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Alluvial plains. Alluvial plain See what “Alluvial plains” are in other dictionaries

– this is a large space, the height of adjacent areas practically does not differ from each other. For example, we can cite the vast West Siberian Plain. The plains themselves differ from each other in structure and formation. Therefore, plains as one of the landforms can also be divided into groups. Most often, plains are divided into groups according to the height of a particular hill. Plains with a height from 0 to 200 m are classified as lowlands, plains from 300 to 500 m are called uplands, and plains above 500 m are classified as plateaus. Also, when determining the type of plain, the genesis of the plain, i.e. origin, plays an important role. Alluvial plains are those plains that are formed by the deposition of river water and sediment. Alluvial plains can also be divided into two groups: fluvial and deltaic. Based on all this, we can conclude that alluvial plains are formed with the help of river activity. Such plains are usually formed from the surface by river sediments, and the thickness can reach hundreds of meters. Examples of alluvial plains are the Hungarian lowland, the valleys of the Po and Ganges rivers.

Let us consider in more detail the formation of alluvial plains. Alluvial plains formed through river activities: erosion, transport and deposition. The slow flow of the river leads to the fact that various natural materials are deposited, since at low speeds in the river they are not transported lower. Typically slow flow occurs at the mouth and downstream. The sediments produced by river waters are called alluvial sediments or alluvium. The formation of deltaic plains occurs in the lower reaches of rivers during the process of delta growth. A delta is an area of lowland that was formed from sediments formed during the operation of rivers, and this area may previously have been occupied by a sea or a lake. Typically, deltaic plains consist of loose and fine deposits of sand and silt, but at the mouths of rocks, deltaic plains can be formed from pebbles, gravel, i.e., large clastic rocks predominate. River channels that cross delta plains are usually very shallow in depth. Also, rivers with delta plains are characterized by a change in channels, which forms undulating surfaces and various river-bed levees. An example of deltaic alluvial plains are the deltas of the following rivers: Kuban, Yellow River, Nile, Amu-Daria, Ganga and Brahmaputra. Delta plains can be very large, ranging from 10 to 445 thousand square kilometers. The most common are fluvial alluvial plains. They are everywhere where there are rivers. If river valleys are deep, then usually river plains will be located along the rivers. The plains of the Middle and Lower Tunguska and Angara have this location. If the river is located in a low area, then very wide plains will form there.
The reason for the formation of wide areas of lowlands may be the slow flow of the river. Delta and river alluvial plains became the habitat of ancient man, and also served as a place for the formation of ancient human cultures. Alluvial deposits can form very large sea bays when river activity is very long. For example, such plains can include the Lombard and Rion lowlands and the Kuban River delta. In addition to river and delta plains, piedmont alluvial plains are also classified as alluvial. Their origin, which can also be understood by their name, is associated with the mountains. The formation of alluvial piedmont plains is explained by the fact that mountains tend to rise, and piedmont depressions descend, as a result of which thick Quaternary deposits, i.e. alluvium, accumulate. Examples of piedmont plains are: the Cis-Caucasian piedmont alluvial plain, the plains of Altai and Tien Shan. The largest alluvial plain on Earth is the West Siberian Lowland. Looking at it in more detail, you can see that it is not the same in its formation and structure. For example, sediments located in the Kulandinskaya and Barabinskaya steppes are formed at a height of 200 to 300 m. These sediment strata are formed mainly by the river activity of the Altai rivers. The Kulandinskaya and Barabinskaya steppes are areas of foothill depression, since the accumulation of sediment layers caused the subsidence of this area. The middle West Siberian Plain has small deposits of about 20-30 m. Alluvial sediments of the Irtysh and Ob rivers are mainly distributed in this part. In the northern regions of the West Siberian Plain, morainic deposits are very common, which are exposed to the influence of rivers.

The accumulative alluvial plain consists of alluvial terraces of various ages and heights above the low-water level of the river. The collection of alluvial terraces forms the bottom (bottom of the river valley). The outer boundary of the valley floor coincides with the rear suture of the highest alluvial terrace. The slope of the bedrock bank towards the valley bottom is called the valley side. It is composed of bedrock, rocks and sediments of non-alluvial origin.[...]

An example is loess plains with ribbon forests. Alluvial plains of the Don and its tributaries with pine forest terraces, landscapes of opoles and overflows in the south of Russia with alternating plowed plains and forest slopes.[...]

Saline soils are widespread on the alluvial plains of many large rivers, such as the Volga, Don, Dnieper, Irtysh, Amu Darya, and in lakeside depressions on coastal alluvial plains and ancient terraces. Saline soils here are also confined mainly to negative forms of relief. They abound in estuaries, oxbow lakes and various depressions.[...]

In the north of the interfluve, flat and flat-ridged lacustrine-alluvial plains predominate, usually in combination with numerous depressions. In the southern part of the interfluve, the main type of relief is flat and terraced lake plains. Some scientists attribute the south of the Ubagan-Ishim interfluve to the West-North. lowlands (Nikolaev, 1992), others (Natural zoning I960) consider it as the northern edge of the Turgai plateau (pre-Turgai plains).[...]

Western Siberia in terms of relief is a flat accumulative plain. Here there are only isolated hills of tectonic or glacial-tectonic origin. Their area is small; genetic types of flat relief predominate - fluvioglacial and alluvial plains. The general flatness is combined with an abundance of depressions, many of which are peat lakes or beds of an ancient river network. Lake basins are genetically mostly glacial-tectonic, glacial, water-glacial, karst, fluvial (floodplain) and aeolian (Zemtsov, 1976). The establishment of the river network in this territory occurred in the early - early middle Pleistocene, and its formation - in the late Pleistocene. A significant part of this decrepit and hydrologically inactive river network on flat interfluves was also a focus of active peat accumulation in the Holocene.[...]

A group of tracts of the main slightly undulating surfaces of loamy lacustrine-alluvial plains is formed under conditions of optimal atmospheric moisture and drainage.[...]

On the other hand, large deltas and even entire alluvial plains are mainly built from river sediments. The study shows that the water arteries that accumulated them were characterized by high turbidity. Nowadays, such deltas, in the presence of appropriate climatic conditions, are intensively plowed and cut through by irrigation systems. Rice cultivation and other types of crop production in the deltas of the Yellow River, Yangtze, Mekong, Salween, Irrawaddy, Ganges and Brahmaputra, Indus, Shat al-Arab, Nile and other rivers feed and provide employment to hundreds of millions of people.[...]

The depressions in which alluvial fans arise are very diverse. They may be alluvial plains or valleys (for example), drainage basins with or without tectonically active margins, and bodies of standing water such as seas and lakes.[...]

River deltas. Some rivers, when they flow into the sea or a large lake, are unloaded from transported sediment, forming low-lying plains composed of young alluvial sediments. Due to their resemblance to the capital Greek letter A, such estuarine alluvial plains were called deltas. Deltas are usually dissected by many branches and channels, heavily watered and covered with marsh vegetation. The world's largest delta - about 100 thousand km2 - is formed by the river. Amazon; river delta area Mekong - about 70 thousand km2. In the USSR, the largest is the Lena delta - about 30 thousand km2. It has more than 800 channels, the depth and outlines of which change after each flood. The Volga delta (19 thousand km2), densely overgrown with reeds, reeds and cattails, has been well studied. [...]

The Clear Fork consists of laminar mudstones, arkosic channel sandstones, and calcretes deposited on a desert alluvial plain. The distribution of the sulfate sebkha and salt basin environments was quite stable throughout the accumulation of the formation, so that significant thicknesses of anhydrite and halite accumulated during steady subsidence.[...]

Disturbed drainage network - characterized by a large transit river into which small, short tributaries flow, poorly draining the adjacent flat plain. Here the sequence of connecting watercourses of different ranks is disrupted, and elementary tributaries flow directly into a high-ranking river. Such an uncoordinated drainage network is typical for relatively young accumulative landforms that have a flat surface and a high groundwater level. These are depressions and water-logged plains with a large area of swamps and lakes. Regional rivers may pass through an area without draining it. This pattern is common for glacial and alluvial plains-depressions, composed of dense sediments of considerable thickness.[...]

The processes of swamping on heavy rocks were studied in the watershed of the Vol-Egan (tributary of the Vakh) and the Small Nai-Yakh (tributary of the Nazinskaya River, which flows into the Ob), in the Nan-Yakh area. This area is a lacustrine-alluvial plain, adjacent from the south to the western tip of the Vakh continent (Olyunin, 1977). It is confined to a large uplift - the Aleksandrovsky megaswell, but is located in its marginal part, where the wings of the uplift are noticeably smoothed out and absorbed by adjacent depressions (Boyarskikh et al., 1965; Rudkevich et al., 1965).[...]

Dilleniaceae have a wide ecological range, ranging from tropical rainforests to areas with very long dry periods. They grow on plains and hills or on small (up to 300-(500 m above sea level) heights and mountains, sometimes rising to 1000-1500 m and very rarely up to 2000 m, for example, dillsiia mountain (G), monlaua). In swampy forests, on alluvial plains, flooded during river floods, there is Dilepia reticulata (I), reticulata), which has stilted corps up to 2 m high. A remarkable feature of this tree is that stilted corps develop in it even in those cases when it grows on the slopes of dry hills, away from rivers.[...]

The zonal type of valley-river complexes (a generalized concept) finds its expression in morphological types: 1) undeveloped valleys without clearly defined differentiation into structural parts. They are known on low-lying plains such as the Caspian; 2) inversion valleys, in which the water level in the river bed, fenced by natural coastal ramparts, is higher than the alluvial plains. During floods and floods, the river often breaks through the ramparts, flooding vast areas of lowlands. Inversion valleys are rare, they are found in lowlands in the lower reaches of rivers that deposit masses of suspended material and wander in these sediments. The Yellow River is notable in this regard. Its channel is located 3-10 m above the adjacent plains, the length of the protective dams is about 5 thousand km. In the USSR, the valley of the Terek River in the estuarine part belongs to the inversion type; 3) young V-shaped valleys, devoid of a developed floodplain and above-floodplain terraces; 4) mature incomplete (slopeless) valleys, which have a wide floodplain and a series of above-floodplain terraces, but lack bedrock slopes. The upper terraces of these valleys morphologically imperceptibly transform into watersheds or themselves become such for rivers of the second order; 5) mature full valleys, characterized by a fully developed valley-river landscape complex with a developed channel, floodplain, above-floodplain terraces, steep (mostly right) and gentle bedrock slopes. [...]

Artificial drainage network - in humid regions, reclamation ditches are carried out to lower the groundwater table. The drainage network under these conditions indicates low and lowland flat lacustrine, glaciolacustrine, moraine and alluvial plains. Irrigation ditches and ditches are created in an arid climate.[...]

So, the soil cover on the territory of the study object is represented mainly by varieties of podzolic and bog types of soil formation, slightly floodplain, manifested in the conditions of periglacial terraced lacustrine-alluvial plains under middle taiga plant associations.[...]

N. A. Solntsev, S. V. Kalesnik, A. G. Isachenko). In this narrowly regional interpretation, the landscape is close to what other authors mean by a specific physiographic region.[...]

The coarse units, with their array of more characteristic sedimentary textures, have received much attention from earlier researchers, and their diversity is well documented. In contrast, sediments of the fine-grained units began to attract interest only relatively recently, as it became clear that their more subtle changes could provide deeper insight into the mysteries of paleoclimate and large-scale geomorphology of ancient alluvial plains.[...]

Upper Jurassic carbonate deposits are also widely represented on the Atlantic margin of Europe. In the Lusitanian basin of Portugal, during the Jurassic period, a strata with a thickness of up to 5000 m was formed. Despite the significant diversity of facies types of sediments, the predominant role in the sections, according to R. Wilson, obtained in 1975, is played by carbonate rocks of shallow-water origin. Coarse-grained limestone layers correspond in this case to large sand bars and oyster banks, thin-layered limestones correspond to deposits of the internal parts of lagoons and tidal platforms. Laterally, the limestones are replaced by terrigenous red rocks - deposits of alluvial plains and alluvial fans of temporary flows. Packs of deltaic sediments were also discovered here, with quite thick horizons of brown coals associated with them.[...]

Particularly thick strata of continental red rocks, ranging in age from 262 to 203 million years, were found in areas adjacent to the modern outskirts of Morocco (Moroccan Meseta and High Atlas). The thickness of only the lower strata of conglomerates and gravelly sandstones developed in the river valley. Argen, reaches, according to R. Brown, obtained in 1974, 2000-2500 m. Over time, the formation of conglomerates associated with the activity of drying up water flows was replaced by the accumulation of sandstones, siltstones and clayey siltstones of the channel and floodplain facies. The thickness of this sequence is more than 1000 m. Finally, in the Early Liassic into the river valley. Argen penetrated the sea and, under the conditions of the tidal terraces, the deposition of gypsum, dolomites and marls began.[...]

Meandering rivers are those rivers whose beds have a distinctly meandering character. Their tortuosity is usually natural, and its dimensions are related to the width of the channel. Meandering appears to be a characteristic feature of areas with slight surface slope. It is favored by the presence of a large amount of fine-grained sediments both along the river banks and in the general solid runoff. Meandering rivers exhibit a more regular nature of channel processes and a clearer separation of channel and floodplain environments than weakly meandering rivers. They are usually observed on alluvial plains, both within the boundaries of valleys or terraces, and in less restricted areas. The coastal plain of the Gulf of Mexico in the southern United States is intersected by a series of meandering rivers, each of which has its own zone of influence. At any given time, the river itself occupies only a small part of the valley or zone of influence. The channel is located within the meandering belt, which is a complex zone of active and dead channel settings and adjacent floodplain settings. Beyond the meandering belt there are more remote areas of the floodplain. With strong tortuosity of the channel, the position of the meandering belt can remain constant for a long time, since clay plugs formed when the channel channels are blocked prevent lateral migration of the channel.

ALLUVIAL PLAINS

plains, plains formed as a result of the accumulative activity of large rivers at the site of extensive subsidence of the earth's crust. They are composed of river deposits on the surface, the thickness of which reaches several tens and even hundreds of meters (Hungarian lowland, plains along the valleys of the Ganges and Po rivers).

Great Soviet Encyclopedia, TSB. 2012

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Summer came completely unnoticed. And it was this summer (according to my mother’s promise) that I was supposed to see the sea for the first time. I have been waiting for this moment since winter, since the sea has been my long-standing “great” dream. But by a completely stupid accident, my dream almost turned to dust. There were only a couple of weeks left before the trip and in my mind I was almost “sitting on the shore”... But, as it turned out, the shore was still far away. It was a pleasant warm summer day. Nothing special happened. I was lying in the garden under my favorite old apple tree, reading a book and dreaming about my favorite gingerbread cookies... Yes, yes, exactly gingerbread cookies. From a small neighborhood store.
I don’t know if I’ve ever eaten anything tastier since? Even after all these years, I still perfectly remember the amazing taste and smell of this amazing, melt-in-your-mouth delicacy! They were always fresh and incredibly soft, with a thick, sweet glaze crust that burst at the slightest touch. Stunningly smelling of honey and cinnamon, and something else that was almost impossible to detect... It was these gingerbread cookies that I decided to go for, without hesitation for a long time. It was warm, and I (according to our common custom) was wearing only short shorts. The store was nearby, literally a couple of houses away (there were three of them on our street!).

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