Get notes, summary, questions and answers, MCQs, extras, and PDFs of Chapter 5 “Landforms of the Earth” which is part of ICSE Class 9 Geography (Morning Star/Total) textbook/workbook answers. However, the notes should only be treated as references and changes should be made according to the needs of the students.
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Summary
The Earth’s surface displays many natural features known as landforms. The planet’s hot interior melts rocks, maintaining a semi-molten layer called the asthenosphere beneath the crust. This internal heat drives conditions that create landforms.
Several causes contribute to landform development. Plate Tectonics is a primary cause. The Earth’s lithosphere, its hard outer layer, is fractured into plates. These plates float on the asthenosphere, moving slowly. Their interactions—pushing, colliding, or sliding—can compress sedimentary rocks, causing them to fold and form fold mountains. The forces behind this are Orogenic movements, a term derived from Greek words meaning “mountain-building.”
Other internal forces, Epeirogenic movements, lead to widespread uplift or subsidence of land. “Epeiros” signifies “continent” and “genic” means “building,” thus these are continent-building movements. They produce block mountains, basins, and rift valleys. Orogenic and epeirogenic forces together are termed Diastrophic forces. In contrast, Exogenic Forces operate on the Earth’s surface. They are often called destructive forces as they wear down existing landforms through weathering and erosion, then create new ones via deposition.
Major landforms include mountains, plateaus, and plains.
Mountains are steep, elevated landforms. Fold Mountains arise from the crust’s compression, exhibiting wave-like upfolds (anticlines) and downfolds (synclines). The Himalayas and Alps are examples. Young Fold Mountains, like the Himalayas, are high and rugged. Old Fold Mountains, such as the Aravallis in India, are lower due to prolonged erosion.
Residual Mountains, also called relict mountains, remain after extensive weathering and erosion have lowered older mountains or plateaus. The Nilgiri Hills are an Indian example.
Block Mountains form due to tensional forces creating faults. A block of land might rise to become a horst (block mountain), or sink to form a graben (rift valley). The Vosges in France is an example.
Plateaus are elevated, flat-topped areas, often called tablelands, typically 500 feet or more above the surrounding land. Intermontane Plateaus, like the Tibetan Plateau, are enclosed by mountains. Volcanic Plateaus, such as India’s Deccan Plateau, are built from successive layers of lava from volcanic eruptions.
Plains are vast, low-lying areas with level or gently undulating surfaces. Structural Plains result from the uplift or subsidence of land, like the Great Plains of the USA. Depositional Plains are formed by the accumulation of materials transported by rivers, wind, or the sea. River deposition creates alluvial plains, such as the Northern Plains of India. Wind action forms sandy deserts like the Sahara or loess plains. Marine deposition creates coastal plains, and sometimes land reclaimed from the sea, called a polder.
Landforms hold significant importance. They contribute to the Earth’s scenic beauty. They influence climate; for instance, the Himalayas shape India’s climate. Mountains often serve as the source for rivers. They host diverse forests, plants, and animals. Oceanic landforms can be ideal fishing grounds. The geological processes forming landforms also bring valuable minerals and fossil fuels nearer to the Earth’s surface.
Textbook solutions (Morning Star/Total)
Multiple-Choice Questions
1. The forces responsible for the formation of fold mountains:
(a) Orogenic movements
(b) Collisional movements
(c) Diastrophic movements
(d) Exogenic movements
Answer: (a) Orogenic movements
2. The large scale uplift or subsistence of land:
(a) Orogenic movements
(b) Diastrophic forces
(c) Epeirogenic movements
(d) Exogenic movements
Answer: (c) Epeirogenic movements
3. The two forces, Orogenic and Epeirogenic that originate deep inside the earth:
(a) Exogenic forces
(b) Continent building movements
(c) Diastrophic forces
(d) Collisional movements
Answer: (c) Diastrophic forces
4. The forces operating on the surface of the earth which cause formation of landforms are called:
(a) Exogenic forces (b) Orogenic forces
(c) Diastrophic forces (d) Epeirogenic forces
Answer: (a) Exogenic forces
5. Upfold : Anticline :: Downfold : ___________
(a) Synclines
(b) Archlines
(c) Anticlines
(d) Ridges
Answer: (a) Synclines
6. Oceanic trenches in combination with volcanic mountain systems lead to the formation of:
(a) Troughs
(b) Ridges
(c) Fold mountains
(d) Synclines
Answer: (b) Ridges
7. Volcanic activities are common in which of the following?
(a) Young fold mountains
(b) Old fold mountains
(c) Residual mountains
(d) Volcanic plateaus
Answer: (a) Young fold mountains
8. Which amongst the following highlands are highly eroded by the agents of gradation and have gentler slopes, rounded tops and sculptured domes?
(a) Young fold mountains
(b) Old fold mountains
(c) Residual mountains
(d) Volcanic plateaus
Answer: (b) Old fold mountains
9. Mountains which are subjected to weathering and erosion for a long time are lowered down:
(a) Old fold mountains
(b) Volcanic plateaus
(c) Relict mountains
(d) Intermontane plateaus
Answer: (c) Relict mountains
10. Which of the following is/are correctly matched?
(a) Young fold mountains : Himalayas, Alps
(b) Old fold mountains : Urals, Aravalli
(c) Residual mountains : Nilgiri, Rajmahal Hills
(d) All of the above.
Answer: (d) All of the above.
11. The coromandel plains along the east coast of India were formed as a result of two different activities. Name them.
(a) Subsidence, deposition
(b) Subsidence, erosion
(c) Upliftment, deposition
(d) Upliftment, erosion
Answer: (a) Subsidence, deposition
12. The plains that are formed by the deposition of materials which have been brought by various agents of transportation:
(a) Structural plain (b) Depositional plain (c) Plain
(d) Landform
Answer: (b) Depositional plain
13. Depositional plains formed as a result of action of wind have irregular and undulating surface because of
(a) new deposits made every day.
(b) existence of sand dunes and hallows.
(c) existence of scrubs.
(d) All of the above.
Answer: (b) existence of sand dunes and hallows.
14. A piece of land reclaimed from the sea or lake:
(a) Sealand
(b) Iceland
(c) Lakeland
(d) Polder
Answer: (d) Polder
15. The plains that are formed due to uplift or subsidence of land are called:
(a) Structural plains
(b) Depositional plains
(c) Plains
(d) Landforms
Answer: (a) Structural plains
16. Which of the following pairs is incorrectly matched?
(a) Structural Plains : Coromandel Plains
(b) Wind Deposition Plains : Thar Desert
(c) River Deposition Plains : Northern Plains (India)
(d) Marine Deposition Plains : Western Coastal Plains (India)
Answer: (d) Marine Deposition Plains : Western Coastal Plains (India)
17. Epeirogenic forces lead to the formation of Block Mountains. In this context which of the following are true?
(a) Horst – block mountains with flattened summits.
(b) Graben – basins separating block mountains.
(c) Vosges example of block mountains.
(d) All of the above.
Answer: (d) All of the above.
18. Name the plateaus, formed along with fold mountains, that are surrounded by hills and mountains on all sides.
(a) Volcanic Plateaus
(b) Structural Plateaus
(c) Intermontane Plateaus
(d) Depositional Plateaus
Answer: (c) Intermontane Plateaus
Short Answer Questions
1. What is meant by a landform? Give two examples.
Answer: A landform is a natural feature of the earth’s surface. Two examples of landforms are mountains and plateaus.
2. Why are the fold mountains called so?
Answer: Fold mountains are called so because they are the result of large-scale earth movements caused by stresses in the earth’s crust. These stresses subject the rocks to compressive forces, producing wrinkling or folding along the lines of weakness. The raising of these folds makes the fold mountains, which form irregular wave-like formations called folds.
3. Give two chief characteristics of the fold mountains.
Answer: Two chief characteristics of fold mountains are:
(i) They form irregular wave-like formations called folds. The upfold rock strata in arch-like shape are called anticlines or crest and the down folded structures are known as synclines or troughs.
(ii) Most of these mountains are constituted of sedimentary rocks formed due to deposition and consolidation of sediments in shallow oceans like the Tethys, in the case of the Himalayas.
4. Give one example of each: (a) Young fold mountain; (b) Old fold mountain.
Answer: (a) An example of a young fold mountain is the Himalayas.
(b) An example of an old fold mountain is the Appalachians.
5. Give one example of residual mountain and an example of depositional plain.
Answer: An example of a residual mountain is Nilgiri Hills in India. An example of a depositional plain is the Northern Plains of India, which are alluvial plains.
6. Briefly describe how the Great Plains of USA were formed. They are examples of which type of Plains.
Answer: The Great Plains of the USA were formed due to the uplift of land submerged under water. They are examples of Structural Plains.
7. Draw a well labelled diagram to show the formation of a residual mountain.
Answer: For diagram, see Fig. 5.3 (Morning Star/Total) or click here.
8. How is a rift valley formed? Give one example of a rift valley.
Answer: A rift valley is formed when, due to tensional force, cracks or faults occur on the earth’s crust. If two parallel faults occur, the land in between subsides, or the valley floor may sink, to form a rift valley. An example of a rift valley is the African Rift Valley.
9. Give a brief definition of a plateau.
Answer: A plateau is defined as an area of high ground, 500 feet above the ground level. These uplands have a steep slope on one side. The upper part is generally flat and is called tableland.
10. What is an intermontane plateau? Give one example.
Answer: An intermontane plateau is a plateau surrounded by hills and mountains on all sides. An example of an intermontane plateau is the Tibetan plateau.
11. Give two points of importance of landforms.
Answer: Two points of importance of landforms are:
(i) Mountains, plateaus, plains and valleys are beautiful sculptures of nature on the surface crust of the earth. They add to the beauty of the earth.
(ii) Landforms represent the relief features of the earth. They have an impact on climate, direction of winds, precipitation as well as other atmospheric processes. The Himalayas act as a climatic divide shaping the distinctive climate of the Indian subcontinent.
Distinguish Between the Following
1. Distinguish between Fold Mountains and Block Mountains.
Answer: Fold Mountains are the result of lateral compression of the earth’s crust. They are the result of large-scale earth movements caused by stresses in the earth’s crust. These stresses subject the rocks to compressive forces, producing wrinkling or folding along the lines of weakness, and the raising of folds makes the fold mountains.
Block Mountains, on the other hand, are formed when forces of faulting, also known as epeirogenic forces, lead to their formation. Due to tensional force, cracks or faults may occur on the earth’s crust. If two parallel faults occur, the land in between subsides to form a rift valley. If a block rises, it forms a horst or block mountain. Block mountains which have flattened summits are also called horst mountains.
2. Distinguish between Intermontane plateaus and Volcanic plateaus.
Answer: Intermontane Plateaus are the highest and most extensive types of plateaus on the globe. These plateaus are surrounded by hills and mountains on all sides and are formed along with fold mountains.
Volcanic Plateaus are formed by numerous volcanic eruptions that slowly build up over time, forming a plateau.
3. Distinguish between Structural plains and Depositional plains.
Answer: Structural Plains are plains that are formed due to uplift or subsidence of land. Diastrophic forces may cause uplift of a portion of land beneath the ocean water or may cause submergence of coastal land under ocean water.
Depositional Plains are plains that are formed by the deposition of materials which have been brought by various agents of transportation.
Structured Questions
1. (a) How are various landforms formed on the surface of the earth?
Answer: Various landforms are formed on the surface of the earth due to several conditions which are caused by the internal heat of the earth. This internal heat melts the rocks and keeps the asthenosphere, which is underneath the crust, in a semi-molten state. The causes of landform development include:
- Plate Tectonics: The lithosphere is broken into several small and big plates that float on the semi-molten asthenosphere. The horizontal movement of these plates, though very slow, causes them to push, collide, or slide past each other. This results in disturbances in sedimentary rock deposits, causing compression and folding of the rocks. The forces responsible for this, called Orogenic movements, act at a tangent to the surface of the earth and are primarily involved in plate tectonics.
- Uplift and Submergence: Another set of forces operating inside the earth act along the radius from the earth’s centre to the surface. These are characterised by large-scale uplift or subsidence of land area and are known as Epeirogenic movements or Continent building movements. Such movements are the result of faulting or cracks in the earth’s surface.
These two forces, orogenic and epeirogenic, are together called Diastrophic Forces, originating deep inside the earth. They act horizontally and vertically and produce relief such as mountains, plateaus, plains, lakes, and big faults. - Exogenic Forces: These are forces operating on the surface of the earth, not inside it, which cause the formation of landforms. Exogenic forces are described as Destructive Forces because they cause widespread destruction through weathering and erosion of existing landforms. They then form new landforms through both erosion and deposition.
1. (b) Describe the formation of mountains and their types.
Answer: Mountains are formed through various geological processes. The three main types of mountains, classified depending on the forces that have formed them, are Fold Mountains, Residual Mountains, and Block Mountains.
Their formation is as follows:
- Fold Mountains: These are the result of lateral compression of the earth’s crust. Fold mountains are formed by large-scale earth movements caused by stresses in the earth’s crust. Such stresses may be caused by the weight of overlying rocks, movements in the mantle, or the expansion or contraction of some part of the earth. These stresses subject the rocks to compressive forces, producing wrinkling or folding along lines of weakness. The raising of these folds makes the fold mountains.
- Residual Mountains: These mountains, also called relict mountains, are formed when existing mountains are subjected to weathering and erosion for a long time and are lowered down. Denudation and erosion by natural agents such as winds, water, snow, etc., cause the mountains to be lowered, but some resistant areas may remain and form residual mountains. They may also be formed on plateaus that are dissected by rivers.
- Block Mountains: The forces of faulting, also known as epeirogenic forces, lead to the formation of block mountains. Due to tensional force, cracks or faults may occur on the earth’s crust. If two parallel faults occur, the land in between subsides to form a rift valley. If a block rises, it forms a horst or block mountain.
1. (c) Give a reason for each of the following:
(i) Asthenosphere though underneath the crust is in a semi-molten state.
Answer: The asthenosphere, though underneath the crust, is in a semi-molten state because the intense heat in the earth’s interior does not travel to the surface as rocks are bad conductors of heat. The internal heat of the earth, therefore, melts the rocks and keeps the asthenosphere in this semi-molten state.
(ii) Exogenic forces are also called destructive forces.
Answer: Exogenic forces are also called destructive forces because they cause widespread destruction through weathering and erosion of existing landforms.
(iii) Residual mountains are also called mountains of denudation.
Answer: Residual mountains are also called mountains of denudation because they are formed when mountains are subjected to weathering and erosion (denudation) for a long time and are lowered down by these processes, or when an original highland (plateau) is worn down by the down cutting action of rivers.
1. (d) Draw a well labelled diagram to show the formation of block mountain.
Answer: For diagram, see Fig. 5.5 (Morning Star/Total) or click here
2. (a) Describe the characteristics of two different types of plateaus.
Answer: Two different types of plateaus are Intermontane Plateaus and Volcanic Plateaus.
- Intermontane Plateaus: These are the highest and most extensive types of plateaus on the globe. Their chief characteristic is that they are surrounded by hills and mountains on all sides. They are formed along with fold mountains. The Tibetan plateau is the world’s highest as well as most extensive intermontane plateau. Other examples include the Columbian Plateau, North American Cordillera, Bolivian, Peruvian, and Mexican plateaus.
- Volcanic Plateaus: These plateaus are formed by numerous volcanic eruptions that slowly build up over time, forming a plateau. The Plateau of Peninsular India, especially the north western Deccan, is an example of a lava plateau and has an enormous accumulation of basaltic rock. The Columbian Plateau, another example, has about 20 layers of lava, suggesting that 20 different volcanic eruptions have formed this plateau. Other examples include the South African plateau and Ethiopian plateau.
2. (b) Describe the characteristics of structural plains.
Answer: Structural plains are plains that are formed due to the uplift or subsidence of land. Their characteristics arise from these diastrophic forces. For instance, these forces may cause the uplift of a portion of land beneath the ocean water, as seen in the formation of the Great Plains of the USA which were formed due to the uplift of land submerged under water; the fact that they were submerged under water is responsible for the existence of many lakes in this vast lowland. The Gulf Coast is another example of an emerged coastal plain.
Conversely, structural plains can result from the submergence of coastal land under ocean water or mild subsidence followed by sedimentation, as in the case of the Coromandel plains in India. Thus, the forces of structural development, sometimes coupled with deposition, are active in the formation of these plains.
2. (c) Give a reason for each of the following:
(i) There are different types of plains.
Answer: There are different types of plains because there are seemingly endless variations in plains, and they are an imprint of past and present processes. A plain is seldom formed by a single process, which leads to the distinction of types such as Structural Plains, Erosional Plains, and Depositional Plains.
(ii) Alluvial plains are regarded as the granaries of the world.
Answer: Alluvial plains, particularly flood plains found along rivers like Ganga, Yang-tze, Mekong, Salveen etc., are regarded as granaries of the world. While the text does not explicitly state why beyond their location, their formation by river deposition implies fertility.
(iii) The landforms on the surface of the earth are symbols of the energy of the earth.
Answer: The landforms on the surface of the earth are symbols of the energy of the earth because they are basically a result of enormous heat generated inside the earth and climate factors operating on the surface of the earth. The earth releases its energy through tectonic activity, earthquakes, and volcanoes, and these internal forces, along with surface weathering and erosional forces, are dominant in sculpturing land.
2. (d) Explain the chief characteristics of depositional plains and their types.
Answer: The chief characteristic of depositional plains is that they are formed by the deposition of materials which have been brought by various agents of transportation.
Their types are:
- (i) River Deposition Plains: These are the most widespread type, including alluvial plains like the Northern Plains of India, flood plains like the Mississippi Plains in the USA, and deltaic plains in Egypt and India. Piedmont Alluvial Plains are formed at the foothills of mountains. Flood plains along rivers like Ganga, Yang-tze, Mekong, and Salveen are also alluvial plains and are regarded as granaries of the world. In India, flood plains are divided into Khadar Plains (new deposits made every year) and Bhangar (old deposits not renewed every year).
- (ii) Wind Deposition Plains: Most such plains are sandy deserts like the Sahara in Africa and the Thar desert in India. They have an irregular and undulating surface made by the existence of sand dunes and hallows. Loess plains in China are formed from deserts.
- (iii) Marine Deposition Plains: These plains are found in coastal regions. Examples include the east coast of India, the estuarine banks in the Netherlands, and the coasts of Germany and Denmark. In Denmark, polders and dykes are found; a polder is a piece of land reclaimed from the sea or lake, where the submerged land is surrounded by an embankment (dyke) and drained by pumping water into canals.
Thinking Skills
1. Find out the landforms found in your state. How were these landforms formed? How many changes have come in these landforms over the years.
Answer: In my region, which is part of Peninsular India, we see a fascinating mix of landforms. A significant portion is characterized by plateaus, specifically the kind formed from volcanic activity. These vast, elevated flatlands, often called tablelands, were built up slowly over immense periods by numerous volcanic eruptions, with lava spreading out and solidifying layer upon layer. The north-western Deccan is a prime example of such a lava plateau, with its enormous accumulation of basaltic rock. Some parts of the Columbian Plateau, for instance, have about 20 layers of lava, suggesting 20 different volcanic eruptions formed it, and our plateaus here share a similar origin story.
We also have many residual mountains or hills. These are not formed by uplift like fold mountains, but are the remnants of older, larger landmasses, possibly ancient mountains or extensive plateaus, that have been worn down over a very long time by weathering and erosion. Natural agents like wind and water have gradually lowered these landmasses. The more resistant rock portions, however, withstood this denudation better and now stand out as hills or low mountains. You can see this in areas where plateaus have been deeply dissected by rivers, carving out hills and valleys – the Deccan plateau itself has many such features. The Nilgiri and Rajmahal Hills are well-known examples of such residual mountains in India.
Over the years, these landforms have, of course, continued to change. The residual mountains, by their very nature, are a testament to long-term erosion. They have been significantly lowered from their original heights and are often characterized by gentler slopes and more rounded tops compared to younger, more rugged mountains, though the exact relief depends on the degree of recent erosion. The plateaus too are constantly being acted upon by rivers, which carve valleys and gradually wear down the surface, contributing to the formation of those dissected hills I mentioned. So, the process of denudation is an ongoing one, continually reshaping these ancient landscapes.
2. The earth releases its energy through tectonic activity, earthquakes and volcanoes. Imagine what will be the consequences if this energy remains trapped inside the earth. State these consequences with examples.
Answer: The earth’s internal heat is immense, and it’s this heat that melts rocks in the interior and keeps the asthenosphere (the layer beneath the crust) in a semi-molten state. This semi-molten asthenosphere is what the lithospheric plates float on, and their movement, driven by this internal energy, leads to tectonic activity like the collision or pulling apart of plates. These activities, along with earthquakes and volcanoes, are how the earth releases its internal energy, and they are the primary forces that build major landforms like fold mountains.
Now, if this energy were to remain trapped inside the earth, and couldn’t be released through these usual processes, the consequences would likely be profound. The intense heat that normally keeps the asthenosphere semi-molten might build up even further. This could lead to more extensive melting of rocks in the mantle. The pressure from this superheated, increasingly molten material would also likely increase significantly.
Since tectonic activity, earthquakes, and volcanoes are the earth’s way of letting off this steam, if these vents were somehow completely blocked and the energy remained trapped indefinitely, the internal conditions would become more extreme. While the rocks are bad conductors of heat, which is why the interior is so hot in the first place, a complete inability to release this accumulating energy would likely mean that the very processes that shape our planet’s surface would be altered. Perhaps the asthenosphere would become even more fluid, or the pressure would build to a point where any eventual release would be far more intense than what we typically observe. The forces that cause landform development, which are driven by this internal heat, might become overwhelmingly powerful if suppressed for too long.
Practical Work
1. Draw and colour different relief features on the surface of the earth.
Answer: Do it yourself. Here are the instructions:
- Take an A4 or chart paper for the drawing.
- Use a pencil first to sketch the different landforms:
- Mountains: Show fold mountains (like the Himalayas) with tall, pointed shapes.
- Plateaus: Draw flat-topped elevated areas like a table.
- Plains: Show large, flat lowland areas.
- Rift valleys: Draw deep valleys with steep sides between highlands.
- Volcanic mountains: Show a conical mountain with a crater on top.
- Label each feature clearly.
- Colour each feature with appropriate shades:
- Brown for mountains and plateaus
- Green for plains
- Grey for rift valleys
- Dark brown or red for volcanic mountains
- Add a key or legend to show what each colour and shape represents.
2. On an outline map of the world show major fold mountains, plateaus and plains with the help of symbols.
Answer: Do it yourself. Here are the instructions:
- Use a printed or drawn outline world map.
- Draw and mark the following with simple symbols: Fold Mountains (use triangle ▲ symbol):
- Himalayas (Asia)
- Andes (South America)
- Rockies (North America)
- Alps (Europe)
- Tibetan Plateau (Asia)
- Deccan Plateau (India)
- Columbian Plateau (USA)
- Ethiopian Plateau (Africa)
- Indo-Gangetic Plain (India)
- Great Plains (USA)
- North China Plain (China)
- Use colour pencils:
- Brown for mountains
- Yellow or orange for plateaus
- Green for plains
- Add a map key explaining each symbol.
- Ensure all names are neatly written and not overlapping the features.
Extras
Additional MCQs
1. A natural feature of the earth’s surface is known as what?
A. Landform
B. Topography
C. Relief
D. Contour
Answer: A. Landform
58. Northern Plains of India are examples of which type of plains?
A. Alluvial plains
B. Desert plains
C. Marine plains
D. Structural plains
Answer: A. Alluvial plains
Additional Assertion and Reason
1. Assertion (A): The asthenosphere, a layer beneath the Earth’s crust, exists in a semi-molten state.
Reason (R): Intense heat from the Earth’s interior is insufficient to melt rocks because rocks are good conductors of heat.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (c) A is true but R is false.
30. Assertion (A): The Great Plains of the USA, which are a type of structural plain, were formed due to the geological uplift of land that was previously submerged under water.
Reason (R): Structural plains are exclusively created by the deposition of materials transported and laid down by agents such as rivers and wind.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (c) A is true but R is false.
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