Geography 6th Std. PDF - Jammu & Kashmir Board

The Earth Our Habitat Textbook of Geography for Class 6th  The Earth Our Habitat Textbook of Geography for Class 6th Jammu & Kashmir Board Of School Education  # No part of this book may be reproduced, First Edition...

The Earth Our Habitat Textbook of Geography for Class 6th  The Earth Our Habitat Textbook of Geography for Class 6th Jammu & Kashmir Board Of School Education  # No part of this book may be reproduced, First Edition stored in a retrieval system or transmitted, November 2019 in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of the publisher. # This book is sold subject to the condition that it shall not, by way of trade, be lent, re- sold, hired out or otherwise disposed of in any form of binding or cover other than that in which it is published without the written consent of the publisher. Cover and Layout Showkat A Baba Professional Graphics Srinagar / 9419974394 FOREWORD C urriculum updating is a continuous process and hence the J&K Board of School Education has brought out the revised curricula for different classes. Social Science is of crucial importance because it helps learners in understanding environment in a broader perspective and a reasonable outlook. This Textbook of Social Science aims at enabling students to develop critical understanding of society, lay foundation for an analytical and creative mindset. Change in the text book entails the change in the content and pedagogical practice of curriculum. Main objective of this change is to enable the children to understand the society and the world in which we live, as well as, understand socio-Geographical scenario. In the light of the NCF-2005, the social and physical aspects of the Geography of J&K and Ladakh have been included in the book. It is hoped that through the perception of local Geography, the students are in a position to understand it. I appreciate the hard work done by the Academic Division and textbook development committee responsible for development of this book. I acknowledge and place on record my deep appreciation to the Director NCERT and Head curriculum Division, NCERT for their support and cooperation. The contents in this book have been adopted completely from the NCERT textbook of Geography for class VI titled “The Earth –Our Habitat” and one chapter on local speci ic content pertaining to Jammu Kashmir and Ladakh has been incorporated. The book has been contextualized and presented in an interesting manner to attract the attention and to create a sense of belongingness among the learners. As an organization committed to systematic reform and continuous improvement in the quality of its textbooks, JKBOSE welcomes comments and suggestions which will enable us to undertake further revision and re inement. I hope this textbook of Geography shall sensitize learners about the Geographical perspective in an explicit manner. (Prof.Veena Pandita) Chairperson  TEXTBOOK DEVELOPMENT COMMITTEE OF NCERT CHAIRPERSON, ADVISORY COMMITTEE FOR TEXTBOOKS IN SOCIAL SCIENCES AT THE UPPER PRIMARY LEVEL Hari Vasudevan, Professor, Department of History, University of Calcutta, Kolkata CHIEF ADVISOR Vibha Parthasarathi, Principal (Retd.), Sardar Patel Vidyalaya, New Delhi MEMBERS Anjali Swami, TGT, N.C. Jindal Public School, New Delhi Anshu, Reader, Kirorimal College, University of Delhi, Delhi Durga Singh, PGT, Kendriya Vidyalaya No.2, Ahmedabad Shahla Mujib, PGT, Govt. Boys Sr. Sec. School,Hari Nagar Ashram, New Delhi MEMBER-COORDINATOR Aparna Pandey, Lecturer, Department of Education in Social Sciences NCERT, New Delhi ACKNOWLEDGEMENT T he J&K BOSE is grateful to the following subject experts for their hardwork, dedication and contribution in developing the local content of this textbook. 1. Dr. Mohd Sha i Bhatt, Assistant Professor, Deptt. Of Geography, University of Kashmir. 2. Ms. Aneeta Koul, Principal, Govt. Boys HSS, Akhnoor. 3. Ms. Vaneeta Manhas,Lecturer, Govt. SRML HSS, Jammu. 4. Ms. Seema Sharma, Master, Govt. Girls HSS, Satwari. 5. Mr. Navdeep Bhalwal, Teacher, GGHS Jourian. Member Coordinators Dr. Arif Jan, Assistant Director-KD Mr. Ranjeet Singh Manhas , Academic Officer-JD The J&K Board of School Education gratefully acknowledges the use of NCERT textbook of Geography for class VI in the development of this book. I express my gratitude to Prof. Veena Pandita (Chairperson) for her support and help in the development of the textbook. She has been a source of inspiration for all of us and without her guidance, this endeavour would have been impossible. I also extend my thanks to Prof. Abdul Wahid Makhdoomi (Joint Secretary) Publication. My sincere gratitude is due to the Curriculum Development & Research wing JD & KD for their untiring efforts for making this textbook available for the students of class VI. Suggestions from the stakeholders for the improvement of the Textbook shall be highly appreciated. (Dr. Farooq Ahmad Peer) Director Academics TABLE OF CONTENTS 1. The Earth in the Solar System.................................................... 1 2. Globe : Latitudes and Longitudes............................................. 10 3. Motions of the Earth..................................................................... 18 4. Maps................................................................................................. 23 5. Major Domains of the Earth...................................................... 30 6. Major Landforms of the Earth................................................... 39 7. Our Country – India...................................................................... 47 8. India : Climate, Vegetation and Wildlife................................. 56 9. Jammu, Kashmir & Ladakh at A Glance................................ 65 Appendix I....................................................................................... 72 Appendix II..................................................................................... 73  1 THE EARTH IN THE SOLAR SYSTEM How wonderful it is to watch the sky after sunset! One Let’s Do would first notice one or two bright dots shining in You’ll need : 1 torch, the sky. Soon you would see the number increasing. 1 sheet of plain You cannot count them any more. The whole sky is paper, pencil and a filled with tiny shining objects – some are bright, others needle. dim. It seems as if the sky is studded with diamonds. Step : They all appear to be twinkling. But if you look at 1. Place the torch in the centre of the paper with its glass them carefully you will notice that some of them do front touching the paper. not twinkle as others do. They simply glow without 2. Now draw a circle around any flicker just as the moon shines. the torch. Along with these bright objects, you may also see 3. Perforate the paper with the needle within the circled the moon on most of the days. It may, however, appear area. at different times, in different shapes and at different 4. Now place the perforated positions. You can see the full moon only once in about circle part of the paper on a month’s time. It is Full moon night or Poornima. A the glass front and wrap the fortnight later, you cannot see it at all. It is a New paper around the torch with a rubber band. moon night or Amavasya. On this day, you can watch 5. Take care that the switch the night sky best, provided it is a clear night. of the torch is not covered. Do you wonder why can’t we see the moon and all 6. In a dark room, stand at those bright tiny objects during day time? It is because some distance facing a the very bright light of the sun does not allow us to see plain wall. Switch off all other lights. Now flash the all these bright objects of the night sky. torch light on the wall. You The sun, the moon and all those objects shining in will see numerous dots of the night sky are called celestial bodies. light on the wall, like stars Some celestial bodies are very big and hot. They shine in the night. are made up of gases. They have their own heat and 7. Switch on all the lights in the room. All dots of light light, which they emit in large amounts. These celestial will be almost invisible. bodies are called stars. The sun is a star. 8. You may now compare the Countless twinkling stars in the night sky are situation with what happens similar to the sun. But we do not feel their heat or to the bright objects of the light, and they look so tiny because they are very very far night sky after the sun rises from us. in the morning.  You must have noticed that all objects look smaller when seen from a distance. How small an aeroplane looks when it is flying at a great height! While watching the night sky, you may notice various patterns formed by different groups of stars. These are called constellations. Ursa Major or Big Bear is one such constellation. One of the most easily recognisable constellation is the Saptarishi (Sapta- seven, rishi-sages). It is a group of seven stars (Figure 1.1) that forms a part of Ursa Major Constellation. Ask someone elder in your family or neighbourhood to show you more stars, planets and constellations in the sky. In ancient times, people used to determine directions during the night with the help of 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. Look at Figure 1.1. You will notice that, if an imaginary line is drawn joining the pointer stars and extended further, it will point to the Pole Star. Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such Figure 1.1 : Saptarishi and the bodies are called planets. The word ‘planet’ comes from North Star the Greek word “Planetai” which means ‘wanderers’. The earth on which we live is a planet. It gets all its heat and light from the sun, which is our nearest star. If we look at the earth from a great distance, say the moon, it will appear to be shining just as the moon. Interesting Fact The moon that we see in the sky is a satellite. It is a Jupiter, Saturn and companion of our earth and moves round it. Like our Uranus have rings earth, there are seven other planets that get heat and around them. These light from the sun. Some of them have their moons too. are belts of small debris. These rings may be THE SOLAR SYSTEM seen from the earth with the help of powerful The sun, eight planets, satellites and some other telescopes. celestial bodies known as asteroids and meteoroids 2 THE EARTH : OUR HABITAT THE EARTH IN THE SOLAR SYSTEM 1. MERCURY - One orbit around sun - 88 days, 5. JUPITER - One orbit around sun - 11 years, 11 8. NEPTUNE - One orbit around sun - 164 years. One spin on axis - 59 days. months about 12 years. One spin on One spin on axis-16 hours 7 2. VENUS - One orbit around sun - 255 days. axis - 9 hours, 56 minutes, number of minutes, number of moons - 13. One spin on axis - 243 days moons - about 53 3. EARTH - One orbit around sun - 365 days. 6. SATURN - One orbit around sun - 29 years, 5 One spin on axis - 1 day months. One spin on axis - 10 hours 40 Number of moons - 1 minutes, number of moons - about 53. 4. MARS - One orbit around sun - 687 days 7. URANUS - One orbit around sun - 84 years. One One spin on axis - 1 day, spin around axis - 17 hours 14 minutes, number of moons - 02 number of moons - about 27. Inner planets - very close to the sun. They are made up Outer Planets - Very-very far from the sun and are huge planets made up of gases and liquids. of rocks. 3 Figure 1.2 : The Solar System Saurce: https://planetarynames.wr.usgs.gov/Page/Planets  Do you know? form the solar system. We often call it a solar family, ‘Sol’ in Roman with the sun as its Head. mythology is the ‘Sungod’. The Sun ‘Solar’ means ‘related to the sun’. The The sun is in the centre of the solar system. It is huge family of the sun is, and made up of extremely hot gases. It provides the therefore, called the solar pulling force that binds the solar system. The sun is system. Write down as many words using the word the ultimate source of heat and light for the solar solar on your own as you system. But that tremendous heat is not felt so much can. by us because despite being our nearest star, it is far Word Origin away from us. The sun is about 150 million km away from the earth. Many words used in a language may Planets have been taken from some other language. There are eight planets in our solar system. In order of Geography, for example, is their distance from the sun, they are: Mercury, an English word. It has its Venus, Earth, Mars, Jupiter, Saturn, Uranus and origin in Greek, which Neptune. relates to the description of the earth. It is made of An easy way to memorise the name of the planets in two Greek words, ‘ge’ order of their distance from the sun is: meaning’ ‘earth’ and ‘graphia’ meaning ‘writing’. MY VERY EFFICIENT MOTHER JUST SERVED US NUTS. Find out more about the earth. All the eight planets of the solar system move around the sun in fixed paths. These paths are elongated. They are 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 Do you know? similar to that of the earth. Humans have T ill recently (August 2006), Pluto was also always been considered a planet. However, in a meeting of the fascinated gazing at the night International Astronomical Union, a decision was sky. Those who study the taken that Pluto like other celestial objects (Ceres, 2003 celestial bodies and their movements are called UB 313 ) discovered in recent past may be called astronomers. Aryabhatta ‘dwarf planets.” was a famous astronomer of ancient India. He said that The Earth the moon and the planets shine due to reflected The earth is the third nearest planet to the sun. In sunlight. Today, astronomers size, it is the fifth largest planet. It is slightly flattened all over the world are busy at the poles. That is why, its shape is described as a exploring the universe. Geoid. Geoid means an earth-like shape. 4 THE EARTH : OUR HABITAT  Conditions favourable to support life are probably Do you know? found only on the earth. The earth is neither too hot Light travels at nor too cold. It has water and air, which are very the speed of essential for our survival. The air has life-supporting about 300,000 gases like oxygen. Because of these reasons, the earth km per second. is a unique planet in the solar system. Yet, even with this speed, From the outer space, the earth appears blue the light of the sun takes because its two-thirds surface is covered by water. It about eight minutes to is, therefore, called a blue planet. reach the earth. The Moon Our earth has only one Interesting Fact satellite, that is, the moon. Its diametre is Neil Armstrong was only one-quarter that of the first man to the earth. It appears so step on the surface big because it is nearer to of the moon on 21 July our planet than other 1969. Find out whether any Indian has landed on celestial bodies. It is the moon? about 3,84,400 km away from us. Now you can compare the distance of Figure 1.3 : The moon as seen from the space the earth from the sun A Satellite is a celestial and that from the moon. body that moves around The moon moves around the earth in about 27 days. the planets in the same It takes exactly the same time to complete one spin. As way as the planets move a result, only one side of the moon is visible to us on around the sun. the earth. A Human-made Satellite The moon does not have conditions favourable for is an artificial body. It is life. It has mountains, plains and depressions on its designed by scientists to gather information about the universe or for communication. It is carried by a rocket and placed in the orbit around the earth. Some of the Indian satellites in space are INSAT, IRS, EDUSAT, etc. Rocket launch Rocket falls back to the Earth Satellite enters orbit ? What do animals and plants require in order Figure 1.4 : Human-made Satellite to grow and survive? THE EARTH IN THE SOLAR SYSTEM 5  surface. These cast shadows on the moon’s surface. Look at the full moon and observe these shadows. Asteroids Apart from the stars, planets and satellites, there are numerous tiny bodies which also move around the sun. These bodies are called asteroids. They are found Figure 1.5 : Asteroid between the orbits of Mars and Jupiter (Figure 1.2). Scientists are of the view that asteroids are parts of a planet which exploded many years back. Meteoroids The small pieces of rocks which move around the sun are called meteoroids. Sometimes these meteoroids come near the earth and tend to drop upon it. During this process due to friction with the air they get heated up and burn. It causes a flash of light. Sometimes, a meteor without being completely burnt, falls on the earth and creates a hollow. Do you see a whitish broad band, like a white glowing path across the sky on a clear starry night? It is a cluster of millions of stars. This band is the Milky Way galaxy (Figure 1.6). Our solar system is a part of this galaxy. In ancient India, it was imagined to be a river of light flowing in the sky. Thus, it was named Akash Ganga. 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. It is difficult to imagine how big the universe is. Scientists are still trying to find out more and more about it. We are not certain about its size but we know that all of us – you and I belong to this universe. Figure 1.6 : Milky Way 6 THE EARTH : OUR HABITAT  Can you relate yourself with the universe now? You are on the earth and the earth is a part of the solar system. Our solar system is a part of the Milky Way galaxy which is part of the universe. Think about the universe, and the fact that it contains millions of such galaxies. How do you fit in the picture? 1. Answer the following questions briefly. (a) How does a planet differ from a star? (b) What is meant by the ‘Solar System’? (c) Name all the planets according to their distance from the sun. (d) Why is the Earth called a unique planet? (e) Why do we see only one side of the moon always? (f) What is the Universe ? 2. Tick the correct answer. (a) The planet known as the “Earth’s Twin” is (i) Jupiter (ii) Saturn (iii) Venus (b) Which is the third nearest planet to the sun ? (i) Venus (ii) Earth (iii) Mercury (c) All the planets move around the sun in a (i) Circular path (ii) Rectangular path (iii) Elongated path (d) The Pole Star indicates the direction to the (i) South (ii) North (iii) East THE EARTH IN THE SOLAR SYSTEM 7  (e) Asteroids are found between the orbits of (i) Saturn and Jupiter (ii) Mars and Jupiter (iii) The Earth and Mars 3. Fill in the blanks. (a) A group of ________ forming various patterns is called a ________. (b) A huge system of stars is called________. (c) ________is the closest celestial body to our earth. (d) ________is the third nearest planet to the sun. (e) Planets do not have their own________ and ___________________. 1. Prepare a chart of the solar system. 2. During a vacation visit a planetarium and describe your experience in the class. 3. Organise a quiz contest on the earth and the solar system. 1. The sun is commonly known as Soorya or Sooraj in Hindi, Find out its name in different languages of our country. Take help of your friends, teachers and neighbours. 2. You might have heard that people make human chains and run for world peace etc. You can also make a human solar system and run for fun. Step 1: All children of your class can play this game. Assemble in a big hall or on a playground. Step 2: Now draw 8 circles on the ground as shown in the figure drawn on the opposite page. Use a 5-metre long rope. Mark at every half a metre with a chalk or ink. Place a small nail to mark the centre. Now hold one end of the rope at the central position. Ask your friend to hold a chalk at the ½ metre mark and move around the nail holding rope and chalk together on the ground. You have drawn one circle just as you do on paper using a compass and a pencil. Draw other circles in the same manner. Step 3: Prepare 10 placards. Name them as Sun., Moon, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. 8 THE EARTH : OUR HABITAT  Step 4: Select 10 children in the following order and give each one of them a placard. Order of placard distribution The Sun - tallest, The moon - smallest; Mercury, Mars, Venus and Earth (almost equal heights); Neptune, Uranus, Saturn and Jupiter taller than the earlier four planets but smaller than the Sun. Now ask the children holding placards to take their places with the Sun in the centre in their orbits. Ask the child holding the moon placard to keep the hand of the child holding the earth placard always. Now your Solar System is almost ready to go into action. Now make everybody move slowly in the anti-clockwise direction. Your class has turned into a small human replica of the solar system. While moving on your orbit you can also turn around. For everybody the spin should be anti-clock wise except for Venus and Uranus who will make the spin in the clock-wise direction. THE EARTH IN THE SOLAR SYSTEM 9  2 GLOBE : LATITUDES AND LONGITUDES In the previous chapter, you have read that our planet earth is not a sphere. It is slightly flattened at the North and the South Poles and bulge in the middle. Can you imagine how it looks? You may look at a globe carefully in your classroom to get an idea. Globe is a true model (miniature form) of the earth (Figure 2.1). Globes may be of varying size and type – big ones, which cannot be carried easily, small pocket globes, and globe-like balloons, which can be inflated and are handy and carried with ease. The globe is not fixed. It can be rotated the same way as a top spin or a potter’s wheel is rotated. On the globe, countries, continents Figure 2.1 : Globe and oceans are shown in their correct size. It is difficult to describe the location of a point on a sphere like the earth. Now the question arises as to how to locate a place on it? We need certain points of reference and lines to find out the location of places. Let’s Do You will notice that a needle is fixed through the Take a big round globe in a tilted manner, which is called its axis. Two potato or a ball. points on the globe through which the needle passes Pierce a knitting are two poles – North Pole and South Pole. The globe needle through it. The can be moved around this needle from west to east needle resembles the axis shown in a globe. You can just as the earth moves. But, remember there is a major now move the potato or the difference. The real earth has no such needle. It moves ball around this axis from around its axis, which is an imaginary line. left to right. Another 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 halves. Therefore, the equator is an imaginary circular line and is a very important reference point to locate places on the earth. 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. Since the distance from the equator to either of the poles is one-fourth of a circle round the earth, it will measure ¼th of 360 degrees, i.e. 90°. Thus, 90 degrees north latitude marks the North Pole and 90 degrees south latitude marks the South Pole. As such, all parallels north of the Figure 2.2 : Latitude equator are called ‘north latitudes.’ Similarly all parallels south of the equator are called ‘south latitudes.’ Do you know? The value of each latitude is, therefore, followed by By measuring either the word north or south. Generally, this is the angle of the indicated by the letter ‘N’ or ‘S’. For example, both Pole Star from Chandrapur in Maharashtra (India) and Belo your place, you can know Horizonte in Brazil (South America) are located on the latitude of your place. parallels of about 20° latitude. But the former is 20° north of the equator and the latter is 20° south of it. We, therefore, say that Chandrapur is situated at 20° N latitude and Belo Horizonte is situated at 20° S latitude. We see in Figure 2.2 that as we move away from the equator, the size of the parallels of latitude decreases. IMPORTANT PARALLELS OF LATITUDES Besides the equator (0°), the North Pole (90°N) and the South Pole (90° S), there are four important parallels of latitudes– (i) Tropic of Cancer (23½° N) in the Northern Hemisphere. (ii) Tropic of Capricorn (23½° S) in the Southern Hemisphere. (iii) Arctic Circle at 66½° north of the equator. (iv) Antarctic Circle at 66½° south of the equator. Figure 2.3 : Important Latitudes and Heat Zones GLOBE : LATITUDES AND LONGITUDES 11  HEAT ZONES OF THE EARTH The mid-day sun is exactly overhead at least once a year on all latitudes in between the Tropic of Cancer and the Tropic of Capricorn. This area, therefore, receives the maximum heat and is called the Torrid Zone. The mid-day sun never shines overhead on any latitude beyond the Figure 2.4 : (a) Tropic of Cancer and the Tropic of Torch-light falling on a straight Capricorn. The angle of the sun’s rays surface is bright and covers a goes on decreasing towards the poles. As smaller area. such, the areas bounded by the Tropic of Cancer and the Arctic Circle in the Northern Hemisphere, and the Tropic of Capricorn and the Antarctic Circle in the Southern Hemisphere, have moderate temperatures. These are, therefore, called Temperate Zones. Areas lying between the Arctic Circle Figure 2.4 : (b) and the North Pole in the Northern Hemisphere and the Antarctic Circle and Torch-light falling on a slanted the South Pole in the Southern surface is less bright but covers a Hemisphere, are very cold. It is because bigger area. here the sun does not rise much above the horizon. Therefore, its rays are always slanting and provide less heat. These are, therefore, called Frigid Zones (very cold). WHAT ARE LONGITUDES? To fix the position of a place, it is necessary to know something more than the latitude of that place. You can see, for example, that Tonga Islands (in the Pacific Ocean) and Mauritius Islands (in the Indian Ocean) are situated on the same latitude (i.e., 20° S). Now, in order to locate them precisely, we must find out how far east or west these places are from a given line of reference running from the North Pole to the South Pole. These lines of references Figure 2.5 : Longitudes are called the meridians of longitude, 12 THE EARTH : OUR HABITAT and the distances between them are measured in Let’s Do ‘degrees of longitude.’ Each degree is further divided Draw a circle. into minutes, and minutes into seconds. They are semi- Let the Prime circles and the distance between them decreases meridian divide steadily polewards until it becomes zero at the poles, it into two equal halves. where all the meridians meet. Colour and label the Unlike parallels of latitude, all meridians are of equal eastern hemisphere and length. Thus, it was difficult to number the meridians. the western hemisphere. Hence, all countries decided that the count should Similarly draw another begin from the meridian which passed through circle and let the equator Greenwich, where the British Royal Observatory is divide it into two halves. located. This meridian is called the Prime Meridian. Now colour the Northern hemisphere and Southern Its value is 0° longitude and from it we count 180° hemisphere. eastward as well as 180° westward. The Prime Meridian and 180° meridian divide the earth into two equal halves, the Eastern Hemisphere and the Western Hemisphere. Therefore, the longitude of a place is followed by the letter E for the east and W for the west. It is, however, interesting to note that 180° East and 180° West meridians are on the same line. Now look at the grid of the parallels of latitude and meridians of longitude on the globe (Figure 2.6). You can locate any point on the globe very easily if you know its latitude and longitude. For example, Dhubri in Assam is situated at 26° N latitude and 90° E longitude. Find out the Figure 2.6 : Grid point where these two lines cut each other. That point will be the location of Dhubri. To understand this clearly draw equidistant vertical and horizontal lines on a paper (Figure 2.7). Label the vertical rows with numbers and horizontal rows with letters, draw some small circles randomly on points where these horizontal and vertical lines intersect each other. Name these small circles as a, b, c, d and e. Let vertical lines represent East Longitudes and horizontal lines as North Latitudes. Now you will see that circle ‘a’ is located on B° N latitude and 1° E longitude. Find out the location of other circles. Figure 2.7 GLOBE : LATITUDES AND LONGITUDES 13  14 Figure 2.8 : Time zones of the World THE EARTH : OUR HABITAT LONGITUDE AND TIME The best means of measuring time is by the movement of the earth, the moon and the planets. The sun regularly rises and sets every day, and naturally, it is the best time-keeper throughout the world. Local time can be reckoned by the shadow cast by the sun, which is the shortest at noon and longest at sunrise and sunset. When the Prime Meridian of Greenwich has the sun at the highest point in the sky, all the places along this meridian will have mid-day 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 (Figure 2.8). The rate of difference can be calculated as follows. The earth rotates 360° in about 24 hours, which means 15° an hour or 1° in four minutes. Thus, when it is 12 noon at Greenwich, the time at 15° east of Greenwich will be 15 × 4 = 60 minutes, i.e., 1 hour ahead of Greenwich time, which means 1 p.m. But at 15° west of Greenwich, the time will be behind Greenwich time by one hour, i.e., it will be 11.00 a.m. Similarly, at 180°, it will be midnight when it is 12 noon at Greenwich. At any place a watch can be adjusted to read 12 o’clock when the sun is at the highest point in the sky, i.e., when it is mid-day. The time shown by such a watch will give the local time for that place. You can see that all the places on a given meridian of longitude have the same local time. WHY DO WE HAVE STANDARD TIME? The local time of places which are on different meridians are bound to differ. For example, it will be difficult to prepare a time-table for trains which cross several longitudes. In India, for instance, there will be a difference of about 1 hour and 45 minutes in the local times of Dwarka in Gujarat and Dibrugarh in Assam. It is, therefore, necessary to adopt the local time of some central meridian of a country as the standard time for the country. In India, the longitude of 82½° 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). Figure 2.9 : Indian Standard Meridian GLOBE : LATITUDES AND LONGITUDES 15  Kabeer lives in a small town near Bhopal. He tells his friend Alok that they will not be able to sleep tonight. A day and night cricket match between India and England had started at 2 p.m. in London. This means that the match would begin at 7.30 p.m. in India and finish well into the night. Do you know what is the time difference between India and England? India located east of Greenwich at 82°30'E is 5 hours and 30 minutes ahead of GMT. So it will be 7:30 p.m. in India when it is 2:00 p.m. noon in London. Some countries have a great longitudinal extent and so they have adopted more than one standard time. For example, in Russia, there are as many as eleven standard times. The earth has been divided into twenty-four time zones of one hour each. Each zone thus covers 15° of longitude. 1. Answer the following questions briefly. (a) What is the true shape of the earth? (b) What is a globe? (c) What is the latitudinal value of the Tropic of Cancer? (d) What are the three heat zones of the Earth? (e) What are parallels of latitude and meridians of longitude? (f) Why does the torrid zone receive maximum amount of heat? (g) Why is it 5.30 p.m. in India and 12.00 noon in London? 2. Tick the correct answers. (a) The value of the prime meridian is (i) 90° (ii) 0° (iii) 60° (b) The frigid zone lies near (i) the Poles (ii) the Equator (iii) the Tropic of Cancer (c) The total number of longitudes are (i) 360 (ii) 180 (iii) 90 (d) The Antarctic circle is located in (i) the Northern hemisphere (ii) the Southern hemisphere (iii) the Eastern hemisphere (e) Grid is a network of (i) parallels of latitudes and merdians of longitudes (ii) the Tropic of Cancer and the Tropic of Capricorn (iii) the North Pole and the South Pole 16 THE EARTH : OUR HABITAT  3. Fill in the blanks. (a) The Tropic of Capricorn is located at _________________. (b) The Standard Meridian of India is ____________________. (c) The 0° Meridian is also known as ____________________. (d) The distance between the longitudes decreases towards___________. (e) The Arctic Circle is located in the ____________ hemisphere. 1. Draw a diagram of the globe showing the earth’s axis, the Equator, Tropics of Cancer and Capricorn, Arctic Circle and Antarctic Circle. 1. Draw and cut out six circles of the same size (approx. 3 cm. radius) from cardboard. Mark diametres (NS, EW) and 23½o angles on each face of the circles as shown on the figure. Place the circle one on top of the other and stitch along the line NS. Now there are twelve semi-circles. Let one semi-circle represent 0o or Greenwich Meridian (Prime Meridian). The 6th semi-circle from it will be the 180o Meridian. Between the 0o and 180o there are 5 semi-circles on both sides which are West and East longitudes 30o apart. On two ends of the stapled line stick pins to represent the North and South Poles. A rubber band around the model touching the EW points will represent the Equator. Two rubber bands touching the 23½o points, South and North of the EW points will represent the tropics. GLOBE : LATITUDES AND LONGITUDES 17  3 MOTIONS OF THE EARTH Let’s Do As you know that the earth has two types of motions, namely rotation and revolution. Rotation is the Take a ball to movement of the earth on its axis. The movement of represent the earth and a the earth around the sun in a fixed path or orbit is lighted candle to represent called Revolution. the sun. Mark a point on The axis of the earth which is an imaginary line, the ball to represent a makes an angle of 66½° with its orbital plane. The town X. Place the ball in plane formed by the orbit is known as the orbital plane. such a way that the town The earth receives light from the sun. Due to the X is in darkness. Now spherical shape of the earth, only half of it gets light rotate the ball from left to from the sun at a time (Figure 3.2). The portion facing right. As you move the ball the sun experiences day while the other half away from slightly, the town will the sun experiences night. The circle that divides the have its sunrise. As the day from night on the globe is called the circle of ball continues to move, illumination. This circle does not coincide with the the point X gradually gets axis as you see in the Figure 3.2. The earth takes about away from the sun. This is sunset. 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. Figure 3.1 : Inclination of the Earth’s axis and the orbital plane Figure 3.2 : Day and Night on the Earth due to rotation  What would happen if the earth did not rotate? The portion of the earth facing the sun would always experience day, thus bringing continuous warmth to Do you know? the region. The other half would remain in darkness and be freezing cold all the time. Life would not have The ancient Indian been possible in such extreme conditions. astronomer Aryabhata had stated that ‘the The second motion of the earth around the sun in earth is round and its orbit is called revolution. It takes 365¼ days (one rotates on its own axis’ 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. Figure 3.3 : Revolution of the Earth and Seasons 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. Find out when will the next leap year be? From the Figure 3.3, it is clear that the earth is going around the sun in an elliptical orbit. Notice that throughout its orbit, the earth is inclined in the same direction. A year is usually divided into summer, winter, spring and autumn seasons. Seasons change due to the change in the position of the earth around the sun. MOTIONS OF THE EARTH 19  Let’s Do Do you know how to draw an ellipse? Take a pencil, two pins and a loop of thread. Now fix these pins on a paper as shown in the figure. Put the loop on the paper enclosing these two pins inside the loop. Now hold the pencil and draw the line keeping the thread tight and moving the pencil along it. The figure represents an ellipse. Look at the Figure 3.3. You will see that on 21st June, the Northern Hemisphere is tilted towards the sun. The rays of the sun fall directly on the Tropic of Cancer. As a result, these areas receive more heat. The areas near the poles receive less heat as the rays of the sun are slanting. The North Pole is inclined towards the sun and the places beyond the Arctic Circle experience continuous daylight for about six months. 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 21st June. At this time Let’s Do in the Southern Hemisphere all these conditions are To understand reversed. It is winter season there. The nights are longer the earth’s than the days. This position of the earth is called the inclination in Summer Solstice. the same direction, draw On 22nd December, the Tropic of Capricorn receives a big ellipse on the ground and take a flag w i t h a direct rays of the sun as the South Pole tilts towards stick. Stand anywhere on it. As the sun’s rays fall vertically at the Tropic of the line of the ellipse. Capricorn (23½° S), a larger portion of the Southern Point your flag to a fixed Hemisphere gets light. Therefore, it is summer in the point far away like on a Southern Hemisphere with longer days and shorter tree-top. Now move along nights. The reverse happens in the Northern the ellipse keeping your Hemisphere. This position of the earth is called the flag always pointing towards that fixed point. Winter Solstice. Do you know that Christmas is In this way, the axis of the celebrated in Australia in the summer season? earth remains inclined On 21st March and September 23rd, direct rays of permanently in the same the sun fall on the equator. At this position, neither of position. The revolution of the poles is tilted towards the sun; so, the whole earth the earth and the experiences equal days and equal nights. This is called inclination of the earth’s an equinox. axis in a fixed direction cause seasons. 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, 20 THE EARTH : OUR HABITAT when it is spring in the Northern Hemisphere and autumn in the Southern Hemisphere. Thus, you find that there are days and nights and changes in the seasons because of the rotation and revolution of the earth respectively. 1. Answer the following questions briefly. (a) What is the angle of inclination of the earth’s axis with its orbital plane? (b) Define rotation and revolution. (c) What is a leap year? (d) Differentiate between the Summer and Winter Solstice. (e) What is an equinox? (f) Why does the Southern Hemisphere experience Winter and Summer Solstice in different times than that of the Northern Hemisphere? (g) Why do the poles experience about six months day and six months night? 2. Tick the correct answers. (a) The movement of the earth around the sun is known as (i) Rotation (ii) Revolution (iii) Inclination (b) Direct rays of the sun fall on the equator on (i) 21 March (ii) 21 June (iii) 22 December (c) Christmas is celebrated in summer in (i) Japan (ii) India (iii) Australia (d) Cycle of the seasons is caused due to (i) Rotation (ii) Revolution (iii) Gravitation 3. Fill in the blanks. (a) A leap year has _______________ number of days. (b) The daily motion of the earth is _______________. (c) The earth travels around the sun in ______________ orbit. (d) The sun’s rays fall vertically on the Tropic of ___________ on 21st June. (e) Days are shorter during ___________ season. MOTIONS OF THE EARTH 21  1. Make a drawing to show the inclination of the earth. 2. Record the timings of sunrise and sunset at your place taking help from your local newspaper on the 21st of each month and answer the following : (a) In which month are the days the shortest? (b) In which months are the days and nights nearly equal? 1. Draw different shapes of ellipses by placing two pins nearer and farther using the same loop of thread. Notice when the ellipse becomes circular. 2. On any sunny day, take a straight stick that is one metre long. Find out a clean and level place on the ground. Place this stick into the ground where it casts a distinctive (sharp) shadow. Step (1): Mark the tip of the shadow with a stone or a twig or by any other means. The first shadow mark is always towards the west. See after 15 minutes and mark the tip of the shadow again. By then it would have moved a few centimetres away. Now join the two points and you have an approximate east-west line. Step (2) : Stand with the first mark to your left and the second mark to your right you are now facing north. This fact is true everywhere on the earth because the earth rotates in west to east direction. An alternative method is more accurate but requires more time. Set up your shadow stick and mark the first shadow in the morning. Use a piece of string to draw a clean arc through this mark around the stick. At mid-day, the shadow will shrink or disappear. In the afternoon, it will lengthen again and at the point where it touches the arc, make a second mark. Draw a line through the two marks to get an accurate east-west line. 22 THE EARTH : OUR HABITAT  N 4 S MAPS You have learnt in the previous chapter about the advantages of a globe. However, globe has limitations as well. 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, Let’s Do districts, towns and villages, it is of little help. In such Take an old a situation we use maps. A map is a representation or rubber ball and a drawing of the earth’s surface or a part of it drawn draw whatever on a flat surface according to a scale. But it is you like all over it. You impossible to flatten a round shape completely. may also mark north We find that maps are useful to us for various pole and south pole on purposes. One map shows a small area and a few facts. it. Now cut this ball Another map may contain as many facts as a big book. with a knife and try to When many maps are put together we get an Atlas. flatten it. Notice how the Atlases are of various sizes, measurements drawn on drawings are distorted. different scales. Maps provide more information than a globe. They are of different types. Some of them are described below. PHYSICAL MAPS Maps showing natural features of the earth such as mountains, plateaus, plains, rivers, oceans etc. are called physical or relief maps. POLITICAL MAPS Maps showing cities, towns and villages, and different countries and states of the world with their boundaries are called political maps. THEMATIC MAPS Some maps focus on specific information; such as road  maps, rainfall maps, maps showing distribution of forests, industries etc. are known as thematic maps. Suitable titles are given on the basis of information provided in these maps. There are three Components of Maps – distance, direction and symbol. DISTANCE Maps are drawings, which reduce the entire world or a part of it to fit on a sheet of paper. Or we can say maps are drawn to reduced scales. But this reduction is done very carefully so that the distance between the places is real. It can only be possible when a small distance on paper represents a large distance on the ground. Therefore, a scale is chosen for this purpose. Scale is the ratio between the actual distance on the ground and the distance shown on the map. For example, the Let’s Do distance between your school and your home is 10 Look at the km. If you show this 10 km. distance by 2 cm on a Figure 4.1. map, it means, 1 cm on the map will show 5 km. on There is a scale. the ground. The scale of your drawing will be 1cm = 5 It may be used for measuring distance km. Thus, scale is very important in any map. If you between places. For know the scale, you will be able to calculate the example the distance distance between any two places on a map. between the well and the When large areas like continents or countries are tree is 5 cm. It means to be shown on a paper, then we use a small scale. For that the actual distance example 5 cm. on the map shows 500 km. of the is 50 metres. Now the ground. It is called a small scale map. distance between the PO (A) to Karim’s house (E) When a small area like your village or town is to be is 12 cm. It means 120 shown on paper, then we use a large scale that is 5 metres on the ground but cm. on the map shows 500 metres only on the ground. you can not fly like a bird It is called a large scale map. directly from E to A. You Large scale maps give more information than small will have to walk on the scale maps. road. Let us measure the total walking distance DIRECTION from E to C, then C to M, M to B and B to A. Add Most maps contain an arrow marked with the letter all these distances. This ‘N’ at the upper right hand corner. This arrow shows will be the total walking the north direction. It is called the north line. When distance from Karim’s you know the north, you can find out other directions, house to the post office. for example east, west and south. There are four major 24 THE EARTH : OUR HABITAT Figure 4.1 : Map of a village directions, North, South, East and West {Figure 4.2 (a)}. They are called cardinal points. Other four intermediate directions are north-east (NE), south- east(SE), south-west (SW) and north-west (NW). We can locate any place more accurately with the help of these intermediate directions. Figure 4.2 (a) : Cardinal Directions Find out the following directions from the Figure 4.1: (a) The direction of the Community Centre, N the playground from Vikas’s house (b) the direction of school from shops. We can find out the direction of a place with the help of a compass. It is an instrument used to find S out main directions. Its magnetic needle always points towards north-south direction {Figure 4.2 (b)}. Figure 4.2 (b) : A compass MAPS 25  SYMBOLS It is the third important component of a map. It is not possible to draw on a map the actual shape and size of different features such as buildings, roads, bridges, trees, railway lines or a well. So, they are shown by using certain letters, shades, colours, pictures and lines These symbols give a lot of information in a limited space. With the use of these symbols, maps can be drawn easily and are simple to read. Even if you don’t know the language of an area and therefore cannot ask someone for directions, you can collect information from maps with the help of these symbols. 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. Some of the conventional symbols are shown in the Figure 4.3. Figure 4.3 : Conventional Symbols Various colours are used for the same purpose. For example, generally blue is used for showing water bodies, brown for mountain, yellow for plateau and green is used for plains. 26 THE EARTH : OUR HABITAT Figure 4.4 : Sunderpur village and its surrounding areas SKETCH Look at the Figure 4.4 and A sketch is a drawing mainly based on memory and find out : spot observation and not to scale. Sometimes a rough (i) In which direction is the river flowing? drawing is required of an area to tell where a (ii) What kind of road particular place is located with respect to other passes by the side of places. Suppose, you want to go to your friend’s village Dumri? house, but you don’t know the way. Your friend may (iii) On what type of make a rough drawing to show the way to his house. railway line is Such a rough drawing is drawn without scale, and Sunderpur situated ? is called a sketch map. (iv) On which side of the railway bridge is the PLAN police station situated? A plan is a drawing of a small area on a large scale. A (v) On which side of the large-scale map gives lot of information, but there are railway line do the certain things which we may sometimes want to know following lie : for example the length and breadth of a room, which (a) Chhatri can’t be shown in a map. At that time, we can refer (b) Church (c) Pond (d) Mosque (e) River drawings drawn to scale called a plan. (f) Post and Telegraph Office Let’s Do Visit web portal School Bhuvan-NCERT and (g) Graveyard draw online neighbourhood map on satellite imageries. MAPS 27  1. Answer the following questions briefly. (a) What are the three components of a map? (b) What are the four cardinal directions? (c) What do you mean by the term ‘the scale of the map’? (d) How are maps more helpful than a globe? (e) Distinguish between a map and a plan. (f) Which map provides detailed information? (g) How do symbols help in reading maps? 2. Tick the correct answers. (a) Maps showing distribution of forests are (i) Physical map (ii) Thematic Map (iii) Political map (b) The blue colour is used for showing (i) Water bodies (ii) Mountains (iii) Plains (c) A compass is used – (i) To show symbols (ii) To find the main direction (iii) To measure distance (d) A scale is necessary (i) For a map (ii) For a sketch (iii) For symbols 1. Draw a plan of your classroom and show the teacher’s table, blackboard, desks, door and windows. 2. Draw a sketch of your school and locate the following : (a) the principal’s room (b) your classroom (c) the playground (d) the library (e) some big trees (f) drinking water 28 THE EARTH : OUR HABITAT  1. Make the plan (in the space given below) of a fun-park where you can enjoy several activities : for example swings, slides, see-saw, merry-go-round, boating, swimming, looking into funny mirrors, etc. or anything else that you can think of. MAPS 29  5 MAJOR DOMAINS OF THE EARTH As you have read in the first chapter, 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. The surface of the earth is a complex zone in which three main components of the environment meet, overlap and interact. The solid portion of the earth on which we live is called the Lithosphere. The gaseous layers that surround the earth, is the Atmosphere, Word Origin where oxygen, nitrogen, carbondioxide and other gases In the Greek are found. Water covers a very big area of the earth’s language, Lithos surface and this area is called the Hydrosphere. The means Stone; Atmos Hydrosphere comprises water in all its forms, that is, means Vapour; ice, water and water vapour. Hudor means Water; The Biosphere is the narrow zone where we find and Bios means Life. land, water and air together, which contains all forms Can you make words using of life. the above? LITHOSPHERE The solid portion of the earth is called the Lithosphere. It comprises the rocks of the earth’s crust and the thin layers of soil that contain nutrient elements which sustain organisms. 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. All the oceans of the world are connected with one another. Look at the map of the world (Figure 5.1). Are all the land masses connected with one another? The level of seawater remains the same everywhere. Elevation of land is measured from the level of the sea, which is taken as zero. MAJOR DOMAINS OF THE EARTH SOUTHERN OCEAN Figure 5.1 : The World : Continents and Oceans 31  The highest mountain peak Mt. Everest is 8,848 Do you know? metres above the sea level. The greatest depth of 11,022 Edmund Hillary metres is recorded at Mariana Trench in the Pacific (New Zealand) Ocean. Could you imagine that depth of sea is much and Tenzing Norgay more than the highest point? Sherpa (India) were the first men to climb the Continents highest mountain peak Mt. There are seven major continents. These are separated Everest on the planet by large water bodies. These continents are – Asia, earth on 29th May, 1953. Europe, Africa, North America, South America, Junko Tabei (Japan) Australia and Antarctica. Look at the map of the world was the first woman to (Figure 5.1) and notice that the greater part of the land reach the summit on 16th mass lies in the Northern Hemisphere. May, 1975. The first Asia is the largest continent. It covers about one- Indian woman to climb the highest peak on 23rd May, third of the total land area of the earth. The continent 1984 was Bachendri Pal. lies in the Eastern Hemisphere. The Tropic of Cancer passes through this continent. Asia is separated from Europe by the Ural mountains on the west (Figure 5.1). The combined landmass of Europe and Asia is called the Eurasia (Europe + Asia). Europe is much smaller than Asia. The continent lies to the west of Asia. The Arctic Circle passes through it. It is bound by water bodies on three sides. Look at the map of the world and locate it. 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. Look at the Figure 5.1; you will find that it is the only continent through which the Tropic of Cancer, the Equator and the Tropic of Capricorn pass. The Sahara Desert, the world’s largest hot desert, is located in Africa. The continent is bound on all sides by oceans and seas. Look at the world map (Figure 5.1). You will notice that the world’s longest river the Nile, flows through Africa. Notice where the Equator, the Tropic of Cancer and the Tropic of Capricorn pass in the map of Africa. North America is the third largest continent of the world. It is linked to South America by a very narrow strip of land called the Isthmus of Panama. The continent lies completely in the Northern and Western Hemisphere. Three oceans surround this continent. Can you name these oceans? 32 THE EARTH : OUR HABITAT  South America lies mostly in the Southern Hemisphere. Which two oceans surround it on the east and the west? The Andes, world’s longest mountain range, runs through its length from north to south (Figure 5.1). South America has the world’s largest river, the Amazon. Australia is the smallest continent that lies entirely in the Name the Strait Southern Hemisphere. between India It is surrounded on all and Sri Lanka. sides by the oceans and seas. It is called an Figure 5.2 : Isthmus and Strait island continent. Antarctica, completely in the Southern Hemisphere, is a huge continent. 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. 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. HYDROSPHERE The earth is called the blue planet. More than 71 per cent of the earth is covered with water and 29 per cent is with land. Hydrosphere consists of water in all its forms. As running water in oceans and rivers and in lakes, ice in glaciers, underground water and Fresh the water vapour in atmosphere, all comprise the Water hydrosphere. 2.5% More than 97% of the Earth’s water is found in the oceans and is too salty for human use. A large Oceans proportion of the rest of the water is in the form of 97.5% icesheets and glaciers or under the ground and a very small percentage is available as fresh water for human MAJOR DOMAINS OF THE EARTH 33 Figure 5.3 : Comparative size of the continents Count the squares given in Figure 5.3 and answer the following : (a) Name the largest continent; (b) Which is larger – Europe or Australia? use. Hence, despite being a ‘blue planet’ we face a shortage of water!! Oceans Oceans are the major part of hydrosphere. They are all interconnected. The ocean waters are always moving. The three chief movements of ocean waters are the waves, the tides and the ocean currents. The five major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean and the Arctic Ocean, in order of their size (Figure 5.1). The Pacific Ocean is the largest ocean. It is spread over one-third of the earth. Mariana Trench, the deepest part of the earth, lies in the Pacific Ocean. The Pacific Ocean is almost circular in shape. Asia, Australia, 34 THE EARTH : OUR HABITAT North and South Americas surround it. Look at the map and find out the location of the continents around the Pacific Ocean. 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. 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 is the only ocean named after a country, that is, India. 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 encircles the continent of Antarctica and extends northward to 60 degrees south latitude. 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. Exosphere ATMOSPHERE The earth is surrounded by a layer of gas called the atmosphere. This thin blanket of air is an integral Thermosphere 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. Mesosphere The atmosphere extends up to a height of about 1,600 kilometres. The atmosphere is divided into five layers based on composition, temperature and other properties. These layers starting from earth’s surface are called the troposphere, the stratosphere, the mesosphere, the thermosphere and the exosphere. Stratosphere The atmosphere is composed mainly of nitrogen and oxygen, which make up about 99 per cent of clean, dry air. Nitrogen 78 per cent, oxygen 21 per cent and other gases like carbondioxide, argon and others Troposphere comprise 1 per cent by volume. 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. It is also essential for the growth of plants. The density of the atmosphere varies with height. It Figure 5.4 : Layers of the Atmosphere MAJOR DOMAINS OF THE EARTH 35  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. The temperature also decreases as we go upwards. The atmosphere exerts pressure on the earth. This varies from place to place. Some areas experience high pressure Figure 5.5 : A mountaineer and some areas low pressure. Air moves from high pressure to low pressure. Moving air is known as wind. 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. There are several Figure 5.6 : The Biosphere 36 THE EARTH : OUR HABITAT species of organisms that vary in size from microbes and bacteria to huge mammals. All the living organisms including humans are linked to each other and to the biosphere for survival. The organisms in the biosphere may broadly be divided into the plant kingdom and the animal kingdom. The three domains of the earth interact with each other and affect each other in some way or the other. For example, cutting of forests for fulfilling our needs of wood, or clearing land for agriculture may lead to fast removal of soil from slopes. Similarly earth’s surface may be changed due to natural calamities like earthquakes. For example, there could be submergence of land, as happened in the case of Tsunami recently. Parts of Andaman & Nicobar islands were submerged under water. 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. There is thus, a need to limit the use of resources of the earth to maintain the balance of nature between the domains of the lithosphere, the atmosphere and the hydrosphere. 1. Answer the following questions briefly. (a) What are the four major domains of the earth? (b) Name the major continents of the earth. (c) Name the two continents that lie entirely in the Southern Hemisphere. (d) Name the different layers of atmosphere. (e) Why is the earth called the ‘blue planet’? (f) Why is the Northern Hemisphere called the Land Hemisphere? (g) Why is the Biosphere important for living organisms? MAJOR DOMAINS OF THE EARTH 37  2. Tick the correct answers. (a) The mountain range that separates Europe from Asia is (i) the Andes (ii) the Himalayas (iii) the Urals (b) The continent of North America is linked to South America by (i) an Isthmus (ii) a Strait (iii) a Canal (c) The major constituent of atmosphere by per cent is (i) Nitrogen (ii) Oxygen (iii) Carbon dioxide (d) The domain of the earth consisting of solid rocks is (i) the Atmosphere (ii) the Hydrosphere (iii) the Lithosphere (e) Which is the largest continent? (i) Africa (ii) Asia (iii) Australia 3. Fill in the blanks. (a) The deepest point on the earth is _____________ in the Pacific Ocean. (b) The _____________ Ocean is named after a country. (c) The _____________ is a narrow contact zone of land, water and air that supports life. (d) The continents of Europe and Asia together are known as _____________. (e) The highest mountain peak on the earth is _____________. 1. Cut the outline of the continents from an outline map of the world and arrange them according to their decreasing sizes. 2. Cut the outline of the continents from an outline map of the world and try to fit them together as a jig-saw puzzle. 3. Collect pictures of expeditions to the Himalayas. Write about the kind of equipment carried by the climbers for protection against sunshine, temperature and the lack of air. Map Skills 1. On the outline map of the world, mark the following : Europe, Asia, Antarctica, South America, Australia, Indian Ocean, Pacific Ocean, Atlantic Ocean, Ural Mountains and Isthmus of Panama. 38 THE EARTH : OUR HABITAT  6 MAJOR LANDFORMS OF THE EARTH You must have seen some of the landform features as Do you know? shown in the Figure 6.1 below. You will notice that the A hill is a land surface of the earth is not the same everywhere. The surface that earth has an infinite variety of landforms. Some parts rises higher than of the lithosphere may be rugged and some flat. the surrounding area. These landforms are a result of two processes. You Generally, a steep hill with will be amazed to know that the ground you are an elevation of more than 600 standing on is slowly moving. Within the earth, a metres is termed as a mountain. Name some continuous movement is taking place. The first, or the mountains with a height of internal process leads to the upliftment and sinking more than 8,000 metres. of the earth’s surface at several places. Figure 6.1 : Landforms  Let’s Do The second, or the external process is the continuous wearing down and rebuilding of the land surface. The Making of a wearing away of the earth’s surface is called erosion. Mountain : The surface is being lowered by the process of erosion and rebuilt by the process of deposition. These two 1. All you require is a pile of paper. processes are carried out by running water, ice and 2. Put the papers on wind. Broadly, we can group different landforms your table. depending on elevation and slope as mountains, 3. Push the papers plateaus and plains. from both sides by your hands. MOUNTAINS 4. The sheet will be A mountain is any natural elevation of the earth folded and rise into surface. The mountains may have a small summit and a peak. a broad base. It is considerably higher than the 5. You have made a surrounding area. Some mountains are even higher mountain! than the clouds. As you go higher, the climate becomes In the same process colder. our Himalayas and In some mountains, there are permanently frozen the Alps were formed! rivers of ice. They are called glaciers. There are some mountains you cannot see as they are under the sea. Because of harsh climate, less people live in the mountain areas. Since the slopes are steep, less land is available for farming. A Fold Mountain Crust Figure 6.2 : Fold Mountains (Himalayas) 40 THE EARTH : OUR HABITAT  Mountains may be arranged in a line known as Do you know? range. Many mountain systems consist of a series of parallel ranges extending over hundreds of kilometres. Mauna Kea The Himalayas, the Alps and the Andes are mountain (Hawaii) in the ranges of Asia, Europe and South America, respectively Pacific Ocean is an undersea mountain. It (Figure 5.1). Mountains vary in their heights and is higher than Mount shape. Everest being 10,205 There are three types of mountains- Fold metres high. Mountains, Block Mountains and the Volcanic Mountains. The Himalayan Mountains and the Alps are young fold mountains with rugged relief and high conical peaks. The Aravali range in India is one of the oldest fold mountain systems in the world. The range has considerably worn down due to the processes of erosion. The Appalachians in North America and the Ural mountains in Russia (Figure 5.1) have rounded features and low elevation. They are very old fold mountains. Block Mountains are created when large areas are broken and displaced vertically. The uplifted blocks are termed as horsts and the lowered blocks are called graben. The Rhine valley and the Vosges mountain in Europe are examples of such mountain systems. Locate them on the world map in the atlas and find out some more examples of this type of landforms. Volcanic mountains are Figure 6.3 : A Block Mountain formed due to volcanic activity. Mt.Kilimanjaro in Africa and Mt.Fujiyama in Japan are examples of such mountains. Mountains are very useful. The mountains are a storehouse of water. Many rivers have their source in the glaciers in the mountains. Reservoirs are made and the water is harnessed for the use of people. Water from the mountains is also used for irrigation and generation of hydro-electricity. The river valleys and terraces are ideal for cultivation of crops. Mountains have a rich variety of flora and fauna. The forests provide fuel, fodder, shelter and other products like MAJOR LANDFORMS OF THE EARTH 41 Figure 6.4 : A Volcanic Mountain gum, raisins, etc. Mountains provide an idyllic site for tourists. They visit the mountains for their scenic beauty. Several sports like paragliding, hang gliding, river rafting and skiing are popular in the mountains. Can you name some places in the Himalayas associated with these sports? Can you name this sport? PLATEAUS A plateau is an elevated flat land. It is a flat-topped table land standing above the surrounding area. A plateau may have one or more sides with steep slopes. The height of plateaus often varies from few hundred metres to several thousand metres. Plateaus, like mountains may be young or old. The Deccan plateau in India is one of the oldest plateaus. The East African Plateau in Kenya, Tanzania and Uganda and the Figure 6.5 : Plateau Western plateau of Australia are other examples. The Tibet plateau (Figure 5.1, p.31) 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. As a result, many of the mining areas in the world are located in the plateau areas. The 42 THE EARTH : OUR HABITAT African plateau is famous for gold and diamond mining. 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. In India, the Hundru falls in the Chhotanagpur plateau on the river Subarnarekha and the Jog falls in Karnataka are examples of such waterfalls. The lava plateaus are rich in black soil that are fertile and good for cultivation. M