Why are some lakes fresh. Classification of lakes and their origin

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

Answer from Zhenok Rain[guru]
On geographical maps, the lakes are painted either blue or lilac. Blue color means that the lake is fresh, and lilac - that it is salty.
The salinity of the water in the lakes is different. 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 is only slightly salty in taste. The concentration of dissolved substances depends on what kind of water the rivers bring them. If the climate is humid and the rivers are full of water, the lakes are fresh. In deserts, there is little rainfall, rivers often dry up or they don’t exist at all, which is why the lakes are salty.
Among the large lakes of the world, most of all 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 the 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, Upper in North America. But the freshest of them should still be considered Lake Benern - the largest of the lakes in Western Europe. Its water is the closest to distilled, there are slightly more soluble minerals in Baikal and Lake Onega.
The freshwater lake of the largest area of the water surface - Lake Superior - one of the Great Lakes of North America. Its area is 83,350 square kilometers.
Mountain glacial lakes are especially poor in salts, the waters of which feed glaciers and snowfields.
If the reservoir is not flowing, then the water in it becomes first slightly brackish, and then salty.
The most saline 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 on foot in summer. This drainless 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 the summer, when the water evaporates, the lake becomes very small, and a dense crust of salt forms on its surface from several 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 oceans. 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 the eastern part is brackish. The reason for this peculiarity lies in the fact that the Ili River flows into the western part of the lake, and the eastern part lies surrounded by deserts, where water evaporates very strongly. Therefore, on geographical maps, the western part of Balkhash is shown blue, and the eastern part is 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, falling into the lake, does not mix with brackish water, but rather floats on it. Freshwater fish live in the upper layer, and marine fish that got into the lake in ancient times stay at the bottom.
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Answer from Department for interaction with POWC[newbie]
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Answer from Albina Sapitsyna[active]
PATAMU))))))

Answer from Katya Shubina[newbie]
Not quite right with stock. and the matter is in feeding the lakes, if the lake is fed from a salty spring (mineral spring), then it is salty. Nearby it is in 10-15 meters.

Answer from Victoria Volgina[newbie]
Salt water becomes in drainless lakes in a hot arid climate. Due to the high evaporation, the salts contained in the water accumulate in the lake, making it salty.

Lake

Lake - a natural closed reservoir formed on the surface of the land in a natural depression. The lake has no direct connection with the oceans. Unlike rivers, water does not flow in lakes.

The lakes on the maps are shown as volume objects in blue. On maps, they need to be shown along the coastline.

The largest lake in the world is the Caspian Sea. This lake is salty. It has no connection with the ocean, therefore it refers to lakes, although it used to be part of the ocean.

Rice. 1. Snapshot of the Caspian Sea

The deepest lake is Baikal, with a depth of 1642 meters. This lake contains 1/5 of all lake waters in the world and is the largest liquid freshwater object! The largest freshwater lake in terms of area in the world is Lake Superior (North America).

Rice. 2. Lake Baikal on the map

Types of lakes by origin of basins

lake basin - the place (deepening) in which the lake is located.

According to the origin of the basins, the following types of lakes are distinguished:

1. Tectonic

2. Glacial

3. Volcanic

4. Staritsy

6. Karst

7. Thermokarst

The deepest lakes tectonic, they are formed in cracks, breaks in the earth's crust during its movement. Examples: Baikal, Teletskoye, Victoria, Tanganyika.

Zaprudnye lakes are formed in the valleys of mountain rivers when the channel is blocked by collapsed rocks, glaciers, etc. Examples: Sarez, Ritsa.

Volcanic (crater) lakes are formed in the craters of extinct volcanoes. Examples: Toba, Kuril, Irasu.

Rice. 4. Kuril lake

Staritsy are formed in the valleys of the old channels of lowland rivers when the direction of the flow of the river and channel changes.

Rice. 5. Scheme of the process of formation of the oxbow lake

Karst lakes are formed as a result of soil failure over voids.

Glacial The lakes were formed as a result of the melting of an ancient glacier. There are many such lakes in the north of Eurasia and North America.

Rice. 6. Lakes of Karelia on the map

Other types of lakes

Lake waters are replenished due to precipitation, rivers, snowmelt, groundwater.

According to the position of the lake are divided into:

1. Ground

2. Underground

According to the water balance, the lakes are divided into:

1. Sewage (at least one river flows from such lakes)

2. Endorheic (rivers do not flow from such lakes)

According to the type of mineralization, the lakes are divided into:

1. Fresh

2. Mineral (salty)

One of the saltiest bodies of water on Earth is the Dead Sea, its salinity can reach 350 ppm! Initially, the lake was called "dead", because. it was thought that living organisms did not live in it due to the high concentration of salt.

Rice. 7. Dead Sea Salts

The highest mountain lake

The highest mountain lake in the world is located at the foot of the highest volcano in the world - Ojos del Salado (South America), which is located at an altitude of 6891 meters above sea level. This unnamed lake is a water-filled crater only 100 meters in diameter and up to ten meters deep.

meteorite lakes

This type of lakes is formed when meteorites fall in meteorite craters, then these craters are filled with water and turn into lakes. Example: Elgygytgyn.

Raspberry lakes

These lakes are distinguished by a light pink color and a pleasant smell. Such properties are given to these lakes by crustaceans, which, dying and decomposing, give salt the aroma of raspberries.

Bibliography

Main

1. Initial course of geography: textbook. for 6 cells. general education institutions / T.P. Gerasimova, N.P. Neklyukov. – 10th ed., stereotype. – M.: Bustard, 2010. – 176 p.

2. Geography. Grade 6: atlas. – 3rd ed., stereotype. – M.: Bustard; DIK, 2011. - 32 p.

3. Geography. Grade 6: atlas. - 4th ed., stereotype. – M.: Bustard, DIK, 2013. – 32 p.

4. Geography. 6 cells: cont. maps: M.: DIK, Drofa, 2012. - 16 p.

Encyclopedias, dictionaries, reference books and statistical collections

1. Geography. Modern illustrated encyclopedia / A.P. Gorkin. – M.: Rosmen-Press, 2006. – 624 p.

1. Federal Institute of Pedagogical Measurements ().

2. Russian Geographical Society ().

3. Geografia.ru ().

The lake is a closed natural body of water. Such reservoirs are classified by volume, water balance, origin and other factors. Today we will consider a list of the freshest lakes. We will also tell interesting facts about them.

Why are lakes fresh?

In order for a lake to form, a depression must appear in the earth's crust as a result of a shift in tectonic plates, a meteorite impact or a glacier. There are also reservoirs formed in the craters of dormant volcanoes.

The water in the reservoir can be mineral, salty, brackish and fresh. In mineral lakes, more than 25% of salt water. So, the salinity of the Dead Sea is 200-300%. It is so salty that you can bask in the sun, lying on the water, as if on an air mattress, and not be afraid to drown.

In saline lakes - 10-12% salt, and in brackish - up to 8%. In fresh waters, the salt content is only 1%.

Salt lakes are found predominantly in arid climates. There, moisture evaporates especially intensively. In addition, sewage lakes, from which at least one river flows, are characterized by lower salinity. The drainless accumulate salt over the centuries of their existence. So, the Dead Sea is actually a closed lake.

Baikal - the deepest lake in the world

Baikal is one of the most unique lakes in the world, being the deepest in the world. This largest reservoir of fresh water, located in Russia, has long been called the sea by the local population. Baikal is located in the northern part of Siberia and still raises many questions from scientists.

The age of the lake, according to one version, is several hundred thousand years. However, according to another, Balkal was formed during the ice age, and its age is millions of years old. The depth of the reservoir is 1642 m.

Some interesting facts about Lake Baikal that you may not have known:

it is distinguished by the purest, almost crystal clear water. It can be drunk even without pre-treatment;
on the coldest days of winter, when Baikal freezes, at its bottom you can see a crack that stretches for 30 km along;
the reservoir is located in a seismically active area. Frequent earthquakes cause storms, during which the wave height reaches 4-5 m;
The poetic name "lake of the sun" was given to the reservoir due to the largest number of sunny days that are observed on its territory.
mystical secrets also did not bypass Baikal. People often drown there, but in one of the weeks of the year the number of victims is especially high. In addition, fishermen often see mirages of past events over the waters of Lake Baikal, and luminous objects are often seen in the sky above the lake. The locals mistake them for UFOs.

Perhaps someday humanity will unravel the mystery of one of the largest freshwater lakes in the world.

Great Upper Lake

Lake Superior, in North America, is part of a group of five reservoirs called the Great. They are interconnected by straits and rivers and occupy a considerable area - 244 sq. m! The most discussed among them is the Upper. This body of water is the largest freshwater lake in the world, with an area of 82.5 thousand square meters. m, the greatest depth is 406 m. Even the famous Baikal, whose area is 31,722 sq. km, is inferior to the upper one. m.

By the standards of our planet, the Upper is one of the youngest natural formations in the crust, since its age does not exceed 10,000 years. For comparison: Baikal is about 25 million years old.

From December to April, the lake is completely covered with ice. In former times, a thick layer of frozen water was used by smugglers to cross on foot to the other side of the reservoir. However, even in warmer months, the water temperature in the lake does not exceed 4 degrees Celsius.

Tanganyika - the longest body of water in the world

Tanganyika holds the title of the longest freshwater lake in the world. The length of its coastline is 1828 m. In terms of volume and depth, the reservoir is second only to the majestic Baikal. Experts estimate its age at 10-12 million years. The average depth of Tanganyika is 570 m, the maximum is 1470. For millions of years of its existence, one of the largest freshwater lakes in the world has not dried up, so its flora and fauna have not changed during this time.

There are 200 species of fish in Tanganyika, 170 species of which live exclusively in these waters. At the same time, 90% of the lake is devoid of most forms of life. Most of the inhabitants of the lake live in the upper layer, saturated with oxygen. Below 100 m the desert depths extend.

The surface of Lake Tanganyika is larger than Belgium.

When the first European explorers visited the reservoir in 1600, they found sturgeons 2.7 meters long and pike reaching 2 meters in length. Today, the main wealth of the reservoir is fish, of which there are 90 species.

Tanganyika Horror

The picturesque shores of the reservoir are a haven for many animals. One of the most interesting and terrifying of its inhabitants is the crocodile Gustav, elevated by the local population to the status of a deity. According to local legends, he accounted for more than three hundred human victims. Perhaps more, since the crocodile often feasts on local sailors.

At the same time, any attempts to catch a seventy-year-old cannibal remain in vain. The attempts made by the hunters end with human casualties and a night snack for Gustav. Even bullets cannot take it, as evidenced by the numerous traces from them on the scales of the crocodile.

Gustav is probably the largest crocodile in the world. Its length can only be guessed from photographs, but it has been established that it reaches 7 m. Today, Gustav is over 70 years old, he continues to grow and terrify the local population. Africans consider him a devil who cannot be killed.

Titicaca - "mountain cougar"

Titicaca is one of the largest freshwater lakes in the world, located in South America. The area of the reservoir is 3872 sq km, the maximum depth is 281 m. The reservoir is located at an altitude of 3812 m above ocean level and is of incredible beauty.

Its name, unusual for our hearing, consists of two words of Spanish origin and is translated as "mountain puma". The name is explained by the location of the reservoir, which is located in the Andes, on the border of Peru with Bolivia. There are more than 40 islands on the surface of the lake, on some of them the leaders of the Inca tribes are buried.

The lake was probably formed over a hundred million years ago. The age of the reservoir is evidenced by the fossilized remains of animals that were found on its banks, as well as a variety of flora and fauna. Titicaca is home to crustaceans, fish and even sharks. Once the lake was a bay, which, as a result of one of the natural disasters, turned into a lake and rose along with the Andes. The latter continue to grow today.

The ancient city of the Aztecs at the bottom of the reservoir

It is known that an ancient city, which is more than 1500 years old, is buried at the bottom of Titicaca. As a result of lengthy excavations, archaeologists have found numerous artifacts - dishes, sculptures and even parts of stone structures. Scientists believe that they have discovered the remains of the Inca civilization - Tiwanaku. Probably, a powerful earthquake or flood destroyed the city, burying local residents under the layers of destroyed structures and the water column.

- the largest in Europe

Lake Ladoga is located in the Republic of Karelia and covers an area of 17,700 square meters. km. This is the largest freshwater lake in Europe with picturesque shores and a maximum depth of up to 233 m in the northern part. It is noteworthy that in the southern part the depth of the reservoir does not exceed 70 m.

Scientists still cannot explain such a sharp change in depth. Perhaps, according to scientist Valery Yurkovitsa, the reason for the formation of the lake was the fall of a meteorite that formed the deep part of the reservoir 40 thousand years ago.

Lake Ladoga arose as a result of a meteorite impact, which formed a crater and became the deep-water part of the reservoir. There are 660 islets on the lake, there is also an incredibly rich flora and fauna.

Some interesting facts about Lake Ladoga:

in ancient times, the Scandinavians and Slavs called the reservoir the sea because of its large size;
one of the most interesting mysteries of the lake is the so-called barrantides. These are sounds of incomprehensible origin, which often appear in the depths, frightening the local population;
in addition, according to many eyewitnesses, the Ladoga monster lives in the lake, resembling the famous Nessie;
only one river flows out of Lake Ladoga - the Neva, but it belongs to the most full-flowing rivers in Europe due to the volumetric catchment of the reservoir;
The water temperature in the lake does not exceed 14 degrees Celsius. Only its southern part warms up to +24 in warm months. The rest of the lake is unsuitable for swimming.

The largest lake in the world

Despite the fact that in this article we are discussing freshwater lakes, it is impossible to ignore the largest body of water in the world.

The Caspian Sea is the world's largest lake with a salinity of 8-12%. Its picturesque shores lie at the border of Europe with Asia and are in the possession of five countries - Russia, Kazakhstan, Azerbaijan, Turkmenistan and Iran. Its area is 3,626,000 km², the maximum depth is 1025 meters.

The Caspian Sea is a kind of unique body of water, which can be classified as an endorheic lake with marine salinity. However, if you delve into the numbers, the salinity level of the Caspian is still lower than in the sea. Therefore, today the Caspian Sea, retaining its former name, is considered a lake.

On geographical maps, the lakes are painted either blue or lilac. Blue color means that the lake is fresh, and lilac - that it is salty.

The salinity of the water in the lakes is different. 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 is only slightly salty in taste. The concentration of dissolved substances depends on what kind of water the rivers bring them. If the climate is humid and the rivers are full of water, the lakes are fresh. In deserts, there is little rainfall, rivers often dry up or they don’t exist at all, which is why the lakes are salty.

Among the large lakes of the world, most of all 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 the rivers are carried away by them into the seas and oceans.

The freshest lakes on the planet- this is Baikal in Asia, Onega and Ladoga in Eastern Europe, Upper in North America. But the freshest of them should still be considered Lake Benern - the largest of the lakes in Western Europe. Its water is the closest to distilled, there are slightly more soluble minerals in Baikal and Lake Onega.

The freshwater lake of the largest area of the water surface - Lake Superior - one of the Great Lakes of North America. Its area is 83,350 square kilometers.

Mountain glacial lakes are especially poor in salts, the waters of which feed glaciers and snowfields.

If the reservoir is not flowing, then the water in it becomes first slightly brackish, and then salty.

The most saline 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 on foot in summer. This drainless 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 the summer, when the water evaporates, the lake becomes very small, and a dense crust of salt forms on its surface from several 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 oceans. 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 the eastern part is brackish. The reason for this peculiarity lies in the fact that the Ili River flows into the western part of the lake, and the eastern part lies surrounded by deserts, where water evaporates very strongly. Therefore, on geographical maps, the western part of Balkhash is shown blue, and the eastern part is 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, falling into the lake, does not mix with brackish water, but rather floats on it. Freshwater fish live in the upper layer, and marine fish that got into the lake in ancient times stay at the bottom.

The lake is very shallow (from 2 to 4 meters deep). Its shores are flat and swampy, and from the north the desert comes close to them. The hot sun dried up 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 Ngi-Bul, as the locals call it, was considered drainless, which was its main mystery. Usually in large, shallow and endorheic lakes on Earth, the water is completely salty, and the upper layer of Lake Chad is fresh. The riddle turned out to be simple.

Approximately 900 kilometers northeast of Chad is the vast Bodele Basin, lying approximately 80 meters below lake level. A water stream hidden under the ground stretched to it from the lake. So, through underground runoff, Lake Chad slowly but constantly renews its waters, preventing them from becoming salty.

Even more surprising is Lake Mogilnoe. It is located on Kildin Island, not far from the northern coast of the Kola Peninsula, and has a depth of 17 meters. The lake consists, as it were, 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" stands out in cherry color - this color is given to it by purple bacteria. They are, as it were, 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 ordinary sea water, and its salinity here is the same as in the sea. This layer is filled with life, jellyfish, crustaceans, stars, sea anemones, sea bass, cod live here. Only they look much smaller than their counterparts at sea. The fourth "floor" is intermediate: the water in it is no longer sea, but not fresh either, but slightly brackish. The fifth "floor" is a six-meter layer of pure spring water suitable for drinking. The fauna here is typical 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 the sea bay. Mogilnoye Lake is separated from the sea only by a small bridge. At high tide, sea water seeps through it in the place where the "marine" layer is located. And the distribution of water in the lake by layers is due to the fact that salt water, as heavier, is at the bottom, and lighter fresh water is at the top. That's why they don't mix. Oxygen does not enter the depths of the lake, and the bottom layers become contaminated with hydrogen sulfide.

An unusual lake called Drutso is located in Tibet. The locals consider it magical. Every 12 years, the water in the lake changes: it becomes either fresh or salty.

Terrestrial reservoirs arose for various reasons. Their creators are water, wind, glaciers, tectonic forces. The water washed out the hollow on the surface of the earth, the wind blew out a depression, plowed and polished the glacier depression, the mountain landslide dammed the river valley - and the bed of the future reservoir is ready. The depressions will be filled with water - a lake will appear.

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

The lakes have the most varied salinity - from fractions of a gram to several tens and hundreds of grams per liter of water. There are, for example, reservoirs in which the water is so saturated with salts that it surpasses the ocean in this respect (35 grams of salts per liter of water); such lakes are called mineral. It all depends on what kind of tribute the rivers bring to them. If the climate is humid and the rivers are full of water, then the rocks in the catchment area are well washed, and therefore the river and lake waters are poorly mineralized.

In a drier climate, where precipitation is scarce and rivers are shallow, their waters contain significantly more salts. Therefore, in the deserts, salt (mineral) lakes are the most widespread. A vivid example of this is Central Kazakhstan, where there are few freshwater lakes, and salty ones are found almost at every step. And yet, among the greatest lakes in the world, freshwater reservoirs predominate.

They are flowing, water does not stagnate in them, salts brought by rivers are discharged into the ocean or sea. And it is worth making such a reservoir drainless - and after some time it will become salty. Take, for example, the Caspian Sea. This huge body of water became largely saline because it had no outlet to the ocean. There were many similar cases on Earth.

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 on foot in summer. This drainless 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 shallow, 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 the summer, when the water evaporates, the lake becomes very small, and a dense crust of salt forms on its surface from several centimeters to two meters thick.