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.