CLASS- VI CH- 6 GEOGRAPHY MAJOR LANDFORMS OF THE EARTH

      MAJOR LANDFORMS OF THE EARTH

                    CLASS VI CHAPTER 6

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·                     The ground we are standing on is slowly moving. Within the earth, a continuous movement is taking place. The first, or the internal process leads to the upliftment and sinking of the earth’s surface at several places.

·                     The second, or the external process is the continuous wearing down and rebuilding of the land surface.

·                     The wearing away of the earth’s surface is called erosion. The surface is being lowered by the process of erosion and rebuilt by the process of deposition.

·                     These two processes are carried out by running water, ice and wind. Broadly, we can group different landforms depending on elevation and slope as mountains, plateaus and plains.

MOUNTAINS

·                     A mountain is any natural elevation of the                                                                              earth surface.

·                     It is considerably higher than the surrounding area. Some mountains are even higher

              than the clouds. As we go higher, the climate becomes colder.

·                     In some mountains, there are permanently frozen rivers of ice which are called glaciers.

·                     Less people live in the mountain areas because slopes are steep, less land is available for                     farming.

·                     When mountains are arranged in a line are called range.

·        There are three types of mountains- Fold Mountains, Block Mountains and the Volcanic                       Mountains.

Fold Mountains

(i)The Himalayan Mountains and the Alps are young fold mountains with rugged relief and high conical peaks.

(ii)The Aravali range in India is one of the oldest fold mountain systems in the world.

(iii) The Appalachians in North America and theUral mountains in Russia are very old  foldmountains.

Block Mountains

(i)  Block Mountains are created when large areas are broken and displaced vertically.

(ii)  The uplifted blocks are termed as horsts and the lowered blocks are called

graben.

(iii)  The Rhine valley and the Vosges mountain in Europe are examples of such mountain systems.

Volcanic mountains

(i)                  Volcanic mountains are formed due to volcanic activity.

(ii)                Mt.Kilimanjaro in Africa and Mt.Fujiyama in Japan are examples of such mountains.

(iii)               The mountains are a storehouse of water. Many rivers have their source in the glaciers in                     the mountains.

(iv)        Water from the mountains is also used for irrigation and generation of hydro-electricity.(v)         The river valleys and terraces are ideal for cultivation of crops. Mountains have a rich variety              of flora and fauna.

PLATEAUS

• ·              A plateau is an elevated flat land. It is a flat-toppedtable land standing above the surrounding area.
•       The height of plateaus often varies from few hundred  metres to several thousand metres.
•         The Deccan plateau in India is one of the oldest plateaus.
•         The Tibet plateau is the highest plateau in the world with a height of 4,000 to 6,000 metres above the mean sea level.
•         As plateaus are rich in minerals many of the mining areas in the world are located in the plateau areas.
•       The African plateau is famous for gold and diamond mining.
•       In India huge reserves of iron, coal and manganese are found in the Chhotanagpur plateau.
•         There may be several waterfalls In the plateau areas.
•        Example-The Hundru falls in the Chhotanagpur plateau on  the river Subarnarekha and the Jog falls in Karnataka.

PLAINS

(i)Plains are large stretches of flat land.They are, generally, not more than 200 metres above mean sea level.

(ii)Most of the plains are formed by rivers and their tributaries. The rivers flow down the slopes of mountains and erode them. They carry forward the eroded material. Then they deposit their load consisting of stones, sand and silt along their courses and in their valleys.

(iii)plains are fertile and good for construction and transportation. So these areas are very much populated.

(iv)Example-these plains are formed by the Ganga and the Brahmaputra in India and

the Yangtze in China.ghj

CLASS- VI GEO. CHAPTER-5

CLASS- VI  GEO. CHAPTER-5

MAJOR DOMAINS OF THE EARTH

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     The earth is the only planet which has life. Human beings can live here because the  life sustaining elements of land, water and air are present on the earth.

·         Earth has three main components they are:-lithosphere,Atmosphere,Hydrosphere

·         Lithosphere:- i.The solid portion of the earth on which we live is called the Lithosphere.

ii. It comprises the rocks of the earth’s crust and the thin layers of soil that contain nutrient elements which sustain organisms.

·         Atmosphere:- The gaseous layers that surround the earth, is the Atmosphere, where oxygen, nitrogen, carbondioxide and other gases are found.

                   

·         Hydrosphere:-

     i.Water covers a very big area of the earth’s surface and this area is called the Hydrosphere.

    ii. More than 71 per cent of the earth is covered with water and 29 per cent is with land.So earth is called ‘blue planet’.

   iii. Hydrosphere consists of water in all its forms. As running water in oceans and rivers and in lakes, ice in glaciers, underground water and the water vapour in atmosphere,                                               .        all comprise the hydrosphere.

 iv. More than 97% of the Earth’s water is found in the oceans and is too salty for human use. A large proportion of the rest of the water is in the form of icesheets and glaciers                                        .       or under the ground and a very small percentage is available as fresh water for human use. Hence, despite being a ‘blue planet’ we face a shortage of water!!

   Biosphere :-The Biosphere is the narrow zone where we find land, water and air together, which contains all forms of life.

·           There are two main divisions of the earth’s surface. The large landmasses are known as the continents and the huge water bodies are called the ocean basins.

·         i.The level of seawater remains the same everywhere. Elevation of land is measured from the level of the sea,which is taken as zero.

·         ii. The highest mountain peak Mt. Everest is 8,848 metres above the sea level. The greatest depth of 11,022 metres is recorded at Mariana Trench in the Pacific Ocean.

Continents

·         There are seven major continents. These are separated by large water bodies. These continents are – Asia, Europe, Africa, North America, South America, Australia and Antarctica.

·         Asia

i.Asia is the largest continent. It covers about onethird of the total land area of the earth.

ii.The continent lies in the Eastern Hemisphere.

iii.The Tropic of Cancer passes through this continent. Asia is separated from Europe by the Ural mountains on the west.The combined landmass of  Europe and Asia is called the Eurasia (Europe + Asia).

·         Europe

i.Europe is much smaller than Asia. The continent lies to the west of Asia.

ii. The Arctic Circle passes through

it. It is bound by water bodies on three sides.

·         Africa

i.Africa is the second largest continent after Asia. The Equator or 0⁰ latitude runs almost through the middle of the continent. A large part of Africa lies in the Northern Hemisphere.

ii. it is the only continent through which the Tropic of Cancer, the Equator and the Tropic of Capricorn pass.

iii. The Sahara Desert, the world’s largest hot desert, is located in Africa. The continent is bound on all sides by oceans and seas.

iv. the world’s longest river the Nile, flows through Africa.

·         North America

i.North America is the third largest continent of the world.

ii.It is linked to South America by a very narrow strip of land called the Isthmus of Panama.

iii.The continent lies completely in the Northern and Western Hemisphere. Three oceans surround this continent.

·         South America

i.South America lies mostly in the Southern Hemisphere.

ii. The Andes, world’s longest mountain range, runs through its length from north to south.

iii.South America has the world’s largest river, the Amazon.

·         Australia

i.Australia is the smallest continent that lies entirely in the Southern Hemisphere.

ii.It is surrounded on all sides by the oceans and seas. It is called an island continent.

·         Antarctica

i. Antarctica, completely in the Southern Hemisphere, is a huge continent.

ii.The South Pole lies almost at the centre of this continent. As it is located in the South

Polar Region, it is permanently covered with thick ice sheets.

iii.There are no permanent human settlements. Many countries have research stations in Antarctica. India also has research stations there. These are named as Maitri and Dakshin Gangotri.

Oceans

i.Oceans are the major part of hydrosphere. They are all interconnected.

ii.The ocean waters are always moving. The three chief movements of ocean waters are the waves, the tides and the ocean currents.

iii. The five major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean and the Arctic Ocean.

Pacific Ocean

i.The Pacific Ocean is the largest ocean. It is spread over one-third of the earth.

ii.Mariana Trench, the deepest part of the earth, lies in the Pacific Ocean.

 iii.The Pacific Ocean is almost circular in shape. Asia, Australia, North and South Americas surround it.

The Atlantic Ocean

i.The Atlantic Ocean is the second largest Ocean in the world. It is ‘S’ shaped. It is flanked by the North and South Americas on the western side, and Europe and Africa on the eastern side. ii.The coastline of Atlantic Ocean is highly indented. This irregular and indented coastline provides ideal location for natural harbours and ports. From the point of view of commerce, it is the busiest Ocean.

The Indian Ocean

i.The Indian Ocean is the only ocean named after a country, that is, India.

 ii.The shape of ocean is almost triangular. In the north, it is bound by Asia, in the west by Africa and in the east by Australia.

The Southern Ocean

i.The Southern Ocean encircles the continent of Antarctica and extends northward to 60 degrees south latitude.

The Arctic Ocean

The Arctic Ocean is located within the Arctic Circle and surrounds the North Pole. It is connected with the Pacific Ocean by a narrow stretch of shallow water known as Berring strait. It is bound by northern coasts of North America and Eurasia.

 ATMOSPHERE

i.The earth is surrounded by a layer of gas called the atmosphere. This thin blanket of air is an integral and important aspect of the planet. It provides us with the air we breathe and protects us from the harmful effects of sun’s rays.

ii. The atmosphere extends up to a height of about 1,600 kilometres which is further divided into five layers based on composition, temperature and other properties such as:- troposphere, the stratosphere, the mesosphere, the thermosphere and the exosphere.

iii. The atmosphere is composed mainly of Nitrogen 78 per cent, oxygen 21 per cent and

other gases like carbondioxide, argon and others comprise 1 per cent by volume.

iv. Oxygen is the breath of life while nitrogen helps in the growth of living organisms. Carbon dioxide, though present in minute amount, is important as it absorbs heat radiated by the earth, thereby keeping the planet warm.

·         The density of the atmosphere varies with height. It is maximum at the sea level and decreases rapidly as we go up. You know, the climbers experience problems in breathing due to this decrease in the density of air. They have to carry with them oxygen cylinders to be able to breathe at high altitudes.

·         Air moves from high pressure to low pressure. Moving air is known as wind.

BIOSPHERE – THE DOMAIN OF LIFE

i.The biosphere is the narrow zone of contact between the land, water and air. It is in this zone that life.

ii. All the living organisms including humans are linked to each other and to the biosphere for survival.

·         Discharge of waste material into lakes and rivers makes the water unsuitable for human use. It also damages other forms of life.

·         Emission from industries, thermal power plants and vehicles, pollute the air. Carbon dioxide (CO2) is an important constituent of air. But increase in the amount of CO2 leads to increase in global temperatures.This is termed as global warming.

·         ISTHMUS

A narrow strip of land joining two landmasses.

STRAIT

A strait is a narrow passage of water connecting two large waterbodies like seas and ocean.

                                               CLASS VI  GEO. CH-4

MAPS

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Ø  What is map?

Ans-A map is a representation or a drawing of the earth’s surface or a part of it drawn on a flat surface according to a scale.

Ø  What is atlas?

Ans-When many maps are put together we get an Atlas. Atlases are of various sizes, measurements drawn on different scales.

Ø  What are the advantages of map as compared to globe?

Ans-i. A globe can be useful when we want to study the earth as a whole. But, when we want to study only a part of the earth, as about our country, states, districts, towns and villages, it is of little help. In such a situation we use maps.

ii. A map is a representation or a drawing of the earth’s surface or a part of it drawn on a flat surface according to a scale.

iii. When many maps are put together we get an Atlas.

iv. Maps provide more information than a globe.

Ø  What is physical maps?

Ans-Maps showing natural features of the earth such as mountains, plateaus, plains, rivers, oceans etc. are called physical or relief maps.

Ø  What is political maps?

Ans-Maps showing cities, towns and villages, and different countries and states of the world with their boundaries are called political maps.

Ø  What is Thematic maps?

Ans-i.Some maps focus on specific information; such as road maps, rainfall maps, maps showing distribution of forests, industries etc. are known as thematic maps.

ii. There are three Components of Maps – distance, direction and symbol.

Ø  What is scale of the map?

Ans-Scale is the ratio between the actual distance on the ground and the distance shown on the map.

Ø  What is small scale map?

Ans-When large areas like continents or countries are to be shown on a paper, then we use a small scale. For example 5 cm. on the map shows 500 km. of the ground. It is called a small scale map.

Ø  What is large scale map?

Ans-When a small area like your village or town is to be shown on paper, then we use a large scale that is 5 cm. on the map shows 500 metres only on the ground. It is called a large scale map.

Ø  What is cardinal points?

Ans-There are four major directions, North, South, East and West They are called cardinal points.

Ø  What is conventional symbols of map?

Ans-Maps have a universal language that can be understood by all.
There is an international agreement regarding the use of these symbols. These are called conventional symbols.

Ø  What is sketch?

Ø     Ans-A sketch is drawing mainly based on memory and spot observation and not to scale.Sketch is a rough drowing without drawing.

Ø  What is plan?

Ans-A plan is a drawing of a small area on a large scale.

Example-the length and breadth of a room, which can’t be shown in a map. At that time, we can refer drawings drawn to scale called a plan.

MOTIONS OF THE EARTH

CLASS VI GEO. CH-3

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·         Earth has two types of motions namely rotation and revolution.

·         Rotation-Rotation is the movement of earth on its axis.

·         Revolution-Revolution is the movement of the earth around the sun in a fixed  path or orbit.

·         Orbital plane-The axis of the earth which is an imaginary line, makes an angle of 66.5­° with its orbital plane. The plane formed by the orbit is known as the orbital plane.

·         Due to the spherical shape of the earth, only half of it gets light from the sun at a time. The portion facing the sun experiences day while the other half away from the sun experiences night.

·         circle of illumination-The circle that divides the day from night on the globe is called the circle of illumination . The earth takes about 24 hours to complete one rotation around its axis. The period of rotation is known as the earthday. This is the daily motion of the earth.

·         What would happen if the earth did not rotate?

·         Ans-The portion of the earth facing the sun would always experience day, thus bringing continuous warmth to the region. The other half would remain in darkness and be freezing cold all the time. Life would not have been possible in such extreme conditions.

·         The second motion of the earth around the sun in its orbit is called revolution. It takes 365­ days (one year) to revolve around the sun. We consider a year as consisting of 365 days only and ignore six hours for the sake of convenience.

              Six hours saved every year are added to make one day (24 hours) over a span of four years. This surplus day is added to the month of February. Thus every fourth year, February is of 29                                                             days instead of 28 days. Such a year with 366 days is called a                                                                 leap year.

•      the earth is going around the sun in an elliptical orbit.
• ·         Since a large portion of the Northern Hemisphere is getting light from the sun, it is summer in the regions north of the equator. The longest day and the shortest night at these places occur on 21 st June. At this time in the Southern Hemisphere all these conditions are reversed. It is winter season there. The nights are longer than the days. This position of the earth is called the Summer Solstice.
• ·         On 22 nd December, the Tropic of Capricorn receives direct rays of the sun as the South Pole tilts towards it. As the sun’s rays fall vertically at the Tropic of Capricorn (23.5­° S), a larger portion of the Southern Hemisphere gets light. Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights. The reverse happens in the Northern Hemisphere. This position of the earth is called the Winter Solstice.
• ·         On 21 st March and September 23rd, direct rays of the sun fall on the equator. At this position, neither of the poles is tilted towards the sun; so, the whole earth experiences equal days and equal nights. This is called an equinox.On 23rd September, it is autumn season in the Northern Hemisphere and spring season in the Southern Hemisphere. The opposite is the case on 21st March, when it is spring in the Northern Hemisphere and autumn in the Southern Hemisphere.