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Structure and Physiography of India

NCERT Class 11 · Geography Based on NCERT Class 11 Geography textbook · Free CBSE study kit

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Chapter Notes

Overview
This chapter explains the geological structure and physiographic divisions of India, tracing the evolution of the Indian landmass from the movement of the Indian plate to the present-day relief features. It divides India into three geological divisions—the Peninsular Block, the Himalayas and other Peninsular Mountains, and the Indo-Ganga-Brahmaputra Plain—and then into six physiographic divisions. The one big idea a student must walk away with is that India's diverse physical landscape is the result of millions of years of tectonic plate movements, endogenic and exogenic forces, and the interplay of structure, process, and stage of development.
Key Concepts (20)
Endogenic forces
Forces originating from within the earth that cause vertical and horizontal movements, leading to the formation of landforms such as mountains, rift valleys, and faults.
e.g. The northward movement of the Indian plate causing the uplift of the Himalayas.
Exogenic forces
Forces originating from outside the earth that wear down the surface through processes like weathering, erosion, and deposition.
e.g. The formation of alluvial plains by the deposition of sediments brought by rivers like the Ganga.
Peninsular Block
The ancient, rigid, and stable landmass of India composed mainly of gneisses and granites, forming the southern part of the country.
e.g. The Deccan Plateau is a part of the Peninsular Block.
Indo-Ganga-Brahmaputra Plain
The vast alluvial plain formed by the sediments deposited by the Indus, Ganga, and Brahmaputra rivers, originally a geo-synclinal depression.
e.g. The fertile plains of Punjab, Haryana, and Uttar Pradesh are part of this plain.
Bhabar
A narrow belt (8-10 km wide) parallel to the Shiwalik foothills where streams deposit heavy materials like rocks and boulders, often disappearing underground.
e.g. The Bhabar belt is found along the foothills of the Himalayas in Uttarakhand.
Tarai
A marshy and swampy belt (10-20 km wide) south of the Bhabar where streams re-emerge, creating conditions for lush vegetation and wildlife.
e.g. The Tarai region in Uttar Pradesh is known for its dense forests and wildlife sanctuaries.
Bhangar
The older alluvial deposits found in the northern plains, forming high terraces above flood levels, often containing calcareous concretions called kankar.
e.g. The Bhangar soil is found in the uplands of the Ganga plain.
Khadar
The newer alluvial deposits found in floodplains, renewed annually by river floods, and very fertile.
e.g. The Khadar soil is ideal for growing sugarcane and rice in the Ganga delta.
Western Ghats
A continuous mountain range along the western coast of India, with an average elevation of about 1,500 m, locally known as Sahyadri, Nilgiri, Anaimalai, and Cardamom hills.
e.g. Anaimudi (2,695 m), the highest peak of the Peninsular plateau, is located in the Anaimalai hills of the Western Ghats.
Eastern Ghats
A discontinuous and low mountain range along the eastern coast of India, highly eroded by rivers like the Mahanadi, Godavari, Krishna, and Kaveri.
e.g. The Nallamala hills and Javadi hills are part of the Eastern Ghats.
Kayals
Backwaters found along the Malabar coast in Kerala, used for fishing, inland navigation, and tourism.
e.g. Punnamada Kayal in Kerala hosts the famous Nehru Trophy Vallamkali (boat race).
Barchans
Crescent-shaped sand dunes formed by wind action in desert regions.
e.g. Barchans are commonly found in the Great Indian Desert (Marusthali).
Ten degree channel
The water body that separates the Andaman Islands in the north from the Nicobar Islands in the south.
e.g. The Ten degree channel is located approximately at 10°N latitude.
Nine degree channel
The water body that divides the Lakshadweep islands, with the Amini Island to the north and the Canannore Island to the south.
e.g. The Nine degree channel is used for navigation between the northern and southern Lakshadweep islands.
Marusthali
The Great Indian Desert, characterized by undulating topography, longitudinal dunes, barchans, and arid climate with rainfall below 150 mm per year.
e.g. The Marusthali region in Rajasthan has mushroom rocks and shifting dunes.
Relict mountains
Old, highly denuded mountains that have been reduced to low hills by prolonged erosion.
e.g. The Aravali range and the Satpura range are examples of relict mountains.
Rift valleys
Linear valleys formed by the sinking of land between two parallel faults due to tectonic activity.
e.g. The Narmada, Tapi, and Mahanadi rivers flow through rift valleys in the Peninsular Block.
Geo-synclinal depression
A large-scale depression in the earth's crust that accumulates sediments over millions of years.
e.g. The Indo-Ganga-Brahmaputra Plain was originally a geo-synclinal depression filled by river sediments.
Submerged coastal plain
A coastal plain that has been partially submerged under the sea due to tectonic activity or sea-level rise.
e.g. The western coastal plains of India are an example of a submerged coastal plain, with natural ports like Kandla and Mumbai.
Emergent coast
A coast that has been exposed due to a fall in sea level or uplift of land, resulting in broader plains and deltas.
e.g. The eastern coastal plains of India are an example of an emergent coast, with well-developed deltas.
How It Works
Formation of the Indian landmass through plate tectonics
  1. The Indian plate was originally located south of the equator and was much larger, including the Australian plate.
  2. Over millions of years, the plate broke into parts; the Australian plate moved southeast, and the Indian plate moved northward.
  3. The northward movement of the Indian plate continues today, causing collisions with the Eurasian plate.
  4. This collision led to the uplift of the Himalayas and the formation of the Indo-Ganga-Brahmaputra depression.
  5. The Peninsular Block remained a rigid, stable landmass, while the Himalayas and the northern plains were shaped by ongoing tectonic and sedimentary processes.
💡 Students often forget that the Indian plate is still moving northward, which causes ongoing seismic activity in the Himalayas.
Formation of the Northern Plains (Bhabar, Tarai, Bhangar, Khadar)
  1. Rivers originating from the Himalayas deposit heavy materials like rocks and boulders at the break of slope, forming the Bhabar belt (8-10 km wide).
  2. South of Bhabar, streams re-emerge in a marshy zone called Tarai (10-20 km wide), with lush vegetation.
  3. Further south, older alluvial deposits form the Bhangar belt, characterized by high terraces and kankar.
  4. Newer alluvial deposits in floodplains form the Khadar belt, renewed annually by floods and very fertile.
  5. The plains extend 3,200 km east-west, with an average width of 150-300 km and alluvium depth of 1,000-2,000 m.
💡 Students often confuse Bhabar and Tarai: Bhabar is where rivers disappear; Tarai is where they re-emerge.
Formation of rift valleys in the Peninsular Block
  1. The Peninsular Block experienced vertical movements and block faulting due to tectonic activity.
  2. Faulting caused the land between two parallel faults to sink, creating rift valleys.
  3. Rivers like the Narmada, Tapi, and Mahanadi now flow through these rift valleys.
  4. The Satpura block mountains are an example of uplifted blocks adjacent to these rift valleys.
💡 Rift valleys are formed by faulting, not by river erosion—students often confuse this with river valleys.
Formation of the Andaman and Nicobar Islands
  1. The islands are believed to be elevated portions of submarine mountains.
  2. Some smaller islands are volcanic in origin, such as Barren Island, the only active volcano in India.
  3. The islands are divided into the Andaman group (north) and Nicobar group (south), separated by the Ten degree channel.
  4. Coral deposits and beautiful beaches are found along the coastline.
💡 Barren Island is the only active volcano in India—students often forget this specific fact.
Formation of the Lakshadweep Islands
  1. The Lakshadweep islands are built entirely of coral deposits.
  2. They are scattered between 8°N-12°N and 71°E-74°E, about 220-440 km off the Kerala coast.
  3. The islands are divided by the Nine degree channel, with Amini Island to the north and Canannore Island to the south.
  4. Storm beaches on the eastern seaboard consist of unconsolidated pebbles, shingles, cobbles, and boulders.
💡 Lakshadweep islands are coral islands, while Andaman and Nicobar are mostly elevated submarine mountains—this distinction is frequently tested.
Exam Traps — Don't Make These Mistakes
⚠ Confusing Bhabar and Tarai belts
✗ Bhabar is the marshy belt where streams re-emerge, and Tarai is the belt where rivers deposit boulders.
→ It is the opposite: Bhabar is the belt of coarse deposits where rivers disappear; Tarai is the marshy belt where they re-emerge.
✓ Bhabar is a narrow belt (8-10 km) parallel to the Shiwalik foothills where streams deposit heavy materials and disappear. Tarai is a wider belt (10-20 km) south of Bhabar where streams re-emerge, creating marshy conditions.
⚠ Mixing up the highest peaks of the Peninsular plateau
✗ Dodabetta is the highest peak of the Peninsular plateau.
→ Anaimudi (2,695 m) is the highest peak, located on the Anaimalai hills. Dodabetta (2,637 m) is the second highest, on the Nilgiri hills.
✓ The highest peak of the Peninsular plateau is Anaimudi (2,695 m) on the Anaimalai hills of the Western Ghats, followed by Dodabetta (2,637 m) on the Nilgiri hills.
⚠ Confusing the Ten degree and Nine degree channels
✗ The Ten degree channel separates Lakshadweep and Minicoy, and the Nine degree channel separates Andaman and Nicobar.
→ It is the reverse: the Ten degree channel separates Andaman and Nicobar islands; the Nine degree channel divides the Lakshadweep islands.
✓ The Ten degree channel separates the Andaman Islands (north) from the Nicobar Islands (south). The Nine degree channel divides the Lakshadweep islands, with Amini Island to the north and Canannore Island to the south.
⚠ Assuming all Peninsular rivers flow eastward
✗ All Peninsular rivers flow into the Bay of Bengal.
→ While most major Peninsular rivers (Mahanadi, Godavari, Krishna, Kaveri) flow east into the Bay of Bengal, some rivers like the Narmada and Tapi flow west into the Arabian Sea through rift valleys.
✓ Most Peninsular rivers flow eastward into the Bay of Bengal, forming deltas. However, the Narmada and Tapi flow westward into the Arabian Sea through rift valleys and do not form deltas.
⚠ Thinking the Indian Desert was always a desert
✗ The Great Indian Desert has always been an arid region with no marine history.
→ Evidence such as wood fossils at Aakal (180 million years old) and marine deposits near Jaisalmer show that this region was under the sea during the Mesozoic era.
✓ The Great Indian Desert (Marusthali) was under the sea during the Mesozoic era, as evidenced by wood fossils and marine deposits. Its present arid features are due to extreme climatic conditions and wind action.
Compare & Contrast
Nature of coast and geomorphological features
Western Coastal Plains
Eastern Coastal Plains
Western coastal plains are a submerged coast, narrow, with natural ports and harbours (e.g., Kandla, Mumbai), and rivers do not form deltas. Eastern coastal plains are an emergent coast, broader, with well-developed deltas (e.g., Mahanadi, Godavari, Krishna, Kaveri), and have fewer natural ports due to a wide continental shelf.
Origin and geological composition
Andaman and Nicobar Islands
Lakshadweep Islands
Andaman and Nicobar Islands are elevated portions of submarine mountains, with some volcanic islands (e.g., Barren Island), and have coral deposits. Lakshadweep Islands are entirely built of coral deposits, with storm beaches of unconsolidated material, and are located off the Kerala coast.
Age and location of alluvial deposits
Bhangar
Khadar
Bhangar is older alluvium found on higher terraces, often containing calcareous concretions (kankar), and is not renewed annually. Khadar is newer alluvium deposited in floodplains, renewed annually by floods, and is more fertile.
Exam Focus
Marks pattern: 2 MCQs (1 mark each), 1 SA (3 marks), 1 LA (5 marks) — total approximately 10 marks
Most asked: Physiographic divisions of India (six divisions) · Comparison of Western and Eastern Coastal Plains · Difference between Bhabar, Tarai, Bhangar, and Khadar · Highest peaks of the Peninsular plateau (Anaimudi, Dodabetta) · Island groups: Andaman & Nicobar vs Lakshadweep · Rift valleys of the Peninsular Block (Narmada, Tapi, Mahanadi) · Formation of the Himalayas and the Northern Plains · Ten degree and Nine degree channels
Don't skip: Describe the six physiographic divisions of India with their key features (5 marks); Compare and contrast the Western and Eastern Coastal Plains (3 marks); Explain the formation and features of the Northern Plains, including Bhabar, Tarai, Bhangar, and Khadar (5 marks); Differentiate between the Andaman & Nicobar and Lakshadweep island groups (3 marks)
One-Line Revision (read aloud before the exam)
  1. India is divided into three geological divisions: the Peninsular Block, the Himalayas and other Peninsular Mountains, and the Indo-Ganga-Brahmaputra Plain.
  2. The Peninsular Block is a rigid, stable landmass of ancient gneisses and granites, with rift valleys of the Narmada, Tapi, and Mahanadi.
  3. The Himalayas are young, weak, and flexible mountains of tectonic origin, dissected by fast-flowing rivers in their youthful stage.
  4. The Indo-Ganga-Brahmaputra Plain was originally a geo-synclinal depression filled by sediments from Himalayan and Peninsular rivers.
  5. The Northern Plains are divided into Bhabar (8-10 km, where rivers disappear), Tarai (10-20 km, marshy), Bhangar (older alluvium), and Khadar (newer alluvium).
  6. The Peninsular Plateau is divided into the Deccan Plateau, Central Highlands, and Northeastern Plateau.
  7. Anaimudi (2,695 m) is the highest peak of the Peninsular plateau, located on the Anaimalai hills of the Western Ghats.
  8. Western Ghats are higher and more continuous than the Eastern Ghats, which are discontinuous and highly eroded.
  9. The Indian Desert (Marusthali) was under the sea during the Mesozoic era, as evidenced by wood fossils at Aakal.
  10. Western coastal plains are submerged, narrow, with natural ports; eastern coastal plains are emergent, broader, with large deltas.
  11. The Ten degree channel separates the Andaman and Nicobar Islands; the Nine degree channel divides the Lakshadweep islands.
  12. Barren Island in the Andaman and Nicobar Islands is the only active volcano in India.
  13. Lakshadweep islands are built of coral deposits, while Andaman and Nicobar islands are elevated submarine mountains.
  14. Kayals (backwaters) are a distinctive feature of the Malabar coast, used for fishing, navigation, and tourism.
  15. The Luni river is the only significant river in the Indian Desert, and most desert rivers are ephemeral with inland drainage.

MCQs — 10 Questions with Answers

Q1. Which of the following rock types primarily forms the foundation of the Peninsular Block?

  • A. Sedimentary rocks and alluvium
  • B. Ancient gneisses and granites ✓
  • C. Young metamorphic rocks and basalt
  • D. Limestone and chalk deposits

Answer: B — The Peninsular Block is formed essentially by ancient gneisses and granites as stated in the text, which constitute the stable, rigid foundation.

Q2. When did the Indo-Ganga-Brahmaputra Plain attain its maximum development during Himalayan mountain formation?

  • A. Approximately 100 million years ago
  • B. Approximately 64 million years ago ✓
  • C. Approximately 25 million years ago
  • D. Approximately 10 million years ago

Answer: B — The text explicitly states the Indo-Ganga-Brahmaputra Plain attained maximum development during the third phase of Himalayan mountain formation approximately 64 million years ago.

Q3. The Northern Plain of India extends approximately how far from east to west?

  • A. 1,500 km
  • B. 2,000 km
  • C. 3,200 km ✓
  • D. 4,500 km

Answer: C — The text states the northern plains extend approximately 3,200 km from east to west, formed by alluvial deposits from the Indus, Ganga, and Brahmaputra rivers.

Q4. Which type of valleys are characteristic of the Peninsular region?

  • A. Deep gorges with steep sides
  • B. Shallow valleys with low gradients ✓
  • C. V-shaped valleys with rapids
  • D. U-shaped glacial valleys

Answer: B — The text states the river valleys in the Peninsula are shallow with low gradients due to the ancient, stable nature of the Peninsular Block.

Q5. Which of the following is NOT a characteristic of the Himalayas according to the passage?

  • A. Young, weak, and flexible geological structure
  • B. Still subjected to faulting, folding, and thrust plains
  • C. Rigid and stable like the Peninsular Block ✓
  • D. Dissected by fast-flowing rivers in youthful stage

Answer: C — The text explicitly contrasts the Himalayas as young and weak against the Peninsular Block which is rigid and stable, making option C incorrect.

Q6. The three major east-flowing Peninsular rivers that form deltas are: Assertion (A): Mahanadi, Krishna, and Godavari form deltas. Reason (R): East-flowing rivers of the Peninsula have high gradients that prevent delta formation.

  • A. Both A and R are correct; R explains A
  • B. Both A and R are correct; R does not explain A
  • C. A is correct but R is incorrect ✓
  • D. A is incorrect; R is correct

Answer: C — The Assertion is correct—these rivers do form deltas. However, the Reason is wrong: low gradients (not high) allow delta formation in Peninsular rivers.

Q7. Calculate the average width of the Himalayas given that the length is 2,500 km and the width varies from 160–400 km. Which statement best describes this proportion?

  • A. The Himalayas are approximately 6 to 16 times longer than they are wide
  • B. The Himalayas are approximately 10 to 20 times longer than they are wide ✓
  • C. The Himalayas are 4 times longer than they are wide
  • D. The Himalayas are equally long and wide

Answer: B — 2,500 km ÷ 160 km ≈ 15.6 times; 2,500 km ÷ 400 km ≈ 6.25 times; so roughly 6 to 15.6 times—option B (10–20) best encompasses this range.

Q8. Based on the landforms present (gorges, V-shaped valleys, rapids, waterfalls) and alluvial deposits of 1,000–2,000 m, which geological structure best explains both observations?

  • A. Young, active mountain uplift with concurrent river deposition ✓
  • B. Ancient, rigid Peninsula with block faulting only
  • C. Flat plain with no structural change
  • D. Glacial erosion creating U-shaped valleys

Answer: A — Young, active mountains (Himalayas) produce youthful landforms like gorges and V-shaped valleys; concurrent Ganga system deposits 1,000–2,000 m alluvium in the plain created by ongoing uplift.

Q9. Which physiographic division is characterised by relict and residual mountains like the Aravali Hills, Nallamala Hills, and Veliconda Hills?

  • A. The Northern Plain
  • B. The Indian Desert
  • C. The Peninsular Plateau ✓
  • D. The Northern and North-eastern Mountains

Answer: C — The text explicitly lists Aravali, Nallamala, Javadi, Veliconda, Palkonda, and Mahendragiri as relict and residual mountains of the Peninsular Plateau.

Q10. Why does the Peninsular Block remain rigid despite being part of the Indo-Australian Plate, while the Himalayas continue to deform rapidly?

  • A. The Peninsula is older and colder, preventing tectonic activity
  • B. The Peninsula has been stable since the Cambrian period with basement rocks; Himalayas are young and weakly structured from recent collision ✓
  • C. The Peninsula contains only igneous rocks whereas Himalayas contain sedimentary rocks
  • D. The Himalayas are located on a separate plate unaffected by the Indian plate movement

Answer: B — The text states the Peninsula has been standing rigid since Cambrian with ancient gneiss-granite base, while Himalayas are young and weak due to ongoing collision, hence still deforming.

Flashcards

What is the approximate age of the Indian plate's northward movement that still continues today?

The northward movement of the Indian plate began millions of years ago when it separated from the Australian plate and continues to the present day, causing ongoing tectonic activity.

Name the three major geological divisions of India.

The Peninsular Block, the Himalayas and other Peninsular Mountains, and the Indo-Ganga-Brahmaputra Plain.

What type of rocks form the foundation of the Peninsular Block?

Ancient gneisses and granites constitute the major foundation of the Peninsular Block, which has remained rigid since the Cambrian period.

Why do Himalayan rivers have V-shaped valleys while Peninsular rivers have shallow valleys?

Himalayan rivers are youthful and fast-flowing due to young, active mountains with high gradients, while Peninsular rivers are mature with low gradients due to ancient stable terrain.

What is the average depth of alluvial deposits in the Indo-Ganga-Brahmaputra Plain?

The average depth of alluvial deposits ranges from 1,000 to 2,000 metres.

Define physiography in geography terms.

Physiography is the outcome of three factors: structure, process, and the stage of development of a landscape.

Name three important east-flowing Peninsular rivers that form deltas.

The Mahanadi, Krishna, Kaveri, and Godavari are east-flowing rivers that form deltas before entering the Bay of Bengal.

What geological features in the Peninsula resulted from block faulting?

The rift valleys of the Narmada, Tapi, and Mahanadi, and the Satpura block mountains are examples of block faulting in the Peninsula.

Approximately how long is the Great Himalayan range from east to west?

The Great Himalayan range is approximately 2,500 km long from east to west, with a width varying between 160–400 km from north to south.

What originally was the Indo-Ganga-Brahmaputra Plain before it filled with sediments?

It was originally a geo-synclinal depression that reached maximum development about 64 million years ago during the third phase of Himalayan mountain formation.

Important Board Questions

Define physiography and explain how it is different from geology. [2 marks]

Physiography = structure + process + stage of development (landform outcome); geology = study of rocks and Earth's history. State the three components clearly and give one example of how process changes landforms.

Explain with two specific examples how the northward movement of the Indian plate has shaped the present geological structure of India. What are the ongoing consequences of this movement? [5 marks]

Example 1: Collision caused Himalayan uplift (ongoing, young, active, faults/folds); Example 2: Block faulting created rift valleys (Narmada, Tapi, Mahanadi) in Peninsula. Ongoing consequence: earthquakes, continued uplift, active deformation. Link plate tectonics to structural relief.

Compare and contrast the Peninsular Plateau and the Himalayan Mountains in terms of (a) age and stability, (b) river characteristics and landforms, (c) geological structure, and (d) future geomorphic activity. Use the NCERT India Physical map to mark one example of each physiographic division and explain how each represents the interplay of endogenic and exogenic forces. [6 marks]

Contrast: Peninsula—ancient, rigid, stable since Cambrian, shallow valleys, low gradient, relict mountains, mature rivers, deltas, minimal faulting; Himalayas—young, weak, active, V-shaped valleys, high gradient, fast-flowing rivers, gorges/rapids/waterfalls, ongoing faults/folds. Endogenic (plate motion, faulting) created structural relief; exogenic (erosion by rivers, weathering) shaped detailed landforms. Mark Aravali (Peninsula) and Mt. Kanchenjunga (Himalaya) on map; explain why Peninsula rivers form deltas while Himalayan rivers in gorges.

Assertion-Reason Questions for Structure and Physiography of India

Q1. Assertion (A):

The Peninsular Block has remained relatively stable since the Cambrian period despite being part of the moving Indo-Australian Plate.

Reason (R):

The Peninsular Block consists of ancient, rigid gneisses and granites that resist folding and faulting, unlike young, flexible mountain ranges.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both statements are true, and the reason correctly explains why the Peninsula remained stable—its rigid, ancient basement composition prevents significant deformation despite plate movements, unlike young mountains that fold and fault easily.

Q2. Assertion (A):

The Himalayan mountains are still undergoing active tectonic development with the formation of gorges, V-shaped valleys, and waterfalls.

Reason (R):

The Himalayas have reached the mature stage of mountain development and are no longer affected by endogenic and exogenic forces.

Answer: C — A is true but R is false — The assertion is true—the Himalayas are young and actively developing with youthful landforms. However, the reason is false because the Himalayas are NOT in the mature stage; they are actively shaped by both endogenic and exogenic forces. The reason contradicts the assertion's premise.

Q3. Assertion (A):

The Indo-Ganga-Brahmaputra Plain has average alluvial deposits of 1,000-2,000 m depth.

Reason (R):

This plain was formed as a geo-synclinal depression approximately 64 million years ago and has been gradually filled by sediments from Himalayan and Peninsular rivers.

Answer: B — Both A and R are true, but R is NOT the correct explanation of A — Both the assertion and reason are true—the alluvial depths are as stated, and the geo-synclinal origin with river infilling is the correct historical explanation. However, the reason does not directly explain WHY the deposits are 1,000-2,000 m deep; it only explains the origin of the depression and the source of sediments. The depth is a consequence, not explained by the reason.

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Case-Based Questions (CBQ) for Structure and Physiography of India

Case Study:

A geological survey team is studying the Narmada-Tapti river system of central India. They observe that these rivers flow through deep, parallel rift valleys bounded by elevated plateau surfaces on both sides. The underlying basement rocks show evidence of vertical displacement along fault planes. The rivers have relatively low gradients (3-4 m/km) but their valleys are structurally confined by steep fault scarps. Unlike the Himalayan rivers, these valleys do not show the erosional landforms of youth (gorges and waterfalls), yet they maintain distinct structural boundaries.

Q1. Which geological process best explains the formation of the Narmada-Tapti rift valleys?

  • A. Block faulting and vertical tectonic movements within the Peninsular Block ✓
  • B. Youthful river erosion creating V-shaped valleys through hard bedrock
  • C. Subsidence of the entire Peninsular Block due to the Indian plate's northward movement
  • D. Glacial erosion during Pleistocene ice ages

Answer: A

Q2. Why do the Narmada-Tapti valleys show fault-controlled boundaries rather than erosional V-shaped valleys despite having relatively low gradients?

  • A. The steep scarps are structural features created by faulting, not by river erosion ✓
  • B. These rivers are older and have reached their old age stage of development
  • C. The low gradient indicates the rivers are no longer capable of erosion
  • D. The bedrock is composed of sedimentary material resistant to lateral erosion

Answer: A

Q3. This case demonstrates that the Peninsular Block, despite its overall rigidity and stability, experienced:

  • A. Only horizontal movements and no vertical displacement
  • B. Localized vertical movements and block faulting creating rift valleys ✓
  • C. Complete subsidence into a geo-synclinal depression like the Northern Plain
  • D. No significant tectonic activity since the Cambrian period

Answer: B

Q4. The parallel structure and similar gradients of the Narmada and Tapti rivers suggest:

  • A. They originated from the same source and divide sediments equally
  • B. They were created by similar tectonic processes and follow parallel fault lines ✓
  • C. They are in the youthful stage of river development
  • D. They are both tributary systems of the Brahmaputra

Answer: B

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