Maharashtra-Board-Class-9-Geography-Textbook-in-English.pdf

 The Coordination Committee formed by GR No. Abhyas - 2116/(Pra.Kra.43/16) SD - 4 Dated 25.4.2016 has given approval to prescribe this textbook in its meeting held on 3.3.2017 GEOGRAPHY STANDARD NINE Maharashtra State Bureau of Textbook Product...

 The Coordination Committee formed by GR No. Abhyas - 2116/(Pra.Kra.43/16) SD - 4 Dated 25.4.2016 has given approval to prescribe this textbook in its meeting held on 3.3.2017 GEOGRAPHY STANDARD NINE Maharashtra State Bureau of Textbook Production and Curriculum Research, Pune. The digital textbook can be obtained through DIKSHA APP on a smartphone by using the Q. R. Code given on title page of the textbook and useful audio-visual teaching-learning material of the relevant lesson will be available through the Q. R. Code given in each lesson of this textbook.  Preface Dear Students, Welcome to Standard IX ! You have studied various terms and concepts of geography in your geography textbooks till now. It gives me immense pleasure to present to you this ninth standard geography textbook with more detailed concepts. Our earth is the only known planet in space where life exists. Various types of natural events occur on the earth. These events affect both the living and the non-living world. In Geography, it is often said that ‘a mountain doesn’t always remain a mountain.’ What does this imply? How to adapt to such things and many other issues make it necessary to study geography. You buy and use many commodities. You may understand from this textbook how these things are made, how they come to the shop, what is the main source of these things, etc. You will also learn how the human world takes shape from the interaction between human beings and nature, various human groups, cultures, society and the relation between society, economy and development. You will also understand the use of internet and its effects. It is necessary to study geography in a comprehensive manner. Use various relevant resources like maps, graphs, scales, etc. available for it. Carry out the activities mentioned in the book carefully in your schools and learn the subject well. Wish you all the best ! Pune Date : 28 April 2017 (Akshay Trutiya) (Dr Sunil Magar) Director Indian Solar Year : Maharashtra State Bureau of Textbook 8 Vaishakh, 1939 Production and Curriculum Research, Pune Sr. Area Unit Competency Statements No 1. Practical Distributional — Presenting information after analysis of thematic maps and Geography Maps using different geographical techniques. — Classifying data preparing multipurpose maps. Locating data on maps. — Finding various regions and places using geographical resources, locating on maps. Making reports. 2. Physical Internal — Researching how disasters are managed by man and how he Geography Movements responds to them. 3. Physical Extrnal — Examining the geographical factors and making hypothesis. Geography Movements 4. Physical Precipitation — Examining the information with the help of geographical tools, Geography interpreting about them and preparing maps. — Making hypothesis by observing physical factors, classifying them and explaining the causality in them. 5. Physical Properties of sea — Studying the ‘variables’ of factors, analysing and hypothesising Geography water about them. 6. General International — Finding solutions on various issues on the basis of geographical Geography Date Line information. — Giving answers about the location and extent of a region after placing a graticule on a map or an image. 7. Human Introduction to — Identifying patterns of economic interconnections and Geography Economics interdependence. — Examining distributional pattern and process of human 8. Human Trade activities. Geography — Explaining the effect of physical environment of a region on its trade and economy. 9. Human Urbanisation — Examining how human has used geographical factors in Geography estabilishing settlements, how he has been adapting to the local physical setting and revised it. 10. Human Transport and — Understanding the changes in values and awareness regarding Geography Communication environment and places affects individual behaviours. — Describing adaptation of various physical and political factors to historical events, movements of the people and environment. 11. Human Tourism — Collecting information for drawing conclusions regarding Geography various regions. — Describing how goods, services and technology connect various places in the region. — Stating hypothesis and conclusions after studying maps. — Answering questions of a region by using maps and other geographical tools.  For Teachers P To begin with, get familiar with the helps to create interest in the subject. textbook yourself. O The present book has been prepared for P Please plan carefully and independently constructivist and activity-based teaching. for the activities in each chapter. Please Please do not teach the lessons in the book do not teach without planning. by just reading them aloud. P The teaching-learning interactions, P Follow the order of the chapters as given processes and participation of all students in the contents because the concepts have is very necessary and so is your active been introduced in a graded manner to guidance. facilitate knowledge-building. P Please use the geographical teaching aids P Do not use the boxes titled ‘Do you in the school as required for the appropriate know?’ for evaluation. understanding of the subject. It is necessary P Give instructions to students regarding to use the globe, the maps of the World, using a pencil for activities in the book. India and the State, atlases, etc. P A glossary is given at the end of the book. P Though the number of chapters has been Detailed information of important reduced the number of periods required for geographical terms / concepts in the each chapter has been given a thought. chapters is given in this glossary. The Abstract concepts are difficult to follow words are given alphabetically. The words and therefore you are expected to use the included in the glossary are enclosed in given number of periods fully. Do not blue highlights in the chapters, e.g. (Thematic Maps) (Lesson 1, Page1) finish the chapter in short. This will help the students to assimilate the content P Some websites have been given for without feeling the ‘burden of learning’. reference at the end of the chapter and the P Like other social sciences, geographical glossary. Also, a list of references used is concepts too are not easy to understand. also given. You as well as the students are Major concepts of geography have a expected to use these references. These scientific base and they deal with references will surely help you to go beyond the textbook. Please bear in mind abstractions. Encourage group work, that extra reading is always helpful for learning through each other’s help, etc. understanding any subject in depth. Facilitate peer learning as much as possible by reorganizing the class structure P Use thought-provoking, activity-oriented, frequently. open-ended, multiple choice questions for P You will find that the character ‘Globee’ evaluation. Some examples are given at appears in different boxes and instructions the end of the chapters in the ‘exercises’. given in the chapters. Please ensure that it P Use QR Code given in the textbook. - For Students - The character ‘Globee’ will meet you in every chapter. Have you guessed who he is ? He will help in the various tasks you are expected to do. Try to follow his instructions.  CONTENTS Expected Number Sr.No. Chapters Area Page No. of Periods 1. Distributional Maps Practical Geography 1 08 2. Endogenetic Movements Physical Geography 9 08 3. Exogenetic Processes Part-1 Physical Geography 23 08 4. Exogenetic Processes Part-2 Physical Geography 30 08 5. Precipitation Physical Geography 41 08 6. The Properties of Sea Water Physical Geography 50 08 7. International Date Line General Geography 57 07 8. Introduction to Economics Human Geography 64 07 9. Trade Human Geography 67 08 10. Urbanisation Human Geography 75 08 11. Transport and Communication Human Geography 82 08 12. Tourism Human Geography 88 08 GLOSSARY 97 S.O.I. Note : The following foot notes are applicable : (1) © Government of India, Copyright : 2017. (2) The responsibility for the correctness of internal details rests with the publisher. (3) The territorial waters of India extend into the sea to a distance of twelve nautical miles measured from the appropriate base line. (4) The administrative headquarters of Chandigarh, Haryana and Punjab are at Chandigarh. (5) The interstate boundaries amongst Arunachal Pradesh, Assam and Meghalaya shown on these maps are as interpreted from the “North-Eastern Areas (Reorganisation) Act. 1971,” but have yet to be verified. (6) The exernal boundaries and coastlines of India agree with the Record/Master Copy certified by Survey of India. (7) The state boundaries between Uttarakhand & Uttar Pradesh, Bihar & Jharkhand and Chattisgarh & Madhya Pradesh have not been verified by the Governments concerned. (8) The spellings of names in these maps, have been taken from various sources. DISCLAIMER Note : All attempts have been made to contact copy righters (©) but we have not heard from them. We will be pleased to acknowledge the copy right holder (s) in our next edition if we learn from them. Front Cover : Landforms produced by physical processes - exfoliated rocks, Beaches, Sea cave, Columnar basalt and biological weathering because of tree roots (in the background) Back Cover : V-shaped valley, retail seller, man-made cave in hard rocks, Wholesale seller, Seif dunes.  1. Distributional Maps You have studied district, state and temperature, rainfall, population, etc. is country maps in the earlier classes in shown on the map according to the data of Environmental Studies and Geography these variables. These maps are useful to subjects. The main aim of maps is explain the distribution of these variables to show the location of a place and in the region. Such maps easily bring distribution of variables. Some maps are out the patterns of distribution. To draw prepared with special themes. Such maps distributional maps, we need statistical are called Thematic Maps. Through such data of the variables. Distribution can be maps, distribution of various variables shown in the three following ways on a in a region is shown. Distribution of map: Distributional Maps Dot method Choropleth method Isopleth method Dot method: v The distribution of physiography, water A dot map is prepared using statistical sources, transport system, etc. of a region data. While preparing dot maps, only data should be considered while placing dots gathered through counting is used. The on a map. way a variable is distributed throughout v While showing population distribution, the region, the dots are used to show its rural population is shown by dots and distribution on the map. For example, the circles are used to show urban population. population of a region, the distribution of cattle, etc. The dot method is most suitable for that To show distribution through dot method, variable which is freely scattered across the the value of a dot has to be determined. To region. do that, the lowest and the highest values of a given variable in a region are taken into Make friends with maps ! consideration. Accordingly, the number of dots are determined. Also, we need to consider In Fig. 1.1, the population distribution the size of the dot, the density of the variable map of Amravati district is given. Answer the and the scale of the map. The number of dots given questions by reading the distributional to be given for the value of variable in each map shown by dot method: sub-administrative unit needs to be decided first. The following precautions should be Ø What is the population of the Amravati taken while using the dot method for a map: town? v The size of a dot should be uniform. 1 Ø Name the place having population of 1 Ø Which part of the map shows sparse lakh on the map. distribution of population? Figure 1.1 : Dot method map Figure 1.2 (A) : Choropleth map (tints) 2 Choropleth method: shown. Read any one map in detail and In these maps, the data regarding various answer the following questions: geographical variables is shown by shades or Ø Name the Talukas having population tints of various colours. While making such density between 301 and 400 persons per maps, the data used for different variables is sq.km. obtained through various processes such as Ø What is the density of the Amravati measurement, surveying, etc. In this method, Taluka? only one value is given to one sub- administrative unit in a region. The smallest Ø Name the Talukas having population density less than 300 persons per sq.km. and the largest values of the given data of the variable are taken into consideration. After Isopleth method : that, 5-7 classes are made. Each class is You have seen contour maps and isobar assigned a tint of the same colour or black- maps in earlier classes. In these maps, the and-white patterns. The shades or the patterns distribution was shown with the help of lines become darker with the increasing values of showing equal values. When the distribution the given variable and are drawn accordingly of a variable is continuous, the isopleth on the map in the given classification. method is then used to show its distribution. In fig. 1.2 (A) and 1.2 (B), the population For example, altitude, temperature, rainfall, density maps of Amravati district using color etc. shades and black-and-white patterns are For these maps, we need to obtain Make friends with maps ! Figure 1.2 (B) : Isopleth Map (Black and White patterns) 3  Make friends with maps ! Figure 1.3 : Isopleth Map the accurate data regarding the altitude, in turn decides the difference between the temperature, rainfall, etc. of some places in lines. a region. It is assumed that the difference v Lines are drawn for the decided intervals. between the altitude or rainfall of two Locations with the same value are joined places changes at a uniform rate. The sub- by a line. administrative units are not taken into Following conclusions are drawn on the consideration here. Statistical data belongs basis of the maps prepared in such a way. to the respective places. Such data is known v If the lines are closer to each other then as point-related data. the change in the variable is steep and if Values of the variable are written on the the lines are away from each other, then it map at their respective locations. If the data is gentle. for more places is available, mapping of the v We get an idea of the natural trend of the distribution can be done more accurately. distribution of the variable with the help On the basis of this information, isopleth of this map. maps are prepared using the steps below: In fig. 1.3, the rainfall map of Amravati v By considering the highest and the lowest district is given. Read the map in detail and values of the variable, the class interval is answer the questions. decided to draw the isopleths maps which Ø In which part of the district is the rainfall more? 4 Ø In which direction is the rainfall decreasing? Ø What is the lowest value of the rainfall in the district? Make friends with maps ! Read the maps given in fig. 1.4 and 1.5 and answer the questions. Figure 1.5 : Rainfall Ø In which direction is the rainfall more in the district? Ø In which direction is the rainfall decreasing? Ø Which class shows low rainfall category in the district? Ø Which class shows high rainfall category in the district? Figure 1.4 : Density of population Ø Which method has been used in preparing this map? Ø In which direction is the density of population decreasing? Try this. Ø Name the Talukas with population density less than 200. Now we will prepare a map using dot Ø Name the Talukas having population method. Carry out the following activity. density between 200 and 400 Ü See the map of Nandurbar given in fig. Ø Name the Talukas with population 1.6 carefully. Draw it on another paper or density more than 400. tracing paper along with its taluka and Ø In which direction are the Talukas having district boundaries. higher density of population located in Ü Now see the population table given along the district? the map. On the basis of the statistical Ø Which method has been used in preparing data, decide the value of the dots this map? considering the highest and the lowest 5  Make friends with maps ! Figure 1.6 : District Nandurbar in the map in fig 1.6 Rural Population S.No. Talukas Ü Compare your dot map with other students 2011 and arrange a discussion in the class. 1. Akkalkuwa 2,15,974 Geographical field-visit 2. Akrani 1,89,661 Field visit is an important study method 3. Taloda 1,33,291 in geography. Geographical concepts 4. Shahada 3,46,352 and elements can be directly experienced 5. Nandurbar 2,56,409 through field-visits. Field-visits are 6. Nawapur 2,31,134 extremely useful for understanding the correlation between humans and values of population. For example, environment. 1 dot = 10000 people, so that you can decide how many dots to be given to each Preparations for field-visits : sub-administrative unit. Before going to the field-visit, decide Ü To draw dots of the uniform size, take the place and the purpose of visit. The a ball pen refill. Close the back end of elements which will be observed in field- the refill with cotton. Press this end on a visit should be decided. Study the location stamp-pad and draw the imprints of the map and the route map of the place to be dots wherever required. visited. Distance, transport route, means of transport and duration of field visit Ü While placing the dots, consider the should be planned ahead. With the help physiography, water sources, roads, rails, of teachers, students should prepare a taluka and district headquarters as shown questionnaire. 6  Selection of the study area : field-visit, you should try to understand the Geographical field-visit is organised local circumstances by conversing with for study of various elements. e.g. the local people. You should also ensure physical landforms, river banks, dams, that you do not harm the environment in coastal areas, tourism sites, offices any way during your visit. You should or museums related to geographical always keep a first-aid box with you for elements, villages, forest areas, etc. emergency circumstances. Elements should be selected after Report-writing : studying the local conditions and A field-report should be written on necessary permission letters have to be the basis of information obtained after obtained. the visit is complete. Use the following For a field visit, you should carry a issues to make a report. Add photographs notebook, specimen questionnaire, pen, wherever necessary: pencil, scale, tape, compass, a bag for v Introduction collecting samples, maps, camera, etc. v Location map and Route Map Precautions to be taken during field- v Physiography visit : v Climate It is very important to ensure safety v Population of ourselves and others during a field- visit. You should obey the instructions v Environmental problems and measures given by the teachers. You should not go v Land Utilization to unknown remote places alone. During v Conclusions Exercise Q 1. Give reasons why following sentences (8) Distribution of various are right or wrong: geographical elements can be (1) The main aim of distributional shown using dot method. maps is to show location. Q 2. Answer in brief. (2) In choropleth maps, only one (1) Explain the use and types of value is assigned to the distributional maps. sub-administrative unit. (2) Differentiate between choropleth (3) In choropleth maps, colours/tints and isopleths methods. do not change according to the (3) Explain with reasons the method values of the variables. which is best suited to show the (4) Choropleth maps are used to show distribution of population altitudes. in a region. (5) Isopleth maps are used to show population distribution. Q 3. Which method will you use for the (6) In dot method, every dot should following information ? have an appropriate scale. (1) Talukawise wheat production in (7) Isopleth maps are not made using the district isolines. (2) Distribution of the altitude of the land in the district. 7  (3) Distribution of domestic animals in (3) What is the population shown by the State the largest circle ? Which place is (4) The distribution of population that? density in India (5) Temperature distribution in (4) Which Taluka has the least Maharashtra State. population? Q 4. Study the population distribution map of *** Kolhapur district and answer the following questions: (1) Which method has been used to show the distribution of population in the district? (2) Explain the directionwise distribution of population from dense to sparse. 8  2. Endogenetic Movements Read the following news. Observe the photograph and answer Can you tell ? the questions. NEPAL DEVASTATED 2 BIG TREMORS 7.9 Richter Scale 11.40 am Powerful earthquake rocks Nepal, nearly 1500 killed _________ Kathmandu : 25 Apr (PTI) 6.6 Richter scale A powerful earthquake measuring 7.9 on Richter scale struck 12.19 pm Nepal today, nearly 1500 people were killed and over 1000 people were injured in the disaster. Epicenter : The quake and a series of serious aftershocks delivered a severe blow to Nepal. The tremors were also felt across Lamjung vast stretches of east and northeast India. It was also felt in ( Nepal) China, Bhutan and as far as Pakistan and Bangladesh. The earthquake with epicentre at Lamjung, around 80 kilometers northwest of Kathmandu, had its impact in several cities in Bihar, West Bengal and Uttar Pradesh. The initial report said the tremor measured 7.9-magnitude. It said the quake hit at 11:40 am local time at a shallow No of Dead : India 53, Tibet 12, Bangladesh 2 depth of 11 km. ‘‘There were 17 major aftershocks measuring over 5 in the next two and half hours,” said an ¢ Focus 11 km deep officer of the National Seismological Centre. ¢ 17 more shocks after 2 big tremors Another aftershock measuring 6.6 hit within 80 minutes ¢ Duration ranging from 30 sec to 2 min of the quake. This is the largest earthquake in Nepal after ¢ India, Bangladesh and Pakistan also experience 80 years. India has sent rescue teams immediately. tremors ¢ 22 States in India feel the tremors Figure 2.1 : Newspaper Snippet | What caused the large-scale casualities? events are disastrous. There is loss of life | What was the magnitude of the earthquake? and property because of natural calamities. In this lesson we will get introduced to these | Which country was the most affected by this earthquake? endogenetic (internal) movements. | Where was the epicenter of the earthquake? Try this. | Which are the other affected areas ? (Note for teachers: The steps in the activities are | At what depth was the focus located? important. Make sure every student participates. | What kind of damage is seen because of Lead the students to the topic through discussion.) the earthquake? Ü As shown in fig 2.2 (A), arrange your | According to you, what could be the reason notebooks on each other. Place 3-4 objects behind the earthquake? | Have you ever experienced a similar earthquake? Discuss. Various natural events occur on the earth from time to time e.g. floods, storms, snowfall extreme rainfall, etc. Similarly, because of the movements below the earth’s surface, natural events like earthquakes and volcanic eruptions occur. For the organisms living on earth, these Figure 2.2 (A) 9  like chalk, duster, sharpener, eraser, etc. Ü Now, give a slight push to this structure and on them. observe what happens. Then again give a hard push. Observe what happens. Carry out a discussion on all these activities. (See fig. 2.3 (B)) Figure 2.2 (B) Ü Now, quickly take out a notebook without affecting the others according to fig. 2.2 Figure 2.3 (B) (B). Observe what happens. Discuss in class. Geographical explanation Try this. Earthquakes and volcanoes occur because of the instability in the interior of the earth. This instability is created due to the movements Ü Arrange the notebooks and keep chalk, occurring in the earth’s interior. duster, sharpener, rubber, etc. on them as in Generally the movements in the earth’s previous step (fig. 2.3 (A)). interior occur in the upper layer of the mantle. Tremendous energy is released by radioactive materials in the mantle. These energy waves travel from one place to another. Due to such a flow of energy, instability is caused in the mantle. The movements are classified on the basis of their velocity, direction and the landforms they produced. Figure 2.3 (A) Volcano 10 Classification of internal movements : Basis of Classification Movements 1. Velocity a) Slow movements ( occurring continuously) like formation of mountains and continents b) Sudden Movements ( in the form of events) like earthquakes, volcanoes 2. Direction a) Horizontal Movements b) Upward , Downward Movements 3. Landforms a) Continent –building ( creating continents, plateaus and highlands) b) Mountain-building ( folding, faulting) Slow movements : The effect of slow movements can be Ü Move both the hands towards each other seen in the form of formation of mountains giving pressure on the strip and continents on the earth’s crust. This Ü Observe what happens to the strip. can be explained as follows: Compression Effect Pressure Tension The di- Waves moving Waves moving rection towards each away from each of wave other other move- Figure 2.5 (A) ment Effect Compression Fa on hard Fau ult rocks lt Effect ne on soft Folding pla rocks ult Fa Figure 2.5 (B) Figure 2.4 : Earth's movements and their effects Geographical explanation (a) Mountain-building movements (orogenic) : In activity 1, the strip was moved by Try this. placing hands on both ends. The work performed on the strip at that time is called Activity 1 : compression. Pressure was given on the Ü Take a 30cm long paper strip centre of the strip from both the ends. As Ü Place your hands on both the ends of a result, the strip moves and folds are the strip. formed. Similarly, due to pressure on the 11 earth’s crust, movements are generated and folds are formed. Try this. Fold mountains : Energy is transferred Activity 2 : from the interior of the earth. Because of Ü Take a long strip of thin paper. these energy waves and pressure working Ü Hold one end of the paper in your right towards each other and in horizontal hand. Hold the other in your left hand. direction, the layers of the soft rocks form Ü Pull both the ends away from each folds. If the pressure is very high, large- other. scale folds are formed and their complexity Ü Observe what happens to the paper increases. As a result, the surface of the strip. earth gets uplifted and fold mountains are formed. The Himalayas, the Aravalis, the Rockies, the Andes, the Alps are the major fold mountains of the world. See fig. 2.6 (A) and (B) and fig 2.7 Tension Figure 2.8 (A) Compression Tension Figure 2.6 (A) : Folding Figure 2.8 (B) Geographical explanation In activity 2, ‘tension’ is created when you pull both the ends away from each Figure 2.6 (B) : Folded part of a mountain other. Similarly, when movements occur in opposite direction to each other, tension is generated and ‘faults’ are formed in the earth’s crust. Block mountains : Because of internal movements, horizontal waves moving away from each other are formed. This causes tension on the layers of rocks. This leads to formation of fractures in the rocks. These are known as faults. Similarly, waves Figure 2.7 : Image of the Himalayas and adjacent coming towards each other in hard rocks areas 12 also form faults due to compression. When happens. Draw the diagram emerging a part of the earth’s crust in between two because of the notebooks in your own parallel faults is lifted, it looks like a block. notebook. Geographical explanation When horizontal movements on the earth’s surface act in opposite direction, it t causes tension on the rocks in the earth’s crust. ul When tension increases, fractures develop in Fa t ul the rocks. This leads to formation of faults. Fa Consequently, rocks on both the ends slide and the continuity in the layers of rocks is not found. Rift valleys : Sometimes, two fractures develop side-by-side in the earth’s crust. The land in between the two fractures subsides. Figure 2.9 (A) : Effect of tension - block mountain This subsided deep part is called rift valley. See fig. 2.10 ( A, B). Both the slopes of a rift See fig 2.9 (A). Such a landform is known valley are steep. For example the rift valley as a block mountain. The hilltops of block mountains are flat. In the early stages, they do not have any peaks. Their slopes are t ul t ul steep. For example, Black Forest mountains Fa Fa in Europe. The Meghalaya Plateau of India (fig 2.9 (B)) has also been formed in similar way. Figure 2.10 (A) : Rift valley Figure2.9 (B) : Meghalaya Plateau (Block mountain) Try this. Ü Take 3 notebooks of the same size. Ü Hold them on tightly on a table keeping a distance of 2-3cm. Ü Remove the two notebooks on each end away from the central one. Observe what Figure 2.10 (B) : Rift valley of Narmada 13 of river Narmada in India, The Great Rift of the earth’s surface, i.e. earthquake Valley of Africa, The Rhine River rift valley occurs. The magnitude of the earthquake of Europe. is measured by Richter scale. See fig 2.11 (b) Continent-building (Epeirogenic) Causes of earthquakes : movements : Ü Moving of the plates Slow movements occur towards the centre Ü Colliding of plates or from the earth’s centre towards the earth’s Ü Plates sliding one below the other crust. Because of these movements, a vast part Ü Forming of fractures in rock layers due of the earth’s crust is uplifted or gets subsided. to tension in the interior of the earth. When the part of the earth’s crust is uplifted Ü Occurring of volcanic eruptions (above the mean sea level,) continents are formed. Therefore, these movements are called continent-building movements. Extensive plateaus can also be formed because of such movements. If the originally continental portion of the crust subsides below the sea level, it forms a part of the sea-bed. Sudden movements : In the beginning of the chapter, we have discussed and studied the news item on earthquake. ‘Earth’ means the ground and ‘quake’ means trembling. Earthquake is the movement of the earth’s crust. You have been acquainted with the magnitude and effects of the earthquake through the activity at the beginning of the chapter itself. Now we will look at the sudden movements called P S L earthquakes and volcanoes in the earth’s interior in detail. Figure 2.11 : Simple seismogram and graph Do you know ? Do you know ? When you stand on a railway platform Indo-Australia, Africa, Eurasia, near the railway track, you experience North America, South America, Pacific trembling if a train passes by speedily. and Antarctica are seven major plates. Tremors are also felt when a heavy The earth’s crust is made up of such vehicle crosses a bridge in speed. plates. Oceans and continents are spread Through these examples, one can over these plates. Depending on the estimate the tremors caused during compression and tension formed in the earthquakes. interior of the earth, these plates move in various directions. Earthquakes : Because of the Focus and Epicenter : Because of the movements occurring in the interior of the movements occurring below the earth’s earth, tremendous tension is created in the surface, tension is created and it keeps on earth’s crust. When the tension goes accumulating. High energy is released at the beyond limits, the energy is released in the place where this tension mounts up. This is form of waves. This results in trembling the centre of the earthquake. It is called the 14 focus or hypocenter. Energy waves scatter lesser than the P waves. The particles lying in in all directions from this centre. The place the way of these waves move up and down in on the earth’s surface where these energy the direction of energy transfer. These waves waves reach first is called the epicenter of can travel only through the solid medium. the earthquake. It is the nearest place on They get absorbed as they enter the liquid the earth’s surface from the focus and it medium. The buildings on the earth’s surface experiences the first tremor. The epicenter is move up and down because of these waves. perpendicular to the focus. These are more destructive than the P waves. Earth's Epicentre (3) Surface or ‘L’ waves : These waves surface are generated after the main P and S waves reach the epicenter. They travel in the direction of the circumference of the earth Surface along the crust. They are highly destructive. s waves rimar y wa ve Seismogram : Through this instrument, a P Focus Second ary graph showing movement of seismic waves waves (Seismograph) can be generated. After studying this graph, the magnitude of the earthquake is known. Fig.2.11 shows a simple seismogram and a seismograph prepared from Figure 2.12 : Types of seismic waves it. Now with the help of modern technology, When the tension is released at the focus, advanced seismograms have been designed. the released energy travels in all directions. With their help, even micro-seismic waves This energy comes towards the earth’s surface can also be measured. in the form of waves. The seismic waves Try this. can be divided into primary, secondary and Ü Hang a heavy bag or pouch on the surface waves. See fig. 2.12 (1) Primary or ‘P’ waves : These are the hook of a spring balance as shown in first ones to reach the surface of the earth after fig 2.13 (A) Ü Pull the bag down and release it. the energy is emitted in the earth’s interior. They travel at a very fast speed from the Observe the spring and note the focus of the earthquake in radial direction. movement of spring. Subjected to a P wave, particles in the rock move in the direction of waves to and fro. The wave moves to and fro, therefore these waves are also called forward-backward waves. These waves can travel through all the three states - liquid, solid and gaseous. But while travelling through liquid medium, their direction gets changed. It is because of the primary waves that the buildings on the earth’s surface move back and forth. (2) Secondary or ‘S’ waves : The waves which reach the earth’s surface after the primary waves are called secondary waves. These waves also scatter in all directions from (A) (B) the focus of the earthquake. Their velocity is Figure 2.13 : Experiment of the weight 15 Ü As shown in fig 2.14, make the students stand holding the ends of a rope. Ask Find out. one student to give a jerk to the rope After you complete all the three activities by pulling it up and down with hand. given above compare them with each of the Observe what happens and note the seismic waves and identify which activity is movement of rope. similar to which type of wave. Effects of earthquake : v Cracks /fractures develop on the ground. v Causes landslides which leads to sliding of rocks. v Sometimes the groundwater changes its course. For example, wells may get water or may dry up. v Some areas get uplifted while some may subside. v Tsunamis are generated in oceans. These waves can cause great loss of life and property in the coastal areas. v In snow-covered areas, avalanches may occur. v Buildings collapse and loss of life and Figure 2.14 : Experiment of the rope property occurs. Ü Spread ‘rangoli’ on a large plate. Flick v Transportation routes get disrupted. on the lower side of the plate slightly v Communication system collapses. with your fingers. Observe what happens. Give it a try. 1) Collect information regarding precautions to be taken during an earthquake. Give a demonstration in the class. 2) Collect information and pictures related to advanced seismograms like the one shown in fig 2.11. Write about its working mechanism in your own words. Volcanoes : Hot solid, liquid and gaseous materials are thrown out from the mantle of the earth onto the surface of the earth. This process is called volcanic eruption. During this process, ash, water vapour, various types of poisonous and inflammable gases, hot molten magma etc. are thrown out. When the molten magma Figure 2.15 : Experiment of Rangoli comes out on the surface, it is called lava. 16  On the basis of the type of eruption, Always remember - volcanoes can be divided into following types: According to the periodicity of the volcanic (1) Central-type or conical volcano : During eruptions, three types of volcanoes can be eruption, the molten magma comes out identified: through a pipe like vent inside the earth’s v If the volcanic eruptions are regular surface. The lava spreads around the mouth of even in the present times, then such this vent when it comes out. As a result, cone- volcanoes are called active volcanoes. shaped mountains start forming and conical For example, Mt Fujiyama in Japan, Mt. volcanic mountains are formed. Mt. Fujiyama Stromboli in Mediterranean Sea. in Japan and Mt. Kilimanjaro in Tanzania v When a volcano has not erupted since are examples of central-type volcanoes and long, but may become active suddenly it is conical mountains. See fig 2.16 called dormant volcano. For example, Mt. Vesuvius in Italy, Mt. Katmai in Alaska, Barren Island, India. v Those volcanoes which have not erupted in the past since long and are not likely to erupt in the future are called extinct volcanoes. For example Mt. Kilimanjaro in Tanzania. Make friends with maps ! Read fig 2.18 and answer the questions. As a supplementary material to this exercise, Figure 2.16 : Central or Conical Volcano take help from a globe or a physical map of (2) Fissure-type volcanoes : During eruption, when the magma comes out not from a single the world. vent but from many cracks (fissures), it is Ø Examine the plate boundaries in the given called fissure-type volcanic eruption. The map and write the names of the plates. molten material coming out with the eruption Ø On which side of the continents of North spreads on both the sides of the fissure. As and South America are the earthquake- a result, volcanic plateaus are formed. The prone zones located? Which mountains Deccan Plateau of India has also been formed are located there? due to such a type of volcanic eruption. (See fig 2.17) Ø In which mountainous zone in Asia does the earthquake-prone zone lie? Ø In which region are the volcanoes concentrated in Africa? What could be the reason? Ø Correlate earthquake regions, distribution of volcanoes and plate boundaries. Geographical explanation By looking at fig 2.18 you will understand that plate boundaries are directly related to Figure 2.17 : Fissure type volcano areas of earthquakes and volcanoes. Most 17 18 Figure 2.18 : World : Earthquakes and volcanoes of the volcanoes are located on the plate boundaries. Similarly, the Do you know ? earthquake zones are also seen in the Barren Island (Andamans) : border areas. The part of the plate boundary which slides under the crust subdues. There is loss of material. Such boundaries are called plate consuming (subduction) boundaries. In areas, where new material is coming up onto the earth’s crust, they are called plate creating (constructive) boundaries. Both the processes happen continuously. They are shown in the map in fig. 2.18 Effects of volcanoes : v Loss of life and property v Sometimes tsunamis get generated due to volcanic eruptions occurring below ocean floors. Andaman and Nicobar Islands are located to v Dust, smoke, ash, gases, water the south-east of the mainland of India. On this vapour, etc. remain in the archipelago lies the Barren Island, India’s only atmosphere for a long time. This active volcano. This volcano was dormant for a may create imbalance in the long time. But, in February 2017, it started erupting. environment. Mainly dust, smoke and mud is coming out of this v Land may become fertile due to eruption along with some lava. volcanic ash. v Many minerals are found near the earth’s surface because of lava. v New land is formed due to volcanic eruption or at times, an island may even disappear. v Lakes are formed at the mouth of the craters of dead volcanoes when rain water accumulates in them. Effect of Earthquake Sahyadri : Layers of lava deposition due to volcanic eruption 19  Exercise Q 1. Tick in front of the correct option P earth’s mantle. (a) On which of the following are slow (d) Rift valley is formed because of movements in the earth’s interior faulting. dependent? Q 4. Arrange the following statements in Landforms chronological order in which an Velocity earthquake occurs. Direction (a) The earth’s surface vibrates (b) When waves divert from each (b) The plates suddenly move. other, what do they create (c) Due to the movements in the Compression mantle, compression goes on Tension increasing. Mountain (d) Along the weak points ( faultlines) (c) For the formation of a rift valley, rocks break apart. which of the following processes (e) Stored energy is released in the should occur in the earth’s crust? form of seismic waves. Compression Q 5. Distinguish between - Tension (a) Block Mountain and Fold Mountain Weathering (b) Primary and Secondary Seismic (d) Which of these is a fold mountain? Waves The Satpudas (c) Earthquakes and volcanoes The Himalayas The Western Ghats Q 6. Answer in brief (e) The formation of extensive plateaus (a) Give reasons why an earthquake is a result of which type of occurs. movements ? (b) Which type of movements have led Mountain-building to the formation of the major fold Continent-building mountains in the world? Horizontal (c) How is the magnitude of the earthquake related to the collapse Q 2. Give geographical reasons. of houses (a) Buildings collapsed at the foothills (d) What are the effects of earthquakes of the Himalayas because of on the earth’s surface and human an earthquake. Before collapsing life? they were moving forward and (e) Explain the types of seismic waves. backward. (f) Explain the types of volcanoes on (b) There is a difference in the the basis of periodicity of eruption formation of the Meghalaya with examples. Plateau and the Deccan Plateau. Q 7. Show the epicentre, focus and the (c) Most of the volcanoes are found on primary, secondary and surface waves the plate boundaries. of an earthquake with the help of a neat (d) The Barren Island is becoming labelled diagram. conical in shape. (e) Volcanic eruptions can cause Q 8. Show the following on a given outline earthquakes. map of the world. Q 3. Identify and name the internal movement. (a) Mt. Kilimanjaro (b) Mid-Atlantic Earthquake zone (a) Tsunamis are generated in coastal (c) Mt. Fuji areas. (d) Krakatoa (b) The Himalayas are an example of (e) Mt. Vesuvius fold mountains. (c) Molten magma is thrown out of the 20 21 Activity: (2) Gather information through internet (1) Make a model showing the central and about earthquakes which have occurred fissure type volcanoes. in India in the past 10 years on the basis of the following points. Magnitude Depth (In Date Time (Richter Epicentre Area affected Loss/Damage caused Kilometers) Scale) Conclusion : *** 22  3. Exogenetic Processes Part- I Many landforms are formed due to the internal movements. Many processes occurring on the earth’s surface also lead to the formation or degradation of landforms continuously. In this lesson, we will be studying the exogenetic (external) processes and the landforms formed by them. External processes occur because of the forces working on the earth’s surface. They are mainly solar energy, gravitational force and kinetic energy associated with the moving objects on the earth’s surface. Figure 3.1 (A) : Exfoliation of dome-shaped hill Do you know ? (mechanical weathering) Landforms formed on the earth’s surface as a result of internal movements are called primary and secondary landforms. For example continents, mountains, plateaus, plains, etc. Because of the external processes like weathering, erosion, transportation and deposition, the primary and secondary landforms give way to the tertiary landforms. For example, valleys, sand dunes, delta, U-shaped valleys, etc. Figure 3.1 (B) : Block disintegration Can you tell ? (mechanical weathering) See the given pictures. Observe the physical appearance of the rocks in each picture. You can see that rocks are broken, fractured and have holes in them. In a picture you can also see that the statue has been deformed. Why are the rocks in such a condition? Think about them and briefly tell the reasons you can think of. Discuss the reasons. Check with the teachers if your reasons are relevant. Figure 3.1 (C) : Shattering (mechanical weathering) 23  Figure 3.1 (G) : Chemical weathering Figure 3.1 (D) : Oxidation (Chemical weathering) Figure 3.1 (H) : Chemical weathering /salt weathering Geographical explanation Breaking or weakening of rocks Figure 3.1 (E) : Biological weathering is a natural phenomenon. It is called weathering. Weathering can be of three types: mechanical (physical), chemical and biological. In arid climates, mechanical weathering is dominant while in humid climates, chemical weathering is more effective. Biological weathering occurs because of living organisms. Mechanical weathering: Try this. Ü Take an onion. Ü Cut it in the middle. Ü Observe the cut parts. Ü Try to remove each skin layer of these Figure 3.1 (F) : Biological weathering parts. 24  Geographical explanation areas where the temperatures drop below 0o C for quite some time, the water You will notice that just as we can accumulated in the cracks and crevices remove each and every outer layer of the in the rocks freezes. Its volume increases. onion, similarly, in nature rocks undergo This leads to tension in the rocks and they such a process. The exposed part of the shatter. See fig 3.1 (C) rock heats more while the inner part is Crystal growth: In rocky coasts, waves comparatively cooler. As a result, the outer hit the sea cliff. The water is alkaline. layers of the rocks fall apart from the main Some water droplets hit the cracks in the rock. This is called exfoliation of the rock. rocks. In this alkaline water, the soluble See fig 3.2 materials in the rock get dissolved. This leads to formation of small holes in the rocks. This is the effect of solution. Alkaline water gets stored in these holes. Because of heat, this water turns into water vapor and only crystals of alkaline materials remain in the rocks. Crystals occupy more space. This causes tension in the rock. Holes are formed in the rocks. It looks like a honeycomb. See fig. 3.3 Figure 3.2 : Exfoliation Mechanical weathering mainly occurs because of the following reasons: — Temperature — Frost — Crystal growth — Release of pressure — Water Temperature: The minerals in the rocks expand because of heat and contract when temperature decreases. Due to such Figure 3.3 : Alkaline crystallization continuous contracting and expanding, Release of pressure: It is not that tension develops in the rock particles. tension is created in the rocks only Each mineral reacts differently to the because of temperature, freezing of water temperature. Some minerals expand more or crystallization. The outer layers of the while others do not expand as much. rocks exert pressure on the inner or lower Consequently, the tension formed in the layers. When this pressure ceases to exist, rocks also increases and decreases. As a the lower or inner layers get freed from result, cracks develop in the rocks and they the pressure. This also leads to weathering. break. In areas, where the diurnal range of Water: Some areas experience more temperature is higher, weathering of this rainfall than others. In such areas, soaking type is common in the hot deserts. of rock water also causes weathering of Frost: You know that the volume of some rocks like sandstone, conglomerate. the water increases when it freezes. In These rocks are formed because of pressure 25 on the agglomeration of sand particles. Mud observe what has happened to it and also makes sand particles come together. When answer the following questions: water penetrates such rocks, the particles get Ü Did the colour of the water change? loose and separate from the main rock. This is called granular weathering. See fig 3.4. Ü What happened to the chalk? 2) Wrap few iron nails in a wet cloth. Open the cloth after 2 days. Observe what happens and answer the following questions: Ü Are there any stains on the cloth? Ü Which colour are they? Ü What could be the reason for the stains? Figure 3.4 : Granular weathering Sometimes both temperature and water are responsible for weathering. Difference in temperature cause contraction and Figure 3.6 : The experiment of screws expansion widening the joints or the cracks in the rocks. Water accumulates in Geographical explanation such wide joints and big blocks of rocks separate from each other. This is called Water plays an important role in block disintegration. See fig. 3.1 (B) chemical weathering. Rock is a mixture of many minerals. Water is a universal Chemical Weathering : solvent. Many things get dissolved easily in water. The solubility increases because Try this. the matter has dissolved in water. And 1) Take a glass of water and put a those materials which do not dissolve easily piece of chalk in it. On the next day, in water get dissolved in such solutions. In areas that receive heavy rainfall, chemical weathering occurs in the following way. Carbonation : — The rainwater travels through the atmos- phere before reaching the ground. Carbon dioxide in the air gets mixed in the water in this process. Dilute carbonic acid gets formed. Materials like limestone get eas- ily dissolved in such acids. e.g Water + carbon Dioxide = Carbonic Acid (H2O + CO2 = H2CO3 ) Figure 3.5 : Experiment of chalk 26 Solution : because of the roots of the trees. As the Some minerals in the rock get roots grow bigger, they create tension in the dissolved in water. Limestone is formed rocks and start breaking them. See fig. 3.8. due to chemical precipitation between water and alkalis. At Wadgaon Darya in Ahmadnagar district, limestone gets precipitated chemically i.e. undergoes chemical weathering again. Similarly, because of solution, alkalis in the rock dissolve and make them brittle. Figure 3.8 : Biological Weathering Ants make large anthills. Rats, mice, rabbits and other worms and insects make Figure 3.7 : Stalactite in Wadgaon Darya, burrows in the ground. These animals are Ahmednagar called burrowing animals. Because of their Oxidation : This process occurs in rocks which activity, weathering of rock occurs. Besides have iron present in them. The iron in these, algae, moss, lichen, other flora etc. the rock comes in contact with water and grow in the rocks. They also help in chemical reaction takes place between iron weathering. See fig. 3.9. and oxygen. Hence, a reddish coloured layer forms on the rocks. This is called rust. When you kept nails in the wet cloth, you must have noticed a similar thing. Similar process occurs in rocks in areas with high rainfall. Fig. 3.1 (D) There are many more processes involved in chemical weathering besides the ones mentioned above. Daily-life examples include moistening of table salt in rainy season, apple slices turning brown, etc. Biological weathering : Besides mechanical and chemical Figure 3.9 : Lichen - Biological weathering weathering, biological factors are also responsible for weathering of rocks. Have you visited any fort? Have you seen trees Let’s recall. growing on their minarets? You also must Have you seen the process of biological have seen pieces of rocks getting separated weathering around you? 27 Mass movements (Mass Wasting) : The the slopes, small layers of soil accumulate weathered rock materials start moving along because of the movement of soil. This is the slopes due to gravity and accumulate called solifluction. See fig. 3.13 near the foothills or the gentler slopes. This process has been happening for years. The weathered particles form a conical heap at the foothills. When weathered particles move down due to gravity alone, the process is called mass movements. Mass movements occur in two ways: it is rapid on steeper slopes while it is slower on gentle slopes. Rapid mass movements : Rockfalls, landslides, land subsidence Figure 3.11 : Rockfall occur rapidly. Their effects are very destructive. The probability of these events is more in the regions having humid climates and steeper slopes. A thick layer of weathered material forms on the slope. When it rains in such areas, the rainwater penetrates the weathered materials and their weight increases. The weathered materials move very rapidly and come down the slope e.g., the mudslide at Malin Village of Pune district. Sometimes the weathered materials do not move downward but sink ‘in situ’ Figure 3.12 : Landslides (where they are). This is called slumping. See fig 3.10. Such rapid mass movements may also occur because of earthquakes. Figure 3.13 : Solifluction Erosion: Like weathering and mass movements, erosion is also an external process. Erosion Figure 3.10 : Slumping occurs through various agents. Wind, running Slower mass movements : water, glaciers, sea water and groundwater In areas with dry climates and gentler cause erosion. slopes, mass movements occur slowly. We will study the agents of erosion Soil creep is a common phemomenon in and the landforms produced by them in the such areas. In periglacial regions along next lesson. 28  Exercise Q 1. Answer in brief. Q 4. Identify the type of weathering from the (a) What is mechanical weathering ? given description. (b) What are the main types of chemical (a) Some animals live inside the grounds weathering? by making burrows. (c) How does biological weathering (b) The rock rusts. occur? (c) Water which has accumulated in the (d) Distinguish between weathering and crevices of the rocks freezes. mass wasting. Consequently, the rock breaks. Q 2. Write whether the statements are true or (d) The pipes supplying water in colder false. Correct the incorrect ones. regions break. (a) Climate affects earthquakes. (e) Sand formation occurs in deserts (b) Mechanical weathering is less effective Q 5. Using internet, look for incidences of a few in humid climates. landslides that have occurred in India and (c) Mechanical weathering happens on a write about them briefly. large scale in dry climates. (d) The breaking down of rocks into smaller particles is called weathering. (e) Lateritic rocks are formed through exfoliation. Q 3. Complete the flowchart below. Weathering process Chemical Weathering Burrowing by Exfoliation Oxidation animals *** 29  4. Exogenetic Processes Part –II Exogenetic processes: The slope of the land, the type of rock, We have learnt in the previous lesson volume of water flowing in the river and that the earth’s surface wears away because the length of the flow, volume of sediments of erosion. The eroded material gets carried in the river, etc, are the factors on which away by agents. When the speed of the the erosional, transportational and agent reduces, the materials get deposited. depositional work of the rivers depend. The agents like running water (river), Erosional work of rivers: glaciers, wind, sea waves and groundwater, The rivers originate at a much higher do the work of erosion, transportation and altitude from the sea level. Here, the river deposition. Because of these agents, the flows at a great speed and therefore, its earth’s surface keeps on undergoing changes power to erode is great. The riverbed and and new landforms are formed. We will the river banks get eroded because of the study some of these landforms in this fast flow of water, sand particles, pebbles. lesson. etc. and the various tributaries joining the main river. All these lead to the formation Work of rivers and landforms: of gorges (canyons), V-shaped valleys and waterfalls. Can you tell ? Transportation and deposition by rivers: A river flows down the slope from a | How will you differentiate between a hilly region. At the foothills, the change in rill, gully, stream and a river? the slope causes deposition of coarse | What is a river? sediments. As these are deposited in a Geographical explanation triangular shape, they form an alluvial fan. As the steepness of the slope decreases Running water flows naturally in a and the transporting capacity of the river direction according to gravity along the reduces, it starts flowing slowly. It bends slope and makes its own way. This is (meanders) often in its way in an effort to called a flow of water. When many such cross even small obstacles. By the time the flows of water come together, a river is river reaches the sea, its riverbed becomes formed. very wide and its speed becomes very slow. The sediments of the river get deposited in its bed and on its banks. The factors that Canyon Meandering of a river 30  Flood Flood plains plains Flood Flood levees levees River Figure 4.1 : Flood levees and flood plains determine the deposition of sediments are the length of the rivers, volume of water, amount of sediments, and the slope of the river and the earth’s surface. Thus, landforms like flood levees, flood plains and deltas are formed because of deposition of sediments. See fig. 4.1. Try to understand the formation of landforms like gorges, V-shaped valleys, waterfalls, alluvial fans, meanders, flood levees, flood plains and deltas with the ‘V’ shaped valley help of teachers. Give it a try. Some pictures of various landforms formed by the river are given. See them. Write the type of work done by the river in formation of those landforms in the box below. Delta Alluvial fans Think about it. F Many creeks are found in the coastal areas of Konkan but no delta. Why ? Find out. Is there any lake found near the meanders of the river? Obtain information Flood levees and flood plains about this. 31 Work of glaciers and landforms: Try to understand the various In regions where the temperatures are landforms produced by the work of generally below freezing point, precipitation glaciers with the help of your teachers. is in the form of snowfall. Layers of snow accumulate on the earth’s surface because Do you know ? of snowfall. The heavy weight of these Glaciers move at different velocities overlying layers makes the snow move daily ranging from 1cm to 1m. The along the slope. At the base of the layer, Jacobshavn Glacier in Greenland is one the snow starts melting because of the of the fastest moving glaciers in the friction and the pressure from above. Glacier world. It moves at the rate of 46m per starts moving slowly along the slope. day. Like the river, a glacier too carries out the work of erosion, transportation and Give it a try. deposition. Some pictures of the landforms Erosion work by glaciers: formed by glaciers are given below. Though its velocity is less, the mass of Write in the box below the function the ice is more and hence the glacier erodes because of which they have been formed. its own banks and its bed on a large scale. The erosional work of glaciers produces Horn landforms like cirques, arêtes, horns, U-shaped valleys, hanging valleys and rôche moutonnées (or sheepbacks). Transportation and deposition by Cirques glaciers : The glaciers carry sediments with them. These sediments are called moraines. Depending on the location of the deposits, moraines can be divided into 4 types: ground moraines, lateral moraines, medial moraines and terminal moraines. Observe Cirques and horn fig. 4.2.The depositional work of glacier produces landforms like drumlins, eskers, etc. Glacier bed aine al mor ater ne L o rai lm Terminal moraine a ter La Flow of the river Lat Medial moraine era lm ora ine Late ral m orai ne Figure 4.2 (A) : Moraines and their types 32  ‘U’ shaped valley Medial moraine Hanging valley Lateral moraine Lateral and Medial moraines Drumlins Eskers Can you tell ? | Where can you see the work by glaciers in India? | In which natural region can you see the work of glaciers at sea level? Rôche moutonnées Think about it. Can you see a glacier moving just Glacier as you can observe the movement of Ground moraines river water? Figure 4.2 (B) : Ground moraine 33 Work of the wind and the landforms Try to understand the various produced: landforms produced by the work of winds You have learnt earlier that the movement with the help of your teachers. of air is called wind. Wind is a gaseous agent of erosion. The erosional, transportational and depositional work of Give it a try. wind is more prominent in deserts and semi- Some pictures of landforms produced by arid regions. As mechanical weathering the work of the winds are given below. See occurs on a large scale here, powdered rock the pictures and write in the box whether they and sand spreads over a large area. There have been formed by erosion or deposition. is hardly any obstacle in the transportational work of the wind. Sand particles also get transported along with the wind and they are carried over longer distances and get deposited where the speed of the wind reduces. In this way the wind does the work of erosion, transportation and deposition. Erosional work of wind: Wind carries small sand particles, small pebbles, etc. along with it. These particles cause erosion along rocks coming in the way due to friction. This leads to formation of mushroom rocks, deflation hollows, yardangs, etc. See fig 4.3. Mushroom rock Soft Hard rocks rocks Direction of wind Figure 4.3 : Yardangs Sand dune (Barchan) Depositional work of winds: Sand partic