DAV Class 7 SST Solution Chapter 2 The Earth and the Changes on It
DAV School Books Class 7 SST Solution Chapter 2 The Earth and the Changes on It all Question Answer. DAV Class 7 2nd Chapter The Earth and the Changes on It full Chapter explanation by expert teacher.
DAV School Books Class 7 SST Solution Chapter 2 The Earth and the Changes on It:
(A) Tick the correct option –
(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
Ans: (d) Formation of mountains
(2) Which one is a Continental glacier?
(a) Siachin
(b) Antarctica
(c) Gangotri
(d) Yamunotri
Ans: (b) Antarctica.
(3) Which of the following features are formed by a river?
(a) ‘V’ shaped valley, meander and delta
(b) ‘U’ shaped valley, meander and delta
(c) ‘I’ shaped valley, cliff and delta
(d) ‘V’ shaped valley, meander and sand dunes
Ans: (a) ‘V’ shaped valley, meander and delta.
(4) Which layer of the soil contains humus?
(a) Bed rock
(b) Weathered rock
(c) Sub soil
(d) Top soil
Ans: (d) Top soil
(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
Ans: (b) Black soil.
(B) Fill in the blanks.
(1) Organic matter when gets decomposed in the soil and converts it into dark coloured material is called _____.
Ans: Humos.
(2) _______ soil is found in a large part of our country.
Ans: Alluvial Soil.
(3) _______ and _______ valleys are formed at the youthful stage of a river.
Ans: ‘I’ Shaped, ‘V’ Shaped.
(4) A _______ is a steep sided rock facing the sea.
Ans: Cliff.
(5) ________ river and ______ river form the largest delta of the world.
Ans: Ganga, Brahmaputra.
(D) Answer the following questions in brief –
(1) Specify two differences between internal and external forces.
Ans: Two differences between external and internal forces are-
(i) External forces take much time to bring the changes on the earth surface rather internal forces are sudden and make sudden effects.
(ii) forces created by volcanic eruptions and earthquake are called internal forces, while forces created by river water, wind etc. Are called external forces.
(2) Name the various agents of gradation.
Ans: The various agents of gradation are- running water, glacier, wind and sea waves.
(3) Distinguish between transported and residual soil.
Ans: Distinction between transported and residual soil –
When the broken rocks’ particles created by the weathering process, carried away by the natural agents like wind, river etc. And deposited into a new place are called transported soil. But the residual soils remain present with the parent rock.
(4) How is a delta formed?
Ans: Formation of delta –
Delta is formed at the old stage of the river by its depositional process. At the meeting point of river to the sea deposition of silt, sand and sediments in a large amount creates delta.
(5) Why is humus formed more rapidly in humid areas?
Ans: Human is formed more rapidly in the humid areas because rich varieties of animals and plants are found in the humid areas. To form the human decomposed particals of dead animals and plants needed.
(E) Answer the following questions –
(1) Explain weathering. Mention the factors that affect the rate of weathering and soil erosion.
Ans: Weathering is one of the processes of external factors to bring changes on the earth. Braking down of stone into smaller particals due to different kinds of weather changes is called weathering. Factors that affect the weathering and soil erosion are force of water and wind, human activities, rapid cutting of trees, animal over grazing etc.
(2) Explain the formation of soil with the help of a labelled diagram.
Ans: Soil formation- Soil can be formed by two procedure -transported soil and residual soil. It takes thousand of years to make a single thin layer of soil. The broken rock’s particals created by the weathering process, carried away by the natural agents like wind, river etc. and deposited into a new place are called transported soil. On the other hand, in the case of residual soil the residual soils particals remain present with the parent rock. After formation the layers of the soil are called horizon. Three layers can be found including Top soil, weathered rock and bed rock.
(3) What are the major soil types found in India? Give one important characteristic of each.
Ans: Major soil types –
(i) Alluvial soil – Found mainly in the coastal and northern plain by the process of deposition of the river. It is the most fertile soil.
(ii) Black Soil – sticky in nature for retaining moisture and best for the growth of cotton. Another name of black soil is cotton soil.
(iii) Red soil – reach in iron, much poro, fine grained and deep .
(iv) laterite soil – can be found in the heavy rainfall region and formed by leaching process.
(4) Describe the journey of a river from its source to its mouth.
Ans: Journey of a river- rivers take birth from the mountain .At her young age due to the steep edges of the mountains it does lots of erosion and creates V,I shaped valleys waterfalls etc. After entering to the plain area the speed becomes slow due to decreased land slope. Here it has to flow through meanders. When the river is about to meet the sea is called the old-age of the river. Here maximum distributaries are created after getting distracted from the main stream. Most of the depositional work can be found at this stage of the river and hely to form delta.
(5) Why is conservation of soil important? Suggest three different ways of soil conservation.
Ans: Conservation of soil is important because soil erosion can affect all the land of the whole world. Again by conserving the soil we can increase the soil fertility to help to yield high yielding crops.
Three different ways of soil conservation are-
(i) Tree plantation and stop reckless cutting of trees.
(ii) Proper animal husbandry and stop animal over grazing.
(iii) Spread proper awareness by the government.
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