, and in the south - by several meters.

In another case, permafrost is the cause that determines the development of other components and natural phenomena. It causes swamping of the plains, has a great influence on the regime of inland waters, cools the soil and thus inhibits the soil-forming process. On permafrost, plants can grow only with a superficial root system, for example, larch.

5. In the final part of the lesson, in order to consolidate the students' skills to establish and characterize the connections of rivers with other components of nature, tasks of a partially search character are offered:

Explain why R. The Yenisei is the most abundant river in Russia, despite the fact that little precipitation falls in the basin.

Explain why there are many rapids and waterfalls on the Yenisei, Angara, Vilyui, but none on the Lena.

It is known that winters in Eastern Siberia are characterized by little snow, and in many places the snow is completely swept away. However, in spring, a high rise in water is observed on the rivers of Siberia, which reaches 10 m on the Lena, and even 20–25 m on the Lower Tunguska. Explain this natural phenomenon.

III. Summing up the lesson.

Homework: § 37, 38, put the nomenclature on the contour map.

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covers an area of ​​about 7 million square kilometers. Eastern Siberia is the name given to the region located east of the Yenisei, up to the mountains that form the watershed between the Pacific and Arctic oceans. The largest area is occupied by the Central Siberian Plateau. In the north and east of Eastern Siberia there are two lowlands: North Siberian and Central Yakut. In the south and west of Eastern Siberia there are mountains - Transbaikalia, the Yenisei Ridge. The length of this geographical area from north to south is about 3 thousand kilometers. In the south of Eastern Siberia, there is a border with Mongolia and China, and the northernmost point is Cape Chelyuskin.

The relief of Eastern Siberia is significantly elevated above sea level. The Central Siberian Plateau - the main part of the East, was formed on the ancient Siberian platform. Its average height above sea level is 500-700 meters, and the highest areas located in the north-west reach 1500-1700 meters - the Vilyui plateau and the interfluve of the Lena River. Most of the rivers flowing in Eastern Siberia are high-water, fast-flowing and flow in deep valleys.

At the base of the Siberian platform lies the Archean-Proterozoic folded crystalline basement, on which is located a sedimentary cover of a later period with a thickness of 10-12 kilometers. In the north and southwest, the basement rocks protrude to the surface - the Anabar massif, the Aldan shield, the Baikal uplift. The total thickness of the earth's crust is 25-30 kilometers, and in some places reaches 40-45 kilometers.

The foundation of the Siberian platform consists of various types of rocks - schists, marbles, charnockites and others. The age of some of these deposits Eastern Siberia, according to experts, about 3-4 billion years. The deposits that make up the sedimentary cover are not so ancient and date back to the time of the emergence of mankind. The Paleozoic deposits of the cover penetrate igneous rocks, which were formed during numerous eruptions and solidified in sedimentary rocks. These igneous rocks are called traps. As a result of the alternation of traps with more fragile sedimentary rocks, a stepped relief was formed - a characteristic feature of the Central Siberian plateau. Most often, traps are found within the Tunguska depression.

During the Mesozoic period, most of Central Siberia experienced uplift. It is no coincidence that the highest point of the Central Siberian Plateau, the Putorana Plateau, is located in this area, its height is 1700 meters above sea level. In the Cenozoic, surface uplift continued. At the same time, a river network was being created on the surface. In addition to the Putorana plateau, the Byrranga, Anabar and Yenisei massifs rose most intensively. Subsequently, active tectonic processes that took place in this territory led to a change in the river system. Traces of river systems that existed in ancient times have survived to our time. At the same time, river terraces and deep river valleys of the central part were formed.

The thickness and mobility of the glaciers of Eastern Siberia was insignificant, therefore, they did not have such a significant impact on the relief as in other places. In the post-glacial period, the uplift of the plateau relief continued.

The modern relief of the Central Siberian plateau is characterized by elevation and contrast of the relief. The height above sea level on its territory ranges from 150 to 1700 meters. A distinctive feature of the Central Siberian plateau is a flat and gently undulating relief of interfluves with deep river valleys. The most significant depth of the river valleys, up to 1000 meters, is typical for the western part of the Putorana plateau, and the smallest 50-100 meters for the Central Tunguska plateau, the Central Yakut and North Siberian lowlands.

The vast majority of the river valleys of the Middle Siberia canyon-like and asymmetrical. Their characteristic feature is also a large number of terraces, which indicates repeated tectonic uplifts of the territory. The height of some terraces reaches 180-250 meters. In Taimyr and in the North Siberian Lowland, the river valleys are younger, and the number of terraces is somewhat less. Even the largest rivers have here three or four terraces.

Four relief groups can be distinguished on the territory of the Central Siberian Plateau:
1. Plateaus, ridges, ridges, and mid-mountain massifs on ledges of the crystalline basement
2. Layered uplands and plateaus on sedimentary Paleozoic rocks
3. Volcanic plateaus
4. Accumulative and reservoir-accumulative plains

Most of the tectonic processes that took place in antiquity and in modern times in Eastern Siberia, coincided in direction. However, this did not happen throughout the entire territory of the Central Siberian Plateau. As a result of these discrepancies, depressions similar to the Tunguska were formed.

Modern erosion processes on the territory of the Central Siberian Plateau are hindered by permafrost, which is typical for this area. It also prevents the development of karst landforms - caves, natural wells, funnels and other formations that occur during erosion. groundwater some rocks. But here, uncharacteristic for the rest of the territory of Russia, relic ancient glacial landforms are found. Karst landforms are developed only in some southern regions of Eastern Siberia, where there is no Lena-Angara and Lena-Aldan plateau. But the main small relief forms on the territory of the Central Siberian Plateau are still erosive and cryogenic.

Due to the strongest monsoons of the sharply continental climate characteristic of Eastern Siberia, here you can find a large number of stony placers and screes in mountain ranges, on the slopes of river valleys and on plateau surfaces.

According to the materials of the big encyclopedia of Russia