WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains

WBBSE Chapter 4 Landforms Topic A Mountain-Long Question And Answers

Question 1. Describe the origin of fold mountains concerning the Plate Tectonic Theory.
Answer:

Origin of fold mountains concerning the Plate Tectonic Theory:

The most recent scientific theory explaining the origin of fold mountains is the Plate Tectonic Theory. Leading geomorphologists such as Mackenzie, Parker, and Morgan endorse the Plate Tectonic Theory in relation to the formation of fold mountains.

Plate movement:

  • According to this theory, the Earth’s crust is made up of various plates. The average depth of the plates is almost 70 km for the oceanic ones and almost 150 km for the continental ones.
  • These plates are floating on the mantle which is in a viscous state. Tremendous heat and pressure within the Earth generate convection currents. These currents cause the movement of the tectonic plates.

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Origin of Fold Mountains:

The following steps occur during the formation of a fold mountain-

  1. There exists a constant convectional current in the Asthenosphere, on which plates are floating. As a result of this current, the plates start moving slowly at an average speed of 2-3 cm per year.
  2. When two plates move towards each other, they are known as converging plates. In such a situation, the oceanic plate will move below the continental plate as it is heavier.
  3. The thickest deposits of sedimentary rocks are generally found at the edges of the continents. As the plates collide with each other, the accumulated layers of rocks crumple and fold like a tablecloth that is pushed across a table.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Origin of fold mountains with references to the plate tectonic Theory

Example:

The Himalayan Mountain Range originated as a result of the collision between the Indian plate and the Eurasian plate.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains

Question 2. Describe the origin of block mountains.
Answer:

Origin of Block Mountains:

  • Tectonic movement sometimes causes cracks or fractures in the rigid lithosphere. One side of this crack subsidies, resulting in a fault.
  • When the landmass between any two fractures rises comparatively higher than the surrounding level, a block mountain is developed.
  • Again, when the landmass between any two faults sinks comparatively lower than its surrounding level, the comparatively higher landmasses form block mountains.

The following steps take place to form a block mountain-

  1. The landmass between any two parallel faults moving upwards due to the pressure (upthrust) forms block mountains. These are also called horses.
    • Example: Satpura Range in Central India.
  2. If the landmass between two parallel faults moves downwards instead of upwards, then the two elevated landmasses beside the subsided region, are both block mountains.
    • Example-Vosges in France and Black Forest in Germany are two block mountains of this type.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Formation of block mountains

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Question 3. Describe the origin of volcanic mountains.
Answer:

Origin of volcanic mountains:

The formation of a volcanic mountain is a slow and gradual process that can be divided into stages. The different stages involved are discussed below-

  1. First, due to an abnormal increase in temperature at a depth of 80 to 160 km, in the interior of the Earth, rocks melt to form magma and enormous pressure is generated.
  2. Then, this magma gets transported to the Earth’s surface through fissures or vents and spreads there as lava along with ashes, lapilli and volcanic bombs.
  3. The pyroclastic materials emitted from the interior of the Earth get deposited around the fissure or crater and gradually increase in height as well as volume to form a conical-shaped volcanic mountain.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Origin of Volcanic mountains

Thus, volcanic mountains are formed mainly due to the deposition of pyroclastic materials. Igneous mountains or volcanic mountains developed mostly near the plate boundaries-the convergent, the divergent or the transitional plate boundaries.

Question 4. Discuss the characteristics of fold mountains and block mountains.
Answer:

Characteristics of fold mountains:

The characteristics of fold mountains are as follows-

  • Type of fold: Fold mountains have different kinds of folds in their rock beds. These are- symmetrical fold, asymmetrical fold, overfold, recumbent fold, overthrust fold, nappes, etc.
  • Anticlines and Synclines: Folds are collectively formed by both anticlines and synclines.
  • Type of rock: Fold mountains are mainly formed out of sedimentary rocks. As a result, fossils are found in fold mountains.
  •  Shape of the peak: The peaks of most of these mountains are usually cone-shaped. However, old fold mountains like the Aravallis have been exposed to erosion for a long time. So they have been lowered and their summits are rounded off.

Characteristics of block mountains:

The characteristics of block mountains are as follows-

  1. Slope: The two sides of a block mountain or the slopes along the faults are quite steep.
  2. Summit: The summit or crest of this type of mountain is a little flat.
  3. Height and extension: Block mountains are not as high as the fold mountains and do not extend over a large area.
  4. Associated features: Block mountains (horsts) are generally associated with rift valleys (grabens) and these mountains generally do not have any peaks.

Question 5. Explain the influence of mountains on human life.
Answer:

Influence of mountains on human life:

Mountains have a great influence on human life. These are discussed below-

  • Source of rivers: Most rivers originate from mountains. Rivers that originate from mountains generally create fertile plains.
  • Influence the climate: Relief rainfall occurs due to the presence of mountains. The climatic conditions on the windward side and on the leeward side of mountains are completely different.
  • Generation of hydroelectricity: Hydroelectricity is generated from fast-flowing rivers that originate on mountains. This aids in power generation and also in agriculture.
  • Forest resources: The soft wood that is available in the forests on the mountains, provides many human needs. Moreover, this region the primary areas for growing tea, fruits and herbs.
  • Tourist spots: Mountains are ideal locations to be developed as tourist spots.
  • Guard from external enemies: Countries that are bounded by mountains always enjoy a natural barrier against external enemies.
  •  Difficulty for carrying out agriculture: It is difficult to carry out agriculture in the mountainous region because of the height, the soil infertility and the overall difficult terrain.
  • Transportation is difficult: ‘It is difficult to develop a transportation system in the mountains. This makes life more difficult for the people residing in the mountains.

Question 6. How are landforms classified?
Answer:

Classification Of landforms:

In general, landforms can be classified into three types on the basis of altitude, shape, geological structure, slope, ruggedness, etc. of the land.

These are-

  1. Mountains
  2. Plateaus and
  3. Plains.

These three types can be further divided into many sub-classes.

They are-

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Landform

Question 7. What are the characteristics of a mountain?
Answer:

The characteristics of a mountain are as follows-

  1. Height: Generally the height of a mountain is more than 900 metres above sea level.
  2. Rough surface: The rocky and stony surface of the mountain is usually rugged and uneven in nature.
  3. Location and expanse: Mountains extend over a large area and are much higher than the surrounding level.
  4. Landforms: Gorges, deep valleys, and steep slopes are found in mountainous regions.
  5. Mountain peak: The topmost part of a mountain is called the peak. The mountain peaks remain covered with snow for most of the year.

Question 8. What are the characteristics of a fold mountain?
Answer:

Characteristics of fold mountains:

The characteristics of fold mountains are as follows-

  • Type of fold: Fold mountains have different kinds of folds in their rock beds. These are- symmetrical fold, asymmetrical fold, overfold, recumbent fold, overthrust fold, nappes, etc.
  • Anticlines and Synclines: Folds are collectively formed by both anticlines and synclines.
  •  Type of rock: Fold mountains are mainly formed out of sedimentary rocks. As a result, fossils are found in fold mountains.
  • Shape of the peak:
    • The peaks of most of these mountains are usually cone-shaped.
    • However, old fold mountains like the Aravallis have been exposed to erosion for a long time.
    • So they have been lowered and their summits are rounded off.

Question 9. Give examples of some important fold mountains.
Answer:

Examples of some important fold mountains in different continents are given in the following table.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains important of fold mountains

 

Question 10. What are block mountains?
Answer:

Block mountains:

  • Due to tectonic movement, sometimes cracks or fractures develop in the rigid lithosphere. One side of this crack gets depressed resulting in a fault.
  • When the landmass between any two fractures rises comparatively higher than its surrounding level, a mountain is formed which is referred to as a block mountain.
  • Again, when the landmass between any two faults sinks or gets depressed comparatively lower than its surrounding level, the comparatively higher landmasses look like mountains and are called block mountains.

Example: Satpura Range in India, etc.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Block mountains

Real-Life Scenarios Involving Mountain Ecosystems

Question 11. What are the characteristics of a block mountain?
Answer:

The characteristics of block mountains are as follows-

  1. Slope: The two sides of a block mountain or the slopes along the faults are quite steep.
  2. Summit: The summit or crest of this type of mountain is a little flat.
  3. Height and extension: Block mountains are not as high as the fold mountains and do not extend over a large area.
  4. Associated features: Block mountains (horsts) are generally associated with rift valleys (grabens) and these mountains generally do not have any peaks.

Question 12. What do you mean by rift valley?
Answer:

Rift valley:

  • Sometimes within the Earth’s surface, intense tectonic movement results in vertical cracks which eventually develop into faults.
  • When the landmass between any two parallel faults sinks downwards instead of going upwards, then it is called a rift valley.
  • Generally, rift valleys are associated with block mountains.

For example– the Satpura Range in Central India and the Rift Valley of the Narmada River are associated with each other.

Question 13. “Block mountains and rift valleys are two associated features.”- Explain.
Answer:

Block mountains and rift valleys are two associated features, because-

  1. The landmass between any two parallel faults may rise upwards to form a block mountain. In this case, there will be two rift valleys located on both sides.
  2. If the landmass between any two parallel faults remains at the same position while its adjacent landmasses subside, then also a block mountain is formed with two rift valleys on both its sides.
  3. If the landmass between any two parallel faults subsides, while the surrounding landmasses remain in the same position, then a rift valley is formed with two block mountains on either side.

Question 14. What are the differences between fold mountains and block mountains?
Answer:

The differences between fold mountains and block mountains are as follows-

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Differences between fold and block mountains

Question 15. What are the characteristics of a volcanic mountain?
Answer:

The characteristics of a volcanic mountain are as follows-

Shape:

These mountains are more or less conical in shape. The slopes surrounding this mountain are quite steep.

Crater: There is an opening at the top of this mountain called a crater. More than one crater is found in large volcanic mountains.

Type of rock:

  • The crater is connected to the magma chamber in the Earth’s interior through a vent.
  • The magma that reaches the Earth’s surface deposits around the crater and forms the mountain.
  • This is the reason why this mountain is formed of igneous rocks only.

Question 16. What are residual mountains?
Answer:

Residual mountains:

  • Due to the action of different exogenic natural forces (river, glacier, wind, sea waves, sunlight, rainfall, etc.), old mountains or soft rock-bedded highlands get partially eroded to form a plain whereas the relatively harder rock-beds are barely eroded and remain intact.
  • This type of eroded mountain are called a residual mountain.

Example- Aravallis in Rajasthan.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Residual mountain

Question 17. What are the reasons that heavy industries do not develop in hilly regions?
Answer:

The reasons that heavy industries do not develop in hilly regions:

  • The hilly regions are steep and have stony and rugged topography. The transport system is also not well-developed and mining is practised to a very limited extent.
  • Due to low population in the hilly regions, there is insufficient availability of skilled labour and demand for industrial products is also less.
  • Again, as the region is economically undeveloped, heavy industries cannot be established, due to a lack of sufficient capital and developed technology.
  • Due to all these reasons, heavy industries do not develop in hilly regions.

Question 18.  Why are fossils found in fold mountains?
Answer:

Fossils found in Fold Mountains:

Fossils are usually formed in sedimentary rock, almost all of which were originally deposited as sediments in the depths of the sea.

  • These rocks unlike igneous and metamorphic rocks are formed at low temperatures and pressure.
  • This helps in preserving buried animal and plant remains in the sediments. As the sediments are compressed into sedimentary rocks, the dead organisms decay and dissolve, leaving behind a cast of their skeleton i.e. fossil.
  • As fold mountains are formed mainly by the effects of folding on layers of sedimentary rock, fossils are mostly found in the fold mountains.

Question 19. What is a hill?
Answer:

Hill:

  • A rocky block with an elevation lower than that of a mountain and extending over a smaller area is called a hill.
  • The average height of a hill is between 600-900 metres. Hills also consist of many valleys and are comparatively less rugged.

Examples: Ajodhya Hills in Purulia, West Bengal, Susunia Hill in West Bengal, etc.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Hill

Question 20. What are folding mountains?
Answer:

Folding mountains:

The mountains formed due to the bending or folding of underlying rock beds resembling the shape of a wave on the Earth’s surface, over a large area are called fold mountains.

Example-Himalayas.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Fold mountain

Question 21. What is a volcanic mountain?
Answer:

Volcanic mountain:

  • When the hot and molten magma, ash, cinder or other rock fragments cannot flow away readily on reaching the Earth’s surface due to its high viscosity.
  • It accumulates around the vent forming a steep-sided conical mound called a volcanic mountain.

Example: Mt. Vesuvius.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Volcanic mountain

Question 22. What is Asthenosphere?
Answer:

Asthenosphere:

  • The word ‘Asthenosphere’ has been derived from the Greek words ‘asthenes’ So ‘asthenosphere’ means weak region. It is the meaning ‘weak’ and ‘sphere’ means ‘region’. highly viscous, mechanically weak, flexible and Earth.
  • It lies below the Lithosphere at depths deforming region of the upper mantle of between 100 km to 200 km below the Earth’s surface.

 

]WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains cross section of the earths interior showing the Asthenosphere

WBBSE Chapter 4 Landforms Topic A Mountain Short Question And Answers

Question 1. What is meant by landform?
Answer:

Landform:

Landform refers to the natural physical features on the Earth’s surface that can be categorised by characteristic physical attributes such as elevation, slope, orientation, stratification, surface area, ruggedness etc.

According to these attributes, landforms are broadly classified into three major types

  1. Mountains and hills
  2. Plateaus and
  3. Plains.

Question 2. Define endogenic forces.
Answer:

Endogenic forces:

The forces which originate and act beneath the Earth’s surface or in the interior of the Earth are called endogenic forces.

Example: Tectonic movement, continents, oceans, plateaus, and mountains are created by these forces.

Question 3. Define exogenic forces.
Answer:

Exogenic forces:

  • The forces which originate above and on the Earth’s surface and create different types of landforms by acting on or above it are called exogenic forces.
  • Examples: Rivers, wind, glaciers, sea waves, etc.

Question 4. What is a tectonic plate?
Answer:

Tectonic plate:

  • The Earth’s crust, which is the rigid outermost shell of our planet, is broken up into several slabs called crustal or tectonic plates.
  • These slabs are in constant motion i.e. floating over the molten asthenosphere.
  • These slabs are called plates. Average thickness of these plates is 100 km. The Earth’s lithosphere consists of 7 major and 20 minor plates.

Important Definitions Related to Mountains

Question 5. What are mountains?
Answer:

Mountains:

  • Extensive and unequal rock blocks with an elevation of more than 900 metres above sea level are called mountains.
  • Mountains are sometimes associated with deep gorges, steep slopes, very high peaks etc.

Examples: the Himalayas in Asia, the Alps in Europe, the Rockies in North America, etc.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Mountain

Question 6. What are mountain peaks?
Answer:

Mountain peaks:

The topmost part of a mountain shaped like a needle is called the mountain peak.

Example: Mt. Everest and Kanchenjunga are two important mountain peaks located in the Himalayas.

Question 7. What is a mountain valley?
Answer:

Mountain Valley:

The lowland or depression between two mountains is called a mountain valley. Example: Dun Valley and the Vale of Kashmir in the Himalayas.

Question 8. What is a mountain range?
Answer:

Mountain range:

A series of mountains, or parallel lines of mountains, closely connected by highland over a large region, is called a mountain range.

Example:

The Himalayas in Asia consists of three parallel mountain ranges. Some other well-known mountain ranges are the Alps in Europe and the Rockies in North America.

WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains mountain ranga

Question 9. What is a knot?
Answer:

Knot:

A high elevated place on the Earth’s surface, where several mountain ranges meet or from where several mountain ranges radiate in different directions is called a knot.

Example: Pamir Knot, Armenian Knot.

Question 10. Why aren’t all places on the Earth’s surface similar?
Answer:

On the Earth’s surface, we find different landforms, like mountains, plateaus and plains. These landforms can also change due to erosional and depositional processes. All these landforms form by two main forces-

  1. Exogenetic forces and
  2. Endogenetic forces.

These forces are the reason for the continuous change of the Earth’s crust. That is why, all places on the Earth’s surface are not similar.

Question 11. What are the characteristics of a hill?
Answer:

The characteristics of a hill are as follows-

  1. Height: The average height of a hill is 600- 900 metres above sea level. Generally, hills are the smaller form of mountains.
  2. Peak: Hills usually have peaks which are not as high as that of mountains. They may be sharp or flat or rounded in shape.
  3. Other features: Hills consist of valleys. The surface of hills are moderately rugged in nature.

Conceptual Questions on Human Activities in Mountain Regions

Question 12. How are mountains classified?
Answer:

According to the origin, mountains on the Earth’s surface can be classified into three types. They are-

  1. Fold mountains: Examples of fold mountains are the Himalayas in Asia, the Andes in South America, etc.
  2. Block mountains: Examples of block mountains are Satpura Range in Central India, the Black Forest in Germany, etc.
  3. Volcanic or Depositional mountains: Examples of volcanic mountains are- Barren and Narcondam in India, Mt. Fujiyama in Japan, etc.

Other than these, all three types of mountains get eroded due to exogenic processes (river, wind, glacier etc.) and form erosional mountains. Prolonged erosion results in residual mountains, such as the Aravalli Range in India.

WBBSE Chapter 4 Landforms Topic A Mountain Very Short Question And Answers

Question 1. What do we call a rocky landform that is spread across a wide area with an average height of 900 metres above sea level?
Answer: Mountain.

Question 2. What is the collective name for the external forces that work on and shape the Earth’s surface?
Answer: Exogenic forces.

Question 3. What is the collective name given to the forces that originate within the Earth’s interior and cause horizontal and vertical movements?
Answer: Endogenic forces.

Question 4. What is the name of a rigid layer of Earth’s crust that is believed to be drifting slowly?
Answer: Plate.

Question 5. What is the molten upper mantle known as?
Answer: Asthenosphere.

Question 6. What kind of mountains are formed due to the folding of the upper part of the crust?
Answer: Fold mountains.

Question 7. What kind of mountains are formed due to the crumpling of the underlying rock structure?
Answer: Fold mountains.

Question 8. Name a fold mountain of South America.
Answer: Andes.

Question 9. What kind of mountains are formed due to the uplifting of the land surface lying between two faults?
Answer: Block mountains.

Question 10. What kind of mountains are formed due to the deposition of lava and magma?
Answer: Volcanic mountains.

Question 11. What do we call the topmost part of a as? volcanic mountain through which magma comes out?
Answer: Crater.

Question 12. Name a famous volcanic mountain in Japan.
Answer: Mt. Fujiyama.

Question 13. Which types of mountains, belonging to the pre-drift era, are subjected to denudation and uplift?
Answer: Relict mountains.

Question 14. What are smaller mountains known as?
Answer: Hills.

Question 15. What is the topmost part of a mountain, resembling the shape of a needle known as?
Answer: Mountain peak.

Question 16. What is a chain of mountains known as?
Answer: Mountain range.

Question 17. Which mountain range was formed due to the collision of Indo-Australian and Eurasian plates?
Answer: The Himalayas.

Question 18. What kind of landform forms between two mountains through which a river flows?
Answer: Valley.

Question 19. What do we call the junction of numerous mountain ranges?
Answer: Mountain knot.

WBBSE Chapter 4 Landforms Topic A Mountain Fill In The Blanks

Question 1. The formation of mountains is known as _______ movement.
Answer: Orogenic

Question 2. The longest mountain range in the world is the _______.
Answer: Andes

Question 3. The largest mountain range not only in Asia, but also in the world is the _______.
Answer: Himalayas

Question 4. The oldest mountain range of India is the _______.
Answer: Aravallis

Question 5. Fossils are found in _______ mountains.
Answer: Fold

Question 6. Block mountains are formed as a result of _______ movement.
Answer: Tectonic

Question 7. _______ is a block mountain situated in India.
Answer: Satpura

Question 8. Mountains formed out of lava deposits are called _______ mountains.
Answer: Volcanic

Question 9. _______ is a dormant volcano in the Andaman group of islands in India.
Answer: Narcondam Island

Question 10. The opening or mouth of a volcano through which lava comes out is called _______.
Answer: Crater

Question 11. _______ is an extinct volcano situated in Myanmar.
Answer: Mt. Popa

Question 12. The highest active volcano in the world is _______.
Answer: Ojos del Salado

Question 13. The Pacific Ring of Fire has been formed along a _______ plate boundary.
Answer: Convergent

Question 14. _______ is known as the ‘Lighthouse of the Mediterranean Sea’.
Answer: Mt. Stromboli

Question 15. The other name of relict mountain is _______ mountain.
Answer: Residual

WBBSE Chapter 4 Landforms Topic A Mountain True Or False

Question 1. Block mountains are referred to as ‘horsts’ in German.
Answer: True

Question 2. Generally, rift valleys are associated with fold mountains.
Answer: False

Question 3. The size and extension of a hill is much more than a mountain.
Answer: False

Question 4. Volcanic mountains are also called relict mountains.
Answer: False

Question 5. Narmada and Tapti river valleys are examples of rift valleys located in India.
Answer: True

Question 6. Generally, the height of a mountain is more than 900 metres above sea level.
Answer: True

Question 7. The Black Forest in Germany is a volcanic mountain.
Answer: False

Question 8. The Appalachians of the USA are fold mountains.
Answer: True

Question 9. Fossils are found in fold mountains.
Answer: True

Question 10. Horsts or block mountains are formed due to the rise of the intermediate landmass between two parallel faults.
Answer: True

Question 11. The transport system is quite developed in mountainous regions.
Answer: False

WBBSE Chapter 4 Landforms Topic A Mountain Match The Columns

Question 1.WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Match the columns

Answer: 1. B, 2. A, 3. D, 4. C

Question 2.WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Match the columns.

Answer: 1. B, 2. A, 3. D, 4. C

Question 3.WBBSE Solutions For Class 7 Geography Chapter 4 Landforms Topic A Mountains Match the columns..

Answer: 1. C, 2. D, 3. A, 4. B

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