STD VII

HOW SURFACE LANDFORMS CHANGE

Q1. What is denudation?

A1.Weathering,erosion and transportation of

the surface, there by laying bare the underlying

rocks, is known as denudation .

Q2. What is a gorge?

A2. A deep and narrow 'v-shaped' valley is

called a gorge.

*It is formed by the river in the upper course,

where erosion is more on the bed , than on the

sides.

Q3. What is humus ? How does it improve the

quality of soil?

A3. Humus is an organic substance or matter

,derived from decomposed plants and animals.

Its presence in soil make the soil fertile, as it

add nutrients to the soil thus making the soil

fertile.

Q4. Define erosion.

A4. Weathering, followed by transportation of

the weathered materials by agents like water ,

wind, ice ,sea is called erosion.

Q5. What are the chief functions of a river in its

middle course?

A5. The main functions of a river in its middle

course are deposition, resulting in features like

meanders ,flood plain , 'u shaped ' valleys.

Q6. What is a flood plain?

A6. Flood plain is a depositional feature of the

the rivers in their middle course.

*This area is very fertile due to the alluvium

deposits.

Q7. Name two types of landforms formed by

the action of winds.

A7. *Mushroom rocks.

*Sand dunes.

Q8. What is marine erosion ?

A8. Weathering , transportation and deposition

along the coast ,resulting in features like sea

cliffs , sea arches, is known as marine erosion

*landforms created due to marine erosion*

Q9. What is weathering ? How does it differ

from erosion ?

A9. The process that causes changes in the

landforms , involving only breaking down of

rocks is called as weathering while erosion

includes weathering as well as transportation

and deposition.

Q10. Mention the chief functions of rivers in it's

upper course.

A10. In the upper course, river flows down the

slope and has great power to break(

weathering) and transport large fragments of

rocks.

*Some important physical features formed by

the river in its upper course are v-shaped

valleys, waterfalls, gorges , cascades.

Q11. Which type of valleys are formed by the

glaciers and why ?

A11. Valleys formed by the glaciers are

'ushaped'. This is because-

*The heavy ice erodes both, the sides as well as

the bottom of the valley and so the bottom

becomes flat and the sides become steep. Thus

forming a 'u-shaped' valley.

Q12. What is moraine ?

A12. A pile of rocks deposited by glaciers is

called a moraine.

A13. What is loess?

A13. When the wind carries fine dust particles

of soil and deposit them in distant regions and

gradually this deposit grows to form a thick

layer of fertile soil, its called a loess.

Eg. Soil present in Northern China.

Q14. What are the factors that infuence the

rates of weathering and erosion?

A14. The factors influencing the rate of

weathering and erosion are -

1. Range of temperature.&

2. High humidity

Q15. Explain the formation of a delta.

A15. The region near the mouth of the river ,

comprising a network of distributaries forming

a triangular shape, is called a delta.

2. It is formed when mounds of deposits ,block

the river course and to overcome this obstacle

,the river water gets distributed into several

small channel known as distributaries.

*This region, near river's mouth is called delta.

Eg. Sunderban delta.

Q16. Give reasons why the action of wind is

more prominent in dry regions.

A16. The action of wind is more prominent in

arid and semi-arid regions because-

1.In this region, the wind is dry and light and

hence flows at a great speed , eroding and

carrying away the materials.

2. Wind flows freely without any hindrance as

these areas lack vegetation.

Q17. Why is soil conservation necessary?

Mention some ways to prevent soil erosion.

A17. Soil conservation is necessary because it is

one of the important resource on which life

depends and secondly the process of soil

formation takes a very long time ,but soil can

be eroded in a few years if it is not protected.

Some ways to prevent soil erosion are -

1. Afforestation.

2. Preventing overgrazing.

3.Practicing terrace farming, crop rotation ,

building of bunds.

Q18. Erosion by river is more prominent in

mountains than in plains. Why?

A18. In the mountains, river flows down the

slopes and aquires great velocity, thus has the

capacity to erode and transport much more

than the rivers in the middle and lower course.

Q19. Why are flood plains densely populated?

A19. Flood plains formed in the middle coarse

of the river have the highest deposits of

alluvium which make the plains very fertile.

Also ,the easy accessibility of water in these

areas have led to the development of towns

and cities.

Thus, the areas are densely populated.

Q20.How can deltas be developed into a tourist

destination?

A20. This can be done by-

1. Developing them into water parks.

2.Developing them as outdoor adventure park.

3. Developing them as wildlife sanctuaries or

national parks.

Q21. Give another name of crescent shaped

dune. A21. Barkhan.

Q22. Which rivers form the largest delta in the

world?

A22. Ganges and Brahmaputra form the largest

delta in the world, the Sunderban delta.