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CLASS IX CBSE-i L UNIT-2 GEOGRAPHY ANDFORMS STUDENTS' MANUAL Shiksha Kendra, 2, Community Centre, Preet Vihar, Delhi-110 092 India CBSE-i GEOGRAPHY LANDFORMS STUDENTS' MANUAL CLASS IX UNIT-2 Shiksha Kendra, 2, Community Centre, Preet Vihar, Delhi-110 092 India The CBSE-International is grateful for permission to reproduce and/or translate copyright material used in this publication. The acknowledgements have been included wherever appropriate and sources from where the material may be taken are duly mentioned. In case any thing has been missed out, the Board will be pleased to rectify the error at the earliest possible opportunity. All Rights of these documents are reserved. No part of this publication may be reproduced, printed or transmitted in any form without the prior permission of the CBSE-i. This material is meant for the use of schools who are a part of the CBSE-International only. Preface Education plays the most important role in acquiring professional and social skills and a positive attitude to face thechallenges of life. Curriculum is a comprehensive plan of any educational programme. It is also one of the means of bringing about qualitative improvement in an educational system. The Curriculum initiated by Central Board of Secondary Education-International (CBSE-i) is a progressive step in making the educational content responsive to global needs. It signifies the emergence of a fresh thought process in imparting a curriculum which would restore the independence of the learner to pursue the learning process in harmony with the existing personal, social and cultural ethos. The CBSE introduced the CBSE-i curriculum as a pilot project in few schools situated outside India in 2010 in classes I and IX and extended the programme to classes II, VI and X in the session 2011-12. It is going to be introduced in classes III, VII and for Senior Secondary classes with class XI in the session 2012-13. The Senior Secondary stage of education decides the course of life of any student. At this stage it becomes extremely important for students to develop the right attitude, a willingness to learn and an understanding of the world around them to be able to take right decisions for their future. The senior secondary curriculum is expected to provide necessary base for the growth of knowledge and skills and thereby enhance a student's potential to face the challenges of global competitiveness. The CBSE-i Senior Secondary Curriculum aims at developing desired professional, managerial and communication skills as per the requirement of the world of work. CBSE-i is for the current session offering curriculum in ten subjects i.e. Physics Chemistry, Biology, Accountancy, Business-Studies, Economics, Geography, ICT, English, Mathematics I and Mathematics II. Mathematics at two levels caters to the differing needs of students of pure sciences or commerce. The Curriculum has been designed to nurture multiple intelligences like linguistic or verbal intelligence, logical mathematical intelligence, spatial intelligence, sports intelligence, musical intelligence, inter-personal intelligence and intra-personal intelligence. The Core skills are the most significant aspects of a learner's holistic growth and learning curve. The objective of this part of the core of curriculum is to scaffold the learning experiences and to relate tacit knowledge with formal knowledge. This involves trans-disciplinary linkages that would form the core of the learning process. Perspectives, SEWA (Social Empowerment through Work and Action), Life Skills and Research would be the constituents of this 'Core'. The CBSE-i Curriculum evolves by building on learning experiences inside the classroom over a period of time. The Board while addressing the issues of empowerment with the help of the schools' administering this system strongly recommends that practicing teachers become skilful and lifelong learners and also transfer their learning experiences to their peers through the interactive platforms provided by the Board. The success of this curriculum depends upon its effective implementation and it is expected that the teachers will make efforts to create better facilities, develop linkages with the world of work and foster conducive environment as per recommendations made in the curriculum document. I appreciate the effort of Dr. Sadhana Parashar, Director (Training), CBSE and her team involved in the development of this document. I specially appreciate the efforts of (Late) Dr. Srijata Das for working tirelessly towards meeting deadlines. The CBSE-i website enables all stakeholders to participate in this initiative through the discussion forums. Any further suggestions on improving the portal are always welcome. Vineet Joshi Chairman, CBSE Acknowledgements Advisory Conceptual Framework Shri Vineet Joshi, Chairman, CBSE Dr. Sadhana Parashar, Director (Training), CBSE Shri G. Balasubramanian, Former Director (Acad), CBSE Ms. Abha Adams, Consultant, Step-by-Step School, Noida Dr. Sadhana Parashar, Director (Training), CBSE Ideators Dr. Anju Srivastava Ms. Varsha Seth Ms. Sarita Manuja Prof. Chand Kiran Saluja Mr. N. K. Sehgal Ms. Preeti Hans Ms. Sunita Tanwar Dr. Usha Sharma Dr. Uma Chaudhry Ms. P Rajeshwary Ms. S. Radha Mahalakshmi Ms. Renu Anand Ms. Anita Sharma Ms. Suganda Vallli Ms. Neelima Sharma Dr. Rajesh Hassija Mr. Mukesh Kumar Material Production Groups English : Ms. Gayatri Khannaa Ms. Renu Anand Ms. P. Rajeshwary Ms. Sarabjit Kaur Hindi : Ms. Sunita Joshi Ms. Babita Singh Ms. Veena Sharma Sh. Akshay Kumar Dixit Core- SEWA Ms. Vandna Ms. Nishtha Bharati Ms. Seema Bhandari Ms. Seema Chopra Ms. Madhuchhanda Ms. Reema Arora Ms. Neha Sharma Chemistry Ms. Charu Maini Ms. S. Anjum Physics: Ms. Novita Chopra Ms. Meenambika Menon Biology : Ms. Pooja Sareen Ms. Neeta Rastogi Core- Prespectives Ms. Madhuchhanda, RO(Innovation) Ms. Varsha Seth, Consultant Ms. Neha Sharma Mathematics : Dr. K.P. Chinda Dr. Ram Avtar Mr. Mahendra Shankar Mr. J.C. Nijhawan Ms. Rashmi Kathuria Ms. Reemu Verma Ms. Arti Ms. Himani Ashija Economics: Ms. Anubha Malhotra Ms. Vintee Sharma Ms. Chaitali Sengupta Core-Research Ms. Renu Anand Ms. Gayatri Khanna Dr. N. K. Sehgal Ms. Anita Sharma Ms. Rashmi Kathuria Ms. Neha Sharma Ms. Neeta Rastogi Ms. Manjushtha Bose Ms. Varsha Manku Dr. K. L. Chopra ICT: Mr. Yogesh Kumar Ms. Nancy Sehgal Ms. Purvi Srivastava Ms. Babita Mahajan Ms. Ritu Arora Ms. Swati Panhani Ms. Chanchal Chandna Geography: Ms. Meena Bharihoke Ms. Parul Tyagi Ms. Sudha Tyagi Ms. Sonia Jarul Ms. Neena Phogat Mr. Nisheeth Kumar History: Ms. Sajal Chawala Ms. Jyoti Sharma Ms. Kamma Khurana Ms. Shalini Chatarvedi Mr. Dalia Haldar Ms. Preeti Gupta Political Science: Dr. Sangeetha Mathur Ms. Ananya Roy Ms. Sunita Rathee Ms. Amarjit Kaur Ms. Nishu Sharma Ms. Manisha Anthwal Ms. Mamta Talwar Chief Co-ordinator : Ms. Kshipra Verma, EO Coordinators: Ms. S. Radha Mahalakshmi, E O Sh. R. P. Sharma Consultant (Science) Ms. Monika Munjal Gandhi (Coordinator) Mr. Navin Maini, RO (Tech) Ms. Neelima Sharma, Consultant (English) Mr. Sanjay Sachdeva, DO Shri Al Hilal Ahmed, AEO Ms. Deepa Shukla Consultant (Biology) Shri R. P. Singh, AEO Ms. Reema Arora Consultant (Chemistry) Contents 1. Meaning of Landform 1 2. Science of landforms study- Geomorphology 5 3. Agents of denudation 5 4. Cycle of erosion 6 5. Weathering Action 7 6. Landforms made by l Fluvial landforms 13 l Karst landforms 21 l Glacial landforms 25 l Sea wave landforms l Eolian landforms 31 7. Meaning of Soil 8. Soil formation 33 9. Soil texture 34 10. Factors affecting soil formation 35 11. Soil Profile 37 12. Causes of Soil Erosion 39 13. Soils Susceptible to Erosion 14. Soil erosion causes two main problems 40 15. Control of Soil Erosion 40 16. Ways to Conserve Soil 41 17. Worksheets 49 LANDFORMS Watch the video Earth – one video you need to see INTRODUCTION In the previous chapters we studied that the lithosphere is broken into a number of plates known as the Lithospheric plates. These plates move around very slowly – just a few millimeters each year. This is because of the movement of the molten magma inside the Earth. The molten magma inside the Earth moves in a circular manner. The movement of these plates causes changes on the surface of the Earth. The Earth movements are divided on the basis of the forces which cause them. The forces which act in the interior of the Earth are called as Endogenic forces and the forces that work on the Fig. 2.1 surface of the Earth are called as Exogenic forces Endogenetic forces – This force is generated in the interior of the Earth and cause Mountains, Plateaus, etc. to subside. We have no direct knowledge of the generation of these forces because the field of their activities is in the interior parts of the Earth. Some scientists think that these forces are caused by contraction of Earth on cooling, change in the rotation of the Earth or due to the action of the radioactive elements. 1 On the basis of intensity, these forces can be divided into two sub-groups: a) Sudden Endogenetic forces – The main forces in this sub-group are volcanic eruption or Earthquake. Landscape undergoes disintegration suddenly. For example, production of deep fissures in plain areas, the sudden changes in the routes of river, the formation of small hills, etc; are some of the effects of these forces. b) Diastrophic forces – These forces act very slowly. Their effect becomes discernable after thousands of years. For example, the coast of the Baltic Sea rises by 1.3 metres in a century. There are a large number of places where the coast is either rising or sinking. The landforms created by the endogenetic forces can be grouped into two divisions: a) Crustal bending – Diastrophic forces raise an area at a place. Broad domes are created in this process. The diameters of these domes range from 160 to 325 km. The rocks are at no place inclined by more than 10 or 20 from the horizontal. The process of dome-formation is known as warping. When the endogenetic forces, instead of raising the area force it down, the rocks become concave and a broad basin is formed. These basins are thus formed by a process which is opposite to dome formation. These basins are filled in by sediment. If contraction process takes place over a broad area, sedimentary rocks hundreds of meters deep are warped up. The sedimentary area thus warped up is known as Geanticlines. If warping makes a broad sedimentary area to subside down, the subsided area of the sedimentary rocks is known as Geosync-line. The sedimentary rocks when warped up or down by endogenetic or other forces form an acute angle with the horizontal. This angle is known as the Angle of Dip. Direction of dip is the direction of the greatest inclination of the bed. The line intersecting the surface of the bed and horizontal surface is known as the strike of the inclined bed. The dip is always measured at right angle to the strike. The dip angle and the strike both represent the attitude of the inclined plane. 2 Fold – When compression takes place on the crust due to endogenetic forces, a part of the crust is raised up in the form of folds. The area is contracted in this process. Due to the forces acting upon it, the crust takes a wave like form. The up-fold part is known as Anticline. The down-fold part between two Anticlines is called Syncline. Various parts of the fold – The two sides of a fold are called limbs. The fold axis passes between the limbs through the highest or the lowest part. The fold axis passing through the Anticline is called Axis of Anticline and that passing through the Syncline is called Axis of Syncline. The imaginary plane which stands in the middle of the fold and passes through the fold axis is called Axis Plane. Faults – If the blocks along the surface of fracture have significant movement, the feature is called Fault. The surface of fracture where movement takes place is called Fault plane. When the Fault plane becomes smooth on account of movement of blocks, it is called Slickenside. If the movement of blocks produces scratches on the fault plane, the scratches are known as Fault strike. A study of these scratches gives an idea of the direction of movement. Rock waste is produced by the movement of blocks. If the rockwaste has rough fragments, it is known as Fault Breccia but if it has fine particles it is called Gouge. Both of them are responsible for creating a variety of landscape which are immediately subjected to exogenetic forces. Exogenetic forces – These forces are produced and act on the surface of the Earth. Wind, water and snow are such forces which erode the surface of the Earth or make depositions on it. These external (exogenetic) forces are also called processes. The systematic study of topographic relief forms is known as Geomorphology (geoEarth; morph form; ology-science). Before learning about the evolution and geomorphic processes, it will be better to have a review and clarify some simple topographic relief forms or grouping of forms. 3 Watch the video Landforms of the world-flv Broadly there are three major landforms namely Plains, Plateaus and Mountains. A Plain is a flat surface or gently rolling with elevation not more than 200 m from the sea level. In some case it may be higher than 200 m, they are referred as high plains e.g.; Mississippi plain (USA) and Ganga plain (India) etc. A Plateau is an elevated flat or rolling land standing above from the surrounding area with at least one side by steep slope. e.g.; Arabian plateau and Tibetan plateau etc. A Mountain is a land surface higher than the surrounding area with broad base and narrow summit. The height of the mountain is a subject matter of human judgement. The Pilani hill of south India is only 1500 m when compared with mighty Himalayas which are standing as high as 6000 m and above, while the white mountains of New England (USA) is even lower than Pilani hills of India. Evolution of landforms Prof. William Morris Davis (1850-1934 AD) (Harvard University) around 1890 AD proposed the systematic study of landforms, according to their origin and stage of development. He propounded that as the surface uplift agents of denudation start working on it to bring it down up to the base level. The base level is the point up to which erosion is possible. In general the base level is sea level because all erosions activities can be done till the sea level. Below sea level only depositional activities can take place. His idea that different landforms are largely explainable in terms of differences in geological structure, geomorphic processes and stages of development of landforms. 4 Some Fundamental Concepts of geomorphic cycle: 1. The same Physical processes and law that operate today must have been operated throughout Geological time, although not necessarily always with the same intensity as now. 2. Geological structure is a dominant controlling factor in the evolution of landforms and is reflected in them. 3. To a large degree the Earth’s surface possesses relief because the Geomorphic processes operate at differential rate. 4. Geomorphic processes leave their distinctive imprint upon landforms and each Geomorphic process develops its own characteristic assemblage of landforms. 5. As the different erosional agents act upon the Earth’s surface, they produced an orderly sequence of landforms. 6. Complexity of geomorphic evolution is more common than simplicity. 7. Little of the topography is older than tertiary and most of it no older than Pleistocene. 8. Proper interpretation of present day landscapes is impossible without a full appreciation of the manifold influences of the geologic and climatic changes during the Pleistocene. 9. An appreciation of world climates is necessary for a proper understanding of the varying importance of the different geomorphic processes. 10. Geomorphology, although concerned primarily with present day landscapes, attains its maximum usefulness by historical extension. The surface of the Earth is made up of rocks and soil particles and all landforms is combined product of one or more land sculpturing forces such as running water (run off) and ground water, sea waves, moving glaciers and blowing winds on the rocks and soil. 5 All the agents of Denudation have the same object; to bring the elevated surface up to the base level of erosion i.e.;; the sea level. Denudation creates different types of landforms involving Weathering, mass wasting, and Erosion etc; Denudation is the process of levelling of the Earth surface by cutting form higher regions and depositing the sediments in depressions. Weathering is the process of decomposing and disintegrating of Earth surface (rocks) due to exposure at or near the Earth surface. It changes hard rock into fine fragments and soft residual masses. Mass wasting is Earth and rock movement due to sliding, rolling, flowing or creeping down from slopes under the influence of gravity. Erosion is the wearing away of the top layer of the Earth’s surface by different agents of denudation e.g.; running water, blowing wind, moving glacier; etc. Note: Mass wasting and erosion have almost similar connotation. Different geologist and geographer consider it differently. 6 Deposition is the process of settling down of sediments. Source: http://pubs.usgs.gov Weathering can take place without subsequent erosion and erosion is possible without previous weathering. It is to be noted here that weathering is a preparatory process that makes erosion easier but it is not prerequisite to nor necessarily followed by erosion. Conditioning factors of weathering There are four factors influence the type and rate of rock weathering. These are rock structure, climate, topography Source: http://pubs.usgs.gov and vegetation. Rock structure is used in the broad sense to include the many physical and chemical characteristics of rocks. It includes Mineralogical compositions as well as such Physical features as joints, bedding planes, faults and minute intergrain fractures and voids. The Minerals forming the rock in part determine whether it is more susceptible to chemical or physical weathering. Physical features such as joints, lesser 7 fractures, bedding lanes and faults to a large degree determine the ease with which moisture enters the rock. The major Climatic Factors of temperature and humidity determine not only the rate at which weathering proceeds but also whether chemical or physical processes predominate. Topography affects the amount of rock exposure and also has important effects upon such factors as the amount and kind of precipitation, temperature and indirectly the kind and amount of vegetation. The abundance and type of vegetation influences the rate and type of weathering by determining the extent of rock outcrops and the amount of decaying organic matter from which carbon dioxide and humic acids may be derived. Weathering process can be divided into two large groups as Physical Weathering or Mechanical weathering and Chemical weathering. Physical weathering Physical weathering is the process of disintegration of rocks into fine particles from massive rock by the exertion of stresses sufficient to fracture the rock, but do not change its chemical composition. It is most common in sub-tropical and mid-latitude regions where diurnal range of temperature is quite high. They are of different types: 8 Granular disintegration – It is process in which rocks are disintegrated into small particles due to alternate expansion and contraction during day and night. Exfoliation: In this process rocks get disintegrated in the form of layer from top to bottom. Block disintegration: When rocks are disintegrated in the form of blocks, it is called as block disintegration. Shattering: it is a type of disintegration in which rocks are broken into small pieces with angle and sharp corners edges. Organic: plants and trees sometimes put pressure on the surface of the rock and that break it into small pieces. Chemical weathering Chemical weathering is the decomposition of soil and rock (change in composition) by chemical processes. The chief Chemical weathering processes are hydration, hydrolysis, oxidation, carbonation and solution. In general, it is probably true that Chemical Weathering is more important than Physical Weathering. This may be true even in arid 9 regions, although the more advanced chemical weathering processes are not significant there. It is most common in warm and humid regions of the world. When water fall on the surface they react with chemical present in the soil and produce different types of landforms. The principle of mineral stability must be understood to appreciate fully the persistence of certain minerals in nature. In general, the least stable minerals are at the top of the surface while the most stable are at the bottom. Watch the video Weathering and erosion Fluvial action Among all agents of Denudation river is the most active. Water running on the slopes flows into gullies or irregularities in the surface of the ground. The gullies join up and form small streams. Erosion begins with the birth of every stream. Rivers erode sediments from higher regions and deposit it in lower areas while it flows from origin to its mouth. There are mainly three activities involved in Landform creation namely Erosion, Transportation and Deposition. Erosion by a stream is the progressive removal of mineral material from the sides and floor of the river channel. Transportation consists of movement of the eroded particles by dragging along the bed by suspension in the water. Deposition is accumulation of transported particles on the floor of stagnant water body into which the rivers drain their water. 10 Corrasion – A stream always follows the shortest and easiest path downhill. On the steep slopes running water moves quickly and can rapidly deepen the channel and remove rock fragments. The force of the current tears and rubs of pieces of soil and particles of rock as it rushes over them. It also uses tools to help it. It drags and rolls along stones which knock against one another and against the sides and bottom of the valley. The power of the flushing water is sufficient to pull apart the loose materials room the bed of the streams. This kind of mechanical erosion is known as Corrasion. Pot holing is a special case of corrasive action. This usually happens at the foot of a waterfall. Hollows occur in the channel and create whirlpools which suck in sand and pebbles, whirling them round in the potholes. When several pot holes from close to one another the rock walls separating them are finally worn away and the bed of the river is further lowered. Hydraulic action: the pressure of running water also causes considerable amount of erosion. Loosely joined blocks of rocks may be removed by mere pressure of the currents flowing against them. Solution: Small amount of carbon dioxide and oxygen found in all water in nature, increase the solubility of rocks and minerals. Limestone, for instance, is eroded easily by water that is charged with carbon dioxide. Stream transportation Streams carry its loads in three principle form i.e.; Dissolved matter is transported invisibly in the form of chemical ions. Suspended load are those particles that remain hanging and flow in turbulent eddies in the stream. Bed load are those heavy particles that settle down on the river bed and they roll or slide on the river bed. 11 The maximum quantity or load of sediments that river can carry is called carrying capacity of a stream. Load carrying capacity of stream is directly proportional to the stream’s velocity. When the Velocity will be high then its load carrying capacity will be increased and vice versa. So when stream is in mountain stage their velocity is high while near the mouth of river it becomes slow. In plain area it is in the state of equilibrium. 12 The work of rivers If a typical stream from its source to its mouth is followed then three visible sections can be seen: (1) The Upper Mountain Course, where the main work is that of erosion. (2) The Middle Plain Course, where the main work consists of the transportation of the material eroded. There is also some amount of deposition. (3) The Lower Delta Course, where deposition of the transported material is the main work. Source: http://cronodon.com/files/River_Processes 13 Source: http://cronodon.com/files/River_Processes Fluvial Landforms 14 The upper course The source of rivers is generally in hilly or mountainous areas. Here the volume of water is small but its flow is very fast. The young streams, therefore, rapidly erode a channel through the rocks. If the down cutting is very rapid or if the rock is very hard to wear out, a steep sided Gorge may be formed. A canyon is similar to a gorge but it is much greater in size. The most famous canyon in the world is the grand canyon of Colorado River in the United States. Gorges and canyons present some of the world’s spectacular scenic wonders. Sometimes big pieces of rock fall into it which cause temporary damming of the stream. Rivers which sweep down from steep mountain valleys on to comparatively level lands drop their load of coarse sands and gravel as there is sudden decrease in velocity. The load generally assumes a fan shape; hence it is called an Alluvial Fan. In some respects the alluvial fans are like deltas. The main difference is that whereas deltas are laid down in the sea or lakes, alluvial fans are formed at the foot of the hills. The alluvial fan sometimes grows till many kilometres across and several fans together when united they form a continuous plain known as a Piedmont Alluvial Plain. Alluvial fans and plains are generally of great agricultural value as their soils are fertile and easy to irrigate as plenty of water is available in nearby area. When a stream rushes over a steep slope in its bed it forms Rapid. They are often due to layers of hard rocks jutting out above the regular surface. Bigger rapids are called Cataract. 15 When a stream plunges down a very deep slope or over a cliff, it forms a Waterfall. Source: http://cronodon.com/files/River_Processes 16 Source: www.oup.com/pdf/oxed/geog The middle course The second stage begins when the river leaves the mountains to enter a low lying region. At this stage the volume of water has increased as the catchment area (the areas drained by a single river system) has also been increased. Some more tributaries also join the main river. In order to cope up with the increased volume of water the river has to widen its valley. The lateral corrosion tends to replace vertical Corrasion. In this processes any interlocking spurs that project from both sides of the valleys are then worn away, as the water exerts its greater force and pressure on them. The material eroded from the valley sides is then deposited on the valley floor to from a flood plain, i.e.; that part of the river valley which is covered by water during flood. Flood is temporary inundation of dry land caused due to spilling of water from river’s bank. 17 As more and more material is deposited on the bed of the river the normal level of water rises and deposition occurs on the banks which are also raised until they form broad ridges, called natural levees, on the both sides of the river. The level of the river bed is then raised above the level of the surrounding plain. Artificial embankments are often built in order to lessen the risk of flooding. When there are excessive floods the embankments gives way, the river water invades the adjacent plains, resulting in great loss of life and property. When the course of a river lies in a flat country, it swings from side to side in wide loops and Meanders. The derived from forms name the is river Meander of Asia Minor which in its lower course runs through a twisting course. The current flows faster at the outside of a bend where the bank is worn away while on the inside of the bend solid material is deposited. Ultimately the meanders may form a 18 complete circle. An interesting type of lake known as Cut-off or Oxbow lake is formed when a meandering river cuts across the narrow neck of land between the two stretches, and leaves back water. When silt is deposited at the entrance to this backwater it becomes a lake. Oxbow lakes gradually fill up with clay and silt. Sometimes due to dead flatness of the surface streams, deposit their load within the stream and Riverine Island are formed. This typical feature is called as Braided channel. The lower course In the lower course the main work is the deposition of material transported to form a Delta. Before draining the water into the sea or ocean, streams deposit their load in their path and block their mouth. When the mouth is blocked up, the level of the river rises and the water is unable to find its way directly towards the sea. This water then runs from the main stream and flows into several channels. Each of these channels is called a distributary. The distributaries wander over the delta plain forming a network of channels resembling the fingers of a hand spread out toward the sea. The whole area gets almost triangular in shape which is made up of fine soil sediment is termed as Delta. Delta is taken from Greek letter from which Herodotus in the 5th century BC coined the term for the river Nile. Deltaic plain deposits consist of alternating clay and salty clays which locally are sandy. Deltas are different in size, shape, growth and 19 importance. Every river does not make Delta. There may be no delta if the last course of river is very swift as it carries little or no alluvium up to the sea or the sea near the coast is very deep. Tidal current at the mouth of the river can also wash away the silt. If there are larger lakes in the course of a river much of the sediment is removed before the river reaches the sea. Many of the rivers emptying into seas have no deltas, but instead they have the shape of a gradually widening bay cutting deep inland. Such a bay is called an Estuary. The formation of estuaries is often due to the scouring action of tides and ocean currents. Non silted Estuaries are an excellent site for the river port. Drainage pattern Almost all steams follow some branching pattern as they do on receiving tributaries which are joined by still smaller tributaries, these patterns depends upon: (1) Differences in the slope of the land upon which the drainage system developed. (2) Differences in the resistance of the underlying rocks to erosion. 20 The three stages in the life of a river An observation of a river valley shows that in the course of development it has passed through a life cycle of Youth, Maturity and Old age. Each of these stages can be traced separately, for each has its characteristics. But the word ‘Young’, ‘Mature’, ‘Old’ are not used in terms of years. They refer to the stages in the course of the development of the landmass through which a river passes. Any projecting spurs are cut back so that the 21 level ground bordering the river is constantly widened. In course of time (Several centuries) the whole hilly area in its basin may be converted into a gently rolling plain which is slightly above the sea level. The word peneplain [meaning ‘almost a plain’] is used to describe the very low relief thus produced in the old age stage in the cycle of erosion. Youth stage: Streams that have just entered upon their work of erosion and still have rather steep gradients are called young streams. A Young stream is a powerful agent of erosion with abrupt changes in gradient. The valley show V shaped cross sections. Its Tributaries are short, and many rivers have a torrential course with narrow ravines, steep walled canyons, rapids and waterfalls. Young rivers with their rapids and waterfalls are not suitable for navigation, but they are useful for hydroelectricity. Maturity: A mature valley is wider. It has a broad flood plain and a slight gradient. It swings from side to side and the work of widening becomes more rapid than that of deepening. The valley floor becomes flat and does not have the narrow V shaped cross section characteristic of a young stream. A mature river may have several well developed Tributaries. When there are exceptionally high floods the river may abandon its natural channel and spread out over the valley floor. When the flood recedes it may leave behind a layer of silt and sand. These layers left behind after successive floods form fertile soil Old age: In this stage the water flows sluggishly and there are numerous meandering streams. There are no waterfalls, no rapids. The valley becomes broad and shallow; and the work of erosion comes almost to a standstill. Tributaries are few and large and the deposits are fine in texture. The heaviest deposition occurs at the mouth of the river where, if the conditions are favourable, a delta is formed. 22 Watch the video The journey of a river from source to mouth Karst Landforms Of the entire world’s water only about six tenths of one percent is found underground. Well developed Karst topography is found in Greek, Yugoslavia and neighbouring countries. This water is stored in aquifer below the Earth surface. Water saturated zone of rocks are called Groundwater. The upper limit of groundwater is called the Water table. Groundwater is an important erosional agent. The powerful dissolvent agent makes several interesting features. The action of groundwater is most active in limestone or calcareous cement areas. Rain water when get mixed with atmospheric sulphur dioxide and carbon dioxide and fall on the limestone area, which actively erodes the surface. 23 The underground water does not flow like river water. The following are the causes of motion of underground water: (a) Porosity of rocks: The amount of water that is locked up in rock depends upon the porosity of the rocks. The ratio of the total volume of the open spaces in rocks to the total volume of the rocks is called porosity of the rocks. This porosity depends upon the size, arrangement, closeness and compactness of the rock. The seeping water dissolves the salts of the rocks and increases their porosity. (b) Permeability of rocks: It is the ability of the water to flow through rocks. Some rocks allow more flow of water than others. This capacity of rocks to transmit water through them is known as permeability of rocks. The absence of pores rocks do not allow water to transmit. When sediments get deposited in the pores then the rock becomes impermeable. 24 Erosional features Clints, grikes and limestone pavement In areas of limestone with steep slope rainwater runs down the slope in the form of rills. Due to continuous erosion the rills get enlarged making the surface into a series of ridges and trenches. The ridges are called Clints or Lapies while the trenches are called Grikes. The region is called limestone pavement. It is difficult to walk barefoot on limestone pavement as clints are sharp pointed. Sinkholes swallow holes and blind valley Stagnant water in limestone region dissolves the surface and form a funnel shaped depression. These funnel shaped depressions are called Sinkholes. Large sinkholes are 25 called Swallow Holes. When a large cavity is from under swallow holes the roof collapses and resembles a valley. Such a valley is called Blind Valley as no river flow through it. Underground features Underground streams: When river enters in limestone region it dissolves the surface and flows underground for several kilometres, it is known as underground stream. After some distance the river reappears on the surface as non-permeable rocks do not allow water to seep downwards and force it to flow upwards. Caverns In limestone rich area groundwater dissolves weak joints. With the passage of time the dissolving process slowly enlarges into a cavity which further converts into caverns. 26 The dissolved material is carried away and discharged into streams. Caverns are enlarged form of caves. These are sometimes as big as football ground. Caverns are often connected through underground passages. Stalactites and stalagmites These are the most magnificent feature of karst topography. When limestone solvent drips from the cave ceiling, trace amount of limestone is deposited at the point of precipitation. The dripped solvent water still has trace amount of calcium carbonate which it deposits just below the ceiling hanging. Ceiling hanging column is called stalactite and column on the floor is called stalagmite. Stalactites develop ground wards while stalagmites grow upwards. When stalactites and stalagmites meet with each other, the resultant feature is called cave pillar. Cave pillar can also be formed by either growing of stalactites and stalagmites towards ground and roof respectively. Watch the video How are caves formed? Glacial Action Glaciers are slow moving river of crystalline ice masses found in high latitude and altitude areas. In cold regions snowfall ice gets accumulated and compacted due to weight of layers of snow. The snow at the bottom get compressed and crystallized into dense ice called as Firn or Nave. Types of glaciers Glaciers are grouped into two types namely Continental Glaciers Valley/Mountain/Alpine glaciers 27 As the name suggests itself, very vast expansion of thick layer of ice on a flat surface are called Continental Glacier. Greenland and Antarctica have continental type of glaciers. These glaciers move in all directions with one or many centres. When small peaks peep out of the continental glaciers surface they are called as Nunatkas. While reaching at the shore big pieces of snow block get detached with the glacier and float in sea or ocean. The floating ice blocks are called ice bergs. These ice bergs are quite dangerous for the movement of ships as only one ninth of the ice berg remains above the water level while remaining nine tenth remains submerged in water. Some of the ice bergs are kilometers in length and breadth with several meters in height. A very massive size of floating ice bergs are called as ice shelves. Mountain glaciers are tongue shaped. When these glaciers descend on the mountain slope and reach below the snow line they start melting. Rivers are formed due to melting of glacier snow. When several glaciers meet together at the foothills they are termed as Piedmont glacier. When these glacier move, they carve out several interesting features with their actions. Glacial Landforms Erosional features Bowl shaped depression with steep wall on three sides and down valley side opening feature is called Cirque. It resembles like an arm chair. Advancing glacier on the vertical wall develops deep crevasse (crack) these are termed as Bergschrund. During summer snow melts and leaves behind a small lake at the bottom of cirque. These lakes are called Tarn. Col: When two cirques are formed back to back (common head wall) the feature made is termed as a col. Arêtes and Matter horns: Sharp edged ridges are called arêtes. They resemble a knife. The summits are free from ice as they are very narrow and due to frost action ice rolls 28 down immediately. A pyramid shaped arêtes edged peak and cirques surrounding it from all directions is called Horn or Matter Horn. Hanging valleys: Hanging valleys are formed at the confluence points of the main glacier and its tributary glacier. As the base level of main glacier and tributaries glaciers are different, so the tributary glacier valley seems to be hanging above the main valley. After glaciations a waterfall takes the place at the confluence point of the main and tributary glacier. Roche Moutannee: These are small streamlined hills on the rocky surface. They are formed by the glacial abrasion on the smooth front side of the hill while steeps are formed on the opposite side due to plucking action of advancing ice. Here the teacher can ask how a layman can identify the direction of advancement of glacier by seeing the Roche Moutannee. 29 Depositional Features Glaciers make several interesting landforms by their depositional activities. Most of the features are made by Tills. Tills are the rock debris fallen into glaciers. The rock debris that falls into the glacier along the margin forms a lateral pattern of unsorted rock debris. This lateral pattern is called Lateral Moraine. When two glaciers coalesce to form a single glacier, the till that was carried along the edges of each glacier joins to form a single dark strip of debris within the newly enlarged glacier, the joint till strip is called as Medial Moraine. At the snowline the glaciers melts and deposit tills in convex arc form. This convex shaped till deposit is termed as Terminal Moraine. Sometimes when glacier ablation exceeds the nourishment, they recede. The receding enables the glacier to make a new terminal moraine. When this process continues for several times then a rolling layer of till is laid down, this is termed as Ground Moraine. Fluvio-glacial deposits Fine clay formed by rolling tills in glaciers is called Boulder clay. When boulder clay get deposited on whale back shaped elongated hills of low height they are called 30 Drumlins. Drumlins have steep slope facing the snow while elongated tail is in the direction of advancement of glacier. When boulder clay gets deposited in a vast area they form Outwash Plain. Sometimes boulder clay is deposited in the form of small mound known as kame. Small depressions in outwash plains are called Kettles. Eskers are another interesting feature made by melted glacier water. They are long, narrow and sinuous ridge composed of gravels and sand. Watch the video Glaciers and glacial landforms 31 Sea waves landforms Sea waves are the most active agent of landform creation in coastal areas. Continuous splash of sea water shapes the coastline. This splash of sea water cause several types of action in coastal region. Know more Sea waves action Most of the landform in coastal areas is formed due to several types of actions. Some of them are Hydraulic action: it includes the picking up of loose materials by waves and shattering of rocks as wave crashes against the cliffs. Corrasion: sea waves are armed with rocks debris and gravels. When the splash of water falls on coastal rocks they hurl them. The material is then eroded by sea waves back into the sea. Corrosion: it is the solvent action of the sea water. Disintegration of rocks takes place due to chemical action. This is limited to regions of limestone and rocks with calcareous cement deposits. Attrition: due to constantly to and fro moving water rock fragments worn themselves and the cliffs. It produces fine sand particles. Coastal erosion features Capes and bays: When alternate hard and soft rocks are found near coast, the soft rock is worn away by waves while the hard rock remains resistant of erosion. Due to wearing away of soft rocks sea inlets are formed. These sea inlets are called bays while the protruding hard resistant rocks are called capes. 32 Sea cliff: Sea cliffs are bench like features with almost vertical wall and wide flat platform in front. In areas of high land, sea waves erode the coastal rock between the region of high tide and low tide. As the cliff recedes a flat platform is made in front of cliff known as Wave Cut Platform. Sea Caves, sea arches, sea stacks and stumps When waves wear away the softer and highly fractured rocks located at the shore it forms sea cave. When two sea caves on opposite sides of a common shore-land rock gets united they form Sea Arch. Sometimes the roof of arch collapses and an isolated remnant pillar like structure is left behind. This rock pillar is called as Sea Stack. The worn down sea stack which is visible during low tides only are called stumps. Blow holes: When water splashes against sea cave, they trap the air inside the cave by blocking the mouth. The compressed air exerts pressure on the rock and weakens the roof of the cave. Continuous action leads to formation of hole in the roof of the cave. The formed feature is called Blow Hole which whistles at the time of splashing water at the cave mouth. 33 Coastal depositional features Sea Beaches Features of Coastal erosion Beaches They are formed by deposition of sand, gravels, pebbles and marine organism shells laid down along the coast. Beaches made up of gravels and pebbles are called Shingle Beaches while beaches made up of sand are called Sandy Beaches. Spits: Spits are long slender sandbars deposited by sea waves. They are connected with the mainland from one side while another side ends into open water of sea. When another spit develops from the main one towards the mainland, they are called Hook or Hooked Spit. Tombolo: Tombolo is sandbar connecting an island with the main land. Lagoon: Lagoon is an enclosed water body. When sandbar develops along the coast and encloses the sea water leaving a small inlet through which water can move in or out is called lagoon. Eolian Landforms Eolian landforms are made by the action of wind in arid [dry] regions of the world. Strong winds are quite common in arid and semi arid regions of the world. Strong wind 34 picks up sand particles from one place to another and while transporting and deposition they make several interesting landforms. Know more Action of wind There are three main types of action which are responsible for landforms creation. Abrasion or Corrasion: Strong winds lift sand particles and blast sand particles on stones or rocks lying in their path. Blasting of sand particles cause scooping out of rock. Deflation: the process of lifting and removal of loose material from the Earth’s surface. Attrition: the mutual wearing of sand particles is called attrition. Erosional features Ventrifacts: Multifaceted, sharp edged pebbles are called Ventrifacts. These are made by mechanical weathering by wind. Stone with three facets is called Dreikanter. Blowout: In scanty vegetation and loose soil area, strong winds deflate the loose particles. The removal of sand particles happens until it reaches the saturated groundwater soil. Deflation gets restricted due to cohesive sand particles. Mushroom rock: In arid regions strong winds carry heavy load near surface called as Bed Load. These bed loads moves by skipping or bouncing on the surface –termed as Saltation. Light weight particles remains in suspension in air and they are called Suspended Load. As the bed loads are bigger in size they abrade and scoop out rocks more near the surface. The suspended load which are lighter they do not scoop that much. Result of two, rocks in arid area get shaped as mushroom and termed as Mushroom Rock or Rock Pedestals or Gour. 35 Yardangs: These are found in areas where hard and soft rocks are found in alternative vertical bands parallel to the direction of wind. Strong winds wear away soft rocks leaving behind hard rocks. It results into formation of ridged landscape or furrow called as yardangs. Inselberg: Inselberg is controversial landform of arid region as few such similar structures are seen in glacial areas. These are conical or dome shaped isolated rocky hills. They are mostly made up of hard rocks like granite and gneiss etc. Depositional features The most interesting landform created by sand deposition is sand dune. Sand dune is a heap of sand made by wind. These can be formed into many shapes. A clump of grass or a thorny shrub obstructs wind carrying sand and forces them to settle down. Slowly gradually continuous deposition of sand makes sand dune. Sand Dunes 36 Sometimes wind elongates the margins of sand dunes in the direction of wind which gives it a crescent shape. These crescent shaped dunes are called Barchans. Due to continuous blowing of wind in one direction for long period of time either of the horn gets extended. The elongated dunes are called Longitudinal Dunes or Seif Dunes. The slope facing the wind is gentle in slope while the leeward side is steep. By saltation, strong winds roll the grain particles which are deposited on leeward side. Due to continuous saltation sand dunes moves from one place to other but these movements are quite slow. Loess: Loess are made by deposition of very fine sand and dust particles blown from one place and settled at distant place. The most extensive loess deposit is seen in North West china named as Loess Plain. The Hwang-ho River flows through loess plain and cut deep gorge. Watch the video The beauty of planet Earth (HD Quality) Soil and its formation The brown loose grainy particle that covers most of the Earth’s land surface is called Soil. It determines the food habit, clothing and housing of the population and many more. Soil formation is a dynamic phenomenon. The layer of soil itself is dynamic in which many complex chemical physical and biological activities go on simultaneously. 37 Soil is made up of substance existing in three states Solid, Liquid and Gaseous. There should be proper balance of all three for proper growth of plants. The solid portion of soil consists of both Inorganic and Organic material. Weathering of rocks produces the inorganic material while the organic material consists of living and decayed plant and animal matters. The chief organic product is a Complex brown jelly like substances known as Humus. Humus makes the soil fertile by increasing the moisture retention capacity. The liquid portion of soil is a complex solution of chemical compounds necessary for many activities that happens in the soil. Without water there will be no chemical reaction nor can it support any type of life. Gass in the pore spaces between soil grains are the third fundamental component. They are the principal gases of the atmosphere. Gases help in aeration of the soil, which increases the fertility of the soil. Watch the video Soil and Soil Profile 38 Soil texture: Soil texture means the particle size that makes the soil. Particles are classified as various grades of Gravel particles 1mm to 2 mm in diameter, Sand particles 1 mm to 0.05 mm in diameter, Silt particles 0.05mm to 0.005 mm in diameter and Clay particles less than 0.005mm in diameter. The Bureau of Soils of the US Department of Agriculture describes various soil textures as follows: Sand – 80% or more sand and 20% of less silt or clay. Sandy loam – more than 20% but less than 50% silt and clay while remaining sand. Loam – 20% clay, 30-50 % silt and 30-50 % of sand. (Silt loam if silt predominates or clay loam if clay predominates). Clay- contains 80% or more clay and silt, 10-20 % of sand. Soil texture is important to determine the water retaining capacity of the soil. Too grainy soil will drain the water while the clay soil particles are so small that they do not allow water to percolate easily. 39 Video to be shown to students. Click on the link to play the video Watch the video Soil Texture by feel Factors affecting soil formation There are many processes and influences that are involved in the formation of soil which are together known as soil formers. Some of these are passive conditions while other is active agents. There are five principal soil formers: Parent material or rock Topography or relief Passive agents Time Climate Active agents Biological activities Parent rock or material determines which type of rocks will be formed in which region. Residual or transported disintegrated rock material makes the bulk of the soil. In the case of transported soil different type of parent rocks can contribute for the formation of soil. New soil or In Situ is made up of residual parent material soil. Black soil is an example of residual parent rock material soil while alluvial soil is an example of transported soil. Topography of the place also affects the soil formation. On the steep slope surface erosion by runoff is more rapid and water penetration is less than gentle slope. On steep slopes soil is thinner and weathering process will produce less soil material. Contrary to 40 this, the gentle slope with good drainage and slow erosion helps in good soil formation. On these slopes there is balance between removal of soil and formation of soil. Another influence of topography can be seen in mid latitude areas of Northern Hemisphere. Only south Facing Mountain slopes of Northern Hemisphere experience warming and drying effect of sunlight. This is reflected by the type of vegetation and soil found on Northern and Southern slopes. Time is one of the most important factors in the soil formation. A soil is said to be mature when it has been acted upon by all soil forming processes for a long time and has developed a profile that remains the same for long period of time. No age in terms of years can be given to all mature soils because the rate is extremely slow from human point of view. A centimetre thick layer of soil takes several thousand years to from. Climate is an active agent of soil formation. Climatic elements involved in soil formation are: Moisture conditions (Precipitation, evaporation, humidity) Temperature Wind Precipitation provides water for chemical and biological activities and leads to disintegration of rock particles into simpler grain and so on. 41 Temperature affects the soil formation in two ways. Firstly, chemical activity is increased in warm and humid regions while slow in cold conditions and it is ceased in frozen conditions. Secondly, bacterial activity is increased in warmer soil regions. Among all wind is of minor importance as climatic factor. Wind increases the rate of evaporation and makes top soil loose and dry. Strong wind removes loose soil and deposits it at far off places such as loess plains of China. Both plants and animals influence soil formation. Sometimes we see plant coming out from the crack of a rock. Slowly the plant grows bigger and bigger which enable stem to exert pressure on the rocks which leads to disintegration. Similarly, there are some bacteria and fungi which eat rocks and decompose it. Soil Profile As the name suggests profiling of soil is called Soil Profile. As the formation of soil take place from top to bottom there is layer wise vertical difference in composition, texture, structure and colour etc. 42 Vertical section of the soil showing different layers is called soil horizon. These are named after English alphabets as A, B and C. The top layer of the soil is called A Horizon (top soil). This is the most important layer for agriculture point of view as all agricultural activities take place in this layer only. The thickness of this layer varies from one region to another. Approximately it is 25-30 cm. in thickness in general condition. Immediately below the A Horizon is Horizon B. Horizon B layer soil have coarser grain and less nutrient minerals. This is termed as sub soil. The thickness of this layer ranges from the bottom of top soil to a few meters downwards. Micro nutrient washed away from the top layer gets deposited in sub soil thus it is also called as Zone of accumulation. Too much of fine clay particles accumulated in subsoil makes it extremely dense and impermeable. Such dense layer is called as Hardpan. Below the sub-soil is the C horizon. C horizon mostly consists of partially altered parent rock and very little or no organic matter. About 2-3 meters from the surface starts the zone of subsoil. Below this layer is the platform of bed rock. In warm and humid areas there a very thin layer of dark brown colour substance above top soil called as the Humus Layer or O Layer. The Humus layer is very fertile. The humus layer, top soil and subsoil together called as Solum or true soil. All processes of soil formation and living roots, animal life are confined in this layer only. A thin layer of soil takes several hundred of years to form get washed away by several activities. Let us see the causes of removal of soil. 43 Causes of soil erosion Land use: Humans play a major role in soil erosion through their use and abuse of natural resources, for example; deforestation, grazing, arable land use, faulty farming systems, high crop intensity, housing construction, mining etc. Climate: The two most important climatic factors having a direct effect on erosion are Precipitation and Wind Velocity. Other climatic factors have an indirect effect on soil erosion. For erosion control it is necessary to investigate physical characteristics of rainfall, including the amount, distribution, intensity, energy load, seasonality and variability of rainfall and the formation and course of surface run off. Soil: The susceptibility of a soil to erosion is influenced by its physical, hydrological, Chemical and Mineralogical properties as well as its Soil profile characteristics. Important Soil physical and hydrological properties that affect the resistance of a soil to erosion include texture, structure, transmission properties and water retention. 44 Hydrology: Infiltration, surface detention, overland flow velocity, and subsurface water flow are important soil erosion components of the hydrological cycle. The different types of flow and their velocities may be turbulent or laminar, steady or unsteady, uniform or non-uniform and influence the extent of erosion Landforms: Slope gradient, slope length and shape of slope are the important variables of landform that affect erosion processes for all types of soil erosion, e.g.;, splash, sheet, rill, and gully erosion. Soil erosion causes two main problems: Loss of soil productivity: When topsoil erodes, the less fertile and harder B horizon becomes exposed. This leads to lower forage production, lower water infiltration and greater run off. Sediment pollution: When eroded sediment is rich in fertilizers or pesticides, it can upset the ecosystem at its point of deposition. In addition, sediments may damage machinery, agitate respiratory problems and reduce visibility. Control of Soil Erosion Soil Erosion prevention measures are implemented on a large-scale today. To name a few, they are shifting vegetation, afforestation, conservation tillage, gardening and contour farming. Erosion control products help in retaining the organic value of the soil as well as the pH. The requirements of the soil are restored by mulching. Soil erosion control is also carried out by planting erosion control plants. Native plants, willow trees, yarrow flowers help to retain the moisture of the soil. One of the most effective techniques to prevent soil erosion is by controlling the rate of grazing in a land vulnerable to erosion. 45 Regular watering of soil also keeps loose particle attached with the ground. Thus, preventing it from getting eroded. Soil, which is one of the most important natural resources, is often less heeded. The importance of soil conservation is relatively less talked about as compared to the conservation of water and other natural resources. The almost omni-present soil is mostly taken for granted. Its omnipresence is ironically the reason behind us, human beings, taking it for a ride. We rarely even think of it as a natural resource that needs to be conserved, a part of the natural wealth that needs to be preserved. The concept of the conservation of soil takes into account, the strategies for preventing the soil from getting eroded and preventing it from losing its fertility due to an adverse alteration in its chemical composition. Here are some ways to conserve soil. Ways to conserve soil Plant trees: We all know that the roots of trees firmly hold on to the soil. As trees grow tall, they also keep rooting deeper into the soil. As the roots of the trees spread deep into the layers of soil, they contribute to the prevention of soil erosion. Soil that is under a vegetative cover has hardly any chance of getting eroded as the vegetative cover acts as a wind barrier as well. Terraces: Terracing is one of the very good methods of soil conservation. A terrace is a levelled section of a hilly cultivated area. Owing to its unique structure, it prevents the rapid surface run off of water. Terracing gives the landmass a stepped appearance thus slowing the easy washing down of the soil. Dry stonewalling is a method used to create terraces in which stone structures are created without using mortar for binding. No-till farming: When soil is prepared for farming by ploughing it, the process is known as tilling. No-till farming is a way of growing crops without disturbing it through tillage. The process of tilling is beneficial in mixing fertilizers in the 46 soil, shaping it into rows and preparing a surface for sowing. But the tilling activity can lead to compaction of soil, loss of organic matter in soil and the death of the organisms in soil. No-till farming is a way to prevent the soil from being affected by these adversities. Contour ploughing: This practice of farming across the slopes takes into account the slope gradient and the elevation of soil across the slope. It is the method of ploughing across the contour lines of a slope. This method helps in slowing the water run off and prevents the soil from being washed away along the slope. Contour ploughing also helps in the percolation of water into the soil. Crop rotation: Some pathogens tend to build up in soil if the same crops are cultivated consecutively. Continuous cultivation of the same crop also leads to an imbalance in the fertility demands of the soil. To prevent these adverse effects from taking place, crop rotation is practiced. It is a method of growing a series of dissimilar crops in an area sequentially. Crop rotation also helps in the improvement of soil structure and fertility. Soil pH: The contamination of soil by addition of acidic or basic pollutants and acid rains has an adverse effect on the pH of soil. Soil pH is one of the determinants of the availability of nutrients in soil. The uptake of nutrients in plants is also governed to a certain extent, by the soil pH. The maintenance of the most suitable value of pH, is thus, essential for the conservation of soil. Water the soil: We water plants, we water the crops, but do we water the soil? If the answer is negative, it is high time we adopt the method of watering soil as a measure of conserving soil. Watering the soil along with the plants is a way to prevent soil erosion caused by wind. Salinity management: The salinity of soil that is caused by the excessive accumulation of salts, has a negative effect on the metabolism of the crops in soil. Salinity of soil is detrimental to the vegetative life in the soil. The death of 47 vegetation is bound to cause soil erosion. Hence, salinity management is one of the indirect ways to conserve soil. Soil organisms: Organisms like Earthworms and others benefiting the soil should be promoted. Earthworms, through aeration of soil, enhance the availability of macronutrients in soil. They also enhance the porosity of soil. The helpful organisms of soil promote its fertility and form an element in the conservation of soil. Indigenous Crops: Planting of native crops is known to be beneficial for soil conservation. If non-native plants are grown, the fields should be bordered by indigenous crops to prevent soil erosion and achieve soil conservation. Watch the video Watch the video Soil who need it Soil and water conservation 48 WORKSHEETS WORKSHEET–1 Answer the following questions: 1. What are the main landforms of the Earth? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. What is the name of the study of Earth’s landforms? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. Who propounded the cycle of erosion for the first time? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. What is meant by denudation? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ........................................................................................................................................... 49 5. Answer the following questions briefly: a) How wreathing can be stated with your understanding about the term? .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... b) How erosion can be stated with your understanding about the term? .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... c) How mass wasting can be stated with your understanding about the term? .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... d) How Deposition can be stated with your understanding about the term? .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... 50 WORKSHEET–2 Collect pictures of all types of landforms (mountain, plateau, plains, valleys and any other) for all continents of the world. You can use different sources like internet, old newspaper, old magazines and journals etc; for collection of pictures. Asia Africa North America South America Europe Australia 51 WORKSHEET–3 Collect and write information on the following: 1. 2. 3. Highest mountain peak of ____________ with its height. a) Asia b) Africa c) North America d) South America e) Europe f) Australia g) Antarctica Important plateaus of a) Asia b) Africa c) North America d) South America e) Europe f) Australia Name important plains of a) Asia b) Africa c) North America d) South America 52 e) Europe f) Australia. MCQ 1. Choose the correct answer form the given options: a) b) c) d) The upper part of the Earth is called? i. Lithosphere ii. Athensphere iii. Core iv. Mantle The forces that cause changes on the suface of the Earth can be divided into i. 2 ii. 3 iii. 4 iv. 5 Which of the following is an example of sudden Endogenic force? i. Earthquake ii. Mountain building iii. Rivers action iv. Wind action Which of the following is an example of Exogenic force i. Volcano ii. Landslide 53 e) 2. iii. Earthquake iv. Glaciers Which among the following is Endogenic force but is a slow process? i. Earthquake ii. Volcano iii. Landslide iv. Mountain building Answer the following questions: a) Where is the Earth Crust floating and why? .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... b) What are the different types of Earth processes? .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... c) What is the study of geomorphology? .......................................................................................................................................... .......................................................................................................................................... 54 .......................................................................................................................................... .......................................................................................................................................... d) Give a brief description on the weathering and erosion as stated by ancient thinkers. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... 3. Fill the blanks given in the diagram? 55 Answer the question with reasoning: Q. Form where do the Earth plates get energy to move and how this happens? Explain with diagram. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 56 WORKSHEET–4 MCQ 1. Choose the correct answer form the given options: a) Which among the following is important for chemical as well as physical weathering? b) c) d) i. Rock structure ii. Topography iii. Climate iv. Human Which of the following is an example of physical weathering? i. Exfoliation ii. Hydration iii. Hydrolysis iv. Oxidation CaSo4 + 2H2O → CaSo4 · 2H2O is an example of i. Hydrolysis ii. Hydration iii. Oxidation iv. Carbonation Which of the following will take place in karst region? i. 2Fe2O3 + 3H2O → 2Fe2O3 ·3H2O ii. KAISi3O8 + HOH → HAISi3O8 + KOH 57 iii. 2KOH + H2CO3 → K2CO3 + 2HOH iv. CaCO3 + H2O + CO2 → Ca (HOH3)2 Answer the following questions 1. What are the main processes of weathering? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. 2. What is mechanical weathering? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. 3. What is meant by chemical weathering? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. 4. What types of mechanical weathering are there? ................................................................................................................................................... 58 ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. 5. What types of chemical weathering are there? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. 6. Which regions are important for different types of weathering? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. 59 WORKSHEET–5 Explain the following diagrams. (a) (b) (c) (d) 60 1. Study the figure and answer the questions below. a Where is the rainwater going? b What happens when temperatures fall below 0°C? c Why has the crack widened? d What effect will this have on the rock? e Which process does this flow chart illustrate? 2. Study the figure and answer the questions below. a What kind of weathering is this? b How does this kind of weathering affect the rock? c Which climates speed up this kind of weathering? 3. 61 Study the figure and answer the questions below. a What happens to the crack as the roots get bigger? b What kind of weathering is this? c When the plant dies the roots decay and chemicals are produced. d What kind of weathering does this process cause? 4. Study the figure and answer the questions below. a Are the changes in temperature gradual or rapid? b In which regions do these fluctuating temperatures often occur? c Where are the points of weakness in the rock? d What is this weathering process called? e Which types of rock are affected by this process? 62 WORKSHEET–6 MCQ 1. Choose the correct answer form the given options: a) b) c) The load carried by the river water is called? i. Carrying capacity ii. Load capacity iii. Freight capacity iv. Weight capacity Which of the following is the most active in higher altitude? i. Deposition ii. Transportation iii. Erosion iv. Erosion and deposition Which of the following is an example of upper course landform made by river? d) i. Natural Levees ii. Interlocking spurs iii. Ox bow lake iv. Delta Ox bow lakes are formed due to i. Erosion activity only ii. Erosion transportation depositional activity 63 iii. Depositional erosion activity iv. Depositional activity. Answer the following questions: 1. What are the main actions of a river? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. How do rivers carry their load? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. Where do rivers have higher and lower rate of weathering? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. In which areas of a river, there is equilibrium in supply of material and erosion? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 64 5. How many stages are there in the journey of a river? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 6. Erosion is most active in which stage of a river? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 7. Deposition is prominent in which stage of a river? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 8. Name the landforms made by rivers in youth stage of a river. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 65 WORKSHEET–7 1. What landforms are made by rivers in equilibrium stages? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. What is flood? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. What is meant by Braided channel of river? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. What is delta? ................................................................................................................................................... ................................................................................................................................................... .................................................................................................................................................. 5. Where do rivers make delta? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 66 WORKSHEET–8 MCQ 1. Choose the correct answer form the given options: a) b) c) d) Karst topography is found in i. Sandy region ii. Coastal region iii. High altitude iv. Limestone region Which of the following is smallest in size? i. Swallow holes ii. Sink hole iii. Valley sinks iv. Uvalas Well developed karst topography can be seen in which region of the world? i. North America ii. South America iii. Europe iv. Asia The hanging feature in karst caves are called i. Cave pillar ii. Stalagmite iii. Stalactite iv. Blind valley 67 Answer the following questions: 1. In which areas Karst landforms can be seen? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. What Erosional landforms are made by groundwater? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. Why is it difficult to walk on limestone pavement? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. A landform is called blind valley even river do not flow through it. Why? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 68 5. What is the most magnificent landform made in Karst region? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 6. What are cave pillars or columns? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 7. How do chemical reactions occur in Karst region? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 69 WORKSHEET–9 Answer the following questions: 1. What are glaciers and where are they found? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. What is Firn or Nave? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. How many types of Glaciers are there? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. What are Nunatkas? ................................................................................................................................................... ................................................................................................................................................... 70 ................................................................................................................................................... ................................................................................................................................................... 5. What are Ice Shelves? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 6. What are Ice Bergs and why are they dangerous for navigation? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 7. What is Plucking and Abrasive action of Glacier? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 8. What are Crevasses in Glaciers? ................................................................................................................................................... ................................................................................................................................................... 71 ................................................................................................................................................... ................................................................................................................................................... 9. What is tarn and where is it formed in Glacier Topography? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 72 WORKSHEET–10 Answer the following questions: 1. Name the Erosional landforms made by glaciers. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. By observing Roche Moutannee how can we know the direction of glacier advancement? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. What are Tills? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. What do you mean by Moraine? Name different types of Moraines. ................................................................................................................................................... 73 ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 5. Why do Fluvio-glacial actions create only depositional landforms? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 6. Name Fluvio-glacial deposits landform made by glacier. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 7. Why do only small grains and sand particles make the Fluvio-Glacial Landforms? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 74 Word worksheet Find out word from the box related to glacial topotraphy. Words can be in row, column, and diagonals. A N D R U M L I N Q A S T E A M O R A I N E S X L R A U V W C R U U N A D M I W G S I K S D A M S T V D R C S E T O L O H N L T E E B A E R E F G S M Z G I R D O R L B A T L H P S P O N A S K T R E R I A K E Y A R S L T T E I R E A R E T E S A L I E E C G G S E S O L E C O M K E L V I K E L K I I R O U T W A S H P L A I N P O E L C E I M M E S S T A A J C N A A D W E L E S K E R S V E U O N S I S L A N D N E W Z A T P A B O U L D E R C L A Y N A F D U G L A C I E O L A P E N 75 1 4 5 6 5 1 2 3 34 2 Crossword worksheet In the above crossword features associated with sea wave action is given. With the help of hints given fill the crossword with appropriate words. 76 Down 1. Place near the coast. (7) 2. Bar connecting mainland and island. (7) 3. Protruding hard resistant rock towards sea. (4) 4. Small enclosed water body. (6) 5. The hurling action of sea water with debris and gravels (9) Across 1. Bars formed near sea shore by sea wave deposit. (4) 2. The whistling coastal landform. (8) 3. Small inlet of water by cutting soft rocks. (3) 4. Vertical wall like structure near coast. 5. Pillar like structure. (8) 6. The solvent action of sea water. (9) 77 WORKSHEET–11 Answer the following questions: 1. What are the main actions of sea waves? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. What is the Whistling landform near Sea Coast? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. What is the basic difference between Shingle beaches and Sandy beaches? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .................................................................................................................................................. 4. What are tombolos? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 5. What is a lagoon and how is it formed? ................................................................................................................................................... ................................................................................................................................................... 78 WORKSHEET–12 MCQ 1. Choose the correct answer from the given options: a) b) c) The topography made by wind in dry areas is called i. Karst topography ii. Sea wave topography iii. Eolian topography iv. Glacial topography Dreiknaters are i. Two facet sharp edge pebbles ii. Three facet sharp edge pebbles iii. Four facet sharp edge pebbles iv. Multi facet sharp edge pebbles Removal of sand particles till it reaches the groundwater saturated soil topography is. d) i. Vertrifacts. ii. Mushroom rock iii. Yardangs iv. Blow out The fertile deposition of very fine sand and dust particles are called. i. Yardangs ii. Zeugens 79 iii. Mesa and butts iv. Loess Answer the following questions: 1. Why winds are the most active agent of denudation in dry areas only? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. What are the main actions of the wind responsible for Landform creation? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. What are Dreikanters? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. How winds in dry regions carve Mushroom Rocks? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 80 ................................................................................................................................................... 5. What are Sand Dunes and name different types of Sand Dunes? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 6. Do Sand Dunes move and if yes then how? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 7. What is loess and how do they form? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 8. What are oases and what is its importance? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 81 WORKSHEET–13 MCQ 1. Choose the correct from the given option: a) b) c) The complex brown jelly like substances is called? i. Air ii. Water iii. Humus iv. Mineral matter Which of the following is having the largest share in soil composition? i. Air ii. Water iii. Organic matter iv. Mineral matter Which of the following is having the smallest share in soil composition? i. Air ii. Water iii. Organic matter iv. Mineral matter Answer the following questions: 1. What is soil? ................................................................................................................................................... 82 ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. What is importance of soil? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. The components that make the soil are found in which state? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. What is humus and what is its importance in soil? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 5. What is importance of water in soil? ................................................................................................................................................... 83 ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 6. Where do gases found in soil and what is its importance? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 84 WORKSHEET–14 MCQ 1. Choose the correct from the given option: a) b) c) d) Which of the following is smallest in size? i. Gravel ii. Clay iii. Sand iv. Silt Which among the following is the biggest in size? i. Gravel ii. Clay iii. Sand iv. Silt Which of the following soil will not allow water to percolate easily? i. Sand ii. Silt iii. Clay iv. Loam Which among the following will be having maximum porosity? i. Loam ii. Clay loam iii. Clay silt iv. Silt loam. 85 2. Observe the following data and answer the following questions: Comp. Clay clay silt loam Loam Silt Sandy loam loam Sand 10% 33% 40% 5% 75% Clay 45% 25% 18% 13% 11% Silt 45% 42% 42% 82% 14% After US Dept. of Agriculture, Yearbook 1938. a. Which soil is having the maximum proportion of clay in it? b. Which soil will be having maximum silt in it? c. In clay loam and loam soil both have same proportion of silt in it, among these two which soil the proportion of sand is high? d. 3. What is percentage of sand in sandy loam soil? Complete the following triangular diagram 86 WORKSHEET–15 MCQ 1. Choose the correct from the given option: a) b) c) d) How many factors affect soil formation? i. 2 ii. 3 iii. 4 iv. 5 How many passive agents from soil? i. 2 ii. 3 iii. 4 iv. 5 Which of the following soil is an example of residual soil? i. Red soil ii. Yellow soil iii. Alluvial soil iv. Black soil. Which slope will not have more active soil formation? i. Northern slopes of mountains north of tropic of cancer ii. Southern slopes of mountains north of tropic of cancer iii. Northern slopes of mountains south of tropic of cancer 87 iv. Southern slopes of mountains south of tropic of cancer Answer the following questions: 1. Which factors affect the formation of soil? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. What do you mean by active and passive agents of soil formation? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. How does topography play important role in soil formation? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. Which climatic factors affect soil formation? ................................................................................................................................................... ................................................................................................................................................... 88 ................................................................................................................................................... ................................................................................................................................................... 5. Which biological factors contribute in soil formation? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 89 WORKSHEET–16 MCQ 1. Choose the correct from the given option: a) b) c) How many horizons in the soil profile? i. 2 ii. 3 iii. 4 iv. 5 The top most layer of soil profile is i. A horizon ii. B horizon iii. C horizon iv. Bed rocks Zone of accumulation lies in i. A horizon ii. B horizon iii. C horizon iv. Bed rocks Answer the following questions: 1. What is meant by soil profile? ................................................................................................................................................... 90 ................................................................................................................................................... ................................................................................................................................................... 2. On what basis soil is stratified? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. Into how many vertical sections soil is divided, in general? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 4. What is the importance of top soil? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 5. What is meant by hard pan? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 6. What is found above the top soil in warm and humid regions? ................................................................................................................................................... 91 ................................................................................................................................................... ................................................................................................................................................... 7. What is solum? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 92 WORKSHEET–17 MCQ 1. Choose the correct answer from the given below: a) b) 2. Which of the following is a human factor in cause of soil erosion? i. Climate ii. Topography iii. Land use iv. Hydrology Which of the following is not a factor of soil that is susceptible to erosion? i. Soils with high water infiltration capability ii. Soils with low organic matter content iii. Soils on steep hills (especially in regions of high rainfall) iv. Soils with poor (unstable) structure Observe the given diagram and explain how erosion is taking place and which region this type of soil erosion is most common. 93 ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Answer the following questions: 1. What factors control the soil erosion? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. How is soil an important resource to us? ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 3. Suggest some ways to conserve soil form erosion. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 94 4. Make a list of five processes that is responsible for soil degradation. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 5. Make a list of five practices to conserve soil. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 95 REFERENCES http://armyengineer.tpub.com www.google.com/images www.natgeo.com www.discoverychannel.com www.wikipedia.com www.youtube.com Tarbuck and Lutgen, the Earth: an introduction to physical geology, 3rd ed. Merrill pub. New York. Thornberry, Principles of Geomorphology, 2nd ed. Wiley pub. New York. Strahler, A. N., Physical Geography, 2nd ed, Wiley pub. New York Environment, NCERT Textbook in Geography, Class 7th 96 CENTRAL BOARD OF SECONDARY EDUCATION Shiksha Kendra, 2, Community Centre, Preet Vihar, Delhi-110 092 India