Exogenic Processes And Resultant Landforms ~ Chapter 1 Geography ( Madhayamik Questions and Answers)
Chapter 1
Exogenic Processes And Resultant Landforms
~ Very Short Answer Type Questions:
Chapter 1 Exogenic Processes And Resultant Landforms Very Short Answer Type Questions:
Question 1. Which bank of a river meander experiences more erosion?
Answer: Concave slope / Outer bend
Question 2. At which altitude, the snow line is found in polar region?
Answer: sea level / 0 meter
Question 3. Name the sand dunes formed parallel to the wind direction.
Answer: Self-dunes / longitudinal dunes
Question 4. Name the largest valley glacier of the world.
Answer: Hubbard (122 km.)
Question 5. What is the name of the Sandy desert in the Sahara?
Answer: Ergs.
Question 6. From where the word ‘meander’ has been derived?
Answer: The word ‘meander’ is derived from the name of a small winding river ‘Meanders’ in Turkey.
Question 7. Which activity out of erosion and. deposition by river increases due to rejuvenation?
Answer: Erosion.
Question 8. In which stage does the incident river capture take place?
Answer: N.M. Davis.
Question 9. Give a single term for each of the following:
1. A stream that gets divided into a network of interconnected channels.
Answer: Braided Stream.
2. Raised banks of natural embankments built up of coarse deposits along the river channel.
Answer: Natural Levees.
3. Winding sections or loops of a stream.
Answer: River Meander and Oxbow lake.
4. A higher ground separating two adjoining drainage basins.
Answer: Water Divide.
5. A drainage pattern looking like the trunk and branches of a tree.
Answer: Dendritic pattern.
Question 10. Who put forward the idea of the ‘cycle of erosion’?
Answer: W.M. Davis.
Question 11. What are the three stages of the cycle of erosion?
Answer: Youth, maturity and old age.
Question 12. What is the deep vertical crack which opens up at the head of the glacier called?
Answer: Bergschrund.
Question 13. Name the typical crescent-shaped sand dunes in a desert.
Answer: Barkhans.
Question 14. What is the other word used to indicate the expansion of deserts?
Answer: Desertification.
Question 15. What is the shape of a glacial valley?
Answer: U-Shaped.
Question 16. What is Snout?
Answer: The glacier’s downstream end is known as the snout.
Question 17. What is Wadi?
Answer: The river valley created by the erosive action of rainwater due to sudden torrential showers in desert areas is called ‘Wadi.
Question 18. What is Pediment?
Answer: The highly eroded plain formed at the foot of the mountain due to erosive actions of both wind and running water in deserts is called ‘Pediment’.
Question 19. Who coined the term ‘Inselberg’?
Answer: S. Passage, a German geomorphologist.
Question 20. Who coined the term ‘Roche Moutonnee’?
Answer: De Saussure in 1804.
Question 21. What is a wind gap?
Answer: The weak place between the elbow of capture and the upper portion of the cutted river is called the ‘wind gap’.
Question 22. What is the ‘sixth power law’?
Answer: ‘Gilbert’ propounded his famous ‘sixth power law’, which states that rate of the discharge of water is directly proportional to the velocity of the river.
Question 23. In which regions sand dunes are found?
Answer: In the Desert Region and in the Coastal Region sand dunes are found.
Question 24. Name the largest valley glacier of India.
Answer: Siachen.
Question 25. Name the largest Piedmont glacier in the world.
Answer: Malaspina in Alaska (U.S.A).
Question 26. Name the local names of the sand dunes of the Malabar coast (Kerala).
Answer: Teries.
Question 27. Name the local name of the lagoons in the Malabar coast.
Answer: Kayal.
Question 28. Name the glacier of the Eastern Himalayas.
Answer: Zemu glacier.
Question 29. Which is the largest desert of the world?
Answer: Sahara desert in North Africa.
Question 30. Name the desert of India.
Answer: The Thar desert.
Question 31. In which continents are the Atacama and Kalahari deserts located?
Answer: Atacama in South America and Kalahari in Africa.
Question 32. What is the name given to the sandy desert in the Sahara?
Answer: Erg.
Question 33. What name is given to the stony desert in Algeria?
Answer: Reg.
Question 34. What is Hammada?
Answer: Hammada is the name given to the rocky desert of the Sahara.
Question 35. What is the other name of mushroom rock?
Answer: Gaur or Gara or Pedestal rock.
Question 36. Name the area of the largest loess deserts.
Answer: North China.
Question 37. Name two important features formed by the depositional work of the wind.
Answer: Sand dunes and loess.
Question 38. Define a glacier.
Answer: A glacier is a mass of snow and ice that moves slowly over the land away from the place of accumulation.
Question 39. Who proved that glaciers are not static but they move forward?
Answer: Louis Agassiz.
Question 40. What is the significance of snowlines?
Answer: Snow never melts above the snowline. A huge mass of snow above the snowline gives birth to glaciers.
Question 41. Name the biggest continental ice sheet of the world.
Answer: Antarctica.
Question 42. What is Playa?
Answer: The small salt lakes present in desert regions are called playa.
Question 43. Name the largest canyon of the world.
Answer: Grand Canyon of river Colorado in the U.S.A.
Question 44. Which is the largest delta of the world?
Answer: The Ganga-Brahmaputra Delta in India.
Question 45. What will be the transport competence of a river if its velocity is doubled?
Answer: 64 times. [The transport competence is proportional to the sixth power of the velocity of the stream.]
Chapter 1 Exogenic Processes And Resultant Landforms 2 Marks Questions And Answers:
Question 1. Define “Graduation”.
Answer: Gradation is the process of levelling of the land by natural agents like rivers, groundwater, winds, glaciers, and sea waves. The processes in gradation are erosion, transportation, and deposition.
Question 2. What is an alluvial cone?
Answer: As the river comes suddenly from its upper course to its middle course, its velocity decreases and its sediments are deposited along with the flow of the river resembling the shape of a cone or fan. This is known as the Alluvial cone.
Question 3. What do you mean by “piedmont glacier”?
Answer: In temperate regions, the snow line descends quite low. Here small glaciers descend at the foot of the mountains and start meeting with each other. It is called the piedmont glacier.
Question 4. Define “transverse dune”
Answer: A large, strongly asymmetrical, elongated dune lying at right angles to the prevailing wind direction. Transverse dunes have a gently sloping windward side and a steeply sloping leeward side. They generally form in areas of sparse vegetation and abundant sand.
Question 5. What do you mean by”Maidan”?
Answer: A wide flat land area whose height is generally low. Generally, flat and wide areas up to 150 meters above sea level are called plains.
Question 6. What is “Rann of Kutch”?
Answer: The Rann of Kutch is a salt marsh located in the Thar Desert in the Kutch District of Gujarat. Also referred to as the White Desert, it is about 30,000 sq. km. in size and is reputed to be one of the largest salt deserts in the world.
Question 7. What is Bergschrund?
Answer:
Bergschrund: A bergschrund is a long narrow crack developed at the source of the glacier. This is created when the mass of ice tends to flow down due to gravity and the mountain’s walls tend to hold back the ice due to friction.
Question 8. What is Canyon?
Answer:
Canyon: The valley formed by the river in its upper course in which vertical erosion is much greater than lateral erosion is known as an l-shaped valley as it resembles the English alphabet ‘I’. This valley is very narrow and very deep. It is also called Canyon.
Question 9. What do you mean by “Inselberg”?
Answer: Inselberg is a small, rounded hill, knob, ridge, or mini-mountain that rises abruptly from relatively flat surroundings. It is also called a monadnock.
Question 10. What is Plunge Pool?
Answer: In mountainous regions, waterfalls are created where the river drops from a considerable height with great velocity. Small depressions or hollows known as potholes are created at the base of the waterfalls due to the pounding of rock fragments brought down by the water. These potholes gradually grow bigger in size to form Plunge Pools.
Question 11. Define Loess.
Answer: Loess, an unstratified, geologically recent deposit of silty or loamy material that is usually buff or yellowish brown in colour and is chiefly deposited by the wind. Loess is a sedimentary deposit composed largely of silt-size grains that are loosely cemented by calcium carbonate.
Question 12. What is denudation?
Answer: Denudation involves the processes of weathering, erosion and transportation together. It is a term derived from the Latin word ‘denudate’ meaning ‘to strip bare’. It, therefore, causes the removal of rock layers from the earth’s surface resulting in the lowering of the land surface.
Question 13. How are the “deflation hollows” formed?
Answer: ‘Deflation hollows’ or deflation basins are formed by sweeping away of loose, light and dry sand particles by wind. They are also known as ‘desert hollows’ or ‘blow-outs’.
Question 14. What is Iceberg?
Answer:
Iceberg: Huge blocks of ice that break off from glaciers and fall into the sea are called icebergs.
Question 15. How are the bird’s foot deltas formed?
Answer: The deltas that look like a bird’s claw or fingers spreading one beside the other, are called bird’s foot deltas. Eg. Delta of the river Mississippi in North America.
Question 16. What is an estuary? What geographical conditions are needed for its formation?
Answer: Some rivers have strong tidal currents at their mouths and so the materials brought down by these rivers to their mouths are carried far into the sea. Deposition of materials at the mouth is almost impossible. The mouths of such rivers are very wide. The wide mouths of tidal rivers are known as estuaries. The mouth of the Thames is a typical estuary.
Question 17. What are the different types of deltas?
Answer: Three types of deltas are usually distinguished:
1. Arcuate or fan-shaped, e.g. Nile.
2. Cuspate or pointed like a tooth, e.g. Ebro.
3. Birds-foot type with fingering branches, e.g. Mississippi.
Question 18. What part does water play to modify a desert landscape?
Answer: In a desert torrential short-lived rainstorms cause sheet floods on level ground and flash floods down slopes and channels. Such occasional floods are disastrous.
Water action produces:
1. Wadis: large dry channels,
2. Bajadas: piedmont alluvial plain produced by the merger of a number of alluvial fans, and
3. Playas, Salinas, Dhand’s, and Bolsons: all different names for salt lakes.
Question 19. How do we identify a river’s realm or domain? What is a divide or watershed?
Answer: The land drained by a river, a natural drain, is the river basin; the area which supplies water is its catchment. Basin is a part of the catchment, and the two together constitute the domain of the realm of a river. A divide or watershed is the edge that divides two river basins.
Question 20. Distinguish between a bed and a valley.
Answer: A river flows in its bed which lies at the bottom of a curb called a valley. Although a river down cuts to form a valley floor, the shape of the valley sides is determined by mass wasting, which widens the narrow-cut bed made by the river.
Question 21. What is a basket of egg topography?
Answer: Basket of egg topography: When the Glacier faces an obstruction in its path, its load is more than it can carry, it dumps its load. These mounds taper two ends along the flow of the glacier, resembling upturned boats or eggs, as they are high at the centre, elongated and pointed at two ends. These are called Drumlins. Many drumlins deposited widely are also called “Basket of Eggs” topography.
Question 22. What is a glacier?
Answer: The term glacier is derived from the French word ‘Glace’, meaning ice. A huge mass of ice compressed and formed by the consolidation under the pressure of snow that moves slowly over land is called glacier.
Question 23. here is the source of the river Yamuna.
Answer: Yamuna originates from the Yamunotri glacier situated at the West of Gangotri (Uttranchal).
Question 24. What is a flood plain?
Answer: Floodplain All great rivers have wide-level lands adjacent to their banks over which they spill their waters in times of flood and deposit alluvium. Such low-lying alluvial plains built by rivers mainly during high water are called flood plains.
Example: Flood plains of the Ganga and Brahmaputra.
Question 25. What are the works of a river?
Answer: There are three works of a river
1. Erosion (in upper or mountain course),
2. Transportation (in the middle or plain course),
3. Deposition (in lower or delta course).
Question 26. Where are alluvial cones formed?
Answer: Alluvial cones are formed at the foothills of mountains where the river suddenly changes its slope from steep to gentle. Its velocity also suddenly decreases. So, the river’s carrying capacity suddenly drops & it deposits pebbles & other coarse materials at the junction of the mountain & plain. The shape of the deposition is like fan or cone, so it is called an alluvial fan or cone. They are found abundantly in the Terai region of the Himalayas.
Question 27. Name three features produced by wind erosion.
Answer: Features produced by wind erosion are
1. Inselberg,
2. Ventifact,
3. Gour.
Question 28. What is Dhand? Where it is found?
Answer: Deflation is a process of wind erosion occurring in desert regions. The high speed of wind lifts sand from one region & carries it. Thus, by the lifting of sand many big & small depressions formed. The small depression produced by deflation is called Dhand. It is found in the Rajasthan desert of India.
Question 29. What is Kame?
Answer: At the end of a glacier when among the terminal moraines, snow meltwaters cause the various stones, rocks, pebbles & clay, etc. to form a mould-shaped deposition with three-sided angular, is called Kame.
Question 30. Why is the river Ganga called an ideal river?
Answer: River Ganga is called an ideal river because it clearly shows three courses,
1. Youthful or upper course,
2. Maturity or middle course and
3. Old or lower course.
Question 31. What is the discharge of a river?
Answer: The discharge of a river is the combination of the volume and velocity of the river. It is measured in cusec (a cubic foot of water passing through the river at a point per second).
Question 32. Name two rivers of India which form an estuary.
Answer: The Narmada &Tapti rivers of India form an estuary.
Question 33. What are rapids & cascades?
Answer: When waterfalls have less steep slopes, they are called rapids. So, we may call them small waterfalls. It is found in the hilly regions of the Chhotanagpur plateau. When waterfalls flow down in many steps or in many channels or branches, they are called cascades.
Question 34. Give an example of a mountain glacier.
Answer: Zemu glacier (26 km in length) in the Karakoram mountain range is an example of a mountain glacier.
Question 35. What is Cirque?
Answer: Cirque is a basin (looks like a handle of a deck chair) cut into the side of a mountain by glacial erosion at the head of a glaciated valley.
Question 36. What is Hanging Valley?
Answer: The hanging valley is a valley of tributary glaciers located high above the valley of the main glacier. The streams in the hanging valley descend to the main valley as a waterfall.
Question 37. What is Roche moutonnee?
Answer: Roche moutonnee is a rock mound modified by glacial erosion. Its upstream surface is gently sloping & smooth while its downstream surface is steep & rough.
Question 38. Which is the largest glacier of the world?
Answer: Beardmore (160 km in length) which is the Antarctic continental glacier is considered the largest glacier in the world.
Question 39. Where is the world’s only equatorial glacier?
Answer: Mt. Cotopaxi in Equador supports the only glacier on the equator.
Question 40. What is a river?
‘Answer: According to Jackie Smith, “A river is a large stream of fresh water flowing down from the hills within a channel to enter or a lake or sea”.
Question 41. What is a river basin?
Answer: The principal river with its tributaries and distributaries drains a vast area. It looks like a basin. The area which is drained by a river and its tributaries and distributaries is called a river basin. The Ganga Basin is the largest river basin in India. The Amazon Basin of South America is the largest river basin of the world.
Question 42. What is water partings?
Answer: The highlands between the two adjacent river basins, which forms a natural boundary between the adjacent river basins, is called watershed or water partings.
Question 43. What are Interfluves?
Answer: The highlands separating one river valley from the next are called Interfluves.
Question 44. What are tributaries?
Answer: Tributaries are the smaller rivers that join the main river carrying the water from its surrounding.
Question 45. What are distributaries?
Answer: Distributaries are the branches or outlets which leave the main river carrying its water to the sea or lake.
Question 46. How far does the mountainous course of the river Ganga extend?
Answer: The mountainous course of the river Ganga extends from the icy cave of Gomukh on the Himalayas to the foothills at Haridwar.
Question 47. In which part of the course of a river depositional activity is most prominent?
Answer: The depositional activity of a river is most prominent in the lower course.
Question 48. What is Dhrian?
Answer: The mobile sand dune of Rajasthan is known as Dhrian.
Question 49. What is the shape of the valley carved out by a glacier?
Answer: The shape of the valley carved out by a glacier is U-like, i.e., U-shaped.
Question 50. In which regions sand dunes are found?
Answer: Sand dunes are found in deserts (Arabian deserts, Rajasthan deserts) and coastal areas of seas and oceans.
Question 51. What is Espers?
Answer: The long ridge of material deposited parallel to the direction of flow of the meltwater is called espers.
Question 52. What are kettle lakes?
Answer: The melted water from glaciers may get accumulated in holes or depressions created in the outwash plains due to the melting of a detached mass of ice that might have been left partly or wholly buried. These are called kettle lakes.
Question 53. What is salt weathering?
Answer: Salt crystallisation causes the disintegration of rocks when saline solution seeps into cracks and joints in the rocks and evaporates, leaving salt crystals behind. These salt crystals expand as they are heated up, exerting pressure on the confining rock. This is known as salt weathering.
Question 54. What is Stone Lattice?
Answer: When a rock with parallel series of hard and soft strata of an area is arranged both in horizontal as well as in vertical directions, a Stone Lattice is formed.
Question 55. What is Demoiselle?
Answer: There are many areas which are made of hard rocks. Winds subject the upper parts of the rocks to abrasion but the lower parts remain protected. The protected soft rock stands like a pillar below the hard rock and is known as Demoiselle or Earth Pillars.
Question 56. What do you mean by Col or Pass?
Answer: Col or Pass: When two cirques from opposite sides of a hill develop and meet each other, a col or a pass is formed. Many passes in the Alps were formed by glacial action. Some of the world’s passes are used for transportation.
Question 57. What is Fjord?
Answer:
Fjord: Fjord is a long narrow inlet with steep sides or cliffs, created by glacial erosion. It is generally formed when a glacier cuts a U-shaped valley by ice segregation and abrasion of bedrock. Most fjords are deeper than the adjacent seas. There are many fjords on the coast of Norway, Alaska, Iceland, etc.
Question 58. Differentiate between the valley shapes formed by the river and the glacier.
Answer: The valley shape formed by the river is V-shaped, while the valley developed by the glacier is of U-shape.
Question 59. Name two important deltas in India.
Answer:
1. The Ganga and the Brahmaputra have the most extensive delta,
2. The Delta of the Mahanadi.
Question 60. What is deflation hollow?
Answer: A deflation hollow is a vast depression on the sandy desert developed by the deflation action of wind erosion, i.e., by lifting and blowing away of sands from the ground.
Example: The Qattara Depression in Egypt.
Question 61. What is a pyramidal peak?
Answer: When several cirques are developed on all sides of a mountain, a horn-shaped pyramid is formed by the glacial action and is known as the pyramidal peak.
Example: Neelkanth peak on the Himalayas.
3 Marks Questions And Answers:
Question 1. Discuss in brief about three processes of river transportation activity.
Answer:
Transportation: The work by which the river carries away the eroded materials from one place to another is called transportation, the materials that the river transports are called its load.
There are four methods by which the river transports its load:
1. Solution: The materials like salts are usually dissolved in river water and are carried in solution.
2. Suspension: Sand, silt and mud are carried in suspension as the river flows. The majority of the river’s load (about 70%) is carried in this way.
3. Saltation: By this method, the larger loads jump up and then hit the bed and side of the channel and repeat this process to proceed further.
4. Traction load: The materials like rocks, boulders, pebbles, stones etc., which are too heavy to float are rolled along the river bed as traction (pulled) load.
The work of transportation is prominent in the upper and middle course of the river.
Question 2. State three differences between “Seif dune” and “Barkhan”.
Answer:
Question 3. Explain why a delta is formed at the mouth of a river.
Answer:
Formation of Delta: The velocity of the river is almost nil where it meets with the sea. Thus, the heaviest amount of depositions occurs here. The main channel is broken into numerous distributaries as more and more depositions take place. The region acquires a triangular shape and looks like the Greek letter Delta, hence the name.
Deltas develop under the following conditions:
1. The sea bed near the mouth of the river is very shallow.
2. Slope is negligible.
3. Tidal action is low.
4. Huge amount of bed load.
Question 4. Why is wind action dominant in desert regions?
Answer: Although the wind blows over the whole of the earth, its action is predominant in arid regions. This is because:
1. No obstacle in wind direction: In desert regions, due to lack of rainfall, there is no or very less vegetation cover. Thus wind blows unhindered at high speed.
2. Loose and exposed soil: Lack of vegetation makes the soil loose and exposed to wind action.
3. High diurnal range of temperature: Great difference between day and night temperature causes rocks to crack and break due to contraction and expansion. This makes the work of the wind easier.
Question 5. Discuss three factors affecting the transportation work of a river.
Answer:
Factors affecting the transportation work of a river: Following factors influence the transportation work of a river:
1. Velocity of Water: The velocity of water flowing in a river is the most important factor which influences the capacity of the river to transport its load. The increase in the velocity of water tremendously increases the transportation power of the river water. The transport competence is proportional to the sixth power of the velocity of the stream. If the velocity of the stream water is doubled, its competence is increased by:
(2)6 = 2x2x2x2x2x2 = 64times.
2. Volume of Water: Other things being equal, the transporting power of the water becomes double if the volume of water is doubled.
3. Size of the River Load: A stream can carry a much larger load of fine material than that of the coarser type. The distance up to which the eroded material is carried depends upon the size and weight of the fragments.
Question 2. Discuss the factors affecting the erosional work of a river.
Answer: Following factors influence the erosional work of a river:
1. Velocity of Water: The erosional work of the river depends upon the velocity of water in the river. On the hill slopes, the velocity of running water is much higher as compared to flat areas. Therefore, the erosional work by the river is more in the mountainous areas as compared to the plain areas.
2. Volume of Water: The increase in the volume of water in a river increases its capacity to erode. Accordingly, a river in flood has greater erosional power. In dry season when the volume of water in the river decreases, its capacity to erode is reduced.
3. Nature of Rocks: Soft rocks such as limestone and sandstone are eroded easily by the river whereas the river takes long to erode hard rocks like granite.
4. Load of the River: The running water by itself has little erosive action. The double work of corrosion or degradation of rocks by mechanical means, and corrosion or chemical weathering of the solid rock supply the load or the cutting tools for erosion. The corrosive work is mainly dependent upon the sediment load which a river current drags along with it. The eroded rock material helps the running water in deepening or vertical downcutting into the bed of the channel, lengthening as well as widening a river valley.
The sand, silt and pebbles are carried within the stream water in solution or suspension. The stones from the rocks and boulders are rolled along the bed of the stream. The particles get smoothened and rounded as they strike against each other and against the sides and bottom of the river valley.
Question 6. What are the agents of gradation? Which of them is the most important? Why?
Answer:
Agents of Gradation: Any natural agency which is capable of eroding and transporting earth material is known as an agent of gradation. The principal agents of gradation are water, snow, ice, wind and sea waves.
Rivers are the most important agents of erosion, transportation and deposition. That is, they carve their own valleys and carry the eroded material downstream where it is either deposited by the riverside or delivered into a lake or the ocean. Rivers are the most important agents in transporting the products of erosion.
They drain vastly larger areas than do glaciers, and, even in their short flowage on deserts, they are able to carry more material than the ever-present wind can. Weathering, mass wasting and rivers work together to shape the landscape.
Question 7. Explain how deltas are formed.
Answer:
Formation of Deltas: The main work of the river in its lower course is deposition. The materials brought down by the river are steadily deposited at its mouth and, as a result, new land is formed. The river cannot cut through it as the current at the mouth is very weak. So it divides into several branches and flows around the newly formed island. As the islands grow larger, they assume the shape of the Greek letter a, so it is called a delta. Most of the important rivers such as the Ganga, the Nile, the Mississippi, etc. have extensive deltas at their mouths.
Question 8. Explain the following:
1. Nunataks,
2. Ice shelves,
3. Iceberg.
Answer:
1. Nunataks: From the central dome of the ice cap, ice creeps out in all directions (extrusion process). The peaks of the loftier mountains project above the ice surface as nunataks (Eskimo word).
2. Ice-Shelves: When the ice sheets reach right down to the sea, they often float as shelves or tidal glaciers. They terminate in precipitous cliffs (seaward face).of ice called ice-fronts.
3. Iceberg: The tongues of the tidal glaciers are torn off by the buoyance of the seawater and great chunks float away in the form of icebergs. In the northern hemisphere, icebergs are like castles, towering high above the water; 10,000-15,000 are formed each year mostly from Greenland carried south by East Greenland and Labrador Currents.
They are rarely found in the Pacific Ocean, as the Bering Strait is shallow and narrow. The southern hemisphere icebergs are mainly tabular, large floating islands of ice. They move at about 6 km per day. Icebergs melt when approaching warmer waters, dropping the rock debris that was frozen inside them on the sea bed.
Question 9. What is an exotic stream? Name and locate four.
Answer: Some delta plains are on desert coasts. They are built by large streams which are fed by the abundant precipitation of mountain regions. Such streams have sufficient volume to flow right across the deserts and to discharge their loads into the bordering sea. These are exotic streams. Outstanding among them are the Nile, the Tigris-Euphrates, the Indus and Colorado.
Question 10. Define alluvium. Name the four principal classes of the alluvial plain.
Answer: Alluvium is the weathered and eroded material that is carried and deposited by streams.
The principal classes of alluvial plains are
1. Delta plains,
2. Flood plains,
3. Piedmont alluvial plains, and
4. Plains of older alluvium.
Question 11. Define the terms source, mouth, tributaries and distributaries.
Answer: The place from where a river begins its flow, is called the source of the river, and the place where its flow ends, is called the mouth.
Small streams and rivulets that descend to join the mainstream are called tributaries. A mighty stream receives innumerable tributaries.
On the lower course of the river, particularly near the mouth, several branches come out from the main channel and these are known as distributaries of the river.
Example: The Bhagirathi-Hooghly.
Question 12. What is a river basin?
Answer: The principal river with its tributaries and distributaries drains a vast area. It looks like a basin. The area which is drained by a river and its tributaries and distributaries is called a river basin. The Ganga Basin is the largest river basin in India. The Amazon Basin of South America is the largest river basin in the world.
Question 13. What do you mean by water partings or watersheds?
Answer: Sometimes, ridges and uplands separate the channels of running water. The uplands which divide the channels are known as water divides or watersheds or water partings. The Vindhya Range in central India divides the river basin of Narmada and Son. Elance, the Vindhyan range is a watershed between Narmada and Son rivers.
Question 14. Name and state the nature of work which a river does. Or, What are the works of a river?
Answer: As it begins to flow along the slope of the land, a river does a lot of work for its smooth journey to the sea. It reshapes the land through which it passes. The work of a river can be divided into three types:
(1) Erosion,
(2) Transportation and
(3) Deposition.
1. Erosion: It is the work of a river by which it wears away the land and breaks down its bed and the sides of its channel. The erosive actions of a river are of three types. These are:
(1)Solution,
(2) Attrition and
(3) Corrasion.
(1)Solution: this is the action in which the river dissolves the soluble rocks like limestone.
(2)Attrition: This is the action in which a load of a river such as pebbles and stones collide with each other and break into smaller pieces.
(3) Corrosion: The action in which river beds and sides of its channel wear away.
Corrasion is of two types:
(1) Vertical corrasion and
(2) Lateral corrasion.
(1)Vertical Corrasion: this is the process of down-cutting; when a river erodes downwards and deepens the valley, it is known as vertical corrasion.
(2)Lateral Corrasion: this is the process of side-cutting; when a river erodes the sides and widens the valley, it is known as lateral corrasion.
2. Transportation: The work in which the river carries away the eroded materials from one place to another is called transportation.
3. Deposition: The work in which the river deposits the transported material is called deposition.
Question 15. How are glaciers formed?
Answer:
Formation of Glaciers: Low temperature and sufficient snowfall are the two important factors for the formation of a glacier. Snowfall that occurs on the high mountains and plateaus and in polar regions each winter, does not melt away completely even during the next summer. Year after year, it accumulates and vast snowfields are formed.
It gradually turns into ice; the first stage from snowflakes to ice crystals is called ’Neve1 or ‘firn1. These are gradually transformed into a solid mass of ice. Then under the force of its own weight, due to melting at the bottom under the influence of latent heat of the masses of ice and owing to gravitational force, the solid mass of ice starts moving and is called a glacier.
Question 16. What are the processes of aeolian erosion? Or, How does wind work in an arid region? Or, Name the processes involved in wind erosion.
Answer: Winds cause erosion in three ways they are
1. Deflation,
2. Abrasion and
3. Attrition.
1. Deflation: The process by which the wind lifts and rolls along the loose particles on the ground is known as Deflation. It, thus, lowers the desert surfaces and causes extensive depressions.
2. Abrasion: This is the process in which the wind drives sand dust particles against an exposed rock or solid surface and results in rock surfaces being scratched, polished or worn away. This process is known as abrasions. It works most effectively near the base of rocks, where material blown by the wind is of the biggest size and the largest quantity.
3. Attrition: In this process, wind-borne particles roll against one another in a collision they wear each other away for this, their sizes are greatly reduced and .grains take rounded form.
Question 17. What are the three types of glaciers?
Answer: Glaciers are of three types:
1. Continental Glacier,
2. Valley Glacier or mountain glacier and
3. Piedmont Glacier.
1. Continental Glacier: Masses of ice which cover large areas of a continent are called Continental Glaciers. These are also called Ice-sheet.
Example: At present two major ice sheets are found in (1) Greenland and (2) Antarctica.
2. Valley or Mountain Glacier: The glaciers which originate and occupy mountain valleys are known as Valley Glaciers or Mountain Glaciers.
Example: The Gangotri Glacier of the Himalayas.
3. Piedmont Glacier: The word Piedmont means ‘the foot of the mountain’. The piedmont glaciers are formed by the union of the spreading ends of several mountain glaciers at the foot of the mountain.
Example: The Malaspina Glacier of southeast Alaska.
Question 18. What is sand dune?
Answer:
Sand Dune: A sand dune is a heap of sand. It is of several metres high. It moves with the prevailing winds. Sand dunes are formed by the accumulation of sand and are shaped by the movement of the wind. A sand dune is built up when the wind faces some obstruction in its paths, such as a bush, a tuff of grass or a large rock. Sand dunes are usually stationary, but they often move in the direction of the wind. However, they move very slowly. The mobile sand dunes of Rajasthan are known as Dorians.
Question 19. Into which parts can the course of a river be divided according to its work?
Answer: The course of an ideal river, from its source to its mouth, can be divided into the following three segments (sections) according to its mode of work:
1. The upper course, or the mountain course: In this stage, the main work of a river is erosion; however, it also does the work of transportation.
2. The middle course or the course on the plains: In this course, the main work of a river is transportation however, it also does the work of deposition.
3. The lower course or the course on the delta: Near the delta, a river does the work of deposition.
Question 20. Describe the factors on which the erosive power of a river depends.
Answer: The erosive power of a river depends upon the following factors:
1. Volume of water: It plays a vital role. A river cannot work more if the volume of water in the channel remains low. The ability increases with the rise of the volume of water. The volume of water that flows in a river is measured in a unit known as cusec or cubic metre per second.
2. Slope of the land: The ability to work of a river largely depends on it. As the slope increases, the velocity of flow increases too.
3. Load of a river: A load of a river acts as its tool. A river with a load of pebbles and stones can erode more.
4. Nature of land: The hardness of land exerts some influence on the work of a river. Soft rocks wear away easily, while hard rocks check the rate of erosion.
Question 21. What are the erosional processes of a river?
Answer: Erosion by a river is called fluvial erosion. River erosion is accomplished in the following ways, such as
1. Hydraulic plucking: Removing and carrying the loose bedrock by the action of the force of running water is known as hydraulic plucking.
2. Abrasion or Corrasion: The wearing away of rock beds by the collision of the flowing rock fragments and the static rocks is known as abrasion or Corrosion. It is of two types:
(1) Lateral Corrasion
(2) Vertical Corrasion.
3. Attrition: The process of the formation of finer materials by the pebbles, and stones being carried by a river due to collision with each other is known as Attrition.
Corrosion: The chemical weathering of the rocks is known as corrasion or solution. Rocks like limestone dissolve in the water.
Question 22. Describe the processes of river transportation.
Answer: A river transports the materials that had eroded as well as a greater mass of materials brought into the river flow. A river transports its load in several ways
1. Solution: When the soluble rocks are dissolved in water they are carried in the form of the solution by the river.
2. Suspension: The fine particles of the rocks remain in a suspended position as long as the force of the upward turbulence is stronger than the downward settling tendency of the particles.
3. Saltation(Latin: Saltere means to leap): The mode of transportation of eroded particles such as small pebbles which make intermittent leaps from the river bed is called Saltation.
4. Traction: Traction is the rolling of very big rocks along the floor of the river as they are too heavy to float in the river. So they roll along the floor of the river.
Question 23. What are the processes of glacial erosion?
Answer: Glacial Erosion consists of the following processes
1. Plucking: The pressure of the moving glacier on rocks along the mountainside pulls them and takes them away. This is called plucking.
2. Abrasion: Ice and its load move along and erode the rocks by scraping. It acts as a giant file grinding the floor and the sides.
3. Ploughing: Loose material is pushed ahead of the glacier, or rock material may fall from valley walls and come to rest on top of the ice.
Question 24. What is a snowline? Explain why its height varies.
Answer: Snowline is the lowest limit of perpetual snow:
The height of the snowline varies with latitude, altitude, seasons and precipitation.
Latitude: It is situated at sea level in the polar regions and about 5,000 metres in the equatorial regions.
Altitude: In the Alps and the Himalayas it moves between 3,000 and 5,000 m and higher still at Mt. Kilimanjaro on the equator.
Season and precipitation: On the southern slopes of the Himalayas the height of the snowline increases from east to Weston account of a progressive decrease in moisture supply. It varies from 4,000 m in the eastern part to 5,500 m in the western part. In summer it goes up, in the wet and cold season it comes down.
Question 25. Distinguish between a V-shaped valley and U shaped valley.
Answer:
Answer: When there is little water in a river a lean flow silts and creates a wide and dry bed but sometimes there is so much water that a river attains a bankful stage and often surplus water spills as a flood. The valley floor over which a flood deposits silt is the floodplain. The river bed is walled by banks, the floodplains by bluffs.
Question 27. Differentiate between alluvial cone and delta.
Answer:
Question 28. Differentiate between Yardangs and Barkhans.
Answer:
Answer:
Question 30. Differentiate the river valley from the glaciated valley.
Answer:
Answer: Landforms developed by glacial action
(1) Corrie and Arete: Corrie and Arete are the different types of features produced by glacial erosion. In the source regions of glaciers, in high mountain regions, glacial erosion causes a light depression to be eroded in such a way that the mountainside is steepened to form a headwall and at its foot, a pronounced depression is created by erosion.
When the glacier melts away in summer these resemble an armchair-like depression called Corrie in English and Cirque in French. Whereas, Arete is formed when glacial erosion may cause adjacent Corries to develop in the mountainside. The ridge that forms the boundary between the adjacent depressions is called Arete.
Question 32. Flow is the delta formed in the old stage of a river.
Answer: Near the mouth, at sea level, the main work of a river is the deposition of materials. Due to the heavy load of materials, the current of the river and its erosion action become weak and the accumulation of materials on the river bed is so high that the river is divided into many branches, forming islands between the two channels. This type of deposition resembles the Greek letter A and so is known as delta. Practically all the big rivers(e.g. Ganga, Nile, Mississippi, Missouri) have formed deltas. The delta of the Ganga is the largest in the world.
Question 33. What are the differences between a Gorge& Canyon?
Answer:
1. Gorges are deep narrow valleys which look like the English letter’V’. Canyons, on the other hand, are very deep& extremely narrow, so they resemble the English alphabet T.
2. Gorges are formed due to high velocity in rivers of rainy mountain areas whereas Canyons are formed in dry regions ‘or deserts.
3. As Gorges are formed in areas receiving high rainfall, either bank gets eroded to give the shape V & many tributaries join from either bank. But canyons are mainly snowed and flow through semi-arid or dry areas.
Question 34. Differentiate between pediment and outwash plains.
Answer:
1. Pediment plains are produced by the work of wind, whereas outwash plains are produced by the work of glaciers.
2. Pediments are produced by wind erosion whereas outwash plains are produced by glacial deposition.
3. Pediments are slightly sloppy, dry, stony plains whereas outwash plain is covered with rocks, stones, pebbles, sand, etc. It is a levelled plain with snowmelt water flowing on the ground.
Comments
Post a Comment