The main types and forms of relief in the region are the result of prolonged geological development of the territory, tectonics, combined with the complex composition of the lithology of rocks and the active participation of various physical-geographical processes. All of this has determined the complex diversity of the surface structure of the Chuy Valley and its mountainous framing.
On the geomorphological map included in the Atlas of the Kyrgyz SSR (1987), P.G. Grigorenko, along with other authors, identified types of relief grouped into three main genetic categories: tectonic-denudational mountainous, tectonic-denudational-accumulative foothill, and tectonic-accumulative plain.
In the Chuy Valley and its mountainous framing, the following relief complexes are clearly distinguished: mountain tectonic-denudational, foothill tectonic-denudational-accumulative, and plain tectonic-accumulative. Each complex represents a combination of types and forms of relief characterized by specific morphometric features and morphological signs, and differs in its economic significance.
The mountain complex is further divided into the following types of relief:
• Dissected glacial highlands;
• Dissected erosional mid-mountains;
• Erosional low mountains - foothill uplands.
The dissected glacial highlands occupy the axial parts and lateral ridges of the Kyrgyz Ala-Too at elevations of more than 3500-4000 m. The northern slopes of the Kyrgyz Ridge are divided into three unequal parts: central, eastern, and western, based on the nature of glaciation and orography (S. Maximov, A. Osmanov, 1995).
The external contours of the relief are sharp, with steep slopes and sharp rocky peaks. Along the northern slope of the ridge, a continuous chain of cirques can be observed - huge bowl-shaped depressions formed by glaciers, measuring up to 400 m, sometimes more than 600 m in diameter. They are often multi-chambered and contain glaciers. Frequently, as the back walls of opposing slopes converge, the cirques form a saddle in the watershed ridge, or when the walls of three or four cirques converge in the middle, a rocky peak remains - Karling.
Traces of past Quaternary glaciation, in the form of cirques, trough valleys, morainic dammed lakes, and terminal moraines, are observed in several places of the Kyrgyz Ridge. For example, from the ends of modern glaciers in the upper reaches of the rivers Shamsy, Issyk-Ata, Ala-Archa, Ak-Suu, etc., trade valleys begin with steep slopes and flat bottoms. The depth of the troughs is usually 150-200 m. In their lower parts, the troughs are to some extent disrupted by post-glacial erosion. Troughs are box-shaped valleys that have partially lost their original features.
At the lower end of the troughs, there is also a pile of moraines forming significant height steps. Among the morainic formations, terminal moraines hold a special place. They usually represent irregularly bulging elevations, stones - "heads," rising several tens of meters above the valley level. Often, terminal moraines are associated with ridge-like steps.
Dammed lakes formed by terminal moraines are also found, which were described by S. Maximov and A. Osmanov (1995).
The dissected mid-mountains are widely distributed in the Kyrgyz Ala-Too and occupy altitudinal limits of 2100-3200 m. In the central and western parts of the ridge, they directly adjoin the highland relief, while in the eastern part, they are represented by more or less independent mountain masses (Oktorok, Baibichenin Soorus, Kok-Jon, Gagyzgan-Choku, etc.). The mid-mountains are characterized by more rounded, soft contours, but at the same time, they are intensely dissected by a network of grand canyons, reaching depths of up to 500-700 m or more. The areas of maximum height of the mid-mountains, represented in the central part of the ridge, are distinguished by the greatest depth of dissection.
The considered relief, depending on the nature of geological structure and relief, is divided into two subtypes:
• Mid-mountains on a loose Paleogene-Neogene foundation. Developed in the interfluves of Shamsy - Kyzyl-Suu. The relief is generally uniform, valleys are relatively wide, interfluves are hilly, dissected by shallow ravines;
• Mid-mountains on a solid Paleozoic foundation. Characterized by a greater diversity of relief forms. The relief features denudational surfaces. The valleys of rivers are canyon-shaped, their slopes are steep, often rocky.
Foothill complex.
Along the northern slope of the Kyrgyz Ridge, one or sometimes two chains of low foothills stretch - shelves, interrupted (dissected) by the canyons of rivers flowing from the main ridge. The shelves are separated from each other and from the main Kyrgyz Ridge by depressions filled with modern Quaternary deposits.
It should be noted that the shelves are not developed everywhere. In the western part, extending east to the Ak-Suu River and at the very eastern end of the Kyrgyz Ridge, they are almost unexpressed, while in the middle part, where they are developed, the slopes of the Kyrgyz Ridge are pushed further north. For example, south of the city of Bishkek, the shelves are represented by a double strip - the first and second shelves, sometimes gradually transitioning into each other, sometimes separated by longitudinal depressions and separated by a similar depression from the underlying Paleozoic slope of the ridge.
The rivers flowing from the Kyrgyz Ridge cut the ridges of the shelves into a series of separate masses with heights of 1150-1850 m, extending south of Bishkek. The first shelves, for example, include the elevations of Baytik, Bozboltok, Besh-Kungay, Chon-Daly (Serafimovka), Noruz, and others. The width of this chain varies from 5 to 7 km. South of the first shelves, a depression, 3-4 km wide, called the Baytik-Toguz-Bulak Basin, with heights of 1030-1450 m, stretches. Then begins a sharp, rocky ascent to the second shelves, reaching an absolute height of 2201 m at the Shakule Mountain. A small depression separates the second shelves from the main Kyrgyz Ridge (Fedorovich, 1931). The described shelves of the foothills gradually descending to the west eventually disappear under the Quaternary deposits of the Chuy Valley.
The slopes of the foothills are dissected by river valleys with varying depths from 300 to 500 m, many of which resemble canyons. Within the low foothills, anthropogenic forms of relief have developed significantly: quarries, channels, terraced slopes, roads, dams, dikes, graves, and others.
Research by S.S. Shultz (1948) showed that the ridges of the foothills represent anticlinal folds created by alpine orogenesis and complicated by faults, with folding affecting not only the Cenozoic sedimentary layers but also their Paleozoic foundation. In the dome-like parts of the ridges, denudation has already brought this Paleozoic foundation, composed of more resistant rocks, to the surface. In the eroded wings, Cenozoic rocks are exposed in the depressions, covered by Quaternary deposits.
Plain / tectonic-accumulative / complex.
This complex corresponds to the bottom of the Chuy Valley with the relief of river terraces, leaning against and overlapping the foothill fans. The bottom of the valley structurally represents a subsidence of the Paleozoic foundation, deeply buried under the layers of Quaternary deposits. S.S. Shultz (1948) dates the beginning of the formation of this subsidence to the beginning of the Paleogene. I.S. Shchukin (1983) notes that in the buried Paleozoic foundation, the tectonic relief is expressed in the form of second-order basins, separated by ridges. With the onset of the Alpine orogenesis in the Neogene, high mountains rose around the Chuy Basin, and it, as a platform structure, transformed into an asymmetric foothill subsidence. According to electrical exploration conducted in the Chuy Basin in 1944, the depth of the Paleozoic foundation in the area of Bishkek turned out to be more than 1 km. From here, towards the north, this depth decreases significantly. As for the reflection of recent movements of the Earth's crust on the surface of the Chuy plain itself, they are not very noticeable due to the very small angles of slope of the surface.
The transition from the foothills to the bottom of the basin occurs either gradually or in the form of a distinctly expressed step. The frequent gradual transition is explained by the fact that at the foot of the foothills, a strip of sloping to the axial part of the valley of the submontane plain or foothill fan adjoins.
Within the plain complex of the Chuy Valley, the following types of relief are distinguished: the foothill fan (foothill plains);
• Sloping proluvial-alluvial plains;
• Flat alluvial plains.
The foothill fan is developed along the entire length of the northern slope of the Kyrgyz Ridge and covers heights from 800 to 1200 m above sea level. Composed of merging and partially overlapping alluvial cones, the area represents a wavy strip in longitudinal profile (in relation to the foot of the mountains), gently sloping northward. The slopes of the fan vary from 11° - 8° to 6°-3°.
The surface of the foothill fan in the upper part is wavy due to the alternation of convex surfaces of alluvial cones and inter-cone depressions. Only in the interfluves of large rivers is this waviness of the relief weak or not expressed at all.
In morphological terms, the foothill fan is divided into:
• Alluvial cones of rivers with terraced surfaces and significant dissection along the axis of the cone by the modern river valley. This subtype includes alluvial cones of such large rivers as: Shamsy, Kegety, Issyk-Ata, Ala-Archa, Sokuluk, Ak-Suu, and others. The depth of the valley incision is 10-15 m, sometimes up to 30 m, and the width of the valley is 100-200 m. Distinct steps of river terraces are clearly expressed (from 2 to 5);
• Alluvial cones of rivers with weak vertical and horizontal dissection of the surface. Terraces are either absent or located at a great distance from each other. They are characteristic of such small rivers as Kyzyl-Suu, Alchal, Noruz, Zhilamish, Kichi-Kayindy, and others.
The foothill fan is composed of proluvial-alluvial deposits with clearly expressed layering. These deposits easily absorb water from rivers flowing out of the mountains. The absorbed water continues to flow as an underground sheet flow and re-emerges at the surface in the form of numerous springs (Kara-Suu) below the Tashkent-Bishkek-Chaldovar highway.
The sloping proluvial-alluvial plain serves as a direct continuation of the foothill fan, from which it is separated by a wide strip of groundwater outflow, creating significant swampiness. The surface of the plain is characterized by slight slopes and gently sloping relief. Its eastern boundary runs in the area of the city of Tokmok. To the west, it expands to 10-15 km and occupies the entire central part of the Chuy Basin. The altitudinal marks of the plain at the boundary with the foothill fan range from 850-800 m in the east to 600-600 m in the west (at the confluence of the Ak-Suu River into the Chuy River). A characteristic feature of the plain is the predominance of transverse slopes (from south to north) over longitudinal slopes (from east to west). Its surface is dissected by numerous rivers, valleys of spring streams - karasuu, and a branched network of irrigation canals. The surface of the plain is also characterized by the alternation of slight elevations and depressions. The latter include quite numerous, usually wide (up to 0.5 - 1 km), linearly elongated dry "deltas".
On the surface of the plain, south of the Atbashinsky Canal, aeolian forms of relief are insignificantly developed. Semi-fixed sands form ridges and mounds 3-5 m high, sometimes up to 10-12 m, oriented from northeast to southwest. This relief is subject to wind deflation.
The undulating-valley and hilly-upland relief is widespread in the northwestern part of the Chuy Basin, between the Sary-Goo gorge and the Kuragaty River. Small areas are found in the lower reaches of the Ak-Suu - Kara-Balta and Ala-Archa - Alamudun rivers. Against the background of the plain, the slightly hilly plateau-like elevation of Sary-Goo stands out. The altitudinal marks of the relief vary within relatively small limits, in the lower reaches of the Ala-Archa - Alamudun rivers 700-600 m, and in the area of the Kuragaty River 600-570 m. The relief features more or less correctly oriented systems of parallel, almost meridionally elongated river valleys, flowing either into the Chuy River valley or into the Kuragaty River valley. The valleys are directly connected with mountain rivers flowing from the Kyrgyz Ridge or with spring streams originating on the periphery of the foothill fan. All valleys are terraced. The inter-valley areas represent fairly high mounds with a slightly elevated surface. Powerful layers of loess-like silty clays are widely distributed, and surface water flows are poorly developed. There is also a development of ravines with blind beginnings. Their sizes vary, with both large (Syrdybay, Sary-Goo, Kuruk-Goo, etc.) and small feathery ones. They complicate the mounds and create relief forms reminiscent of landscapes of finely dissected low uplands with soft contours.
The sloping plain is the most favorable for conducting any branch of the economy, especially for mechanizing all field works.
Flat alluvial plains occupy the lowered part of the Chuy Basin and extend in the form of terraces, floodplains along the Chuy River and its major tributaries. The width of the plain ranges from 1.5 to 3 km, but in most cases is 1-1.5 km. Absolute heights decrease in the direction of the river flow from 800 to 850 m at the city of Tokmok, in the east to 670 m, in the west (at the confluence of the Ak-Suu River into the Chuy River). The number of terraces reaches 4-5, with low terraces predominating. They are traced throughout the length of the Chuy River valley. The modern floodplain is predominantly expressed in the central and western parts of the Chuy River valley. Its surface is covered with thickets of shrubs.
Three sections are distinguished in the Chuy Valley based on the nature of the relief:
• Eastern (to the east of the city of Tokmok);
• Central (between the city of Tokmok and the Chumyshev (Chemych) dam);
• Western (Chumyshev-Tashatkulskiy).
The eastern section is characterized by a poorly developed floodplain. Between the exit from the Boom Gorge and the village of Kemin, 5 above-floodplain terraces are traced in the cross profile at heights of 5, 10, 20, 40, and 60 m above the level of the Chuy River (Ibrahimov, 1975). In the area of the village of Novorossiysk, 3 lower terraces are developed on both banks of the Chuy River. Downstream, there is a sequential retreat from the river, a decrease in height, and increasing smoothness. West of the village of Kemin, the Chuy River expands. The floodplain develops significantly, reaching more than 1 km in width in places, and the Chuy River itself splits into wandering channels and streams.
In the central section, the floodplain and low terraces are widely developed, almost everywhere swampy. In places along the edges of the Chuy River valley, small areas of high fourth and fifth terraces have been preserved. They are home to the villages of Ken-Bulun, Ivanovka, Black River, and others.
The western section of the Chuy River valley resembles the central one in its external appearance. Here, too, large areas are occupied by low swampy terraces and floodplains; the third and fourth terraces are widely distributed, on which irrigated fields and numerous settlements are spread.
The surface of the alluvial plain (terraces, floodplains) is weakly dissected by streams, ravines, irrigation, and river networks, the slope is expressed weakly, and the conditions of the relief are more favorable for economic use. Significant areas of swampy territories have now been drained. The silt and silt meadows are used as natural hayfields and pastures. Erosion processes are weakly formed.
Anthropogenic forms of relief.
In the territory of the Chuy Valley, under the influence of human economic activity, the following forms of anthropogenic relief are distinguished: agricultural, road, hydraulic engineering, construction, protective-defensive, archaeological, mining-geological, and pasture.
The most widespread forms of relief at the bottom of the valley are agricultural forms. These include arable land and irrigation canals.
Arable land, as forms of relief, includes all plowed lands, including gardens, grasses, as well as areas occupied by fruit orchards. When plowing or planting garden crops, the appearance of the relief changes completely, and the natural vegetation disappears.
Large irrigation canals are the main water arteries from which numerous smaller irrigation networks branch off. They begin at the exits from the mountains of all more or less large rivers of the Kyrgyz Ridge, with each river having not one but several canals branching off. For example, from the Ala-Archa River, 1 main canal is diverted at the mouth of the Ak-Suu River, and 1-2 canals are laid for Shamsy, Issyk-Ata, Alamudun, etc. Thus, canals and ditches form a dense irrigation network.
Road forms of relief include railway embankments, highways, dirt roads, and mountain trails, as well as various earthworks, pits, and holes associated with road construction.
The railway, running from Kainy to Bishkek and east to Kemin parallel to the Kyrgyz Ridge, crosses many ravines, river valleys, and elevations. When laying the roadbed, large earthworks had to be carried out: embankments were built in depressions of the relief, sometimes more than 8 meters high, bridges were built, drainage pipes were laid, etc. In elevated places, deep excavations were made, resulting in steep and exposed slopes. In addition, along the road, excavation of the embankment was sometimes carried out. Railway embankments, resembling natural ridges, prevent surface runoff of water, directing it along the roadbed to depressions in the relief. The place of excavation of the embankment or pits located along the road becomes, as it were, collectors of atmospheric precipitation, and often ravines arise on their slopes. In places where bridges are built, the valley narrows and river waters are dammed, disrupting the natural development of the valley.
Due to strict control and maintenance of railways, destructive processes such as landslides and ravines hardly occur here.
Highways have developed widely, both in the plains and in the foothills. From Bishkek, many roads branch off in different directions (including into the mountains). These are main roads (bypass), going east, west, and north. A good highway stretches almost to the alpine camp of Ala-Archa along the Ala-Archa valley.
Many roads are found in the basins of the Issyk-Ata, Kara-Balta, and Shamsy rivers. All of this has led to significant changes in the natural relief in the areas of the route.
Dirt roads and trails have the most branched network, both in the plain part and in the mountainous territory. Most often, these are dirt roads connecting settlements with district centers.
Hydraulic engineering forms of relief are associated with the construction of reservoirs, dams, and other irrigation structures.
In the foothills of the Kyrgyz Ala-Too, many reservoirs have been created, which play a significant role in regulating the water regime of rivers used for irrigating fields, protecting against floods and mudflows, and for fish farming, etc. Reservoirs can also be used for organizing recreation for people. Most often, reservoirs in the valleys of Ala-Archa, Alamudun, Kara-Balta, Sokuluk, Chuy, and others are used for such purposes.
To construction forms of relief belong the territories of settlements, various pits, holes, quarries that arose in connection with construction works. The entire set of anthropogenic forms of relief arising from the construction of cities and villages is grouped under the general name - the relief of settlement landscapes, as it is impossible to distinguish each form. Such relief is characterized by its diversity. These are leveled, often covered with asphalt or cobblestones streets and squares, various pits, drainage channels, bridges, crossings, roads, small quarries. Fruit and decorative gardens, plowed areas for gardens, ditches, dams, and dikes are widely spread in settlements. In short, one can find a large number of very diverse forms of anthropogenic relief in settlements.
The foothills and foothill plains of the Kyrgyz Ridge are very rich in construction materials - stones, brick clay, gravel, sand, and others. Gravel is especially intensively extracted for road covering, and loess-like silty clay is used for brick production. Therefore, we often encounter quarries - places for the extraction of construction materials. There are many of them near large settlements such as Bishkek, Tokmok, Ivanovka, Kara-Balta, Belovodsk, and others. Quarries represent huge pits with vertical walls, sometimes terraced or multi-chambered, with depths reaching dozens of meters. In the southern part of Bishkek, there is a large boulder-gravel quarry. Its length is more than 1.5 km, width about 1 km, and depth 40-50 m. Quarries significantly change the appearance of the natural relief.
To protective-defensive forms of relief belong various earthen boulder-gravel dikes, dams, cement barriers against mudflows, floods, and slope erosion. They are mainly distributed in the valleys of rivers in the central and eastern parts of the ridge.
Many channels, ditches, and mountain roads are reinforced against erosion and destruction with gravel masonry, cement slabs, and gutters.
Protective-defensive forms of relief play a significant role in preserving slopes from destruction, from mudflows and floods, although they themselves also introduce a number of changes into the natural environment. For example, during the construction of an explosive dam in the Ala-Archa River valley, a significant number of trees on the slopes of the mountains were destroyed, and some slopes became exposed and are constantly eroding.
Archaeological forms of relief. The foothill zone of the Kyrgyz Ridge has long been a region of human settlements. Traces of human activity have been preserved to this day in the form of remnants of dwellings, burial structures, mounds, etc. Very characteristic and widely distributed forms are mounds - artificial structures resembling conical hills. They are especially numerous in the areas of Bishkek, Sokuluk, Belovodsk, Tokmok, and others. They are often located in groups near rivers. Their height usually reaches 5-10 m, and the diameter of the base ranges from 15-20 to 80-100 meters.
In addition, in the central part of the valley, burial grounds or cemeteries and remnants of abandoned settlements, usually built of clay and stone, are often found. For example, the remnants of auls located in Ak-Beshim, Krasnaya Rechka, as well as the mounds and graves of the Batyr Baytik and the Burana tower.
Mining-geological forms of relief are formed in connection with the exploration and development of mineral resources. In particular, the Kyrgyz Ridge is significantly characterized by exploratory and operational quarries, adits, trenches, shafts, and dumps. They are known in the valleys of Shamsy, Issyk-Ata, Ala-Archa, Sokuluk, and others. Adit tunnels are usually laid on the slopes of mountains and resemble caves, their length reaches hundreds of meters. Terraced slopes of mountains are sometimes found in the valleys, where paths for trolleys are laid. All these mining-geological anthropogenic forms of relief introduce significant diversity into the morphology of mountain valleys and to some extent disrupt the stability of the relief of mountain slopes.
Pasture forms of relief are represented by terraced slopes of mountains and valleys, numerous roads and trails along which livestock is driven. Cattle-driving paths and trails are especially common in the eastern and western parts of the ridge, mainly in the basins of Shamsy, Kegety, Ak-Suu, Kara-Balta, and other rivers. Terraced slopes, or so-called cattle-driving trails, are so frequent that in places the slopes of the valleys resemble plowed fields. Often, atmospheric precipitation, flowing down them, develops gullies.
Thus, in the territory of the Chuy Valley, anthropogenic forms of relief have become very widespread, especially in the foothill plain, where the main economic activity of humans is concentrated. The most widespread artificial forms of relief have emerged in recent decades due to the intensive development of natural resources (land, minerals) in this foothill area and the use of powerful modern agricultural and construction machinery.