THE EARTH AND THE CHANGES ON IT (Chapter -2) SOLUTIONS

 D. Answer the following questions in brief.

D1. Specify two differences between internal and external forces

Ans: Internal forces:

(i) Internal forces are those which have been generating deep inside of the Earth surface. 

(ii) These forces are responsible to form major relief of the Earth like mountains, volcanoes, Plateau, Tectonic plate etc

    External Forces:

(i) External  forces are those which act on the surface of the earth causing a change in the nature and shape of a landform. For example, wind and water are the external forces which cause weathering and denudation of land.

(ii) These forces are modifying the shapes of the landform formed by the impact of internal forces

D2. Name the various agents of gradation.

Ans: Four agents of gradation are rivers, winds, sea water and glaciers.

D3.  Distinguish between transported and residual soil.

Ans: Soils which  are carried away by water, wind, etc., and later get deposited at a new place. Such soil is called transported soil. But, when the soil is formed by the weathering of a parent rock and remains present on the same site, it is called residual soil.    

 D4:  How is a delta formed?

Ans:  When the river reaches in its third stage and going to empty its water over the sea it  becomes large and sluggish and gets divided into several distributaries. It now comes to its old stage. The river, thus, deposits silt, sand and sediments over a large area near its mouth. This large deposition helps in the formation of a delta 

D5: Why is humus formed more rapidly in humid areas?

Ans: The humus formed rapidly in humid areas due to heavy growth of plants and rich animal life.

 

E1:  Explain weathering. Mention the factors that affect the rate of weathering and soil erosion.

 Ans:Weathering is a process by which rocks are disintegrated  into smaller pieces so that they can be taken away by agents of erosion such as wind, air or ice.

Rainfall, heat, moisture and the wind  are the main factors which affect the rate of weathering and soil erosion. Weathering happens more quickly in hot and wet climates. 

E2:  Explain the formation of soil with the help of a labelled diagram.

Ans: Soil formation is a very slow process.The weathering process breaks the rocks into small particles. These are then carried away by water, wind, etc.The soil forming process continues over a long span of time. It starts developing in layers, one over the other. These layers are called horizons

 

E3: What are the major soil types found in India? Give one important characteristic of each.

Ans: (i) Alluvial soil - widespread soil cover of India. 

        (ii) Black soil- Ideal for Cotton cultivation.

        (iii) Red soil - presence of iron. 

        (iv) Laterite soil - formed by leaching process.

        (v) Mountain soil - Texture and size changes as the height changes.

        (vi) Arid soil -  Rich in salt

E4: Describe the journey of a river from its source to its mouth.

Ans: River takes birth in a mountain or a hill. In its early stage, the river is young. It flows over steep mountains where its rate of erosion is maximum. Due to down cutting work of a river, it forms striking youthful features like ‘I’ shaped and ‘V’ shaped valleys, waterfalls, etc. 

As the river enters into the plains, it comes to the stage of maturity. Here, the volume of water increases and the slope of land decreases, resulting in slow speed of the river 

Before meeting the sea, the river becomes large and sluggish and gets divided into several distributaries. It now comes to its old stage. The river, thus, deposits silt, sand and sediments over a large area near its mouth

E5: Why is conservation of soil important? Suggest three different ways of soil conservation

Ans: Conservation of soil is important because it is use as a medium of plant growth and without it we can't be able to meet our need of food requirement and it is also indirectly responsible to maintain ecological balance over the earth's surface and nature has been taking the long geological period to make few cm layer of the earth surface
Three ways of soil conservation are -
(i) By encouraging terrace farming and contour ploughing.
(ii) By promoting afforestation.
(iii) By controlling overgrazing by animals.