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

The lakes of the world 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 salty.

The lakes have a wide variety of 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 salt per liter of water); such lakes are called mineral lakes. It all depends on what kind of 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 the river and lake waters are poorly mineralized.

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

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

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. These lakes, in addition to Lake Tuz in Turkey, include Lake Eyr 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 that you can walk on in summer. This closed lake Tuz is 80 kilometers long, about forty-five kilometers wide and average depth- 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 sevenfold, 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 with a thickness of several centimeters to two meters.

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 salty. The reason for this peculiarity lies in the fact that the Ili River flows into the western part of the lake, and the eastern one lies surrounded by deserts, where the water evaporates very strongly. Therefore on geographical maps the western part of Balkhash is shown in blue, and the eastern part 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, falling into the lake, does not mix with brackish water, but as if floats on it. Freshwater fish live in the upper layer, and sea fish that got into the lake in ancient times stay at the bottom.

The lake is very shallow (2 to 4 meters deep). Its shores are flat and swampy, and from the north the desert rises 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 rivers Shari and Lagoni, flowing into it from the south, feed the "Sahara Sea" with their waters. For a long time, Lake Chad, or Ngi-Bul, as it is called locals, was considered drainless, which was its main riddle... Usually, large, shallow and closed lakes on Earth have completely salty water, and the upper layer of Lake Chad is fresh. The riddle turned out to be simple.

About 900 kilometers northeast of Chad is the vast Bodele Basin, which lies about 80 meters below the lake level. A water stream hidden underground stretches to it from the lake. So, by means of underground runoff, Lake Chad slowly but constantly renews its waters, preventing them from becoming salty.

Even more surprising is the Mogilnoye lake. 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, practically lifeless, consists of liquid silt and is saturated with hydrogen sulfide. The second "floor" is highlighted in cherry color - this color is given to it by purple bacteria. They act as 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 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 water, but not fresh, but slightly brackish. The fifth "floor" is a six-meter layer of clean spring water drinkable. Animal world here it 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 the sea bay. Mogilnoye Lake is separated from the sea only by a small bridge. At high tide, seawater seeps through it where the "sea" layer is. And the distribution of water in the lake by layers is due to the fact that salty water how the heavier is at the bottom, and the fresh lighter is at the top. That is why they do not mix. Oxygen does not enter the depths of the lake, and the bottom becomes contaminated with hydrogen sulfide.

Hydrological types of lakes

The water mass of the lakes is created by atmospheric precipitation and groundwater. Sometimes fresh water replaces sea water that filled the basin in the geological past. These are relict lakes, including the Caspian Sea, Ladoga and Onega lakes.

There are drainage lakes (from which rivers flow out), flowing and internal drainage (without runoff, mainly in semi-deserts and deserts). Very interesting is the drainless lake Chany, which, depending on fluctuations in seasonal or annual precipitation, is subject to sharp changes in shape. The nomadic lakes include: Lop Nor, Airy Chad.

Due to the large volume of water, the hydrological and thermal regimes of the lakes are not as pronounced as those of rivers (see Rivers). On lakes there are no such impressive rises in water during floods and floods, freeze-up and ice drift (most lakes in Russia freeze in winter) are slower than on rivers. But there are strong waves, including seiches.

Fresh and salt lakes

Most of the flowing lakes are fresh and often have a unique quality. drinking water(the most striking example is Baikal). Endless lakes to one degree or another, they are mineralized, they accumulate salts (from 1 to 24.7% - brackish lakes, and from 24.7 to 47% - salty), contained even in the fresh water of their tributaries. There are also mineral lakes (which contain more than 47% salts), including flowing ones, formed due to the inflow of mineralized waters from the depths of the Earth. Salts can precipitate from them. For example, the self-deposited lakes Elton and Baskunchak.

to another river, sea or lake: a) tributary; b) mouth; c) waterfall; d) lake. 3. This river is so immense, you need to swim for several months to understand how much water dominates the Earth here. Its depths - more than 90 meters - are not found in every sea. The river really looks like the sea: after all, standing on one side, 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 the river valley, flooded during the flood of the river, is called: a) the coast; b) meadow; c) floodplain; d) flood. 6. In the past, this lake was connected to the ocean and was the sea. Now this is the most big lake on the planet. a) Baikal; b) Top; c) Ladoga; d) Caspian. 7. Name the longest river in the world: a) Mississippi; b) Rhine; c) Nile; d) Amazon; e) Lena. 8. Which of these lakes is Australian? a) Air; b) Victoria; c) Baikal; d) Michigan. LAND WATERS Option 2 1. The catchment 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 located Niagara Falls? a) in Asia; b) in Europe; c) in the USA. 4. Voids washed out by water in readily soluble rocks are called: a) springs; b) ravines; c) caves. 5. Find a match: 1. Waste lake; 2. A drainless lake. a) Baikal; b) Chad; c) Caspian; d) Aral; e) Top. 6. On which bank of the great Russian river is the city of Kamyshin? a) on the left; b) on the right. 7. Select African rivers: a) Yenisei; b) Congo; c) Nile; d) Mississippi; e) Niger; f) Volga. 8. Which lakes have the following coordinates? Set the correspondence: 1. 7 ° S. NS.; 30 ° East d. 2.53 ° N NS.; 105 ° East 3.62 ° N NS.; 32 ° East e. a) Baikal; b) Tanganyika; c) Ladoga. WATERS OF THE SUSHI Option 3 1. The place where the river begins is called its: a) tributary; b) the source; c) channel; 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" because this lake is the deepest in the world. What lake are we talking about? a) Top; b) Victoria; c) Nyasa; d) Baikal. 3. Which lakes have the following coordinates? Set the correspondence: 1. 12 ° S. NS.; 35 c. etc .; 2.48 ° N NS.; 88 ° W etc .; 3.28 ° S NS.; 137 ° E e. a) Upper; b) Air; c) Nyasa. 4. Choose from the listed water bodies artificial reservoirs: a) Volga-Don canal; b) the Aral Sea; c) Tsimlyansk reservoir; d) the Suez Canal; e) a pond; f) Bering Strait. g) the Parana river. 5. Relate the rivers and continents along which they flow: 1. Africa; 2. North America; 3. Australia; 4. Eurasia; 5. South America... a) Ob; b) Congo; c) Murray; d) Parana; e) Colorado. 6. A sudden rise in the water level in the river is: a) flood; b) flood; c) low water; d) floodplain. 7. Determine where the mouth of the Angara River is located: a) the Caspian Sea; b) the Lena River; c) Lake Baikal; d) the Yenisei River. 8. Lakes from which the rivers originate are called: a) sewage; b) drainless; c) fresh. please help with correct answers !!

Remember: From what sources do the lakes feed? What is Evaporation? Keywords:feeding of lakes, waste and closed lakes, fresh and salt lakes.

1. Waste and closed lakes... The lakes are fed by river, underground runoff and atmospheric precipitation. Depending on the flow rate of water, the lakes are wastewater and endless. Lakes that have a river flow, that is, from which rivers flow out, are so c e lakes, and lakes that have no runoff - unsteady... Waste lakes are found mainly in areas of excessive moisture, closed-drain - in areas of insufficient moisture.

The level of lakes in connection with the arrival and discharge of water does not remain constant, it changes. Especially large fluctuations in the level of lakes are observed in arid and dry areas. This is associated with changes in the areas of lakes.

** The Australian Lake Air North during the wet season is a large body of water with an area of ​​up to 9,300 km 2, and in the dry seasons of dry years, water is stored only in a few bays of the southern part of the lake.

Fresh and salt lakes... By the amount of dissolved substances, the lakes are divided into nice(salt content less than 1 g in a liter of water), solon about(from 1 to 24 g of salts per liter) and saline, or m in eral(salt content is more than 24 g in a liter of water). In lakes with high water salinity, salts precipitate. Usually sewage lakes are fresh, as the water in them is constantly renewed. The drainless lakes are most often brackish or salty. This is because evaporation predominates in the discharge of water in such lakes. All minerals brought by rivers and groundwater remain and accumulate in the reservoir.

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

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

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

Practical work.

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

Draw a drainage and drainless lake?

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

& 45. Glaciers

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. The accumulations of ice on the earth's surface are glaciers. They are not the kind of ice that covers our rivers and lakes in winter.

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

Glaciers form as a result of the accumulation and transformation of solid atmospheric precipitation, mainly snow. If more snow falls than it can melt, it builds up, compacts and turns into clear bluish ice.

Rice. 132. Scheme of the structure of the glacier

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

Glaciers move slowly. The speed of movement of glaciers in most mountainous countries ranges from 20 to 80 cm per day or 100 - 300 m per year. In the ice sheets of Greenland and Antarctica, 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 glaciers.

C o r n e, or mother, ice occupy the land surface regardless of its relief, which does not affect the shape of the glacier (Fig. 133). They have a flat-convex surface in the form of domes or shields. Ice accumulates in the middle and slowly spreads to the sides. Glacier tongues often descend on the coastal ocean, such as in Antarctica. In this case, chunks 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 detecting them.

Continental ice sheets are developed in Antarctica and Greenland, on the islands of the Arctic Ocean. Once the ice sheets spread over most of Europe, North Asia and North America.

Rice. 133. Antarctica Cover Glacier

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

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

Rice. 135. Mountain glaciers

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

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

Glaciers, like flowing waters, alter the topography of the land. During their movement, they create 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 highland and polar countries.

The solid material transported and deposited by glaciers is called m o r e n about. Moraine consists of sands, sandy loams, loams, clays, gravel, boulders and is deposited during the melting of glaciers. It composes moraine plains, ridges, hills, hills (Fig. 136).

1. What natural formations are called glaciers? 2. What is a snow boundary? 3. What is the difference between continental (cover) glaciers and mountain glaciers? 4. What is the significance of glaciers? 5*. Show the ratio of continental and mountain glaciers on a pie chart.