Geography lesson
8th grade
Subject : Development of landforms
Lesson Objectives:
Subject:
To organize the activities of students to study the development of landforms in Russia and the application of new knowledge in various situations.
2. Metasubject:
Create conditions for consolidating the skills to analyze and systematize information, expanding the experience of students' creative activity.
3. Personal:
To help students realize the social and practical significance of information about the development of Russia's landforms through research, information, communication, project activities and reflective culture of students.
Tasks:
Educational: form an idea of the interaction of internal and external processes as a source of relief development; to acquaint with the features of the formation of the relief on the territory of Russia as a whole and the Kursk region in particular, to show the impact of the impact of society on changing the surface of the Earth.
Developing:
develop meta-subject skills of working with information.
Educational:
to educate a careful and rational attitude to mineral, soil resources, and minerals.
Methods:
Verbal, visual, practical.
Equipment: physical map of Russia, tables, schemes, geographic atlases, contour maps, textbook, rock samples., reference materials, handouts, multimedia projector, laptop, presentation.
During the classes
1. Organizational moment
“There was a wise man who knew everything. One person wanted to prove that the sage does not know everything. Clutching the butterfly in his hands, he asked: “Tell me, sage, which butterfly is in my hands: dead or alive?” And he himself thinks: “The living woman will say - I will kill her, squeezing my hands harder, the dead one will say - I will let her out.” The sage, thinking, replied: "Everything is in your hands."
And it's true, guys, everything is in your hands! It is up to you how our lesson will go, how attentive and active you will be.
2. Repetition. Updating of basic knowledge.
Questions:
From the course of physical geography, remember what relief is?
What landforms do you know?
List the types of plains by height.
List the types of mountains by height.
Test (slide show)
1. The largest deposits are located in Western Siberia:
A) coal
B) non-ferrous metal ores;
B) oil and gas.
2. The Baltic shield is rich:
A) oil and gas
B) ores of ferrous and non-ferrous metals;
B) coal.
3. The accumulation of minerals is ...
A) platform
B) deposit;
In the pool.
4. A group of closely spaced deposits of the same mineral is ..
A) a swimming pool
B) platform.
5. The Lena basin is a deposit
B) coal;
B) natural gas;
D) iron ore. (Mutual check - work in pairs)
Answers: 1. AT); 2. B); 3 .B); 4. BUT); 5. B).
We will continue to "discover" knowledge of the relief of Russia. Let's think and answer, what else have we not studied and would like to know about it?
Problem: The relief was formed throughout the entire geological stage (3.5 billion years), but its development continues at the present time.
Problem question:
Why is the surface of the earth constantly changing?
Open the textbook page 49 and find the answer to this question:
What are the modern relief-forming processes?
3. Studying new material
Look at the desk ( terms written on the board): endogenous processes, exogenous processes, volcanism, earthquake, glaciation, moraines, eolian relief, talus, landslides, avalanches, mudflows, erosion - we will consider the terms in the lesson today, and remember some.
The relief is constantly changing under the influence of exogenous and endogenous factors. Both factors operate simultaneously.
Draw a diagram on the board:
Endogenous Exogenous processes
They appear both in the mountains and on platforms and flow under the influence of flowing waters, permafrost and wind.
Glacial landforms:
Morena is a geological body composed of glacial deposits. The boulders in the moraines consist mainly of granites and gneisses. It is an unsorted mixture of clastic material of various sizes.
The terminal moraine ridges are the boundary of the movement of the glacier, it represents the brought clastic material.
Sheep foreheads - a ledge of igneous and metamorphic rocks with scratches and scars on the surface; the slopes are facing towards the movement of the glacier, - gentle, opposite - steep.
Oz. (ridge, ridge) is a ridge with rather large slopes (30-45 0), resembling a road embankment. They are usually composed of sand, often with pebbles and gravel. The height can reach several tens of meters. Pine trees grow on the surface. Feature: they do not take into account the relief at all: the esker ridge can stretch along the watershed, then go down the slope, go into the lake, forming a long peninsula, dive and emerge again on the other side.
Kam. - this is a hill that makes up the material sorted, layered.
Zander - surfaces on which sands are common, brought by melted glacial waters.
Lakes in glacial basins - (exaration process) basins are formed as a result of tectonic troughs as a result of glacier movement.
Kars (mountain cirques) - glaciation in the mountains: Kars - bowl-shaped niches with slopes, steep upper parts and more gentle ones higher. Formed under the action of frosty weathering, they serve as a place for the accumulation of snow and the formation of glaciers.
Aeolian landforms:
Dunes are a kind of dunes, relief mobile formations of sand in deserts, blown by the wind and not fixed by plant roots. They reach a height of 0.5-100 m. They resemble a horseshoe or sickle in shape. Being not fixed, they can move at a speed of several cm to sonnets of meters per year.
Thermal landforms:
Frost heaving - typical for areas of the cold belt. Small hillocks can occur directly due to an increase in the volume of freezing water in the soil.
Stone rings and polygons - are formed in loose rocks, heterogeneous in composition, containing inclusions of stone fragments (crushed stone, pebbles ...). As a result of repeated freezing and thawing, large clastic material is pushed out of the rock to the surface and moves towards the fracture zones.
Solifluction is a slow flow along the slopes of loose, highly waterlogged dispersed deposits.
Kurums are mobile stone placers in the mountains and plateaus.
Thermokarst is the process of thawing of underground ice, accompanied by subsidence of the earth's surface, the formation of depressions and shallow karst lakes.
4. Practical work No. 2.
Target: reveal the relationship between the relief and tectonic structures on the territory of Russia.
5. Physical minute.
(The teacher reads a poem, the students do physical exercises)
Close your eyes, relax your body
Imagine - you are birds, you suddenly flew!
Now you swim like a dolphin in the ocean,
Now in the garden you pick ripe apples.
Left, right, looked around
Open your eyes and get back to work!
Individual work on instructive maps. (Atlas "Physical map of Russia" p. 14-15, "Tectonic map" p. 16.)
Conclusion on work(Children formulate)
1. The predominance of the flat terrain in Russia is associated with tectonic structure.
2. Large plains in the tectonic structure correspond to platforms.
3. In the relief, folded areas correspond to the mountains and plains.
4. The Caucasus Mountains formed in the areas of new folding. They are in height high mountains.
5. In the areas of ancient folding are located medium and low mountains in height.
6. The diversity of the relief of Russia is associated with the structure earth's crust.
(Discussion of the results of independent work, evaluation by criteria)
6. Fixing:
Application on k.k. landforms formed under the influence of external factors. (East European Plain, Caspian Lowland, Central Russian Upland,
Volga Upland, West Siberian Plain, Central Siberian Plateau, Caucasus Mountains, Ural, Altai, Western
and Eastern Sayan Mountains, Stanovoy Ridge, Verkhoyansk Ridge, Chersky Ridge).
7. Reflection.
Take one of the butterflies on your tables that matches your mood at the end of the lesson, think about whether you succeeded in this lesson, do you agree with your assessment, did you like the lesson? And attach to our impromptu clearing with daisies.
Red - I did it and I liked the lesson.
Yellow - I liked the lesson, but I made mistakes.
Blue - it was difficult and boring for me at the lesson.
8. Homework.
Guys, next lesson we will have a general review of the topics covered, so I suggest reviewing the material, and do not forget to bring contour maps to the next lesson.
Great day!
The lesson has come to an end.
Let everyone say to himself:
What a fine fellow I am!
And I thank you very much for the lesson!
9. Grading students.
Development of landforms
Russia
Forces shaping and changing the relief of Russia
Endogenous (internal)
Exogenous (external)
The latest tectonic
movements
- Weathering;
- Ancient glaciations;
- Sea activity;
- Activity of flowing waters (erosion);
- wind activity;
- Processes caused by the action of gravity;
- human activities
Volcanism
earthquakes
The relief is constantly changing under the influence of external (exogenous) and domestic (endogenous) processes
Recent tectonic movements
Horizontal
Slow vertical
Folded
discontinuous
Almost the entire area
Russia is experiencing
uplift.
Lowered central
areas West Siberian
plains, Caspian,
North Siberian,
Yano-Indigirskaya and
Kolyma lowland
In the districts
Cenozoic
folding
formed
folded
(Caucasus)
In the regions
folding
formed
faults and
(Altai, Sayans,
Ural, etc.)
Evidence of current ongoing tectonic movements are EARTHQUAKE
Volcanism
cones of volcanoes
Laccoliths
lava plateaus
Active volcanoes in Russia are only in Kamchatka and the Kuriles
Ancient glaciations
There were 4 epochs of glaciation in the Quaternary period: Valdai, Moscow, Dnieper, Okskoe.
The centers of glaciation were Scandinavian mountains, Polar Urals, Putorana plateau, Byrranga mountains (Taimyr)
Glacial landforms
- when the glacier melted, the water carried sand, from which water-glacial plains were formed on the outskirts of the glacier, they were called "outland".
- when the glacier moved to the south, under its weight, the earth's surface was plowed, the rocks were chafed and destroyed, and when the glacier melted, the recesses were filled with glacial melt water and thousands of lakes were formed in Karelia and the Kola Peninsula. The largest of them are Ladoga and Onega.
Ladoga lake
"lamb foreheads"
circuses and trogs
Physical
Destruction g rock under the influence of temperature difference
WEATHERING
biological
weathering, the destruction and alteration of rocks under the action of plants and living organisms, enhances the action of its other types.
Chemical
Rocks are destroyed under the influence of chemical processes - dissolution, leaching
Rocks are remnants. Ural
Mountain Altai. Ukkurum tract. Stone mushrooms in the gorge
river valley
Activity of flowing waters
Ravine-beam relief
fluvial relief
accumulative
erosional
scour
Ravine-beam relief
scour
fluvial relief
(from lat. Fluvivs- river)
Delta of the Lena River
Shot from space
Surface flowing water is one of the most important factors in the transformation of the Earth's relief.
River erosion - destruction of the bottom and banks of the river by the water flow. The result is a change in the valley, the emergence of sandy islands and sandbars, mountain gorges and canyons.
Trusovskoye Gorge. Caucasus
Valley of Spirits. Altai
Island formation
Sea activity
flat low seaside
plains created by
advancing seas
in the postglacial period
sand bars
Caspian lowland
Pechora lowland
Aeolian relief - wind activity
dunes
spring up in the desert
Dunes
formed along the coast
rivers and seas
curonian spit
Processes caused by the action of a force
gravity
collapses and
talus
landslides
sat down
Anthropogenic landforms
Dumps
Waste heaps
career
embankments
foundation pits
dumps
embankments
foundation pits
waste heaps
CAREERS
Mir kimberlite pipe Yakutia
Thanks
However, changes in landforms are actively taking place today. The relief-forming factors that are characteristic of the territory of Russia today can be divided into two groups: exogenous (wind and water activity) and endogenous (movements in the lithosphere).
Modern relief-forming processes can be divided into two groups: internal (endogenous), caused by movements of the earth's crust (they are called neotectonic or recent), and external (exogenous).
Development of landforms in Russia
The development of landforms in Russia dates back to the Quaternary period, when, due to climate change, many territories of our planet were covered with glaciers. So the modern Ural Mountains, the Taimyr Peninsula and the Central Siberian Plateau became the centers of glaciation.
Over time, the glaciers began to move south, moving sand, gravel and clay with them. The high temperatures of the southern territories contributed to the rapid melting of ice, which led to the settling of loose rocks on the soil and the formation of a moraine relief.
This type of relief prevails in the Moscow and Smolensk regions. The next climatic changes on the planet caused the melting of the northern glaciers.
Glacial waters filled depressions in crystalline rocks, thus creating lakes in the northern part of the Russian Plain.
Human activities and landform formation
In the course of the development of industry, irreparable changes in the relief of Russia take place. The types of human activities that affect the relief include: mining, construction of highways and railways, movement of soil for agricultural purposes.
Very often, people's intervention in the relief structure causes such negative consequences as the appearance of natural disasters.
The influence of wind on the development of relief
In the regions of the Russian Federation, which are characterized by a large amount of precipitation, the formation of the relief is influenced by the wind.
In particular, the special influence of wind on the formation of relief is typical for such territories as the Caspian lowland and the coast of the Baltic Sea (Kaliningrad region).
Natural phenomena
Natural natural phenomena are phenomena that occur in the balls of the lithosphere. Landslides, earthquakes, avalanches, volcanic eruptions are among the natural disasters.
The most typical for Russia is an earthquake. So in 1995, the Sakhalin Peninsula suffered from a strong earthquake. The strongest internal tremors led to the destruction of several settlements.
For mountainous areas, in particular the region of the Ural and Altai mountains, landslides and landslides are characteristic. Due to the fact that these mountain systems belong to the old mountains, the masses of snow that melt in the spring carry rock fragments with them, which is dangerous for the locals.
Until now, we have considered internal relief-forming factors, such as movements of the earth's crust, folding, etc. These processes are due to the action of the internal energy of the Earth. As a result, large landforms such as mountains and plains are created. In the lesson, you will learn how the relief was formed and continues to form under the influence of external geological processes.
Other forces are also working on the destruction of rocks - chemical. Seeping through cracks, water gradually dissolves rocks (See Fig. 3).
Rice. 3. Dissolution of rocks
The dissolving power of water increases with the content of various gases in it. Some rocks (granite, sandstone) do not dissolve in water, others (limestone, gypsum) dissolve very intensively. If water penetrates along cracks into layers of soluble rocks, then these cracks expand. In those places where water-soluble rocks are close to the surface, numerous sinkholes, funnels and depressions are observed on it. This is karst landforms(see Fig. 4).
Rice. 4. Karst landforms
Karst is the process of dissolution of rocks.
Karst landforms are developed on the East European Plain, Cis-Urals, the Urals and the Caucasus.
Rocks can also be destroyed as a result of the vital activity of living organisms (saxifrage plants, etc.). This is biological weathering.
Simultaneously with the destruction processes, the destruction products are transferred to lower areas, thus, the relief is smoothed out.
Consider how the Quaternary glaciation shaped the modern relief of our country. Glaciers have survived to this day only on the Arctic islands and on the highest peaks of Russia. (See Fig. 5).
Rice. 5. Glaciers in the Caucasus Mountains ()
Going down steep slopes, glaciers form a special, glacial relief. Such a relief is common in Russia and where there are no modern glaciers - in the northern parts of the East European and West Siberian plains. This is the result of an ancient glaciation that arose in the Quaternary era due to a cooling of the climate. (See Fig. 6).
Rice. 6. Territory of ancient glaciers
The largest centers of glaciation at that time were the Scandinavian mountains, the Polar Urals, the islands of Novaya Zemlya, the mountains of the Taimyr Peninsula. The thickness of the ice on the Scandinavian and Kola peninsulas reached 3 kilometers.
Glaciation occurred more than once. It was advancing on the territory of our plains in several waves. Scientists believe that there were about 3-4 glaciations, which were replaced by interglacial epochs. The last ice age ended about 10,000 years ago. The most significant was the glaciation on the East European Plain, where the southern edge of the glacier reached 48º-50º N. sh.
To the south, the amount of precipitation decreased, therefore, in Western Siberia, glaciation reached only 60º N. sh., and east of the Yenisei, due to the small amount of snow, it was even less.
In the centers of glaciation, from where the ancient glaciers moved, there are widespread traces of activity in the form of special relief forms - Sheep foreheads. These are ledges of rocks with scratches and scars on the surface (slopes facing towards the movement of the glacier are gentle, and the opposite ones are steep) (See Fig. 7).
Rice. 7. Lamb forehead
Under the influence of their own weight, glaciers spread far from the center of their formation. Along the way, they smoothed out the relief. A characteristic glacial relief is observed in Russia on the territory of the Kola Peninsula, the Timan Ridge, the Republic of Karelia. The moving glacier scraped soft loose rocks and even large, hard debris from the surface. Clay and hard rocks frozen into the ice formed moraine(deposits of rock fragments formed by glaciers during their movement and melting). These rocks were deposited in more southerly regions where the glacier was melting. As a result, moraine hills and even entire moraine plains were formed - Valdai, Smolensk-Moscow.
Rice. 8. Moraine formation
When the climate did not change for a long time, the glacier stopped in place and single moraines accumulated along its edge. In the relief, they are represented by curved rows tens or sometimes even hundreds of kilometers long, for example, Northern Uvaly on the East European Plain (see fig. 8).
During the melting of glaciers, streams of melt water were formed, which washed over the moraine, therefore, in the areas of distribution of glacial hills and ridges, and especially along the edge of the glacier, water-glacial sediments accumulated. Sandy flat plains that arose along the outskirts of a melting glacier are called - outwash(from German "zander" - sand). Examples of outwash plains are the Meshcherskaya lowland, the Upper Volga, Vyatka-Kama lowland (see fig. 9).
Rice. 9. Formation of outwash plains
Among the flat-low hills, water-glacial landforms are widespread, ozes(from Swedish "oz" - ridge). These are narrow ridges, up to 30 meters high and up to several tens of kilometers long, resembling railway embankments in shape. They were formed as a result of settling on the surface of loose sediments formed by rivers flowing along the surface of glaciers. (see fig. 10).
Rice. 10. Formation of lakes
All water flowing on land, under the influence of gravity, also forms a relief. Permanent streams - rivers - form river valleys. The formation of ravines is associated with temporary streams formed after heavy rains. (see fig. 11).
Rice. 11. Ravine
Overgrown, the ravine turns into a beam. The slopes of uplands (Central Russian, Volga, etc.) have the most developed ravine network. Well-developed river valleys are characteristic of rivers flowing outside the boundaries of the last glaciations. Flowing waters not only destroy rocks, but also accumulate river sediments - pebbles, gravel, sand and silt (see fig. 12).
Rice. 12. Accumulation of river sediment
They consist of river floodplains, stretching in strips along the riverbeds. (see fig. 13).
Rice. 13. The structure of the river valley
Sometimes the latitude of the floodplains varies from 1.5 to 60 km (for example, near the Volga) and depends on the size of the rivers (see Fig. 14).
Rice. 14. The width of the Volga in various sections
Along the river valleys there are traditional places of human settlement and a special type of economic activity is being formed - animal husbandry in floodplain meadows.
On the lowlands, experiencing slow tectonic subsidence, there are extensive floods of rivers and wanderings of their channels. As a result, plains are formed, built by river sediments. This relief is most common in the south of Western Siberia. (see fig. 15).
Rice. 15. Western Siberia
There are two types of erosion - lateral and bottom. Deep erosion is aimed at cutting flows into the depth and prevails near mountain rivers and rivers of plateaus, which is why deep river valleys with steep slopes are formed here. Lateral erosion is aimed at erosion of the banks and is typical for lowland rivers. Speaking about the impact of water on the relief, we can also consider the impact of the sea. When the seas advance on the flooded land, sedimentary rocks accumulate in horizontal layers. The surface of the plains, from which the sea retreated long ago, is greatly changed by flowing waters, wind, glaciers (see fig. 16).
Rice. 16. Retreat of the sea
The plains, relatively recently abandoned by the sea, have a relatively flat relief. In Russia, this is the Caspian lowland, as well as many flat areas along the shores of the Arctic Ocean, part of the low plains of Ciscaucasia.
The activity of the wind also creates certain landforms, which are called eolian. Aeolian landforms are formed in open spaces. In such conditions, the wind carries a large amount of sand and dust. Often a small bush is a sufficient barrier, the wind speed decreases, and the sand falls to the ground. Thus, at first small, and then large sandy hills are formed - dunes and dunes. In terms of plan, the dune has the shape of a crescent, with its convex side facing the wind. As the direction of the wind changes, so does the orientation of the dune. Wind-related landforms are distributed mainly on the Caspian lowland (dunes), on the Baltic coast (dunes) (see fig. 17).
Rice. 17. Formation of a dune
The wind blows a lot of small fragments and sand from the bare mountain peaks. Many of the grains of sand he carries out again hit the rocks and contribute to their destruction. You can observe bizarre weathering figures - remnants(see fig. 18).
Rice. 18. Remains - bizarre landforms
The formation of special species - forests - is associated with the activity of the wind. - loose, porous, dusty rock (see fig. 19).
Rice. 19. Forest
Forest covers large areas in the southern parts of the East European and West Siberian plains, as well as in the Lena River basin, where there were no ancient glaciers (see fig. 20).
Rice. 20. Russian territories covered with forest (shown in yellow)
It is believed that the formation of the forest is associated with dust and strong winds. The most fertile soils are formed on the forest, but it is easily washed away by water and the deepest ravines appear in it.
- The formation of the relief occurs under the influence of both external and internal forces.
- Internal forces create large landforms, and external forces destroy them, transforming them into smaller ones.
- Under the influence of external forces, both destructive and creative work is carried out.
Bibliography
- Geography of Russia. Nature. Population. 1 hour Grade 8 / V.P. Dronov, I.I. Barinova, V.Ya Rom, A.A. Lobzhanidze.
- V.B. Pyatunin, E.A. Customs. Geography of Russia. Nature. Population. 8th grade.
- Atlas. Geography of Russia. population and economy. - M.: Bustard, 2012.
- V.P. Dronov, L.E. Savelyeva. UMK (educational-methodical set) "SPHERES". Textbook “Russia: nature, population, economy. 8th grade". Atlas.
- The influence of internal and external processes on the formation of relief ().
- External forces that change the relief. Weathering. ().
- weathering().
- Glaciation in Russia ().
- Physics of dunes, or how sand waves are formed ().
Homework
- Is the statement true: “Weathering is the process of destruction of rocks under the influence of wind”?
- Under the influence of what forces (external or internal) did the peaks of the Caucasus Mountains and Altai acquire a pointed shape?
Description of the presentation on individual slides:
1 slide
Description of the slide:
2 slide
Description of the slide:
* Repetition of home material. Questions to the class: 1. What minerals are rich in our country? 2. Name the patterns in the distribution of minerals 3. Using the example of the Tomsk region, show what dependence the distribution of minerals has on the landforms and structure of the territory. 4. Remember what minerals are associated with igneous, sedimentary rocks?
3 slide
Description of the slide:
* Patterns in the distribution of minerals The mountainous areas are confined to: igneous minerals The flat areas are confined to: Sedimentary minerals
4 slide
Description of the slide:
* Minerals of Igneous origin: Granite, Basalt Iron ore, Copper ore, Gold, diamonds Sedimentary origin: Coal, Oil, Natural gas, Phosphorites, Salt
5 slide
Description of the slide:
* Learning new material. Give examples of changes in landforms at the present time - for the Tomsk region; For other areas of our country; For other continents
6 slide
Description of the slide:
* Relief The surface of the Earth is constantly changing. And this is influenced by two types of processes: endogenous (internal), exogenous (external) Internal; External
7 slide
Description of the slide:
* Endogenous (internal processes) Quaternary events: Recent tectonic movements Earthquakes Volcanism
8 slide
Description of the slide:
* Recent tectonic movements Almost the entire territory of Russia experienced uplift in the Neogene-Quaternary. But the northern edge of the Asian part sank and was flooded by the waters of the seas of the Arctic Ocean. The central regions of the West Siberian Plain and the Caspian lowland also sank.
9 slide
Description of the slide:
* Earthquakes Earthquakes are evidence of ongoing tectonic movements. The most frequent and strong earthquakes occur in Kamchatka, the Kuril Islands, in the mountains of the Baikal region, the Greater Caucasus, the southeastern part of Altai, Tyva and the lower reaches of the Lena.
10 slide
Description of the slide:
* Volcanism There are active volcanoes in our country only in Kamchatka and the Kuril Islands. There are about 60 active and three times more extinct volcanoes. Traces of recent volcanism are also found in the Caucasus (Elbrus, Kazbek), and in the Eastern Sayan, in Transbaikalia, in the Far East. The most beautiful and highest volcano in Kamchatka is Klyuchevskaya Sopka. (top photo) Gorely volcano (bottom photo)
11 slide
Description of the slide:
* Exogenous (external processes) Ancient glaciations, Activity of the sea, Activity of flowing waters.
12 slide
Description of the slide:
* Ancient glaciations The general uplift of the land, the change in the outlines of the Eurasian continent and the cooling of the climate on the globe led to the emergence of a sheet glaciation in the Quaternary. In total there were 3-4 epochs of glaciation. Centers: Scandinavia, Polar Urals, Putorana Plateau, Byrranga Mountains on the Taimyr Peninsula
13 slide
Description of the slide:
* Glacial Landforms The glacier moved to the south, changing the Earth's relief, moving stones (boulders), sand, crushed stone, clay frozen into it. brought loose material (boulders, crushed stone, gravel) hills - moraines. In the north, under the weight of the glacier, the northern tip of Eurasia was forced through and became the bottom of the seas of the Arctic Ocean. The glacier also deepened tectonic troughs, forming thousands of lakes in Karelia and the Kola Peninsula.
14 slide
Description of the slide:
* Glacial lakes Lake Ladoga is the largest freshwater lake in Europe. Refers to the Baltic Sea basin of the Atlantic Ocean. The area of the lake without islands is from 17.6 thousand km² (with islands 18.1 thousand km²); the volume of water mass - 908 km³; length from south to north - 219 km, maximum width - 138 km. The depth varies unevenly: in the northern part it ranges from 70 to 230 m, in the southern part - from 20 to 70 m)
