(CLASS - 7th) CHAPTER - 2 The Earth and the Changes on It (Questions and the Answers)
1. Specify two differences between internal and external forces .
- Any process working on the earth's surface and bringing changes on it, is known as external process.
- The external process may lower the level of land by wearing away rock particles. It can also raise the level of land where the soil particles are deposited.
- Internal Forces are forces between objects found inside the system
2. Name the various agents of gradation.
Various agents of gradation.
- Running water
- Wind
- Ice
- Sea Waves
3. Distinguish between transported and residual soil.
The weathering process breaks the rocks into small particles then 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.
4. How is delta form?
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 sentiments over a large area near its mouth. This large deposition helps in the formation of a delta.
5. Why is humus formed more rapidly in humid areas ?
The humus present in the soil contributes to the fertility of the land. This is rapidly formed in humid areas due to heavy growth of plants and rich animal life. However, humus is low in desert soil.
E.
1.Explain weathering. Mention the factors that effect the rate of weathering and soil erosion.
Weathering
The term weathering refers to the process that breaks rocks into smaller particles. It includes erosion and deposition .They disintegrate as they are exposed to all types of weather changes.
The rate at which erosion takes place depends upon the temperature of a place , vegetation cover, rainfall , slope of the land , type of soil and changes in land use.
2. Explain the formation of soil with the help of a labelled diagram.
Soil is the thin layer of material covering the earth’s surface and is formed from the weathering of rocks. It is made up mainly of mineral particles, organic materials, air, water and living organisms—all of which interact slowly yet constantly.
Factors affecting formation of soil may be atmospheric, such as changes in temperatures and pressure; erosion and transportation by wind, water and glaciers; chemical action such as crystal growth, oxidation, hydration, carbonation and leaching by water, especially rainwater, with time.
So in general,formation of soil takes place by two methods:
☆Physical disintegration of rocks
☆Chemical decomposition of rocks
3. What are the major soil types found in India ? Give one important characteristic of each.
The major soil types found in India
Alluvial soil - It is very fertile and forms major agricultural land of our country.
Black soil - This soil has an ability to retain moisture and become sticky when wet.
Red soil - It is highly porous, fine grained and deep.
Laterite soil - It is formed by the leaching process.
4. Describe the journey of a river from its source to its mouth.
In the early stage, the river is young. It flows over steep mountains where its rate of erosion is maximum.
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. This large deposition helps in the formation of a delta .
This delta of Ganga and Brahmaputra is the largest in the world.
5. Why is conversation of soil important ? Suggest three different ways of soil conversation.
Conservation of soil is essential for agriculture. It helps in maintaining the food security of the world.
Soil is necessary for water supply. It can provide nutrients to plants.
Three ways of soil conservation are -
(i) By encouraging terrace farming and contour ploughing.
(ii) By promoting afforestation.
(iii) By controlling overgrazing by animals.
*Do not throw plastic bags all polythene bags waste pollutants into soil.
*Plant more trees.
*Keep always your surrounding environment clean.
*Do not use more and more fertilizers or insecticides in fields.
E.
1.Explain weathering. Mention the factors that effect the rate of weathering and soil erosion.
The term weathering refers to the process that breaks rocks into smaller particles. It includes erosion and deposition .They disintegrate as they are exposed to all types of weather changes.
The rate at which erosion takes place depends upon the temperature of a place , vegetation cover, rainfall , slope of the land , type of soil and changes in land use.
2. Explain the formation of soil with the help of a labelled diagram.
Soil is the thin layer of material covering the earth’s surface and is formed from the weathering of rocks. It is made up mainly of mineral particles, organic materials, air, water and living organisms—all of which interact slowly yet constantly.
Factors affecting formation of soil may be atmospheric, such as changes in temperatures and pressure; erosion and transportation by wind, water and glaciers; chemical action such as crystal growth, oxidation, hydration, carbonation and leaching by water, especially rainwater, with time.
So in general,formation of soil takes place by two methods:☆Physical disintegration of rocks
☆Chemical decomposition of rocks
3. What are the major soil types found in India ? Give one important characteristic of each.
The major soil types found in India
Alluvial soil - It is very fertile and forms major agricultural land of our country.
Black soil - This soil has an ability to retain moisture and become sticky when wet.
Red soil - It is highly porous, fine grained and deep.
Laterite soil - It is formed by the leaching process.
4. Describe the journey of a river from its source to its mouth.
In the early stage, the river is young. It flows over steep mountains where its rate of erosion is maximum.
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. This large deposition helps in the formation of a delta .
This delta of Ganga and Brahmaputra is the largest in the world.
5. Why is conversation of soil important ? Suggest three different ways of soil conversation.
Conservation of soil is essential for agriculture. It helps in maintaining the food security of the world.
Soil is necessary for water supply. It can provide nutrients to plants.
Three ways of soil conservation are -
(i) By encouraging terrace farming and contour ploughing.
(ii) By promoting afforestation.
(iii) By controlling overgrazing by animals.
*Do not throw plastic bags all polythene bags waste pollutants into soil.
*Plant more trees.
*Keep always your surrounding environment clean.
*Do not use more and more fertilizers or insecticides in fields.
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