Lakes of glacial and tectonic origin. Lake types. Types of lakes by origin

- a reservoir formed on the surface of the land in a natural depression. Since the lake has no direct connection with the ocean, it is a reservoir of slow water exchange.

The total area of ​​lakes on the globe is about 2.7 million km 3, which is 1.8% of the land surface.

The main characteristics of the lake:

• lake area - water surface area;
• coastline length - water edge length;
• lake length - the shortest distance between the two most distant points on a coastline, average width - ratio of area to length;
• lake volume - the volume of the basin filled with water;
• average depth - ratio of water mass volume to area;
• maximum depth - found by direct measurements.

The largest lake in terms of water surface area on Earth is the Caspian (376 thousand km 2 at a water level of 28 m), and the deepest is Baikal (1620 m).

The characteristics of the largest lakes in the world are given in Table. 1.

In each lake, three interconnected components are distinguished: a basin, a water mass, vegetation and animal world reservoir.

Lakes of the world

By position lake basin lakes are divided into ground and underground. The latter are sometimes filled with juvenile water. The subglacial lake in Antarctica can also be classified as an underground lake.

Lake basins can be like endogenous, and exogenous origin, which most significantly affects their size, shape, water regime.

The largest lake basins. They can be located in tectonic depressions (Ilmen), in foothill and intermountain troughs, in grabens (Baikal, Nyasa, Tanganyika). Most of the large lake basins have a complex tectonic origin, both discontinuous and folded movements are involved in their formation (Issyk-Kul, Balkhash, Victoria, etc.). All tectonic lakes are different large sizes, and most - and significant depths, steep rocky slopes. The bottoms of many deep lakes lie below the level of the World Ocean, and the mirror of the oxen is above the level. In disposition tectonic lakes certain regularities are observed: they are concentrated along the faults of the earth's crust either in rift zones (Syrian-African, Baikal), or they frame shields: along the Canadian shield there are Great Bear Lake, the Great Slave, the Great North American Lakes, along the Baltic Shield - Onega, Ladoga, etc.

Volcanic lakes occupy craters and calderas extinct volcanoes(Kronopkoye lake in Kamchatka, lakes of Java, New Zealand).

Along with lake basins created by the internal processes of the Earth, there are very numerous lake baths formed due to exogenous processes.

Among them, the most common glacial lakes on the plains and in the mountains, located both in hollows plowed by the glacier, and in depressions between hills with uneven deposition of moraine. The destructive activity of ancient glaciers owes its origin to the lakes of Karelia and Finland, which are elongated in the direction of glacier movement from northwest to southeast along tectonic cracks. In fact, Ladoga, Onega and other lakes have a mixed glacial-tectonic origin. The glacial basins in the mountains include numerous, but small car lakes located in bowl-shaped depressions on the slopes of mountains below the snow line (in the Alps, in the Caucasus, Altai), and trough lakes - in trough-shaped glacial valleys in the mountains.

Lakes among hilly and moraine relief are associated with uneven accumulation of glacial deposits on the plains: in the northwest of the East European Plain, especially on the Valdai Upland, in the Baltic States, Poland, Germany, Canada and in the north of the USA. These lakes are usually shallow, wide, with lobed shores, with islands (Seliger, Valdai, etc.). In the mountains, such lakes arose on the site of former tongues of glaciers (Como, Garda, Würm in the Alps). In areas of ancient glaciation, there are numerous lakes in the hollows of the flow of melted glacial waters, they are elongated, trough-shaped, usually small and shallow (for example, Dolgoye, Krugloye - near Moscow).

Karst lakes are formed in places where rocks are leached by underground and partly surface waters. They are deep, but small, often rounded in shape (in the Crimea, the Caucasus, in the Dinaric and other mountainous regions).

Suffusion lakes are formed in basins of subsiding origin at the site of intensive removal of fine earth and mineral particles by groundwater (south of Western Siberia).

Thermokarst Lakes are created when permafrost is burned or ice melts. Thanks to them, the Kolyma Lowland is one of the most lake regions in Russia. Many relict thermokarst lake basins are located in the northwest of the East European Plain in the former periglacial zone.

eolian lakes arise in blowout basins (Lake Teke in Kazakhstan).

Zaprudnye lakes are formed in the mountains, often after earthquakes, as a result of landslides and landslides blocking river valleys (Lake Sarez in the Murgab valley in the Pamirs).

In the valleys of lowland rivers, the most numerous are floodplain oxbow lakes of a characteristic horseshoe shape, formed as a result of meandering of rivers and subsequent straightening of channels; when rivers dry up in bochagas - reaches, river lakes are formed; in river deltas there are small ilmen lakes, in place of channels, often overgrown with reeds and reeds (ilmens of the Volga delta, lakes of the Kuban floodplains).

On the low coasts of the seas, coastal lakes are characteristic in place of estuaries and lagoons, if the latter are separated from the sea by sandy alluvial barriers: spits, bars.

TO special type relate organogenic lakes among swamps and coral buildings.

These are the main genetic types of lake basins, determined by natural processes. Their location on the continents is presented in Table. 2. But in Lately there are more and more "man-made" lakes created by man - the so-called anthropogenic lakes: lakes - reservoirs on rivers, lakes - ponds in quarries, in salt mines, on the site of peat mining.

By genesis of water masses There are two types of lakes. Some have water of atmospheric origin: precipitation, river and The groundwater. Such lakes insipid, although in dry climates they can eventually become salty.

Other lakes were part of the World Ocean - these are relic salty lakes (Caspian, Aral). But even in such lakes, the primary sea water can be greatly transformed and even completely displaced and replaced by atmospheric water (Ladoga and others).

Table 2. Distribution of the main genetic groups of lakes by continents and parts of the world

depending from water balance, t.s. According to the conditions of inflow and runoff, lakes are divided into waste and non-drainage. Lakes that discharge part of their waters in the form of river runoff - sewage; a special case of them are flowing lakes. Many rivers can flow into the lake, but only one flows out (the Angara from Lake Baikal, the Neva from Lake Ladoga, etc.). Lakes that do not have a runoff into the oceans - drainless(Caspian, Aral, Big Salt). The water level in such lakes is subject to fluctuations of different duration, which is primarily due to long-term and seasonal changes climate. At the same time, the morphometric characteristics of lakes and the properties of water masses change. This is especially noticeable on lakes in arid regions, which are predicted to have long cycles of humidification and aridity of the climate.

The waters of the lakes, like others natural waters, are characterized by different chemical composition and varying degrees mineralization.

According to the composition of salts in the water, the lakes are divided into three types: carbonate, sulfate, chloride.

By degree of mineralization lakes are divided into insipid(less than 1% o), brackish(1-24.7% s), salty(24.7-47% o) and mineral(more than 47% c). Baikal can serve as an example of a fresh lake, the salinity of which is 0.1% c \ brackish - the Caspian Sea - 12-13% o, the Big Salt - 137-300% o, the Dead Sea - 260-270% o, in some years - up to 310% s.

In the distribution of lakes with varying degrees of mineralization on the earth's surface, geographical zoning is traced, due to the coefficient of moisture. In addition, those lakes into which rivers flow are distinguished by low salinity.

However, the degree of mineralization can be different within the same lake. So, for example, in the endorheic Lake Balkhash, located in the arid zone, in the western part, where the river flows into. Or, the water is fresh, and in the eastern part, which is connected to the western part only by a narrow (4 km) shallow strait, the water is brackish.

When the lakes are oversaturated from the brine, the salts begin to precipitate and crystallize. Such mineral lakes are called self-planting(for example, Elton, Baskunchak). Mineral lakes in which lamellar fine needles are deposited are known as mud.

plays an important role in the life of lakes thermal regime.

Fresh lakes of the hot thermal zone are characterized by the most warm water at the surface, with depth it gradually decreases. This distribution of temperature over depth is called direct thermal stratification. Lakes of the cold thermal zone have the coldest (about 0 ° C) and light water at the top for almost the entire year; with depth, the water temperature rises (up to 4 ° C), the water becomes denser, heavier. This distribution of temperature over depth is called reverse thermal stratification. Lakes of the temperate thermal zone have a variable stratification according to the seasons of the year: direct in summer, reverse in winter. In spring and autumn there come moments when the vertical temperature is the same (4 °C) at different depths. The phenomenon of temperature constancy over depth is called homothermy(spring and autumn).

The annual thermal cycle in lakes of the temperate zone is divided into four periods: spring heating (from 0 to 4 °C) is carried out due to convective mixing; summer heating (from 4 °C to maximum temperature) - by molecular heat conduction; autumn cooling (from maximum temperature to 4 °C) - by convective mixing; winter cooling (from 4 to 0 ° C) - again by molecular heat conduction.

IN winter period freezing lakes, the same three phases are distinguished as those of rivers: freezing, freezing, opening. The process of formation and melting of ice is similar to rivers. The lakes are usually covered with ice for 2-3 weeks longer than the rivers of the region. The thermal regime of freezing salt lakes resembles that of the seas and oceans.

Dynamic phenomena in lakes include currents, waves and seiches. Stock currents occur when a river flows into a lake and outflow of water from the lake into the river. In flowing lakes, they can be traced throughout the entire water area of ​​the lake, in stagnant lakes - in areas adjacent to the mouth or source of the river.

The height of the waves on the lake is less, but the steepness is greater compared to the seas and oceans.

The movement of water in lakes, along with dense convection, contributes to the mixing of water, the penetration of oxygen into the lower layers, and the uniform distribution of nutrients, which is important for a wide variety of lake inhabitants.

By nutritional properties of the water mass and the conditions for the development of life, lakes are divided into three biological types: oligotrophic, eutrophic, and dystrophic.

Oligotrophic- low-nutrient lakes. These are large deep transparent lakes with greenish-blue water, rich in oxygen, so organic residues are intensively mineralized. Due to the small amount of biogenic elements, they are poor in plankton. Life is not rich, but there are fish, crustaceans. It's many mountain lakes, Baikal, Geneva, etc.

Eutrophic lakes have a high content of nutrients, especially nitrogen and phosphorus compounds, are shallow (up to 1015 m), well heated, with brownish-green water. The oxygen content decreases with depth, which is why fish and other animals die in winter. The bottom is peaty or silty with an abundance of organic remains. In summer, there is a "bloom" of water due to the strong development of phytoplankton. The lakes are rich in flora and fauna. They are most common in forest-steppe and steppe zones.

Dystrophic lakes are poor in nutrients and oxygen, they are shallow. The water in them is acidic, slightly transparent, brown due to the abundance of humic acids. The bottom is peaty, there are few phytoplankton and higher aquatic vegetation, animals too. These lakes are common in heavily wetlands.

In the last decade, under the conditions of increased supply of phosphorus and nitrogen compounds from the fields, as well as the discharge of wastewater from some industrial enterprises, eutrophication of lakes has been observed. The first sign of this unfavorable phenomenon is a strong bloom of blue-green algae, then the amount of oxygen in the reservoir decreases, silts form, and hydrogen sulfide appears. All this will create unfavorable conditions for the life of fish, waterfowl, etc.

The evolution of lakes occurs in different ways in wet and dry climates: in the first case, they gradually turn into swamps, in the second, into salt marshes.

In a humid (humid) climate, the leading role in filling the lake and turning it into a swamp belongs to vegetation, partly to the remains of the animal population, which together form organic remains. Temporary streams and rivers bring mineral deposits. Small lakes with gently sloping shores are overgrown by pushing vegetative ecological zones from the periphery to the center. Eventually the lake becomes a grassy fens.

Deep lakes with steep banks overgrow in a different way: by growing from above alloys(quick) - a layer of living and dead plants. It is based on plants with long rhizomes (cinquefoil, watch, calla), and other herbaceous plants and even shrubs (alder, willow) settle on a grid of rhizomes. The raft first appears near the coast, protected from the wind, where there is no excitement, and gradually moves towards the lake, increasing in power. Part of the plants dies, falls to the bottom, forming peat. Gradually, only “windows” of water remain in the quagmire, and then they disappear, although the basin is not yet filled with sediments, and only with time does the raft merge with a layer of peat.

In dry climates, lakes eventually become salt marshes. This is facilitated by an insignificant amount of precipitation, intense evaporation, a decrease in the inflow of river waters, and the deposition of solid sediments brought by rivers and dust storms. As a result, the water mass of the lake decreases, the level decreases, the area decreases, the concentration of salts increases, and even fresh lake may first turn into salt Lake(Great Salt Lake in North America), and then into the salt marsh.

Lakes, especially large ones, have a softening effect on the climate of the surrounding areas: it is warmer in winter and cooler in summer. So, at coastal weather stations near Lake Baikal, the temperature in winter is 8-10 °C higher, and in summer by 6-8 °C lower than at stations outside the influence of the lake. The air humidity near the lake is higher due to increased evaporation.

A lake is a body of water that forms on the surface of the land. Lakes do not have a direct connection to the oceans and seas. Most of the reservoirs are tectonic lakes. In total, on our planet, they occupy almost two percent of the land surface.

Characteristics of lakes

After a long study of the lakes, scientists have identified a number of characteristics inherent in this type of water bodies.

1. Water surface area.
2. Coastline length.
3. The length of the lake To measure this, the two most remote points of the coastline are taken. During the measurement, the average width is determined - this is the ratio of area to length.
4. The volume of the basin, which is filled with water, is determined.
5. The average depth of the reservoir is set, and the maximum depth is also determined.

The largest lake in the world is the Caspian, and the deepest is Baikal.

Origin of lakes

All existing lakes are divided into underground and terrestrial. The basins themselves can be of endo- and exogenous origin. This factor determines the shape and size of the reservoir. Tectonic lakes are located in the largest basins. They can be located in tectonic depressions, like Ilmen, in grabens (Baikal), or in foothill and mountain foredeep.

Most of the large basins have a complex tectonic origin. Discontinuous, folded movements participated in their formation. All tectonic lakes are different large size and significant depths, the presence of rocky slopes. The bottom of most reservoirs is located at the level of the World Ocean, and the mirrors are much higher.

Some regularity can be traced in the location of tectonic lakes: they are concentrated along the faults of the earth or in rift zones, but they can frame shields. Examples of such lakes are Ladoga and Onega, located along the Baltic Shield.

Lake types

There is a classification of lakes according to the water regime.

1. Drainless. Rivers flow into these types of reservoirs, but none of them flows out. Most of them are located in areas with insufficient humidity: in the desert, semi-desert. This type includes the Caspian Sea-lake.
2. Waste. Rivers flow into these lakes, and they also flow out of them. Such species are most often found in the zone of excessive moisture. A different number of rivers flow into such lakes, but usually only one flows out. An example of a tectonic lake of a sewage type is Baikal, Teletskoye.
3. Flowing reservoirs. Many rivers flow into and out of these lakes. Examples are lakes Ladoga and Onega.

In any reservoir, food occurs due to precipitation, rivers, and underwater resources. Partially, water evaporates from the surface of reservoirs, flows out or goes underground. Due to this feature, the amount of water in the pool fluctuates. For example, Chad covers an area of ​​about twelve thousand square kilometers during a drought, but during the rainy season, the basin covers an area twice as large - about 24 thousand square kilometers.

The largest lakes in the world are of tectonic origin. An example would be Baikal, Ladoga and Lake Onega. Big endogenous factors play a role in the origin of tectonic lakes. The basins of these reservoirs are formed on the sunken parts of the earth's crust. Typically, such basins are strongly elongated and deep.

Baikal

The deepest and largest lake in the world with fresh water. Baikal is located in Siberia. The area of ​​this basin is more than 31 thousand square kilometers, the depth is over 1500 meters. If you look at Baikal in terms of water volume, then it takes only the second place after the Caspian Sea-lake. The water in Baikal is always cold: in summer - about nine degrees, and in winter - no more than three. The lake has twenty-two islands: the largest is Olkhon. 330 rivers flow into Baikal, but only one flows out - the Angara.

Baikal influences the climate of Siberia: it softens winters and makes summers cooler. The average temperature in January is about -17 °C, and in summer +16 °C. In the south and in the north, a different amount of precipitation falls throughout the year - from 200 to 900 mm. From January to May Baikal is covered clear ice. This is due to very clean and transparent water - you can see everything that happens in the water at a depth of up to forty meters.

Other types of reservoirs

There are glacial-tectonic lakes that have arisen as a result of the processing of tectonic depressions in the earth's crust by glaciers. Examples of such lakes are Onega, Ladoga. In Kamchatka and the Kuriles are volcanic lakes. There are lake basins that appeared due to continental glaciations.

In the mountains, some lakes were formed due to blockages, for example, Lake Ritsa in the Caucasus. Small reservoirs arise above karst failures. There is a saucer different lakes arising on loose rocks. Melting permafrost can form shallow lakes.

Lakes of glacial-tectonic origin are located not only in the mountains, but also on the plains. The waters fill the hollows, literally plowed by glaciers. During the movement of the glacier from the northwest to the southeast along the cracks, the ice, as it were, made a furrow. It filled with water: this is how many reservoirs were formed.

Ladoga lake

One of the largest glacial-tectonic lakes is Ladoga. It is located in the Leningrad region and in Karelia.

The area of ​​​​the lake is more than seventeen thousand square kilometers: the width of the reservoir is almost 140 kilometers, and the length is 219 km. The depth throughout the entire basin is uneven: in the northern part it ranges from eighty to two hundred meters, and in the south - up to seventy meters. Ladoga is fed by 35 rivers, and only one - the Neva - takes its beginning.

There are many islands on the lake, among which the largest are Kilpola, Valaam, Mantinsari.

Lake Ladoga freezes in winter and opens in April. The water temperature on the surface is uneven: in the northern part it is about fourteen degrees, and in the south - about twenty degrees.

The water in the lake is hydrocarbonate type with weak mineralization. It is clean, transparency reaches seven meters. Throughout the year there are storms (they are strongest in autumn), calm (most often in summer).

Onega and other lakes

Most of the islands Onega Island A: there are more than a thousand of them. The largest of them is Klimetsky. More than fifty rivers flow into this reservoir, and only the Svir takes its beginning.

There are many tectonic lakes in Russia, among which there is a drainage basin, including Ilmen, Saima, Lake Onega.

There are lakes of similar origin in Krasnaya Polyana, for example Khmelevsky. Their formation was served by a deflection that arose in the process of destruction of the earth's crust. The deflections that appeared as a result of this led to the formation of basins that were filled with water. As a result, Khmelevsky lakes were formed in this place, which became a national park. There are four large lakes and several small reservoirs, swamps.

Large lakes located on the territory of Russia have a large economic importance. These are huge reserves of fresh water. Navigation is developed in the waters of many large lakes. On the shores there are recreation centers, equipped fishing spots. In very large lakes, such as Ladoga, fishing is carried out.

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 the rocks that make it up 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. Fig. 3. Scheme of the overgrowth of a deep lake by the formation of quagmires.

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 a large area, a 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.

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. Typical 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. Thus, the 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 various groups 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 clean and cold water.
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 of 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 River, Volta on the Volta River and Kariba on the Zambezi River; the largest in terms of volume 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, and later the formed salt lake is gradually desalinated.

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 silt-clay deposits accumulate, often with big amount organics. 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 salt, and only pure water, then 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 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. For glacial lakes banded clays are characteristic, which are formed due to a combination of lacustrine and glacial deposits. In karst lakes, carbonates accumulate, sometimes heaps of blocks of landslide origin.

Familiarization with varieties, geographical location, temperature regime of waters and chemical composition of lakes in Russia.

Study of the location, area and depth indicators of the largest domestic reservoirs - Baikal, Ladoga and Onega lakes.

By clicking on the "Download archive" button, you will download the file you need for free.
Before downloading this file, remember those good essays, control, term papers, theses, articles and other documents that are unclaimed on your computer. This is your work, it should participate in the development of society and benefit people.

Find these works and send them to the knowledge base.
We and all students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

To download an archive with a document, enter a five-digit number in the field below and click the "Download archive" button

Ecological and geographical characteristics of the lakes of the Moscow region

Consideration of the total number, total area and location of lake natural complexes Moscow region; study of their hydrological, hydrochemical and temperature regime changes.

Acquaintance with the organic world of lakes near Moscow.

presentation, added 02/05/2012

The largest lakes in the world

Geographical significance of lakes, features of their formation and classification.

Genetic types of lakes, thermal regime and life in them. Lakes associated with the activity of rivers. Tectonic, volcanic and glacial lakes.

Characteristics of some large lakes

abstract, added 09/22/2012

Lakes of the Caucasus

General characteristics of the lakes of the Caucasus. Types of lakes by origin, nutrition, regime, chemical composition, their resources and use.

Description of tectonic, volcanic, glacial, water-accumulative, water-erosion lakes and artificial reservoirs.

term paper, added 11/10/2010

Lake Baikal - a natural landmark of Russia

Baikal as the most deep lake on Earth and the largest freshwater reservoir with high-quality clean water.

Study of its location and extent in Russia. Study of the water surface area, maximum depth and volume of lake water. Fauna of Baikal.

presentation, added 10/06/2014

Physical and geographical characteristics of the lakes of Pivnichnaya America

Physical and geographical characteristics of lakes and internal waters of Pivnichnaya America. Hydroresources of lakes and problems of their pollution, recommendations for the improvement of ecosystems. The lakes are a zone of accumulation of mineral and organic rivers (typically lacustrine kopalini).

term paper, added 04/09/2009

Small lakes and rivers of Siberia

General information about Eastern Siberia as one of the largest regions of Russia.

History of its research and study. General characteristics of small rivers and lakes of Eastern Siberia, their hydrological features, value and significance, economic use.

abstract, added 04/22/2011

Biogeography of Lake Ladoga

Study of the history of the formation of Lake Ladoga.

Analysis of the influence of the lake on climatic conditions. The area of ​​the drainage basin and the island. Descriptions of coastal and aquatic vegetation, animal world. Description of the main environmental problems of the lake.

abstract, added 05/16/2013

great african lakes

The concept and features of lakes, assessment of their role and importance in nature, distribution area. general characteristics largest lakes East Africa: Victoria, Albert, Edward, Kivu, Tanganyika, Nyasa, their geographical position and assessment of water reserves.

term paper, added 03/26/2013

Lake Baikal

Formation and development of lakes, their geographical significance in nature: geotectonic features of the Baikal depression and Lake Baikal.

Ecological significance of the aquatic environment of the lake, its flora and fauna.

Technogenic impact on the lake ecosystem.

abstract, added 01/26/2010

Obtaining quantitative estimates of the regulatory capacity of Lake Onega

Hydrography of the catchment area of ​​the Onega Lake basin.

Quantile analysis of long-term variability of hydrometeorological characteristics. Features of long-term instability of temperatures and precipitation. Methods of the theory of periodically correlated random processes.

thesis, added 04/27/2018

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.

The Caspian Lake is the largest 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.

Because of the landslides in the 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. There are estuary lakes on the coast of the Black and Azov Seas.

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).

Hello dear readers! Now I will tell you about what lakes are and about their main types.

- these are natural reservoirs in the depressions of the land (hollows), filled within the lake bowl (lake bed) with a heterogeneous water mass.

Lack of direct connection with the World characteristic of lakes. The area occupied by the lakes is about 2.1 million km 2 or almost 1.4% of the land area, which is almost seven times the surface of the big lake in the world - the Caspian Sea (424,300 km 2).

Lakes are unevenly distributed: in the north there are especially many of them - in the forest zone and tundra, less often lakes are found in the south, in the desert and in the steppe.

Lake types.

Lakes can have different origins. Geographers classify lakes according to the presence of life, the content of salts, and the way they are formed. There is no life only in the most salty lakes. Most of the lakes were formed as a result of volcanic eruptions or movements.

Also, lakes can form in depressions that have arisen as a result of the uneven distribution of glaciers in areas of continental icing. (moraine and glacial lakes); when ice melts in subsidence dips (thermokarst lakes); in castrate abysses and funnels (fire lakes); in valleys blocked by collapse, glacier or displacement (volcanic lakes of Java, the Kuril Islands, etc.), by applying a mule or sand (estuary lakes of the Crimean Peninsula).

Many lakes were created by people. These lakes are called reservoirs, since they contain a reserve of water for hydroelectric power stations and other economic needs.

Let us consider in more detail the main types of lakes:

Tectonic lakes. These lakes are the most interesting. They occur in places of tectonic faults, as a rule, they are very deep and have an elongated shape.

The deepest lake in the world is Baikal (max. depth - 1620 m, average - 730 m), tectonic in origin. It arose as a result of a break in the block of the earth's crust, as a result of which a depression filled with water appeared.

Due to the formation of the water mass of lakes. Sometimes sea water, which in the geological past filled the basin, is replaced by fresh water. These are the so-called relic lakes, including Onega, Lake Ladoga and the Aral with the Caspian Seas.

The reasons for the formation of the Caspian Sea (the largest lake on Earth) are faults and folds, due to the movement of the earth's crust.

In the depression between the Mangyshlak plateau in the East and the Caucasus Mountains in the West, the Caspian Sea is located. Its dimensions have been constantly changing over the past few million years.

The Caspian Sea connected with the Black Sea before the Caucasus Range rose.

Another example of a huge fault is the East African Rift System. It is filled with a chain of lakes and extends from Southeast Africa to the North to Southwest Africa. The most famous of the lakes of this system are Nyasa (Malawi), Albert, Tanganyika, Edward.

On the territory of Israel, but the same system belongs to the lowest-lying lake in the world - the Dead Sea (-399 m, below sea level).

Lakes can also sewage(from them flow, or their flow may be underground) and drainless(they do not have drains, they are mainly found in deserts and semi-deserts).

The endorheic Lake Chany is very interesting, it is prone to abrupt changes in boundaries, depending on fluctuations in annual or seasonal rainfall. Nomadic lakes include: Chad, Lop Nor and Eyre.

The hydrological and thermal regimes of lakes are not as pronounced as those of rivers, due to the large volume of water.

During the period of floods and floods, there are no such impressive rises of water on the lakes, and freezing and ice drift occur more slowly than in rivers. But there are strong winds on the lakes, including seiches.

freshwater lakes they feed on rainwater, streams and rivers, but minerals and soils that are washed off the banks gradually accumulate with a limited supply of fresh water. The fresh water evaporates and the mineral-rich brine remains in the lake.

Salt lakes. More-less, endorheic lakes mineralized, they accumulate salts (from 1 to 24.7% - brackish lakes, and from 24.7 to 47% - salty), which are located even in fresh water their tributaries.

There are also mineral lakes (they contain more than 47% of salts), including flowing ones, they are formed due to the flow of mineralized waters from the depths of the Earth. Salts from them may precipitate.

in the Aral Sea and Caspian Sea are salt lakes. The Aral Sea was the fourth largest lake in the world, but after the channels of the rivers replenishing it were changed, it began to dry up.

The area of ​​the sea has decreased from 77,451 km 2 to 40,000 km 2, and this gives reason to talk about the gradual death of the lake.

The Dead Sea is the saltiest lake. It is located in the Jordan Valley between Jordan and Israel. Its water is 9 times saltier than ocean water. As a result of this, the density of water is so high that on its surface you can lie quietly, as if on a bed, and read a newspaper.

Volcanic lakes. A water-filled volcanic crater is the most common form of volcanic lake.

Crater Lake in Mazama Volcano Crater, Oregon () – one example of this type of lake. This lake has a diameter of 10 km and a depth of 598 m, and was formed 6600 years ago.

Some lakes were formed when lava flows blocked volcanic valleys and water accumulated in them. Lake Kivu is such an example, a depression in the East African Rift System on the border between Rwanda and Zaire.

Once flowing from Lake Tanganyika, the Ruzizi River flowed through the Kivu Valley north to the Nile, but after a nearby volcano erupted, which blocked the river's course, its waters filled the depression.

In the northern hemisphere, the most common lakes were created by glaciers during the last ice age. This is how the lakes of the Italian Alps, about 60,000 Finnish lakes and most of the British lakes were formed.

Glaciers left behind deep depressions in which warm water accumulated. Moraine (glacial deposits) dammed depressions, forming lakes. An example is the reservoirs of the Lake District in the North of England.

Lakes can also form underground, in limestone voids. Water dissolves limestone, creating water-filled huge caves. Similar lakes can form in areas of underground salt deposits.

artificial lakes. The most famous example of artificial lakes are reservoirs. Among the largest are Lake Mead in the USA, which appeared after the damming of the Colorado River, and Lake Nasser on the border of Sudan and Egypt, which was created by damming the Nile Valley.

All of them serve hydroelectric power stations. Also, many artificial lakes exist for industrial use and to provide water to large settlements. Another example of artificial lakes is decorative small lakes created in parks or just at home in the yard.

Such lakes serve as a decoration, an outdoor aquarium for fish and just a place for birds to take a bath 🙂

These were the main types of lakes, I hope this information will be useful to you 🙂

Most big lakes in the world

* Unstable area