DAV Class 7 SST Chapter 2 Question Answer – The Earth and the Changes on It

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DAV Class 7 SST Ch 2 Question Answer – The Earth and the Changes on It

DAV Class 7 SST Ch 2 Solutions – The Earth and the Changes on It

Something To Know

A. Tick (✓) the correct option.

Question 1.
Which one of the following is not a human activity?
(a) Diverse land use
(b) Cleaning of forests
(c) New human settlements
(d) Formation of mountains
Answer:
(d) Formation of mountains

Question 2.
Which one is a Continental glacier?
(a) Siachin
(b) Antarctica
(c) Gangotri
(d) Yamunotri
Answer:
(b) Antarctica

Question 3.
Which of the following features are formed by a river?
(a) V’ shaped valley, meander and delta
(b) TJ’ shaped valley, meander and delta
(c) T shaped valley, cliff and delta
(d) V’ shaped valley, meander and sand dunes
Answer:
(a) V’ shaped valley, meander and delta

Question 4.
Which layer of the soil contains humus?
(a) Bedrock
(b) Weathered rock
(c) Subsoil
(d) Topsoil
Answer:
(d) Topsoil

Question 5.
Which soil type is capable of retaining moisture and becomes sticky when wet?
(a) Alluvial soil
(b) Black soil
(c) Red soil
(d) Laterite soil
Answer:
(b) Black soil

B. Fill in the blanks.

1. Organic matter when gets decomposed in the soil converts it into dark-coloured material is called ……………
2. …………… soil is found in a large part of our country.
3. ………….. and ……………. valleys are formed at the youthful stage of a river.
4. A …………… is a steep-sided rock facing the sea.
5. …………. river and ………….. river form the largest delta of the world.
Answer:
1. humus
2. Alluvial
3.‘I’shaped; V’ shaped
4. cliff
5. Ganga; Brahmaputra

C. Give a single term for each of the following statements.

Question 1.
Mounds of sand deposited by wind action in deserts.
Answer:
Dunes.

Question 2.
The process in which a gradual wearing and carrying away of soil particles takes place on the earth’s surface.
Answer:
Erosion.

Question 3.
The process of laying down of sediments carried by various agents of gradation.
Answer:
Deposition.

Question 4.
A mass of moving ice down the slope.
Answer:
Glacier.

Question 5.
Removal of the top layer of soil.
Answer:
Soil erosion.

D. Answer the following questions in brief.

Question 1.
Specify two differences between internal and external forces.
Answer:
Internal Forces. These forces are active inside the earth and are very fast and sudden. They bring radical changes and are easily visible. Example: earthquake. External Forces. These forces are active on the surface of the earth and are very slow. They take place gradually over a very long time. They could be due to natural forces such as carrying of soil by rain water, changes in the course of river, winds carrying soil particles with them, etc.

Question 2.
Name the various agents of gradation.
Answer:
Running water, glacier, wind and sea waves.

Question 3.
Distinguish between transported and residual soil.
Answer:
The weathering process breaks the rocks into small particles. These are then carried away by water, wind, etc., and later get deposited at a new place. Such soil is called transported soil. But, when a soil is formed by the weathering of a parent rock and remains present on the same site, it is called residual soil.

Question 4.
How is a delta formed?
Answer:
The river deposits silt, sand and sediments over a large area near its mouth. This large deposition helps in the formation of a delta.

Question 5.
Why is humus formed more rapidly in humid areas?
Answer:
Humus is more rapidly formed in humid areas due to heavy growth of plants and rich animal life.

E. Answer the following questions.

Question 1.
Explain weathering. Mention the factors that affect the rate of weathering and soil erosion.
Answer:
Weathering refers to the process that breaking rock into smaller particles. It includes erosion and deposition. They disintegrate as they are exposed to all types of weather. One factor that influences the rock at which rocks will weather is their degree of exposure to the atmosphere. Another factor is the composition of rocks. Also climate is another factor that plays an important role in the rate of weathering. Agents of gradation like running water, wind, moving ice, sea waves affect the rate of soil erosion.

Question 2.
Explain the formation of soil with the help of a labeled diagram.
Answer:
Soil formation is a very slow process. It takes thousands of years to form a thin layer of soil. The weathering process breaks the rocks into small particles. These are then carried away by water, wind, etc. and later get collected at another place. Also soil is formed by the weathering of a parent rock and remains present on the same site.

The soil-forming process continues over a long span of time. It starts developing in lavers, one over the other. These layers are called horizons. From bottom to top, the lowest horizon is called bedrock, then comes the horizon of weathered rock and it is followed by the subsoil and topsoil.

Question 3.
What are the types of major soils found in India? Give one important characteristic of each.
Answer:
The major types of soils found in India are –

• Alluvial Soil: This soil 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 and Yellow Soil: This soil is highly porous, fine grained and deep. It is red in colour due to the presence of iron particles. It looks yellow when it occurs in a hydrated form.
• Laterite Soil: This soil develops under tropical and subtropical climate with alternate wet and dry season. It is found in the regions of heavy rainfall.

Two other types of soils are:

• Arid or Desert Soil: This soil is generally sandy in texture and saline in nature.
• Forest and Mountainous Soil: This soil is found in the hilly and mountainous areas where sufficient rain forests are available.

Question 4.
Describe the journey of a river from its source to its mouth.
Answer:
A river covers a long journey from its source to mouth. It takes birth in a mountain or hill, becomes larger where it is met by a number of tributaries and flows over plains and finally ends when it reaches the sea. The river’s journey is divided into three stages. In its first or early stage, it is young. It flows over steep mountains where its rate of erosion is maximum. It forms striking youthful features like T-shaped and V’ shaped valleys, waterfalls, etc.

Now, the river enters into the plains. Here starts its second stage, i.e. the stage of maturity. The volume of water increases and the slope of land decreases, resulting in slow speed of the river. During this stage, the river is said to flow through meanders. 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.

Question 5.
Why is the conservation of soil important? Suggest three different ways of soil conservation.
Answer:
Conservation of soil is important because soil formation is a very slow process. It takes thousands of years to form a thin layer of soil.
Different ways for soil conservation are –

• Plantation of trees;
• Selective agricultural practices like crop rotation and multiple cropping methods.
• Development and management of pasture lands.
• Need to spread awareness among local people so that they could adopt these practices.

Value-Based Question

Agriculture is the main source of livelihood in India. It depends on the fertility of the soil. When soil erodes, it makes the land less productive and lead to landslides, floods and destroys the habitat of micro-organism. Wrong agricultural practices, deforestation for the expansion of agriculture, industrialization, and construction of roads and railway lines are some of reasons of this menace.

Question 1.
What will be the aftereffects of this menace?
Answer:
(i) Content of organic matter and other nutrients of soil decrease, and as a result, soil structure gets impoverished.
(ii) The ability of land to supply moisture for plant growth is reduced, and due to these bad effects, yield are lowered.
(iii) The wind-borne sand encroaches the arable land and makes them infertile. Crops damaged due to sand storms.

• Soil erosion in catchment areas of streams due to deforestation and other natural and man-made activities leads to silting of streams and reservoirs. This reduces the capacity of these water bodies to carry large volumes of water.
• Due to many of the reasons behind soil erosion, trees and plants will be less day to day.

Question 2.
In your opinion, which one of the reasons mentioned above is justified?
Answer:
Try to give an answer yourself.

Map Skill

Take an outline map of India. Locate and label the areas of major soil types on it. Mention the names of states of each soil type.
Answer:

Alluvial soil is found in northern plains including states of Punjab, Haryana, Uttar Pradesh, Bihar, West Bengal, etc. Black soil is found mostly in the Deccan trap region, Maharashtra, Gujarat, Karnataka, etc. Red and yellow soil is found mostly in Jharkhand, Odisha, Arunachal Pradesh, Nagaland, Mizoram, Andhra Pradesh, Telangana, Tamil Nadu and Karnataka.

Laterite soil is basically found in southern states such as Tamil Nadu, Andhra Pradesh and Kerela, Western Ghats of Maharashtra, Odisha, some of the regions of West Bengal and north-eastern regions. Forest and Mountainous soil is found mainly in Jammu and Kashmir and Ladakh (both union territories), Himachal Pradesh, Uttarakhand, Sikkim, some parts of Arunachal Pradesh and Meghalaya. Arid or Desert soil is basically found in west of Rajasthan, Haryana and south of Punjab.

Something To Do

Question 1.
Complete the table by writing appropriate features in relevant columns.
Answer:

Agents	Features formed by Erosion	Features formed by Deposition
Running Water	Meanders	Delta
Wind Action	Rocks	Sand dunes
Sea Waves	Cliffs	Beaches
Moving Ice	Frozen rivers	Glacier

Question 2.
Collect pictures of various features formed by various agents of gradation and weathering. Paste these pictures in a scrap file.
Answer:
1 and 2 – Do it yourself.

DAV Class 7 Social Science Chapter 2 Question Answer – The Earth and the Changes on It

A. Tick (✓) the correct option.

Question 1.
External processes which bring changes on the earth’s surface do not include
(a) weathering
(b) erosion
(c) volcanic activities
(d) building of dams
Answer:
(c) volcanic activities

Question 2.
The term weathering refers to
(a) gradual wearing and carrying away loose particles of rocks
(b) breaking of rocks into smaller particles
(c) laying down of sediments by carrying them from a distant land
(d) leveling of land
Answer:
(b) breaking of rocks into smaller particles

Question 3.
The rate at which weathering and erosion take place depends upon the
(a) the temperature of a place
(b) the slope of the land
(c) the slope of the land
(d) All of the above
Answer:
(d) All of the above

Question 4.
On the plains, the volume of water increases and the slope of the land decreases. As a result the speed of the river
(a) becomes normal
(b) becomes very fast
(c) becomes very slow
(d) plateaus
Answer:
(c) becomes very slow

Question 5.
Sand dunes are found in
(a) plain areas
(b) desert areas
(c) hilly areas
(d) plateaus
Answer:
(b) desert areas

Question 6.
The most suitable soil for large-scale agricultural activities is the
(a) black soil
(b) alluvial soil
(c) laterite soil
(d) arid soil
Answer:
(b) alluvial soil

B. Very Short Answer Type Questions

Question 1.
Mention any two human factors that bring changes on the earth’s surface.
Answer:
The two human factors that bring changes on the earth’s surface are-

• cutting down of forests
• large-scale mining.

Question 2.
What is the effect of weathering on stone monuments and buildings?
Answer:
The pieces of stone get flaked off and iron railings get rusted.

Question 3.
What is the difference between aggradation and degradation?
Answer:
Agradation means adding of sediments and raising the level of land. Degradation means breaking and wearing away of sediments and lowering the level of land.

Question 4.
What are the agents of gradation?
Answer:
The agents of gradation are running water, wind, moving ice and sea waves.

Question 5.
Mention two features of weathering and erosion.
Answer:

• They take place together.
• They occur everywhere and all the time.

Question 6.
Where are glaciers found in India?
Answer:
In India, glaciers are found on high altitudes of the Himalayas where the temperature is below freezing point.

Question 7.
In which regions is the action of the wind most common?
Answer:
The action of the wind is most common in desert regions.

Question 8.
Name the Indian state where sand dunes can be found.
Answer:
Rajasthan.

Question 9.
What is soil made of?
Answer:
The soil is made up of organic and inorganic particles.

Question 10.
How is humus good for the soil?
Answer:
The humus present in the soil contributes to the fertility of the land.

Question 11.
Where are the organic particles derived from?
Answer:
The organic particles are derived from plants, dead remains of animals and bacteria.

Question 12.
Where are the inorganic particles derived from?
Answer:
The inorganic particles are derived from rocks.

Question 13.
What is black soil also known as? Why?
Answer:
Black soil is also known as cotton soil because it is largely used for growing cotton.

Question 14.
What is soil erosion?
Answer:
The removal of top fertile soil cover due to various reasons like wind, glaciers and water is called soil erosion.

Question 15.
Name two forces that bring sudden changes inside the earth.
Answer:
Internal forces and external forces.

Question 16.
What do you understand by the term external force?
Answer:
Any process working on the earth’s surface and bringing change on it, is called external force.

Question 17.
Name the agents that are responsible for soil erosion.
Answer:
Running water, wind, moving ice and sea waves.

Question 18.
Give an example each of continental and mountain glaciers.
Answer:
Continental Glaciers – Antarctica and Greenland.
Mountain Glacier – Siachin Glacier of Himalayas in India.

C. Short Answer Type Questions

Question 1.
What changes are noticed in a river when it enters into the plains?
Answer:
When a river enters the plains, it comes to the stage of maturity. Here, the volume of water increases and the slope of land decreases. As a result, the speed of the river becomes slow. During this stage, the river is said to flow through meanders. Before meeting the sea, the river becomes large and sluggish and gets divided into several distributaries.

Question 2.
How are sand dunes formed?
Answer:
In the desert regions, the land is exposed to strong wind. The strong wind has the capacity to rub and scrap rocks, resulting in strange-shaped rocks. Whenever the speed of the wind slows down due to some obstruction. The carried material is then deposited at a new place. This forms various types of sand dunes.

Question 3.
Name the factors on which the rate of weathering and soil erosion depends.
Answer:
The factors on which the rate of weathering and soil erosion depends are –

1. Temperature of place
2. Vegetation cover
3. Rainfall
4. The slope of the land
5. Type of soil
6. Changes in land use

D. Long Answer Type Questions

Question 1.
Give an account of the four types of soil found in India.
Answer:
Four types of soil:
(a) Alluvial Soil. This type of soil is found over a large part of the country. It is mainly formed by the work of a river. It is highly fertile. Therefore, regions of this soil are intensively cultivated and thickly populated.

(b) Black Soil. It is black in color. It is also known as cotton soil because it is ideal for growing cotton. It is found in Deccan Plateau and is confined to some parts of Gujarat, Maharashtra and Karnataka. It is made of extremely fine (clayish) material that has the capacity of holding moisture.

(c) Red and Yellow Soil. It is red in color due to the presence of iron particles. It is confined to peninsular India and some patches of the northeastern part of India. It is highly porous, fine-grained and deep. It looks yellow when it occurs in a hydrated form.

(d) Laterite Soil. It is found over the hill slopes of peninsular plateaus. The regions of heavy rainfall are rich in this type of soil. It looks yellow when it occurs in a hydrated form.

Question 2.
How do changes take place slowly on the earth’s surface?
Answer:
Changes on the earth’s surface take place slowly because the processes like weathering, erosion, transportation, and deposition are very slow ones and take place gradually over a very long time. Just take the example of erosion. It is a gradual wearing and carrying away of all those loose particles of disintegrated rocks which lie exposed on the earth’s surface by agents of gradation like running water. The river deposits silts, sand and sediments over a large area near its mouth. This large deposition helps in the formation of a delta.

Question 3.
Explain the important role played by human beings in changing the face of the earth’s surface.
Answer:
Human beings have been changing the face of the earth’s surface in a very drastic way. Our population is increasing very fast. The rate of industrialization is also very fast. These two factors have disturbed the natural environment to a great extent. To meet the needs of the growing population, human beings are clearing forests.

This provides them a temporary solution. They get agricultural land and produce crops of different varieties. They also use land for the construction of roads and for new human settlements. These human activities change the land surface. It is important that development makes minimum disturbance over land surface and an ecological balance is maintained.