On our planet there are a huge number of lakes.They can be strikingly different from each other, both in size, origin, and other indicators. Then what are they similar, and what is a lake in general?
To give a precise definition of this concept is not sosimply. For example, if you say that this is a body of water, surrounded on all sides by land, this will not be entirely correct. Since those in which the rivers flow (or flow out of them), the coastline is broken.
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, lakes differ in size with each other. Sometimes in the mountains you can find small, only a few tens of meters in length, while the largest lake on Earth - the Caspian Sea - has a length of more than 1000 kilometers.
Rainwater flows into lakes, rivers flow into themand streams, so they should be in low points of the terrain. But this is not always respected. South American lake Titicaca is located at an altitude of 3812 meters above sea level.
How are they formed
To understand what a lake is, you need tofind out how they arise. There are glacial reservoirs located in the troughs of the earth's surface, formed under the great weight of an ancient glacier. These depressions were gradually filled with melt glacial waters. Most often they are placed in large groups, have small sizes and depths. There are many of them in Finland, Canada, and Siberia.
Mountain lakes are located in the high mountainhollows. Sometimes it happens that such a lake arises right before your eyes - in case of mountain falls, the riverbed is blocked and water accumulates near the dam that has arisen. Usually they are short-lived, and the water quickly erodes the barrier, but there are exceptions. An example is the Lake Sarez in the Pamirs.
The 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. Such is the deepest lake Baikal in the world.
Reservoirs of tectonic origin may haveand shallow depth, such as Khmelevskie Lake, which are located in the eastern part of the ridge Achishkho. Four drainless reservoirs are filled with fresh water, not a single stream flows into them and does not flow out either.
Some lakes have water due to the largethe amount of impurities in its composition is not only salty, but also turbid, which gives it a different color. But most reservoirs, especially small in size, have fresh and clean water. For example, in the Leningrad Region there is the Nameless Lake, which is considered one of the cleanest in Russia. The reason for this is the presence of a large number of springs and keys, constantly updating and refreshing water.
Some of the lakes regularly change theirdimensions, and on the maps their coastline is denoted conditionally. Most often it depends on seasonal rainfall. Thus, Lake Chad on the African mainland may change several times throughout the year.
