What is a lake, and how do lakes differ from each other?

On our planet there is a huge number of lakes. They can differ dramatically from each other in terms of size, origin, and other indicators. Then what are they like, and what is the lake in general?

It is not so easy to give an accurate definition of this concept. For example, if we say that this is a pond surrounded on all sides by land, this will not be entirely correct. Since those in which rivers flow into (or flow out of them), the coastline is broken.

If you say that this is a freshwater pond, then how to be with the Dead Sea and others, in which the water is salty? You can say that they have no connection with the oceans. But the famous Maracaibo Lake, located in South America, connects with the Caribbean Sea.

So what is a lake? It will be most correct to say that this is a reservoir of natural origin on land. First of all, the lakes differ in size. Sometimes in the mountains you can meet small, in length only a few tens of meters, while the largest lake on Earth - the Caspian Sea - has a length of more than 1000 kilometers.

The rain drains into the lakes, rivers and streams flow into them, so they should be 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 are formed

To understand what a lake is, it is necessary to find out how they arise. There are glacial ponds located in the troughs of the earth's surface, formed under the enormous weight of the ancient glacier. These depressions gradually filled with thawed glacial waters. Most often they are placed in large groups, have small sizes and depths. There are a lot of them in Finland, Canada, Siberia.

Mountain lakes are located in high-mountain troughs. Sometimes it happens that such a lake occurs right before our eyes - in case of mountain landslides, the riverbed is blocked, and water accumulates near the dam that has arisen. Usually they are short-lived, and water quickly blurs the barrier, but there are exceptions. An example is the Sarez Lake in the Pamirs.

Lakes formed in the crusts of the earth's crust are elongated, narrow and very deep. They are many in Africa: Tanganyika, Nyasa and others. This is the deepest in the world Lake Baikal.

Reservoirs of tectonic origin may also have a small depth, for example the Khmelevskie lakes, which are located in the eastern part of the Achishkho range. Four drainless reservoirs are filled with fresh water, no stream flows into them and does not flow either.

High-altitude lakes, filled with glacial water, are only fresh. But the Dead Sea, located in the basin, is so salty that there is no life in it.

In some lakes, water, because of the large amount of impurities in its composition, is not only salty, but also cloudy, which gives it a different color. But most water bodies, especially small ones, have fresh and clean water. For example, in the Leningrad region there is Lake Bezymyannoe, 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 their size, and on the maps their coastline is designated conditionally. Most often this depends on seasonal precipitation. So, Lake Chad on the African mainland throughout the year can change several times.