The most salty lakes on earth. Fresh and salt lakes What is the difference between salt lakes and fresh lakes

We remember: What sources feed the lakes? What is evaporation? Keywords:feeding of lakes, waste and endorheic lakes, fresh and salt lakes.

1. Waste and endorheic lakes. The lakes are fed by river, underground runoff and atmospheric precipitation. Depending on the flow of water, the lakes are sewage and endorheic. Lakes with river flow, that is, from which rivers flow, are s t o c h n e lakes, and lakes that do not have a runoff - b i s s o c t i o n e. Waste lakes are located mainly in areas of excessive moisture, drainless - in areas of insufficient moisture.

The level of lakes in connection with the inflow and outflow of water does not remain constant, it changes. Especially large fluctuations in the level of lakes are observed in arid and dry regions. Changes in the area of lakes are associated with this.

** The Australian Lake Eyre North in the rainy season of wet years is a large body of water up to 9300 km 2, and in the dry seasons of dry years, water is retained only in a few bays in the southern part of the lake.

Fresh and salt lakes. According to the amount of dissolved substances, lakes are divided into fresh(salt content less than 1 g per liter of water), salty(from 1 to 24 g of salts per liter) and salty, or min eral(salt content more than 24 g per liter of water). In lakes with high salinity, salts precipitate. Usually sewage lakes are fresh, as the water in them is constantly updated. Endorheic lakes are most often brackish or salty. This is because evaporation dominates the water flow of such lakes. All minerals brought by rivers and groundwater remain and accumulate in the reservoir.

** One of the largest salt lakes on Earth - the Great Salt Lake in North America (salinity from 137 to 300 0 / 00) (Fig. 131). The most salty lake in the world is the Dead Sea - the maximum salinity is 310 ppm.

As a result of sediment deposition and vegetation overgrowth, lakes gradually become shallow, and then turn into swamps. They, like rivers, are the most important natural wealth. Lakes are used for navigation, water supply, fishing, irrigation, recreation, treatment, and obtaining various substances.

1. What are the lakes in terms of water consumption and salinity? 2. Why is the water in endorheic lakes most often brackish or salty? 3. Name the largest lake in your area. How is it used by the local population?

Practical work.

Divide these lakes into two groups (drainage and drainless): Baikal, Caspian Sea, Ladoga, Onega, Victoria, Tanganyika, Aral Sea, Chad, Air North.

Draw a sewage and drainless lake?

3. Describe on the map one of the world's lakes according to the plan (see Appendix 2).

& 45. Glaciers

We remember: What land waters have we studied? Remember what glaciers are. Name the properties of ice .

Keywords:snow, glaciers, continental and mountain glaciers, moraine

1. Glaciers and their formation. Accumulations of ice on the earth's surface are glaciers. They do not have the ice that covers our rivers and lakes in winter.

* On Earth, glaciers occupy an area of about 16.1 million km 2, which is approximately 11% of the land. Glaciers are found in all latitudes, but the largest area of glaciation occurs in the polar regions.

Glaciers are formed as a result of the accumulation and transformation of solid atmospheric precipitation, mainly snow. If more snow falls than it can melt, it accumulates, compacts and turns into transparent bluish ice.

Rice. 132. Scheme of the structure of the glacier

* The height at which as much snow falls in a year as it melts is called the snow boundary (line). In tropical latitudes, the snow limit is located at an altitude of 5000 - 6000 m and drops to the ocean level in polar latitudes. Below this limit, during the year less snow falls than can melt, and therefore its accumulation is impossible. Higher, due to low temperatures, snowfall exceeds its melting, and snow accumulates and transforms into ice. Here is the feeding area of the glacier. From here, ice, being a plastic substance, flows down in the form of a glacial tongue (Fig. 132).

Glaciers are moving slowly. The speed of movement of glaciers in most mountainous countries is from 20 to 80 cm per day, or 100 to 300 m per year. In the ice sheets of Greenland and Antarctica, the ice moves even more slowly - from 3 to 30 cm per day (10 - 130 m per year).

2. Cover and mountain glaciers. Glaciers are divided into cover and mountain.

C o r o v n e, or ma t e r i k o v e, glaciers occupy the surface of the land, regardless of its relief, which does not affect the shape of the glacier (Fig. 133). They have a plano-convex surface in the form of domes or shields. Ice accumulates in the middle part and slowly spreads to the sides. Glacier tongues often descend to the coastal part of the ocean, as, for example, in Antarctica. In this case, blocks of ice break off from it, turning into floating ice mountains - icebergs (Fig. 134).

Rice. 134. Formation of icebergs

The height of icebergs above the water surface is on average 70 - 100 m, most of them are under water.

** One of the icebergs off the coast of Antarctica was 45 km wide and 170 km long with an ice thickness of more than 200 m.

Icebergs move under the influence of currents and winds to warmer latitudes, where they melt. They are dangerous for navigation. Modern ships are equipped with means of their detection.

Continental ice sheets are developed in Antarctica and Greenland, on the islands of the Arctic Ocean. Ice sheets once extended across most of Europe, northern Asia, and North America.

Rice. 133. Ice sheet of Antarctica

* Continental glaciers occupy 98.5% of the area of modern glaciation. Antarctica is almost completely covered with ice (the area not covered with ice is 5% of the total). The average thickness of the ice cover of Antarctica is 2200 m, the maximum is 4776 m. A powerful ice sheet is carried by the island of Greenland .

Mountain glaciers, unlike coverslips, are smaller and differ in a variety of shapes. The shape of mountain glaciers is determined by relief. Some, like caps, cover the peaks, others are located in bowl-shaped depressions on the slopes, and others fill the mountain valleys (Fig. 135).

Rice. 135. Mountain glaciers

* The most common are valley mountain glaciers, which move down from the feeding areas along mountain valleys. They can receive tributaries and have icefalls. The thickness of mountain glaciers is usually 200 - 400 m. The world's largest mountain glaciers are the Malaspina glacier in Alaska in North America (100 km long) and the Fedchenko glacier in the Pamirs in Asia (71 km).

3. Significance of glaciers. Glaciers have large reserves of fresh water. They contain many times more water than rivers and lakes combined. Mountain glaciers often feed streams and rivers.

Glaciers, like flowing waters, change the relief of land. During their movement, they develop glacial valleys, expand and deepen them, erase irregularities that impede their movement, demolish loose rocks, transfer and deposit various materials in other places. At the same time, the work of glaciers takes place where there are no rivers - in high-mountainous and polar countries.

Solid material transported and deposited by glaciers is called sea. Moraine consists of sands, sandy loams, loams, clays, gravel, boulders and is deposited during the melting of glaciers. It composes moraine plains, ridges, hills, uplands (Fig. 136).

1. What natural formations are called glaciers? 2. What is a snow border? 3. How do continental (cover) glaciers differ from mountain ones? 4. What is the importance of glaciers? 5*. Show on a pie chart the ratio of continental and mountain glaciers.

Everyone who was on the beach could make sure that the water in the sea tasted salty. But where does salt come from if fresh water enters the ocean through rains, rivers and? Why the sea is salty and has it always been so - time to figure it out!

How is the salinity of water determined?

Salinity refers to the content of salts in water. Salinity is most commonly measured in ppm » (‰). A ppm is one thousandth of a number. Let's give an example: the salinity of water is 27 ‰, which means that one liter of water (that's about 1000 grams) contains 27 grams of salt.

Fresh water is considered to be water with an average salinity of 0.146 ‰.

Medium the salinity of the oceans is 35 ‰. Sodium chloride, also known as table salt, makes the water directly salty. Among other salts, its share in sea water is the highest.

The most salty sea is the Red Sea. Its salinity is 41‰.

Where does the salt in the seas and oceans come from

Scientists still disagree about whether sea water was originally salty or acquired such properties over time. Depending on the versions, different sources of the appearance of salts in the World Ocean are also considered.

Rains and rivers

Fresh water always has a small amount of salt, and rainwater is no exception. It always contains traces of substances dissolved in it, which were captured during the passage through the atmosphere. Getting into the soil, rainwater washes away a small amount of salts and eventually brings them to lakes and seas. From the surface of the latter, water evaporates intensively, falls again in the form of rain and brings new minerals from the land. The sea is salty because all the salts remain in it.

The same principle applies to rivers. Each of them is not completely fresh, but contains a small amount of salts captured on land.

Confirmation of the theory - salt lakes

Evidence that salt comes through rivers are the most saline lakes: the Great Salt Lake and the Dead Sea. Both are about 10 times saltier than sea water. Why are these lakes salty?, while most of the world's lakes are not?

Usually lakes are temporary storages for water. Rivers and streams bring water to lakes, and other rivers carry it away from these lakes. That is, water enters from one end, and leaves from the other.

The Great Salt Lake, the Dead Sea and other salt lakes have no outlets. All the water that flows into these lakes leaves only by evaporation. When the water evaporates, the dissolved salts remain in the water bodies. Thus, some lakes are salty because:

rivers carried salt to them;
the water in the lakes evaporated;
salt remained.

Over the years, the salt in the lake water has accumulated to its current level.

Interesting fact: The density of salt water in the Dead Sea is so high that it practically pushes a person out, preventing him from sinking.

The same process made the seas salty. Rivers carry dissolved salts to the ocean. Water evaporates from the oceans to fall again as rain and replenish rivers, but the salts remain in the ocean.

hydrothermal processes

Rivers and rains are not the only source of dissolved salts. Not so long ago, on the ocean floor were discovered hydrothermal vents. They represent places where sea water has seeped into the rocks of the earth's crust, has become hotter and is now flowing back into the ocean. Along with it comes a large amount of dissolved minerals.

underwater volcanism

Another source of salts in the oceans is underwater volcanism - volcanic eruptions underwater. It is similar to the previous process in that sea water reacts with hot volcanic products and dissolves some mineral components.

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.

A lake is a closed 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 reservoirs on our planet are distributed unevenly. The total area of the Earth's lakes is 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 cooling, which fettered the continents repeatedly over the past 2 million years. The result of the ice ages were modern lakes located on the territory of North America and Europe, namely in Canada, Baffin Island, Scandinavia, Karelia, the Baltic States, the Urals and in other areas.

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

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

River lakes appear when some sections of flowing rivers dry up. In this case, the formation of chain reservoirs arising from one river takes place. The second variant of river formations are floodplain lakes, which appear due to water barriers that interrupt the water channel.

Seaside lakes are called estuaries. They appear when lowland rivers are flooded by the waters of the seas or as a result of the lowering of sea coasts. In the latter case, a strip of land or shallow water appears between the newly formed bay and the sea. In estuaries, which appeared from the confluence of the river and the sea, the water has a slightly salty taste.

Karst lakes are earth pits that are filled with the waters of underground rivers. Pit pits are failures of the lithosphere, consisting of limestone rocks. As a result of the failure, the bottom of the reservoir is lined, which affects the transparency of its filled waters: they are crystal clear.

Karst lakes have one distinctive feature - they are periodic in their appearance. That is, they can disappear and form again. This phenomenon depends on the level of underground rivers.

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

Volcanic-type lakes appear in the craters of dormant volcanoes. Such craters have a significant depth and high edges, which impede the runoff and inflow of river waters. This makes the volcanic lake practically isolated. Craters fill with rainwater. The specific location of such objects is often reflected in the composition of their waters. The increased content of carbon dioxide makes them dead, unsuitable for life.

These are reservoirs and ponds. They are created intentionally for the industrial purposes of settlements. Also, artificial lakes can be the result of earthworks, when the remaining earthen pits are filled with rainwater.

Above was a classification of lakes depending on the origin.

Types of lakes by position

It is possible to make a classification of lakes depending on their position in relation to the earth as follows:

Terrestrial lakes are located directly on the surface of the land. These are involved in the constant water cycle.
Underground lakes are located in underground mountain caves.

Mineralization classification

You can classify lakes by the amount of salts as follows:

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

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

Salt lakes in terms of the content of salts in the thickness of their waters resemble oceans. Sometimes the salt concentration of lakes is somewhat higher than in the seas and oceans.

Classification by chemical composition

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

In carbonate lakes, there is an increased concentration of Na and Ca. Soda is mined from the depths of such reservoirs.
Sulfate lakes are considered curative due to the content of Na and Mg in them. In addition, sulfate lakes are a place for the extraction of Glauber's salt.
Chloride lakes are salt lakes, which are the place where common table salt is mined.

Water balance classification

Waste lakes are endowed 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 one flowing one. An excellent example is the large lakes - Baikal and Teletskoye. The water of sewage lakes is fresh.
Endorheic lakes are saline lakes, since the flow of water in them is more active than its inflow. They are located in the desert and steppe zones. Sometimes they produce salt and soda on an industrial scale.

Classification according to the amount of nutrients

Oligotrophic lakes contain a relatively small amount of nutrients. The peculiarities 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.
Eutrophic plants 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, there is an excess of mineral salts, the color of the water is from dark green to brown, which is why the transparency of the water is low.
Dystrophic lakes are extremely poor in minerals. There is little oxygen, the transparency is low, the color of the waters can be yellow or dark red.

Conclusion

The water basin of the Earth is made up of: rivers, seas, oceans, glaciers of the oceans, lakes. There are several types of lake classifications. They have been reviewed in this article.

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

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 ().