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Distribution of Oceans and Continents Class 11 Important Extra Questions Geography Chapter 4

 

🌍 Class 11 Geography – Chapter 4

❓ Important Questions & Answers (Exam-Oriented)

❓ Question 1

What is Pangaea? (पैंजिया क्या है?)
✅ Answer (उत्तर):
🌐 All landmasses of the world were once a single supercontinent called Pangaea (पैंजिया).

❓ Question 2

Who first propounded the theory of continental drift? (महाद्वीपीय विस्थापन का सिद्धांत किसने दिया?)
✅ Answer (उत्तर):
👨‍🔬 The theory of Continental Drift was propounded by Alfred Wegener in 1912.

❓ Question 3

Which plate is composed mainly of oceanic crust? (कौन सी प्लेट मुख्यतः महासागरीय परत से बनी है?)
✅ Answer (उत्तर):
🌊 The Pacific Plate is mainly composed of oceanic crust.

❓ Question 4

How did the Himalayas rise? (हिमालय कैसे बने?)
✅ Answer (उत्तर):
⛰️ The collision between the Indian Plate and the Eurasian Plate gave rise to the Himalayas.

❓ Question 5

What is the evidence in support of Continental Drift Theory? (महाद्वीपीय विस्थापन सिद्धांत के समर्थन में प्रमाण लिखिए।)
✅ Answer (उत्तर):
🔎 Evidence includes:

  1. 🪨 Geological matching (भूगर्भीय समानता)

  2. ❄️ Palaeoclimatic unity (प्राचीन जलवायु समानता)

  3. 🧲 Palaeomagnetism (प्राचीन चुम्बकत्व)

❓ Question 6

Name the continents into which the supercontinent Pangaea got split. (पैंजिया किन महाद्वीपों में विभाजित हुआ?)
✅ Answer (उत्तर):
🌍 Pangaea split into two parts:

  • Laurasia (Northern part)

  • Gondwanaland (Southern part)

❓ Question 7

How many years ago did Pangaea evolve? (पैंजिया का निर्माण कितने वर्ष पूर्व हुआ था?)
✅ Answer (उत्तर):
🕰️ Pangaea evolved about 280 million years ago.

❓ Question 8

What are Hot Spots? (हॉट स्पॉट क्या होते हैं?)
✅ Answer (उत्तर):
🔥 Hot Spots are the centres of volcanic activity (ज्वालामुखीय क्रियाओं के केंद्र).

❓ Question 9

Name the three kinds of boundaries based on their relative motion. (प्लेट सीमाओं के तीन प्रकार बताइए।)
✅ Answer (उत्तर):
🗺️ Plate Boundaries are of three types:

  1. ↔️ Divergent/Spreading Margins (विसरण सीमाएँ)

  2. ↕️ Convergent Margins (अभिसरण सीमाएँ)

  3. 🔀 Transform Faults / Fracture Zones (परिवर्तन भ्रंश क्षेत्र)

❓ Question 10

How many plates is the lithosphere divided into? (भूपर्पटी कितनी प्लेटों में विभाजित है?)
✅ Answer (उत्तर):
🌍 The lithosphere is divided into 7 major plates.

❓ Question 11

The collision between which two plates gave rise to the Himalayas? (हिमालय किन दो प्लेटों की टक्कर से बने?)
✅ Answer (उत्तर):
⛰️ The Indian Plate and the Eurasian Plate collided to form the Himalayas.

❓ Question 12

Name two fossils that tell us continents were once united. (ऐसे दो जीवाश्म लिखिए जो बताते हैं कि महाद्वीप एक थे।)
✅ Answer (उत्तर):
🦖 Fossils of –

  1. 🌿 Glossopteris (plant)

  2. 🐊 Mesosaurus & Lystrosaurus (animals)

These prove the unity of continents.

❓ Question 13

What is Palaeomagnetism? (पैलियोमैग्नेटिज़्म क्या है?)
✅ Answer (उत्तर):
🧲 Fossil magnetism preserved in igneous rocks like Magnetite, Hematite, Pyrrhotite, etc.

❓ Question 14

What is the Pacific Plate? (प्रशांत प्लेट क्या है?)
✅ Answer (उत्तर):
🌊 The largest plate in terms of formation and origin.

❓ Question 15

What do you understand by spreading of crust from ridge and widening of ocean basin? (क्रस्ट के फैलने और महासागरीय बेसिन चौड़ा होने को क्या कहते हैं?)
✅ Answer (उत्तर):
🌐 This process is called Sea-floor Spreading.

❓ Question 16

Name the northern and southern parts of Pangaea. (पैंजिया के उत्तरी और दक्षिणी भागों के नाम लिखिए।)
✅ Answer (उत्तर):
🌍 Laurasia (North) and Gondwanaland (South).

❓ Question 17

Name the sea separating Laurasia and Gondwanaland. (लॉरेशिया और गोंडवानालैंड को अलग करने वाला समुद्र कौन सा था?)
✅ Answer (उत्तर):
🌊 The Tethys Sea.

❓ Question 18

In which parts was Pangaea split? (पैंजिया किन भागों में विभाजित हुआ?)
✅ Answer (उत्तर):
🌐 Laurasia (Northern continent) and Gondwanaland (Southern continent).

❓ Question 19

Name the original supercontinent. When was it formed? (मूल सुपरकॉन्टिनेंट का नाम और उसका निर्माण कब हुआ?)
✅ Answer (उत्तर):
🌍 The original supercontinent was Pangaea, formed about 280 million years ago.

❓ Question 20

State three causes of plate movements. (प्लेटों की गति के तीन कारण बताइए।)
✅ Answer (उत्तर):

  1. 🔥 Thermal convection (ऊष्मीय संवहन)

  2. 🌋 Volcanic hot spots

  3. 🌊 Movement of currents

❓ Question 21

What is meant by Sea-floor Spreading? (सी-फ्लोर स्प्रेडिंग क्या है?)
✅ Answer (उत्तर):
🌊 The crust spreads away from mid-ocean ridges and the ocean basin widens → This is Sea-floor Spreading.

❓ Question 22

Name the process in which one plate overrides another and slips into the mantle. (वह प्रक्रिया कौन सी है जिसमें एक प्लेट दूसरी के नीचे डूब जाती है?)
✅ Answer (उत्तर):
⬇️ This process is called Subduction (अधोवेशन).

❓ Question 23

What is Thermal Convection? (थर्मल कन्वेक्शन क्या है?)
✅ Answer (उत्तर):
🔥 It is the driving force for the movement of plates.

❓ Question 24

Name the four types of plate interactions. (प्लेटों की परस्पर क्रियाओं के चार प्रकार लिखिए।)
✅ Answer (उत्तर):

  1. ↔️ Spreading

  2. ↕️ Collision

  3. ⬇️ Subduction

  4. 🔀 Transform Faults

❓ Question 25

How was drifting of continents caused? (महाद्वीपों का विस्थापन किन कारणों से हुआ?)
✅ Answer (उत्तर):
It was caused by –

  1. 🌀 Pole-fleeing force (ध्रुव से दूर जाने वाली शक्ति)

  2. 🌊 Tidal force (ज्वारीय शक्ति)


❓ Question 2

Discuss the Continental Drift Theory. (महाद्वीपीय विस्थापन सिद्धांत पर चर्चा कीजिए।)

✅ Answer (उत्तर):

📌 Introduction

🌐 The Continental Drift Theory was proposed by Alfred Wegener (1912).
👉 He suggested that all landmasses were once a single supercontinent called Pangaea (पैंजिया).

🕰️ Historical Development of Pangaea

  1. Formation – Pangaea evolved about 280 million years ago (end of Carboniferous period).

  2. Split into Two – By 150 million years ago (Jurassic Age), Pangaea divided into:

    • Laurasia (Northern continent)

    • Gondwanaland (Southern continent)

  3. Further Breakup – Around 65 million years ago (Cretaceous Period), Gondwanaland split into:

    • South America 🌎

    • Africa 🌍

    • Australia 🇦🇺

    • Antarctica ❄️

  4. Present Distribution – The drifting apart of these landmasses formed present continents, and the hollows became oceans.

🔎 Evidences in Support of Continental Drift

  1. 🪨 Geological Matching (भूगर्भीय समानता) – Similar rock formations on different continents.

  2. ❄️ Palaeoclimatic Evidence (प्राचीन जलवायु प्रमाण) – Glacial deposits found in tropical regions.

  3. 🧲 Palaeomagnetism (प्राचीन चुम्बकत्व) – Magnetic orientation in rocks proves movement of plates.

🏁 Conclusion

✅ The present distribution of continents and oceans is the result of the fragmentation & drifting of Pangaea.
👉 Thus, Wegener’s theory laid the foundation of modern plate tectonics.

❓ Question 3

Describe Sea-floor Spreading in brief. (सी-फ्लोर स्प्रेडिंग का संक्षेप में वर्णन कीजिए।)

✅ Answer (उत्तर):

📌 Explanation

  1. 🌍 The present distribution of continents has mainly occurred in the last 65 million years, and the drift still continues.

  2. 🌋 Mid-ocean ridges (महासागरीय मध्य पर्वतमाला) are long cracks on the ocean floor where molten rocks (lava) rise and form new crust.

  3. ↔️ The new crust spreads on both sides of the ridge, causing the ocean basin to widen.
    👉 This process is called Sea-floor Spreading (महासागरीय तल का प्रसार).

🌐 Examples

  • The South Atlantic Ocean widened and separated Africa & South America.

  • The Red Sea is an active crack that may become a new ocean in the future.

  • The Atlantic Ocean continues to change its size.

🏁 Conclusion

✅ Sea-floor spreading explains how continents drift apart and how oceans are formed & expanded over geological time.



❓ Question 5

Describe the main features of the Indian Plate. (भारतीय प्लेट की मुख्य विशेषताओं का वर्णन कीजिए।)

✅ Answer (उत्तर):

📌 Topography of Indian Ocean Floor

  1. 🌊 The Indian Ocean floor shows striking topography with ridges and plateaus.

  2. 🗻 Important ocean ridges:

    • Mascarene Plateau

    • Chagos–Maldive–Lakshadweep Ridge
      👉 These are volcanic tracts formed due to hot spots (ज्वालामुखीय हॉट स्पॉट्स).

📌 Major Geological Features

  1. The Ninety-East Ridge extends northward into the trench, where the seafloor was consumed below the Indian continental mass.

  2. The Chagos–Lakshadweep Ridge once connected the Carlsberg Ridge (Arabian Sea) with the Southeast Indian Ridge during the Eocene period (~50 million years ago).

📌 Collision & Himalaya Formation

  1. 🗻 Due to the movement of the Indian Plate northward, it collided with the Eurasian Plate.

  2. This collision gave rise to the Himalayas.

  3. The suture zone (जोड़ क्षेत्र) between Indian and Eurasian plates lies along the Indus & Brahmaputra river valleys.

🏁 Conclusion

✅ The Indian Plate is unique as it includes both continental and oceanic parts, active volcanic ridges, and played a major role in the formation of the Himalayas through plate collision.


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