There are a huge number of lakes on our planet. They can differ strikingly from each other both in size, origin, and in other indicators. Then how are they similar, and what is a lake in general?
Give a precise definition of this concept is not so easy. For example, if you say that this is a reservoir surrounded on all sides by land, then this will not be entirely correct. Since those that flow into (or flow from) rivers have broken coastlines.
If we claim that this is a fresh water body, then what about the Dead Sea and others in which the water is s alty? We can say that they have no connection with the oceans. But the well-known Lake Maracaibo, located in South America, is connected to the Caribbean Sea.
So what is a lake? It would be more correct to say that this is a reservoir of natural origin on land. First of all, the lakes differ in size from each other. Sometimes in the mountains you can find small ones, only a few tens of meters long, while the largest lake on Earth - the Caspian Sea - has a length of more than 1000 kilometers.
Rainwater flows into the lakes, rivers and streams flow into them, thereforethey should be located in low points of the terrain. But this is not always observed. South American Lake Titicaca is located at an altitude of 3812 meters above sea level.
How they form
To understand what a lake is, you need to find out how they arise. There are glacial reservoirs located in troughs of the earth's surface, formed under the enormous weight of an ancient glacier. These depressions gradually filled with melted glacial waters. Most often they are placed in large groups, have small sizes and depths. There are many of them in Finland, Canada, Siberia.
Mountain lakes are located in high mountain basins. Sometimes it happens that such a lake appears right before our eyes - during mountain landslides, the riverbed is blocked and water accumulates near the resulting dam. Usually they are short-lived, and water quickly erodes the barrier, but there are exceptions. An example is Lake Sarez in the Pamirs.
Lakes formed in the faults of the earth's crust are elongated, narrow and very deep. There are many of them in Africa: Tanganyika, Nyasa and others. The world's deepest Lake Baikal is one of them.
Reservoirs of tectonic origin can also be of shallow depth, for example, the Khmelev lakes, which are located in the eastern part of the Achishkho ridge. Four endorheic reservoirs are filled with fresh water, not a single stream flows into them and does not flow out either.
Alpine lakes filled with glacial water are only fresh. Here is the Dead Sealocated in a basin so s alty that there is no life in it.
In some lakes, due to the presence of a large amount of impurities in its composition, the water is not only s alty, but also cloudy, which gives it a different color. But most reservoirs, especially small ones, have fresh and clean water. For example, in the Leningrad region there is Lake Bezymyannoye, which is considered one of the cleanest in Russia. The reason for this is the presence of a large number of springs and springs, constantly renewing and refreshing the water.
Some of the lakes regularly change their size, and on the maps their coastline is indicated conditionally. Most often it depends on the seasonal precipitation. So, Lake Chad on the African mainland can change several times during the year.
