Water bodies on the planet have a different origin. Their creation involves water, glaciers, the earth's crust and wind. The signs of a lake that appeared in this way may be different.
What is a lake?
What is a lake, what are its symptoms? The answer to this question is contained in geography textbooks. A lake is a depression in the earth's crust with water, the renewal of which is slow. Under the influence of natural elements pits are formed. They eventually fill up with surface or groundwater. Thus, a new pond is obtained.
Geographical scientists have developed different classifications of lakes according to the presence of flora and fauna, salinity and the method of formation. At school, the signs of the lake are studied in detail (grade 2).
Lifeless lakes, as a rule, have a high level of mineralization. The majority of water bodies are formed by tectonic and volcanic processes. Some of the depressions beneath the lakes are formed by glaciers during their retreat. More and more water bodies are created by man for various needs. The smallest lakes occurred as a result of their separation from the ocean.
Dam lakes
Signs of a dam-type lake: the presence of a valley blocked by a glacier, landslide, rock collapse, etc. Varieties of these reservoirs:
- River . They occur during the summer low water on separate streams, the level of which in places drops below the surface of the channel. The river turns into a chain of lakes separated by dry plots.
- Floodplain . Their other name is elders. If the river paves a shorter path for itself, then a lake will form on the site of the former channel.
- Valley . Appear in mountain gorges in which there are streams. As a result of the massive fall of stones, the channel is blocked by a natural dam. It turns out a new lake.
- Coastal: lagoons and estuaries. The first are bays of small depth, which were fenced off from the sea by a sand spit or river deposits. The second - river mouths flooded with the sea.
Moraine lakes
Moraines include lakes that formed as a result of glacier movement. The bulk of them appeared in the Quaternary. During the retreat, the glacier leaves behind a trail consisting of a large number of debris (sand, gravel, clay, rocks, etc.). Morena does not remain an even layer, but creates hills and indentations. After filling with water, the latter become lakes.
What are the most visible signs of this type of lake? As a rule, the depth of the reservoir does not exceed 10 m, and the banks have a rugged contour. Most of them have a small area, but there are also large lakes (Seliger, Ilmen, Chudsk-Pskov).
Kar Lakes
These lakes also owe their origin to the glacier. Exposure to ice cover, firn and weathering led to the appearance of depressions, which were subsequently filled with water. You can meet such ponds high in the mountains. Signs of a lake (caravan): round or oval, small area, flat border, steep banks, gently sloping bottom.
The place of their formation is the hollows on the mountain slopes. They accumulate snow and ice, which as a result of repeated melting and freezing deepen the car.
Karst Lakes
Karst are called lakes that arose under the influence of surface and groundwater. Voids underground are formed as a result of the processes of dissolution and removal of the smallest clay particles. After some time, the soil above this place will fail and a funnel will appear.
Signs of this type of lake: a karst funnel filled with water. These include those that were formed in permafrost areas. A special term has been coined for these lakes - thermokarst.
Deflation, tectonic and volcanic lakes
Deflation lakes (their second name is aeolian) are water-filled gaps between dunes. Weathering processes sometimes form depressions, which become the basis of the reservoir. They are also referred to as aeolian. This name has ancient Greek roots: Aeolus - the god of the wind.
Tectonic lakes occurred as a result of active processes in the earth's crust. Usually they are gigantic in size. Baikal is a typical representative of tectonic lakes.
Volcanic lakes can be found in craters and hollows on the surface of cooled lava.
Lake Baikal
Baikal is the most famous lake in the Russian Federation. It is located near the center of Asia, and its fame spread far beyond the mainland. This is one of the oldest lakes on the planet, it is approximately 25 million years old. During the indicated period of time, the distance between the shores increased by 2 cm per year. In millions of years, the body of water will become much larger.
The most famous signs of Lake Baikal:
- The greatest depth is 1.62 km.
- Area - 31.5 thousand km 2 .
- Contains a fifth of the planet’s fresh water. It would take 4 years for the Amazon to fill the empty Baikal bed.
- 336 rivers flow into the lake, the largest of which is the Selenga. It accounts for half of the applied volume of water.
- Angara is the only river flowing from Lake Baikal. The Irkutsk Hydroelectric Power Station was built on it and the Bratsk Reservoir, the largest on Earth, was created.
The water in the lake has a deep blue color, and its purity is impressive. In June, water transparency is maximal, so you can easily see what is located at a depth of 40 m. The salt content in the lake is so low that the rivers flowing into it are more mineralized. This phenomenon has no scientific explanation. There is a hypothesis that Baikal at a great depth has a powerful source of almost distilled water.
At school classes in natural science, they study the signs of Lake Baikal (grade 2). All students are aware of the exceptional purity of water. In studying this issue, one cannot but say about one living creature, thanks to which the water from the lake is suitable for drinking without preliminary purification. This is a small epishura crustacean that lives exclusively in Baikal. He constantly filters the water, passing it through his body. This crustacean is not the only endemic. This group includes ⅔ representatives of the fauna and flora of Lake Baikal. About 2.6 thousand species of living organisms are found in the lake.
In the last century, the lake began to be subjected to strong anthropogenic impact. A pulp and paper mill was built on the shore of Lake Baikal, and a pulp and paper mill on the Selenga River. There were many opponents of their commissioning, but the need for these plants was stronger. Factory runoff has a devastating effect on the flora and fauna of the lake. Strong chemicals by the 21st century poisoned about 10 km 2 of the coastal zone. The self-cleaning ability of Baikal is not unlimited. If a turning point occurs, then it will be impossible to save the lake.