Which lakes are fresh and which are salty. Why is the sea salty, and some lakes even saltier? Types of lakes by location

Earth's bodies of water arose for various reasons. Their creators are water, wind, glaciers, tectonic forces. The water washed out a basin on the surface of the earth, the wind blew out a depression, the glacier plowed out and polished the depression, a mountain collapse dammed the river valley - and so the bed of the future reservoir was ready. The depressions will be filled with water and a lake will appear.

Lakes around the globe are divided into two large groups - fresh and salt water bodies. If less than one gram of salts are dissolved in one liter of water, the water is considered fresh; if there are more salts, then it is salty.

Lakes have very different salinities - from fractions of a gram to several tens and hundreds of grams per liter of water. There are, for example, reservoirs whose water is so saturated with salts that it surpasses ocean water in this regard (35 grams of salts per liter of water); Such lakes are called mineral lakes. All this depends on what tribute the rivers bring them. If the climate is humid and the rivers are full of water, it means that the rocks in the catchment area are well washed, and therefore river and lake waters are weakly mineralized.

In drier climates, where precipitation is scarce and rivers are shallow, their waters contain significantly more salts. That is why salt (mineral) lakes are most widespread in deserts. A striking example of this is Central Kazakhstan, where there are few fresh lakes, and salt lakes are found almost at every turn. And yet, among the world's greatest lakes, fresh water bodies predominate.

They are flowing, the water in them does not stagnate, salts brought by rivers are discharged into the ocean or sea. But if you make such a reservoir without drainage, it will become salty after some time. Take, for example, the Caspian Sea. This huge body of water became largely salty because it did not have access to the ocean. Similar cases there were quite a few on Earth.

The saltiest lakes on our planet can be considered lakes in which the salt content per liter of water is more than 25 grams. Such lakes, in addition to Lake Tuz in Turkey, include Lake Eyre in Australia, the Dead Sea on the Arabian Peninsula, Molla-Kara in Turkmenistan, Lake Dus-Khol in Tuva and others.

In the center of Turkey, south of Ankara, at an altitude of 900 meters above sea level, there is a lake on which you can walk in the summer. This endorheic lake The ace is 80 kilometers long, about forty-five kilometers wide and average depth- two meters. It is not only small, but also very salty - up to three hundred and twenty-two kilograms of salt per ton of water. In spring, due to winter and spring precipitation, the lake overflows and increases almost seven times, occupying a huge area of ​​25,000 square kilometers. In summer, when the water evaporates, the lake becomes very small, and a dense crust of salt forms on its surface, ranging from a few centimeters to two meters thick.

The Dead Sea is the deepest and saltiest of the salt lakes. Its greatest depth is over 400 meters, and it is located 395 meters below the level of the World Ocean. In one liter of water Dead Sea it contains 437 grams of salt.

Some of the lakes are brackish-fresh. The most amazing of them is Lake Balkhash. Its western part is fresh, and its eastern part is brackish. The reason for this uniqueness is that the Ili River flows into the western part of the lake, and the eastern part lies surrounded by deserts, where the water evaporates very strongly. Therefore on geographical maps western part Balkhash is shown in blue, and the eastern one is shown in lilac.

The huge Lake Chad, located on the outskirts of the Sahara, is fresh at the top and brackish at the bottom. Fresh river and rain water, entering the lake, does not mix with brackish water, but seems to float on it. Freshwater fish live in the upper layer, and those that entered the lake in ancient times sea ​​fish stay near the bottom.

The lake is very shallow (from 2 to 4 meters deep). Its shores are flat and swampy, and the desert approaches them closely from the north. The hot sun dried out all the northern and eastern tributaries of Chad, turning them into waterless channels - wadis. And only the Shari and Lagoni rivers flowing into it from the south feed the “Sahara Sea” with their waters. For a long time Lake Chad, or Nghi Boul as it was called local residents, was considered drainless, which was its main mystery. Typically, large, shallow, and endorheic lakes on Earth have completely salty water, while the top layer of Lake Chad is fresh. The riddle turned out to be simple.

About 900 kilometers northeast of Chad is the vast Bodélé Basin, which lies about 80 meters below lake level. A hidden underground water stream stretched towards her from the lake. Thus, through underground flow, Lake Chad slowly but constantly renews its waters, preventing them from becoming salty.

Lake Mogilnoye is even more amazing. It is located on the island of Kildin, near north coast Kola Peninsula, and has a depth of 17 meters. The lake consists of several layers - “floors”. The first “floor” at the bottom of the lake, almost lifeless, consists of liquid silt and is saturated with hydrogen sulfide. The second “floor” is distinguished by a cherry color - this color is given to it by purple bacteria. They are like a filter that traps hydrogen sulfide rising from the bottom. The “third” floor is a “piece of the sea” hidden in the depths of the lake. This is normal sea ​​water, and its salinity here is the same as in the sea. This layer is filled with life, jellyfish, sea crustaceans, stars, sea anemones, sea bass, and cod live here. They just look much smaller than their counterparts in the sea. The fourth “floor” is intermediate: the water in it is no longer sea, but also not fresh, but slightly brackish. The fifth “floor” is a six-meter layer of clean spring water, suitable for drinking. Animal world here is common for freshwater lakes.

The unusual structure is explained by the history of the lake. It is very ancient and was formed on the site of a sea bay. Mogilnoye Lake is separated from the sea only by a small bridge. At high tide, seawater seeps through where the "sea" layer is located. And the distribution of water in the lake by layers is due to the fact that salt water how the heavier one appears at the bottom, and the insipid, lighter one appears at the top. That's why they don't mix. Oxygen does not reach the depths of the lake, and the bottom becomes contaminated with hydrogen sulfide.

into another river, sea or lake: a) tributary; b) mouth; c) waterfall; d) lake. 3. This river is so vast, you need to swim for several months to understand how much the water here dominates the Earth. Not every sea has its depth - more than 90 meters. The river really seems like a sea: after all, standing on one bank, you cannot see the other at all. What river are we talking about? a) Volga; b) Limpopo; c) Lena; d) Amazon. 4. The highest waterfall in the world: a) Angel; b) Iguazu; c) Victoria; d) Ilya-Muromets. 5. The part of the bottom of a river valley that is flooded during a river flood is called: a) bank; b) meadow; c) floodplain; d) flood. 6. In the past, this lake was connected to the ocean and was a sea. Now this is the most big lake on the planet. a) Baikal; b) Upper; c) Ladoga; d) Caspian. 7. Name the longest river in the world: a) Mississippi; b) Rhine; c) Nile; d) Amazon; d) Lena. 8. Which of these lakes is Australian? a) Air; b) Victoria; c) Baikal; d) Michigan. WATER OF LAND Option 2 1. Drainage area of ​​the river and its tributaries: a) flood; b) river system; c) river basin; d) source. 2. The deepest river in our country: a) Lena; b) Volga; c) Yenisei; d) Cupid. 3. Where is it located? Niagara Falls? a) in Asia; b) in Europe; c) in the USA. 4. Voids washed out by water in easily soluble rocks are called: a) springs; b) ravines; c) caves. 5. Find a match: 1. Sewage lake; 2. Endorheic lake. a) Baikal; b) Chad; c) Caspian; d) Aral; d) Upper. 6. On which bank of the great Russian river is the city of Kamyshin located? a) on the left; b) on the right. 7. Select the rivers of Africa: a) Yenisei; b) Congo; c) Nile; d) Mississippi; e) Niger; e) Volga. 8. Which lakes have the following coordinates? Match: 1. 7° south. sh.; 30° E. 2. 53° N. sh.; 105° E. 3. 62° N. sh.; 32° east d. a) Baikal; b) Tanganyika; c) Ladoga. WATER OF LAND Option 3 1. The place where a river begins is called its: a) tributary; b) source; c) by the riverbed; d) threshold. 2. The basin of this lake appeared 15–20 million years ago. This is one of the oldest lakes in the world. Some scientists see it as a nascent ocean. It is called the “well of the planet”, as this lake is the deepest in the world. What lake are we talking about? a) Upper; b) Victoria; c) Nyasa; d) Baikal. 3. Which lakes have the following coordinates? Match: 1. 12° south. sh.; 35th century d.; 2. 48° N. sh.; 88° W d.; 3. 28° S sh.; 137° east d. a) Upper; b) Air; c) Nyasa. 4. Select artificial reservoirs from the listed water bodies: a) Volga-Don Canal; b) Aral Sea; c) Tsimlyansk reservoir; d) Suez Canal; d) pond; e) Bering Strait. g) Parana River. 5. Match the rivers and the continents through which they flow: 1. Africa; 2. North America; 3. Australia; 4. Eurasia; 5. South America. a) Ob; b) Congo; c) Murray; d) Parana; d) Colorado. 6. A sudden rise in water level in a river is: a) flood; b) flood; c) low water; d) floodplain. 7. Determine where the mouth of the Angara River is: a) Caspian Sea; b) Lena River; c) Lake Baikal; d) the Yenisei River. 8. Lakes from which rivers originate are called: a) waste lakes; b) drainless; c) fresh. please help me with the correct answers!!

why lakes are salty and others are fresh and got the best answer

Answer from Rain Wives[guru]
On geographical maps the lakes are colored either blue or lilac. Blue color means that the lake is fresh, and lilac means that it is salty.
The salinity of water in lakes varies. Some lakes are so saturated with salts that it is impossible to drown in them, and they are called mineral lakes. In others, the water tastes only slightly salty. The concentration of dissolved substances depends on what kind of water the rivers bring to them. If the climate is humid and the rivers are full of water, the lakes are fresh. In deserts there is little precipitation, rivers often dry up or there are none at all, which is why the lakes are salty.
Among the world's largest lakes, most are fresh. This is due to the fact that the water in them is flowing and does not stagnate, which means that the salts brought by rivers are carried away by them into the seas and oceans.
The freshest lakes on the planet are Baikal in Asia, Onega and Ladoga in Eastern Europe, and Verkhneye in North America. But the freshest of them should still be considered Lake Benern - the largest of the lakes Western Europe. Its water is closest to distilled water, with slightly more soluble minerals in Lake Baikal and Lake Onega.
Freshwater lake with the largest water surface area - Lake Superior - one of the Great Lakes North America. Its area is 83,350 square kilometers.
Mountains are especially poor in salts glacial lakes, whose waters are fed by glaciers and snowfields.
If the reservoir is not flowing, then the water in it becomes first slightly brackish and then salty.
The saltiest lakes on our planet can be considered lakes in which the salt content per liter of water is more than 25 grams. Such lakes, in addition to Lake Tuz in Turkey, include Lake Eyre in Australia, the Dead Sea on the Arabian Peninsula, Molla-Kara in Turkmenistan, Lake Dus-Khol in Tuva and others.
In the center of Turkey, south of Ankara, at an altitude of 900 meters above sea level, there is a lake on which you can walk in the summer. This closed lake Tuz has a length of 80 kilometers, a width of about forty-five kilometers and an average depth of two meters. It is not only small, but also very salty - up to three hundred and twenty-two kilograms of salt per ton of water. In spring, due to winter and spring precipitation, the lake overflows and increases almost seven times, occupying a huge area of ​​25,000 square kilometers. In summer, when the water evaporates, the lake becomes very small, and a dense crust of salt forms on its surface, ranging from a few centimeters to two meters thick.
The Dead Sea is the deepest and saltiest of the salt lakes. Its greatest depth is over 400 meters, and it is located 395 meters below the level of the World Ocean. One liter of Dead Sea water contains 437 grams of salt.
Some of the lakes are brackish-fresh. The most amazing of them is Lake Balkhash. Its western part is fresh, and its eastern part is brackish. The reason for this uniqueness is that the Ili River flows into the western part of the lake, and the eastern part lies surrounded by deserts, where the water evaporates very strongly. Therefore, on geographical maps the western part of Balkhash is shown blue, and the eastern part is shown lilac.
The huge Lake Chad, located on the outskirts of the Sahara, is fresh on top and brackish at the bottom. Fresh river and rain water, entering the lake, does not mix with brackish water, but seems to float on it. Freshwater fish live in the upper layer, and sea fish that entered the lake in ancient times stay at the bottom.
Source:

Reply from Department for interaction with POVK[newbie]
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Reply from Albina Sapitsyna[active]
PATAMU))))))

Reply from Katya Shubina[newbie]
Not quite right with the drain. but the point is in recharging lakes if the lake is fed from a salty spring ( mineral spring) then it is salty, for example Lake Yarovoye is itself salty and there is a lake nearby Hot key fresh. Nearby it is 10-15 meters away.

Reply from Victoria Volgina[newbie]
Water becomes salty in endorheic lakes in hot, arid climates. Due to high evaporation, salts contained in the water accumulate in the lake, making it salty.

A lake is an enclosed depression of land filled with water. It has a slow water exchange, unlike rivers, and does not flow into the waters of the oceans, unlike the seas. These bodies of water are unevenly distributed on our planet. Total area The Earth's lakes make up about 2.7 million km 2, or about 1.8% of the land surface.

The lakes have a number of differences among themselves, both in external parameters and in the composition of the water structure, origin, etc.

Classification of lakes by origin

Glacial reservoirs were formed due to the melting of glaciers. This happened during periods of severe cold spells that shackled the continents repeatedly over the past 2 million years. The result of the ice ages were modern lakes located in North America and Europe, namely in Canada, Baffin Island, Scandinavia, Karelia, the Baltic states, the Urals and other places.

Huge blocks of ice, under the weight of their weight, and also due to their movements, formed considerable pits in the thickness of the earth's surface, sometimes even pushing tectonic plates apart. In these pits and faults, after the melting of the ice, reservoirs were formed. One of the representatives of glacial lakes can be called lake. Arbersee.

The reason for the occurrence was the movement of lithospheric plates, as a result of which faults formed in the earth's crust. They began to fill with water from melting glaciers, which led to the appearance of this type of reservoir. The clearest example is Lake Baikal.

River lakes appear when some sections of flowing rivers dry out. In this case, the formation of chain reservoirs arises from one river. The second option for river formations are floodplain lakes, which appear due to water barriers that interrupt the water channel.

Coastal lakes are called estuaries. They appear when lowland rivers are flooded by sea waters or as a result of subsidence sea ​​shores. In the latter case, a strip of land or shallow water appears between the newly formed bay and the sea. In the estuaries that emerged from the confluence of the river and the sea, the water has a somewhat salty taste.

Karst lakes are earthen pits that are filled with the waters of underground rivers. Pits are depressions in the lithosphere consisting of limestone rocks. As a result of the failure, the bottom of the reservoir is lined, which affects the transparency of the waters it fills: they are crystal clear.

Karst lakes have one distinctive feature - they appear periodically. That is, they can disappear and form again. This phenomenon depends on the level of underground rivers.

They are located in mountain basins. They are formed in several ways. Due to mountain collapses that block the river flow and thereby form lakes. The second method of formation is the slow descent of huge blocks of ice, which leave behind deep land depressions - basins that are filled with water from melting ice.

Lakes volcanic type appear in the craters of dormant volcanoes. Such craters have significant depth and high edges, which impedes drains and inflows river waters. This makes the volcanic lake practically isolated. The craters are filled with rainwater. The specific location of such objects is often reflected in the composition of their waters. High levels of carbon dioxide make them dead and unsuitable for life.

These are reservoirs and ponds. They are created intentionally for industrial purposes. settlements. Also, artificial lakes can result from excavation work, when the remaining excavation pits are filled with rainwater.

Above, a classification of lakes was compiled depending on their origin.

Types of lakes by location

A classification of lakes depending on their position in relation to the earth can be made as follows:

1. Land lakes are located directly on the land surface. These participate in the constant water cycle.
2. Underground lakes are located in underground mountain caves.

Classification by mineralization

You can classify lakes according to the amount of salts as follows:

1. Fresh lakes are formed from rainwater, melting glaciers, and groundwater. The waters of such natural objects do not contain salts. In addition, fresh lakes are a consequence of the damming of river channels. The largest fresh lake is Baikal.
2. Salt water bodies are divided into brackish and saline.

Brackish lakes are common in arid areas: steppes and deserts.

Salt lakes resemble oceans in terms of the salt content in their water column. Sometimes the salt concentration of lakes is slightly higher than in the seas and oceans.

Classification by chemical composition

The chemical composition of the Earth's lakes is different, it depends on the amount of impurities in the water. The lakes are named based on this:

1. Carbonate lakes have increased concentrations of Na and Ca. Soda is extracted from the depths of such reservoirs.
2. Sulfate lakes are considered healing due to their Na and Mg content. In addition, sulfate lakes are where Glauber's salt is mined.
3. Chloride lakes are salt lakes, which are the place of production of the usual table salt.

Classification by water balance

1. Sewage lakes are equipped with the help of which a certain amount of water is discharged. As a rule, such reservoirs have several rivers flowing into their basin, but there is always only one flowing out. An excellent example are large lakes- Baikal and Teletskoye. The water of waste lakes is fresh.
2. Endorheic lakes are salt lakes, since the flow of water in them is more active than its inflow. They are located in desert and steppe zones. Sometimes they produce salt and soda on an industrial scale.

Classification by amount of nutrients

1. Oligotrophic lakes contain relatively small amounts of nutrients. The features are the transparency and purity of the waters, the color from blue to green, the depth of the lakes is significant - from medium to deep, the decrease in oxygen concentration closer to the bottom of the lake.
2. Eutrophic ones are saturated with a high concentration of nutrients. The peculiarities of such lakes are the following phenomena: the amount of oxygen sharply decreases towards the bottom, mineral salts are contained in excess, the color of the water is from dark green to brown, which is why the transparency of the water is low.
3. Dystrophic lakes are extremely poor in minerals. There is little oxygen, transparency is low, and the color of the water can be yellow or dark red.

Conclusion

The Earth's water basin consists of: rivers, seas, oceans, glaciers of the world's oceans, lakes. There are several types of lake classifications. They were discussed in this article.

Lakes, like other bodies of water, are the most important natural resources, which are actively used by people in various fields.