NCERT GEOGRAPHY : 6TH : THE EARTH : OUR HABITAT : REVISION NOTES

6th NCERT GEOGRAPHY : TABLE OF CONTENTS :

  1. The Earth in the Solar System

  2. Globe : Latitudes and Longitudes.

  3. Motions of the Earth

  4. Maps

  5. Major Domains of the Earth

  6. Major Landforms of the Earth

  7. Our Country – India

  8. India : Climate, Vegetation and Wildlife

CHAPTER 1 : THE EARTH IN THE SOLAR SYSTEM :

Page 1 :

  • The sun, the moon and all those objects shining in the night sky are called celestial bodies.

  • These celestial bodies have their own heat and light and emit it in large amounts – are called stars.

  • The sun is a star.

Page 2 :

  • Various patterns formed by different groups of stars are called constellations.

  • Ursa Major or Big Bear is one such constellation.

  • One of the most easily recognisable constellation is the small bear or Saptarishi (Sapta-seven, rishi-sages). It is a group of seven stars.

  • The North star indicates the north direction. It is also called the Pole Star. It always remains in the same position in the sky. We can locate the position of the Pole Star with the help of the Saptarishi.

  • Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called planets.

  • The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’.

  • The moon is a satellite. It is a companion of our earth and moves round it.

THE SOLAR SYSTEM : Page 2 :

The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.

  • ‘Sol’ in Roman mythology is the ‘Sungod’.

  • Those who study the celestial bodies and their movements are called astronomers.

  • Aryabhatta was a famous astronomer of ancient India.

Page 4 :

The sun :

  • It is at the centre of the solar system ; made of extremely hot gases.

  • Ultimate source of heat +light for solar system.

  • Sun provides the pulling force that binds the solar system.

  • The sun is about 150 million km away from the earth.

Planets :

  • There are eight planets in our solar system. In order of their distance from the sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

  • All the planets move around the sun in fixed elongated paths – called orbits.

  • Mercury is nearest to the sun. It takes only about 88 days to complete one round along its orbit.

  • Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.

  • Jupiter, Saturn and Uranus have rings around them. These are belts of small debris.

The Earth :

  • The earth is the third nearest planet to the sun. In size, it is the fifth largest planet. It is slightly flattened at the poles. That is why, its shape is described as a Geoid. Geoid means an earth-like shape.

  • From the outer space, the earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a blue planet.

  • Light travels at the speed of about 300,000 km per second. Yet, even with this speed, the light of the sun takes about eight minutes to reach the earth.

  • Neil Armstrong was the first man to step on the surface of the moon on 21 July 1969

The Moon : Page 5 :

  • Our earth has only one satellite, that is, the moon.

A Satellite is a celestial body that moves around the planets in the same way as the planets move around the sun.

  • Moon is about 3,84,400 km away from our earth.

  • The moon moves around the earth in about 27 days. It takes exactly the same time to complete one spin. As a result, only one side of the moon is visible to us on the earth.

  • The moon does not have conditions favourable for life. It has neither water nor air. It has mountains, plains and depressions on its surface. These cast shadows on the moon’s surface.

Page 6 :

  • Asteroids are tiny bodies which move around the sun and they are found between the orbits of Mars and Jupiter.

  • The small pieces of rocks which move around the sun are called meteoroids.

  • A galaxy is a huge system of billions of stars, and clouds of dust and gases. There are millions of such galaxies that make the Universe.

  • Our solar system is a part of milky galaxy.

Chapter - 2 Globe : Latitudes and Longitudes

Page 10 :

  • Earth is not a sphere. It is slightly flattened at the North and the South Poles and bulge in the middle. It rotates from West to East.

  • Globe is a true model (miniature form) of the earth.

  • The imaginary line running on the globe divides it into two equal parts. This line is known as the equator. The northern half of the earth is known as the Northern Hemisphere and the southern half is known as the Southern Hemisphere. They are both equal halfs.

  • All parallel circles from the equator up to the poles are called parallels of latitudes. Latitudes are measured in degrees.

  • The equator represents the zero degree latitude.

  • 90 degrees north latitude marks the North Pole and 90 degrees south latitude marks the South Pole.

Since the distance from the equator to either of the poles is one­fourth of a circle round the earth, it will measure 90 degrees.

Important Parallels of Latitudes : Page 11 :

Besides the equator (0°), the North Pole (90°N) and the South Pole (90° S), there are four important parallels of latitudes– They are : (i) Tropic of Cancer (23 ½ ° N) in the Northern Hemisphere. (ii) Tropic ofCapricorn (23 ½ ° S) in the Southern Hemisphere. (iii) Arctic Circle at 66 ½ °north of the equator. (iv) Antarctic Circle at 66 ½ ° south of the equator

Heat Zones of the Earth :Page 12 :

  • Area between the Tropic of Cancer and the Tropic of Capricorn - Torrid Zone : Sun overhead at least once a year on all latitudes.

  • Areas bounded by the Tropic of Cancer + the Arctic Circle and the Tropic of Capricorn and the Antarctic Circle = have moderate temperatures - Temperate Zones - as mid­day sun never shines overhead on any latitude =

  • Areas lying between the Arctic Circle + the North Pole and the Antarctic Circle + the South Pole = Frigid Zones (very cold) as the sun does not rise much above the horizon. Therefore, its rays are always slanting and provide less heat.

WHAT ARE LONGITUDES? Page 12

  • The lines of references running from the north pole to the south pole are called the meridians of longitudes.

  • All these meridians meet at the poles.

  • The meridians which passed through Greenwich where the British Royal Observatory is located is called the Prime meridian. Its value is zero degree longitude.

Longitude and Time : Page 15 :

  • The best means of measuring time is by the movement of the earth, the moon and the planets.

  • When the Prime Meridian of Greenwich has the sun at the highest point in the sky, all the places along this meridian will have mid­day or noon.

  • As the earth rotates from west to east, those places east of Greenwich will be ahead of Greenwich time and those to the west will be behind it.

Why do we have Standard Time ? Page 15 :

  • The local time of places which are on different meridians are bound to differ. For example, it will be difficult to prepare a time­table for trains which cross several longitudes.

  • In India, the longitude of 82 ½ ° E (82° 30' E) is treated as the standard meridian. The local time at this meridian is taken as the standard time for the whole country. It is known as the Indian Standard Time (IST)

  • The Earth has been divided into 24 time zones of 1hour each.

Chapter 3 : Motions of the Earth

Page 18 :

The earth has two types of motions, namely rotation and revolution.

  • Rotation is the movement of the earth on its axis. The earth takes about 24 hours to complete one rotation around its axis.The period of rotation of earth is known as the Earth day. The portion facing the sun experiences day while the other half away from the sun experiences night.

  • The movement of the earth around the sun in a fixed path or orbit is called Revolution. Earth goes in an elliptical orbit around the sun + takes 365 days 6 hours to revolve around the sun

Page 20 :

  • On 21 june, the Northern Hemisphere is tilted towards the sun. The rays of the sun fall directly on the tropic of cancer. The longest day and the shortest night at these places occur on 21st 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 Summer Solstice.

  • On 22 December the tropic of capricorn receives direct rays of the sun. A larger portion of the Southern Hemisphere gets light. Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights + Reverse in Northern Hemisphere.This is called Winter Solstice.

  • On 21st March and 23rd September direct rays of the sun fall on the equator. This is known as Equinox.

  • On 23rd September it is autumn season in the Northern Hemisphere and spring seaso.n in the southern hemisphere.

  • Chapter 4 : Maps – Ignore

Chapter 5 : Major Domains of the Earth:

Page 30 :

The Earth is the only planet which has life i.e. it has the life sustaining elements of land, water and air. The Biosphere is the narrow zone where we find land, water, and air together which contains all forms of life.

  • The solid portion of the earth on which we live is called Lithosphere.

  • The gaseous layers that surround the earth is the atmosphere

  • Water covers a big area on earth's surface is Hydrosphere.

Edmund Hilary and Tenzing Norgay sherpa were first men to climb Mt.Everest on 29th May 1953.

Junko Tabei of Japan was the first woman to climb Mt.Everest.

LITHOSPHERE : The solid portion of the earth - comprising the rocks of the earth’s crust and the thin layers of soil that contain nutrient elements which sustain organisms.

Two main divisions of the earth’s surface :

  • The large landmasses are known as the continents

  • The huge water bodies are called the ocean basins ( All the oceans of the world are connected with one another)

Continents : Page 32 : Greater part of the land mass lies in the Northern Hemisphere.

- There are 7 major continents: 1. Asia :

  • Asia is largest continent with 1/3rd of land area of the earth on the Eastern Hemisphere.

  • Asia is separated from Europe by the Ural mountains on the west.

2. Europe : Smaller ; lies to west of Asia ; bound by water on 3 sides ; combined landmass of Europe and Asia is called the Eurasia. 3. Africa :

  • Africa is the second largest continent.

  • Africa is the only continent through which tropic of cancer, the equator and the tropic of cancer passes.

  • World's largest hot desert Sahara is located in Africa.

  • World's longest river The Nile flows through Africa.

4. North America : North America is linked to South America by a very narrow strip of land called the Isthmus of Panama.

Page 33 : 5. South America : has world's largest river Amazon + World’s Longest mountain range The Andes. 6. Australia : Lies entirely in S.Hemisphere. called as Island continent – as it is surrounded by oceans on all sides. 7. Antarctica : Lies entirely in S.Hemisphere. Made of permanent thick ice sheets. HYDROSPHERE:

  • The earth is called the blue planet as - 71 percent of it comprises water i.e., in all its forms.

  • Hydrosphere : As running water in oceans and rivers and in lakes, ice in glaciers, underground water and the water vapour in atmosphere

  • More than 97% of the Earth’s water is found in the oceans and is too salty for human use.

OCEANS : Page 34 :

  • Ocean waters are always moving.

  • The four major oceans are –

  1. The pacific ocean – Largest. 1/3rd. Mariana Trench, the deepest part of the earth lies in the pacific ocean.

  2. The Atlantic ocean – 2nd Largest + ‘S’ Shaped. Presence of indented costal lines – useful for harbours.

  3. the Arctic ocean - connected with Pacific ocean by a narrow stretch of shallow water known as Berring Strait.

  4. the Indian ocean –named after India + triangular in shape.

ATMOSPHERE :

  • The earth is surrounded by a layer of gas called the atmosphere.

  • Nitrogen 78 per cent, oxygen 21 per cent and other gases like carbondioxide, argon and others comprise 1 per cent by volume.

  • The density of the atmosphere varies with height. It is maximum at the sea level and decreases rapidly as we go up.

  • The temperature also decreases as we go upwards.

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

Page 37 :

Biosphere – The Domain of Life :

  • The biosphere is the narrow zone of contact between the land, water and air. It is in this zone that life, that is unique to this planet, exists i.e., from microbes and bacteria to huge mammals.

  • The organisms in the biosphere may broadly be divided into the plant kingdom and the animal kingdom.

Chapter 6 - Major Landforms of the Earth

Page 39 + 40 :

The earth has an infinite variety of landforms – From rugged to flat. Landforms evolved through 2 process :

  • Internal – which leads to upliftment + sinking of the earth’s surface at several places.

  • External - which is continuous wearing down + rebuilding of the Earth’s surface.

Based on elevation and Slope = it can be categorised into – Mountains, Plateaus, and Plains.

Land surface higher than the surrounding areas = Hill.

Hill with elevation of more than 600 metres= Mountain.

MOUNTAINS :

  • It is natural elevation of the earth surface + surface higher than surrounding area.

  • Glaciers are the mountains with permanently frozen rivers of ice.

Page 41 :

  • Arrangement of mountains in a line – is called Range. The Himalayas, the Alps and the Andes are mountain ranges of Asia, Europe and South America, respectively.

There are three types of mountains : FBV.

1. Fold mountains :

  • Himalayan Mountains and the Alps are young fold mountains

  • Aravali range – oldest.

  • Appalachians in North America + the Ural mountains in Russia have rounded features and low elevation. They are very old fold mountains.

2. Block mountains : Created when large areas are broken and displaced vertically. The uplifted blocks are termed as horsts and the lowered blocks are called graben.

Example : Rhine valley and the Vosges mountain in Europe.

3.Volcanic mountains : are formed due to volcanic activity.

Example : Mt.Kilimanjaro in Africa and Mt.Fujiyama in Japan

General facts :

  • The mountains are a storehouse of water + river source (Glacier)

  • Its water – used for irrigation and generation of hydro-lectricity.

  • The river valleys and terraces are ideal for cultivation of crops.

  • Mountains have a rich variety of flora and fauna.

Mauna Kea (Hawaii) in the Pacific Ocean is an undersea mountain. It is higher than Mount Everest being 10,205 metres high.

Page 42 :

PLATEAUS :

  • It is an elevated flat-topped land above the surrounding area having one or more sides with steep slopes.

  • -Plateaus, like mountains may be young or old.

  • 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.

  • Plateaus are very useful because they are rich in mineral deposits.

  • In India huge reserves of iron, coal and manganese are found in the Chhotanagpur plateau.

  • In the plateau areas, there may be several waterfalls as the river falls from a great height.

Example : Hundru falls in the Chhotanagpur plateau on the river Subarnarekha and the Jog falls in Karnataka are examples of such waterfalls.

  • lava plateaus are rich in black soil that are fertile and good for cultivation.

Page 43:

PLAINS :

  • Plains are large stretches of flat land – not more than 200 metres above mean sea level.

  • Formed by rivers and their tributaries ; therefore very fertile.

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. It is from these deposits that plains are formed.

  • They are very thickly-populated regions of the world. Plains are the most useful areas for human habitation. There is great concentration of people as more flat land is available for building houses, as well as for cultivation.

  • In India, the Indo-Gangetic plains are the most densely populated regions of the country.

Chapter 7 : Our Country – India

  • Page 47:

India is located in the northern hemisphere. The Tropic of Cancer (23°30'N) passes almost halfway through the country. India has an area of about 3.28 million sq. km with vast geographical expanse :

  • North- bound by the lofty Himalayas.

  • Arabian Sea in the west,

  • the Bay of Bengal in the east

  • the Indian Ocean in the south, wash the shores of the Indian peninsula.

The peninsula is a piece of land that is surrounded by water on three sides.

  • The north-south extent from Kashmir to Kanyakumari is about 3,200 km. From south to north, main land of India extends between 8°4'N and 37°6'N latitudes

  • the east-west extent from Arunachal Pradesh to Kuchchh is about 2,900 km. From west to east, India extends between 68°7'E and 97°25'E longitudes.

Page 48 :

  • There are seven countries that share land boundaries with India. They are: 1. Afghanistan 2.Pakistan 3.China 4.Bangladesh 5.Bhutan 6.Myanmar 7.Nepal

  • Sri Lanka does not share boundary with India. It is a neighbouring country and is separated from India by the Palk Strait.

Page 49 : Delhi – NCR. Rajasthan is the largest state and Goa is the smallest state in terms of area.

PHYSICAL DIVISIONS : Page 50 :

HIMALAYA : The Himalayan Mountains are divided into three main parallel ranges.

  • The northernmost is the Great Himalaya or Himadri. The world’s highest peaks are located in this range.

  • Middle Himalaya or Himachal lies to the south of Himadri. Many popular hill stations are situated here.

  • The Shiwalik is the southernmost range.

Page 51 :

NORTH INDIAN PLAINS : The Northern Indian plains lie to the south of the Himalayas. They are generally level and flat. These are formed by the alluvial deposits laid down by the rivers– the Indus, the Ganga, the Brahmaputra and their tributaries. These river plains provide fertile land for cultivation. That is the reason for high concentration of population in these plains.

PENINSULAR PLATEAU : To the south of northern plains lies the Peninsular plateau. It is triangular in shape. -The relief is highly uneven. This is a region with numerous hill ranges and valleys. -Aravali hills, one of the oldest ranges of the world, border it on the north-west side. -The Vindhyas and the Satpuras are the important ranges.

  • The rivers Narmada and Tapi flow through these ranges. These are west-flowing rivers that drain into the Arabian Sea.

WEST : In the western part of India lies the Great Indian desert. It is a dry, hot and sandy stretch of land.

GHATS :

  • The Western Ghats or Sahyadris border the plateau in the west and the Eastern Ghats provide the eastern boundary.

  • While the Western Ghats are almost continuous, the Eastern Ghats are broken and uneven

  • To the West of the Western Ghats and the East of Eastern Ghats lie the Coastal plains. The western coastal plains are very narrow. The eastern Coastal plains are much broader.

EAST-FLOWING RIVERS : The rivers Mahanadi, Godavari, Krishna and Kaveri drain into the Bay of Bengal. -These rivers have formed fertile deltas at their mouth.

  • The Sunderban delta is formed where the Ganga and Brahmaputra flow into the Bay of Bengal.

ISLAND : Two groups of islands also form part of India - Lakshadweep and Andaman & nicobar

  • Lakshadweep Islands are located in the Arabian Sea. These are coral islands located off the coast of Kerala. Corals are skeletons of tiny marine animals called Polyps. When the living polyps die, their skeletons are left. Other poplyps grow on top of the hard skeleton which grows higher and higher, thus forming the coral islands

  • The Andaman and the Nicobar Islands lie to the southeast of the Indian mainland in the bay of bengal.

Chapter 8 : INDIA : CLIMATE , VEGETATION AND WILDLIFE

Page 56 :

  • Weather - day to day changes

  • Major seasons in India :

  • Cold Weather Season (Winter) December to February : Cool winds from north to south., therefore low temperature in Northern India.

  • Hot Weather Season (Summer) March to May - as sun rays fall in this region. Hot and dry winds called loo, blow during the summer days.

Page 57 :

  • Southwest Monsoon Season (Rainy) June to September : Monsoon. Winds from Arabian sea + BOB – blow towards land.

  • Season of Retreating Monsoon (Autumn) October and November : Winds from Mainland to BOB.

  • The climate is about the average weather condition,which have been measured over many years. The climate of India has broadly been described as Monsoon type

  • Monsoon is taken from the Arabic word ‘mausim’, which means seasons.

  • Due to India’s location in the tropical region, most of the rain is brought by monsoon winds. The climate of a place is affected by its location, altitude, distance from the sea, and relief.

NATURAL VEGETATION : Page 58 :

Vegetation of India can be divided into five types –

  1. Tropical Rain forest :

  • Tropical Rain Forests occur in the areas which receive heavy rainfall.

  • Important trees found in these forests are mahogany, ebony and rosewood.

  • Andaman and Nicobar Islands, parts of North-Eastern states and a narrow strip of the Western slope of the Western Ghats are home of these forests.

Page 59 :

2. Tropical deciduous forest :

  • These forests are also called monsoon forests

  • They are less dense.

  • They shed their leaves at a particular time of the year.

  • Important trees of these forests are sal, teak, peepal, neem and shisham. They are found in Madhya Pradesh, Uttar Pradesh, Bihar, Jharkhand, Chhattisgarh, Odisha, and in parts of Maharashtra.

3. Thorny bushes :

  • The leaves are in the form of spines to reduce the loss of water.

  • Cactus, khair, babool, keekar are important and are found in the states of Rajasthan, Punjab, Haryana, Eastern slopes of Western Ghats and Gujarat.

Page 60 :

4. Mountain vegetation :

  • At a height between 1500 metres and 2500 metres most of the trees are conical in shape. These trees are called coniferous trees

  • . Chir, Pine and Deodar are important trees of these forests.

5.Mangrove forests :

  • These forests can survive in saline water.

  • They are found mainly in Sunderbans in West Bengal and in the Andaman and Nicobar Islands.

  • Sundari is a well-known species of trees in mangrove forests after which Sunderbans have been named.

WILDLIFE:

  • The tiger is our national animal.

  • Gir forest in Gujarat is the home of Asiatic lions.

  • Elephants and one-horned rhinoceroses roam in the forests of Assam. .Elephants are also found in Kerala and Karnataka.

  • Camels and wild asses are found in the Great Indian desert and the Rann of Kuchchh respectively.

  • Wild goats, snow leopards, bears, etc. are found in the Himalayan region.

  • The peacock is our national bird.

  • The Government has also started Project Tiger and Project Elephant to protect these animals.

  • Every year we observe wildlife week in the first week of October, to create awareness of conserving the habitats of the animal kingdom.

  • .Some birds such as the Pelican, Siberian Crane, Stork, Flamingo, Pintail Duck and Curlew migrate to our country in the winter season every year.

  • Siberian Cranes migrate from Siberia. They arrive in December and stay till early March.

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