WBBSE Solutions For Class 9 Geography And Environment Chapter 4 Geomorphic Processes And Land Forms Of The Earth

Class 9 Geography Book WBBSE Chapter 4 Geomorphic Processes And Land Forms Of The Earth Short Questions With Answers:

Question 1. Name the largest deltaic plain in the world.
Answer: The deltaic plain of the Ganga-Brahmaputra is the largest deltaic plain in the world.

Question 2. Which is the largest aggradational plain in India?
Answer: The Ganga-Brahmaputra plain is the largest aggradational plain in India.

Question 3. Name one lava plateau.
Answer: The plateau of Maharashtra (located in the northwest of the Deccan plateau) is a lava plateau.

Read and Learn all WBBSE Solutions for Class 9 Geography and Environment

Question 4. What are anticlines?
Answer: The arch-shaped folds are called anticlines.

Question 5. What are synclines?
Answer: The downfold troughs are called synclines.

Question 6. What is a symmetrical fold?
Answer: When both the limbs (sides) of the fold remain equally bent, it is called a symmetrical fold.

Question 7. Define asymmetrical fold.
Answer: When a limb of the fold is pushed too far making one limb steeper than the other, an asymmetrical fold is formed. :

Question 8. Name two categories of endogenetic processes.
Answer: Diastrophism and sudden forces.

Question 9. Name two main forces of diastrophism.
Answer: Expeirogenetic and Orogenetic.

Class ix Geography Book WBBSE

Question 10. Which is the best example of rise of coast or emergence of coast in India?
Answer: Kathiawar Peninsula.

Question 11. What is called the bending of horizontal layer of rocks?
Answer: Folding.

Question 12. Name one intermontane plateau.
Answer: Plateau of Tibet.

Question 13. Which is the largest rift valley?
Answer: World’s largest rift valley is extended in 4800 km of length starting from Israel and Jordan up to Zambezi river of eastern Africa.

Question 14. Why do you think that the slopes or gradients are created by tectonic factors?
Answer: The slopes or gradients are created by endogenetically tectonic factors such temperature, crystallisation and melting.

Question 15. Name one rift valley.
Answer: Rhine valley of Germany.

Question 16. Which is the largest rift valley?
Answer: World’s largest rift valley is extended in 4800 km of length starting from Israel and Jordan up to Zambezi river of eastern Africa.

Question 17. What is called the raised portion between two faults?
Answer: Block mountain.

Question 18. Where was the Tethys Sea’ located?
Answer: Tethys Sea was located in the region of the Himalayas.

Question 19. Name one bird’s foot type delta.
Answer: The Mississipi delta.

Question 20. Which type of mountain is the Andez?
Answer: Fold Mountain.

Question 21. Name any volcanic mountain.
Answer: Mount Fujiyama in Japan.

Question 22. Give at least two examples of dissected plateaus.
Answer: Chottanagpur Plateau of Jharkhand & Malnad region in Karnataka.

Question 23. Give at least two examples of Residual mountains.
Answer: Eastern Ghats & Aravallis.

Question 24. What is the name of highest plateau of India?
Answer: Ladakh Plateau of Kashmir.

Question 25. Name the oldest fold mountain of India.
Answer: The Aravallis.

Question 26. Give two examples of rift valleys of India.
Answer: Narmada valleys and Damodar valleys.

Class ix Geography Book WBBSE

Question 27. The Himalayas belong of which type of mountain.
Answer: Fold Mountain.

Question 28. Which is the highest plateau in the world?
Answer: Pamir Knot.

Question 29. Which plateaus result from tectonic movements?
Answer: Continental Plateaus.

Question 30. Name the mountains formed due to tensile forces and faulting.
Answer: Block Mountains.

Question 31. Name a residual mountain which was also an old fold mountain.
Answer: The Aravallis.

Question 32. Define peneplain.
Answer: Peneplain means almost plain (pene = almost, plain = plain). It is formed by erosion.

Question33. What is over-fold?
Answer: When one limb of the fold is pushed over the other, it is known as over-fold.

Question 34. What is a fault?
Answer: A fault is a landform of facture. It is formed when the broken parts of rock- bed are displaced on either side of the facture.

Question 35. What do you mean by Degradation?
Answer: Wearing down of rocks/relief or elevation is called degradation.

Question 36. What is meant by Aggradation?
Answer: Filling up of basins, depressions or lowlands is termed as aggradation.

Question 37. What do you mean by the term Graduation?
Answer: The phenomenon of wearing down of relief variations of the surface of the earth through erosion is known as gradation.

Question 38. Name one opposing group of geomorphic processes.
Answer: Endogenic Pro

Class 9 Geography Book WBBSE Chapter 4 Geomorphic Processes And Land Forms Of The Earth True Or False Type

Question 1. Vindhyan Mountain is known as a block mountain.
Answer: True

Question 2. The area lying between two folds is known as a syncline in a fold mountain.
Answer: True

Question 3. One volcano of India is Barren Island.
Answer: True

Question 4. Ganga plain is an Alluvial Plain.
Answer: True

Question 5. Deccan Plateau is a lava plateau.
Answer: True

Question 6. Tibet is an intermontane plateau.
Answer: True

Question 7. Satpura is a block mountain.
Answer: True

Question 8. Block mountains are also called fault mountains.
Answer: True

Geography Class 9 Chapter 4 Question Answer

Question 9. Block mountains have flattened summits.
Answer: True

Question 10. Longest fold mountain is the Andes of S. America.
Answer: True

Question 11. Aravali is the oldest fold mountain in India.
Answer: True

Question 12. Plateaus have steep escarpment.
Answer: True

Question 13. Oxbow lakes are very common in the flood plain.
Answer: True

Question 14. Depressed plains are created because of tectonic movement.
Answer: True

Chapter 4 Geomorphic Processes And Land Forms Of The Earth Short Fill In The Blanks

Question 1. Block mountains are formed due to________.
Answer: Fault.

Question 2. Peneplains means_________ plain.
Answer: Almost.

Question 3. Chhotanagpur plateau is an example of__________ plateau.
Answer: Dissected.

Question 4. Maharashtra plateau is an example of___________ plateau.
Answer: Lava.

Question 5. Anatolia plateau is an example of __________plateau.
Answer: Intermontane.

Geography Class 9 Chapter 4 Question Answer

Question 6.___________ valley is a depressed area in between two block mountains.
Answer: Rift.

Question 7. Narmada Valley is an example of___________ valley.
Answer: Rift.

Question 8. ________is the only example of a volcanic mountain in India.
Answer: Barren Islan

Chapter 4 Geomorphic Processes And Land Forms Of The Earth 2 Marks Questions And Answer Question

1. What is Pangea?
Answer:

Pangea

According to Alfred Wegener, a German geologist, hundred of millions years before an original single sialic landmass was surrounded by a primeval sima-floored ocean (Panthalassa). This single landmass was Pangea which was later broken and drifted apart from the recent shape of the land surface.

Question 2. What are Angaraland and Gondwana land ?
Answer:

Angaraland and Gondwana land

In Precambrian times the Pangea was separated into two landmass on either side of the Tethys sea. To the North the landmass named Angaraland and to the South was the Gondwanaland.

Question 3. How volcanic mountains are formed?
Answer: When repeated eruptions take place through a vent of a volcano, the solidification of lava forms a high mountain around the crater of volcano. Thus, volcanic mountain is formed. Example – Fujiyama of Japan, Vesuvius in Italy.

Geography Class 9 Chapter 4 Question Answer

Question 4. What are the characteristics of volcanic mountains?
Answer:

Characteristics of volcanic mountains

(1) Volcanic mountains are cone-shaped.

(2) The peak of the hill has an opening or crater.

(3) Large volcanic mountains have multiple craters.

(4) The crater is connected to the magma chamber in the earth’s interior by a pipe or neck. ;

Question 5. What are the characteristics of Relict mountains?
Answer:

Characteristics of Relict mountains

(1) The mountain top is round & no sharp peaks are visible.

(2) The mountain slope is gentle.

(3) Relict mountains are of low height.

Question 6. Where was the ‘Tethys Sea’ located?
Answer:

Location Of Tethys Sea

The Tethys Sea was located in between the Gondwanaland in the South and the Angaraland in the North, and particularly where the Himalaya is now situated.

Question 7. Why is Pamir Plateau called the ‘roof of the world’?
Answer: The Pamir is the highest plateau (4,873 m) in the world (in Asia) and that is why it is called the ‘roof of the world’.

Question 8. What is aggradational plan?
Answer:

Aggradational plan

Aggradation means levelling of the earth’s surface by deposition. Alluvial plains are formed by deposition and known as aggradational plain.

Question 9. Define external forces.
Answer:

External forces

The forces which originate in the atmosphere and on the surface of the earth and cause changes on the surface are termed as external forces. They are also called Exogenic forces.

Question 10. What is Internal Forces?
Answer:

Internal Forces

Internal forces are those forces which originate in the interior of the earth and cause changes on the surface of the earth. They are also termed as Endogenic forces.

Geography Class 9 Chapter 4 Question Answer

Question 11. write a short note on Geomorphic Processes.
Answer:

Geomorphic Processes

The processes through which endogenic and exogenic forces cause physical stresses and chemical reactions on earth’s material and bring about changes in the configuration of earth’s surface are called geomorphic processes.

Question 12. What are Exogenic Processes?
Answer:

Exogenic Processes

Processes like weathering, mass wasting, erosion and deposition which riginate in the atmosphere or on the surface of the earth and cause changes on the surface are known as exogenic processes.

Question 13. What are Endogenic Processes?
Answer:

Endogenic Processes

Processes like volcanoes and earthquakes which originate in the interior of the earth and cause changes on the surface are given the name of endogenic processes.

Question 14. Define Diastrophism.
Answer:

Diastrophism

Diastrophism is the combination of all processes that move, elevate or build portions of the earth crust including orogenic processes, epeirogenic processes, earthquakes and plate tectonics.

Question 15. What are Orogenic Processes?
Answer:

Orogenic Processes

Orogenic processes are those processes which involve mountain building through severe folding and affecting long and narrow belts of the crust.

Class 9 Chapter 4 Geography Notes WBBSE

Question 16. Define Volcanism.
Answer:

Volcanism

Volcanism includes the movement of molten rock material (magma) into or towards the earth’s surface and also formation of many intrusive and extrusive volcanic forms.

Question 17. What are the types of horizontal forces?

Answer:

Horizontal forces as of two types :

(1) Compression :
It is a force which pushes against a body from opposite sides.

(2) Tension :
The rocks are pulled apart by tensional forces acting from within the earth.

Question 18. What are vertical movements and Orogenic movements?
Answer:

Vertical movements and Orogenic movements

Vertical movements, also known as epeirogenic movements [from Greek epeiros-continent] are continent-building movements and are closely associated with plate tectonics.

Question 19. What are Horizontal movements?
Answer:

Horizontal movements

Horizontal movements, also known as orogenic movements [from Greek oros-mountain] are mountain-building movements. They are caused by compressional and tensional forces acting on the surface of the Earth.

Question 20. Define Exogenic elements of nature.
Answer:

Exogenic elements of nature

Exogenic elements of nature are also called agents of gradation as they cause picking up of weathered material, transport it and deposit it in the lowlands or depressions.

Examples: water, ice, wind, waves, underground water, etc.

Question 21. What are the names of upfold and downfold respectively?
Answer:

Names of upfold and downfold respectively

Anticline and syncline.

Class 9 Chapter 4 Geography Notes WBBSE

Question 22. What is meant by Folding?
Answer:

Folding :
The bending of horizontal layers of rock is known as folding.

Question 23. Define the term symmetrical folds.
Answer:

Symmetrical Folds :
When both the limbs of a fold are equally bent and they are inclined at almost equal angles to the horizontal, it is called symmetrical fold.

Question 24. Define Asymmetrical Fold.
Answer:

Asymmetrical Fold :
This type of fold is formed when one limb of the fold is pushed too far so that one side of the fold is long and gradual in slope while the other is short and steep.

Question 25. Define the term Recumbent Fold.
Answer:

Recumbent Fold :
When the isoclinal or overfold goes to such an extent that one limb is pushed over the other and the two limbs are almost parallel to each other lying in a roughly horizontal posture, it forms a recumbent fold.

Question 26. What do you mean by Over thrust Fold?
Answer:

Overthrust Fold :
In case of acute folding, the pressure of the compressional force is so great that a fracture occurs in the fold, and one limb slides forward over the other limb along the thrust plane. This results in an overthrust fold. The overthrust limb of the fold is known as Nappe.

Class 9 Chapter 4 Geography Notes WBBSE

Question 27. What is fold?
Answer:

Fold

A fold is the contraction in the rock strata originated by horizontal compression of the earth’s crust. The layer of rock which bends upward is anticline and that which bends downward is syncline.

Question 28. What is geosyncline?
Answer:

Geosyncline: Geosynclines are formed due to a large folding. A syncline on a large scale or a large depression or trough in the earth’s crust is known as a geosyncline. It extends for wide distances upto hundreds of kilometres.

Question 29. What is the meaning of faulting?
Answer:

Faulting :
As compression results in folding so tension results in faulting. As the force of tension increases in the earth’s crust, a stage comes when the rock strata cannot withstand the force and the crust breaks.

 

 

Question 30. What is a rift valley?
Answer:

Rift valley :
When a block is downthrown betwen two parallel faults, a rift valley is formed. It is a long and narrow valley with steep edge. It is also known as Graben in German language.

Example: Narmada valley in India, Rhine valley in Europe.

 

Question 31. Distinguish between Dormant Volcanoes and Extinct Volcanoes.
Answer:

The distinction between Dormant Volcanoes and Extinct Volcanoes is as follows :

Dormant Volcanoes	Extinct Volcanoes
1.  Volcanoes which erupt intermittently are known as dormant volcanoes.	1.  The volcanoes that have not erupted for a long time and have reported to be erupted in historic times are called extinct volcanoes.
2.  They are also named as sleeping volcanoes. Example: Barren island of India.	2. They are also called dead volcanoes. Krakatao in Indonesia was extinct till 1883.

 

Question 32. What are lacustrine plains? :
Answer:

Lacustrine Plains :
Depositional plain of sediments in a lake basin gives rise to old lake plain or a Lacustrine plain. Example: The Imphal basin of Manipur the Kashmir valley are examples of this type.

Geography Chapter 4 Class 9 WBBSE

Question 33. Discuss some features of deltaic plains.
Answer:

Some characteristic features of a deltaic plain :

(1) They are flat-level lands.

(2) They are triangular in shape, formed at the mouth of a river.

(3) They are the extensions of the floodplain.

(4) several smaller branches of the main river drain into sea. These smaller branches are called distributaries.

Question 34. What is Aggradation?
Answer:

Aggradation :
The deposition of unconsolidated deposits by river, wind, wave or glacier and other transporting agents.

Question 35. What is degradation?
Answer:

Degradation :
The lowering or flattening of a surface through erosion especially erosion carried out to maintain the graded profile of a river.

Question 36. What is Diastrophism?
Answer:

Diastrophism :
The slow or sudden processes or earth movements that cause elevation or build up portions of the earth’s crust.

Question 37. What is Denutrophism?
Answer:

Denutrophism :
The laying bare of underlying rocks by the process of weathering, transport and erosion.

Question 38. What is Endogenic process?
Answer:

Endogenic process :
This refers to those forces operating below the crust which are involved in the formation of surface features.

Geography Chapter 4 Class 9 WBBSE

Question 39. What is Epeirogenic movement?
Answer:

Epeirogenic movement :
Broad and generally large-scale vertical movement of the earth’s crust which does not involve much alteration in structure of the rock.

Question 40. What is Exogenic Process?
Answer:

Exogenic Process :
This refers to the processes which operate at or near the earth’s surface through the agents of denudation like running water, glacier, wind and waves.

Question 41. What is Gondwanaland ?
Answer:

Gondwanaland :
A ‘supercontinent’ occurring as a continuous region of land formed of the now separate units of Africa, Madagascar, Antarctica, Australia and India.

Question 42. What is Laurasia?
Answer:

Laurasia :
One of the two original continents which broke from the supercontinent Pangea by continental drift.

Question 43. What is Subduction?
Answer:

Subduction :
The transformation into magma of a denser plate as it dives under another less dense plate. A zone where rocks of an oceanic plate are forced to plunge below much thicker continental crust is called the subduction zone.

Chapter 4 Geomorphic Processes And Land Forms Of The Earth 2 Marks Questions And Answers (Short Notes)

Question 1. Relict Mountains.
Answer:

Relict Mountains

The mountains which are formed by weathering, erosion and denudation are called Relict or Residual Mountains.

Example: The Parasnath, the Aravalis, etc.

Geography Chapter 4 Class 9 WBBSE

Features:

(1) They do not have pointed peak.
(2) They are of low altitude.
(3) They are made up of very hard rocks.

Question 2. Mountain of Accumulation.
Answer:

Mountain of Accumulation

This is also known as volcanic mountains, because it is formed by the accumulation of volcanic materials, such as lava, magma, volcanic dust and ash. According to the plate tectonic theory, hot magma comes out through the weakened crust.

The materials are deposited in layers around the vent and in course of time build volcanic cone. The cone is called volcanic mountain. If the lava is basic, the cone is flat and if the lava is acidic the cone is steep. Examples of volcanic mountains are

(1) Vesuvius of Italy, Fuziyama of Japan, Kilimanjaro of Africa, etc.

WBBSE Geography Book Class 9

Question 3. Flood plains.
Answer:

Flood plains

The plains which are formed by the deposition of sediments brought by the rivers during a flood are called Flood Plains. ‘

Example: The Ganga Brahmaputra flood plain is the largest aggradational Plain.

Features:
(1) It is very levelled plain bordering a river.
(2) It is formed by the layers of silt brought down by the river.
(3) Braided river, meander, ox-bow lakes, swamps sandbars, etc. are the features of flood plains.

 

Question 4. Peneplain –
Answer:

Peneplain

The plains which attain almost level surface, worn down by erosion, are called Peneplains.

Peneplain means almost a plain. It isa combination of two words, pene = almost and plain = plain. These plains are formed as a result of weathering, erosion and denudation. Rivers, wind, ice, etc. help to reduce uplands to undulating plains. Monadnocks, heaps of stone and knoll are sometimes found on this plain.

The concept of peneplain was introduced by William Morries Davis. He used the term to describe the low and gently undulating plain which is the ultimate product of erosion.

WBBSE Geography Book Class 9

Question 5. Tethys Sea – (S.Question)
Answer:

Tethys Sea

Tethys sea was situated in the region of the Himalayas. The Himalayas were formed millions of years ago from a shallow Geosynclinal sea called Tethys sea. There were two large ancient land masses on either side of it.

To the North, there was the Angaraland and to the South was the Gondwanaland. Sediments from these land surfaces were deposited in the Tethys sea which were formed into sedimentary rock.

Then to million years ago, the two ancient lands pushed up. The sediments of the Tethys sea as they moved towards each other. The push from the North was greater, therefore the southern slope of the Himalayas is steeper than the northern slopes.

The large folds over great real and vertical distances were formed. The height being great snow is perpetually found throughout the higher slopes. So these mountains are the abode of snow as the Himalayas.

Question 6. Rift Valley –
Answer:

Rift Valley

Rift Valley is formed either by tension or by compression. Under tension, the fault blocks sink between parallel faults. While compression cause the fault blocks to rise up towards each other over a central block bound by parallel faults. The central depressed area bound by steep fault scrap side forms a Rift Valley. The blocks towering above on two sides of the rift valley are called block mountains, e.g. between the Vindhyas and the Satpuras lies the rift valley through which flows the Narmada river.

 

Question 7. Horst – (S.Question)
Answer:

Horst

The origin of Block mountains is tectonic. They result from vertical movements in the earth’s crust. Due to dropping down a part of the lithospheric plate or due to intense tensional force, the layers of rock may break giving rise to cracks and fractures and when the broken parts are displaced on either side of the fracture, fault is formed. In the process, up landing landmass forms a mountain known as Block mountain or a “Horst”. When a block is thrown down between two parallel faults, a rift valley is formed. It is long and narrow with deep ridges. Satpura and Vindhyas (India), Black Forest (Germany), Vosges (France) are examples.

WBBSE Geography Book Class 9

Question 8. Monadnocks. –
Answer:

Monadnocks: Eroded and isolated remains of resistant rocks materials appearing like mountains are called Monadnocks, after Mt. monadnock in New Hampshire in USA. Thus all monadnocks may be called Residual Mountains. These eroded and lowered relicts of landforms were called Monadnocks by W.M. Davis.

Question 9. Inselburg –
Answer:

Inselberg :
The German term, ‘Inselberg’ (meaning ‘island mountain’) was invented by S. Passarge, a German geomorphologist in 1904. Inselbergs are steep-sided isolated hills. They are like residual hills, such as buttes.

They are the remnants of larger upland areas that have been eroded away by the action of rivers. Other opinion is that inselbergs are large blocks of unweathered rock that are slowly being excavated from a covering of weathered materials. Probably both processes are at work. Ayers Rock of Australia is an example of inselberg.

 

Passarge conducted a thorough study of the inselberg landscape in Kalahari and Nambia. He found resistant crystalline rocks had long been exposed. Butiselbergs occur even in humid regions.

In Brazil, inselberg namely Sugar Loaf has developed in a tropical humid climate and along the coast. It has been partially submerged even. Besides Kalahari and some other deserts had been humid regions in the past.

Chapter 4 Geomorphic Processes And Land Forms Of The Earth 3 Marks Questions And Answers

Question 1. Distinguish between –
(1) New Fold Mountain and Old Fold Mountain.
(2) Fold Mountain and Block Mountain.
(3) Flood Plain and Deltaic Plain.
(4) Iintermontane Plateau and Piedmont Plateau.
Answer:

Difference Between New Fold Mountain and Old Fold Mountain.

(1) New Fold Mountains	Old Fold Mountains
(1) They are newly formed mountain. (2)    They contain usually soft rocks. (3)    Effect of weathering and erosion is less on these mountains. (4)    They have high-pointed peaks. (5)    They have high elevation.	(1)    They are ancient mountains. (2)    They contain usually hard rocks. (3)    Effect of weathering and erosion is high on these mountains. (4)    They do not have high-pointed peaks. (5)    They do not have high elevation.

 

Difference Between Fold Mountain and Block Mountain.

(2)    Fold Mountain	Block Mountain
(1) They are formed due to forces of compression.	(1) They are formed due to forces of tension.
(2)    They have high-pointed peaks.	(2)    They have low-pointed peaks.
(3)    They are formed due to fold in the earth’s crust.	(3)    They are formed due to fault in the earth’s crust.
(4)    They do not have rift valley.	(4)    They are always associated with rift valley.
(5)    The Himalayas, the Alps are examples of fold mountains.	(5)    The Vosges, the Vindhayas are examples of Block Mountains.

 

Difference Between Flood Plain and Deltaic Plain.

(3)    Flood Plain	Deltaic plain
(1)    It is formed in the middle stage of a river.	(1)    It is formed on the last stage of a river.
(2)    They have high elevation compared to deltaic plain.	(2)    They are almost level with the area.
(3)    They do not have marshy land.	(3)    They contains marshy land.
(4)    The sand granules are bigger in in size.	(4)    The sand granules are very small and time.
(5)    Wheat, rice, sugarcane are grown here.	(5)    Jute, coconut, etc. are grown here.

 

Difference Between Iintermontane Plateau and Piedmont Plateau.

(4) Intermontane Plateau	Piedmont Plateau
(1) Intermontane plateau are surrounded b” mountains on all sides.	(1) These plateaus are located at the foot of mountains.
(2) These are areas of inland drainage.	(2) These are bounded by a plain or an ocean on one side.
(3) These cover a large area.	(3) These have a limited area.
(4) Tibet plateau is an intermontane plateau.	(4) Patagonia is a piedmont plateau.

 

Question 2. How does folding takes place?
Answer:

Folding: The horizontal forces of compression cause tilting, warping and twisting of rocks. This is known as folding. When the rock’s strata are compressed from side to side, a part of the crust is raised into folds.

Folding occurs when horizontal forces act towards a common point or plane from opposite directions. Rock folds look like waves on a lake surface, resulting in a series of troughs and crusts.

The crusts are the upfolds or anticlines, while the troughs are the downfolds or synclines. The force of compression leads to contraction of the folds while the force of tension leads to expansion of the fold. Due to folding, a ridge and valley topography is formed. Folding has caused most of the world’s great mountain systems.

Class 9 Geography Chapter 4 Question Answer WBBSE

Question 3. What are Plains?
Answer:

Plains

Extensive areas of level or gently undulating lands usually of low altitude are called plains. Plains may be formed in a variety of ways and are often named accordingly. On many of the plains of the temperate zone, the natural vegetation is grass, and the plains have thus come to be known as grasslands.

Question 4. What is Wave Cut Plain?
Answer:

Wave Cut Plain :

Sea waves constantly attack the coast and erode it. As a result, the recedes leaving in front a platform first below the sea level. On the other hand, the return water of the waves transport the eroded materials and deposit them at the edge of the wave cut platform resulting in its seaward extension.

Such plains are created because of the waves and are known as wave cut plains. The coastal plain of South Africa, India and the USA are formed in this way.

Question 5. Distinguish between Mesa and Butte.
Answer:

Differnce between Mesa and Butte

Mesa, a Spanish word, means a flat-topped upland. The harder top layers of rocks have resisted denudation and being horizontal have maintained flat summits. A butte is a small isolated portion of a Mesa. A Mesa in the semi-arid area becomes reduced by erosion to a butte.

Question 6. Why fossils are found in fold mountains?
Answer:

Fossils are found in fold mountains due to –

(1) Fold mountains are formed on shallow seas. So, the remains of the sea creatures are found in it.

(2) Rivers brought seas layer upon layer. Hence, they sometimes brought the remains of animals and plants. So, in fold mountains, fossils are usually found.

Class 9 Geography Chapter 4 Question Answer WBBSE

Question 7. The formation of block mountain and rift valley is interlinked. Why? (S.Question)
Answer:

The formation of block mountain and rift valley is interlinked.

The origin of block mountains is tectonic. This is the result of vertical movements in the earth’s crust. Due to dropping down a part of the lithospheric plate or due to intense tensional force, the layers of rock may break giving rise to racks and fractures and when the broken parts are displaced on either side of the fracture, fault is formed.

In this process the up landing landmass forms a mountain known as Block mountain or a “Horst”. When a block is thrown down between two parallel faults, a rift valley is formed. It is long and narrow with deep ridges. Satpuras and Vindhyas (India), Black Forest (Germany), Vosges (France) are its examples.

Question 8. What is meant by mountain of accumulation? Give an example.
Answer:

Mountain of accumulation

This is also known as volcanic mountain, because it is formed by the accumulation of volcanic materials, such as lava, magma, volcanic dust and ash. According to the plate tectonic theory, hot magma comes out through the weakened crust.

The materials are deposited in layers around the vent and in course of time cone is flat and if the lava is acidic the cone is steep.

Examples of volcanic mountain are

(1) Vesuvius of Italy, Fujiyama of Japan, Kilimanjaro of Africa etc.

Question 9. Describe the characteristics of Block mountain with examples.
Answer:

Block mountains are formed when the earth’s crust breaks into blocks separated by fissures as a result of faulting. :

Some of their characteristic features are :—

(1) A block mountain has a flat summit and the slopes on either side are steep.

(2) The areas of block mountain have rift valleys which are formed by the depression between two fault planes.

(3) Block mountains do not have great height and neither do they cover extensive areas.

(4) The elevated regions are surrounded by areas of comparatively very low elevation.

Question 10. What is plateau? Mention any three factors for the formation of plateau.
Answer:

Plateau

A plateau is an upland area with a flat top and steep sides. Its surface has the appearance of a table, hence its other name is tableland. The average height of a plateau is 600 m above sea level, but some may rise to a much greater height. There are mainly three reasons for the formation of plateaus, namely :

Class 9 Geography Chapter 4 Question Answer WBBSE

(1) Diastrophism or Earth Movements:—

These are the movements which originate inside the earth’s crust and as a result, the land surface of the earth was fragmented and gradually moved away from each other forming plateaus like Arabian plateau, Deccan plateau etc. Some plateaus are also formed along with the formation of mountains like Ladakh plateau.

(2) Natural Agents of Erosion:—

Extensive uplands and mountain areas are eroded by the forces of erosion (sun rays, rain, wind, running water etc.) and reduced to low plateau areas.
Example: Malwa Plateau.

(3) Accumulation of Lava:—

The lava which reaches the earth’s surface through cracks and weak zones flows and cover large areas of earth. Such repeated eruptions form plateaus.
Example: Maharashtra Plateau.

Question 11. What are dissected plateaus? Give one example.
Answer:

Dissected plateaus

A vast plateau worn out by weathering, erosion and denudation by innumerable river, rivulets wind, ice etc. is known as dissected plateau. Its surface is irregular and is divided into many blocks.

The external agents, like sun, rain, running water, glacier etc. wear away the soft rocks of the high plateau and the remaining resistant masses are left. These stand on the ground above the surroundings. Sometimes their surface is level cut by streams.

Examples are:-

(1)Chhotanagpur plateau (India).
(2) Plateau of Wales (Great Britain).
(3) Malwa plateau (India), etc.

Question 12. Distinguish between Aggradation and Degradation.
Answer:

Difference between Degradation and Aggradation

Class 9 Geography Chapter 4 Question Answer WBBSE

Degradation	Aggradation
(1)  When landforms of high elevation are reduced in height, the process is known as degradation. (2) The word degradation comes from the word ‘degrade’ and ‘degrade’, means to lower. (3) This happens to work by three processes —erosion, transportation and deposition. (4) Elevated landform is reduced in height by this process.	(1) When landforms of low elevation are increased in height, the process is known as aggradation. (2) The term aggradation comes from the word ‘aggregate’ which means to add to. (3) This happens to work by the process of deposition. (4) Low landform is increased in height by this process.

 

Question 13. Distinguish between Hills & Mountains.
Answer:

Distinction between Hills and Mountains are :

Hills Mountains

Hills	Mountains
(1) A natural elevation of the earth’s surface, not as high as a mountain, is loosely called a hill.	(1)A high landmass on the earth’s surface, attaining a great height above the surroundings with a series of ranges and peaks is called mountains
(2)The height of a hill generally ranges from 600m to 1000m	(2) The height of a mountain is above 1000 m.
(3) Hills are not much extensive as mountains.	(3)Mountains are extensively located.
(4)They have gentle slopes.	(4) They have more rugged features like steeper slopes and deep valleys.
(5)Hills have rounded peaks,	(5) Mountains have sharp peaks
(6)Rajmahal and Ayodhya are examples of hills.	(6) Himalayas, Andes are examples of mountains

 

WBBSE Class 9th Geography Chapter 4 Notes

Question 14. Write a note on Fault theory.
Answer:

Fault Theory :

A majority of geologists argue that block mountains are the product of faulting. Among those who advocated the fault theory are Clarence
King. G.K. Gilbert, G.D. Louderback and W.M. Davis. According to this theory, block mountains are formed in the following ways—

(1) Due to upward movement of the block in the middle between two normal faults. The summit of the block is flat.

(2) Sometimes, the surrounding blocks subside leaving the middle block stationary. Such cases are found in high plateau regions.

(3) Block mountains may originate when the middle block moves downward and becomes a rift valley while the surrounding blocks stand higher as block mountains.

Question 15. Discuss the conditions necessary for the formation of deltaic plains.
Answer:

Conditions necessary for the formation of deltaic plains are as follows :

(1) Shallow Sea :
The sea in which the river enters should be shallow.

(2)Calm sea :
Sea in which the river enters must be comparatively calm. The rate of deposition of sediments at or just beyond the mouth of a river should
exceed the rate of removal by waves, currents, etc.

(3)Fresh Water :
A freshwater lake into which the river flows causes quick deposition of silts because the current in the lake is usually checked.

(4) Long River with many tributaries :
There must have a large load and this will happen if there are many tributaries of the main river which flows over along distance having active erosion in their upper catchments areas of the valley.

(5) Soft Rock Strata :
The river together with its tributaries flow over the region mostly made up of soft rock strata.

WBBSE Class 9th Geography Chapter 4 Notes

Question16. What do you know about Pediment and Bajada?
Answer:

Pediment :

A pediment is an erosional plain formed by the joint erosional action of wind and water in desert areas at the base of surrounding mountain scarps. It is a gentle slope at the foot-hill areas. A large pediment lies on the southern flank of Atlas mountain in the northwestern part of the Sahara desert in Africa.

Bajada :

It is a depositional plain formed by the joint depositional work of wind and water in the desert area at the base of the surrounding scarps and made up of alluvial materials laid down by the intermittent streams. These are found at the foot-hill regions of Atlas mountain in Africa.

Question17. Classify Coastal Plains.
Answer:

Coastal plains may be classified as follows :

(1) Depositional Coastal Plains :
In the coastal regions, most waves and winds often drive beach materials, mud, sand, and deposit them on the continental shelf along the coastline. In process, coastal plains rise in the form of sandy coastal plains, mud flats, tidal and estuarine lowlands.

(2) Emerged Coastal Plains :
Emerged coastal plains are recently emerged from the sea and found near the continental shorelines. They are caused by the uplift of the continental shelves. Parts of the eastern coastal plain of India are supposed to have originated due to coastal uplift.

WBBSE Class 9th Geography Chapter 4 Notes

(3) Submerged Coastal Plains :
The margin of the continental plate may subside because of isostatic adjustment due to accumulation of sediments Water depth over the continental shelf remains shallow, but the sediment deposits may reach thicknesses of thousands of metres the continental margins experience submergence. During submergence marine clay, marl (lime mud) and sand are being deposited in layers forming coastal plains.

Usually coastal plains formed on submerged coast are narrower and those on emerged coast wider. The narrowness or broadness of a coastal plain vary in their surface features for several factors : rock-bed structures, nature and degree of uplift and the type of land on which it lies.

Question18. What are the features of young fold mountain?
Answer:

Features of Young Fold Mountains :

(1) The young fold mountains consist of a series of parallel ranges with deep valleys between them. The mountain ranges have high peaks covered with snow.

(2) In some places, high plateaus lie between the mountain ranges, for example, the plateau of Anatolia in Turkey and the plateau of Tibet. These are called the intermontane plateaus.

(3) The mountain regions are areas of crustal instability. This makes these regions liable to earthquakes and volcanic eruptions.

(4) There are narrow gorges and canyons and high waterfalls in these mountain regions.

(5) These mountain regions have many glaciers and attract tourists due to their scenic beauty.

Chapter 4 Geomorphic Processes And Land Forms Of The Earth 5 Marks Questions And Answers

Question 1. What is a mountain? Classify mountains according to the mode of origin.
Answer:

Definition Of Mountain: A mountain is an extensive area of the earth’s surface which rises considerably above its surroundings with sharp pointed peaks, deep gorges and steep slopes or uneven sides. In general, mountains rise to comparatively high altitudes more than 1000 m.

Classification: Mountains can be classified into 4 types according to the mode of formation –

(1) Fold mountains:
The mountains which are formed by folding of sedimentary rock strata due to the forces of compression are called Fold Mountains.
Examples: The Himalayas the Alps, the Andes and the Rockies.

(2) Block Mountains:
Block or fault mountains are tectonic in origin. The mountains which are formed by blocks of earth’s crust or rock bed developed by tensional force and faulting are known as Block mountains.
Example: – The Vindhyas, The Satpuras etc.

(3) Volcanic Mountains:
Tall, conical or dome-shaped mountains which are formed by the accumulation of lava, ash, dust and liquid mud as acted via avert round the mouth of volcano in successive layers called Volcanic mountains or mountain of accumulation.
Example:
The vesuvius in Italy
Fujiyama in Japan
Barren Island in India.

(4) Residual Mountains:
Residual or Relict mountains are the products of weathering, erosion and denudation.

The mountains which are formed by the remains of erosion of highlands, mostly resistant rocks are known Residual or relict Mountains.
Examples:- The Eastern Ghat, The Nilgiri, The Parasnath, etc.

Question 2. What is Fold Mountain? Write in brief about the origin of Fold Mountains.

Or, When are Fold Mountains formed? State the plate tectonic theory regarding the origin of the fold mountains.

Or, “Plate movements are considered as the main reason responsible for the formation of fold Mountains” – Explain.

Or, Explain the origin of fold mountain according to Plate Tectonic Theory with an example.

Answer: The mountains which are formed by folding of sedimentary rock strata due to forces of compression are called Fold Mountains.

Origin:

According to the geologists, the following theories are regarded to the origin of the fold mountains –

Class 9 Geography Chapter 4 WBBSE

(1) Geosyncline theory – This theory is divided into 3 parts:-

(1) Lithogenesis:

In the past where the shallow geosyncline seas are located the rivers which drains into that sea deposited sediments comes with it. That sediments transformed into sedimentary rock due to the pressure of layers and heat of the interior which took many centuries.

(2) Orogenesis:

When the movement of the land masses hear that shallow sea takes place in opposite direction (towards each other), a tremendous pressure is created which causes the sedimentary rocks to be folded to form fold mountains. Example- The Himalayas.

(3) Gliptogenesis:

The fold mountains are still rising due to the movement of landmasses and their peaks are being eroded.

Plate tectonic theory:

Modern geologists approve the plate tectonic theory regarding the origin of the mountains. It states that the earth is made up of different plates. They different in respect of size, shape etc. These plates float on the asthenosphere. As these plates have tendency to move they sometimes collide with each other. These are caused due to the earth’s movement in the interior. So, when they collide, horizontal pressure pushes the rock beds to bend to form fold mountains. The convergence and consequent collission of plates may take place on the following three occassions :

(1) The convergence of two Continental plates produces a chain of mountains like The Himalayas.

(2) The convergence of two oceanic plates results in the formation of oceanic ridges and island arches.

(3) The convergence of continental plate and oceanic plate produces cordilleras like the Andes, the Rockies, etc.

Continental drift theory:

German scientists Alfred Wegener has given continental drift theory regarding the origin of the fold mountains. According to him, the primitive landmasses were a single unit called Pangea. This landmass, when time passed, broke into many pieces due to natural forces. As these broken parts drifted apart, horizontal pressure (compression) took place on rock beds and folds were found formed. This folded landform is known as fold mountain.

Question3. Explain the origin of Block Mountains with examples and sketches.
Answer:

Origin of Block Mountains

The mountains which are formed by the blocks of the earth’s crust or rock bed developed by the tensional force and faulting are known as Block Mountains.

Formation :

Block mountains are formed due to forces of tension. Owing to the intense tensional force, the rock strata may break, giving rise to fracture and cracks. When the broken parts are displaced on either side of the fracture a fault is formed.

A block, between two parallel faults may sometimes rise up, or the land on either side may sometimes fall down below; the upstanding landmass then forms a mountain known as Block Mountain or a Horst. These mountains have broad flat tops and steep sides. These mountains are also called Fault Mountains as they are formed by faulting.

Class 9 Geography Chapter 4 WBBSE

Rift Valley :

When a block is thrown down between two parallel faults a rift valley is formed. A rift valley is a long and narrow valley with steep edges.

Examples :

(1) The Satpuras,
(2) the Vindhyas of India,
(3) the Black Forest Mountain in Germany,
(4) the Vosges in France are the important Block Mountains of the world.

(1) The Narmada valley in India,
(2) the Rhine valley in Europe and
(3) the Great Rift Valley in Africa are some of the important Rift valleys in the world.

 

Question 4. Classify and describe the different types of plateaus with examples.
Answer:

Based on structure and formation plateaus can be divided into major following groups –

Intermontane Plateau:

The word ‘Intermontane’ means between mountains. The plateaus which have mountain rims round their surrounding are known as intermontane Plateaus.

Formation:

Due to the lateral pressure of the rocks the rock beds fold to form fold mountains. When these fold mountains are formed the area between the mountains also rises. As the area is covered or surrounded by mountains it is called Intermontane Plateau.

Example:

(1) Tibetian Plateau between The Himalyas and The Kunlun
(2)Anatolian Plateau between The Pontic and The Taurus.

Dissected Plateau:

The plateau worn down and made into blocks by natural agents is known as Dissected Plateau.

Formation:

In the humid highlands stream action and glaciation cut deep narrow valleys in old surfaces and its tributaries and distributaries made this highland into several blocks. So this formed a flat plateau. This is known as Dissected Plateau.

Class 9 Geography Chapter 4 WBBSE

Example:

(1) Chottanagpur Plateau of India
(2) Colorado plateau of U.S.A.

(3) Lava Plateau:

The plateau formed by the accumulation of lava comes out of volcano is known as Lava Plateau.

Formation:

From the volcano sometimes the lava occur in nearly horizontal flow of variable thickness. The sucessive layers spread over the land in great sheets which have since hardened to take the formation of a plateau called lava plateau. Lava plateaus are called volcanic plateaus as they are formed by Volcanism.

Example:
(1) The plateau of Maharashtra
(2) Plateau of Bolivia in South America.

Question5. Classify Volcanic mountains with ‘examples.
Answer:

On the basis of nature of eruption

(1) Active volcano
They erupt often like Vesuvius in Italy, Mauna Loa in Hawaii.

(2) Dormant Volcano
When eruption has not occured for some time but it can occur any time like Fujiyama in Japan.

(3) Extinct or dead volcano
When eruption had occured for a long time previously and no eruption will occur in future it is called Dead Volcano like Mt.Popo in Myanmar.

On the basis of shape and form:

(1) Shield volcanic mountain:

These are built from massive accumulation of lava which flows out from the central vent before hardening and thus builds a mountain which is broad and gently sloping. These are known as Dome shaped or shield volcanic mountains.
Example: Islands in Hawai show such mountains.

Class 9 Geography Chapter 4 WBBSE

(2) Conical-shaped volcanic mountain:

It is formed due to violent eruption and resembles a cone.
Example: Japan has many such volcanic mountains.

(3) Explosive vent volcanic mountain:

With a violent explosion when a big hole or depression is formed to give rise to a volcanic mountain, such mountains are formed.
Example: In Iceland, such volcanoes are seen.

(4) Composite cone volcanic mountain:

When over a long period of time many eruptions had take place, forming many craters other than the main crater,
such mountains are formed.
Example: – Popocatepeti mountain in Mexico.

Class 9 Geography Chapter 4 WBBSE

Question6. Classify, describe different kinds of plains according to the mode of formation.
Answer:

Plains may be grouped into three broad categories according to their mode of formation. These are –

(1)Alluvial Plains:

The plain which is formed by the deposition of alluvium brought by a river, which is a levelled track, is known as Alluvial Plain.

Classification:

It can be classified into 2 groups –

Flood Plain:

The plains which are formed by the deposition of sediments brought by the rivers during flood are called Flood Plains.
Example:- The Ganga-Brahmaputra flood plain, largest aggradational plain, is the best example of flood plain.

Deltaic Plains:

The plains which are formed by the deposition of the rivers on their deltaic regions are known as deltaic plains.
Example:– The deltaic plain of the Ganga-Brahmaputra is a spectacular example.

(2) Coastal plains:

Audrey N.Clark defines coastal plains as “any comparatively level land of low elevation, sloping gently seaward and bordering the sea or ocean, resulting from the deposition of sediment washed down from the land or from denudation by the sea or by the emergence of part of the continental shelf”.

Example – East-coastal plain and the west-coastal plain of India.

(3) Peneplains:

An almost featureless, gently undulating plain land produced by the agents of erosion is called peneplain.
Example – The plains of finland.

Question 7. Classify and describe different kinds of plains according to the mode of origin.
Answer: According to the mode of origin plains can be grouped into 3 categories They are –

(1) Tectonic Plains:
Tectonic plains are formed by the movements of the tectonic plates.

Example:
(1) Russian Platform (Structural Plain)
(2) Tarim basin (Depressed Plain).

(2) Depositional Plains:
Depositional plains are formed by the depositional work of river, glacier, wind, wave, etc.
Example:-
(1) Alluvial plain, Flood plains and coastal plains by the work of rivers,
(2) Lacustrine Plains result from the filling of lake beds by river-borne loads.
(3) Bajada is formed by the mergess of alluvial fans laid down by swollen streams where they debouch on a plain at the base of a mountain range in an arid or semiarid area.
(4) Loess plain is formed by the deposition of sand brought by the wind.
(5) Glacial plains are the products of Glacial Deposition.

(3) Erosional Plains:

Erosional plains are formed as a result of weathering, erosion and denudation. It gave rise to several types of plains –

WBBSE Solutions Guide Class 9

(1) Peneplain:

It is gently sloping, undulating plain produced by the agents of erosion. Agents of erosion are river, glacier, wind, etc.

(2) Karst Plains:

A karst plain is formed by the action of underground water dissolving the regions made of limestone.

(3) Peidmont plain:

It is a plain formed at the foot hills of the mountains due to erosion and denudation.

Question 8. Describe the importance of mountains.
Answer:

The social, financial, cultural and political condition of any country is affected by mountains.

The importance of mountains are –

(1) Natural Barrier:

Mountain as a natural barrier protects the country from foreign invasion or foreign attack. E.g. – The Himalayas from a very long time protects India.

(2) Source of Rivers:

Mountains are mainly covered by snow. Hence it originates many rivers which are very useful for humans and animals.

(3) Effect on Agriculture:

As a mountainous region, it is not suitable for agriculture. But terraced forming is practised on mountain slopes and rice, tea, wheat, fruits are grown here.

(4) Production of HEP:

The rivers originated from the mountains are very suitable for hyde! power generation.

(5) Rich Wealth of Natural vegetation:

High mountains have rich forest cover. From these forests, wood of high quality can be obtained.

(6) Mineral resources:

Mountains are rich in minerals. The mountainous or rocky part of mountains are rich in minerals. The Appalachian mountain of America is rich in coal, iron and petroleum.

WBBSE Solutions Guide Class 9

(7) Tourist abode:

Having high elevation usually, mountainous regions are tourist attractive. The Jammu and Kashmir region, the Darjeeling region are famous.

(8) Influence on Transport and Communication:

As a mountainous region, it is unsuitable for making railways and roadways. The rivers of this region are very swift flowing so they are not suitable for navigation.

(9) Influence on population:

Scarcity of food, transport and other necessary things made the mountains sparsely populated.

Question 9. Describe the forces that originate landforms from the earth’s crust.
Answer:

The various landforms on the surface of the earth are produced by the interaction of two processes or forces. These are :

1. Endogenic Forces:

This forces are generated in the interior of the earth and cause mountains, plateaus, etc. to subside. These endogenetic forces are also called internal processes. On the basis of intensity, these forces are divided into two subgroups.

Sudden Endogenic Forces:

The main forces in this group are volcanic or of earthquakes. Earthquakes and volcanoes are a natural process of readjustment of the earth’s crust along a weak zone.

Diastrophic Forces:

These forces act very slowly. The diastrophic forces which aré the result of the internal process also called Geotectonic Forces or
Tectonic Movements. These are sub-divided into 2 types

Epeirogenic Movements:

These are the vertical movements of the earth’s crust. These movements are called the epeirogenic movement after the Greek word ‘periods’ meaning a continent. These movements are called the continent-building movements.

WBBSE Solutions Guide Class 9

Orogenic Movements:

These are the horizontal movements of the earth. These movements may be caused by compression or tension. Compressional forces result in the formation of fold mountains. These movements come from the Greek word ‘Oros’ means mountain.

2. Exogenetic Forces:

The forces are also called the external processes. The external processes are those which act on the surface of the land. These are the agents of denudation like rivers, glaciers, wind and waves. These agents were down the rocks on the surface and the differences in the rate of their denudation processes produce different features, like valleys, lowlands ridges etc. Hence these forces are also called Gradational Forces.

Question 10. Write the importances of Plateaus.
Answer:

The main importances of Plateaus are –

(1) Richness in Minerals:

Ancient plateaus are very rich in minerals. The southern plateau of India is rich in iron, coal, manganese, gold etc. The Chottanagpur Plateau region is also known as “Store house of minerals”. Except petroleum all minerals are present in Chottanagpur plateau region.

(2) Transport System:

The surface is broken so making of railway system is very difficult. The rivers are very swift flowing so they are not navigable. Hence, transport system is very weak in plateaus. But roadways are enough developed for transport.

(3) Effect on Temperature:

The plateau region of Uttar Pradesh remains cool also during the summer season. The Intermontane plateau as a rain shadow region remains dry all round year.

(4) Agriculture:

Unfertile land, less rainfall and less facility of irrigation make the plateaus unsuitable for cultivation. However, the lava plateau contains black soil which is very suitable for wheat cultivation.

(5) Natural vegetation:

As devoid of agriculture, vegetation is usually found. Plateau having high rainfall have forest and area having low rainfall have grasses. This region is suitable for animal rearing.

(6) Absence of population:

Unfertile land, lack of transport makes the apa region sparsely populated. But richness of minerals attracts people.
Example: The region of Raniganj, Jharia, etc.

WBBSE Solutions Guide Class 9

(7) Industries:

Mineral based industries are usually developed in this region.

Question 11. Write the importance of Plains.
Answer:

In human culture and his financial development plains have enormous contribution.

The importance of plains can be summed up under the following heads –

(1) Development of Human Culture:

Due to many facilities human culture is developed in plains from ancient times.
Example: The Sindh, The Ganga, etc. region is the best example.

(2) Development of Agriculture:

The surface of the plains is very fertile hence agriculture is well-developed here. Here well or tap can easily be made. Hence, irrigation facility is also present here.

(3) Transport facility:

Plains have levelled surface. Roadways, railways are | easily made here. Rivers also flow slowly, hence it is navigable. So transport is well-developed:

(4) Industrial development:

Plains provide raw material, drinking water, trans- port facility, cheap labour and huge market for finished goods. So, industries are well-developed here.

(5) Enormous population:

Agricultural facility, presence of industries, transport facility and other necessary facilities make plains densely populated.

(6) Presence of cities:

Dense population, presence of transport facility develop world’s largest Industrial and Business centres in plains. Kolkata, Kanpur, Chicago, etc. are present on plains.

(7) Fear of attack:

Devoid of natural barrier makes plains a fear of attack. Transport facility and financially sufficient plains attract people. Hence from ancient time it is an area of battle.

Class ix Geography Book WBBSE

Question 12. Distinguish among mountains, plateaus and plains.
Answer:

Difference among mountains, plateaus and plains

Mountains	Plateaus	Plains
(1) A mountain is an extensive area which rises considerably above its surroundings areas.	(1) Flat-topped, extensive highland is known as a plateau.	(1) Extensive area of level or gently undulating lands are called plains.
(2) Mountains have an elevation of more than 1000m.	(2) It is less than 1000m high.	(2) They usually have very low altitude.
(3) A mountain has sharp pointed peaks.	(3) It has flat top.	(3) It doesn’t have any top but its surface is extensively large.
(4) It is very steep-sided.	(4) It is of low steep sides or gentle sloping.	(4) It is very gently sloping and fiat.
(5) Its surface is very undolating.	(5) Its surface is less dulating.	(5) Itsurfaceisgently undulating.
(6) It contains new and less hard rocks.	(6) It contains very old or ancient hard rocks.	(6) It contains new and very soft rocks.
(7) It is unfertile land.	(7) It is comparatively less fertle.	(7) It is very fertile.
(8) They are sparsely populated	(8) They are less populated than plains.	(8) They are highly populated.
(9) They are rich in mineral resources.	(9) They are highly rich in mineral resources.	(9) They have scarcity of mineral resources.
(10) They have less temperature.	(10) They have comparatively low-temperature.	(10) They have high temperature.

 

Question 13. Explain geomorphic processes.
Answer:

Geomorphic processes :

(1) Geomorphic processes are endogenic and exogenic forces which cause physical stresses and chemical reactions on the earth’s materials and bring changes in the configuration of the earth’s surface. Diastrophism and volcanism are  endogenic forces or processes. Weathering, mass wasting, erosion, deposition are exogenic geomorphic processes.

(2) Geomorphic agents are those exogenetic elements of nature which are capable of acquiring and transporting earth’s material. They are water, snow, ice, wind, sea waves, underground water, etc. When these elements become mobile due to difference in gradients they remove the material and transport them over long distances and then deposit them in depressions.

(3) A process is a force which is applied on earth’s material affecting the same.

(4) An agent is a mobile medium which removes, transports and deposits earth’s material. The major agents are running water, moving snow and ice masses (gla- ciers), groundwater, wind, sea waves, currents, etc. They are called geomorphic agents.

 

Question 14. Examine the various forces which are the causes of exogenic processes.
Answer:

Exogenic processes :

(1) Atmosphere provides energy to all the exogenic processes. This is the ultimate energy of the sun. Tectonic factors also determine the amount of energy due to gradients.

(2) Gravitational force acts upon all sloping materials and tends to produce movement of matter or material to down slope direction. This induces deformation.

(3) They are the separating forces which break rocks and earth’s other materials. These separating forces also called shear stresses result in angular dis-placement or slippage.

(4) Along with gravitational stress, earth’s materials are also subjected to molecular stresses that are caused by numerous factors like temperature changes, crystallisation and melting.

(5) Chemical processes lead to loosening of bands between grains, dissolving of soluble minerals or cementing of materials.

(6) Basic reason leading to weather, mass movement, erosion and deposition is the development of stresses in the body of earth’s material.

(7) Earth’s climatic divisions are different on earth’s surface, exogenic geo-morphic processes also vary from place to place and from region to region.

(8) Temperature and precipitation are two basic climatic elements. They control various processes.

(9) Other factors responsible for changes in the landforms are intensity, magnitude and frequency of action of exogenic geomorphic processes.

Question 15. Explain diastrophism.
Answer:

Diastrophism :

All the processes that move, elevate or build up portions of the earth’s crust come under the preview of diastrophism. They are :

(1) Orogenic processes:

Mountain building through folding. They affect narrow belts of the earth’s crust.

(2) Epeirogenic processes:

Uplift and warping of large parts of the earth’s crust.

(3) Earthquakes:

local and relatively minor movements.

(4) Plate Tectonics:

horizontal movements of the crystal plates or tectonic plates. —

In orogeny, the crust is severely deformed into folds.

Epeirogeny leads to simple deformation. Orogeny is a mountain-building process while epeirogeny is a continental-building process.

(1) Crust is faulted or fractured due to the processes of orogeny, epeirogeny, earthquakes and plate tectonics.

(2) All these processes cause pressure, volume and temperature changes. They, in turn, form metamorphose rocks.

Question 16. Describe systematically the vertical and horizontal movements originated in the earth’s crust. Give relevant references from the Indian subcontinent.
Answer:

Epeirogenetic forces :

The word epeirogentic is drawn from a Greek word Epeiros meaning continent. In other words, the continents either rise or sink under the influence of these forces. Accordingly, there are two types of epeirogenetic forces :

(1) Upward Forces :

A part of earth’s crust rises in relation to its surroundings under these forces. This process is known as uplift.

(2) Downward Forces :

A part of earth’s crust sinks or subsides under the influence of downward forces. This process is known as subsidence. The epeirogenetic movements on a large scale build up continents but they do not disturb the horizontality of the rock strata. At the most the strata may be
inclined or tilted.

(3) Orogenetic or Horizonal Forces :

The word Orogenetic has been derived from a Greek word ‘Oros’ meaning mountain. Thus, they are mountain-building forces acting ina horizontal direction. These movements are responsible for greatly disturbing the horizontal arrangement of rock strata. They are of two types:

(1) Compression:

It is a force which pushes against a body from opposite sides. The rocks change their state when compressed or squeezed. These forces result in folding of the rock strata.

(2) Tension:

It is a pulling force. The rocks are pulled apart by tensional forces acting from within the earth. These forces are responsible for causing faults in the earth’s crust.

Question 17. Describe briefly how the different kinds of folds are produced.
Answer:

Types of folds :
The main varieties of folds are as follows :

(1) Symmetrical folds:
Are simple folds, the limbs of which dip uniformly. The axial plane is essentially vertical and the beds dip in equal angles from or to- wards the axis. These are formed when compressive forces work regularly but with moderate intensity.

 

(2) Asymmetrical folds:
Are more common than symmetrical folds. They are characterized by unequal and irregular limbs. One limb of the fold dips more steeply than the other in unequal angles.

 

(3) Overturned folds:
Are those folds in which one limb of the fold has been tilted beyond the vertical. Both limbs dip in the same direction, though not necessarily in the same angle.

 

(4) Recumbent fold:
Is one in which the axial plane is essentially horizontal. Such folds are formed when the compressive forces are so strong that both the limbs of the fold come parallel as well as horizontal.

 

 

(5) Isoclinal folds:
Are those in which both limbs are essentially parallel, re- gardless whether the fold is upright, overturned or recumbent.

 

 

(6) Monocline, the simplest of folds:
Is one limbed tiexure on both sides of which the strata are either horizontal or dip uniformly at low angles. A monocline is sometimes described as half a fold. It may be pointed out that vertical force and movements are held responsible for the formation of monoclinal folds.

 

(7) Plunge fold :
A fold with an inclined axis is called a plunging fold. The angle between a fold axis and the horizontal is the plunge of the fold.

(8) Fan fold :
A fan fold is one in which both limbs are overturned. In the anti-clinal fan fold, the two limbs dip towards each other and in the synclinal fan fold, the two limbs dip away from each other.

(9) Box fold :
A box fold is one in which the crest is broad and flat, two hinges are present, one on either side of the flat crest.

(10) Chevron fold :
A chevron fold is one in which the hinges are sharp angular and limbs are straight.

(11) Closed and open fold :
A closed or tight fold is one in which the deformation has been sufficiently intense to cause flow of the more mobile beds so that these beds thicken and thin. Conversely an open fold is one in which the flow has not taken place.

(12) Drag folds :
Are formed when a strong bed slides past a weak bed. Such minor folds may form on the limbs of larger folds because of the slipping of beds past each other.

Question 18. Name the different types of faults and explain them.
Answer:

Faulting :

As compression results in folding so tension results in faulting. As the force of tension increases in the earth’s crust, a stage comes when the rock strata cannot withstand the force and the crust breaks. Consequently one side of the rock strata moves up or down relative to the other side. The break or rise and sink is along a line of weakness or along a plane of fracture. The plane along which the fault takes place is known as Fault Plane. One part of a fault is thrown upwards and is known as upthrown side. Similarly, the downthrown part is called downthrown side. The part which is exposed as a result of fault is known as Fault Scrap.

Types of Faults :

From the point of view of position and movement, faults can be of the following types :

(1) Normal fault :

In a normal fault, the blocks on either side of the fault plane move in opposite directions because the forces of tension act in opposite direc- tions. The hanging wall slips downwards. The fault plane is either vertical or has a very steep slope. This fault generally takes place due to tension in the upper part of the crust.

 

(2) Reverse fault :

This fault is produced by compression. In such a fault, the blocks along the fault plane move towards each other. The hanging wall slips up. The slope of the fault plane is gentle.

(3) Thrust fault :

When one block of the fault rises over the other along the fault plane, it is known as thrust fault. This type of fault is produced by compres- sion and is often accompanied by folds.

(iv) Step fault :

When an area suffers several parallel faults in such a way that the crust is broken into thin strata and the slope is on one side, the fault looks like a flight of stairs. Such a fault is called step fault.

Question 19. What is Gradational Process? Discuss in brief with its types.
Answer:

Gradational Process :

‘Gradation’ means the process of bringing the earth’s surface to a uniform level. The process of levelling the earth’s surface is known as gradation. Gradational processes are continuously engaged in remov- ing the vertical irregularities created by endogenous processes through denudational (both weathering and erosion) and depositional activities.

Agents of Gradational Process :

Gravity is the driving force behind the movement of material from high areas to low areas, thus, reducing the height differences between them. But before this can happen, the rocks have to be eroded (broken) into small pieces. The erosional, transportation and depositional works of running water or rivers, glacier, wind, groundwater and works of ocean waves and shore currents results in gradation.

Processes :

Evidently, gradation involves three different processes—

(1) The process of wearing down (erosion) uplants,

(2) The process of transporting (transportation) the eroded materials,

(3) The process of filling up (deposition) lowlands.

The three main processes involved in gradation are erosion, transportation and deposition of the eroded material. This process of erosion, transportation and deposition is known as gradation. Hence Gradation = Erosion + Transportation + Deposition.

Types :

It is clear that gradation is achieved by simultaneous processes of the following three processes-
(1) Degradation,
(2) Aggradation and
(3) Biotic Processes.

(1) Degradation Definition :

Degradation is the general wearing away of the land surface by external forces. It is achieved by the breakup and carrying of the broken rock material.

Processes of Degradation :

The agents of degradation work through three successive processess-
(1) Erosion of the elevated surface,
(2) Transportation of the eroded. rock and
(3) Mass-wasting.

Geography Ch 4 Class 9 WBBSE

Agents of Degradation :

Degradation or denudation, as it is called, too, is eroded and carried out by different degradational agents like (erosion and transportation work) weather, running water, glaciers, winds, sea waves, underground water and living beings. The agents, i.e. forces of degradation work in a destructive manner.

(2) Aggradation

Definition :

When landforms of low elevation are increased in height, the pro- cess is known as aggradation. It is also known as deposition. Actually aggradation is the process of filling up low-lying areas of the earth to give them a levelled up surface.

Agents of Aggradation :

Various forces are ever at work to achieve aggradation of depressed areas of the earth. Strangely, these forces are the very agents
that carry out degradation of elevated parts of the earth. Important agents of aggradation are
(1) Depositional work of flowing or running water,
(2) Depositional work of winds.
(3) Depositional work from glacier.
(4) Depositional work of groundwater.
(5) Depositional work of sea waves etc.

Associated Landforms :

(1) Flood plains,
(2) Formation of delta,.
(3) Moraine,
(4) Formation of stalactite and stalagmite,
(5) Loess etc. are the important landforms created by the aggradation processes.

(3) Biotic Processes :

This includes the action of animals and insects, vegetation and man.

Geography Ch 4 Class 9 WBBSE

(1) Man :

The quarrying, mining, deforestation and indiscriminate cultivation of land are some of the important actions of man.

(2) Plants :

The long and tenacious root fibres of the plants work down into the cracks of rock.

(3) Animals :

There are millions of animals and insects such as dogs, rabbits, rats, jackals, termites etc. which consume large quantities of rock and soil for making their habitats and for extracting food.

Question 20. State the mechanism of origin of volcanic mountains.
Answer:

Mechanism for the origin of Volcanic Mountains :

The mechanism of volcanicity (volcanism) and volcanic eruptions which are responsible for the formation of volcanic mountains is closely associated with serveral interconnected processes such as—

(1) temperature with increasing depth of 1°C per 32m due to heat generated from the disintegration of radioactive elements deep within the earth,

(2) origin of magma because of lowering of melting point caused by reduced- Lesa MS ace Ocho eae wee tion in the pressure of overlying superincumbent load due to fracture caused by spliting of plates and their movement in opposite direction,

(3) origin of gases and vapour due to heating of water,

(4) the ascent of magma forced by enormous volume of gases and vapour and

(5) finally the occurence of volcanic eruptions.

 

Question 21. State the characteristics of Fold Mountains.
Answer:

Characteristics of Fold Mountains :

(1) Fold mountains consist of great masses of folded sedimentary rocks whose thickness is often as much as about 12 km.

(2) Various types of folds are present in fold mountains.

(3) Complex folding is more common in fold mountain.

(4) Simple folding gives rise to mountains and valleys. The anticlines become the mountains and the synclines the valleys. Simple fold mountains are rare.

(5) Faults are also common in fold mountains.

Geography Ch 4 Class 9 WBBSE

(6) Fold mountains are usually made of sedimentary rocks.

(7) Fossils are common as they origin from the seas.

(8) Most of the peaks are conical.

(9) Many of the world’s largest mountain chains exist beneath the sea. Some of these are revealed as island arcs, as in the West Indies, and in the west and south-west Pacific Ocean.

Question 22. Give five differences between volcanic mountains and residual mountains.
Answer:

Difference between Volcanic Mountains and Residual Mountains :

Volcanic Mountains	Residual Mountains
1. Geological process of origin
(1) Endogenetic/Endogenic processes which originate from within the earth (e.g. Diastr-ophism and Vulcanicity) are involved in the formation of these mountains.	(1) Exogenetic/exogenic processes which arise at or near the surface of the earth (weathering erosion and denudation) are involved in the formation these mountains.
2. Time taken for the formation
(2) Volcanic Mountains are formed within a short period.	(2) Residual mountains are formed over very long periods.
3. Products
(3) Volcanic mountains are products of accumulation.	(3) Residual mountains are products of erosion.
4. Classifications
(4) Usual classification of volcanic mountains are made of the basis of the type of volcanic cones such as (a) Shield volcanoes, (ii) Cinder Cones, (iii) Composite Cones, (iv)Plug Dome.	(4) Residual mountain are of different types, namely (a) Monadnocks, (b) Buttes, (c) Inselburg, etc.
5. Shapes and appearance
(5) The volcanic mountains are conical in shape.	(5) The residual mountain are dome-like in appearance.

 

Question 23. Discuss the features of a plateau.
Answer:

Features :

(1) The elevation of most plateaus of the world exceeds 300 metres. Height above sea level, however, is not the sole factor in classifying a landform as a plateau, although a plateau has generally high relief. In South America, a plateau is called ‘altiplano’ (alt : high and plano : plain).

(2) A plateau is a region of horizontal rock structure with high relief.

(3) A plateau has an uneven surface top extending over a large area.

(4) A plateau forms a steep escarpment at least on one side, marking the ‘ f change to a region of lower elevation.

(5) Most plateaus are tectonic in origin. Folding, warping and faulting of the  continental plates may cause to uplift broad areas to form plateaus.

(6) Some plateaus are the results of volcanism. Outpouring of magma through fissures may form a plateau.

(7) Plateaus are quite often produced by the processes of erosion.

 

When it is an elevated upland with an extensive level surface and generally de-scends steeply to the surrounding lowland, it is called Tableland. The Bolivian Plateau rising thousands of metres above sea level like a tabletop is an example.

WBBSE Solutions for Class 9 Geography and Environment

• Chapter 1 Earth As A Planet
• Chapter 2 Movement Of The Earth Rotation & Revolution
• Chapter 3 Determination Of The Location Of A Place On Earth Surface
• Chapter 5 Weathering
• Chapter 6 Hazards And Disasters
• Chapter 7 Resources Of India
• Chapter 8 West Bengal
• Chapter 9 Map & Scale