Volcanic lakes have salty water. Types of lakes

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

– these are natural bodies of water in the depressions of the land (basins), filled within the lake bowl (lake bed) with a heterogeneous water mass.

Lack of direct connection with the World typical for 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 lake itself. big lake in the world - the Caspian Sea (424,300 km 2).

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

Types of lakes.

Lakes can have different origins. Geographers classify lakes according to the presence of life, salt content and the method of their formation. There is no life only in the saltiest lakes. Most lakes were formed due to volcanic eruptions or movements.

Lakes can also form in depressions that arose as a result of the uneven distribution of glaciers in areas of continental icing. (moraine and glacial lakes); when ice melts in subsidence holes (thermokarst lakes); in caster abysses and craters (fire lakes); in valleys blocked by a landslide, glacier or displacement (volcanic lakes of Java, Kuril Islands etc.), by applying mule or sand (estuary lakes of the Crimean Peninsula).

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

Let's take a closer look at the main types of lakes:

Tectonic lakes. These lakes are the most interesting. They arise 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 (maximum depth - 1620 m, average - 730 m), tectonic in origin. It arose as a result of a fracture in a block of the earth’s crust, which resulted in a water-filled depression.

Due to this, the water mass of lakes is formed. Sometimes sea water, which in the geological past filled the basin, is replaced by fresh water. These are the so-called relict lakes, among which Onega, Lake Ladoga and the Aral and 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 Caucasus mountains in the West, the Caspian Sea is located. Its size has changed constantly over the past few million years.

The Caspian Sea was connected to 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 South-East Africa to North to South-West Africa. The most famous lakes of this system are Nyasa (Malawi), Albert, Tanganyika, Edward.

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

Also lakes can be sewage(they flow from them, or their flow may be underground) and drainless(they have no drainage, they are mainly located in deserts and semi-deserts).

The endorheic Lake Chany is very interesting; it is prone to sudden changes in its boundaries, depending on fluctuations in annual or seasonal precipitation. Lakes that are nomadic 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 periods of floods and high waters, lakes do not experience such impressive water rises, and freeze-up and ice drift occur more slowly than in rivers. But there are strong winds on the lakes, including seiches.

Freshwater lakes They are fed by rainwater, streams and rivers, but the minerals and soils that wash off the banks gradually accumulate with a limited supply of fresh water. The fresh water evaporates, leaving the mineral-rich brine solution in the lake.

Salt lakes. To one degree or another, drainless lakes are mineralized; salts accumulate in them (from 1 to 24.7% are brackish lakes, and from 24.7 to 47% are salty), which are found 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.

To the Aral and Caspian Sea- are salt lakes. The Aral Sea was the fourth largest lake in the world, but after the rivers that fed it were changed, it began to dry up.

The area of ​​the sea 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 you can relax and calmly lie on its surface, like on a bed and read a newspaper.

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

Crater Lake in Mount Mazama 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 volcanic valleys were blocked by lava flows and water accumulated in them. Lake Kivu is an example, a depression in the East African Rift System on the border of Rwanda and Zaire.

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

In the northern hemisphere, the most common lakes are those that 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 British lakes were formed.

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

Lakes can also form underground, in the voids of limestone rocks. The water dissolves the limestone, creating huge caves filled with water. Such lakes can form in areas of underground salt deposits.

Artificial lakes. The most famous example of artificial lakes is reservoirs. Among the largest are Lake Mead in the USA, which appeared after the Colorado River was dammed, 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 for large settlements. Another example of artificial lakes are decorative small lakes created in parks or just in your own yard.

Such lakes serve as decoration, an outdoor aquarium for fish, and simply a place for birds to take a bath :)

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

The most big lakes in the world

Lake	Area thousand km 2
Caspian Sea (Asia – Europe), salty	371*
Upper (USA – Canada)	82,1
Victoria (Kenya, Tanzania, Uganda)	69,4
Huron (USA – Canada)	59,6
Michigan (USA)	57,8
Aral Sea (Kazakhstan – Uzbekistan), salty	36,5*
Tanganyika (DRC, Burundi, Tanzania, Zambia)	32,9
Baikal (Russia)	31,5
Great Bear (Canada)	31,3
Nyasa (Malawi, Tanzania, Mozambique)	29,0
Great Slave (Canada)	28,5
Erie (USA – Canada)	26,5
Winnipeg (Canada)	24,3
Balkhash (Kazakhstan), salted	22,0*
Ontario (USA – Canada)	19,7
Ladozhskoe (Russia)	17,7
Chad (Niger, Chad, Cameroon, Nigeria), brackish	16,3*
Maracaibo (Venezuela)	13,5
Onega (Russia)	9,7
Air (Australia), salted	9,3*
Volta (Ghana)	8,5
Titicaca (Peru – Bolivia)	8,3
Nicaragua (Nicaragua)	8,0
Athabasca (Canada)	8,0
Deer (Canada)	6,7
Rudolph (Kenya – Ethiopia), salted	6,5
Issek-Kul (Kyrgyzstan), salty	6,2
Kokunor (Qinghai) (China), salted	5,7*
Torrens (Australia), salty	5,7*
Vänern (Sweden)	5,7
Albert (DRC – Uganda)	5,6
Nettiling (Canada)	5,4
Vinipegosis (Canada)	5,39
Kariba (Zambia – Zimbabwe)	5,31
Nipigon (Canada)	4,9
Gardner (Australia), salted	4,77*
Urmia (Iran), salted	4,69
Manitoba (Canada)	4,66
Lesnoye (USA – Canada)	4,47

* Unstable area

A lake is a component of the hydrosphere, which is a naturally occurring body of water filled within a lake bowl (lake bed) with water and not having a direct connection with the sea (ocean). Lakes are the subject of study of the science of limnology.

From the point of view of planetology, a lake is an object that exists stably in time and space, filled with a substance in the liquid phase, the dimensions of which occupy an intermediate position between the sea and the pond.

From a geographic point of view, a lake is a closed depression of land into which water flows and accumulates. Lakes are not part of the World Ocean.

Although the chemical composition of lakes remains constant for a relatively long time, unlike a river, the substance filling it is renewed much less frequently, and the currents present in it are not the predominant factor determining its regime. Lakes regulate river flow by retaining hollow waters in their basins and releasing them at other times. Chemical reactions occur in lake waters. Some elements move from water to bottom sediments, others - vice versa. In a number of lakes, mostly without drainage, the concentration of salts increases due to water evaporation. The result is significant changes in the mineralization and salt composition of lakes. Due to the significant thermal inertia of the water mass large lakes soften the climate of adjacent areas, reducing annual and seasonal fluctuations in meteorological elements.

The shape, size and topography of the bottom of lake basins change significantly with the accumulation of bottom sediments. The overgrowing of lakes creates new forms of relief, flat or even convex. Lakes and, especially, reservoirs often create a backwater of groundwater, causing swamping of nearby land areas. As a result of the continuous accumulation of organic and mineral particles in lakes, thick layers of bottom sediments are formed. These deposits are modified by further development bodies of water and turning them into swamps or dry land. Under certain conditions, they transform into rocks of organic origin.

Lake classification

Based on their origin, lakes are divided into:

• Tectonic: formed by filling cracks in the earth's crust. A striking example of a tectonic lake is Lake Baikal.
• Glacial: formed by a melting glacier. Typical glacial lake, a remnant of the last ice age is Arbersee, located at the foot of the Great Arber mountain (1456 m) - the most high mountain Bohemian forest.
• River(or old women).
• Primorskie(lagoons and estuaries). The most famous lagoon is the Venetian lagoon, located in the northern part of the Adriatic Sea.
• Failed(karst, thermokarst). A feature of some sinkhole lakes is their periodic disappearance and reappearance, depending on the peculiar dynamics of groundwater. A typical representative is Lake Ertso in South Ossetia.
• Dammed: formed when part of a mountain collapses (for example, Lake Ritsa in Abkhazia).
• Mountain: located in mountain basins.
• Crater: located in the craters of extinct volcanoes and explosion tubes. In Europe, similar lakes are located in the Eifel region (Germany). Near them there are weak manifestations of volcanic activity in the form of hot springs.
• Artificial(reservoirs, ponds). The creation of such lakes can be an end in itself, for example, for creating reservoirs for various purposes. Often this creation is associated with more or less significant earthworks. But in some cases, such lakes arise as a side effect of such work, for example, in mined-out quarries.

According to their position, lakes are divided into (in relation to planet Earth):

• Ground, the waters of which take an active part in the water cycle in nature and underground waters, the waters of which, if they take part in it, are only indirect. Sometimes these lakes are filled with juvenile, that is, native water.
• Underground. The subglacial lake in Antarctica can also be classified as underground lakes.

According to water balance, lakes are divided into:

• Sewage(have a drainage, mainly in the form of a river).
• Drainless(they do not have surface runoff or underground drainage of water to neighboring watersheds. Water consumption occurs due to evaporation).

By type of mineralization

• fresh;
• ultra-fresh

mineral (salty).

• brackish
• salty

By chemical composition water mineral lakes are divided into

• carbonate (soda)
• sulfate (bitter-salty)
• chloride (salty)

Based on the nutritional value of the substances contained in the lake (trophicity), three types of lakes are distinguished:

• Oligotrophic (with a small amount of nutrients) - lakes are usually characterized by large or medium depths, a significant mass of water below the temperature jump layer, high transparency, water color from blue to green, a gradual drop in O2 content to the bottom, near which the water always contains significant amounts of O2 (at least 60% of its content on the surface)
• Eutrophic (with a high content of nutrients) - well-warmed lakes (the layer below the temperature jump is very small), transparency is low, the color of the water is from green to brown, the bottom is covered with organic silt. The water is rich in nutritious salts, the O2 content drops sharply towards the bottom, where it often disappears completely.
• Dystrophic (poor in nutrients) - swampy lakes with low transparency and yellow or brown (due to the high content of humic substances) water color. The mineralization of water is low, the O2 content is low due to its consumption for the oxidation of organic substances.

In modern hydrology and hydroecology, intermediate levels of trophic classification are distinguished: mesotrophic (between oligotrophic and eutrophic) and hypertrophic.

Based on its location on celestial bodies lakes are divided into:

• earthly;
• extraterrestrial.

The largest lakes on Earth

total area lakes globe makes up about 1.8% of the land (approximately 2.7 million km²).

Lake name	Maximum surface area, thousand km²	Altitude above sea level, m	Maximum depth, m	Part of the world
Caspian Sea
Upper				North America
Victoria
Huron				North America
Michigan				North America (USA)
Tanganyika
Baikal				Asia (Russia)
Malawi
Big Bear
Great Slave				North America (Canada)
Erie
Chad
Winnipeg				North America (Canada)
Balkhash				Asia (Kazakhstan)
Ontario				North America
Aral Sea
Ladoga				Europe (Russia)

Origin, types and morphology of lake basins

Lakes are called basins or depressions the earth's surface, filled with water and not having a direct connection with the sea.

The sizes of lakes vary over 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 area, formed, for example, during the period of spring snowmelt.

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

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

Reservoir -And artificial lake .

Pond -small reservoir .

Pond - natural lakes in which aquatic vegetation is widespread.

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, having similarities in a number of characteristics.

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

By the nature of the basins that served as the basis for the formation of the lake can be distinguished:

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

Among the dam lakes we can distinguish

- river - may arise as temporary formations as a result of a sharp decrease in the flow of individual rivers during the dry season; in this case, rivers often turn into a chain of lakes lying in a 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 sediment and the formation of a new channel by the river.

- valley - arise in the mountains from rubble. Lakes of dammed 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 when shallow bays, or bays, are separated from the sea by alluvial sandy-clayey shafts, or spits.

Estuaries They represent the mouth 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 spaces beneath them. After retreat (melting) and disappearance of such ice sheet in its place remained fragmentary material that the glacier carried with it: clay, sand, crushed stone, large blocks of rock, etc.

A large accumulation of this material (moraine) in some places and insignificant in others creates a relief characterized by hilliness, continuous and frequent alternation of hills 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 moraine landscape there are many lakes that are also of the dam type.

3. Tarn lakes occupy depressions developed during glacial times by the combined action of ice, firn and frost weathering.

4. Karst lakes are the result of the chemical (solvent) 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 craters on the surface of the earth; If these sinkholes are filled with water, karst lakes will appear in their place.

A peculiar variety of karst type lakes are thermokarst lakes , arising as a result of 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 lenses of ice. The melting of this ice not only contributes to the formation of the lake basin, but also largely supplies water to fill the basin.

5. Deflationary lakes are located in basins created as a result of the blowing process, and in depressions between barchans 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. Examples include lakes Issyk-Kul, Baikal, Sevan, etc.

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 drainage, mainly in the form of a river);

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

By chemical composition The lake waters 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 naturally constructed relief that distinguishes it from depressions not occupied by water.

The original shape of the basins changes under the influence of erosion, both by surface runoff into the lake and by waves: the slopes of the basin are flattened, the unevenness of the bottom topography is smoothed out, filled with sediments, and the shore slopes acquire a stable profile.

The section of lake science, which examines the patterns manifested in the formation of the relief of lake basins, is called lake morphology .

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

The main bank ends edge, or line connecting the slopes with the surface of the adjacent area.

The part of the basin filled with water to the height of the maximum rise in level 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 There are three zones:

1) coastal slopes (yar)- part of the lake slope that surrounds the lake on all sides and is not exposed to the effects of wave surf;

2) coast - includes dry part , which is exposed to water only during strong waves and especially when the water is high, floodable , which is covered with water periodically - when the water level of the lake rises, and underwater , which usually lies below the surface of the water and, unlike the deeper parts of the coastal region, is exposed to the action of waves when it is rough;

3) coastal sandbank - 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 shallows corresponds to the lower limit of the impact of the wave surf on the coastal area.

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

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

The coast and the coastal sandbank are combined into one zone - coastal or littoral. Its lower limit is determined by the depth of action of the wave, sometimes by the depth of penetration of sunlight. The deep part of the lake - profundal. Between the littoral and profundal - sublittoral.

Formation of a lake bed under the influence of waves and sediment deposition. Waves, depending on the strength of the wind, the depth and size of the lake, affect the coastal area of ​​the lake basin for a long period, destroy the rocks composing it and carry eroded material down the slopes and to the bottom of the lake. As a result of this, the size of the coast and the erosion shallows increases, while at the same time the area of ​​alluvium increases and decreases due to the deep area of ​​the lake.

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

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

In addition to waves, the shape of the lake bed is significantly influenced by the process of supply of alluvial sediments brought by rivers flowing into the lake. Surface watercourses flowing into the lake erode soils along their route and carry erosion products into the lake.

In addition to mineral sediments that fall into the lake bed as a result of waves or brought by river flows, 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 deposition to the bottom of microscopic animals and plant organisms suspended in the water (the so-called plankton), as well as as a result of the death of coastal vegetation, which disintegrates into tiny particles after rotting, easily carried away by currents to the middle of the lake. The intensive development of these organisms during the warm period of the year, and their death during the cold season, causes 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.

Overgrowing of lakes. The amount of mineral sediments 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 move onto the lake from the shores, bordering the water surface with a wide green ring.

For shallow lakes with flat 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 you can observe alloys - islands of vegetation isolated from the shores or directly adjacent to the mineral shore (Fig. 3). At first, these rafts form small areas, then, as the lake further shallows, they grow, connect with others and cover the lake with a continuous cover of marsh vegetation from grass and moss tiers. These formations are known as muddy.

Rice. 3. Overgrowth pattern deep lake through the formation of alloys.

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

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

These data already allow us to form a general idea of ​​the main features of the lake’s regime. The geographical position of the lake to a certain extent reflects the general climatic characteristics of the area, and the altitude position 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 of 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, is calculated in two ways: either together with the area of ​​the islands, or separately the area of ​​the water surface. Since the shores of lakes are not vertical, the area of ​​the water surface (lake surface) changes as the lake level changes.

Lake length -L, 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 lake outlines; for a winding lake, this line, obviously, may not be straight, but consist of separate segments of straight and curved lines.

Lake width– distinguish:

Largest 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 lake to its length L

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

The coastline tortuosity ratio can also be expressed as the ratio of the coastline length S to the perimeter of the broken line S" , outlining the contour of the lake:

m = S/ S"

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

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

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

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

Volume of water in the lake W , m 3 can be determined from an 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 limited by adjacent isobaths, and the height is equal to the section between them. Having designated the areas limited by individual isobaths through ω 0 , ω 1 , ω 2 , ω 3 … ω n , and their section 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 с – maximum depth of the lake in meters; h n – depth corresponding to the greatest isobath, ω n – area of ​​the last (deepest) isobath.

A lake is a closed depression of land filled with water and not having a direct connection with the ocean. Unlike lakes, they are reservoirs of slow water exchange. The total area of ​​the Earth's lakes is about 2.7 million km2, or about 1.8% of the land surface. Lakes are distributed everywhere, but unevenly. The geographical distribution of lakes is greatly influenced by climate, which determines their nutrition and evaporation, as well as factors contributing to the formation of lake basins. There are many lakes in the regions; they are deep, fresh and mostly flowing. In areas with a dry climate, all other things being equal, there are fewer lakes, they are often low-water, often drainless, and therefore often salty. Thus, the distribution of lakes and their features are determined by geography.

4. Karst lakes, the basins of which arose as a result of failures, soil subsidence and erosion (limestones, gypsum, dolomites). The dissolution of these rocks by water leads to the formation of deep but small lake basins.

5. Dammed (dammed, or dam) lakes arise as a result of blocking the river bed (valley) with blocks of rock during landslides in the mountains (Sevan, Tana, many lakes of the Alps, and other mountain lakes). From a large mountain collapse in 1911, Lake Sarez with a depth of 505 m was formed.

A number of lakes are formed for other reasons:

• estuary lakes are common on the shores of the seas - these are coastal areas of the sea, separated from it by means of coastal spits;
• oxbow lakes are lakes that arose in old river beds.

Based on the origin of the water mass, lakes are of two types.

1. Fresh lakes— the salinity of which does not exceed 1‰ (one ppm).

2. Brackish - the salinity of such lakes is up to 24‰.

3. Salty - with a content of dissolved substances in the range of 24.7-47‰.

4. Mineral (47‰). These lakes are soda, sulfate, and chloride. In mineral lakes, salts can precipitate. For example, self-settling lakes Elton and Baskunchak, where salt is mined.

Usually wastewater lakes are fresh, since the water in them is constantly renewed. Endorheic lakes are often salty, because their water flow is dominated by evaporation, and all minerals remain in the reservoir.

Lakes, like rivers, are the most important natural resources; used by humans for navigation, water supply, fishing, obtaining mineral salts and chemical elements. In some places, small lakes are often artificially created by humans. Then they are also called .

In this article we will talk about what types of lakes there are, as well as how they originated, i.e. consider the general characteristics of the lake. A lake is an inland body of land with low-flow or standing water. It forms near the surface of the earth in a natural depression. Since lakes are not connected to the ocean, they are bodies of slow water exchange. They occupy only about 2% of the planet's land mass. The largest is the Caspian Sea, and the deepest is Baikal. There are various types of lakes, which have heterogeneous origins. Each body of water is distinguished by several interconnected components: basin, water mass, vegetation, fauna.

Characteristics of the lake: origin of lake basins and types of lakes

Endogenous - most large lakes, which are the result of the manifestation of the internal forces of the Earth. Endogenous basins include tectonic and volcanic basins.

Tectonic depressions are subsided zones of the earth's crust. The subsidence occurs due to the deflection of layers (Aral) or faults along cracks (Upper, Baikal, Huron, Michigan). Volcanic depressions are the craters of volcanoes. There are such basins in Kamchatka.

Exogenous – small types of lakes, which were formed by the activities of external forces. Often river valleys have oxbow lakes that have an oblong shape. They appear on the site of former river beds.

Many water basins were formed during the Ice Age. As they moved, the glaciers “plowed out” huge depressions that filled with water.

Similar glacial lake characteristics can be found in northwestern Russia, as well as Canada and Finland. Almost all of them are elongated in the direction of movement of glaciers.

The result of strong earthquakes in the mountains is dams. So, for example, the Sarez reservoir was formed in the Pamirs (1911). During the earthquake, part of the mountain range was thrown onto the river valley, and a dam more than 600 meters deep was formed.

A significant number of recesses are of mixed origin. For example, Onega and Ladoga are tectonic, but the action of glaciers has modified their basins. The Caspian Sea is the remnant of a giant basin that was previously connected to the Black Sea. Depressions created by man are artificial reservoirs.

Mountain lake Ritsa (Abkhazia) is of glacial-tectonic origin

Typeslakes by water regime

1. Sewage - rivers not only flow into them, but also flow out (they may have an underground flow). The data is most often located in the area of ​​excess moisture. A different number of rivers flow into such lakes, but only one flows out (Baikal, Teletskoye).

1. Endorheic - rivers flow in, none of them flow out (i.e. such lakes have no flow). They are located in areas of insufficient moisture (most often deserts, semi-deserts). The Caspian Sea, the Aral Sea, and some tundra water basins belong to the same type.

1. Flowing - many rivers flow in and out (Onega and Ladoga).

Majestic Lake Baikal

The basin is fed by inflowing rivers, precipitation, and groundwater resources. Some of them evaporate from the surface of reservoirs, flow out, and go into underground drainage. And depending on the balance of incoming and outgoing parts, characteristics of lakes And The water level can fluctuate and the area of ​​these water basins changes. For example, Lake Chad during drought covers an area of ​​about 12 thousand square meters. km, during the rainy season - 26 thousand square meters. km.

Salt content

According to the amount of elements dissolved in water, three types of lakes are distinguished: fresh, brackish, salt. So, fresh - salt solution less than 1% o, brackish - more than 1% o, and salty - more than 24.7% o.

They are classified according to the method of their formation, the presence of life and the salt content. Life is absent only in incredibly salty bodies of water.

Lake Salar-Uyuni (Bolivia)

Sewage and flow-through pools are classified as fresh resources, since the influx of water significantly exceeds the flow. Drainless water resources most often brackish or salty. Such reservoirs have an inflow less than the flow. This increases the salinity. Salty - occupy zones of deserts and steppes. (Bolshoye Solenoye, Dead, Elton).

This article discussed the main types of lakes, which are important natural resources. Some of them are rich in raw materials, such as salt, iron ore, sapropel. Lakes are used for water supply, navigation, irrigation, fishing, and the production of a number of chemical elements and mineral salts. Lakes also serve great place for recreation, rest houses, sanatoriums and recreation centers were built next to them.

And more details from characteristics of lakes This video will introduce you.