NCERT Solutions for Class 11 Geography (Fundamental of physical geography) Chapter 5 Geomorphic Processes

NCERT
SOLUTIONS
CLASS - 11th

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Class : 11th

Subject : Geography

Chapter : 6

Chapter Name : Geomorphic Processes

Q1 Multiple Choice Questions

(i) Which one of the following processes is a gradational process?

(a) Deposition (c) Volcanism

(b) Diastrophism (d) Erosion

(ii) Which one of the following materials is affected by hydration process?

(a)Granite (c) Quartz

(b) Clay (d) Salts

(iii) Debris avalanche can be included in the category of:

(a) Landslides (c) Rapid flow mass movements

(b) Slow flow mass movements (d) Subsidence

i-(d) Erosion

ii-(b) Clay

iii-(c) Rapid flow mass movements

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Book : Fundamental of Physical Geography Ncert Solutions | Chapter - 6 Social Science Geography

Page : 54 , Block Name : Exercises

Q2 Answer the following questions in about 30 words.

(i) It is weathering that is responsible for biodiversity on earth. How?

(ii) What are mass movements that are real rapid and perceptible? List.

(iii) What are the various mobile and mighty exogenic geomorphic agents and what is the prime
job they perform?

(iv) Is weathering essential as a pre-requisite in the formation of soils? Why?

(i) Bio-diversity depends on forest and forest depends upon weathering mantles.

(ii) Landslides are mass movements that are rapid and perceptible. These include slump, debris
slides and rockslides.

(iii) Weathering, mass movements and erosion, transportation and deposition are the main
exogenic geomorphic agents. Their primary job is of denudation.

(iv) Soil formation depends first on weathering. It is this depth of the weathered material, which
is the primary input for soil to form.

Page : 54 , Block Name : Exercises

Q3 Answer the following questions in about 150 words.

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(i) Our earth is a playfield for two opposing groups of geomorphic processes.”Discuss.

(ii) Exogenic geomorphic processes derive their ultimate energy from the sun’s heat. Explain.

(iii) Are physical and chemical weathering processes independent of each other? If not, why?
Explain with examples.

(iv) How do you distinguish between the process of soil formation and soil forming factors? What
is the role of climate and biological activity as two important control factors in the formation of
soils?

(i) The earth’s crust is dynamic. All changes take place under the influence of certain forces
working continuously within the earth as well as over the surface of the earth. The external
forces are known as ​exogenic forces ​and the internal forces are known as ​endogenic forces​.
The actions of exogenic forces result in wearing down (degradation) of relief/elevations and
filling up (aggradation) of basins/depressions, on the earth’s surface. The phenomenon of
wearing down of relief variations of the surface of the earth through erosion is known as
gradation​. It may be sudden forces like earthquakes, volcanoes, etc. in general, the endogenic
forces are mainly land hurtling forces and exogenic forces are mainly land wearing forces.

(ii) Exogenic forces act on the surface of the earth. All exogenic forces such as weathering and
denudation derive their energy from the sun. Sunlight causes air to move, water to evaporate,
and ocean waves to rise. These moving fluids like water, wind and waves, etc., attack the solid
surface, eroding it , carrying the broken pieces far away, and depositing them to fill low places in
the landscape. Weathering is a process of the breaking of rocks by static agents of weather. In
this process, the rocks are disintegrated by physical forces and decomposed by chemical
action. Agents of physical weathering such as insulation, frost, etc. wholly depend upon energy
derived from the sun. The agents of denudation like river, glaciers, wind, sea waves, etc also
derive their energy from the sun.

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Book : Fundamental of Physical Geography Ncert Solutions | Chapter - 6 Social Science Geography

(iii) Weathering is the action of elements of weather and climate over earth materials. Physical
and chemical weathering processes aren’t independent of each other, rather work of agents of
physical and chemical weathering are interdependent. Chemical weathering is brought about by
oxidation, carbonation, hydration and solution. The agents of physical weathering, like unloading
and expansion, temperature changes and expansion, freezing, thawing and salt weathering,
easily break these decayed and decomposed rocks. Chemical weathering depends upon the
work of physical weathering because physical weathering prepares ground for agents of
chemical weathering to work. For example, agents of physical weathering like variation in
temperature, freezing thawing and frost wedging, salt weathering, etc… breaks the rocks and
agents of chemical weathering can easily work on them.

(iv) Soil is a dynamic medium in which many chemical, physical and biological activities go on
constantly. The soil formation begins with the breaking down of rocks into small pieces by
various agents of weathering and erosion. It contains a mixture of minerals. This rock material
contains a mixture of minerals. Later on, decaying plant remains are mixed in it. This is known
as humus and forms organic part of the soil. Animals and insects with microorganisms like
bacteria also forms organic matter.

Soil holds water, which provides life to plants and trees. Plant roots penetrate down, burrowing
animals bring up particles, mass of material becomes porous and sponge-like with a capacity to
retain water and to permit the passage of air and finally a mature soil, a complex mixture of
mineral and organic products forms. Thus, soil is the final product of the interactions between
the weathering of underlying rock, the climate, plants and the activities of millions of insects and
microorganisms. All these physical, chemical and biological act as soil-forming Factors

Five basic factors that control the formation of soils: (i) parent material (ii) topography (iii)
climate (iv) biological activity (v) time.

The role of the climate and biological activity are as follows:

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→​The climate of an area is a major active factor in soil formation. The climate elements that are
responsible for soil forming are-Moisture and temperature.Both of them affects the chemical and
biological activities. Excess of water due to moisture helps in eluviation and illuviation. In
regions with humidity minerals like magnesium, sodium, silica are removed from the soil.
Whereas in areas with high temperature water evaporates leaving behind salt in the soil.

→​Biological activity includes the effect of vegetation, bacteria, and animals. The vegetative cover

and organisms helps in adding organic matter, nitrogen, moisture retention etc. . Dead plants
provide humus, which increases soils’ fertility. Bacteria like Rhizobium helps in nitrogen fixation
by changing nitrogen from air into chemical form, Burrowing animals like ants, rodents,etc. also
helps in mixing air, water and minerals by reworking the soil.

Page : 54 , Block Name : Exercises

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