A 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 of river flow. 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, usually nothaving runoff, the s alt content increases due to evaporation. As a result of this process, there is a significant change in the s alt and mineral composition of the lakes. Due to the large thermal inertia, large objects soften the climatic conditions of the adjacent zones, reducing seasonal and annual meteorological fluctuations.
Bottom sediments
When they accumulate, there are significant changes in the relief, the size of lake basins. 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 converted into mountain fossils of organic origin.
Features of education
Reservoirs appear 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 s alts. Only in the most saline lakes are there no livingorganisms. Most of the reservoirs were created due to displacements of the earth's crust or volcanic eruptions.
Classification
According to their origin, water bodies are divided into:
- Tectonic lakes. They are formed due to the filling of cracks in the bark with water. Thus, the Caspian Sea, the largest lake in Russia and the entire planet, was formed by displacements. Before the rise of the Caucasus Range, the Caspian Sea was connected with the Black Sea. Another example of a large-scale fault is the East African Rift Structure. It extends from the southeastern region of the continent north to southwest Asia. Here lies a chain of tectonic lakes. The most famous are the lakes. Albert, Tanganyika, Edward, Nyasa (Malawi). The Dead Sea belongs to the same system. It is considered the lowest tectonic lake in the world.
- River reservoirs.
- Seaside lakes (estuaries, lagoons). The most famous is the Venetian Lagoon. It is located in the northern region of the Adriatic Sea.
- Failing lakes. One of the features of some of these reservoirs is their periodic appearance and disappearance. This phenomenon depends on the specific dynamics of groundwater. A typical example of a karst lake is Lake. Ertsov, located in Yuzh. Ossetia.
- Mountain reservoirs. They are located in the ridge basins.
- Glacial lakes. They are formed when the ice column shifts.
- Dammed lakes. Such reservoirs are formed during the collapse of the mountainous part. An example of such a lake islake Ritsa, located in Abkhazia.
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 since the channel was blocked after the eruption of a nearby volcano, it has filled the hollow.
Other species
Lakes can form in limestone voids. Water dissolves this rock, forming huge caves. Such lakes can occur in areas of underground s alt 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 appearanceis a by-product of them. So, for example, artificial reservoirs are formed in developed quarries. Among the largest lakes, it is worth noting the lake. Nasser, located on the border of Sudan and Egypt. It was formed by damming the valley of the river. Nile. Another example of a large artificial lake is Lake. Mid. It appeared after the installation of a dam on the river. Colorado. As a rule, such lakes serve local hydroelectric power stations, provide water to nearby settlements and industrial zones.
The largest glacial-tectonic lakes
One of the main reasons for the formation of reservoirs is the movement of the earth's crust. Due to this displacement, in some 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 fairly deep depressions behind them. 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 was left 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 predominantlyin 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
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", "ram's foreheads". 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 lakes in Russia are classified as a=2-4 and a=4-10. Deep water zone (over 10 m) of the total volumeis 60-70%, shallow (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.
Distribution
Where, besides Kamchatka, are there tectonic lakes? The list of the most famous reservoirs of the country includes such formations as:
- Sandal.
- Sundozero.
- Palié.
- Randozero.
- Salvilambi.
These reservoirs are located in the Suna river basin. Tectonic lakes are also found in the forest-steppe Trans-Urals. Examples of bodies of water:
- 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, Sandy, 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., andcoastline length - 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 m3). 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.
Location
Baikal lies in a deep depression. It is surrounded by mountain ranges covered with taiga. The area near the reservoir is characterized by a complex, deeply dissected relief. Not far from the lake itself, there is a noticeable expansion of the mountain strip. The ridges here run parallel to each other in the direction from the northwest to the southeast. They are separated by depressions. River valleys run along their bottom, in some places small tectonic lakes are formed. Displacements of the earth's crust take place in this area today. This is indicated by relatively frequent earthquakes near the basin, hot springs coming to the surface, as well as subsidence of large areas of the coast. The water in the lake is blue-green. It is distinguished by exceptional transparency and purity. In some places you can clearly see the stones lying at a depth of 10-15 m, thickets of algae. A white disc, lowered into the water, is visible even at a depth of 40 m.
Distinguishing Features
The shape of the lake is a crescent being born. The reservoir stretches 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 there are still discussions in the scientific community 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.
