What is the lake and what are its signs? Signs of Lake Baikal (2nd class)

The reservoirs on the planet have a different origin. In their creation, water, glaciers, the earth's crust and wind are involved. The signs of the lake that appeared in this way may be different.

What is a lake

What is a lake, what are its signs? The answer to this question is contained in the textbooks on geography. The lake is a deepening in the earth's crust with water, the renewal of which is slow. Under the action of natural elements, pits are formed. They eventually fill with surface or groundwater. Thus, a new reservoir is obtained.

Scientists-geographers have developed different classifications of lakes by the presence of flora and fauna, salinity and the mode 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 main number of reservoirs is formed by tectonic and volcanic processes. A part of the depressions under the lakes is formed by glaciers during their retreat. More and more reservoirs are created by man for various needs. The least of all lakes have occurred as a result of their separation from the ocean.

The dam lake

Signs of a dam type lake: the presence of a valley overlain by the glacier's descent, a landslide, a collapse of rocks, etc. The varieties of these reservoirs:

• River . Occur during the summer mezhdeni on individual watercourses, the level of which falls in places below the surface of the river bed. The river turns into a chain of lakes, separated by parched areas.
• Floodplain . Another name for them is the old people. If the river paves a shorter path, then in place of the former channel a lake is formed.
• The valley . Appear in mountain gorges, in which there are watercourses. As a result of the massive fall of stones, the channel is covered by a natural dam. It turns out a new lake.
• Coastal: lagoons and estuaries. The first are gulls of small depth, which were fenced off from the sea by a sandy scythe or sediments of rivers. The second - river mouths, flooded by the sea.

Moraine Lakes

Moraines include lakes, which were formed due to the movement of the glacier. The bulk of them appeared in the Quaternary period. During the retreat, the glacier leaves a trail consisting of a large number of debris (sand, gravel, clay, rocks, etc.). Morena remains not an even layer, but creates hills and grooves. After filling with water, the latter become lakes.

What are the 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, Chudsko-Pskov).

Carved Lakes

Their origin is also due to the glacier. The impact of ice cover, firn and weathering led to the appearance of depressions, which subsequently filled with water. You can meet such reservoirs high in the mountains. Signs of the lake (carousel): round or oval shape, small area, level boundary, steep banks, flat bottom.

The place of their formation is hollows on mountain slopes. They accumulate snow and ice, which as a result of repeated melting and freezing deepen the car.

Karst lakes

Karsts called lakes, which arose under the influence of surface and groundwater. The voids beneath the earth are formed as a result of processes of dissolution and removal of the smallest particles of clay. After a while, the soil above this place will fail and a funnel will appear.

Signs of a lake of this type: a karst funnel filled with water. These are also those that were formed in the permafrost regions. A special term for these lakes is the thermokarst.

Deflation, tectonic and volcanic lakes

Deflationary lakes (the second name is eolian) are water-filled intervals between barkhans. The processes of weathering sometimes form depressions, which become the basis of the reservoir. They are also referred to as eolian. This name has ancient Greek roots: Aeolus is the god of the wind.

Tectonic lakes have occurred as a result of active processes in the earth's crust. Usually they are giant in size. Baikal is a typical representative of tectonic lakes.

Volcanic lakes can be found in craters and depressions on the surface of a cooled lava.

Lake Baikal

Baikal is the most famous lake in the Russian Federation. It is located near the center of Asia, and the glory of it spread far beyond the mainland. This is one of the most ancient lakes of the planet, it is approximately 25 million years old. During this time interval, the distance between the banks increased by 2 cm per year. In millions of years the reservoir will become much larger.

The most famous signs of Lake Baikal:

• The greatest depth is 1.62 km.
• The area is 31.5 thousand km ² .
• Contains a fifth of the planet's fresh water. It would take 4 years to fill an empty bed of Baikal with Amazon.
• 336 rivers flow into the lake, the largest of which is Selenga. It accounts for half the amount of water introduced.
• Angara is the only river flowing from Lake Baikal. It built the Irkutsk hydroelectric power station and created the Bratsk water reservoir, the largest on Earth.

The water in the lake has a rich blue color, and its purity is impressive. In June, the transparency of the water is maximum, so you can easily see what is at a depth of 40 m. The salt content in the lake is so low that the rivers flowing into it have more mineralization. This phenomenon does not yet have a scientific explanation. There is a hypothesis according to which Baikal at great depth has a powerful source of almost distilled water.

At the school classes in natural science, they study the signs of Lake Baikal (2nd class). All pupils are aware of the exceptional purity of water. In studying this question, one can not but say about one living being, thanks to which water from the lake is suitable for drinking without prior purification. It is a small crustacean epishura, which lives exclusively in Lake Baikal. He constantly filters the water, passing it through his body. This crustacean is not the only endemic. To this group belong ⅔ representatives of the animal and vegetable world of Lake Baikal. In the lake there are about 2.6 thousand species of living organisms.

In the last century the lake began to undergo a strong anthropogenic impact. On the shore of Lake Baikal, a pulp and paper mill was built, and on the Selenge River - the Central Control Commission. There were many opponents of their commissioning, but the need for these plants was stronger. The effluent of the enterprises has a disastrous effect on the flora and fauna of the lake. Strong chemical substances by the 21st century poisoned about 10 km ^{2 of the} coastal zone. The ability to self-clean Lake Baikal is not unlimited. If a turning point happens, then it will be impossible to save the lake.