Big lakes. tectonic lakes

27.09.2019

- a reservoir formed on the surface of the land in a natural depression. Since the lake does not have a 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;
length coastline - 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. one.

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 large, and most of them have 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. Certain regularities are observed in the location of tectonic lakes: they are concentrated along faults in the earth's crust, either in rift zones (Syrian-African, Baikal), or frame shields: the Great Bear Lake, the Great Slave Lake, the Great North American Lakes, along the Baltic Shield are located along the Canadian Shield - Onega, Ladoga, etc.

lake name	Maximum surface area, thousand km 2	Height above sea level, m	Max Depth, m
Caspian Sea
				North America
Victoria
				North America
				North America
Aral Sea
Tanganyika

Nyasa (Malawi)
Big Bear				North America
Great Slave				North America
				North America

Winnipeg				North America

				North America
Ladoga
maracaibo				South America
Bangweulu

Onega
Tonle Sap

Nicaragua				North America
Titicaca				South America
Athabasca				North America
				North America
Issyk-Kul
Big Salty				North America
				Australia

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.

The uneven accumulation of glacial deposits on the plains is associated with lakes among the hilly and moraine relief: 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.

A special type are 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 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 strongly transformed and even completely displaced and replaced by atmospheric waters (Ladoga and others).

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

Genetic groups of lakes	Continents and parts of the world
Genetic groups of lakes	Western Europe	Overseas Asia	North America	South America	Australia
Glacial
Glacial-tectonic
Tectonic
Volcanic
Karst
Residual
Lagoon
floodplain

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 climate changes. 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.

Lake waters, like other natural waters, are characterized by different chemical composition and varying degrees of 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 warmest water near 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 the winter period of freezing lakes, the same three phases are distinguished as in 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 big 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 thrusting vegetation 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, intensive evaporation, a decrease in the inflow river waters, 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 turn first into a salt lake (Big Salt Lake in North America), and then to 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.

Water surface area.
Coastline length.
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.
The volume of the basin, which is filled with water, is determined.
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.

lake name	Max. surface area, thousand km 2	Max. depth, m	What continent is it on
Caspian lake
			North America
Victoria
			North America
Ladoga
Onega

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 distinguished by their 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.

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.
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.
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. Baikal, Ladoga and Onega lakes can be an example. 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 big lake 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. average temperature in January - about -17 °С, and in summer +16 °С. 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. There are volcanic lakes in Kamchatka and the Kuriles. 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 are saucer-shaped lakes that arise 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 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.

Ladoga lake 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 are on Onega Island: 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. Here 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 stocks. fresh water. Navigation is developed in the waters of many large lakes. On the shores there are recreation centers, fishing places are equipped. In very large lakes, such as Ladoga, fishing is carried out.

Definition 1

In the aspect of planetology, a lake is an object stably existing in space and time, which is filled with a substance in liquid form.

In a geographical sense, it can be represented as a closed depression of land, into which water is systematically. For a sufficiently long period of time, the chemical composition of lakes does not change. The liquid filling it is renewed, but much less frequently than in a river. At the same time, the currents present in it do not act as the main factor by which it is possible to determine the general regime.

Remark 1

Lakes mainly provide a balancing of river flow, as complex chemical reactions take place in their waters.

In the process of interactions, some elements pass into the liquid, while others settle in bottom sediments. In some water bodies that do not have such a runoff, the salt content increases significantly due to evaporation. As a result, there is a cardinal change in the mineral and salt composition of the lakes. Large objects soften the climatic conditions of the territories close to them through large-scale thermal inertia, thereby reducing seasonal and annual weather fluctuations.

Tectonic lakes: characteristics, examples

Definition 2

Tectonic lakes are reservoirs that were formed in areas of faults and shifts in the earth's crust.

Basically, these objects are narrow and deep, and also distinguished by rectilinear steep banks. Such lakes are located mainly in deep through gorges. The tectonic lakes of Russia (examples: Far and Kuril in the territory of Kamchatka) are characterized by a low-lying bottom. Thus, the Kuril reservoir flows in the southern part of Kamchatka, in a colorful deep basin. This area is completely surrounded by mountains. The maximum depth of the lake is about 360 m, and a huge amount of mountain streams constantly flows from the steep banks. The Ozernaya River flows out of this reservoir, along the banks of which quite hot springs come to the surface. In the center of the reservoir there is an island in the form of a small dome-shaped elevation, popularly referred to as the "heart-stone". Not far from the lake there are unique pumice deposits called Kutkhiny Baty. Today, Lake Kurilskoye is considered a reserve and declared a natural zoological monument.

Interestingly, tectonic lakes are located only in explosion pipes and extinct craters. Such reservoirs are often found in European countries. For example, volcanic lakes are observed in the Eifel region (in Germany), near which a weak manifestation of volcanic activity in the form of hot springs is recorded. A water-filled crater is the most common type of such reservoirs.

Example 1

For example, Lake Crater of Mazama Volcano in Oregon formed about 6.5 thousand years ago.

Its diameter reaches 10 km, and the depth is more than 589 m. Part of the reservoir was formed by volcanic valleys in the process of blocking by continuous lava flows, in which water accumulates over time and a lake is formed. This is how the Kivu reservoir appeared, which is a depression of the East African rift structure, which is located on the border of Zaire and Rwanda. Flowing more than 7 thousand years ago from Tanganyika, the Ruzizi River flowed through the Kivu Valley to the northern regions, towards the Nile. But since that period, the channel has been "sealed" in with the eruption of a nearby volcano.

Profile of the bottom of tectonic lakes

Tectonic reservoirs of the world have a clearly defined bottom relief, represented as a broken curve.

Accumulative processes and glacial deposits in the sediments did not have a significant effect on the relief of the lines of the basins, but in a number of special cases the effect can be quite noticeable.

Glacial-tectonic lakes can have a bottom covered with "scars" and "ram's foreheads", which can be observed on rocky shores and islands. The latter are formed mainly from hard rocks, which are practically not amenable to erosion. As a result of this process, a small rate of accumulation of precipitation occurs. Similar tectonic reservoirs of Russia are classified by geographers as: a = 2-4 and a = 4-10. The deep-water surface (over 10 m) of the total volume reaches approximately 60-70%, shallow-water (up to 5 m) - 15-20%. Such lakes are characterized by diverse waters in terms of thermal parameters. The low temperature of bottom waters persists during the period of maximum surface heating. This is due to thermally stable stratifications. Vegetation in these areas is extremely rare, as it can only be found along the coast in closed bays.

Features of the formation of reservoirs

Lakes arise for a variety of reasons. Their natural creators are:

water;
wind;
tectonic forces.

On the earth's surface, basins are often washed out with water. Due to the action of the wind, a depression is created, after which the glacier polishes the depression, and the mountain collapse gradually dams the river valley. This is how the bed for the future reservoir is formed.

By origin, the lakes are divided into:

river reservoirs;
seaside lakes;
mountain reservoirs;
glacial lakes;
dam reservoirs;
tectonic lakes;
failed lakes.

Tectonic lakes appear as a result of filling small cracks in the crust with water. Thus, the shifts formed the Caspian Sea - the largest body of water in Russia and the entire planet. Before lifting Caucasian ridge The Caspian Sea was directly connected with the Black Sea. Another striking example of a large-scale fault in the earth's crust is the East African structure, which extends from the southwestern region of the continent north to southeast Asia. Here is a chain of tectonic reservoirs. The most famous are Tanganyika, Albert Edward, Nyasa. To the same system, experts include the Dead Sea - the lowest tectonic lake in the world.

Seaside lakes are estuaries and lagoons, which are mainly located in the northern regions Adriatic Sea. One of the specifics of failed reservoirs is their systematic disappearance and emergence. This a natural phenomenon depends directly on the unique dynamics of groundwater. An ideal example of this object is Lake Ertsov, located in South Ossetia. Mountain reservoirs are located in ridge basins, and glacial lakes are formed during the displacement of the layer of multi-year ice.

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

general characteristics

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

Bottom sediments

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

Features of education

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

Classification

According to their origin, reservoirs are divided into:

Volcanic reservoirs

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

Other types

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

The largest glacial-tectonic lakes

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

Tectonic lakes: examples, characteristics

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

bottom profile

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

Spreading

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

Sandal.
Sundozero.
Palier.
Randozero.
Salvilambi.

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

Welgi.
Argayash.
Shablish.
Tishki.
Sugoyak.
Kaldy.
B. Kuyash and others.

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

Unique body of water

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

terrain

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

Distinctive features

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

Water

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

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

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

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

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

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