RBSE Solutions for Class 11 Physical Geography Chapter 9 Denudation

Rajasthan Board RBSE Class 11 Physical Geography Chapter 9 Denudation

RBSE Class 11 Physical Geography Chapter 9 Text Book Questions

RBSE Class 11 Physical Geography Chapter 9 Multiple Choice Questions

Question 1.
Spatial disintegration and decomposition of rocks is called:
(a) Denudation
(b) Erosion
(c) Weathering
(d) Solution
Answer:
(c) Weathering

Question 2.
What is Denudation?
(a) Erosion and Transportation
(b) Erosion and Deposition
(c) Erosion, Weathering and Mass Translocation
(d) Erosion and Dissolution
Answer:
(c) Erosion, Weathering and Mass Translocation

Question 3.
The process of Exfolation takes place in the regions where:
(a) Annual range of temperature is high
(b) Temperature is high
(c) Temperature is low
(d) Daily range of temperature is high
Answer:
(d) Daily range of temperature is high

Question 4.
In which region is the process of chemical weathering more active?
(a) Tropical and Arid
(b) Polar region
(c) Tropical and Humid
(d) Cold and Humid
Answer:
(c) Tropical and Humid

Question 5.
Translocation of massive rock debris along the slope by gravitational force is called:
(a) Weathering
(b) Erosion
(c) Mass Translocation
(d) Transportation
Answer:
(c) Mass Translocation

RBSE Class 11 Physical Geography Chapter 9 Very Short Answer Type Questions

Question 1.
Which type of weathering is oxidation?
Answer:
Oxidation is a type of chemical weathering in which atmospheric oxygen dissolves in water to change rock minerals into oxides.

Question 2.
What does erosion mean?
Answer:
Erosion is a dynamic process in which rocks keep on disintegrating by being rubbed, eroded, trans – located and transported through glaciers, underground water, waves, wind and rivers.

Question 3.
Where does attrition take place, in weathering or in erosion?
Answer:
The process of attrition takes place in erosion. In this process, the rock fragments or particles being carried by wind, river or sea waves smash together and break into smaller particles.

Question 4.
Which type of weathering is block disintegration?
Answer:
Block Disintegration is a type of physical weathering, in which cracks occur in the rocks and they disintegrate due to extreme daily range of temperature.

Question 5.
Which type of weathering is Carbonation?
Answer:
Carbonation is a type of chemical weathering in which the atmospheric carbon – dioxide gas dissolves in water to form carbonic acid, which in turn erodes lime rocks rapidly.

RBSE Class 11 Physical Geography Chapter 9 Short Answer Type Questions

Question 1.
Explain the meaning of denudation in brief.
Answer:
The process by which the cover of rocks of the crust is eroded, is called denudation. This process enables the leveling of different land forms created by endogenetic forces. In this, after the fragmentation of uplifted landmass, its transportation, erosion, attrition and mass translocation take place. Eventually, by these processes, the uplifted terrain transforms into the lower terrain.

Question 2.
Write the types of weathering.
Answer:
Weathering is a spatial process, in which the rocks disintegrate and decompose at their own place. Mainly, there are three types of weathering:

1. Physical Weathering:
It is further classified into Block Disintegration, Exfolation, Frost Weathering and Pressure Release.

2. Chemical Weathering:
This type of weathering is further classified into Oxidation, Carbonation, Desilication, Hydration and Dissolution.

3. Biological Weathering:
This type of weathering is classified into weathering by vegetation, weathering by animals and weathering by humans.

Question 3.
What is Plucking?
Answer:
Water of glaciers uproots the rock fragments coming in their way and carries them along, this process is called Plucking. The process of plucking takes place in glacial regions.

Question 4.
What do you understand by Corrosion?
Answer:
By the chemical action of water, when the minerals of rocks dissolve in water and flow away, it is called Corrosion. This process of corrosion promotes the process of erosion.

Question 5.
Explain Physical Weathering.
Answer:
Physical Weathering:
Process of disintegration in the rocks by insolation, frost, water and wind is called Physical Weathering. The process of physical weathering is classified into the following parts:

1. Block Disintegration:
In this type of process, due to extreme daily range of temperature, cracks occur in the rocks and they disintegrate into large pieces.

2. Exfolation:
Breaking of rocks in the form of shells when the upper layer of rocks remain heated and the inner layers cool down.

3. Frost Weathering:
In extreme cold regions, the breaking down of rocks due to freezing and melting of water in the cracks of rocks on regular basis.

4. Pressure Release:
When the removal of upper rocks reduces the pressure on the lower rocks, then cracks start appearing in the rocks. This process is called Pressure Release.

RBSE Class 11 Physical Geography Chapter 9 Essay Type Questions

Question 1.
Explain the meaning of weathering and the main types of weathering in detail.
Answer:
Weathering is a spatial process in which the rocks break down by disintegration and decomposition at their own place.

Types of Weathering:
The process of weathering takes place in various forms. Considering the various components as the basis, weathering is classified into the following types:

1. Physical Weathering:
Process of disintegration in the rocks by insolation, frost, water and wind is called Physical Weathering. It has the following types:

(a) Block Disintegration:
In hot desert regions, cracks occur in the rocks due to extreme daily range of temperature. Over time/these rocks disintegrate into large pieces.

(b) Exfolation:
Breaking of rocks in the form of shells when the upper layer of rocks remain heated and the inner layers cool down.

(c) Frost Weathering:
In extreme cold regions, the breaking down of rocks due to the freezing and melting of water in the cracks of rocks on regular basis.

(d) Pressure Release:
When the removal of upper rocks reduces the pressure on the lower rocks, then the cracks start appearing in the rocks.

2. Chemical Weathering:
When the rocks break, dissolve, decay and change into new compounds by the action of water and gas in a chemical process , it is called Chemical Weathering. It is classified into the following parts:

(a) Oxidation:
The atmospheric oxygen dissolves in water to change rock minerals into oxides by which decomposition of the rocks takes place.

(b) Carbonation:
The atmospheric carbon – dioxide gas dissolves in water to form carbonic acid by which the lime-rocks dissolve.

(c) Desilication:
Process of separation of silica from rocks.

(d) Hydration:
Absorption of water in rock minerals is called Hydration. Rocks scatter by the process of absorption of water.

(e) Dissolution:
Rainwater dissolves many types of acids and carbonic elements in the rock-materials and creates new chemical compounds. This reaction is called Dissolution.

3. Biological Weathering:
Biological weathering is the weakening and subsequent disintegration of rock by vegetation and living organisms. It has the following types:

(a) Weathering by vegetation:
Roots of trees enter into the rocks and disintegrate them.

(b) Weathering by animals:
Disintegration of rocks by earthworm, termite, rats, etc.

(c) Weathering by humans:
Weathering taking place due to agricultural, mining and construction activities done by human beings.

Question 2.
Explain the meaning of denudation and the main types of denudation in detail.
Answer:
The process by which the cover of rocks of the crust gets removed is called Denudation. This process of denudation completes the action of leveling by the medium of exogenetic forces. Denudation is regarded as the combined result of weathering, erosion and mass translocation. On this basis, it is classified into the following parts:

Weathering:
Weathering is a spatial process in which the rocks break down by disintegration and decomposition at their own place. The process of weathering completes mainly in the form of physical, chemical and biological weathering. This process of weathering is affected by the structure and organization of rocks, slope of land, diversity in climate and vegetation. In this, the amount and periodicity of insolation, nature of glacier, structure of rocks and the effect of water and gases on them are included.

Erosion:
The word Erosion is made from the Latin word ‘Erodere’, the meaning of which is to rub or to nibble. Erosion is a dynamic process in which rocks keep on disintegrating by being rubbed, eroded, translocated or transported through glaciers, underground water, waves, air and rivers. The process of erosion takes place due to corrasion, attrition, hydraulic action, corrosion, deflation, cavitation and plucking.

Mass Translocation:
Movement and transfer of rock debris in massive amount along a slope due to gravitational force is called Mass Translocation. Gravitational force is responsible in rolling down of unorganized rock debris. Creeping down the slopes, the rock particles accumulate in the foothills. This accumulation or pile of rocks – flour is called Talus. On the basis of the amount of rolling or creeping of unorganized loose materials, the mass translocation is classified in the form of gradual flow, rapid flow and extreme rapid flow.

Question 3.
Explain in detail the concept of the Cycle of Erosion.
Answer:
American Geomorphologist, William Morris Davis propounded the concept of Cycle of Erosion in 1899. He explained, “During the period of Erosion Cycle, the uplifted terrain on being eroded, transforms into shape – less pedeplain.” For the presentation of Cycle of Erosion, Davis considered the three elements important: structure, process and stage. These three are known by the name of Trikoot of Davis. Their brief description is as follows:

1. Structure:
First, rock structure develops on a terrain. After that, various landscapes form there.

2. Process:
In the development of landscapes or land forms, any of the transformational processes like river, wind, waves, glacier, underground water, etc. plays a vital role.

3. Stage:
Like human life, there is a certain period of time for the development of landscapes. In the Erosion Cycle, Davis considered the direct connection between uplift and erosion. According to him, one of the two processes of uplift and erosion takes place at a time. When there is uplift, there is no erosion; and when there is erosion, there is no uplift. Erosion begins only when the uplift ends. The Erosion Cycle of Davis is classified into the following three stages:

• Youth Stage
• Mature Stage
• Old Stage.

Youth Stage:
In this stage, erosion begins after the ending of uplift. In this stage, the river flows along an uneven surface and there is intensive bottom erosion, the gradients are steep and the erosion is rapid. The rapid deepening of the channel leads to the formation of V-shaped valleys.

Mature Stage:
In this stage, lateral erosion begins whereby the valleys begin to widen rather than deepen. In this stage, the velocity of rivers reduces due to gentle slope, and this decreases their transportation capacity. Most of the rivers get levelled according to the base surface of the erosion.

Old Stage:
In this stage, unevenness of the earth’s crust reduces. The entire area transforms into a pedeplain. Absolute and relative relief both are minimized. The valleys become shallow and extremely broad, and their lateral slope is concave in shape.

The Cycle of Erosion of Davis is being presented by the following diagram:

RBSE Class 11 Physical Geography Chapter 9 Other Important Questions

RBSE Class 11 Physical Geography Chapter 9 Multiple Choice Questions

Question 1.
Weathering is a:
(a) Spatial process
(b) Dynamic process
(c) Process of movement
(d) None of these
Answer:
(a) Spatial process

Question 2.
Breaking of rocks in the form of shells is called:
(a) Block Disintegration
(b) Exfolation
(c) Pressure Release
(d) Frost Weathering
Answer:
(b) Exfolation

Question 3.
Where does the process of oxidation occur the most?
(a) in arid regions
(b) in humid tropics
(c) in cold regions
(d) in temperate regions
Answer:
(b) in humid tropics

Question 4.
In which process does carbonic acid form?
(a) in oxidation
(b) in carbonation
(c) in hydration
(d) in dissolution
Answer:
(b) in carbonation

Question 5.
Collision of the flowing rock particles and fragments among themselves is called:
(a) Attrition
(b) Corrosion
(c) Plucking
(d) Cavitation
Answer:
(a) Attrition

Question 6.
Where does the process of plucking occur?
(a) in deserts
(b) in plains
(c) in glacial regions
(d) in mountains
Answer:
(c) in glacial regions

Question 7.
The one which is not included in gradual flow, is:
(a) Earth Creep
(b) Rock Creep
(c) Soil Creep
(d) Slumping
Answer:
(d) Slumping

Matching Type Questions

Match Column A with Column B in the following:

Question A.

Column A (Type of Weathering)	Column B (Area of Weathering)
(i) Block Disintegration	(a) in humid tropics
(ii) Frost Weathering	(b) in lime regions
(iii) Oxidation	(c) in extreme cold regions
(iv) Carbonation	(d) in mining areas
(v) Weathering by humans	(e) in desert regions

Answers:

1. (e)
2. (c)
3. (a)
4. (b)
5. (d)

Question B.

Column A  (Process)	Column B (Relation)
(i) Talus Creep	(a) Extreme rapid flow
(ii) Sheet Flow	(b) Chemical weathering
(iii)Debris Fall	(c) Rapid flow
(iv) Dissolution	(d) By glaciers
(v) Plucking	(e) Gradual flow

Answers:

1. (e)
2. (c)
3. (a)
4. (b)
5. (d)

RBSE Class 11 Physical Geography Chapter 9 Very Short Answer Type Questions

Question 1.
What are Endogenetic Forces?
Answer:
Forces which originate in the internal part of earth are called Endogenetic Forces. New terrains are formed on the earth’s surface by these forces.

Question 2.
What are Exogenetic Forces?
Answer:
Forces originating or acting on the surface of earth are called Exogenetic Forces. The process of leveling is done mainly by these forces.

Question 3.
Of what is denudation a collective process?
Answer:
The denudation is a collective process of weathering, erosion and mass translocation.

Question 4.
Name the controlling factors of weathering.
Answer:
The factors that affect weathering include the structure and organization of rocks, slope of land, diversity of climate and vegetation.

Question 5.
What is the meaning of Mechanical Weathering?
Answer:
The disintegration of rocks by the action of physical factors like insolation, frost, water and wind pressure is called Physical Weathering.

Question 6.
What is the meaning of Disintegration?
Answer:
The action of breaking down of rocks into the fragments by the fragmentation of organized rocks is called Disintegration.

Question 7.
Why does Frost Weathering occur?
Answer:
Frost Weathering occurs in extreme cold regions, when the rocks break down due to the freezing and melting of water in the cracks of rocks on regular basis.

Question 8.
What does Pressure Release mean?
Answer:
When the removal of upper rocks reduces the pressure on the lower rocks, then cracks start appearing in the rocks. This process is called Pressure Release.

Question 9.
What is Chemical Weathering?
Answer:
When the rocks break, dissolve, decay and change into new compounds by the action of water and gas by chemical process, it is called Chemical Weathering.

Question 10.
What does Oxidation mean?
Answer:
When the atmospheric oxygen dissolves in water to change rock minerals into oxides, then this process is called Oxidation.

Question 11.
What does Carbonation mean?
Answer:
The atmospheric carbon dioxide gas (CO₂) dissolves in water to form carbonic acid. On coming in contact with it, the lime – rocks dissolve rapidly. This process is called Carbonation.

Question 12.
What is Hydration?
Answer:
The absorption of water in rock minerals is called Hydration.

Question 13.
What does Biological Weathering mean?
Answer:
The fragmentation of rocks by the biotic community (vegetation, living – organisms and humans) found on the earth’s crust is called Biological weathering.

Question 14.
What are the factors responsible for erosion?
Answer:
The factors responsible for erosion include glacier, underground water, sea waves, wind and flowing water.

Question 15.
What does Corrasion mean?
Answer:
A type of erosive action in which pebbles, stones, boulders, rock-particles, etc. along with any factor of erosion, erode the land-surface by rubbing or scraping, is called Corrasion.

Question 16.
What does Attrition mean?
Answer:
The rock fragments or rock particles when carried by the air, water and glacier, smash together and break into smaller particles. This process is called Attrition.

Question 17.
What does Hydraulic Action mean?
Answer:
The process of the erosion of rocks by the heavy pressure of river water or whirlpool is called Hydraulic Action.

Question 18.
What is Deflation?
Answer:
When the sand, dust or other unorganized rocks – flour are carried away by the winds from one place to another, this process is called Deflation.

Question 19.
What is Plunge Pool?
Answer:
Plunge Pool:
Deep trough built in a base rock by the erosion caused by pebbles and stones present in the whirlpool, which fall down from a height with the waterfalls.

Question 20.
What is called Mass Translocation?
Answer:
The process of the movement and transfer of rock debris in massive amount along a slope duetto gravitational force, is called Mass Translocation.

Question 21.
Into how many types is Mass Translocation classified?
Answer:
Mass Translocation is classified into three parts: mass translocation with gradual flow, with rapid flow and with extreme rapid flow.

Question 22.
Where does the process of gradual-flow take place the most?
Answer:
The process of gradual-flow mostly takes place in sub – polar cold regions.

Question 23.
In which forms is the extreme rapid flow seen?
Answer:
The extreme rapid flow is seen mainly in the forms of Landslide, Rock Slide, Rock Fall, Landslip, Debris Fall and Slumping.

Question 24.
Which are known as the Trikoot of Davis?
Answer:
Structure, process and time (stage) are known as the Trikoot of Davis.

Question 25.
What did Penck consider the Cycle of Erosion as the sum of?
Answer:
Penck considered the Cycle of Erosion as the sum of the stages of development of landscapes, their uplift rate and inter-relations of their degradation.

RBSE Class 11 Physical Geography Chapter 9 Short Answer Type Questions (SA-I)

Question 1.
Describe the processes included in Denudation.
Answer:
In Denudation, the following processes are included:

1. Weathering:
It is a spatial process, in which the rocks break down by dis-integration and decomposition at their own place. This process is called Weathering.

2. Erosion:
It is a dynamic process in which rocks keep on dis-integrating by being rubbed, eroded, trans – located or transported through glaciers, underground water, waves, wind and rivers. This process is called Erosion.

3. Mass Translocation:
Movement and transfer of rock debris in massive amount along the slope by gravitational force is called Mass Translocation.

Question 2.
What are the differences between block disintegration and frost weathering?
Answer:
The following differences are found between black disintegration and frost weathering:

Block Disintegration	Frost Weathering
1. This process of weathering takes place in desert regions.	1. This process of weathering takes place in polar and sub-polar regions.
2. This process takes place due to high temperature.	2. This process takes place as a result of the condition of low temperature.
3. In this type of weathering, the rocks disintegrate due to high range of temperature.	3. In this type of weathering, the rocks disintegrate due to changing of water into solid and liquid form.

Question 3.
What are the differences between Oxidation and Carbonation?
Answer:
The following differences are found between Oxidation and Carbonation:

Oxidation	Carbonation
1. In this process, the atmospheric oxygen dissolves in water.	1. In this process, the atmospheric carbon dioxide dissolves in water.
2. In this process, oxygen changes the rock minerals into oxides.	2. In this process, carbon dioxide dissolves in water to form carbonic acid.
3. Due to oxidation, the process of rusting in iron takes place.	3. Due to carbonation, the process of fragmentation of lime takes place.
4. This process takes place mostly in humid tropics.	4. This process takes place mostly in lime regions.

Question 4.
Explain the types of Biological Weathering.
Answer:
On the basis of their causative factors, Biological Weathering is classified as follows:

1. Weathering by Vegetation:
Roots of different types of trees by entering into the rocks make their particles loose, due to which dis – integration in the rocks takes place. This is called weathering by vegetation.

2. Weathering by Living Organisms:
This weathering takes place when the rocks are disorganized by various living – organisms like earthworm, termite, rats and animals.

3. Weathering by Humans:
When the rocks are disorganized by various human activities like mining, agriculture, construction, atomic explosion, it is included in the weathering by humans.

Question 5.
Explain the importance of weathering in brief.
Answer:
The importance of weathering is explained as follows:

1. In weathering, the rocks are broken up into small fragments, this facilitates soil formation.
2. Weathering is responsible for erosion and mass movement.
3. Depending on the depth of weathered materials, the growth of vegetation and bio-diversity are determined.
4. Weathering is helpful in massive erosion and degradation of high reliefs.
5. Topographies are the result of weathering and erosion.
6. By the weathering and deposition of rocks, the concentration of valuable minerals like iron, manganese, aluminium, copper, etc takes place, by which their exploitation, processing and refinement become easy.
7. Weathering is an important process of soil formation.

Question 6.
How is weathering responsible for bio-diversity on the earth?
Answer:
Bio – diversity represents the presence of various biological species found in a region on the earth’s surface. Weathering has a significant impact on bio – diversity. Bio – diversity is completely affected by vegetation. Rocks and minerals are trans – located by weathering and new surfaces are formed. This helps in the penetration of moisture and air in the surface by chemical process. Through this, the humus, carbonic and acidic materials enter into the soil, by which bio – diversity is affected. In this way, it can be said that weathering is responsible for bio – diversity on the earth’s surface.

Question 7.
What are the differences between Erosion and Mass Translocation?
Answer:
The following differences are found between Erosion and Mass Translocation:

Erosion	Mass Translocation
1. In erosion, the flowing water, glacier, wind, underground water, waves and currents are the major contributors.	1. The process of mass translocation takes place mainly due to gravitational force.
2. Erosion is a continuous process.	2. Mass translocation is not a continuous process.
3. The scope of erosion is wide.	3. The scope of mass translocation is limited in comparison to erosion.
4. Degradation takes place by erosion.	4. It is not necessary that degradation will take place by mass translocation.

Question 8.
Explain the stages of the Cycle of Erosion as described by Davis.
Answer:
Davis classified the Cycle of Erosion into three main stages:

1. Youth Stage
2. Mature Stage
3. Old Stage

1. Youth Stage:
In this stage, the river flows along an uneven surface and there is intensive bottom erosion, the gradients are steep and the erosion is rapid. The rapid deepening of the channel leads to the formation of V – shaped valleys.

2. Mature Stage:
In this stage, river widens the valley by lateral erosion. The bottom is eroded by the lateral erosion in this stage, by which the V – shaped valleys usually converts into a U – shape.

3. Old Stage:
In this stage, unevenness of the earth’s crust reduces and the entire area transforms into a pedeplain. In this stage, the slope is almost non-existent and the water spreads around.

Question 9.
Write the three drawbacks of the Cycle of Erosion concept of Penck.
Answer:
The theory related to the Cycle of Erosion of Penck has the following drawbacks:

1. Penck presented the theory of the Cycle of Erosion in German language. When it was translated from German to other languages (mainly in English), the meaning became distorted.
2. The theory becomes non-interesting due to being obscure.
3. Scholars do not agree on the concept of continuous movement in crust and the parallel withdrawal of slopes as presented by Penck.

RBSE Class 11 Physical Geography Chapter 9 Short Answer Type Questions (SA-II)

Question 1.
What are the components that control weathering.
Answer:
Weathering is a spatial process in which rocks disintegrate at their own place, but during this process many factors or components affect it. In these controlling factors, the structure and composition of rocks, slope of land, diversity of climate and vegetation are mainly included. The short description of all these factors/components is as follows:

1. Structure and Composition of Rocks:
Chemical weathering is more in the rocks with higher porosity and soluble minerals. Mechanical weathering is more in the rocks with vertical base layers, and chemical weathering is more in the rocks with horizontal layers.

2. Slope of Land:
Weathering is less in the land with gentle and low slope relatively to the land with steep slope.

3. Diversity in Climate:
Chemical weathering is more in humid tropics, while mechanical weathering is more in arid and tropical regions.

4. Influence of Vegetation:
Vegetation partially is a factor of weathering and partially is a constraint too. The amount of weathering is also more in vegetation less tropical regions due to more insolation.

Question 2.
Are physical and chemical weathering independent of each other? If not, then why? Explain with example.
Answer:
Weathering is a process of breaking down of rocks, in which due to disintegration and decomposition, rocks become weak and start getting separated. Under weathering, the weakening of rocks takes place in two ways:

1. By mechanical fragmentation.
2. By chemical decomposition.

The process of weakening down of rocks by physical factors like temperature, rainfall, air-pressure, etc. is called disintegration. This type of weathering is called Physical Weathering. The process of weakening down of rocks by chemical processes like oxidation, carbonation, hydration, etc. is called Chemical decomposition. This type of weathering is also called chemical Weathering.

The processes of physical and chemical weathering are different from each other, but both types of weathering are not independent of each other. The effects of factors that participate in physical and chemical weathering cannot be separated from each other. For example, temperature plays an important role in physical weathering, due to which the rocks undergo expansion and contraction and they become weak.

Weathering is completely influenced by chemical composition of rocks. On the basis of chemical composition, the ability to absorb heat in rocks is also affected. Similarly, water will not react with any rock, unless it receives heat by temperature or pressure. The processes of chemical weathering are not the same in all the heating boards. Chemical weathering is more active in tropical climatic regions where the temperature is high throughout the year.

Thus, it is clear that the physical and chemical weathering are not independent of each other and they are controlled by atmospheric conditions.

Question 3.
What is mass movement? Explain its various forms with the help of a diagram.
Answer:
All those movements are included in the mass movement, under which massive debris of rocks are displaced in accordance to the slope by gravitational force. In mass movement, there are creeps, flows, slides and falls of debris obtained from rocks. Weathering is not necessary in mass movement because in this, the fall of original rocks also start in accordance to the slope along with the weathered materials.

Mass movement occurs also due to gravitational force. There is no direct connection to the factors of erosion in this. Materials present their resistance on the slope. But due to gravitational force, they are generally not successful. Weak materials, thin bedded rocks, faults, steep slope, lack of adequate vegetation, etc. are the important helping factors of mass movement.

Question 4.
What are the major factors of the activation of mass movement?
Answer:
Important factors of the Activation of Mass Movement:
The important factors providing activation to mass movement are as follows:

1. By natural and artificial agents, the removal of the base, which supports the materials at the top.
2. Increase in the height and intensity of slope.
3. Materials to be of heavy weight.
4. Overload resulting due to the lubrication of saturated materials of slope by excessive rainfall.
5. Removal of materials from the surface of original slope.
6. Earthquake
7. Vibrations caused by explosives or machines.
8. Excess of natural leakage.
9. Excessive exploitation of water from river, lake and other water reservoirs, and gradual flow of water from down the river banks and slopes.
10. Indiscriminate exploitation of vegetation.

Question 5.
Into which stages did Penck classify the process of erosion? Explain.
Answer:
German scholar, Penck, classified his concept related to erosion into the following stages:

1. First Stage:
According to Penck, in this stage, both the processes of upliftment and erosion move together. But the upliftment is more than the erosion.

2. Second stage:
In this stage, uplift and erosion remain equally active. As a result, the valleys start to become wide and deep.

3. Third Stage:
In this stage, due to competitive rate, the dorsal difference of the upper and lower curves of the uplift and erosion processes remains the same.

4. Fourth Stage:
In this stage, the rate of uplift gets inactive and weak, and the erosion is effective at the same rate. As a result, the valleys are deep and move down.

5. Fifth Stage:
In this stage, along with the uplift, the rate of erosion also gets inactive and weak. The dorsal difference of both the curves decreases. The concept of Penck related to erosion is being presented by the following diagram.

Question 6.
“Our Earth is the playground of geomorphic processes of two opposing groups.” Explain.
Answer:
Changes take place in the configuration of the earth’s surface due to the physical pressure and chemical processes by endogenetic and exogenetic forces.

Two types of forces work in the formation of the earth’s surface:

1. Endogenetic Forces
2. Exogenetic Forces

Endogenetic forces originate from deep down the surface and work at a very slow speed. By this, mountains are formed and unevenness is created on the earth’s surface. Undesirable incidents also occur by some endogenetic forces like volcanic eruption, earthquake, etc. Exogenetic forces originate above the surface and work right opposite to the endogenetic forces, thereby trying to reduce the relief.

In this process, somewhere they do the work of erosion and somewhere accumulation. In this way, the unevenness of the earth’s surface reduces by exogenetic forces. Thus, these forces are also called ‘Level Establishing Force’. The opposite work of both the forces remains as long as the opposing action of endogenetic and exogenetic forces continue. In this way, it is said that the Earth is the playground of geomorphic processes of two opposing groups.

RBSE Class 11 Physical Geography Chapter 9 Essay Type Questions

Question 1.
Define erosion and describe the modes of factors responsible for it.
Or
Explain the modes of erosion.
Answer:
The word ‘Erosion’ is made from the Latin word ‘Erodere’, the meaning of which is to rub or to nibble. Erosion is a dynamic process. In this process, the rocks keep on disintegrating by being rubbed, eroded, translocated or transported through glaciers, underground water, sea waves, wind and rivers. By this process, a high terrain eventually transforms into a low terrain.

The following modes are held responsible for the process of erosion:

1. Corrasion
2. Attrition
3. Hydraulic Action
4. Corrosion
5. Deflation
6. Cavitation
7. Plucking

1. Corrasion:
When the erosion factors carry away rocks-debris and rocks – flour in their flow, then these materials cause the friction of surface rocks, which is called Corrasion.

2. Attrition:
The rock fragments or particles when carried by the air, water and glacier smash together and break into smaller particles, this is called Attrition.

3. Hydraulic Action:
The process of erosion of rocks by the heavy pressure of river water or whirlpool is called Hydraulic Action.

4. Corrosion:
By the chemical action of water, the minerals of rocks dissolve in water and flow away, which is called Corrosion.

5. Deflation:
The sand, dust and or other unorganized rocks – flour are carried away by the winds from one place to another place, which is called deflation.

6. Cavitation:
Waves rising from whirlpool in river form many types of holes at the bottom of the river, which is called Cavitation. Pot holes and plunge pools are examples of such holes.

7. Plucking:
When glaciers uproot the rocks coming in their way and transport them along, then this action is called Plucking. The eroded materials usually flow in the three forms:

(a) Dissolving:
Various materials dissolve in water and flow along with it.

(b) Suspension:
Materials float or hang along with erosive factors (water or wind) and flow along.

(c) Sliding:
Large masses of rocks drag or slide and flow on the surface of the river, which is known as sliding.

Question 2.
What is the meaning of Mass Translocation? Explain its types.
Answer:
Movement and transfer of rock debris in massive amount along a slope due to gravitational force is called Mass Translocation. The gravitational force is responsible for the rolling down of unorganized rock debris. Creeping down the slopes, the rock particles accumulate in the foothills. This accumulation or pile of rocks – flour is called Talus.

A cone – shaped accumulation of loose rocks is called Talus Cone. On the basis of the amount and speed of creeping or rolling down of unorganized loose materials, mass translocation is classified into the following three groups:

1. Mass translocation with gradual flow:
Due to less amount of moisture, the rocks – flour creeps slowly. The action of gradual flow occurs mostly in sub-polar cold regions. Earth Creep, Rock Creep, Talus Creep and Soil Creep are included under the action of gradual flow.

2. Mass translocation with rapid flow:
Due to the adequacy of water, the rocks – flour gets saturated and creeps rapidly. Earth flow, Mud flow and Sheet flow are included under rapid flow. Mud flow can be seen creeping on the walls of the river valleys.

3. Mass translocation with extreme rapid flow:
Moisture of water is not necessary for extreme rapid flow. Large rock fragments start falling suddenly by gravitational force. Landslide, Rock Slide, Rock Fall, Landslip and Debris Fall are included in extreme rapid flow.

Question 3.
Compare the ideas of Davis and Penck.
Answer:
The comparison of the ideas of Davis and Penck is as follows:

RBSE Solutions for Class 11 Geography