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DAV CLASS 8 Land, Soil and Water Social Science Solutions
A. Tick () the correct option.
Which type of erosion leads to desertification?
(a) soil erosion
(b) wind erosion
(c) water erosion
(d) wave erosion
Answer 1. (a)
Which one of the following is suitable
for restoring soil fertility?
(a) terrace farming
(b) contour ploughing
(c) shifting agriculture along the hill slopes
(d) rotation of crops
Answer 2. (b)
Which of the following is not in favour of multipurpose river valley projects?
(a) control floods
(b) generate hydroelectricity
(c) large scale displacement of people
(d) provide water for irrigation
Answer 3. (c)
Maintenance of lakes and ponds is essential for—
(a) increasing surface water runoff
(b) increasing water table
(c) increasing soil fertility
(d) recycling of water
Answer 4. (b)
Which factor is more responsible for the quick formation of soil in Rajasthan?
(a) soluble rocks
(b) vegetation cover
(c) extreme difference in day and night temperature
(d) rainfall
Answer 5. (c)
B. Fill in the blanks.Earth’s surface is divided into and zones.
To maintain ecological balance,__________ % of the land should be under forest.
Planting of trees is commonly known as ________ .
The main source of fresh water is ________ .
Earth is known as ______ planet due to the presence of water on it.
Ans. 1. land; water 2. 3.afforestation 4. rainfall 5. Blue
C. Write a technical term or an appropriate word for each of the following statements.
It is formed by decomposed parts of plants and animals.
The original rock from which the soil is formed.
It is formed as a result of long-continued weathering process of rocks.
A project which serves various purposes at the same time.
The process in which the top layer of the soil is removed by the natural and human activities.
Ans. 1. humus 2.Parent rock 3.Soil 4.Multipurpose River Valley Project 5.Soil erosion
D. Answer the following questions in brief.
- Why is soil considered an important resource? Give any of these reasons.
Ans. Soil is considered an important resource because
(i) Agricultural production is mainly dependent upon the fertility of the soil.
(ii) Animals also depend upon the soil to satisfy their basic needs as soil gives nutrients to plants.
(iii) It is also used for making bricks and pottery. - Highlight any three causes of soil erosion.
Ans. The causes of soil erosion include both human and natural activities. Natural agencies such as water, wind, glacier, etc. cause soil erosion. But at the same time, mankind’s unwise actions such as deforestation, over-grazing
and mining is also responsible for soil erosion. It has been observed that the fertility of soil is severely damaged by soil erosion. - Explain the hydrological cycle with the help of a diagram.
Ans. The main source of freshwater is rainfall. This rainwater continuously gets recycled in nature through evaporation, condensation, and precipitation. This process is called the hydrological cycle.
- How does river water get polluted? Explain.
Ans. River water gets polluted as untreated industrial waste and urban waste is dumped into them. This makes the river water unsuitable for consumption. It also disturbs the ecosystem.
- Identify any three ecological problems caused by building large dams.
Ans. (i) Extensive forests get submerged underwater.
(ii) River water gets diverted.
(iii) Aquatic life gets affected.
E. Answer the following questions.
Explain any five factors which are responsible for the formation of soil.
Ans. The five factors responsible for soil formation are (i) Parent rock: The original rock, from which soul is formed by the process of weathering is known as the parent rock. It determines the color, texture, chemical, properties, minerals, content and permeability of the soil. For example, the black soil of India is derived from lava rock.
(ii) Topography: The location of soil on a landscape can affect how the climate processes affect it. Variations in the relief, such as mountains, plains and plateaus determine the thickness of the soil. For example, the northern plains have a thick soil cover than the Himalayas. Even within mountains, river valleys have thick soil cover.
(iii) Climate: Climatic factors like temperature and rainfall affect soil formation. In the areas of high rainfall and extreme temperature, rocks are easily weathered which affects soil formation.
(iv) The Vegetation Cover: Cracks disintegrate into smaller pieces and help in the soil formations. Remains of dead or decomposed plants and animals provide humus to the soil, which enriches the fertility of the soil.
(v) Time: It takes thousands of years to develop a very thin layer of soil on the earth’s surface. Example; the Nile Delta and delta formed by the Ganga and Brahmaputra rivers have very deep and fertile soil.
What is meant by land use pattern?
Why is it important to study the land use pattern? List the factors influencing the utilisation of land.
Ans. The use of land for various purposes such as for cultivation of crops, building of houses, roads, railways,grazing of animals, etc. is commonly known as land use pattern. It is important to study the land use pattern because the percentage of land used for various purposes various from one region to another. The utilisation of land is determined by the continuous interplay of the Physical factors, such as relief, soil, climatic conditions, mineral resources, etc., and the human factors like density of population and the technological and social requirements of the people.
What are Multipurpose River Valley Projects? Name any two such projects. List the main objectives of
a multipurpose river valley project.
Ans. Multipurpose River Valley Projects are large-scale hydro projects which have been developed all over the world to utilize water. Under them, a dam or series of dams are constructed across the river for storing water.
Two multipurpose river valley projects—
(a) Hirakud
(b) Bhakra Nangal
A multipurpose river valley serves many objectives at the same time. The stored water is used for several purposes, such as providing irrigation, generating hydro electricity, afforestation, control floods, navigation, etc.
Suggest any five steps to conserve soil.
Ans. Soil is an important natural resource. Therefore, its conservation must be given top priority. Various methods
of soil conservation are:
(i) Afforestation: It is the process of planting more trees and seeds on land. It reduces the surface runoff
and kinds the soil.
(ii) Shelterbelts: Rows of trees are planted in desert regions to protect the fields from wind erosion.
(iii) Rock dams: This prevents gullies and further soil loss since rocks are piled up to slow down the flow of water.
(iv) Terrace farming: Terrace farming should be encouraged across the hill slope. Terraces reduce run-off and soil erosion.
(v) Contour ploughing: Ploughing parallel to the contours of a hill slope to form a natural barrier for water to flow down a slope is called contour ploughing.
(vi) Overgrazing by animals like sheep and goats must be checked. Fodder crops should be raised. The free movement of animals in the fields should be restricted.
vii) Reckless cutting of trees should be checked.
Suggest any five methods for the conservation of water.
Ans. Water is an indispensable resource of life. We cannot imagine life in its absence. The sources of water are limited and are reducing every year. Therefore, its conservation is essential. Various methods of water
conservation are given below:
(i) Rainwater harvesting: It is a method of collecting water while it rains so that it may come of use in the future.
(ii) Improving underground storage: The surface run-off can be minimized by having vegetation cover to improve underground storage.
(iii) Making dams across the rivers: The rainwater can be impounded by making dams across the rivers.
(iv) Drip irrigation system: Water can be saved by adopting modern methods of irrigation, such as drip or trickle irrigation technique and sprinkler methods of irrigation.
(v) The demand of water for industries can be met by recycled water.
(vi) The domestic demand can also be reduced by using a modern method of recycling. The already used water can be reused for watering plants,flushing toilets.
(vii) Maintenance of lakes and ponds also helps in increasing the auifer or water table of underground water.
(viii) Water can be conserved by educating and sensitising people towards the urgent need to conserve water so
that they do not waste fresh water.
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