A vast territory lying to the east of the lower reaches of the Lena, north of the lower reaches of the Aldan and bounded in 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 Northern Arctic Ocean) exceeds 1.5 million. km 2. Within North-Eastern Siberia are located East End Yakut Autonomous Soviet Socialist Republic and the western regions of the Magadan region.
North- Eastern Siberia located in high latitudes and in the north it is washed by the seas of the Arctic Ocean. 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 modern relief 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 has been clarified, etc. Discovery large deposits 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 is replaced here 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 Yano-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 sediments, and the Jurassic formations 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. 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.
Formation of modern mountainous terrain 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
The traces of mountain-valley glaciation are much better expressed 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 conifers appeared in the composition of forest vegetation, including the Daurian larch that is now dominant.
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 severe, 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. In addition, the processes of nivation, solifluction, and frost weathering are of greater importance 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.
In accordance with the morphogenetic features 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 deposits - alluvial, lacustrine, marine and glacial. They are characterized by a slightly rugged topography and slight fluctuations. relative heights. Forms that owe their origin to permafrost processes, large ice content of loose deposits and the presence of thick underground ice are widespread here: thermokarst basins, permafrost heaving mounds, frost cracks and polygons, and on the sea coasts, high ice cliffs are intensively collapsing (for example, the famous Oyegossky Yar with a length of more than 70 km).
Accumulative plains occupy vast areas of the Yana-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 are 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 Uplands, 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, some of which have been preserved here 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 North-East 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-Khayat, Tas-Khayakhtakh, the Chersky Tas-Kystabyt ridge, Ulakhan-Chistai), as well as central regions Verkhoyansk ridge. Due to the fact that the activity of Quaternary and modern glaciers played the most significant role in the formation of the alpine relief, 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 regions. climatic zones, at a considerable height above sea level and isolated by mountain ranges from the effects of the seas of the Pacific Ocean.
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. Within seven to eight months (from September - October to April) radiation balance 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, for winter months 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. 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 thick here that even in the daytime you have to turn on the lights in the houses, and turn on the 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 higher pressure over the northern seas. 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 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 rainfall, and 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 temperature in July 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. A certain role in the nutrition of rivers is played by groundwater and the melting of "eternal" snow and glaciers in 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, on most rivers there is the most high level water. 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 rivers Dulgalakh and Sartang - flow down from northern slope Verkhoyansk ridge. 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 characterized 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 geographical latitude and elevation 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-grade forests of the northern taiga appearance 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 most southern 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 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 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. The total length of currently operated waterways is 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. Mastering it 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. State farms created in the upper reaches of the Indigirka and Kolyma meet part of the needs of the population in 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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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. general power earth's crust- 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 Central Siberia experienced an uplift. It is no coincidence that this area is home to the most high point The Central Siberian Plateau is the Putorana Plateau, 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
Majority 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 when some rocks are washed away by groundwater. 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, a large number of stony placers and screes can be found here in mountain ranges, on the slopes of river valleys and on plateau surfaces.
Based on materials big encyclopedia Russia
Central Siberia
Siberia has been and remains a unique part of the planet Earth. The unique scale of its territory, the diversity of natural and climatic conditions, flora and fauna located in the depths of mineral resources, the energy capacity of rivers and the purity of lake waters, the original history and culture of the peoples inhabiting it. It is no coincidence that Siberia was originally called a land or a country. The annexation of Siberia has become the most valuable acquisition of the Russian state for the entire time of its existence and the most important milestone on the way to the formation of the Russian Empire.
The first information about the nature of Central Siberia - its rivers, climate features and fur wealth - were obtained as a result of campaigns of Russian "service people" in early XVII century. Their observations were used in the preparation of maps and drawings, which contained a fairly accurate image of the most important geographical objects of the country for that time. In the 19th century, reconnaissance scientific research was carried out in many regions of Central Siberia. At the beginning of the 20th century, mineral deposits of Central Siberia (gold, coal, iron ore), navigation conditions on rivers and climate were studied. Expeditions of the Resettlement Administration on a large scale undertook studies of soils and vegetation in the southern regions of the country.
At present, the nature and natural resources of Central Siberia have been relatively well studied. Deposits of various minerals have been discovered in the bowels of the region. Hydropower resources and conditions for the construction of powerful hydroelectric power stations on the Angara, Lena and other rivers have been studied.
Central Siberia has its own distinctive features of flora and fauna and its own contribution to the general structure of life on Earth.
The nature of the Central Siberian Plateau
Geographical position, geological structure, tectonics and history of the development of the territory
The Central Siberian Plateau is located between the Yenisei and Lena rivers. In the north, the plateau abruptly breaks off to the North Siberian Lowland, and in the south it comes to the foothills of the Eastern Sayan, the Baikal region and the North Baikal highlands. The average heights of the plateau reach 500 - 700 meters. The most elevated areas are 1500 - 1700 meters (Putorana Plateau).
The most ancient part of the plateau is the Siberian platform. The most important feature structure is the high position of the Argian and Lower Proterozoic folded basement and overlying sedimentary Upper Proterozoic and Paleozoic deposits, penetrated by volcanic rocks and exposed to the ancient surface in most of the territory. Oscillatory movements on the platform created anteclises and syneclises, the depth of the foundation in the latter reaches 5000 - 7000 meters.
The Siberian platform has two large uplifts of the Argian basement, the Anabar and Aldan shields. The Anabar shield is located in the upper part of the Anabar river basin. The folded base is the most elevated in the central part and comes to the surface, and along the edges the basement surface descends under sedimentary deposits.
In the west of the Siberian platform, dislocated Riphean rocks (schists, teys, marbles, quartzites, all of which are cut through by intrusions) emerge, forming projections of the Baikal basement of the platform - the Yenisei and Turukhansk uplifts.
The subsided sections of the foundation form syneclises and deflections. In the basins of the Angara, Kureika, Nizhnaya and Podkamennaya Tunguska rivers, there is the Tunguska syneclise, which is filled with Cambrian deposits and marine lagoon sediments of the Devonian and Lower Carboniferous. Upper Paleozoic and Early Mesozoic rocks fill the entire Tunguska syneclise and consist of the so-called Tunguska suite, which is formed by thick continental deposits (sands, sandstones, gray clays and coal seams), tuffaceous suite and traps. Coal-bearing strata belong to the Carboniferous and Permian systems, forming the Tunguska basin. Its area is 1 million km2.
Effusions and intrusions of basic rocks (diabases and basalts) began in the Permian period and continued until the beginning of the Jurassic. Volcanic processes on the Central Siberian Plateau manifested themselves in the form of powerful effusions that formed colossal lava sheets, sheet intrusions and laccoliths in the thickness of the Upper Paleozoic rocks. The main distribution of traps is associated with the Tunguska syneclise, but they are also found beyond its borders. Under the influence of trap intrusions, part of the coals turned into high-quality graphite. The largest deposits of graphite are concentrated in lower parts basins of the Kureika and Nizhnyaya Tunguska rivers.
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The Vilyui syneclise is located between the Anabar and Aldan shields. At its base is the Urinsky aulacogen filled with Proterozoic rocks. In place of the aulacogen, the Vilyui syneclise developed with a thick stratum of Paleozoic and Mesozoic deposits, among which there are deposits of Cambrian salt, Jurassic and Cretaceous coals.
In the Carboniferous and Permian, the northwestern part of the platform was lowered and the Tunguska syneclise was formed. Its surface was covered with lakes and swamps, and coal accumulated.
In the Jurassic period, in connection with tectonic activity, the formation of the main morphostructures occurs; in the zones of stable subsidence, negative morphostructures were outlined (Vilyui syneclise, Angara-Vilyui and Sayan troughs), and in the zones of uplifts - positive (straight lines - Anabar anteclise; inverted ones arose in the Tunguska syneclise, the Putorana plateau, etc.).
From the end of the Paleogene to the beginning of the Pleistocene, due to neotectonic movements, further changes in the relief and the formation of modern morphostructures take place.
By the beginning of the development of the mainland branch, the Central Siberian Plateau rose again, in connection with which the rivers cut and lower basement and accumulative terraces formed in their valleys. In the valleys of large rivers, there are up to 8-10 terraces. Simultaneously with the incision of the rivers, the ledges of the Byrranga and Putorana plateaus were formed, facing the North Siberian Plain, which sagged and was flooded by the waters of the borgal transgression. Marine Quaternary deposits of this transgression are now at altitudes of 200-220 meters.
In the Pleistocene, under the influence of glacial exaration and accumulation, erosion, nivation, frost weathering, solifluction, and permafrost, morphosculpture was formed. The northwestern part was covered by the Middle Pleistocene and Late Pleistocene glaciations, the centers of which were in the Byrranga, Putorana and Anabar shield mountains. To the south of the glaciation boundaries there were severe perigmatic conditions.
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In general, Central Siberia, confined to the Central Siberian Plateau, is a country of traps and Tunguska coals. It has a fire-breathing past, although now there are no active or extinct volcanoes here. At the beginning of the Mesozoic era, the nature was different: interstratal and vein intrusions of igneous masses penetrated the body of the platform and the structures of adjacent troughs, and in some places lavas poured onto the surface. A complex system of solidified volumes of magma survived in the bowels, erosion separated them in the form of armoring layers on vast plateaus up to a million km2 in area. Where the reservoir intrusions were located in several tiers, stepped slopes arose (these lava layers are called traps - from the Swedish. "ladder"). The vents of many Mesozoic volcanoes are explosion tubes; during their formation, rare conditions arose that are necessary for the birth of diamond crystals. Two outcrops of the deep basement of the Siberian Platform - the Anabar Shield and the Yenisei Ridge - were built by Precambrian rocks, and the Anabar structures are older than the Yenisei. In other areas, the platform is two-tiered - the basement is covered by horizontally lying Paleozoic sedimentary strata, the extensive basement trough is the Tunguska depression. Here, in a thick stratum of continental strata, in the Upper Paleozoic and the beginning of the Mesozoic, the coal-bearing Tunguska suite was concentrated. Thus, one of the richest coal basins in the country, the Tunguska, arose.
In the south, the Pre-Sayan trough borders the platform, in the north there is the North Siberian depression. Only in the east, the boundary is devoid of certainty - the structures of the platform gradually sink towards the Vilyui depression, and the relief of the plateau just as imperceptibly passes into the plain.
Millions of years of erosion would long ago have turned the territory into a residual plain, but the latest uplifts, breaking open, humping and tilting the surface, enlivened the incisions of the valleys, and karst was powerfully formed in the salt-bearing and limestone strata in vast spaces - caves, tunnels with underground rivers arose.
The geographical position of the Central Siberian plateau on the ancient Siberian platform determined the complexity and diversity of the geological structure, the development of physical and geographical processes, the nature of minerals and the formation of natural complexes. The territory of the region is composed of rocks of the Precambrian (Archaean, Proterozoic), Paleozoic, Mesozoic and Cenozoic age, that is, starting from the most ancient and ending with modern formations.
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Relief
Against the background of the rest of the predominantly mountainous High Siberia, Middle Siberia seems to be relatively even, as if an intermediate step between the plain of the west and the mountains of the south and east. But its surface is rarely called a plain. More than a quarter of the territory is characterized by intricately dissected mountainous terrain. The very word "plateau" here is rather a tribute to tradition. The acquaintance of geographers with this country began with its flat parts, and horizontally lying layers were visible in the cliffs of the outskirts.
Along the meridian, Central Siberia is elongated, like Western Siberia, but the differences between the latitudinal zones recede into the background here. Almost the entire plateau is dominated by a variety of landscapes, this is facilitated by differences in the structure of the bowels, the recent uplift of the protrusions of the ancient basement and the high mobility of the younger outskirts of the plateau. Its northern and middle parts are more stable - the platform is stable here, while the south lies beyond its borders - these are ancient foothill troughs. Beddings in them are disturbed by old processes of folding, and the latest erosion creates not only table and stepped plateaus, but also sloping ridges, and even ridges in the Cis-Baikal trough.
The Central Siberian Plateau was formed in the western part of the Siberian Platform, the structures of which were rigidly soldered as a result of trap magmatism. All this territory in the Meso-Cenozoic steadily rose as a single structure and is represented in the relief by the largest orographic unit. The Central Siberian Plateau is characterized by a significant elevation and relief contrast. The height within it ranges from 150-200 to 1500-1700 meters. The average height is 500-700 meters. A distinctive feature of the plateau is the combination of a predominantly flat or gently undulating stepped relief of the interfluves with deeply incised steep-slope (often canyon-like) river valleys.
By the nature of the distribution of heights and dismemberment, the Central Siberian Plateau is very heterogeneous. Within its limits, more fractional orographic units are distinguished. The plateau reaches its maximum heights in the northwest, where the Putorana plateau (up to 1701 meters) and Syverma (more than 1000 meters) rise. They are adjoined by the Anabar plateau, the Vilyui and Tunguska plateaus with heights up to 850-950 meters.
From the Central Yakut Plain, located to the east of the Central Siberian Plateau, and confined to the Vilyui syneclise and the Predverzhoyansky trough, a lowered strip (300-500 meters) stretches through the territory of the plateau to the foot of the Sayan. Within its limits are the Angara and Central Tunguska plateaus. To the southeast of this band, the surface rises. Here are the Angarsk Ridge and the Lena-Angara Plateau with a height of up to 1000-1100 meters. To the northeast, they pass into the Prilenskoye plateau, limiting the Central Yakut plain from the south. Thus, according to the altitudinal position, the Central Siberian Plateau is clearly divided into three parts: the northwestern - the most elevated, the central - lowered, the southeastern - elevated.
The Central Siberian Plateau is characterized by the development of a multi-tiered stepped relief, the formation of which is due to the structural features of the Siberian Platform, long-term continental denudation since the pre-Jurassic, the lithology of the constituent rocks - dense traps and less stable sedimentary rocks of the Pamozoic and Mesozoic age, and the latest tectonic movements that have intensified the denudation process. Dividing spaces have the appearance of either isolated mesas or elongated ridge-like hills. In some places, individual ridges, composed of volcanic rocks (diabases and basalts), rise up under the uniformly leveled surfaces. The flat areas are swampy in some places. In the northwest is the Putorana Plateau, composed of traps and volcanic tuffs. In its middle part, in the upper reaches of the Katanga River, concentrated maximum heights(1701 meters). To the west and east, the height of the mountains gradually decreases to 600-700 meters. Traces of ancient glaciations are widespread in the mountains. The bottom of the intermountain depressions is occupied by rivers (upper reaches of the Pyasina, Kheta and others) and lakes (Keta, Khantayskoe). In the upper reaches of the Anabar and Olenek rivers, there is the Anabar plateau with glacial processing. Its maximum heights reach 700-900 meters. From the southwest, the Central Siberian Plateau borders the Yenisei Ridge, it extends from the mouth of the Podkamennaya Tunguska River almost to the Eastern Sayan, which is separated by a tectonic depression. The highest height of the Yenisei Ridge is Mount Epashimsky Polkan (1104 meters).
Thus, the relief of the Central Siberian region was formed under the influence of internal and external forces that manifest themselves on our planet. Certainly, it is quite unique.
At the base of the Central Siberian plateau lies a hard massif of ancient crystalline rocks that are weakly compressible, which determined the nature of the relief of the plateau. From above, these rocks are covered with traps.
Climate of Central Siberia
The climate of the territory is sharply continental. The continentality of the climate is determined by the geographical position and relief. The territory is located in the center of the northern part of Asia, elevated, removed from the warm seas, fenced off from them by mountain barriers. In most of the territory, except for the south, the radiation balance has a negative value from October to March. Orographic conditions have a significant influence on climate formation. Large mountain ranges and deeply incised river valleys determine local climatic differences, uneven distribution of precipitation during winter temperature inversions. By annual number of hours sunshine the southern part surpasses many southern regions of the country: in Irkutsk it reaches 2099 hours. Compared with the climate of other territories located at the same latitudes, the continentality of the climate is expressed in the coldest and coldest winters, the warmest summers and the least annual precipitation. Therefore, the climate is characterized by a large temperature amplitude and negative annual air temperature (Bratsk -2.60C).
Precipitation falls mainly in summer, 4-5 times more than in winter, which is twice as long as summer. On the Central Siberian Plateau, the annual precipitation is 300-400 millimeters. The continentality of the climate increases towards the east, which is expressed in a decrease in the amount of precipitation, and in the mountains the amount of precipitation increases.
In winter, the entire territory is very cool, which contributes to the development of a stable powerful anticyclone from October to March. From the center of the Asian anticyclone to the north and northeast, a spur actually extends high pressure that fills almost the entire area. Cold continental arctic and temperate air masses dominate. The weather is mostly clear, windless, with low temperatures.
In winter, precipitation is occasionally brought by cyclones coming from the west. Long stay sedentary anticyclones over the territory causes a strong cooling of the surface and ground air layer, the occurrence of powerful temperature inversions. This is also facilitated by the nature of the relief: the presence of deep river valleys and basins in which masses of cold water stagnate. heavy air. The continental air of temperate latitudes prevailing here is characterized by very low temperatures and low moisture content. Therefore, January temperatures are 6-200C lower than the mid-latitude ones. The lowest January temperatures are typical for the northeastern part of the Central Siberian Plateau (-42…-430C). There is little precipitation in winter, about 20-25% of the annual amount.
Summer is relatively warm. The total solar radiation in July in the north reaches 12-13 Kcal/cm2, in most of the territory - 13-14 Kcal/cm2.
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In summer, due to warming up, a lower pressure is established over the territory. Air masses rush here from the Arctic Ocean, the western transfer is intensifying. But the cold Arctic air, entering the land, very quickly transforms (warms up and moves away from the state of saturation) into the continental air of temperate latitudes. July isotherms run sublatitudinally within the Central Siberian Plateau, this pattern is obscured by the influence of the relief. The high hypsometric position causes less heating of the surface, therefore, in most of its territory, the average temperature in July is 14-160C and only in the southern outskirts reaches 18-190C (Irkutsk 17.60C). With an increase in the height of the terrain, summer temperatures decrease, that is, on the territory of the plateau, a vertical differentiation of temperature conditions can be traced, which is especially pronounced on the Putorana Plateau.
The continentality of the climate naturally increases in an easterly direction, and especially in the northern part. Thus, the average air temperature in January at the northwestern limit of the zone is -320C, and at the eastern limit -380C, the average July temperatures are +14 and +180C. at the southern border, the average January temperature is 260C, and the average July temperature is +180C. The average temperatures for the year are negative everywhere: at the northern border - about -100C, and at the southern border - about -40C. To the east, the amount of precipitation decreases from 500 to 250 mm, as well as evaporation from 250 in the southwest to 150 mm in the northeast.
The cooling of the mainland in winter creates stable anticyclonic weather with severe frosts, low wind speeds and an abundance of calms with moderate, and in some years even thin snow cover. In October, an anticyclone begins to form, it reaches its maximum in January, and collapses from March. Surface layers of air are intensively cooled and sometimes become colder than arctic air masses. Throughout the territory, they can drop annually to -50, and sometimes even to -620C, once every 15-20 years in January they rise to 3 and even to 00C, but there is no thaw.
Winter moves from the northeast to the southwest, where it lasts a total of 5 months. Characterized by stable temperature inversions with an increase of 1-30C for every 100 meters of height. In this regard, "lakes" of cold are formed in depressions not only in winter, but also in transitional seasons. Therefore, the plants in the depressions suffer from frost, and on the uplands and slopes more productive and species-rich forests grow in comparison with the forests in the depressions.
When the temperature drops below -350C, frosty fogs usually appear over settlements - water vapor condenses. Fogs rise up to 40-50 meters, and sometimes up to 100 meters. The maximum annual cloudiness differs in November up to 25 cloudy days. The sunniest is March, when there are no more than 14-15 cloudy days.
During the long almost semi-annual cold period, only about 15% of the annual precipitation falls. Snow lasts from October to May (from 250 days in the northwest to 230 days in the northeast and 185 in the south). Its distribution largely depends on the relief. If in the valleys its thickness does not exceed 30-40 centimeters, then on a hill it reaches 60-80 centimeters. In general, the greatest thickness of snow cover is observed in the Katanga basin in accordance with the November snowfalls. The growth of snow cover continues until January, then slows down. It depends on the increase in the evaporation of snow on sunny days. Persistent and severe frosts with a small snow cover create conditions for the preservation, and in some places for an increase in permafrost soils.
The transition from winter to spring in the southern part of the zone is usually abrupt with a significant difference between low nighttime and high daytime air temperatures, especially on cloudless days. Sometimes, during the transfer of warm air masses from Central Asia, positive average daily temperatures are observed already in the first ten days of April. However, frosts occur until June.
In spring, air humidity is minimal (50-60%) and the least cloudy in the year. In combination with low rainfall (about 12% of the annual amount), droughts occur, especially in the southern part. This contributes to the dominant distribution of larch. Spring is also the windiest time of the year with changeable winds that change direction. Their speed often exceeds 15m/s. Fairly evaporated during sunny March, the snow melts quickly, with the exception of elevated shady places. But constant night frosts slow down the thawing of soils, which excludes their moistening with melted snow water, which quickly rolls into rivers without benefit for future crops.
The predominant transfer of air masses in the warm part of the year is from the west. Less often cold masses of it come from the north. Cyclonic activity develops. Usually cyclones bring rains, except for those that originate in Central Asia. However, the influence of the last sharp cyclones is limited only to the southern part of the zone. Cold arctic air flows into the rear of the western cyclones, causing cooling down to frost.
The frost-free period naturally decreases from west to east and from south to north. Its average duration in the valleys of the southern rivers is 90-100 days, in the northwest - 70 days, and in the northeast - no more than 60 days. Daytime temperatures in summer are quite high everywhere and often exceed 300C. evaporation is greatly increased. Cyclonic activity dramatically increases the amount of precipitation. For 2-3 months they fall more than half of the annual amount, maximum in July - the first half of August.
Autumn, like spring, is very short and comes immediately, passing from warm summer days to constant night frosts. Everywhere in the beginning of autumn the weather is usually dry and clear. By the end of autumn, cyclonic activity fades. An anticyclone begins to form. Frequent frosts occur at the end of August. In the valleys of small rivers, frost occurs at the end of August. In the valleys of small rivers, frost occurs at the end of August. In the valleys of small rivers, frosts begin almost a month earlier than in the valleys of large ones. In October-November, the cloudiness is the highest for the year, but fogs decrease, the maximum of which occurs in August-September. AT different years the change of seasons of the year deviates up to two weeks in one direction or another.
As a result, we can conclude that the climate of the Central Siberian Plateau is formed under the influence of solar radiation entering the earth's surface, the circulation of air masses and moisture circulation, as well as the underlying surface. The close interaction of these factors determined the formation of a sharply continental climate with long cold winters, low precipitation, relatively hot and humid summers, short transitional hot and humid summers, and short transitional periods from winter to summer.
Inland waters
The largest rivers of Russia - the Lena, the Yenisei and their numerous tributaries - flow through Central Siberia.
The watershed between the Yenisei and the Lena runs along the Central Siberian Plateau from south to north. In the northern part of the plateau, a watershed extends from west to east, separating the Pyasina, Khatanga, Anabar and Olenyok rivers from the upper reaches of the tributaries of the Nizhnyaya Tunguska, Kureika and Vilyui rivers. All rivers carry their waters to the Laptev and Kara seas. Some rivers begin in the mountains, in the middle reaches their valleys are of a transitional nature, and finally, in the lower reaches they enter the plains and become typical lowland rivers. These include the Yenisei, Lena and the left tributaries of the Angara, Uda, Oka, Irkut and others. Other rivers - and most of them - begin on the Central Siberian Plateau. Their upper sections approach the flat rivers. In the middle reaches, they cut deeply into the plateau, flowing through a narrow rapids valley, and in the lower reaches they become flat (for example, Podkamennaya and Lower Tunguska, Vilyui).
Large rivers flow within the permafrost through the taiga. The upper reaches of the rivers are located in the southern regions: here they have many tributaries, bringing a large amount of water to the main rivers. The rivers are fed by rain and snow, part of the water in the rivers comes from the melting of ice and permafrost. Ground feeding is negligible. Spring-summer flood. During 4-6 warm months, more than 90-95% of the annual runoff occurs. The minimum flow of all rivers is observed in winter. Due to the long cold winter, the ice cover on the rivers is very long. For example, in the northern part of the Irkutsk region, rivers freeze in the first half of November, and break up at the end of April. In winter, as a result of the weakening of the flow and low temperatures, some rivers freeze through. Water flows from the upper reaches of the frozen sections of the rivers and spreads over the surface of the ice, forming powerful icings. At the same time, there are polynyas at the places where powerful ground sources emerge, for example, on the Lena below Kachug. The freezing of the Central Siberian rivers occurs in a very peculiar way. Ice first forms not on the surface of the water, but at the bottom on supercooled pebbles, and then rises to the surface. Freezing on the rivers occurs in October, and on the southern rivers - in early November. The ice thickness on the rivers reaches 1-3 meters. Small rivers freeze to the bottom.
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All major rivers are important transport routes and are used for navigation and timber rafting. The Angara River is navigable from Lake Baikal to the city of Bratsk and in the lower reaches - from the mouth up at a distance of 300 km. The Lower Tunguska is a raftable river, navigable from the village of Turukhansk to the village of Tura. Podkamennaya Tunguska is navigable only in the lower reaches.
Rivers have enormous reserves of electricity. A cascade of powerful hydroelectric power stations has been built and is being built on the Angara and Yenisei, but these large stations also have huge reservoirs, although with a relatively large depth and narrowness of the valleys, they flood even less land than their "colleagues" on the plains of the West. And yet, about 5 1/2 thousand went under the waters of the Bratsk Sea, and a little less than 2 thousand km2 under the waters of the Ust-Ilimsk. The Bratsk Sea stretched along the river for almost 550 km, and its bays, penetrating up the Oka and its tributary, stretched for another 370 and 180 km, respectively. The Ust-Ilimsk reservoir raised the Angara by 300 km. in length, and the bay in the lower reaches of the Angarsk tributary of the Ilim turned out to be shorter by only 1 km. Nevertheless, the width of the new "seas" is also significant. Saved from flooding large stocks wood, primarily drill, - more than 3 thousand km2 of wood was removed. But the part of the forest that has not been cut down harms water bodies. Decaying wood impoverishes the water, the lack of oxygen increases the winter kills of fish.
The Central Siberian Plateau has a well-developed river network. This is due to the significant elevation and uneven height of the territory, the fracturing of rocks, long period continental development, waterproof effect of permafrost, deep and prolonged ozone freezing of soils.
Permafrost not only prevents moisture from seeping into the ground, but also reduces evaporation due to the low temperature of river and groundwater. All this determines the features of the water balance - an increase in the table and, above all, its surface component and a decrease in evaporation compared with similar latitudes of the Russian Plain and Western Siberia.
The rivers are rich in various fish. Sterlet, sturgeon, omul, whitefish, and grayling are of primary commercial importance. Salmon fish make up 97% of the catch. The largest number of these fish is concentrated in the mouths of the Yenisei and Lena rivers.
Soils, vegetation and wildlife
In connection with the appearance of perennial soils of the eastern Yenisei Ridge, soil formation differs markedly from the western territories. The soil profile is more often loosened from the western territories. The soil profile is often loosened by the seasonal intrusion of ice, causing its mobility.
The podzolic process is suppressed and occurs mainly on deep-thawing sandy-clay soils, especially on river terraces. In the interfluves, soils are formed on massively crystalline or tree-saddle stony rocks. As a result of orthoeluvia, the usually stony amount of fine earth quickly decreases with depth and height, becoming strongly gravelly.
Due to the low-temperature substrate, litter humification proceeds extremely slowly, and the organic-cumulative horizon A1 becomes coarse-humus and often peaty. Easily soluble substances, and especially fulvic acids, are quickly washed out of it. Looseness and gravelly soil profile accelerate the migration of most substances, including silica. Humus is found throughout the soil profile, although in lower proportions. If in the upper part its content reaches 8-10%, then at a depth of 50 cm - about 5%, and at a depth of 1 meter there may be 2-3% of humus.
The A2 podzolic horizon is by no means always formed, especially in the northern half of the Central Siberian taiga. In general, podzolization is typical here on those parent rocks that include light, weathering-resistant minerals - quartz, feldspar, micaceous silicates, i.e. mainly on sands and Mesozoic sandstones, developed just in the southern half of the plateau. But a podzolic or simply lightened horizon is never thicker than 3-5 cm; it is usually underlain by a bright brown horizon. This is due to the leaching of iron and fulvic acids. With depth, humic substances are gradually deposited around the mineral grains in the form of humus-iron-oxide compounds, coloring the soil brown. The brightness of the color decreases downward, although the glandular compounds increase. The permafrost screen, which moistens the soil during the growing season, affects the small differentiation of the soil profile. The high content of fulvic acids causes a strongly acid reaction of soils with a pH of water extract of 4-6. A small amount of humus and high acidity do not provide soil fertility.
In the south, in the Angara River basin, clayey slightly podzolic and soddy-forest soils without a podzolic horizon are more common. A dark gray upper humus horizon and a transitional one to the parent rock stand out. In soils on traps rich in sesquioxides, where humic acids predominate over fulvic acids, calcium and magnesium are leached, and a ferruginous film is formed around the primary minerals, which inhibits podzolization. Such soils are called sod-iron-aluminum.
On carbonate rocks of the lower Paleozoic plain, soddy-calcareous soils with a weakly differentiated profile, but with a dark gray humus horizon, containing 5-6% humus and about 9% calcium carbonate. Humic acids predominate in humus. The reaction is neutral or even slightly alkaline.
In the northern taiga, a new type of soil on traps, granuzems, has recently been studied. They are formed in the conditions of a sharply continental climate on a rock that, when weathered, produces minerals with framework structures, pyroxenes, glasses, in which clay minerals do not transform. Rapid physical crushing contributes to the accumulation of amorphous iron and aluminum compounds and the rapid removal of the products of the interaction of humic acids with minerals. A thin soil (about 20 cm) is formed with an unexpressed differentiation into genetic horizons in chemistry close to the parent rock, but with a high humus content of the fulvic composition and unsaturation of the absorbing complex.
Vegetation.
The vegetation cover of the taiga zone, which occupies more than 70% of the territory, has the most peculiar character. Despite this relative homogeneity and the vast expanses occupied by the taiga, it is not always the same. Differences in the thickness of the permafrost layer, in appearance, in drainage and other factors create some diversity in the plant world.
Within the boundaries of Central Siberia, light coniferous forests of Siberian larch (in the west) and Daurian larch (in the east) predominate. The dark coniferous taiga is pushed back to the extreme western regions. Warm and not very humid summers are the reason for the more significant advancement of forests to the north than anywhere else.
Animal world
The fauna of Central Siberia differs from the fauna of Western Siberia: it is more ancient; the sharp continentality of the climate contributes to the large movement of taiga species to the north in the summer; in harsh climatic conditions, the hairline of fur-bearing animals acquires a special splendor, tenderness and silkiness.
The taiga has a more diverse and rich animal world. Of the predators, the brown bear, wolverine, fox, Siberian weasel, ermine, and sable are common. Wolverine lives everywhere. This nocturnal predator settles under tree roots, in rock crevices, in soft ground and in snow. Kolonok with brown fluffy silky fur. It is distributed in the Vimoya basin in dense taiga with undergrowth. Sable is rare and spread over stony placers in dense taiga. The lynx is the only animal from the cat family, its habitat is dense taiga forests. Of the ungulates in the taiga, elk and musk deer are common, and on the Putorana plateau there is a bighorn sheep. Maral and roe deer are common in the southern part of the Cis-Yenisei taiga.
There are numerous rodents in the taiga, especially the squirrel, which occupies a prominent place in the fur trade; it is found throughout the territory, but its main habitat is the central dark coniferous taiga. Of the other rodents, chipmunk, white hare, and vole are common. Of the birds, hazel grouses, white partridges and many others are common.
Beginning in 1930, the muskrat was released into the territory of the Irkutsk region. Its habitats are reservoirs, slowly flowing rivers, where there is a lot of wetland vegetation. In the western part of the Irkutsk region, the acclimatization of the hare and the American mink was carried out.
It is important to note that many animals of Central Siberia are wrapped in warm coats of fur and feathers, which are especially necessary in winter, they are much larger than their relatives living in a milder climate, which is an advantage in conditions when it is necessary to keep warm (the larger the animal, the less surface that loses heat relative to its size).
Thus, the formation and distribution of soils, flora and fauna over the territory of the plateau is greatly influenced by its specific harsh sharply continental climate and the almost universal distribution of permafrost associated with it. The conservation of permafrost is favored by low average annual temperatures and the peculiarities of the cold period inherent in this climate: low temperatures, low cloudiness, which contributes to night radiation.
The diversity of the soil cover of the Central Siberian Plateau is closely dependent on the heterogeneity of rocks, topography, moisture conditions, temperature regime and the nature of vegetation. The species composition of animals, their number, lifestyle, external coloration depend on the characteristics of the surrounding geographical environment.
Natural resources
The territory of the Central Siberian Plateau is rich in natural resources, it is especially provided with minerals, hydropower and forest resources.
So, in the west of the Siberian Platform, there are dislocated Riphean rocks (crystalline schists, gneisses, marbles, quartzites), here is one of the largest iron ore basins in Siberia - the Angara-Pitsky - located in the Yenisei Ridge; it is confined to a large synclinorium. Iron ores of sedimentary origin are noticed in the upper Proterozoic sequence.
Here is one of the largest coal basins in Russia, its coal-bearing strata are attributed to the Carboniferous and Permian systems. Under the influence of trap intrusions, part of the coals turned into high-quality graphite. The largest deposits of graphite are concentrated in the lower parts of the Kureika and Nizhnyaya Tunguska river basins.
The Lena coal basin is located in the Vilyui syneclise and in the Verkhoyansk trough.
Most of the Central Siberian Plateau is covered with taiga, including the Angara region belongs to the forest surplus zone.
The fauna is rich in game and fur animals, for the production of which Central Siberia occupies a leading position.
The rivers of the Central Siberian Plateau have a significant hydropower potential, for example, the Ust-Ilimskaya HPP (4.3 million kW) and the world's largest Bratskaya HPP (4.5 million kW) are located on the Angara River, as well as the Vilyuiskaya HPP on the Vilyui River.
Thus, the territory of the Central Siberian Plateau is provided with all types of natural resources; as a result, the following industries are developed in the economy of the region: fuel, non-ferrous, forestry, energy, fur and fur.
The current state of landscapes and geoecological problems, possible ways their decisions
The economic basis for the development of the economy of Central Siberia is the approach of industry to the sources of raw materials. But the development of natural resources in the harsh Siberian climate costs a lot and respect for nature in the process of exploiting its resources. In the last decade, more and more centers of local changes in nature have appeared in the course of mining in the course of transport and energy construction.
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Man actively invades nature and often changes the regime of permafrost, which entails not only a change in the soil and vegetation cover, but often also in the relief. These changes turn out to be irreversible, although they do not yet cover large areas. The Angara basin is a striking representative of the areas of human impact on nature. In order to preserve unique and typical natural complexes, to protect animals in 1985, the Ust-Lena Reserve was created in the lower reaches of the Lena on an area of about 1.5 million hectares, and in the Tunguska province - the Central Siberian Reserve with an area of slightly less than 1 million hectares.
It is important to preserve and protect the Central Siberian taiga as far as possible, not only for ethical and moral reasons, as unique environment habitation, and also because, apparently, coniferous forest plays a significant role in regulating CO2 reserves in the Earth's atmosphere. This has become apparent as a result of recent research. The regeneration of the taiga is painfully slow. When layers of soil are removed, permafrost rises to the surface and prevents new trees from growing. It is now obvious that it is human impact that causes the most dramatic changes in the taiga ecosystem.
Large-scale mining of iron ore, gold and minerals has left its mark on large areas of the region. Roads, settlements and all infrastructure have completely changed the local environment. Moreover, metallurgical plants and pulp and paper mills seriously pollute the air.
Influencing factors include:
deforestation;
water and air pollution;
Forest fires;
roads, dams, hydroelectric power plants, pulp and paper mills, metallurgical plants, mining and so on.
Of particular value are the pine and pine-deciduous forests of the Angara basin, where over 35 million hectares are concentrated. Pine forests.
The forest is an important physical and geographical factor that creates a special climate, retains moisture, and reduces wind speed. The vast majority of the territory of the Central Siberian Plateau belongs to the forest areas.
Today, the anthropogenic pressure on the fauna of Central Siberia has increased many times over, although today one can be proud of the leadership in the world in the extraction of valuable fur animals, many birds and river fish, then soon without the organization of cultural hunting and fishing and fish farms, without the creation of reserves and wildlife sanctuaries, nothing of this will not.
Physical-geographical zoning of Central Siberia
natural areas
Throughout the entire length of Central Siberia, 3 zones are distinguished: tundra, forest-tundra and taiga. The taiga is most fully represented, occupying 70% of the area. The Central Siberian Plateau includes only the forest-tundra and taiga.
The forest-tundra stretches in a narrow strip (up to 50-70 km); the boundary of the zone runs along the northern ledge of the Central Siberian Plateau.
The climate of the zone was assigned to B.P. Alisov to subarctic with a predominance of continental air of temperate latitudes in the cold period and transformed arctic air in summer. The combination of the polar position with continentality with negligible radiation and the dominance of anticyclone weather determines the severity winter period, which lasts about 8 months, from October to May. Snow cover lasts 250-260 days. Its thickness is 30-50 cm, slightly increasing towards the west. In summer, the soil and the surface layer of air warms up intensively. The average July temperature is 12-13oC.
Sufficiently high temperatures during the growing season, a decrease in the strength of winter winds, favor the growth of not only herbaceous and shrubby vegetation, but also trees. Of the tree species, Dahurian larch dominates here. The vegetation cover of the forest-tundra is dominated by shrub thickets of birch, alder, and willow. Trees are scattered in individual specimens or groups.
The taiga zone stretches from north to south for more than 2000 km from the northern edge of the Central Siberian Plateau.
The specific features of the Central Siberian taiga, which sharply distinguish it from the taiga of Western Siberia, are the sharply continental climate and the almost universal distribution of permafrost, slight swampiness, the dominance of monotonous deciduous taiga and permafrost-taiga soils.
The climate of the zone is sharply continental, with severe winters with little snow and moderately warm and cool, moderately humid summers. Cold winter with persistent and severe frosts lasts 7-8 months. On the western slopes of the Central Siberian Plateau, the greatest amount of precipitation falls, which contributes to the formation of snow cover up to 70-80 cm thick. The relief and features of atmospheric circulation determine the variegated distribution of precipitation in the zone.
The zonal soils of the taiga are permafrost-taiga. In the central part of the taiga, the density of the tree layer and the height of the trees increase. In the undergrowth, in addition to shrubs, birch, there are bird cherry, mountain ash, elderberry, juniper, honeysuckle. The grass-moss cover is typically taiga. Acid permafrost-taiga soils develop under the forests. In the southern taiga, the diversity of coniferous forests is increasing. In the space of the taiga zone, intrazonal differences associated with the nature of the lithogenic base are clearly traced.
The increase in the severity of winter and the decrease in the thickness of snow cover from west to east have the greatest influence on the distribution of forests across the territory. In this regard, dark coniferous spruce-cedar forests predominate in the Yenisei part. To the east, they are replaced by dark coniferous-larch and pine-larch.
Physiographic provinces and regions
There are two main provinces on the territory of Central Siberia:
1. The province of mountain-glacial tundra and forest-tundra middle mountains and moraine-sea plains occupies the northern part of Central Siberia. The province is characterized by a significant differentiation of neotectonic uplifts. The greatest uplifts were manifested in the fold-block mountains of Byrranga, where local centers of ancient and modern glaciation arose in connection with the uplift of the territory. The moraine-marine accumulative plains were formed on the site of territories with insignificant subsidence and rises. The province is located within the northern part of the Krasnoyarsk Territory and the northwest of the Yakut Autonomous Soviet Socialist Republic.
The arctic deserts and tundras of Taimyr are the northernmost physiographic continental region of the Soviet Union. It occupies the northern half of the Taimyr Peninsula. The Byrranga Mountains stretch from the Yenisei Bay to the Laptev Sea for almost the length of the Caucasus (1000 km) and are divided into three parts: the western one, located between the Yenisei Bay and the Pyasina River with heights up to 400 m; central between the rivers Pyasina and Lower Taimyr with heights up to 700 m; the eastern part is the highest, the highest height reaches 1146 m. The mountains gradually descend to the shores of the seas of the Arctic Ocean, forming a series of low elevations, and fall steeply to the North Siberian Lowland. The ridges and massifs are separated by deep longitudinal and transverse river valleys. The mountains are composed mainly of Paleozoic rocks: in the north of the highlands there are outcrops of Precambrian (Proterozoic metamorphic shales) and acid intrusions of pre-Paleozoic and Paleozoic age. The northern part of the highlands was created in the Caledonian folding, and the southern - in the Hercynian.
The relief is characterized by a wide development of stone placers and a complex of exaration ("ram's foreheads", cara, troughs) and permafrost-solifluction forms. In the central and western parts, the peaks of the mountains are dome-shaped, and in the eastern part, a dissected glacial relief prevails: moraines and sands are common, located in low areas - highlands. There are numerous large snowfields and modern glaciers in the Byrranga mountains.
The winter is severe with a negative radiation balance (from mid-September to April) and a predominance of severely frosty weather types. The duration of the cold period is about 290 days. The average January temperature is -30, -35 ° C. The snow cover lasts from September 15-20 to June 27, and its height in the middle of winter is 20-60 cm.
Summer is short and cold. Total radiation in July it reaches 16 kcal/cm2. The average July temperature at Cape Chelyuskin is +1°С. The annual rainfall is about 200-300 mm. They fall approximately evenly throughout the year, the ratio of precipitation to evaporation is more than 1.33. The entire territory is located in the permafrost zone with insignificant seasonal thawing of the soil during the warm period and to the north of the bullet isoline of the sum of active temperatures.
In the highest part of the mountains, northeast of the lake. Taimyr, where up to 700 mm of precipitation falls at an altitude of 900 m, modern glaciation is developed. The area of all glaciers is about 50 km2. The existence of glaciers and snowfields on the Byrranga highlands, apparently, should be considered as an altitudinal belt of perennial snow and ice, since this is the highest part of the mountains, where "level 365" comes close to the surface of the ridges.
At the foot of the mountains there are arctic tundras on hidden gley (in the northern foothills) and arctic tundra (in the southern foothills) soils. In the southwestern foothills, moss, lichen, and shrub tundras are developed on tundra gley soils.
The altitudinal zonality is expressed in the Byrranga mountains as follows: at the foot of the northern slopes - the Arctic tundra, and the southern slopes - the Arctic tundra and moss, lichen and shrub tundra; along the southern slopes moss-herbaceous tundras rise to a height of 200 m. Higher up the slopes of the mountains there are arctic deserts on cryptogley arctic soils. Even higher - sparse vegetation of talus and rocks, glaciers. Numerous finds of stumps and trunks of trees (larches, birches, willows, spruces) in the Quaternary deposits along the rivers of the Upper and Lower Taimyr, at the mouth of the Pyasina and at Cape Chelyuskin (to the north of 76 ° N) indicate that forest vegetation covered almost the entire territory of the Taimyr Peninsula and the northern border of the forest-tundra was 4-5 ° north of the modern one.
The North Siberian moraine-marine tundra lowland is located between the tectonic ledges of the Byrranga, Putorana and Central Siberian plateaus. In the west, the lowland merges with the West Siberian Plain, and in the east, with the Lena Delta. The hilly surface of the lowland has a height of 50-100 m. The maximum heights are about 225-260 m. From the side of the Byrranga mountains, individual ridges and hills with heights of 400-650 m enter the lowland. m) and Chekanovsky (up to 529 m).
Coast to the west of the mouth of the river. Olenek continues to descend. This is evidenced by the estuaries of the Anabar and Khatanga rivers. To the east of the mouth of the Olenek, the rivers form deltas at their confluence, which indicates the rise of the coast. The area of the river delta Lena is 28500 km 2. Many islands of the delta have developed peatlands, polygonal vein ice and hydrolaccoliths.
The North Siberian Lowland was formed on the site of the submerged Hercynian structures of the Taimyr Peninsula, Mesozoic structures extending from the Pre-Verkhoyansk marginal foredeep. The lowered folded structures form the marginal Khatanga trough, which is filled with Paleozoic, Meso-Cenozoic and Quaternary sedimentary deposits. Mesozoic deposits are coal-bearing. Among the sedimentary rocks there are salt domes composed of Permian, Triassic sandstones, Devonian rock salt (Nordvik).
The climate is arctic with moderately severe long winters and short cool summers. In winter, anticyclonic weather prevails. The duration of the cold period is about 290 days. The average January temperature is about -30, -36°C, the minimum is -61°C. The average temperature in July is from +4°C in the north of the lowland to +12°C in the south. The maximum temperature reaches +30° C. Annual precipitation decreases from west to east from 300-350 to 200-220 mm, and about 100 mm falls in the delta of the Lena River. The zone is excessively humid: the ratio of annual precipitation and evaporation is more than 1.33. The sum of active temperatures is 0-400°С, N=0-3.
The rivers Pyasina, Upper Taimyr and the lower reaches of the Khatanga, Anabar and Olenek flow through the lowlands. Among the hilly-morainic sea plains and on the islands of the Lena delta, there are many shallow glacial and thermokarst lakes. Swamps are common in places: their depth is small, since the top layer of frozen soil thaws by 30-60 cm during the warm period.
In the North Siberian Lowland, moss-lichen and shrub tundras predominate; to the south, shrubs of dwarf dwarf and willow forests are common. The main soils are tundra gley. In the south of the lowland, swampy larch sparse forests appear on gley-frozen-taiga soils. Siberian larch comes from the west only to the sources of the Pyasina, and to the east of it, Dahurian larch is common. Dahurian larch moves along the river valleys far to the north: in the valley of the river. Khatangi - up to 72 ° N. sh. The northernmost forest area on the globe is located on the terrace of the Lukunskaya River (72 ° 34 "N. Lat.). The northern border of the forest on the North Siberian Lowland during the period of the post-glacial thermal maximum was much north of the modern one, approximately at the foot of the Barranga Mountains. For To preserve the northernmost forests on Earth, it is necessary to organize a nature reserve in the Khatanga River basin.
The northern taiga and mountain-tundra plateau of Putorana is located on the northwestern polar margin of the Central Siberian Plateau: the western and northern border it passes along tectonic ledges, in some places forming rocky walls 300-500 m high. The southern and eastern boundaries of the Putorana region are drawn along the border of the Zyryansk glaciation. Putorana is a huge dome-shaped mid-mountain uplift of the Central Siberian Plateau, the highest heights of which are concentrated in the center (1701 m). All rivers begin there (Kotui, Kureika, upper reaches of the Kheta), creating a centrifugal pattern of the hydro network and emphasizing the dome-shaped structure of the mountain system.
The Putorana Plateau was formed on the site of the lowered part of the Tunguska syneclise, the anticline zone and the marginal foredeep of the Baikal folding as a result of intense Quaternary uplifts. The plateau is composed of horizontally deposited Paleozoic sedimentary rocks and traps - volcanic rocks of Upper Permian and Lower Mesozoic age. The determining factor in the creation of the modern relief was tectonic movements: pre-Quaternary and Quaternary splits of the latitudinal and meridional directions, as well as arched uplifts and in some areas of subsidence.
The main relief forms are numerous raised blocks along the lines of splits of the massif - ridges with flat stony watersheds, separated by wide intermountain depressions, young erosional and glacial valleys. The slopes of the mountains abruptly break off to deep intermontane depressions and to valleys created as a result of the activity of rivers and glaciers along the lines of Neogene, Paleogene and Quaternary splits. The depth of dissection of the mountains reaches 800-1500 m. On the Putorana plateau in the Pleistocene, powerful ice sheets, which had a great influence on the formation of morphosculpture. Intermountain depressions are filled with glacial deposits and have a hilly-morainic relief with a large number of lakes dammed by moraines, as well as tectonic ones (lakes Lamo, Keto, Khantai, Glubokoe, etc.). On the slopes of the valleys, circuses and caravans filled with snow are characteristic.
The Putorana Plateau is located in the west of the Siberian region of the subarctic climatic zone and is influenced by the Atlantic and Arctic air masses and the Asian anticyclone. Therefore, there are significant differences in the climate of the western and eastern parts of the plateau. In the west of the Putorana, there is more precipitation and cooler summers than in its eastern half. The winter is long and very cold: the average temperature of the coldest month reaches -30, -38°С, the absolute maximum temperatures in the north are -58°С, and in the east -59°С. The snow cover lies for about eight months. Summer is short, but moderately cool, in lower areas the average temperature of the warmest month is from +12 to +14°C, and in the mountains, at an altitude of 600-1500 m, from +6 to +12°C. The maximum temperature was +28°С in the north, and +31°С in the east, in most of the region the sum of active temperatures was less than 400°С. The annual precipitation in the west is 504 mm, and in the east - 300 mm. Moisture coefficient - 1.33, N = 3.
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The Putorana Plateau is located in the northern taiga subzone, where the western dark coniferous taiga is in contact with the eastern larch taiga. Dark coniferous taiga with larch occupies intermountain basins and valleys, rising up to a height of 250-450 m.
Higher up are larch forests, which, from a height of 450-500 m, are replaced by larch woodlands and thickets of dwarf pine. Soils are mountain permafrost-taiga, gleyic-acid with signs of podzolization. Above 700-750 m, the alder belt follows, turning into mountain shrub tundra. From a height of 800-900 m, mountain tundras (lichen and stony) are widespread. Below continuous stony placers, mountain tundra and mountain arctic soils are developed.
The Anabar socle taiga and mountain-tundra upland is located in the upper reaches of the Anabar and Olenek rivers, on the Anabar shield, which is expressed in relief as a domed uplift. Its maximum heights reach 905 m in the center. The watersheds look like numerous massifs with smooth domed peaks.
The folded Archean crystalline basement of the Anabar shield is elevated in the central part, and the basement surface descends along the edges, overlapping mainly with limestones and sandstones of the Cambrian and Ordovician. In the south-west of the region there are outcrops of sedimentary Silurian and Permian deposits and covers of traps. Between the Anabar Upland and the Putorana Plateau is the Kotuy swampy trap plateau. On the Anabar Upland and the Kotui Plateau, traces of ancient glaciations were found in the form of narrow ridges composed of boulder loam and sand and gravel material. Glaciation was inactive. The watersheds are flat with domed tops; valleys carved in easily eroded rocks, floodplains with ancient terraces, and in some areas (where crystalline rocks emerge) the valleys are narrow with rapids and rifts. The main relief types of the Anabar shield are basement plateaus with glacial and nival processing; along the edges of the Anabar shield, in the area of development of Paleozoic rocks, erosional layered-tiered, water-glacial lacustrine and alluvial plains and a trap plateau were formed.
The climate is subarctic with long cold winters. The average January temperature is -38, -43°C. In the basin of Lake Essey, the minimum inversion temperature was recorded at about -70°C. The summer is moderately cool: the average temperature in July is +12, +14°C. The sums of active temperatures are 700-400°C and less (in the mountains). Moisture coefficient - 1.33-1.00. The annual rainfall is about 300 mm. The area is excessively humid.
The main part of the territory is covered with northern taiga forests of Daurian larch and mountain larch sparse forests on gley-permafrost-taiga and mountain-permafrost-taiga soils. In the south, in the upper reaches of the river. Olenek, permafrost-taiga carbonate rubble soils are developed on sedimentary rocks of the Lower Paleozoic. Forests rise along the slopes of valleys and mountain ranges up to a height of 500-700 m. Higher mountain tundras are developed on mountain-tundra soils.
The Tunguska trap north and middle taiga plateau occupies the basin of the Lower Tunguska and the upper reaches of the Olenek and Vilyui between the boundaries of the Samarovo and Zyryansk glaciations. The heights of the watershed plateaus are up to 981 m (N. Tunguska basin). The river valleys are deeply incised. The surface of the basement of the Tunguska syneclise and the southwestern slope of the Anabar massif subsides to depths of 1000 to 4000 m and is overlain by a thick sequence of Paleozoic and Triassic sedimentary rocks penetrated by traps. During the maximum and Taz glaciations, the region was a marginal glacial zone, and on the surfaces of the trap plateau and stratified-stage plains, bottom and terminal moraine glacial-glacial deposits were formed. During the Zyryansk and Sartan glaciations, the territory represented a periglacial area: in a cold climate, permafrost and treelessness, deluvial and permafrost processes took place; a microrelief was formed - mounds, polygonal forms, etc.
The region lies in the subarctic and temperate zone. The climate is sharply continental, humid. The average January temperature is around -28°C in the southwest and -38°C in the northeast. The average roofing temperature is +15, +16° C. The greatest amount of precipitation in the west is 400-500 mm; in the east, they gradually decrease to 300 mm. The sum of active temperatures is 600-1000 ° C. The coefficient of moisture is 1.33-1.00, N = 6-10.
The increase in precipitation and proximity to the West Siberian Plain predetermined the development of a more diverse species composition of the middle and north taiga forests in the southwest of the region. They consist of larch (Daurian and Siberian), spruce, pine, cedar with an admixture of birch. In the east, the forest is formed by larch with an admixture of birch. Permafrost-taiga, mountain permafrost-taiga carbonate and podzolic soils have formed under forests under permafrost conditions; The highest watersheds (de-800-900 m high) are covered with mountain tundra.
2. The province of non-glacial erosional plateaus and uplands and alluvial-lacustrine lowlands of the forest zone is located in the southern half of Central Siberia, beyond the limits of maximum glaciation. The province is characterized by intense differentiated neotectonic movements. Permafrost and related permafrost-solifluction landforms are widespread. The province lies mainly in the southern part of the Krasnoyarsk Territory and in the southwest of the Yakut Autonomous Soviet Socialist Republic.
The Leno-Olenyok northern taiga plateau is located in the northeast of the Central Siberian plateau, between the border of maximum glaciation and the mountains of the Verkhoyansk ridge. The plain is located on the eastern slope of the Anabar massif, which consists of the Olenyok trough, the Olenyok and Mun uplifts. The depth of the basement in the trough is about 1500 m, and in the uplifts - from 500 to 1000 m. The platform cover is formed by Cambrian and Ordovician carbonate deposits. Of the Quaternary rocks on the watersheds, deluvial - solifluction and eluvial strata predominate, and along the river valleys - alluvial and deluvial-colluvial. The plateau is dissected by deep valleys with flat watersheds. In areas of fractured rocks, the valleys sharply change their directions. The surfaces of carbonate rocks are dissected by modern ancient karst forms. Permafrost-solifluction forms are widespread throughout the territory.
The climate is subarctic with a cold long winter: the average January temperature is -40, -42°C. The duration of snow cover is from 220 days in the south of the region and more than 240 days in the north. The average temperature in July is from +12 to +16°C. The sum of active temperatures is 400-1000°C. The territory is slightly arid, the humidity coefficient is 1.00-0.77. The annual rainfall is over 200 mm.
The region is located in the northern taiga subzone of sparse larch forests. The sparse larch stand in the north - in the forest tundra - is distributed evenly. On the Olenyok uplift, on elevated plateaus north of 70 ° N. latitude, altitudinal zonality is manifested: from about a height of 350 m, the tops of the plateau are covered with mountain tundra on mountain-tundra soils, and along lower watersheds and river valleys, larch sparse forests go far to the north. In the southern part of the Leno-Olenyok watershed, on the slopes of the southern and southwestern exposure, relic steppe grass-forb areas have been preserved.
The main soils of the region are gley-permafrost-taiga soils and at the outcrops of carbonate Lower Paleozoic permafrost-
noteazh carbonate.
The Angara-Tunguska trap middle and southern taiga plateau is located in the basins of the Angara, Podkamennaya and Nizhnyaya Tunguska rivers and the upper reaches of the Lena, in the southern part of the Tunguska syneclise. The plateau is composed of Paleozoic and Lower Mesozoic sedimentary rocks with a wide distribution of traps. The Quaternary cover is formed by eluvial-deluvial, deluvial-solifluction and alluvial processes.
The relief is dominated by erosive layer-tier and trap plateaus separated by deep valleys. In readily soluble rocks, karst forms are developed, especially in the southern Angara region, where funnels, caves, dry and blind valleys arose in gypsum, limestone and dolomite. The traps had a great influence on the landforms of the entire territory: on the watersheds they form an elevated plateau, in the valleys they form canyon-like forms and rapids.
The large fracturing of the traps contributes to the accumulation of groundwater, which comes out in the slopes of the river valleys.
The climate is moderate, continental. Winter is very cold and moderately severe. The average January temperature is from -20 to -30°C, and the minimum is -58°C. The summer is warm: the average temperature in July is +16, +18°C. The sum of active temperatures is 1000-1600°C. The moisture coefficient is 1.00-0.77. The greatest amount of precipitation (about 400 mm) falls in the west of the region, to the east they decrease to 300 mm, N=10-16.
According to morphology, the Angara valley is divided into three parts: the upper one - from the lake. Baikal before the confluence of the river. Oka, 680 km long, where the river flows in a narrow valley with rocky banks; the middle one - from the Oka river to the confluence of the Ilima river, 290 km long, where the Angara passes through the traps, forming the Podkamenny, Padunsky, Dolgiy and other rapids; the lower one - from the Ilma River to the Yenisei, 860 km long, where the Angara River also flows through traps, but the rapids in these areas are much smaller. The regime of the Angara largely depends on the regime of the lake. Baikal. The Angara is characterized by high water content, smooth level fluctuations, especially in the upper reaches. In the spring, the Angara is not flooded, but a decline in water. With the onset of freeze-up, the water level rises and remains high throughout the winter. In the spring, when the ice jams disappear, the water level begins to decrease.
The water temperature in summer at the source (in August) is about + 8.4 ° C. Downstream it rises, reaching + 16.7 ° C near Bratsk (in August). ambient air, and warmer in autumn. In the north of the district, larch forests grow with an admixture of spruce, cedar and pine on permafrost-taiga acidic soils. To the south of the latitudinal segment of the Angara stretches the southern light coniferous taiga, dominated by pine with an admixture of larch, cedar, spruce and birch on soddy-podzolic soils, among which there are soddy-calcareous.
The Yenisei socle taiga ridge consists of separate ridges and massifs with heights of 800-1100 m. The maximum peak is Enashimsky Polkan (1104 m). This range is formed by anticlinal and synclinal structures of the Baikal folding and is composed of Precambrian shales - gneisses and granites. In the northern part of the ridge, sandstones and limestones of the Lower Paleozoic occur on Precambrian rocks. Above the mouth of the Podkamennaya Tunguska, the Yenisei ridge is sawn up by the Yenisei. To the west of the Yenisei valley, it plunges under the sedimentary deposits of the West Siberian Plain. In places of breakthrough, the Yenisei valley is narrow, and there are Osinovsky rapids in the channel. The largest river of the Yenisei Ridge - the Big Pit - cuts it in the south and flows in a narrow deep valley. The socle watershed elevations of the ridge are flat-ridged, swampy in places, many rivers flow from the swamps. The slopes are strongly dissected by river valleys, the depth of which often reaches 180-200 m.
The climate is characterized by cold winters with high snow cover (up to 90 cm) and moderately warm summers. The average temperature in January is about -20, -25°С, and in July +16°С. The sum of active temperatures is 1200-1600°C. Annual rainfall 550-700 mm; the territory is humid, the moisture coefficient is 1.33-1.00. The ridge is covered with dark coniferous mountain taiga forests, consisting of spruce, fir, cedar with an admixture of larch, pine and birch. Mountain permafrost-taiga soils are formed under the forests.
The Lena-Vilyui accumulative and stratified middle taiga plain occupies the subsidence zone of the Siberian Platform basement: the eastern part of the Angara-Lena trough, the Vilyui syneclise and the Verkhoyane trough. The largest rivers of Central Siberia - Lena, Aldan, and Vilyui - flow on the surface of the plain in terraced valleys. The highest heights are located on the outskirts of the region and reach 400-700 m, and the lowest - in the valleys of Vilyui and Lena - about 50 m and below.
The Vilyui syneclise and troughs are filled with terrigenous, salt-bearing and carbonate deposits of the Cambrian, Ordovician and Silurian, a thick sequence of continental and marine Jurassic and Cretaceous deposits (sands, loose sandstones, shales with interlayers of brown coal), in the Nizhnealdanskaya depression there are coal-bearing and sandy lacustrine-alluvial neogene deposits. Particularly widespread coal accumulation occurred in the Lower Cretaceous. The thickness of the Mesozoic rocks reaches 200-300 m. Among the loose Quaternary deposits (lacustrine-marsh, loess-like, etc.), lenses of fossil firn or lacustrine ice have been preserved, they thaw and subsidence filled with water is formed.
A large number of lakes are scattered throughout the Leno-Vilyui lowland, on watersheds and in valleys. For the purpose of economic use, the local population lowers lakes into rivers. Beautiful meadows used for mowing and pastures, the so-called alas, form in the lake basins.
The climate is sharply continental. In winter, cold air flows into the Leno-Vilyui lowland, here the air cools and an anticyclone weather regime develops. Therefore, the winter is very severe and cruel, with the temperature of the coldest month -35 -45°C, moderately snowy. The duration of the snow cover is about 220 days, and the height is -20-40 cm. Summer is warm, slightly dry and arid; the average temperature in July reaches +18°C in Vilyuisk, and +18.8°C in Yakutsk. The sum of active temperatures is 1200-1400°C. The annual amount of precipitation decreases from west to east: in Vilyuisk 2.46 mm falls, and in Yakutsk - 192 mm, the moisture coefficient is -0.77 -0.55, N=15 - 26.
The entire territory is covered with larch forests, under which predominantly permafrost-taiga carbonate soils are developed, which are formed on carbonate rocks. on the Leno-Vilyui lowland, forests are often swampy. Larch-pine and pine forests are widespread on the sandy terraces of the valleys. Permafrost-taiga fawn (neutral) and solodized soils have formed under the forests. On the terraces of the valleys of the Lena and Vilyui rivers, among the larch taiga, there are patches of meadows, among which alasses are especially peculiar. Alas vegetation consists of fescue, bluegrass, sedge and a large amount of herbs. Some of the alasses are covered with solonchak meadows (turans) formed on the site of lakes.
The vegetation of saline meadows consists of saltworts. There are salt licks and solods. Steppe meadows with dark-colored meadow-chernozem loamy soils containing up to 12-17% humus are common on the floodplain terraces of the Lena. Their vegetation cover is formed by hairy feather grass, fescue, thin-legged, xerophytic forbs: Siberian edelweiss and speedwell. Among the wall types there are local Siberian species, whose origin is associated with the mountainous regions of Siberia, and Mongolian species, which came mainly from Central Asia in one of the xerothermic periods.
The Aldan socle taiga mountain-tundra plateau occupies the southeastern part of Central Siberia, between the Lena and the Stanovoy Range. In the Aldan Highlands, the ridges rise up to 1800-2300.
The Aldan socle plateau is a reflection in the relief of the Aldan shield, which is composed of crystalline and metamorphic rocks of the Archean. They are covered from the surface by sedimentary rocks of the Lower Cambrian and continental sediments of the Jurassic and Lower Cretaceous. The Aldan Shield is riddled with intrusions of various ages. Mesozoic deposits on the shield occur in the Predstanovoy trough, which is a zone of deep basement subsidence, where the thickness of Mesozoic coal-bearing sediments reaches up to 750 m. A large fault passes in the south of the trough, separating the Stanovoy Range from the Aldan Highlands. In the relief, the fault line is expressed as a ledge.
To the north, the Archean rocks submerge under the predominantly carbonate sequences of the Lower Cambrian, gently dipping to the north. There are patches of Jurassic deposits on the surface of the Cambrian. The slope of the Aldan shield in the relief is expressed by the Lena-Aldan erosion layer-tier plateau, on which heights of 500-600 m prevail, reaching 700-1000 m in some areas. Ancient and modern karst processes occurring in Cambrian rocks are widespread on the plateau. In the Pliocene-Quaternary, the Aldan Highlands experienced a greater uplift than the Lena-Aldan Plateau. Uplifts caused a revival of erosion and dismemberment of the territory.
The rivers are deeply incised: they have up to 4-8 accumulative and socle terraces (Olyokma, Lena, Aldan). Within the region, four leveling surfaces are distinguished (the highest is 1000-1300 m, the lowest is Lenskaya-300-400 m). Traces of ancient glaciations are expressed on the ridges of the Aldan Highlands with absolute elevations above 1200-1300 m.
The climate is cold and cold-temperate with an average January temperature of -32, -40°C, with a long snow cover of 220-240 days. Summer on the Leno-Aldan plateau is warm, humid and semi-humid, the average July temperature is above +16°C; in the Aldan Highlands - cool and excessively humid; the average July temperature is about +12°С. The sum of active temperatures is 1200°-1400°C, the humidification coefficient is 1.33-1.00. Annual precipitation is 200-300 mm on the Lena-Aldan Plateau and 400-500 mm on the Aldan Highlands, N = 9-4.
On the Lena-Aldan plateau, larch middle taiga forests on permafrost-taiga pale (neutral) and solodized soils predominate. Along the river valleys there are larch-pine forests and patches of meadow steppes (Amga valley). The Aldan Highlands are dominated by mountain-larch and larch-cedar forests on mountain permafrost-taiga soils and mountain permafrost-taiga carbonate soils. Forests rise along the slopes of the ridges to a height of 1200-1300 m. Above the slopes and peaks are covered with mountain tundra on mountain-tundra soils.
The Sayan southern taiga and forest-steppe erosional plateau with a cover of loess-like rocks lies in the foothills of the Eastern Sayan. highest height the plateau reaches in the foothills (550-760 m). To the north and northeast, the territory drops to 500 m. The lowest parts of the region (200-240 m) are located in the area of the city of Kansk. The region is located on the southern outskirts of the Siberian platform - in the Irkutsk amphitheater, where three geostructures are distinguished: the Sayano-Yenisei and Baikal-Lena syneclises and the Angarsk anteclise separating them. Along the northern foot of the Eastern Sayan stretch the Mesozoic depressions - the Cape and Irkutsk, filled mainly with terrigenous coal-bearing deposits of the Jurassic age; The Cape depression continues to the west, beyond the Yenisei, and is united by the common name of the Kansk-Achinsk depression.
The coal and lignite deposits of the Kansk-Achinsk and Irkutsk basins form the Kansk-Irkutsk coal-bearing province.
The climate is sharply continental, semi-arid: the amplitude of absolute temperatures is about 84°С (-51°С +33°С). Winter is very cold, quite snowy in the west and moderately snowy in the east with an average January temperature of -20, -25 ° C. Summer is warm, the sum of active temperatures is 1400-1600 ° C, the duration of the frost-free period is from 72 days in the northeast of the region to 106 -111 days in the Cape forest-steppe. Precipitation per year is 300-400 mm, the moisture coefficient is 1.00-0.77. Permafrost islands are rare.
Among the southern taiga pine forests there are areas of steppes and steppe meadows: their distribution is associated with a dissected relief and the degree of moisture. Significant areas are covered with larch-pine forests on soddy-podzolic soils. Spruce-fir forests of the southern taiga type occupy the northern territories and are found along the valleys. Pine forests of forest-steppes on watersheds and slopes are sparse and with a high grass cover, birch forests with an admixture of larch cover the slopes of the northern exposure, and sometimes watersheds.
The forest-steppes occupy the lower parts of the plateau (the Cape Basin) and the slopes of the valleys of the Oka and Angara rivers (the Irkutsk and Balagan forest-steppes). The steppes are dominated by perennial turf grasses (fine-legged fescue, hairy feather grass, wormwood) and herbs (veronica and cinquefoil). The species composition of the steppes of Central Siberia is somewhat different from the steppes of Western Siberia: many species are absent, for example, tavolzhanka, but mountain-steppe ones appear, for example, edelweiss. Leached chernozems predominate, and on the outskirts - gray forest slightly podzolic soils. Meadow saline soils are developed in logs.
Conclusion
On the basis of the studied material, it can be concluded that the Central Siberian Plateau is a formation that is complex in terms of relief and history of formation. On its territory there are both plateaus and mountains with steep river valleys and narrow watershed ridges. So, the Putorana Plateau is the highest part of the Central Siberian Plateau.
The Central Siberian Plateau is characterized by river valleys with well-defined terraces and numerous shallow valleys. The presence of terraces testifies to the slow movements of the earth's crust that took place on the territory of the plateau.
The climate is sharply continental. Permafrost is ubiquitous. The formation of permafrost occurred during the Ice Age. Permafrost is a legacy of the Ice Age. The Central Siberian region has a rich material and raw material base, sufficiently prepared for industrial development. The water resources of the Central Siberian Plateau are one of the most valuable natural resources. Resources groundwater can be renewed in accordance with the natural cycles characteristic of a particular climatic zone, the geological structure and landscape features of the territory.
Physical and geographical conditions, the considerable length of the Central Siberian Plateau, the complexity and dissection of the relief determine the diversity of natural zones. The natural zones represented by the forest-tundra and taiga are integrated ecological complexes that arise when plants and animals interact with the environment. Each of the zones is characterized by its own set of plant life forms and a specific dominant form.
Weekly tour, one-day hiking trips and excursions combined with comfort (trekking) in the mountain resort of Khadzhokh (Adygea, Krasnodar Territory). Tourists live at the camp site and visit numerous natural monuments. Rufabgo Waterfalls, Lago-Naki Plateau, Meshoko Gorge, Big Azish Cave, Belaya River Canyon, Guam Gorge.
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, in 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 transport system 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 of 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 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. In the Arctic desert live: 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 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 the melting 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 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, and 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. Northern band of rare-layer wetlands scaffolding is coming 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 diverse and rich animal world than the 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 - marshy 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.
Physical geography of Russia and the USSR
Asian part: Central Asia and Kazakhstan, Siberia, Far East
Northeast Siberia
general characteristics
A vast territory lying to the east of the lower reaches of the Lena, north of the lower reaches of the Aldan and bounded in 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 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 is replaced here 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 Yano-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 sediments, and the Jurassic formations 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. 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
The traces of mountain-valley glaciation are much better expressed 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 conifers appeared in the composition of forest vegetation, including the Daurian larch that is now dominant.
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 severe, 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. In addition, the processes of nivation, solifluction, and frost weathering are of greater importance 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.
In accordance with the morphogenetic features 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 deposits - alluvial, lacustrine, marine and glacial. They are characterized by slightly rugged topography and slight fluctuations in relative heights. Forms that owe their origin to permafrost processes, large ice content of loose deposits and the presence of thick underground ice are widespread here: thermokarst basins, permafrost heaving mounds, frost cracks and polygons, and on the sea coasts, high ice cliffs are intensively collapsing (for example, the famous Oyegossky Yar with a length of more than 70 km).
Accumulative plains occupy vast areas of the Yana-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 are 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 Uplands, 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, some of which have been preserved here 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 activity of Quaternary and modern glaciers played the most significant role in the formation of the alpine relief, 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 thick that even in the daytime 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 higher pressure over the northern seas. 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 temperature in July 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. A certain role in the nutrition of rivers is played by groundwater and the melting of "eternal" snow and glaciers in 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 characterized 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-grade forests of the northern taiga appearance 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 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 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. The total length of currently operated waterways is 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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