Geo Ch 3 PDF

3. Agents of Erosion Can you tell ? Geographical explanation The names of many places may have You have seen how landforms may be used some relation with the landforms located to name places or villages....

3. Agents of Erosion Can you tell ? Geographical explanation The names of many places may have You have seen how landforms may be used some relation with the landforms located to name places or villages. Landforms have there. The names of few of them are given been formed due to certain processes. Agents below as example. You are expected to work upon them. Landforms develop over a long find out the particular landforms to which period. You have already learnt about the agents they are associated. Find about them and of erosion: running water (river), sea waves, try to locate them on a map using an atlas. wind, underground water and glaciers. They are Make a list of similar examples from India. the medium. These agents detach or separate, Discuss your findings in the class. pick up, move, and eventually lay down broken rock particles. These agents of erosion cause Landform various processes when they pick up, move and Name of associated with Location deposit these rock particles. These processes the place the name lead to erosional and depositional landforms. Raigad, Revdanda Sand bar Some processes are common across all agents Maharashtra but some are specific to a particular agent. Try Ganpati Ratnagiri, Beach to understand these processes with the help of the Pule Maharashtra Pravara Confluence of Ahmadnagar, table given below. The adjacent diagrams will Sangam rivers Maharashtra help you to visualize how the process operates. Sr. Processes of Erosion Agent Diagram No. 1. Plucking is the process by which moving Glacier ice exerts pressure on majority portion of rocks on bed or along the bank. This causes uprooting of rock portion which is getting exposed to the flow. This uprooting of particles is called plucking. The eroded bedrock will have a rugged surface. 2. Abrasion involves the scratching and Wind, polishing of the surface or bedrock by the glacier, sea particles which are moving onto it. Just as waves sandpaper is used for smoothening, the rock particles involved in abrasion rub against and wear away the surface. The eroded bedrock or surface will have a smooth side. Abrasion increases as velocity increases. 27 Sr. Processes of Erosion Agent Diagram No. 3. Attrition is when rocks and pebbles bump Wind , into each other and break up into smaller Waves, river fragments. During transit, materials reduce in size. Rock particles become more rounded. The difference between abrasion and attrition is that abrasion affects the surface along which the material moves and attrition relates to the material that moves. 4. Solution - Solution is when certain types of Underground rocks get eroded as a result of acids in the water, river, sea or river water. When minerals in rocks sea waves like chalk and limestone are dissolved in water, they are carried in the water. The load is not visible. In particular, limestone, dolomite and sandstone coasts are very susceptible to this type of erosion. 5. Deflation – The particles which are Wind loosened on the surface are blown away by the wind. This action is more intense where vegetation is absent. After removal, the portion from where sand is blown off appears as a depression. These are called deflation hollows. 6. Drilling - Bedload moves along the River running water. As and when this flow encounters an obstacle due to relief on the bed or joints in the bed, the flow tends to develop a circular pattern. This circular system becomes stable, though the water continues to flow in downstream direction. This leads to development of a whirl. The trapped sediments also follow the similar circular motion. The continuous action of these trapped sediments and the whirl deepens the bed of the river at a given point. Eventually, it develops into a larger depression assuming a shape of a pot. 28 Sr. Processes of Erosion Agent Diagram /Figure No. 7. Down cutting, also called downward River, erosion is a process of hydraulic action that glacier deepens the channel of a stream or valley by removing material from the stream's bed or the valley's floor. 8. Head ward erosion is the backward erosion River, by river in the source region. Gravel or glacier soil in the source region may collapse due to steep slope. This is carried away by the stream. This causes the river to move backward. Such erosion takes place in the opposite direction of the flow of the river. 9. Lateral erosion is the erosion that occurs River, on the sides of valleys of a river or glacier. glacier, sea The valley side slopes are eroded by the waves tributary streams. As and when, rate of downcutting decreases, the effect of lateral erosion becomes evident. This process is also called valley widening. In the valley floor region too lateral erosion occurs that mainly leads to widening of flood plains. Sr. Processes of Transportation Agent Diagram /Figure No. 10. Traction – The material acquired by the All except agents is transported by rolling, pushing and groundwater dragging along the surface. The material consists of boulders and big rocks. 11. Saltation – Often, rock materials move River, wind forward by leaps and bounds through this and sea process. Saltation is when material such waves as pebbles and gravel and coarse sand that is too heavy to be carried in suspension is bounced along the surface by the force of the water or wind. 29 Sr. Processes of Transportation Agent Diagram /Figure No. 12. Suspension - Fine light material is carried River, wind, along with wateror air in the upper layer. sea waves They are very small in size. For a long distance, they do not come to rest. 13. Solution – The material is carried in River, sea water in a dissolved state. In areas where waves, limestone or similar soluble rock is present, groundwater the amount of dissolved load in water is greater. 14. The process of deposition takes place due to certain factors in the course followed by the agent. The velocity at which the agent is moving has a great impact on deposition. If the stream or wind slows down, the carrying capacity will decrease and the particle sizes carried and deposited will also decrease. If a stream flows faster, say, during floods or when the river is in the mountains, then the carrying power of the stream will increase and the sizes of particles deposited will increase as well. If there is a change in the slope of the land, or change in direction of flow, deposition may occur there. Winds change their directions. When the slope is almost absent like in plain regions, the rivers are unable to carry sediments further and start depositing. Smaller particles settle more slowly than the larger particles, due to gravity. The smaller particles tend to stay in suspension for longer periods of time. Smaller particles are carried away till the end by river or wind. And their deposition occurs in the later stage. An obstacle like tree or mountain or similar structure may come in between. The agents may slow down because of obstacles. Deposition may take place at such a point. Understanding these processes will help you together or may also act singularly at different see how the action of different agents of erosion locations. Based on the effect of each of them, leads to landform formation. These landforms landforms produced by different agents can are a sum result of erosional, transportation be classified as erosional and depositional and depositional processes. These processes act landforms. Let’s recall. You have already learnt about various Sr. Page Name of the Agent Erosional / landforms formed by the agents of erosion No. No. landform Depositional in Class IX. Identify the landforms given in 1 30 class IX textbook from page no. 30 to 38. 2 31 Identify the agent which is responsible for their formation. Also, state whether they are 3 erosional or depositional landforms. Complete 4 the table accordingly in your notebook. 30  landforms. Picking up pieces of rock and moving Geographical explanation them require the river to have kinetic energy. You must have realized that not all agents When it has more kinetic energy, it can pick up of erosion are present everywhere. In arid and move more particles. regions, wind is the dominant agent while river As soon as a stream begins from its origin, it is the most common of all. Karst topography starts erosion. In mountainous areas, river flows occurs only where there are dolomite or calcium at a higher speed. Here, the bed gets more eroded rocks. There are many factors which control the than its banks. Gorges are formed with steep formation of landforms. They are climate, type banks and a narow bed. For example, the gorges of rocks, intensity of erosion, slope of the land of river Ulhas and river Narmada. Deeper gorges and obstacles. These factors affect the processes are called canyons. of erosion and deposition and the processes discussed above. For example, the wind starts Find out ! depositing when it is not able to carry the heavy load of the sediments. Thus, the process of Find out famous examples of gorges and forming depositional landforms begins. Rivers canyons. start depositing when their speed reduces. Though all agents of erosion are not present Over a period of time, river starts consuming everywhere, process of erosion and deposition its energy in transporting the material. occurs everywhere. Common processes lead to Consequntly, the bed is less eroded. However different landforms through different agents. the erosion along the banks and the slope of the Flood plains are formed due to deposition by valley increases. Hence, the valley with almost rivers while drumlins are formed by deposition vertical sides becomes wider resembling the letter by glaciers. 'V'. These valleys are called 'V' shaped valleys. Some times, water flowing over a hilly Agents of erosion and landforms : region comes down a cliff, waterfalls commonly Let’s understand how each and every agent get formed at such locations. When a river runs works to form various landforms. over alternating layers of hard and soft rock, Work of river : rapids and waterfalls are formed. Jog falls on the Sharavati river, Chuliya falls on river Chambal Think about it. and Venna falls in Mahabaleshwar are some well known examples. At the base of the waterfall, Have you ever been to a river and seen plunge pools can form because of constant gush its bed? Discuss in the class about your of water on the rock below. observations about the river, its banks, its Potholes generally originate in special bed and its velocity. circumstances, such as below waterfalls or where rocks are structurally weak. Swirling whirlpool Geographical explanation motions of the river water causes stones at the bottom to grind the bedrock and enlarge the A river, which is flowing water, erodes rock potholes by drilling while finer sediments are materials, transports them to newer places and carried away in the current. Potholes may range deposits them. In this process, it creates many from a few centimetres to many meters in diameter 31 and depth. Large potholes can be seen in the some material at the foothills. This leads to beds of river Kukadi at Nighoj in Ahmadnagar formation of alluvial fans. Coarse sediments district and river Indrayani at Bhegadewadi in like boulders and cobbles are deposited towards Pune district. In river beds, gravels and pebbles the apex. are often rounded. This happens because the rock As river enters the plains, the river now uses materials carried in the flow tumble and bounce much of its available energy for transporting against one another. This process called attrition the heavy load. The speed of erosion is reduced. makes the load fine-grained. Erosion on the outer bank and deposition on the inner bank of the channel leads to formation of Can you tell ? serpentine bends called meanders. During floods, Look at the figure below and answer the streams seek a shorter and straight path and may questions : not meander. This isolates a meander bend from Source the new flow channel of the river. If the cut-off A meander remains filled with water, it forms an oxbow lake. Height Flooding in this course increases the erosional work of rivers in the area of the gently B C Mouth sloping plain leading to formation of extensive Distance from source plains called floodplains. The richness of the 1) What features are formed in the upper soil, formed by material brought by the rivers course of the river? What processes will (alluvium) is beneficial for agriculture to thrive play an important role? here. During floods, these floodplains become 2) Can you mark the location where a inundated with sediment-filled water that deposits waterfall may formed? sediments on the sides of the river. This leads to 3) Why is there a change in slope from A to formation of natural levees on the sides of the B? How will it influence the flow of the river banks. river? Minimum gradient and close proximity to the sea makes erosion impossible in this region. 4) Which human activities can be conducted Heavy load and reduced velocity make the river in the region around A and B? break into various channels. They are called 5) In which area will the process of distributaries of a river because the load gets deposition overtake erosion? distributed. Here the river deposits the sediments 6) Alluvial fans and deltas are both within its channel as a result flow gets separated. features formed due to deposition but at Islands are formed. This takes a some what different locations. Identify their regions triangular shape. This distinct landform is called of formation and reason behind their a delta. See fig. 3.1. Deltas can only form at different locations. those river mouths where the sediment supply is high. It can be formed where the sea is not very When the river enters the plains, there is deep. Therefore, some rivers may not form delta a change in the slope. The river’s velocity is because they do not have huge load of sediments. reduced abruptly. As a result, it may deposit Instead they may form estuaries at the sea. 32 33 Fig. 3.1 : Work of river Work of sea waves : Can you tell ? Look at fig. 3.2 A and identify the landforms at A, B, C, D, E, F and G. A B C D E F G Fig. 3.2 : A) Work of sea waves developed where the rocks are least resistant Geographical explanation to wave erosion. This happens due to abrasion. Like running water sea waves too erode They are visible at lower water levels, such as at rocks. Abrasion is the most effective form low tide. They are also proof of cliff recession. of erosion by waves. Waves also erode rock The most common landform of coastal material chemically through solution. Salt deposition is the beach. The part of land weathering is particularly significant in coastal projecting into the sea is called headland. areas. The coast between two adjacent headlands If a steep coastal slopes continues deep is concave in shape. The eroded particles are beneath the water, the impact of waves may brought by the waves and deposited in this break the rocks. Sea cliffs are carved where portion. Besides, the rivers and other agents of waves strike directly against rocks. The softer erosion bring large amounts of sediment from rock along the coastline gets eroded first. the land. Moreover, as these areas are shallow, Sometimes, waves can erode the softer part and the velocity of waves decreases. As a result, all make it hollow enough to be called a cave. these different types of sediments get deposited A sea arch forms when waves erode in this area along the sea. Predominantly, fine a layer of soft rock underneath a layer of hard sand gets settled along the coast between the rock. If a sea arch collapses, it creates a sea headlands. Such sandy deposits along the coast. stack, which looks like a large rock in the middle are called beaches. Along the coastal areas in of water. Sea arches also result where two caves Maharashtra, long beaches have developed meet from each side of a headland. at Diveagar, Guhagar, Hareshwar, etc. The Surfaces at the base of the cliffs are called Marina beach at Chennai is the longest beach wave-cut platforms. Extensive platforms are in India. See fig. 3.2 B. 34  Sand also gets deposited along the sides of fresh water lagoon during monsoons. the headlands. Such deposition extends parallel Sometimes, such sand bars are not separated to the coast from one headland to the another. from the mainland and extend into the sea. They Over a period of time, these deposits extend are known as sand spits. Sand bars and sand spits over long distances and develop into a bund or may get separated from the land. bar that protrudes into the water at some distance away from the beach. These are called sand Uniqueness of coastal areas : bars. Along the coast in Maharashtra, we can Compare to the other agents of erosion, find sand bars at Shrivardhan and Revdanda. the work of sea waves goes on ceaselessly. The sand bars offer the first protection against Therefore, its effect becomes apparent within a storm or tsunami by absorbing most of their short period of time. Erosion in some part and destructive force. Between these sand bars and deposition in the adjoining part keeps on taking the land, a part of the sea gets enclosed. The place constantly. The beaches and bars which water in this enclosed sea is brackish. This are normally the products of deposition, are also brackish water is called a lagoon. Large waves subject to erosion. Coastal regions are always do not get generated in these lagoons as they get vulnerable to the risk of getting submerged due separated from the sea. These lagoons are like to increase in sea level. Coastal regions are also salt-water lakes. The Chilka Lake in Orissa and the regions of high population density. Therefore, the Vembanad lake in Kerala are examples of the coastal zone management warrants serious lagoons. The Chillka Lake in Orissa becomes a attention. Fig. 3.2 : B) Work of sea waves 35 Work of winds : Abrasion also contributes to formation of mushroom rocks. The high rising rocks in the path Geographical explanation of the wind are attacked by the sand that moves On a global level, wind is less effective as with the wind. Winds and the particles they carry an agent of erosion than running water, waves, attack the base of an individual rock. The larger top part is not eroded as much as the basal part. groundwater or glacier. But, wind is a significant The particles at medium height are smaller but agent in the deserts. Following conditions are their velocities are high. Hence, their impact is necessary for wind to become effective : more. As a result, the portion of rock at medium a) Aridity : In such areas, rate of evaporation height is eroded more and the rock as a whole is greater than rate of precipitation. gets the shape of a mushroom. See fig. 3.3 B. b) Sparse vegetation cover or absence of trees c) Presence of dry loose materials at the surface d) A wind velocity high enough to pick up and move sediments Strong winds blow frequently in arid regions. These movements of the wind pick up loose surface materials and transport them with wind currents. Deflation occurs when wind blowing fast enough in swirling motion over an area of loose sediment. It is able to pick up and remove small fragments of rock. This erosion can produce shallow depressions, which can vary in diameter from a few centimetres to a few kilometres are called deflation hollows. The Fig. 3.3 : B) Mushroom Rock Qattar depression in Egypt is formed in this way. In areas where hard and soft rocks are It is around 300 km long and 135 km wide. Its found, the softer rocks get more eroded faster. depression is 133 m below sea level. The eroded portion of softer rocks appear like Where the land surface is exposed, wind elongated ridges and harder rocks appear as can polish the rock surface through abrasion. elevated portions. A yardang is the remaining Abrasion carves the windward side of rock into part of a ridge where rocks have been eroded. smooth sloping surface. These rocks are called See fig. 3.3 C. ventifacts. See fig. 3.3 A. Fig. 3.3 : A) Ventifacts Fig. 3.3 : C) Yardang 36  Attrition reduces the size of the particles as The barchan slope that faces the wind is they dash against each other mutual bouncing. gentle whereas the opposite slope is steep. Transportation is carried out by winds Such hills can be seen in large numbers in where large-sized particles at lower heights the Great Indian Desert in Rajasthan. and finer particles at moderate heights through b) Longitudinal dunes are long dunes traction and saltation, respectively. All materials deposited in the direction of the wind. They transported by the wind are deposited. Coarser, appear parallel to the wind direction. They material is often deposited in the shape of hills, do not migrate like the barchans but extend called sand dunes. Fine-grained sediment such in the wind direction. They are also called seif dunes. They are sometimes hundreds of as silt, can be transported in suspension over kilometres long. Such dunes can bee seen in long distances from its source area. These Rub-al-Khali desert in Saudi Arabia. deposits are called loess.   Loess deposits form loess plains varying Types of Sand dunes : Sand dunes are classified in thickness from few centimeters or according to their shape and wind direction less to more than 100 meters. They are formed far away from deserts when winds a) Barchans are crescent-shaped dunes. They carry suspended particles for hundreds or form where supply of sand is minimum. thousands of kilometres. In northern China, Due to an obstacle in the path of the wind or the loess is 30 to 90m thick. It is formed by due to the lowering of its velocity, the sand the winds coming from the Gobi Desert. moving with it gets fropped at some places. They are fertile plains. See fig. 3.3 D. Fig. 3.3 : D) Work of wind 37 Work of groundwater : Study fig. 3.4 A. given above and answer the following questions. Formation of sink Sink holes Stalactite Stalagmite holes Pillar Cave Fig. 3.4 : A) Work of groundwater 1) Which rocks are mainly found here? of the world. The region around Mediterranean 2) Identify the spot where stream disappears. sea has large scale limestone features. These 3) Which major erosional process works in have majorly developed on the Karst Plateau this area? along Croatia’s Dalmatian Coast. Landforms developed by underground water anywhere in 4) Identify the landforms formed by deposition. the world are therefore called Karst landforms. 5) Why do depositional landforms not form on Other examples outside Europe are found in the surface in areas of Karst terrain? Mexico, USA, Caribbean Islands and southern Geographical explanation China. In India, they are found in isolated parts in Meghalaya, Bora caves in Andhra Pradesh, Like water flowing at the surface, water Kanhur Plateau in Maharashtra, some parts of beneath Earth’s surface moves, carries other Madhya Pradesh and Chhattisgarh. substances, influences the form and appearance Karst topography needs three important of the landscape. factors to develop : Water from precipitation, or melt-water i) Carbon dioxide : Warmer humid climate soaks into the ground. In areas, where the bedrock have greater amount of vegetation, which is soluble in water, like limestone, water below supplies CO2 to sub-surface water. CO2 is the surface is an important agent in shaping the necessary for the acidity of water which landform features. Sub-surface water dissolves, makes dissolving easier. removes, transports and deposits materials. ii) Active movement of underground water : Through the chemical removal of rock materials, Water saturated with dissolved CO2 should underground water is an effective agent especially have easy movement. The greater the where limestone is present. permeability of the rock, the faster ground The most common soluble rock is limestone, water will flows. a sedimentary rock composed of calcium iii) Joints : Fracture patterns and joints in the carbonate (CaCo3). Landform features created rocks in an area encourage passage for by sub-surface water are found in many parts water. 38 Erosional and depositional landforms : getting stored and flows parallel to the surface. Infiltration of water into the sub-surface tends Minerals like calcium carbonate present in the to be concentrated where joints and fractures rock there, get dissolved in this water. Over a exist in the rocks. This is the reason why the period of time this process gives rise to caves. groundwater forms landforms below the surface. Some are large enough and may extend to few In areas of land with water-soluble rocks, such kilometres. For example, one of the caves in as gypsum and limestone, the acidic water Meghalaya in India is 23 km long. dissolves the rock. Such cracks enlarge with The dripping water leaves behind a deposit time. They eventually become larger and then of calcium carbonate. Water dries in these caves due to continuous solution, develop into roughly from the ceiling. Water saturated with calcium circular surface depressions called sinkholes. carbonate dripping onto the floor of a cave builds The surface streams which sink disappear up similar but more massive structures. The underground through sinkholes. The surface structures growing from the ceiling are called streams which sink disappear underground stalactites. Those growing from the ground through sinkholes. Sudden collapse of sinkholes of the cave are called stalagmites. Stalactites could be a significant natural hazard. and stalagmites often continue to grow and In some areas, groundwater dissolves may meet to form columns or pillars. When the rock,leaving network of passageways. dripping water contacts the cave air, it releases Sometimes, the water that moves down through CO2 to the air. This is the reverse of carbonation sinkholes, strikes a compact and impermeable process causing the water to precipitate calcium rock layer. Instead of penetrating further, it starts carbonate. See fig. 3.4 B. Fig. 3.4 : B) Work of groundwater 39 Work of glacier : characteristic peak which is called a horn. The See fig. 3.5 A, B, C. Answer the following Matterhorn in the Swiss Alps is an example. As questions. the glaciers move ahead, they erode the sides 1) What differences do you find in the three as well as the bottom of the valleys they flow figures? through (lateral and vertical erosion) equally. This makes the valley broad at the bottom. 2) Identify the landforms formed due to This is called a U-shaped valley. You can see the erosion by glaciers. difference in the landform before glaciation sets 3) Where can U–shape valley be formed? in. The presence of glaciers (moving ice) changes 4) In which region will deposition start? the landscape. See fig. 3.5 A, B, C. 5) Identify the landforms formed by deposition Like rivers, glaciers too have tributaries. by glaciers. These tributaries also form U-shaped valleys. But, the rate of erosion is different because of Geographical explanation difference in sizes of glaciers. The main valley gets eroded faster and becomes deeper than the Glaciers are important agents of erosion tributary glacial valleys. These appear to be in high altitudes beyond the snowline and in hanging, when seen from the main valley. They polar areas. In areas with high latitude and high are therefore called hanging valleys. At the altitudes, precipitation is always in the form of confluence of hanging valleys and main valley snowfall. As a result, layers of snow accumulate and convert into ice. Due to tremendous pressure snow falls in blocks. At these locations, waterfalls of ice, layers of ice start moving down slope form after the glacier disappears. very slowly. Such a flow of ice is called glacier. 1) Drumlin : Coarse material that moves with As glacier is in solid state, its velocity is very glacier gets deposited at different places in low. Like other agents of erosion, glaciers too the form of heaps. They appear to have egg parry out erosion, transportation and deposition. like shape. Such heaps are called drumlins. Glaciers remove rock particles from the surface At times, large number of drumlins get on which they flow by plucking and by abrasion. deposited in an area. If you see this from Abrasion and plucking at the base of a glacier a higher elevation, it appears like a basket lead to formation of Roche moutonnees They of eggs. are bedrock hills that are smoothly rounded on the upper side by abrasion and plucking on the 2) Eskers : When the coarse material, moving lower side. with the glaciers is deposited in linear and zigzag manner it is called an esker. Ice movement, accompanied by weathering and mass wasting, steepens the wall at the head 3) Erratic rock : In the areas under the of the glacier. It deepens into armchair-shaped influence of glaciers generally at high depression called cirque. Often two or more latitudes, huge rock pieces are found to have cirques develop side-by side. This leaves the area been deposited in the area where the local between any two of them into a narrow wall. rocks are of different formation. Such rock This is called arête. Where three or more cirques appear as erratic ones to the area in which are formed, the headward erosion of the glacier they are deposited. These can be considered erodes the summit. This leads to formation of a as guest rocks. 40  Glaciers generally deposit load of terminal moraines. Where two tributary glaciers sediments along the side and front of the join together, their lateral moraines merge ice. These deposits are called moraines. The underneath to form medial moraines. moraines deposited at the sides of the wall are called lateral moraines. At the toe or foot of the glacier, sediment is deposited in a jumbled heap Use your brain power ! of all grain sizes forming a curved depositional ridge called end moraines. End moraines, that   In which diagram of the three will you mark the farthest advance of a glacier are called find end moraines? See fig. 3.5 A, B, C. Fig. 3.5 : A) Pre-glaciation Fig. 3.5 : B) During glaciation 41  Fig. 3.5 : C) Post glaciation Exercise Q. 1) Complete the table : Agents Erosional landforms Depositional landforms 1) River 2) Wind 3) Sea waves 4) Groundwater 5) Glacier Q. 2) Choose the correct option by identifying the 2) Sometimes, the river starts erosion upstream. correct correlation in the sentences : This happens when the head stream gets 1) Water or snow enters the cracks in the rocks a lot of water in the early stages of river’s and makes it weak. When the glacier passes flow. on these rocks, it pulls the rocks at the bottom a) Downcutting b) Headward erosion along with it. This process is called c) Lateral erosion d) Vertical erosion a) Plucking b) Abrasion 3) Soft rock erodes beneath the hard rock due c) Attrition d) Transportation to sea waves. This results into landforms 42  which further develop as sea arches. The 4) One finds many sheep rocks, horns, arêtes landform is and hanging valleys in the Himalayas. a) Sea cave b) sea stack 5) Karst landforms are seen concealed under c) sea cliff d) wave cut platform the surface of the earth. 4) This landform develops due to depositional 6) Snowline decides the limit of glacier work work of wind. The windward slope of this as an agent of erosion. landform is gentle. Q. 4) Write short notes on : a) Loess plains b) barchans 1) Attrition 2) The work of rivers in hilly areas and human c) Seif d) Sand hills activities 5) River, glacier, wind, sea waves and 3) Conditions necessary for work of wind. groundwater are the agents of erosion. Following work in the correct order is Q. 5) Distinguish between : responsible to form various landforms. 1) Attrition and Abrasion a) Disintegration, picking up, transportation, 2) U shaped valley and V shaped valley weathering 3) Stalactite and stalagmite b) picking up, disintegration, deposition, 4) Tributaries and distributaries weathering Q. 6) Answer in detail : c) deposition, transportation, picking up, 1) Explain the landforms formed by different disintegration agents through the process of abrasion. d) disintegration, picking up, transportation, 2) Explain how the depositional work done by deposition river Ganga has been beneficial to human Q. 3) Give geographical reasons : activities. 1) The Eastern coast of India have deltas 3) Which agents of erosion can you see on formed by the rivers but the Western coast the cover page of the textbook? Which has estuaries. landforms can you see there? Write the process of formation of any one.   2) There is direct relationship between the velocity of the agents and the process of Q. 7) Draw neat and labelled diagrams for : deposition. 1) Deflation 3) Compared to all the agents, sea waves work 2) Wave-cut platform ceaselessly. 3) Mushroom rocks  43