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Q. 1. Name the two types of agents of change.
Ans. External and Internal.
Q. 2. Name two processes involved in denudation.
Ans. Weathering and Erosion.
Q. 3. What does the term denude mean ?
Ans. To lay the rocks bare.
Q. 4. From which word the term denudation is derived ?
Ans. Latin word ‘denudare’.
Q. 5. What is weathering ?
Ans. Breaking up of rocks by agents related to atmosphere.
Q. 6. Name three important agents of weathering.
Ans. Frost, wind, heat and cold.
Q. 7. Name the three types of weathering.
Ans. (i) Mechanical (Physical) (ii) Chemical (iii) Biological.
Q. 8. State four factors which determine weathering in an area.
Ans. Structure of rocks, slope of the land, climate, vegetation.
Q. 9. What is the main process involved in Mechanical weathering ?
Ans. Disintegration of rocks.
Q. 10. What is exfoliation ?
Ans. Peeling off the outer layers from main rock.
Q. 11. What term is used for broken fragments by weathering ?
Ans. Talus or Scree.
Q. 12. How much expansion in volume takes place when water turns into ice ?
Ans. About 1/10th.
Q. 13. What term is used for disintegration of rocks by frost ?
Ans. Thaw freeze or Frost shattering.
Q. 14. In which type of areas, is the frost action found ?
Ans. In cold areas and in high mountains.
Q. 15. Name an umbrella shaped rock mass found in India.
Ans. Toad rock in Rajasthan.
Q. 16. What are earth pillars ?
Ans. The soft rock pillars capped with hard rocks.
Q. 17. Where are earth pillars found in India ?
Ans. In Spiti valley (Himachal Pradesh).
Q. 18. What are land slides ?
Ans. When rocks slide down the slopes, under the force of gravity due to increased weight by rain water.
Q. 19. What is bad-land ?
Ans. An area dissected with gullies and ravines.
Q. 20. Name a bad-land topography found in India.
Ans. Chambal valley.
Q. 21. What does the term ‘in situ’ mean ?
Ans. When rocks are chemically weathered at the same place.
Q. 22. Name the gases involved in the process of chemical weathering.
Ans. Weak acids, oxygen, carbon dioxide, hydrogen.
Q. 23. What main process of breaking rocks is involved in chemical weathering ?
Ans. Decomposition of rocks.
Q. 24. Which is the gas involved in oxidation ?
Q. 25. Name the four processes of chemical weathering.
Ans. Oxidation, Hydration, Carbonation a n d Solution.
Q. 26. What is soil ?
Ans. The uppermost layer of earth’s crust.
Q. 27. Name the components of soils.
Ans. Minerals, humus, water, organisms.
Q. 28. Name the different soil horizons.
Ans. A-Horizon (Top soil), B-Horizon (Sub soil), CHorizon (Mantle).
Q. 29. Name the dead organic matter found in soils.
Q. 30. Which substance is the most important constituent of soil ?
Q. 31. What do you mean by parent material ?
Ans. Rocks from which soil is derived.
Q. 32. In which soil horizon, is humus found ?
Ans. Top soil.
Q. 33. What is soil profile ?
Ans. A cross-section of soil into layers.
Q. 34. What is soil erosion ?
Ans. The removal of top soil.
Q. 35. What is deforestation ?
Ans. Reckless cutting of forests.
Q. 36. What is afforestation ?
Ans. Planting of trees in new areas.
Q. 37. What is terraced agriculture ?
Ans. Cultivation along terraces on hill slopes.
Q. 38. What is contour ploughing ?
Ans. Ploughing at right angles to the slope.
Q. 39. What is Pedology ?
Ans. The science that deals with study of soils.
Q. 40. What is Eutrophication ?
Ans. Enrichment of water with nutrients causing abundant plant growth.
Q. 41. Why is the earth crust unstable ?
Ans. The earth crust is dynamic. Continents have been drifting. Drift has occurred horizontally as well as vertically. The internal forces operating from within the earth are also responsible for variation on the outer surface of the earth.
Q. 42. Name the different external agents.
Ans. The following external agents bring changes on the surface of the earth : (i) Weathering (ii) River (iii) Wind (iv) Glacier (v) Sea-waves.
Q. 43. On what factors does the weathering depend ?
Ans. Weathering depends upon :
(a) structure of rocks
(d) topography and slope of land.
Q. 44. Name the gases which help in chemical weathering.
Ans. The following atmospheric gases help in the process of chemical weathering :
(iii) Carbon dioxide.
Q. 45. Name the main processes involved in chemical weathering.
Ans. The main processes involved in chemical weathering are :
Q. 46. Gravity and Gradient help the movement of all types of materials. How ?
Ans. Mass movements are aided by gravity and geomorphic agents like running water, glaciers, winds, etc. Without gravity and gradient, mass movement is not possible. Gravity starts the movement on the surface. All movements are caused due to gradient. From higher level to lower one, from high temperature to low temperature, and from high pressure to low pressure areas, movement takes place due to gravity and gradient.
Q. 47. What is weathering ?
Ans. The disintegration and decomposition of rocks (chemically and mechanically) by the agents of weather and climate is called weathering. It is insite as well as on site.
Q. 48. What do you mean by enrichment ?
Ans. When rocks undergo weathering, some materials are removed through chemical or physical leaching by groundwater and thereby the concentration of remaining (valuable) materials increases. Without such a weathering taking place, the concentration of the same valuable material may not be sufficient and economically viable to exploit, process and refine. This is what is called as enrichment.
Q. 49. Name three types of mass movements.
Ans. Mass movements can be grouped into three major types :
(i) Slow movement.
(ii) Rapid movement.
Q. 50. Explain the significance of weathering.
Ans. (i) Weathering prepares the way for soil formation.
(ii) Weathering is responsible for erosion and mass movements.
(iii) Erosion cannot be significant if nodes are not weathered.
(iv) Landforms are a consequence of weathering.
(v) Weathering is an important process in the formation of soil.
(vi) It helps in the enrichment and concentration of valuable ores.
Q. 51. Define soil.
Ans. The uppermost layer of the earth’s crust is called soil. It consists of a thin layer of loose material of rock waste. The soil consists of mineral particles, organic matter (humus), water, air and living organisms (bacteria).
Q. 52. What is humus ? How is it formed ? What is its significance in soil formation ?
Ans. Humus. Humus is a dark substance formed in soils. It is a dead organic matter formed by decay of animals and plants. Trees, shrubs, grass and bacteria help in the formation of humus. In warmer climates, humus is destroyed by countless bacteria. In colder areas soils are rich in humus and it is collected in the soil. Tropical humid soils are poor in humus because it is consumed by bacteria.
Humus is vital to the fertility of soils. It provides nitrogen, phosphorus and calcium to the soils. It sustains other forms of life. It helps the weathering of minerals to add to fertility of soils. It increases water holding capacity of soils.
Q. 53. Describe the work of frost in polar areas.
Ans. Frost. Frost is an important agent of weathering in cold climates and high mountainous areas. In such areas water enters the rocks through fissures, cracks and joints. This water freezes into ice during the night and its volume increases 1/11 times.
As it expands, it exerts pressure on the rocks which causes a widening of the cracks. There is repeatedly melting and freezing of water. It makes the cracks wider still. The action is similar to a wedge and is known as thaw freeze or Frost shattering. Finally, the rocks are split into blocks. Sharp-edged rocks are formed by repetition and long continued action of frost.
Q. 54. How are earth pillars formed ?
Ans. Earth pillars. Rain washes away soft material in clay regions. The boulders or hard rocks like a cap protect the underlying rocks with the result, earth pillars are formed. When the cap rocks fall, the earth pillars are destroyed. The examples of earth pillars are found in Bolzano (Italy) and Spiti valley (Himalayas).
Q. 55. What is oxidation?
Ans. Oxidation. The atmospheric oxygen combines with minerals of rocks especially iron compounds to form oxides. With the result, rocks get rusted as iron is rusted due to presence of air and water. The original colour of the rocks changes into red, yellow or brown.
The rocks begin to decay and crumble to a powdered mass of brown dust. This process is known as oxidation.
Q. 56. What is carbonation?
Ans. Carbonation. Rain water mixed with carbon dioxide is slightly acidic. It dissolves limestone, chalk and marble rack. In limestone areas, this acid water sinks into the ground and forms huge caves by a slow process of carbonation.
Q. 57. Describe the importance of soils.
Ans. Soil is a valuable natural resource. Mankind has lived and continues to live on the soils. Many human and economic activities depend upon soils. All our food comes directly or indirectly from soils. Livestock farming depends upon raising of grass on different soils. Soils form an important element for all living things.
Soils have affected the march of civilizations. Ancient civilizations developed in fertile river valleys. Fertile soils attract human settlements.
Q. 58. What are the functions of soil for which it needs to be preserved?
Ans. Soil has a great significance for mankind as a basic natural resource. It occupies a significant place in the biosphere. Good soils lay the basis of a flourishing agriculture and human habitation. Due to soil erosion, productivity is reduced. Soils are the basis for providing food stuffs and agricultural raw materials for industries. Therefore, all measures are adopted to preserve soils.
Q. 59. Distinguish between Geomorphic agent and Geomorphic process.
Ans. Any exogenetic element of nature (like water, ice, wind, etc.) capable of acquiring and transporting earth materials can be called a geomorphic agent.
When these elements of nature become mobile due to gradients, they remove the materials and transport them over slopes. That means, immobile they affect the materials and mobile they remove, transport and deposit the same. Geomorphic processes and geomorphic agents especially exogenetic, unless stated separately, are one and the same.
A process is a force applied on earth materials affecting the same. An agent is a mobile medium (like running water, moving ice masses, wind etc.) which removes, transports and deposits earth materials.
Running water, groundwater, glaciers, wind, waves and currents, etc., can be called geomorphic agents.
Q. 60. Describe the various factors helping mass movements.
Ans. Several activating or initiating causes precede mass movements. They are, (i) removal of support from below to materials above through natural or artificial means, (ii) increase in gradient and height of slopes, (iii) overloading through addition of materials naturally or by artificial filling, (iv) overloading due to heavy rainfall, saturation and lubrication of slope materials, (v) removal of material or load from over the original slope surfaces, (vi) occurrence of earthquakes, explosions or machinery vibrations, (vii) excessive natural seepage, (viii) heavy drawdown of water from lakes, reservoirs and rivers leading to slow outflow of water from under the slopes or river banks, (ix) indiscriminate removal of natural vegetation. Heave (heaving up of soils due to frost growth and other causes), slide and flow are the three forms of movements.
Q. 61. What do you mean by Diastrophism ? Which processes are included in it ?
Ans. Diastrophism. All processes that move, elevate or build up portions of the earth’s crust come under diastrophism. They include :
(i) orogenic processes involving mountain building through severe folding and affecting long and narrow belts of earth’s crust,
(ii) epeirogenic processes involving uplift or warping of large parts of the earth’s crust,
(iii) earthquakes involving local, relatively minor movements,
(iv) plate tectonics, involving horizontal movements of the crustal plates.
In the process of orogeny, the crust is severely deformed into folds. Due to epeirogeny, there may be simple deformation. Orogeny is a mountain building process whereas epeirogeny is a continental building process.
Through the processes of orogeny, epeirogeny, earthquakes and plate tectonics, there can be faulting and fracturing of the crust. All these processes cause pressure,volume and temperature (PVT) changes which in turn induce metamorphism of rocks.
Q. 62. On what forces does the physical weathering depend ?
Ans. Physical weathering is also called mechanical weathering. The applied forces can be :
(i) Gravitational forces such as over burden pressure, load and shearing stress.
(ii) Expansion forces due to temperature changes, crystal growth or animal activity.
(iii) Water pressure controlled by wetting and drying cycles.
These forces lead to rock failure or fracture. Most of the physical weathering processes are caused by thermal expansion and pressure release.