Resources and development: 10th Geography

Question: How is red soil formed? Mention its three characteristics.
Or
How does red soil develop? What makes it look red and yellow?

Answer: Formation: Most of the red soils have come into existence due to weathering of ancient crystalline igneous rocks.

Characteristics/Features :

1. Soils are loamy in deep depressions and in uplands. They consist of loose gravels and highly coarse materials.
2. The colour of these soils is generally red, often grading into brown, chocolate or yellow. The red colour is due to wide diffusion rather than high percentage of iron content. It looks yellow when it occurs in a hydrated form.
3. Soils are deficient in phosphoric acid, organic matter and nitrogenous materials but are fairly rich in potash. But crops are cultivated with the use of fertilisers.

Question: Which geographical factors are responsible for the evolution of black soil ? Why is it considered the most suitable for growing cotton ?

Answer:

1.  Climatic conditions like temperature, rainfall etc. along with present rock material are important factors for making of black soil. The parent rock is volcanic rock.
2. It is ideal for growing cotton because:
   (i) It has capacity to hold moisture.
   (ii) They are rich in calcium carbonate, magnesium, potash and lime.
   (iii) This soil is also known as black cotton soil,
   (iv) They develop deep cracks during hot weather, which help in the preparation of the soil.

Question: How is mountain soil (forest soil) formed? Mention any four characteristics of forest soil.

Answer: Formation: The soils are formed due to mechanical weathering caused by snow, rain, temperature variation, etc.

Characteristics / Features:

1. These soils are heterogeneous in nature, and their character changes with mountainous environment and altitude.
2. The soils are very rich in humus, but are deficient in potash, phosphorus and lime.
3. The soils are especially suitable for plantation of tea, coffee, spices and tropical fruits.
4. The soil is loamy and silty in valley sides and coarse grained in the upper slopes. It is acidic with low humus content in the snow covered areas. It is fertile in the lower parts of the valleys.

Question: Mention any four features of the arid soils.
Or
Name the soil type which is widely found in Western Rajasthan. Explain two important characteristics of this soil type which make it unsuitable for cultivation.

Answer: Arid soil is widely found in Western Rajasthan.

1. The soil ranges red to brown in colour.
2. The soils contain considerable amount of soluble salts.
3. The soils contain a low percentage of organic matter due to dry climate and absence of vegetation.
4. The soil is alkaline in nature as there is no rainfall to wash soluble salts.
5. The lower horizon of the soil is occupied by ‘kankar’ because of the increasing calcium content downwards. The ‘kankar’ layer formations in the bottom horizons restrict the infiltration of water.
6. The soils are infertile but with irrigation and fertilisers, the drought resistant and salt tolerant dry crops such as barley, cotton, wheat, millets, maize, pulses, etc., are grown. (Any Four)

Question: Explain the formation and important features of the laterite soil.

Answer: Formation: It develops in areas with high temperature and heavy rainfall. The laterite soil is a result of intense leaching owing to heavy tropical rains.

Features:

1. The soils are acidic in nature, coarser and crumbly in texture.
2. Due to lack of nitrogen, potassium and organic elements, the laterite soils lack fertility, and are not suitable for cultivation. But when the soils are manured and irrigated, some crops can be cultivated.
3. As the soils are indefinitely durable, so they provide valuable building materials.

Question: What is soil erosion? Explain the major types of soil erosion prevailing in India.

Answer: “Soil erosion is the removal of soil by the forces of nature like wind and water, more rapidly than the various soil forming processes can replace it”. Generally, there is a balance between the soil forming process and the erosional process. The balance can be disturbed by natural or human factors.

Types of Soil Erosion:

(a) Water Erosion: Water is a powerful agent of soil erosion. Following are the major types of erosion caused by water.

1. Sheet Erosion: When the top layer of the soil is removed over a large area by the running water, it is called as sheet erosion.
2. Rill Erosion: This is the second stage of sheet erosion. If erosion continues unchecked for a sufficient time, (rills) or small finger-shaped grooves which are a few centimeters in depth, may develop on the landscape. Over a period of time, the fine rills increase in number and also become deeper and wider, and resemble the twigs, branches and trunk of a tree. This is called as rill erosion.
3. Gully Erosion: This is the third stage of sheet erosion. With further erosion of the soil, the rills may deepen and become enlarged, and are ultimately turned into gullies. The main cause of gully erosion is the removal of vegetation, particularly of trees with their widespread binding roots. Gullies cut up agricultural land and the entire area may be turned into a bad land topography. Gully erosion is also responsible for the formation of ravines.

(b) Wind erosion: Wind is a powerful agent of erosion in arid and semi-arid lands with little rainfall. Wind can lift the valuable top soil from one area and deposits in another area. The wind erosion is very dangerous type of erosion because due to wind most of the deserts of the world are expanding.

Question: With reference to the types of soil, answer the following questions :
(1) Name any four regions or states where alluvial soil is formed.
(2) Name any four regions or states where red and yellow soils are formed.
(3) Name any four regions or states where laterite soil is formed.

Answer:

1. Rajasthan, Gujarat, deltas of Mahanadi and Godavari, and deltas of Krishna and Kaveri rivers.
2. Odisha, Chhattisgarh, Southern parts of the middle Ganga plain and the Western Ghats.
3. Karnataka, Kerala, Tamil Nadu and Madhya Pradesh.

Question: State two main differences between the Alluvial soil and the Red soil.

Answer: Alluvial Soil:

1. Alluvial soil is very fertile as it is rich in mineral nutrients like potash and lime.
2. Most of the alluvial soil is derived from the sediments deposited by the rivers.

Red Soil:

1. It is less fertile as it is deficient in phosphorus, nitrogen, lime and humus.
2. Most of the red soil has been formed due to weathering of ancient crystalline and metamorphic rocks.