The lake is located in a tectonic basin. Lakes: characteristics and types. Mineralization classification

The lake is an element of the hydrosphere. This is a reservoir that arose naturally or artificially. It is filled within its bed with water and has no direct connection to the sea or ocean. There are about 5 million such reservoirs in the world.

general characteristics

In terms of planetology, a lake is an object that exists stably in space and time, filled with a substance that is in liquid form. In a geographical sense, it is presented as a closed depression of the land, into which water enters and accumulates. The chemical composition of lakes remains constant for a relatively long time. The substance that fills it is renewed, but much less frequently than in a river. At the same time, the currents present in it do not act as the predominant factor that determines the regime. Lakes provide regulation Chemical reactions take place in the waters. In the course of interactions, some elements settle in bottom sediments, while others pass into the water. In some water bodies, which usually do not have a runoff, the salt content increases due to evaporation. As a result of this process, there is a significant change in salt and mineral composition lakes. Due to the large thermal inertia, large objects soften the climatic conditions of the adjacent zones, reducing seasonal and annual meteorological fluctuations.

Bottom sediments

With their accumulation, significant changes in the relief and dimensions of lake basins occur. When water bodies are overgrown, new forms are formed - flat and convex. Lakes often form barriers to groundwater. This, in turn, causes swamping of adjacent land areas. In lakes there is a continuous accumulation of mineral and organic elements. As a result, thick strata of deposits are formed. They are modified in the course of further development of water bodies and their transformation into land or swamps. Under certain conditions, bottom sediments are transformed into mountain fossils of organic origin.

Features of education

Reservoirs occur for a variety of reasons. Their natural creators are wind, water, tectonic forces. On the surface of the earth, depressions can be washed out by water. Due to the action of the wind, a depression is formed. The glacier polishes the depression, and the mountain collapse dams the river valley. So it turns out a bed for the future reservoir. After filling with water, a lake appears. In geography, water bodies are classified depending on the method of formation, the presence of life, and the concentration of salts. Only in the most saline lakes there are no living organisms. Most of reservoirs created as a result of displacements of the earth's crust or volcanic eruptions.

Classification

According to their origin, reservoirs are divided into:

Volcanic reservoirs

These lakes are located in extinct craters and explosion tubes. Such reservoirs are found in Europe. For example, volcanic lakes are present in the Eifel region (in Germany). Near them there is a slight manifestation volcanic activity in the form of hot springs. The most common type of such lakes is a crater filled with water. Oz. The crater of the Mazama volcano in Oregon was formed more than 6.5 thousand years ago. Its diameter is 10 km and its depth is 589 m. Part of the lakes was formed in the process of blocking volcanic valleys by lava flows. Gradually, water accumulates in them and a reservoir is formed. So, for example, there was a lake. The Kivu is a depression of the East African Rift Structure, located on the border of Rwanda and Zaire. Flowing once from the lake. Tanganyika r. Ruzizi flowed along the Kivu valley to the north, towards the Nile. But from the moment the channel was blocked after the eruption of a nearby volcano, it filled the depression.

Other types

Lakes can form in limestone voids. Water dissolves this rock, forming huge caves. Such lakes can occur in areas of underground salt deposits. Lakes can be artificial. They are intended, as a rule, to store water for various purposes. Often the creation of artificial lakes is associated with various earthworks. However, in some cases, their appearance is a side effect of them. So, for example, artificial reservoirs are formed in developed quarries. Among the largest lakes, it is worth noting the lake. Nasser, located on the border of Sudan and Egypt. It was formed by damming the valley of the river. Nile. Another example of a large artificial lake is Lake. Mid. It appeared after the installation of a dam on the river. Colorado. As a rule, such lakes serve local hydroelectric power stations, provide water to nearby settlements and industrial zones.

The largest glacial-tectonic lakes

One of the main reasons for the formation of reservoirs is due to this displacement, in a number of cases, the sliding of glaciers occurs. Reservoirs are very common on the plains and in the mountains. They can be found both in hollows and between hills in depressions. Lednikovo- tectonic lakes(examples: Ladoga, Onega) are quite common in the Northern Hemisphere. Avalanches left enough deep depressions after myself. They accumulated melt water. Deposits (moraine) dammed depressions. This is how reservoirs were formed in the Lake District. At the foot of Bolshoi Arber there is a lake. Arbersee. This reservoir remained after the Ice Age.

Tectonic lakes: examples, characteristics

Such reservoirs are formed in areas of shifts and faults of the crust. Usually, the tectonic lakes of the world are deep and narrow. They are characterized by steep straight banks. These reservoirs are located mainly in through deep gorges. The tectonic lakes of Russia (examples: Kuril and Dalnee in Kamchatka) are characterized by a low-lying bottom (below ocean level). Yes, oz. Kuril is located in the southern part of Kamchatka, in a picturesque deep basin. The area is surrounded by mountains. The maximum depth of the reservoir is 360 m. It has steep banks, from which many mountain streams flow. The river flows out of the reservoir. Ozernaya. Hot springs come to the surface along the banks. In the center of the lake there is a small elevation - an island. It is called "heart-stone". Not far from the lake there are unique pumice deposits. They are called Kutkhins baty. Today lake. Kurilskoye is a nature reserve and declared a zoological natural monument.

bottom profile

The glacial-tectonic lakes of the world have a sharply defined relief. It is presented as a broken curve. Glacial deposits and accumulative processes in sediments may not have a significant effect on the clarity of basin lines. However, in some cases the impact can be quite noticeable. Glacier-tectonic lakes can have a bottom covered with "scars", They are quite well visible on the islands and rocky shores. The latter are composed mainly of hard stone rocks. They are weakly susceptible to erosion, which, in turn, causes a low rate of precipitation accumulation. Such tectonic ones are classified as a=2-4 and a=4-10. The deep-water zone (over 10 m) of the total volume is 60-70%, shallow-water (up to 5 m) - 15-20%. Tectonic lakes are distinguished by the heterogeneity of water in terms of thermal parameters. During maximum surface heating, low temperature bottom waters. This is due to stable thermal stratifications. Vegetation is quite rare. It can be found along the shores in closed bays.

Spreading

Where, besides Kamchatka, are tectonic lakes found? The list of the most famous reservoirs of the country includes such formations as:

1. Sandal.
2. Sundozero.
3. Palier.
4. Randozero.
5. Salvilambi.

These reservoirs are located in the Suna River basin. Tectonic lakes are also found in the forest-steppe Trans-Urals. Examples of reservoirs:

1. Welgi.
2. Argayash.
3. Shablish.
4. Tishki.
5. Sugoyak.
6. Kaldy.
7. B. Kuyash and others.

The depth of reservoirs on the Trans-Ural plain does not exceed 8-10 m. By origin, they are classified as lakes of the erosion-tectonic type. Their depressions were modified, respectively, under the influence of erosion processes. Many reservoirs in the Trans-Urals are confined to ancient river hollows. These are, in particular, such tectonic lakes as Kamyshnoe, Alakul, Peschanoe, Etkul and others.

Unique body of water

In the southern part Eastern Siberia lake is located Baikal is a tectonic lake. Its length is more than 630 km, and the length of the coastline is 2100 km. The width of the reservoir varies from 25 to 79 km. The total area of ​​the lake is 31.5 sq. km. This reservoir is considered the deepest on the planet. It contains the largest volume fresh water on Earth (23 thousand m 3). This is 1/10 of the world's supply. Complete renewal of water in the reservoir takes 332 years. Its age is about 15-20 million years. Baikal is considered one of the oldest lakes.

terrain

Baikal lies in a deep depression. He is surrounded mountain ranges covered with taiga. The area near the reservoir is characterized by a complex, deeply dissected relief. Not far from the lake itself, there is a noticeable expansion of the mountain strip. The ridges here run parallel to each other in the direction from the northwest to the southeast. They are separated by depressions. River valleys run along their bottom, in some places small tectonic lakes are formed. Displacements of the earth's crust take place in this area today. This is indicated by relatively frequent earthquakes near the basin, hot springs coming to the surface, as well as subsidence of large areas of the coast. The water in the lake is blue-green. It is distinguished by exceptional transparency and purity. In some places you can clearly see the stones lying at a depth of 10-15 m, thickets of algae. A white disk lowered into the water is visible even at a depth of 40 m.

Distinctive features

The shape of the lake is a crescent being born. The pond stretched between 55°47" and 51°28" N. latitude and 103°43" and 109°58" east. longitude. The maximum width in the center is 81 km, the minimum (opposite the delta of the Selenga river) is 27 km. The lake is located above sea level at an altitude of 455 m. 336 rivers and streams flow into the reservoir. Half of the water comes into it from the river. Selenga. One river flows out of the lake - the Angara. However, it should be said that in the scientific community there are still discussions about the exact number of flows flowing into the reservoir. Most scholars agree that there are fewer than 336.

Water

The liquid substance that fills the lake is considered unique in nature. As mentioned above, the water is surprisingly clear and clean, rich in oxygen. In the recent past, it was even considered healing. Baikal water was used to treat various diseases. In spring, its transparency is higher. In terms of performance, it approaches the standard - the Sargasso Sea. In it, the transparency of the water is estimated at 65 m. During the period of mass flowering of algae, the indicator of the lake decreases. Nevertheless, even at this time, in a lull from the boat, you can see the bottom at a fairly decent depth. High transparency is caused by the activity of living organisms. Thanks to them, the lake is poorly mineralized. Water is close in structure to distilled water. The importance of the lake Baikal is hard to overestimate. In this regard, the state provides special environmental protection to this area.

Origin of lake basins
Sedimentation in lakes

lakes – natural reservoirs with stagnant or low-flowing water, formed as a result of flooding of land depressions (hollows) with water masses. Lakes have no connection with the ocean and, unlike rivers, have a slow water exchange.

Each lake consists of three interconnected natural components:

1. hollows - landforms of the earth's surface,
2. water mass with substances dissolved in it,
3. plants and animals that inhabit the water.

Origin of lake basins

Lake basins arise as a result of various relief-forming processes and are divided into several groups according to their origin.

The manifestation of endogenous activity is associated with the formation of tectonic and volcanic basins.

Basins of tectonic origin formed as a result of the movement of parts of the earth's crust. Many lakes that have arisen in basins of tectonic origin occupy a vast area, are characterized by great depth and have ancient age. Characteristic examples of lakes belonging to this group are the Great African Lakes (including Tanganyika with a depth of -1470 m), confined to the East African rift system, where the processes of stretching and subsidence of the continental crust take place. Lake Baikal in Russia (which is the largest freshwater reservoir and has a maximum depth of -1620 m among lakes), Lake Biwa in Japan (famous for freshwater pearls mined in it) and others have a similar origin. Basins are often confined to isometric troughs (Chad, Eyre) or large tectonic faults. Formation is also associated with tectonic processes. residual lakes, which are the remains of ancient oceans and seas. So, Caspian lake separated from the Mediterranean and Black Seas as a result of tectonic movements of the earth's crust.

Hollows volcanic origin confined to the craters and calderas of extinct volcanoes or located among solidified lava fields. In the latter case, lake basins are formed when hot lava flows from under a colder surface lava horizon, which contributes to the subsidence of the latter (this is how Yellowstone Lake was formed), or when rivers and streams are dammed by lava or mud flow during volcanic eruptions. Basins of this origin are found in areas of modern or ancient volcanic activity (Kamchatka, Transcaucasia, Iceland, Italy, Japan, New Zealand and etc.).

The variety of exogenous processes leads to the formation of various groups of lake basins.

A large number of lake basins have glacial origin. Their formation may be associated with the activity of mountain and lowland glaciers. In the mountains, glacial lake basins are represented by moraine-dammed and cirque. Moraine-dammed ones are formed when river valleys are dammed up by glaciers. When the cirque basins are filled with water, small picturesque lakes with clear and cold water are formed.
On the plains, basins of glacial origin are common in the territory subjected to Quaternary glaciation. Among them, one can distinguish hollows of exaration, glacial-accumulative and moraine-dammed origin. Exaration basins are associated with mined-out moving ice by negative relief forms. A famous example of a lake that owes its origin to the destructive activity of glaciers is Loch Ness in Scotland, formed in a glaciated river valley. Thousands of lakes formed in the basins of glacial ploughing, are found in the territory Scandinavian Peninsula, in northern Canada. Glacial-accumulative basins are formed in the area of ​​development of moraine deposits. Lake basins in the area of ​​the moraine-plain relief are wide, have an oval shape and shallow depth (Chudskoye, Ilmen); in the conditions of a hilly-recessional and hilly-ridged relief, they have an irregular shape, islands, and a complex coastline, dissected by peninsulas and bays (Seliger). Moraine-dammed basins arise when a moraine pre-glacial river valley is dammed up (for example, Lake Saimaa in Finland).

In areas of permafrost, thermo basins karst origin , which owe their origin to the melting of fossil ice and frozen rocks and subsidence of the soil. Many basins of tundra lakes have this origin. All of them have a small depth and are small in area. Another area of ​​development of thermokarst basins is the area of ​​distribution of Quaternary fluvioglacial deposits. Here, during the melting of ice caps, huge blocks were buried under a layer of sediments carried out by melted glacial waters. dead ice. Many of them melted only after hundreds of years, and in their place there were basins filled with water.

Lake basins of karst origin are formed in areas composed of soluble (karst) rocks. The dissolution of rocks leads to the formation of deep, but usually insignificant basins. Here, failures often occur due to the collapse of the vaults of underground karst cavities. Examples of karst basins are the famous "Failure" in Pyatigorsk (known from the novel by Ilf and Petrov "The Twelve Chairs") and Lake. Zhirot in french alps, having a depth of -99 m with an area of ​​​​only 57 hectares.

Lake basins of suffusion origin are formed during subsidence of soils due to the removal of loose silt particles by groundwater. Basins of this genesis are found in the steppe and semi-desert zones. Central Asia, Kazakhstan and the West Siberian Plain.

Basins of fluvial origin associated with the geological activity of rivers. Most often these are oxbow and deltaic lakes. Sometimes the formation of lakes is due to the obstruction of the riverbed by alluvial sediments of another river. For example, the formation of Lake St. Croy (USA) is associated with the damming of the river. St. Croy alluvial deposits of the river. Mississippi. Due to the dynamism of erosive and accumulative fluvial processes and the small size of basins, the latter are relatively quickly filled with sediment and overgrown in some places and re-formed in others.

Some lake basins are formed as a result of springing by landslides, mountain landslides or mudflows of rivers. Usually such lakes do not exist for long - there is a breakthrough of sediments that form a "dam". So, in 1841. The Indus in present-day Pakistan was dammed by a landslide caused by an earthquake, and six months later the "dam" collapsed, and a lake 64 km long and 300 m deep was drained in 24 hours. Lakes in this group can remain stable provided that excess water is drained through erosion-resistant hard rock. For example, Lake Sarez, formed in 1911 in the valley of the river. Murghab in the Eastern Pamirs still exists and has a depth of -500 m (the tenth deepest lake in the world).
The process of damming the river with a powerful collapse also contributed to the formation of one of the "pearls" of the Caucasus - Lake Ritsa in Abkhazia. A giant landslide on the slope of Mount Pshegish dammed the Lashipse River. The waters of the river flooded the gorge (tracing a large tectonic fault in the strata of rocks) for more than 2 km, the water rose by 130 m. A river with a different name, Yupshara (in Abkhazian “split”), is knocked out from under a natural stone dam.

lakes artificial origin associated with the filling of artificial basins (quarries, etc.) with water, or with the damming of river flows. During the construction of dams, reservoirs of various sizes are formed - from small ponds to huge reservoirs(located in Africa are the Victoria reservoirs on the Victoria Nile, Volta on the Volta and Kariba on the Zambezi; the largest in Russia is Bratsk reservoir on the Angara River). Some dams were built to generate electricity for aluminum smelting from large deposits of bauxite. It should be added that dams are created not only by man. Dams built by beavers can reach lengths of more than 500 m, but they exist only for a short time.

Basins of coastal marine origin formed mainly as a result of the separation sea ​​bays bars from the sea area during the movement of the alongshore sediment flow. On initial stage the basin is filled with salty sea waters, which later formed salt Lake gradually softens.

Hollows of organogenic origin occur in the sphagnum swamps of the taiga, forest-tundra and tundra, as well as on coral islands. In the first case, they owe their origin to the uneven growth of mosses, in the second - to coral polyps.

Lakes on the scale of geological time exist for a relatively short time. The only exceptions are some lakes with basins of tectonic origin, confined to active zones of the earth's crust, and large residual lakes. Over time, the basins are filled with sediments or become swampy.

Sedimentation in lakes

Lake deposits are represented by terrigenous, chemogenic and organogenic sediments. The composition of sediments accumulating in lakes is primarily determined by climatic zoning.

In the lakes of humid regions, predominantly silty-argillaceous deposits accumulate, often with a large amount of organic matter. Dead organisms, as well as material carried into the lake, are deposited at the bottom and form gyttia(from Swedish gyttja - silt, mud) - lake deposits, consisting of organic residues. The organic matter of gyttium is formed mainly due to the decay products of plant and animal organisms living in water, to a lesser extent due to the remains of terrestrial plants brought from the surrounding land. The mineral part consists of sandy-clay material and oxides of calcium, iron and magnesium precipitated from water. Gyttia is also called sapropel(from the Greek sapros - rotten and pelos - silt, mud - "putrefactive silt"). In Lake Nero, located near the city of Rostov-Yaroslavsky (Rostov Veliky), the layer of sapropel reaches 20 m. Sapropels are used as fertilizer or as a mineral feed for livestock; sometimes for balneological purposes (mud therapy).

In semi-desert and desert arid zones, lakes are endorheic with intense evaporation. Since rivers and underground waters always bring salts, and only pure water evaporates, there is a gradual increase in the salinity of lake waters. The concentration of salts can increase so significantly that from the water (brine) supersaturated with salts, salt is deposited on the bottom of the lake (self-settling lakes). Salinization of continental lakes accumulates carbonate, soda, sulfate, salt and other chemogenic deposits. In Russia, modern soda lakes known in Transbaikalia and in Western Siberia; abroad, Lake Natron in Tanzania and Lake Searls in California are very famous. Natural soda deposits are associated with fossil deposits of such lakes.
In general, arid regions are characterized by halogen-carbonate deposits, poor in organic matter.

In a number of cases, the origin of lake basins plays a decisive role in the nature of sedimentation. Glacial lakes are characterized by banded clays formed by a combination of lacustrine and glacial deposits. In karst lakes, carbonates accumulate, sometimes heaps of blocks of landslide origin.

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Significant water reserves are concentrated in lakes. There are more than 2.5 million lakes in Russia. The largest lakes are the Caspian, Ladoga, Onega and Baikal.

Caspian lake is the most big lake in the world, the deepest is Lake Baikal. The lakes are very unevenly distributed.

In particular, in the Vilenovsky basins, the West Siberian Plain and the northwestern layer of Europe - in Karelia. All these areas are in too much humidity. In the south, in the zone of the steppe and semi-sedimentary zone with a weak climate, the number of lakes decreases sharply, and many lakes have salt or salt. Salt is such huge large lakes as the Caspian, as well as lakes Elton and Baskunchak, where salt is eliminated.

Hydrographic characteristics of large lakes in Russia

There are different lakes and sources of pools.

Lakes of tectonic origin are located in trenches and cracks in the earth's crust. The largest tectonic lake Baikal is located in the Graben, reaching a depth of 1637 m.

Ice-tectonic lake basins were created as a result of processing liquid depressions of the glacial crust of the glacier: Imandra, Ladoga, Onega.

In Kamchatka and the Kuril Islands, the lake is mainly of volcanic origin. In the northwest of the European Plain, the sources of lake basins are associated with continental ice. Many caves are located between the hills of the sea: Seliger, Valdai.

Due to landslides in mountain valleys there was a lake of a lake: Sarez in the Pamirs, Ritsa in the Caucasus. Small lakes are formed by karst nests.

In the south of Western Siberia, there are many lakes in the form of plates, which were created as a result of stoning stones. When ice melts on the surface of the permafrost, shallow slab-like waters also form. Lake people are located on the flood plains of low-lying rivers. On the Black and Sea of ​​Azov there are estuary lakes.

All the largest and largest lakes in Russia are often used in the national economy. Catch and catch in them. Especially a lot of fish, including the most valuable sturgeon, end up in the Caspian.

In Baikal, the harvest is omul. Lakes are also used for navigation - geoglobus.ru. Numerous minerals were acquired in the lakes of lakes: oil and mirbilite in the Caspian lake, salt in Elton and Baskunchak. Water for freshwater lakes is used for drinking. There are many sanatoriums and rest houses on the shores of many lakes.

There are nine lake districts on the territory of Russia:

1) northwest lake, iceberg icebergs;
2a) Azov-Black Sea estuaries associated with marine activities;
2b) North Caucasian-glacial and karst lake;
3) salt formation of the Caspian Lake;
4) West Siberian-Tuscan and bitter-salty lakes;
5) Altai - sea ​​view lakes (Teletskoye, Markakol);
6) Zabaikalsky - the remaining lakes;
7) Lower Amur lakes, which have a hydrological connection with the Amur River;
8) Yakuti - lakes of thermocouples;
9) Lake Kamchatka - lakes of volcanic origin (Kronotsky, Kurilsky).

A lake is a closed depression of land filled with water. It has a slow water exchange, unlike rivers, and does not flow into the waters of the oceans, unlike the seas. These reservoirs on our planet are distributed unevenly. The total area of ​​the Earth's lakes is about 2.7 million km 2, or about 1.8% of the land surface.

The lakes have a number of differences among themselves both in external parameters and in the composition of the water structure, origin, etc.

Classification of lakes by origin

Glacial reservoirs were formed due to the melting of glaciers. This happened during periods of severe cooling, which fettered the continents repeatedly over the past 2 million years. result ice ages become modern lakes located in North America and Europe, namely in Canada, Baffin Island, Scandinavia, Karelia, the Baltic States, the Urals and in other areas.

Huge blocks of ice, under the weight of their weight, and also because of their movements, formed considerable pits in the thickness of the earth's surface, sometimes even pushing apart tectonic plates. In these pits and faults, after the melting of ice, reservoirs were formed. One of the representatives glacial lakes can be called a lake. Arbersee.

The cause of the occurrence was the movement of lithospheric plates, as a result of which faults were formed in the earth's crust. They began to fill with water from melting glaciers, which led to the emergence of this type of reservoir. The brightest example is Lake Baikal.

River lakes appear when some sections of flowing rivers dry up. In this case, the formation of chain reservoirs arising from one river takes place. The second variant of river formations are floodplain lakes, which appear due to water barriers that interrupt the water channel.

Seaside lakes are called estuaries. They appear when lowland rivers are flooded by the waters of the seas or as a result of the lowering of sea coasts. In the latter case, a strip of land or shallow water appears between the newly formed bay and the sea. In estuaries, which appeared from the confluence of the river and the sea, the water has a slightly salty taste.

Karst lakes are earthen pits that are filled with water. underground rivers. Pit pits are failures of the lithosphere, consisting of limestone rocks. Due to the failure, limestone rocks line the bottom of the reservoir, which affects the transparency of its filled waters: they are crystal clear.

Karst lakes have one distinctive feature - they are periodic in their appearance. That is, they can disappear and form again. This phenomenon depends on the level of underground rivers.

They are located in mountain valleys. They are formed in several ways. Due to mountain landslides that block the river flow and thereby form lakes. The second way of formation is the slow descent of huge blocks of ice, which leave behind deep land failures - basins that are filled with water from melted ice.

lakes volcanic type appear in the craters of dormant volcanoes. Such craters are of significant depth and high edges, which prevents runoff and inflows of river waters. This makes the volcanic lake practically isolated. Craters fill with rainwater. The specific location of such objects is often reflected in the composition of their waters. The increased content of carbon dioxide makes them dead, unsuitable for life.

These are reservoirs and ponds. They are created intentionally for industrial purposes. settlements. Also, artificial lakes can be the result of earthworks, when the remaining earthen pits are filled with rainwater.

Above was a classification of lakes depending on the origin.

Types of lakes by position

It is possible to make a classification of lakes depending on their position in relation to the earth as follows:

1. Terrestrial lakes are located directly on the surface of the land. These are involved in the constant water cycle.
2. Underground lakes are located in underground mountain caves.

Mineralization classification

You can classify lakes by the amount of salts as follows:

1. Fresh lakes are formed from rainwater, melting glaciers, groundwater. The waters of such natural objects do not contain salts. In addition, fresh lakes are a consequence of the overlapping of river beds. The largest fresh lake is Baikal.
2. Salt water bodies are subdivided into brackish and saline.

Brackish lakes are common in arid areas: steppes and deserts.

Salt lakes in terms of the content of salts in the thickness of their waters resemble oceans. Sometimes the salt concentration of lakes is somewhat higher than in the seas and oceans.

Classification by chemical composition

The chemical composition of the lakes of the Earth is different, it depends on the amount of impurities in the water. Lakes are named based on this:

1. In carbonate lakes, there is an increased concentration of Na and Ca. Soda is mined from the depths of such reservoirs.
2. Sulfate lakes are considered curative due to the content of Na and Mg in them. In addition, sulfate lakes are a place for the extraction of Glauber's salt.
3. Chloride lakes are salt lakes, which are the place where common table salt is mined.

Water balance classification

1. Waste lakes are endowed with the help of which a certain amount of water is discharged. As a rule, such reservoirs have several rivers flowing into their basin, but there is always one flowing one. An excellent example is the large lakes - Baikal and Teletskoye. The water of sewage lakes is fresh.
2. Endorheic lakes are saline lakes, since the flow of water in them is more active than its inflow. They are located in the desert and steppe zones. Sometimes they produce salt and soda on an industrial scale.

Classification according to the amount of nutrients

1. Oligotrophic lakes contain a relatively small amount of nutrients. The peculiarities are the transparency and purity of the waters, the color from blue to green, the depth of the lakes is significant - from medium to deep, the decrease in oxygen concentration closer to the bottom of the lake.
2. Eutrophic plants are saturated with a high concentration of nutrients. The peculiarities of such lakes are the following phenomena: the amount of oxygen sharply decreases towards the bottom, there is an excess of mineral salts, the color of the water is from dark green to brown, which is why the transparency of the water is low.
3. Dystrophic lakes are extremely poor in minerals. There is little oxygen, the transparency is low, the color of the waters can be yellow or dark red.

Conclusion

The water basin of the Earth is made up of: rivers, seas, oceans, glaciers of the oceans, lakes. There are several types of lake classifications. They have been reviewed in this article.

Lakes, like other bodies of water, are the most important Natural resources which are actively used by man in various fields.

Topic 7. Hydrology of lakes

Origin, types and morphology of lake basins

lakes called hollows or hollows the earth's surface, filled with water and not having a direct connection to the sea.

The sizes of lakes fluctuate in a very wide range. According to the above definition, lakes can also include such large bodies of water as the Caspian and Aral Seas, as well as relatively small temporary accumulations of water in depressions of the terrain, which are formed, for example, during the spring snowmelt.

Sometimes, unlike flowing waters (rivers), lakes are defined as bodies of water with slow flow or slow water exchange.

In the presence of a basin, the formation of a lake will occur when the inflow of water into this depression exceeds the losses due to filtration and evaporation.

Reservoir -And man-made lake .

Pond -small reservoir .

Pond - natural lakes, on the area of ​​​​which aquatic vegetation is common.

Types of lakes according to the nature of the basins. Despite the wide variety of lakes found in nature, certain types can be distinguished among them, which have similarities in a number of ways.

First of all, certain types of lakes can be distinguished depending on the conditions for the formation of the lake bed.

According to the nature of the basins, which served as the basis for the formation of the lake, can be distinguished:

1. P lotin lakes - are formed when the valley is blocked in some place by a collapse, glacier, sediment, etc.; This group also includes artificial lakes - reservoirs.

Among the dam lakes, one can distinguish

- river - may appear as temporary formations as a result of a sharp decrease in the flow of individual rivers during the dry season; in this case, the rivers often turn into a chain of lakes lying in the valley and separated from each other by dry sections of the channel.

- floodplain - are directly related to the process of formation of oxbow lakes, which arise as a result of the blocking of individual branches of the river by a ridge of sediments and the formation of a new channel by the river.

- valley - arise in the mountains from rubble. Lakes of landslide origin are formed as a result of blockage of a narrow valley by the products of destruction of their slopes.

- coastal lakes There are two types: lagoons and estuaries.

lagoons arise in the case when shallow bays, or bays, are separated from the sea by alluvial sandy-argillaceous shafts, or spits.

Estuaries represent the mouth part of the valley flooded by the sea.

2. Moraine lakes owe their origin to the activity of glaciers, especially the powerful ice sheets of the Quaternary period, which buried vast expanses under them. After the retreat (melting) and disappearance of such an ice sheet, detrital material remained in its place, which carried the glacier with it: clay, sand, crushed stone, large blocks of rocks, etc.

A large accumulation of this material (moraines) in some places and insignificant in others creates a relief characterized by hilly, continuous and frequent alternation of elevations and depressions, and the depressions are usually closed. Filled with water, they form moraine lakes of round or irregular shape, with many branches and bays. In the conditions of a moraine landscape, there are many lakes that also belong to the dam type.

3. Karovye lakes occupy depressions worked out during the ice age by the joint work of ice, firn and frosty weathering.

4. Karst lakes are the result of the chemical (dissolving) activity of ground and surface waters. The removal of dissolved substances, as well as fine clay particles (suffusion) can lead to the formation of underground voids and subsidence of the roof over these voids, which will cause the appearance of funnels on the surface of the earth; if these funnels are filled with water, karst lakes will appear in their place.

A peculiar kind of karst type of lakes are thermokarst lakes , resulting from the filling of depressions on the surface of the earth with water, formed in areas of permafrost development due to the melting of underground layers or ice lenses. The melting of this ice not only contributes to the formation of a lake basin, but also supplies water to a large extent to fill the basin.

5. Deflationary lakes are located in hollows created as a result of the blowing process, and in depressions between dunes and dunes.

Many basin lakes arise as a result of volcanic and tectonic processes.

6. Tectonic lakes . Tectonic processes cause the appearance of huge basins. Therefore, tectonic lakes usually deep. Lakes Issyk-Kul, Baikal, Sevan and others can serve as examples.

7. Volcanic lakes arise either in the crater of an extinct volcano, or in depressions on the surface of a lava flow formed during its solidification, or in a river valley due to its blocking by a lava flow.

According to water balance lakes are divided into:

- sewage- have a drain, mainly in the form of a river);

- drainless- do not have surface runoff or underground water drainage to neighboring watersheds. Water consumption occurs due to evaporation.

By chemical composition The waters of the lake are divided into:

Fresh

Mineral (salty)

Elements of the lake bed and coastal area. A depression located on the ground and filled with water has a regularly constructed relief that distinguishes it from depressions not occupied by water.

The initial shape of the basins changes under the action of erosion both by surface runoff into the lake and by waves: the slopes of the basin flatten out, the irregularities of the bottom topography are smoothed out, filled with sediments, and the slopes of the coast acquire a stable profile.

The section of lake science, which deals with the patterns that are manifested in the formation of the relief of lake basins, is called lake morphology .

lake basin separated from the surrounding area native coast, forming coastal slope, or yar; the base of this shore is located at the upper boundary of the influence of the lake wave.

The root bank ends edge, or line of conjugation of slopes with the surface of the adjacent terrain.

The part of the basin filled with water up to the height of the maximum level rise is called lake bed, or lake bowl.

In the lake basin, first of all, one can distinguish coastal And deep areas.

In the coastal area three zones are distinguished:

1) coastal slopes (yar)- a part of the lake slope that surrounds the lake from all sides and is not affected by the wave surf;

2) coast - includes dry part , which is exposed to water only during strong waves and especially when the water is high, flooded , which is covered with water periodically - during the rise in the water level of the lake, and underwater , which usually lies below the surface of the water and, in contrast to the deeper parts of the coastal area, is exposed to waves during waves;

3) coastal shoal - ends with an underwater slope, which is the boundary between the slope and the bottom of the lake bed; the upper part of the coastal shoal corresponds to the lower boundary of the impact on the coastal area of ​​the wave surf.

These zones of the coastal region of the lake basin are shown schematically in Fig. 1.

Rice. 1. Scheme of the division of the coastal area of ​​the lake basin

The coast and coastal shallows are combined into one zone - coastal or littoral. Its lower limit is determined by the depth of the wave, sometimes by the depth of penetration of the sun's rays. Deep part of the lake profundal. Between the littoral and the profundal sublittoral.

Formation of the lake bed under the influence of waves and sedimentation. Excitement, depending on the strength of the wind, the depth and size of the lake, affects the coastal area of ​​the lake basin for a long period, destroys its components rocks and carries the eroded material down the slopes and to the bottom of the lake. As a result of this, the sizes of the coast and erosion shoals increase, at the same time, the area of ​​alluvium increases and decreases due to the deep region of the lake.

Thus, the lake is gradually filled in due to the action of the waves. The degree of intensity of this process, of course, largely depends on the geological composition of the rocks that make up the shore of the lake.

However, whatever the coastal material, it eventually turns into fine stone, gravel and sand under the influence of waves and weathering.

In addition to roughness, the shape of the lake bed is significantly affected by the process of alluvial sediment inflow brought by the rivers flowing into the lake. The surface streams flowing into the lake erode the soil along the way and carry the erosion products into the lake.

In addition to mineral sediments falling into the lake bed as a result of waves or carried by rivers, the lake basin is also filled with silt deposits of organic origin. This silt is a product of processes occurring in the lake itself, and is formed as a result of the death and subsequent sedimentation of microscopic animal and plant organisms suspended in the water (the so-called plankton), as well as the death of coastal vegetation, which decays after decay into the smallest particles, easily carried by currents to the middle of the lake. The intensive development of these organisms during the warm period of the year, and the death during the cold period, determines the layer-by-layer deposition of these silts on the bottom of the lake, which makes it possible to determine the age of the lake by layers.

Overgrowth of lakes. The amount of mineral precipitation and organic silt at the bottom of the lake increases every year, as a result of which the bottom gradually rises.

In lakes with gently sloping shores, wetland plants approach the lake from the shores, edging the water surface with a wide green ring.

For shallow lakes with gently sloping shores, a number of belts can be distinguished, regularly changing from the shores to the center of the lake (Fig. 2).

Rice. 2. Scheme of overgrowing of shallow lakes.

1 - sedge peat, 2 - reed and reed peat, 3 - sapropel peat, 4 - sapropelite.

Sometimes on shallow lakes one can observe alloys - islands of vegetation detached from the coast or directly adjacent to the mineral coast (Fig. 3). At first, these quays form small areas, then, as the lake becomes shallower, they grow, join with others, and cover the lake with a continuous cover of bog vegetation from grass and moss layers. These formations are known as quicksand.

Rice. 3. Scheme of overgrowing deep lake by the formation of alloys.

1 - alloy peat; 2 - mutta, or pelogen; 3 - sapropel peat; 4 - sapropelite.

Geographical position of the lake. Morphometric characteristics. An important characteristic of the lake is its geographical position (latitude, longitude) and height above sea level.

These data already make it possible to form a general idea of ​​the main features of the lake regime. The geographical position of the lake to a certain extent reflects the general climatic features of the area, and the altitude also determines the local influence of climatic and other factors on the processes occurring in the lake.

When studying lakes and lake basins, it is important to establish not only the conditions for their formation, but also to determine a number of numerical characteristics that give quantitative ideas about the main elements of the lake and lake basin. These characteristics are called morphometric.

lake area ω, m2, calculated in two ways: either together with the area of ​​the islands, or separately the area of ​​the water surface. Since the shores of the lakes are not sheer, the area of ​​the water surface (mirror of the lake) changes when the level of the lake changes.

The length of the lakeL, m - the shortest distance between the two most distant points located on the shores of a lake, measured along the surface of the lake.

Thus, this line will be straight only in the case of relatively simple outlines of the lake; for a meandering lake, this line, obviously, may not be straight, but may consist of separate segments of straight and curved lines.

Lake width– distinguish:

Greatest Width - V, m , defined as the largest diameter (perpendicular) to the length line of the lake,

Average width - On Wednesday , m representing the area ratio ω lakes to its length L

Tortuosity coefficientT - the degree of development of the coastline - the ratio of the length of the coastline s to the circumference of a circle having an area equal to the area of ​​the lake,

The tortuosity coefficient of a shoreline can also be expressed as the ratio of the length of a shoreline S to the perimeter of the broken line S" , circling the contour of the lake:

m = S/ S"

In this case, a more correct idea of ​​the indentation of the coastline is obtained.

Wide application in assessing the water reserves of the lake has curve of change in lake area with depth , which is a graph of the relationship between the areas of the horizontal sections of the lake and the corresponding depths, and lake volume curve depending on its depth.

Rice. 4. Curves of areas and volumes of Lake Onega

On Fig. Figure 4 shows the curves of changes in the area and volume of Lake Onega with depth. Such curves make it possible to determine the area of ​​the lake surface and the volume of water for any level. These values ​​must be known in all calculations.

The volume of water in the lake W , m 3 can be determined from the isobath map using the "prism method". Isobath surfaces divide the volume of the lake into a number of layers, each of which can be considered approximately as a prism, the bases of which will be the areas bounded by adjacent isobaths, and the height is equal to the cross section between them. Denoting the areas bounded by individual isobaths, through ω 0 , ω 1 , ω 2 , ω 3 … ω n , and cutting them through h , the volume of water in the lake is determined by the formula

W =
+
+
+…+
+∆ W =

=
∆ W,

Where ∆ W - the volume enclosed between the area of ​​the last deepest isobath and the point of the lake bottom with the maximum depth, determined by the formula:

∆W=
,

Where h poppy c is the maximum depth of the lake in meters; h n is the depth corresponding to the largest isobath, ω n – the area of ​​the last (deepest) isobath.

The maximum depth of the lake ish Max , m.

WITH
average lake depth - h Wed , m - the ratio of the volume of water in a lake to the area of ​​its surface.

Average bottom slope between isobaths is determined by the formula:

Where l 1 , l 2 are the lengths of the isobaths between which the slope is determined; h isobath section, ω is the area of ​​the ring between the isobaths.

Average slope of the lake I is determined by the formula:

Where n is the number of isobaths.

Knowledge of the elements that characterize the shape of the lake basin is necessary not only to understand the basic laws of the lake regime, but also to solve a number of economic problems directly related to the exploitation of the lake. For example, when using a lake for transport purposes, it is necessary to know the distribution of depths within the entire water area and, in particular, in the coastal shallow zone. When regulating the flow of rivers flowing from the lake, it is necessary to have curves of the dependence of the volume of water and the areas of the lake on the height of the level. To calculate wave elements, it is important to know the distribution of depths and widths of the lake in different directions, etc.

Level regime of lakes.

The level regime of lakes is determined by a complex of the following natural conditions:

a) the ratio between the incoming (precipitation on the lake surface, surface inflow, underground inflow) and the outgoing part of the lake's water balance (evaporation, surface and underground runoff from the lake);

b) morphometric characteristics of the lake bowl and the lake basin (the ratio between the height of the water in the lake and the area of ​​its water surface);

c) the size of the lake, its shape, the nature of the shores, the nature of wind activity, which determines the size of waves, surges and surges.

Lake level fluctuations can be reduced to the following three main types: seasonal , annual And short-term .

Sometimes fluctuations in the level in the annual (seasonal) and long-term period, reflecting the regime of inflow and loss of water in the lake, are called absolute fluctuations , and short-term, which occur simultaneously with absolute changes in the level, are called relative fluctuations . Due to the fact that relative fluctuations occur simultaneously with absolute fluctuations, they additionally increase or decrease the amplitude of the absolute fluctuation of the lake level at its individual points.

Seasonal fluctuations that occur during the year are due to different in different months, but more or less correctly, annually recurring ratios between the incoming and outgoing parts of the water balance.

Amplitude of annual level fluctuations water in different lakes is different and depends on a number of factors: climatic conditions, the nature of nutrition, the size of the catchment area, the size of the lake, the geological conditions of the lake bed, etc.

The absolute values ​​of the amplitude of fluctuations in the levels of natural lakes vary over a fairly wide range - from tens of centimeters to 2-4 m and more, depending on the combination of the above conditions.

After a number of high-water years, when the inflow exceeds the water discharge from the lake, there is a higher level standing than after low-water periods. Due to the fact that on large (especially drainless) lakes the level of each given year is a consequence of the nature of the water content of a number of previous years, a low level can also occur in a high-water year if this year is included in the cycle of years of a low-water period, and a high level can occur in a low-water period if this a dry year is observed within a high-water period.

In addition to the mentioned cause, which takes place on each lake, sometimes there are so-called secular fluctuations , caused by geological factors (uplift, lowering of the lake basin and its individual parts).

Short-term, or relative, fluctuations in water levels in the lake are the result of waves, wind surges, and seiches.

Dynamic phenomena in lakes

Permanent and temporary movements of water masses. The movements of the water mass that occur in lakes can be divided into permanent and temporary.

Constant movements The waters in the lake in the form of currents are caused by a river flowing into or out of the lake (sewage streams). The intensity of such currents is determined by the ratio of the volume of the lake and the flow rate of the inflowing or outflowing river. If the volume of water in a flowing lake is small compared to the volume of water flowing into the lake, then a current is established in the lake similar to that in a river, only with correspondingly lower velocities. Such a flowing lake can, in a sense, be regarded as an extreme case of a significant expansion of the riverbed.

If, on the contrary, the volume of the lake is very large in comparison with the volume of water flowing in and out of it, then, although in this case it is also called flowing, in many respects, in terms of the nature of the processes occurring in it, it is closer to a drainless lake. A current of this type is observed in the lake. Baikal, the volume of which is extremely large compared to the volume of the flow of the rivers Selenga, Upper Angara, etc. flowing into it, and the river flowing from it. Hangars.

Temporary movements The water mass of the lake can manifest itself in the form of currents and waves.

Among the temporary currents, first of all, one should single out those that arise under the influence of the wind and as a result of uneven heating and cooling of the lake water.

Wind (drift) currents have a particularly significant effect on the nature of physical processes in lakes with large area, flat shape of the lake bed and shallow depths.

The uneven cooling and heating of the water masses of the lake primarily causes vertical, so-called convection currents , to some extent affecting the horizontal movement of water masses.

Among the temporary movements of the water masses of the lake, the most important are wind waves Andseiches.

Wind waves. Research has shown; that if two media of different density are located one above the other, but only in a state of rest of one medium relative to the other, the surface separating them will be a plane. If one of them moves relative to the other, then the surface separating them takes on a wave-like character, and the size of the waves depends on the speed of movement, the difference in densities and depths of both media.

When air moves over the water surface, as a result of friction, an unstable equilibrium is created on the surface of their separation, which, inevitably, being disturbed, naturally passes into a wave form that is stable under these conditions with an increase in the separation plane against the initial level line in some places and with a decrease in others.

Waves are characterized by the following elements (Fig. 5):

- vertex , or crest , waves - the highest point of a wave A;

- sole , or hollow - the lowest point of the wave IN;- height waves - the difference between the marks of the ridge and sole;

- length - distance between two peaks or two soles;

- steepness waves ( A ) at a given point - the tangent of the angle that is tangent to the wave profile with a horizontal line. Often in the calculated dependences, the steepness of a wave is understood not as the steepness at a given point, but as the ratio of the wavelength to the wave height;

- period waves - the period of time during which the wave runs a distance equal to its length;

- speed wave propagation - the distance traveled by any point of the wave (for example, a crest) per unit time.

According to the external form, they distinguish:

a) correct - two-dimensional - excitement, when one system of waves propagating in one direction and having the same shape and size is observed;

b) irregular - three-dimensional - excitement, consisting of randomly moving waves, the crests and hollows of which are divided into separate hillocks and depressions.

Rice. 5. Scheme of the wind wave

As applied to the case of regular two-dimensional waves, there is a theory of waves, known as the theory trochoidal waves . This theory establishes the external form of the wave and the laws of motion of water particles.

The waveform, according to the theory under consideration, is trochoid, i.e., a curve described by some point inside a circle rolling (without slipping) along a straight line, while a point on the circle of such a circle describes a curve called cycloid (Fig. 6).

Rice. 6. Trochoid (1) and cycloid (2).

seiches. Sometimes in the lake there is an oscillation of the entire mass of water, and no wave propagates over its surface. This oscillatory movement is called seiches . During seiches, the surface of the lake acquires a slope to one side or the other. The fixed axis around which the mirror of the lake oscillates is called node . Studies show that seiches are more stable in deep waters than in shallow waters.

Characteristics of the process of heating and cooling water in lakes.

Heating and cooling changes non-simultaneously throughout the water column. The most dramatic changes in temperature are observed on the surface of the reservoir, from where, under the influence of dynamic and convective mixing, currents and waves, they propagate throughout the entire water column.

They are formed in places of faults and shifts of the earth's crust. As a rule, these are deep narrow reservoirs with straight sheer banks, located in deep through gorges. Kurile Lake is located in the south of Kamchatka in a deep picturesque basin surrounded by mountains. The greatest depth of the lake is 306 m. Its banks are steep. Numerous mountain streams flow from them. The lake is sewage, the Ozernaya River originates from it. Hot springs come to the surface along the shores of the lake, and in its middle there is an island called the Heart-stone. Not far from the lake there is a unique outcrop of pumice stones, which are called Kutkhin Baty. Currently, the lake has been declared a nature reserve and a zoological monument of nature.

bottom profile tectonic lakes sharply defined, has the form of a broken curve. Glacial deposits and processes of sediment accumulation have little changed the clarity of the tectonic lines of the lake basin. The influence of the glacier on the formation of the basin can be noticeable, it leaves traces of its presence in the form of scars, sheep's foreheads, which are clearly visible on the rocky shores and islands. The shores of the lakes are composed mainly of hard stone rocks that are weakly susceptible to erosion, which is one of the reasons for the weak process of sedimentation. These lakes belong to the group of lakes of normal depth (a=2-4) and deep (a=4-10). The deep-water zone (more than 10 m) of the total volume of the lake is 60-70%, shallow water (0-5m) 15-20%. The waters of the lakes are thermally heterogeneous: during the period of the greatest warming surface water low bottom temperatures are maintained, which is facilitated by stable thermal stratification. Aquatic vegetation is rare, only in a narrow strip along the shores of closed bays. Typical lakes in the river basin. The suns are large and medium-sized: Palye, Sundozero, Sandal, as well as very small lakes Salvilambi and Randozero, located on private watersheds of lakes Palye and Sandal.

As a result of the movement of the earth's crust, depressions form in some places over time. It is in these depressions that tectonic lakes arise. The three largest lakes in Kyrgyzstan: Issyk-Kul, Son-Kul and Chatyr-Kul were formed tectonically.

There are many lakes in the forest-steppe Trans-Urals. Here are such large reservoirs as Uelgi, Shablish, Argayash, B. Kuyash, Kaldy, Sugoyak, Tishki, etc. The depths of the lakes on the Trans-Ural Plain noticeably decrease and do not exceed 8-10 m. By origin, these lakes belong to the erosion-tectonic type. Tectonic depressions have been modified as a result of the impact of erosion processes. Many lakes of the Trans-Urals are confined to ancient hollows of river flow (Etkul, Peschanoe, Alakul, Kamyshnoe, etc.).

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