Glacial tectonic lakes are examples. Tectonic lakes: examples, list. Largest glacial-tectonic lakes

The lake is an element of the hydrosphere. This is a body of water that has arisen naturally or artificially. It is filled within its bed with water and has no direct connection with 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 matter in liquid form. In a geographical sense, it is represented as a closed depression of land into which water enters and accumulates. The chemical composition of lakes remains constant for a relatively long time. The substance filling it is renewed, but much less frequently than in the river. At the same time, the currents present in it do not act as the predominant factor determining the regime. Lakes provide regulation. Chemical reactions take place in the waters. During interactions, some elements settle in bottom sediments, others pass into the water. In some bodies of water, which usually do not have a flow, the salt content increases due to evaporation. As a result of this process, a significant change in the salt and mineral composition of the lakes occurs. Due to large thermal inertia, large objects are softened climatic conditions adjacent areas, reducing seasonal and annual meteorological fluctuations.

Bottom sediments

When they accumulate, significant changes occur in the relief and size of lake basins. When reservoirs become overgrown, new forms are formed - flat and convex. Lakes often form barriers to groundwater. This, in turn, causes waterlogging of nearby land areas. There is a continuous accumulation of mineral and organic elements in the lakes. As a result, thick layers of sediment are formed. They change with the further development of reservoirs and their transformation into land or swamps. Under certain conditions, bottom sediments are transformed into rock minerals of organic origin.

Features of education

Ponds arise for a variety of reasons. Their natural creators are wind, water, and 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. This creates a bed for the future reservoir. Once filled with water, a lake appears. In geography, bodies of water are classified depending on the method of formation, the presence of life, and salt concentration. Only the saltiest lakes lack living organisms. Most of reservoirs created due to displacements 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 tubes. 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 Mazama volcano crater in Oregon was formed more than 6.5 thousand years ago. Its diameter is 10 km, and its depth is 589 m. Some of the lakes were formed in the process of blocking volcanic valleys with lava flows. Gradually, water accumulates in them and a reservoir is formed. So, for example, a lake appeared. 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. The Ruzizi flowed north through the Kivu Valley 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 arise in areas of underground salt deposits. Lakes may be artificial. They are usually intended to store water for various purposes. Often, the creation of artificial lakes is associated with various types of excavation work. However, in some cases their appearance is a side effect. For example, artificial reservoirs are formed in mined-out quarries. Among the largest lakes it is worth noting Lake. Nasser, located on the border of Sudan and Egypt. It was formed by damming the river valley. Nile. Another example of a large artificial lake is Lake. Mid. It appeared after the installation of a dam on the river. Colorado. As a rule, such lakes are served by local hydroelectric power stations and provide water to nearby settlements and industrial zones.

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. Ponds 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 quite deep depressions behind them. Melt water accumulated in them. Sediments (moraine) dammed the depressions. This is how reservoirs in the Lake District were formed. At the foot of the town of Bolshoi Arber there is a lake. Arbersee. This body of water remained after the Ice Age.

Tectonic lakes: examples, characteristics

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

Bottom profile

Glacial-tectonic lakes of the world have a sharply defined relief. It is presented in the form of 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. Glacial tectonic lakes may have a bottom covered with “scars.” They are quite clearly visible on islands and rocky shores. The latter are composed mainly of hard rocks. They are weakly susceptible to erosion, which, in turn, causes a low rate of sediment 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 characterized by heterogeneity of water in terms of thermal parameters. During the maximum heating of the surface, the temperature of the bottom waters remains low. 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 in the country includes such formations as:

Sandalwood.
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.
Quiet.
Sugoyak.
Kaldy.
B. Kuyash and others.

The depth of reservoirs on the Trans-Ural Plain does not exceed 8-10 m. Based on their origin, they are classified as lakes of the erosion-tectonic type. Their depressions changed accordingly under the influence of erosion processes. Many reservoirs in the Trans-Urals are confined to ancient river hollows. These are, in particular, tectonic lakes such as Kamyshnoye, Alakul, Peschanoye, 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 its length coastline- 2100 km. The width of the reservoir varies from 25 to 79 km. The total area of the lake is 31.5 square meters. km. This reservoir is considered the deepest on the planet. It contains the largest volume of fresh water on Earth (23 thousand m3). This is 1/10 of the world supply. Complete renewal of water in the reservoir occurs in 332 years. Its age is about 15-20 million years ago. Baikal is considered one of the oldest lakes.

Terrain

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

Distinctive features

The shape of the lake is a nascent crescent. The reservoir stretches between 55°47" and 51°28" north. latitude and 103°43" and 109°58" east. longitude The maximum width in the center is 81 km, the minimum (opposite the Selenga River delta) 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 from the river. Selenga. One river flows out of the lake - the Angara. It should, however, be said that in the scientific community there are still discussions about the exact number of streams flowing into the reservoir. Most scientists agree that there are fewer than 336.

Water

The liquid substance filling the lake is considered unique in nature. As mentioned above, the water is surprisingly transparent 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 indicators, it is approaching the standard - the Sargasso Sea. Its water transparency is estimated at 65 m. During the period of mass algal blooms, the lake’s indicator decreases. Nevertheless, even at this time, in a lull, the bottom can be seen from the boat at a fairly decent depth. High transparency is caused by the activity of living organisms. Thanks to them, the lake is slightly mineralized. The structure of the water is similar to that of distilled water. The importance of the lake Baikal is difficult to overestimate. In this regard, the state provides special environmental protection to this area.

The science of limonology deals with the study of lakes. Based on their origin, scientists distinguish several types, including tectonic lakes. They are formed as a result of the movement of lithospheric plates and the appearance of depressions in the earth's crust. This is how the deepest lake in the world, Baikal, and the largest lake in area, the Caspian Sea, were formed. A large rift has formed in the East African Rift System, where a number of lakes are concentrated:

Tanganyika;
Albert;
Nyasa;
Edward;
Dead Sea (is the lowest lake on the planet).

In their form, tectonic lakes are very narrow and deep bodies of water, with steep banks. Their bottom is usually located below ocean level. It has a clear outline, resembling a curved broken curved line. At the bottom you can find traces of various landforms. The shores of tectonic lakes are made of hard rocks and are poorly eroded. On average, the deep-water zone of lakes of this type is up to 70%, and shallow water - no more than 20%. The water of tectonic lakes is not uniform, but generally has a low temperature.

The largest tectonic lakes in the world

In the Suna River basin there are both large and medium-sized tectonic lakes:

Randozero;
Palier;
Salvilambi;
Sandalwood;
Sundozero.

Among the lakes of tectonic origin in Kyrgyzstan, Son-Kul, Chatyr-Kul and Issyk-Kul should be mentioned. On the territory of the Trans-Ural Plain there are also several lakes formed as a result of a tectonic fault in the solid shell of the earth. These are Argayash and Kaldy, Uelgi and Tishki, Shablish and Sugoyak. In Asia there are also tectonic lakes Kukunor, Khubsugol, Urmia, Biwa and Van.

Europe also has a number of lakes of tectonic origin. These are Geneva and Veettern, Como and Constance, Balaton and Lago Maggiore. Among the American lakes of tectonic origin, the Great North American Lakes should be mentioned. Winnipeg, Athabasca and Great Bear Lake are the same type.

Tectonic lakes are located on plains or in the area of intermountain troughs. They have considerable depth and enormous dimensions. In the process of formation of lake basins, not only folds of the lithosphere take part, but also ruptures in the earth’s crust. The bottom of tectonic lakes is below the ocean level. Such bodies of water are found on all continents of the earth, but the largest number of them are located precisely in the fault zone of the earth’s crust.

The uniqueness of natural lakes lies in a number of their special characteristics. They are characterized by slow water exchange, free thermal conditions, a unique chemical composition, and differences in water levels.

In addition, they create their own microclimate and cause changes in the surrounding landscape. They accumulate mineral and organic substances, some of which are valuable and useful.

Geographical object "lake" (meaning)

There are about 5,000,000 lakes in our world. Lakes on Globe occupy almost 2% of the surface, which is almost 2.6 million km 3. Being a component of the hydrosphere, classical natural lakes, are bodies of natural origin, which are lake bowls of water that do not have direct contact (contact) with the sea or ocean. There is a whole science that studies them - limnology. However, there are also anthropogenic lakes that arose as a result of human activity.

If we consider the lake as geographical feature, then its definition becomes more clear: it is a hole on land with closed edges into which flowing water falls and, as a result, accumulates there.

Characteristics of lakes

To give an accurate description of a particular lake, you need to determine its origin, position (above or underground), type of water balance (waste or not), salinity parameters (fresh or not), its chemical composition etc.

In addition, you need to accurately determine the following parameters: total area water mirror, the total length of the shoreline, the maximum distance between opposite shores, the average width of the lake (calculated by dividing the area by the previous indicator), the volume of water that fills it, its average and maximum depth.

Types of lakes by origin

The generally accepted classification of lakes by origin factor is as follows:

Anthropogenic (artificial) - created by man;
Natural - arose naturally (exogenous or endogenous - either from within the Earth, or as a result of processes on its surface), without human intervention.

Natural lakes, in turn, have their own division based on the principle of origin:

Tectonic - cracks in the earth's crust that have arisen for one reason or another are filled with water. The most famous lake of this type is Baikal.
Glacial - the glacier melts and the resulting water creates a lake in the basin of the glacier itself or any other. Such lakes, for example, are in Karelia and Finland: lakes appeared along the trajectory of the glacier along tectonic cracks.
Oxbow lake, lagoon or estuary - a decrease in water level cuts off part of the river or ocean.
Karst, suffusion, thermokarst, aeolian - leaching, subsidence, thawing, blowing, respectively, create a depression that is filled with water.
A dammed lake occurs when a landslide or earthquake cuts off part of the water surface from the main body of water by a land bridge.
Water often also collects in mountain basins and craters of volcanoes or eruption channels.
And others.

The importance of lakes in nature and for humans

Lakes are natural reservoirs of water that can regulate river flow: receive excess water and, conversely, release part of it when the water level in the river generally decreases. A large water mass has a large thermal inertia, the effect of which can significantly soften the climate of nearby areas.

Lakes are an important object for fishing, organizing salt production, and laying waterways. Water from lakes is often used for water supply. Reservoirs can be used to organize the energy reservoir of a hydraulic installation. Sapropels are extracted from them. Some lake muds have medicinal properties and are used in medicine. The importance of lakes in the planet’s ecosystem can hardly be overestimated; they are an organic element of the entire natural mechanism.

The largest lakes in the world

Among the lakes there are two main record holders:

The Caspian Sea is the largest in area (376,000 km 2), but relatively not deep (30 m);

(Lake Baikal)

Baikal - depth record (1620 meters!).

The average record holders for size in the lake community are tectonic lakes.

A lake is a body of water with slow water exchange. Lakes are classified according to various criteria: by origin (tectonic, volcanic, dammed, glacial, sinkhole, karst, etc.); by salinity (fresh, brackish, saline, brine, etc.); by trophicity (oligotrophic, mesotrophic, eutrophic, etc.); by position in the landscape (lowland, floodplain, highland, etc.); by depth (shallow, deep, extra-deep); by morphology (round, elongated, ribbon-shaped, crescent-shaped, bead-shaped, etc.); by flow (drainless, low-flow, periodically flowing, temporary, relict); by type of use (fishery, water supply, salt mining, sapropel ore, medicinal mud, etc.); according to condition (clean, dirty, overgrown, etc.).

How long do lakes live?

Most often, it is relatively short-lived - several thousand or tens of thousands of years. This applies primarily to glacial and oxbow lakes. Karst, volcanic and especially tectonic lakes can exist for millions and tens of millions of years. For example, one of the lakes in Australia was formed about 700 million years ago.

How many lakes are there on Earth?

An exact count has not yet been made. There are probably about 2 million lakes in Canada and Alaska, about 100 thousand in Finland and the Scandinavian Peninsulas. About 100 thousand in Great Britain and Ireland as well as Denmark, Belgium, Holland and France. Hydrologists believe that there are about 5 million lakes in total on the earth.

Tectonic lakes.

They are formed in places of faults and shifts in the earth's crust. As a rule, these are deep narrow reservoirs with straight steep banks, located in deep through gorges. The bottom of such lakes located in Kamchatka is below ocean level. Tectonic lakes include Dalnee and Kurilskoye. Kuril Lake located in the south of Kamchatka in a deep picturesque basin surrounded by mountains. The greatest depth of the lake is 306 m. Its shores are steep. Numerous mountain streams flow from them. The lake is drainage; the Ozernaya River originates from it. Along the shores of the lake, hot springs come to the surface, and in the middle of it rises an island called the Heart-Stone. Not far from the lake there is a unique outcrop of pumice called Kutkhiny Baty. Currently, the lake is declared a nature reserve and zoological monument.

The profile of the bottom of tectonic lakes is sharply outlined and looks like a broken curve. Glacial deposits and sediment accumulation processes 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 rocks that are poorly susceptible to erosion, which is one of the reasons for the weak sedimentation process. 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 (0-5 m) 15-20%. The waters of the lakes are thermally heterogeneous: during the period of 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 shores of closed bays. Typical lakes in the river basin. The Sunes are large and medium-sized: Palje, Sundozero, Sandal, as well as the very small lakes Salvilambi and Randozero, located on the private catchments of lakes Palje and Sandal.

As a result of the movement of the earth's crust, depressions are formed in some places over time. Tectonic lakes arise in these depressions. Three most large lakes Kyrgyzstan: Issyk-Kul, Son-Kul and Chatyr-Kul were formed tectonically.

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

Lake Baikal. General information

Lake Baikal

Baikal - freshwater lake in the south of Eastern Siberia, it stretched from 53 to 56° N. latitude. and from 104 to 109°30’E. Its length is 636 km, and its coastline is 2100 km. The width of the lake varies from 25 to 79 km. The total area of the lake (mirror area) is 31,500 sq. km.

Baikal is the deepest lake in the world (1620 m). It contains the largest reserves of fresh water on earth - 23 thousand cubic km, which is 1/10 of the world's reserves fresh water. A complete change from this huge amount water loss in Baikal occurs over a period of 332 years.

This is one of the oldest lakes, its age is 15 - 20 million years.

336 rivers flow into the lake, including the Selenga, Barguzin, and Verkhnyaya Angara, and only one river flows out, the Angara. There are 27 islands on Lake Baikal, the largest of which is Olkhon. The lake freezes in January and opens in May.

Baikal lies in a deep tectonic depression and is surrounded by taiga-covered mountain ranges; The area around the lake has a complex, deeply dissected topography. Near Baikal, the mountain range noticeably expands. Mountain ranges stretch here parallel to one another in the direction from northwest to southeast and are separated by basin-like depressions, along the bottom of which rivers flow and lakes are located in places. The height of most of the ridges of Transbaikalia rarely exceeds 1300 - 1800, but the highest ridges reach higher values. For example, hr. Khamar-Daban (peak Sokhor) - 2,304 m, and Barguzinsky ridge. about 3000 m.

Tectonic movements continue here today. This is evidenced by frequent earthquakes in the area of the basin, the release of hot springs and, finally, the subsidence of significant sections of the coast.

The waters of Baikal are blue-green in color and are distinguished by exceptional purity and transparency, often even greater than in the ocean: you can clearly see stones and thickets of greenish algae lying at a depth of 10 - 15 m, and a white disk lowered into the water is visible at a depth of 40 m.

Baikal lies in the temperate climate zone.

Geography of Lake Baikal

Lake Baikal is located in the south of Eastern Siberia. In the shape of a nascent crescent, Baikal stretches from southwest to northeast between 55°47" and 51°28" north latitude and 103°43" and 109°58" east longitude. The length of the lake is 636 km, the greatest width in the central part is 81 km, the minimum width opposite the Selenga delta is 27 km. Baikal is located at an altitude of 455 m above sea level. The length of the coastline is about 2000 km. The area of the water surface, determined at the water line of 454 m above sea level, is 31,470 square kilometers. The maximum depth of the lake is 1637 m, the average depth is 730 m. 336 permanent rivers and streams flow into Baikal, while half of the volume of water entering the lake is brought by the Selenga. The only river flowing from Baikal is the Angara. However, the question of the number of rivers flowing into Baikal is quite controversial; most likely there are fewer than 336. There is no doubt that Baikal is the deepest lake in the world, the closest contender for this title, African lake Tanganyika is behind by as much as 200 meters. There are 22 islands on Lake Baikal, although, as mentioned above, there is no unanimity on this issue. Most large island- Olkhon.

Age of Lake Baikal

Usually in the literature the age of the lake is given as 20-25 million years. In fact, the question of the age of Baikal should be considered open, since the use of various methods for determining age gives values from 20-30 million to several tens of thousands of years. Apparently, the first assessment is closer to the truth - Baikal is indeed very ancient lake.

It is believed that Baikal arose as a result of tectonic forces. Tectonic processes are still ongoing, which is manifested in increased seismicity in the Baikal region. If we assume that Baikal is actually several tens of millions of years old, then it is the oldest lake on Earth.

origin of name

Numerous scientific studies have been devoted to the problem of the origin of the word “Baikal,” which indicates a lack of clarity on this issue. There are about a dozen possible explanations for the origin of the name. Among them, the most probable version is considered to be the origin of the name of the lake from the Turkic-speaking Bai-Kul - rich lake. Of the other versions, two more can be noted: from the Mongolian Baigal - rich fire and Baigal Dalai - big lake. The peoples who lived on the shores of the lake called Baikal in their own way. Evenks, for example, - Lamu, Buryats - Baigal-Nuur, even the Chinese had a name for Baikal - Beihai - North Sea.

The Evenki name Lamu - Sea was used for several years by the first Russian explorers in the 17th century, then they switched to the Buryat Baigal, slightly softening the letter "g" by phonetic replacement. Quite often Baikal is called the sea, simply out of respect, for its violent temper, because the distant opposite shore is often hidden somewhere in the haze... At the same time, a distinction is made between the Small Sea and the Big Sea. Small Sea - what is located between north coast Olkhon and the mainland, everything else is the Big Sea.

Baikal water

Baikal water is unique and amazing, like Baikal itself. It is unusually transparent, clean and saturated with oxygen. In not so ancient times, it was considered healing, and diseases were treated with its help. In spring, the transparency of Baikal water, measured using a Secchi disk (a white disk with a diameter of 30 cm), is 40 m (for comparison, in the Sargasso Sea, which is considered the standard of transparency, this value is 65 m). Later, when massive algae blooms begin, the transparency of the water decreases, but in calm weather the bottom can be seen from a boat at a fairly decent depth. Such high transparency is explained by the fact that Baikal water, thanks to the activity of living organisms living in it, is very weakly mineralized and close to distilled. The volume of water in Baikal is about 23 thousand cubic kilometers, which is 20% of the world's fresh water reserves.

Tectonic lakes are formed in places of faults and shifts in the earth's crust. As a rule, these are deep narrow reservoirs with straight steep banks, located in deep through gorges. The bottom of such lakes located in Kamchatka is below ocean level. Tectonic lakes include Dalnee and Kurilskoye. Kuril 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 shores are steep. Numerous mountain streams flow from them. The lake is drainage; the Ozernaya River originates from it. Hot springs come to the surface along the shores of the lake.

Tectonic basins result from movements of the earth's crust, and many lake basins of tectonic origin have large area and ancient age. They occupy depressions that arise as a result of tectonic movements of the earth's crust: faults, faults, grabens, intermountain and plain troughs. As a rule, they are very deep, some tectonic lakes exceed the sea. It is no coincidence that the Caspian and Aral lakes are called seas. Caspian lake 4 times more than Bely, almost 3 times more than Adriatic and 2 times - Aegean seas. And the deepest lakes in the world - Baikal and Tanganyika - are much deeper than our northern seas - the Barents, Kara, East Siberian and others.

Tectonic processes manifest themselves in different ways. For example, the Caspian Sea is confined to a trough at the bottom of the ancient Tethys Sea. In the Neogene, an uplift occurred, as a result of which the Caspian Basin became isolated. Its waters gradually desalinated under the influence of precipitation and river runoff. Lake basin Victoria in East Africa formed as a result of the uplift of the surrounding land. Big Salt Lake in Utah also arose due to the tectonic uplift of the territory through which the lake previously drained. Tectonic activity often results in the formation of faults (cracks in the Earth's crust), which can become lake basins if the area then undergoes a reverse fault or if a block enclosed between the faults subsides. In the latter case, they say that the lake basin is confined to a graben. Several lakes within East Africa have this origin. rift system. Among them is the lake. Tanganyika, formed about 17 million years ago and characterized by a very great depth (1470 m). Continuing this system to the north are the Dead Sea and Lake Tiberias. Both of them are very ancient. The maximum depth of Lake Tiberias is currently only 46 m. Lake Tahoe on the border of California and Nevada in the USA, Biwa (a source of freshwater pearls) in Japan and Lake Baikal are also confined to the grabens. The bottom profile of tectonic lakes is sharply defined and has the appearance of a broken curve. Glacial deposits and sediment accumulation processes 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 rocks that are poorly susceptible to erosion, which is one of the reasons for the weak sedimentation process. The waters of the lakes are thermally heterogeneous: during the period of 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 shores of closed bays. As a result of the movement of the earth's crust, depressions are formed in some places over time. Tectonic lakes arise in these depressions. The three largest lakes in Kyrgyzstan: Issyk-Kul, Son-Kul and Chatyr-Kul were formed tectonically.