Distribution of Oceans and Continents

1.Continental Drift

• Early Ideas of Joined ContinentsImportance 3/5
  Who was the first to suggest that the Atlantic continents were once joined, what was his nationality, and in which year? Remember what Pellegrini added. Understand why the Atlantic coastlines prompted this idea, and how it differs from Wegener's full argument.
• Wegener's Continental Drift TheoryImportance 5/5UPSC 2014
  Remember who Wegener was by profession and nationality, and the year he put forward his theory. Understand its central claim: what the continents and oceans looked like at first, and what happened to them later.
• Pangaea, Panthalassa, Laurasia and GondwanalandImportance 4/5
  Remember what each of these four names refers to and what the first two names mean. Around when did Pangaea begin to split? Be clear which part became the northern and which the southern landmass, and which sea lay between them.
• Matching of Continents (Jig-Saw-Fit)Importance 4/5UPSC 2025
  Which two continents show the clearest match of coastlines? Remember who produced a computer fit of the Atlantic margins, and when. Why was the fit tried along the 1,000-fathom line and not along the present shoreline?
• Rocks of Same Age Across the OceansImportance 3/5
  How has radiometric dating helped link rocks on opposite sides of the Atlantic? Remember the belt of ancient rocks that matches between Brazil and western Africa, and its age. What does the Jurassic age of the earliest marine deposits suggest about the ocean?
• Tillite and the Gondwana System of SedimentsImportance 4/5UPSC 2025
  What is tillite, and how is it formed? Which southern landmasses have counterparts of the Gondwana sediments found in India? Explain why glacial deposits in lands that are warm today support both drift and a change of climate.
• Placer Deposits of Gold in GhanaImportance 3/5UPSC 2025
  What is a placer deposit, and how does it differ from gold found in rock veins? Why is the lack of a local source rock in Ghana puzzling? Understand how this points to a past link with Brazil.
• Distribution of Fossils (Lemurs and Mesosaurus)Importance 4/5
  Where are lemurs and their fossil relatives found? What was the lost land of Lemuria proposed to explain, and why was the idea dropped? What kind of reptile was Mesosaurus, and where are its fossils found? Explain why identical land or freshwater species on either side of an ocean need an explanation.
• Pole-Fleeing Force and Tidal ForceImportance 4/5
  Wegener proposed two forces for drifting. What does each of them relate to? Understand why most scholars found them far too weak.
• Weaknesses of Wegener's TheoryImportance 3/5
  Understand the main objections to the theory: weak forces, continents moving through the ocean floor as if it were passive, movement only towards the equator and the west, and no reason for the timing of the break-up. Which later ideas answered these objections?
• Convectional Current TheoryImportance 4/5
  Who discussed convection currents in the mantle, and around when? Understand what causes these currents. Explain how the idea tried to answer the objection about the force behind drifting.
• Mapping of the Ocean FloorImportance 3/5
  Understand why mapping of the ocean floor after World War II shifted the debate from evidence on land to evidence under the sea. Remember what the mapping showed about relief, ridges, trenches, the age of oceanic rocks and the rocks on either side of the ridge crests.
• Divisions of the Ocean Floor (Continental Margins, Abyssal Plains)Importance 2/5
  Remember the three major divisions of the ocean floor and the parts that make up a continental margin. Where do abyssal plains lie, and what collects on them?
• Mid-Oceanic RidgesImportance 4/5
  Remember how this ridge system compares with other mountain chains on earth, and why it is hidden from view. Understand its three parts (central rift, fractionated plateau, flank zone) and why the crest is a zone of volcanic activity.
• Global Belts of Earthquakes and VolcanoesImportance 4/5
  Know the path of the line of earthquake activity through the Atlantic and Indian Oceans, and where it splits near the Indian subcontinent. Which mountain system and which ocean rim form the other major belt? Understand how these belts coincide with ridges and young fold mountains.
• Depth of Earthquake Foci Across BeltsImportance 3/5
  How does the depth of earthquake foci change with the type of plate boundary? Compare ridges, trenches, the Alpine-Himalayan belt and the Pacific rim. Understand where deep-focus earthquakes occur and why.
• Rim of Fire Around the PacificImportance 4/5
  Which region is called the rim (or ring) of fire, and why? Understand how plate movement around the Pacific explains its earthquakes and volcanoes.

2.Concept of Sea Floor Spreading

• Volcanism and Rock Symmetry at Mid-Oceanic RidgesImportance 3/5
  Remember what is seen along the ridges: frequent eruptions, and rocks at equal distances on either side of the crest that match in age, make-up and magnetism. How does the age of rocks change away from the crest? Why does this symmetry suggest new crust forms at the crest?
• Palaeomagnetism and Magnetic StripingImportance 4/5UPSC 2018
  What is palaeomagnetism, and how do cooling basalts record the earth's magnetic field? Understand polarity reversals. Why do alternate normal and reversed stripes running parallel to a ridge support sea floor spreading? Which polarity is found nearest the crest?
• Age of Oceanic Crust and Thinness of Ocean SedimentsImportance 4/5
  How do the greatest ages of oceanic rocks and continental rocks compare? Remember the approximate maximum age of each. Why were scientists surprised to find thin sediments on the ocean floor, and what does this say about the age of the ocean floor?
• Hess's Sea Floor Spreading HypothesisImportance 5/5
  Who proposed the hypothesis, and around which year? Explain how eruptions at the ridge crest push the crust apart. Understand how Holmes's earlier idea influenced Hess.
• Consumption of Oceanic Crust at TrenchesImportance 4/5
  If one ocean spreads, why does another not shrink? Explain why Hess concluded that oceanic crust must be consumed, and where. Understand how this links to subduction.

3.Plate Tectonics

• Origin of the Plate Tectonics TheoryImportance 3/5
  Who put forward the theory, and in which year? Understand why interest in the distribution of oceans and continents revived after sea floor spreading, and how these scientists built on earlier ideas.
• Tectonic Plate and the LithosphereImportance 4/5
  What is a tectonic plate? What does the lithosphere include, how thick is it under oceans and under continents, and what does it move over? Distinguish a continental plate from an oceanic plate, with the Eurasian and Pacific plates as examples.
• Seven Major PlatesImportance 4/5
  Remember the seven major plates and the oceanic floor attached to each. Along which islands are the North and South American plates separated? Are the Indian and Australian plates counted as one plate or as two?
• Minor Plates (Cocos, Nazca, Arabian, Philippine, Caroline)Importance 4/5
  Remember where each of these five minor plates lies. Is the Antarctic plate a minor plate?
• Continental Drift and Plate Tectonics ComparedImportance 5/5
  Does a whole continent move, or a plate carrying it? Explain how the two views differ on what moves, and on the idea of a static earth against a dynamic earth. Understand how Pangaea fits in, and whether any plate has stayed still.
• Palaeomagnetic Reconstruction of Past PositionsImportance 3/5UPSC 1995
  How do scientists use palaeomagnetic data to fix the past positions of landmasses? Which rocks were analysed to trace Peninsular India? Understand the idea of continents changing position over about 540 million years.
• Divergent Boundaries and Spreading SitesImportance 5/5
  What happens at a divergent boundary, and what are spreading sites? Which is the best-known example, and which plates does it separate? Why is such a boundary also called constructive?
• Great African Rift Valley as Divergence on LandImportance 3/5UPSC 2026
  Which two plates are pulling apart in the Great African Rift Valley, and how far south does the active rift run from the Afar region? Distinguish divergence on land from divergence at an ocean ridge.
• Convergent Boundaries and Subduction ZonesImportance 5/5
  What happens to crust at a convergent boundary, and what is a subduction zone? Understand how it links to trenches, deep-focus earthquakes and volcanoes.
• Three Types of ConvergenceImportance 4/5
  Remember the three ways in which plates can converge. Understand what landform typically results from each.
• Transform BoundariesImportance 4/5
  What happens to crust at a transform boundary, and how does this differ from divergent and convergent boundaries? Remember one standard example in North America.
• Transform Faults Across Mid-Oceanic RidgesImportance 3/5
  How are transform faults placed in relation to mid-oceanic ridges? Understand how they connect the offset sections of a ridge.
• Magnetic Strips as a Measure of Plate MovementImportance 2/5
  How do the normal and reversed magnetic strips parallel to a ridge help scientists work out how fast plates move?
• Slowest and Fastest Spreading RidgesImportance 3/5
  Which ridge spreads slowest and which fastest? Remember their approximate rates, and where the fastest one lies.
• Convection Cells and the Earth's Internal HeatImportance 4/5
  Explain how a convection cell works in the mantle: what rises, what happens as it cools, and what follows. What are the two sources of the earth's internal heat? How do mantle convection, slab pull and ridge push each contribute to plate movement, and which is now thought to be the strongest?
• Hotspots and Mantle PlumesImportance 4/5
  What is a hotspot, and why is hotspot volcanism usually within a plate and not at a boundary? Which well-known hotspot is an exception, lying on a ridge? Understand how a moving plate over a nearly stationary hotspot leaves a chain of islands and dead volcanoes. Remember Hawaii and Réunion as examples.

4.Movement of the Indian Plate

• Extent of the Indian Plate and Its Northern BoundaryImportance 4/5
  Which landmasses does the Indian plate include? What type of plate boundary lies along the Himalayas?
• Eastern, Western and Southern Boundaries of the Indian PlateImportance 3/5
  Remember the features that mark each of these boundaries: Arakan Yoma and the Java Trench, the Kirthar range and the Makran coast, and the ridge with the Antarctic plate. Which segments are convergent, which are divergent and which are transform?
• India Before Its Northward JourneyImportance 3/5UPSC 1995
  Where did India lie before it moved north? What sea lay between India and Asia, and what closed it? When did India break away from Gondwana and begin its fast northward drift?
• Position of India Through Geological TimeImportance 3/5
  At about what latitude, south of the equator, was India roughly 140 million years ago? Understand how its position changed in the period since about 71 million years ago.
• Formation of the Deccan TrapsImportance 4/5
  At the end of which geological period did the lava outpouring that formed the Deccan Traps take place, and about when? Where did the subcontinent lie then in relation to the equator? Understand which hotspot is linked to it.
• Collision with Asia and the Rise of the HimalayasImportance 5/5
  When did India collide with Asia, and from when did the Himalayas begin to form? Understand how the collision caused uplift, and whether the Himalayas are still rising today. How fast did India move before the collision, and how did the speed change after it?

1. 1.

   With reference to Wegener's continental drift theory, consider the following statements:
   1. Alfred Wegener, a German meteorologist, put forth the theory in 1912.
   2. Pangaea first broke into Laurasia and Gondwanaland, forming the southern and northern components respectively.
   3. Pangaea began to split around 200 million years ago.
   Which of the statements given above is/are correct?

   1. A1 only
   2. B1 and 3 only
   3. C2 and 3 only
   4. D1, 2 and 3
2. 2.

   Consider the following:
   1. The jig-saw fit of the shorelines of Africa and South America
   2. Placer deposits of gold on the Ghana coast
   3. Distribution of Mesosaurus fossils
   4. Strips of normal and reverse magnetic field parallel to mid-oceanic ridges
   How many of the above were offered as evidence in support of the continental drift theory?

   1. AOnly one
   2. BOnly two
   3. COnly three
   4. DAll four
3. 3.

   Consider the following statements:
   Statement-I: The Ghana coast has rich placer deposits of gold although the source rock is absent in the region.
   Statement-II: The gold deposits of Ghana were derived from the Brazil plateau when the two continents lay side by side.
   Which one of the following is correct in respect of the above statements?

   1. ABoth Statement-I and Statement-II are correct and Statement-II explains Statement-I
   2. BBoth Statement-I and Statement-II are correct and Statement-II does not explain Statement-I
   3. CStatement-I is correct but Statement-II is incorrect
   4. DStatement-I is incorrect but Statement-II is correct
4. 4.

   Consider the following pairs:

   Evidence	Found in
   1. Mesosaurus skeletons	Southern Cape province of South Africa and Iraver formations of Brazil
   2. Belt of ancient rocks of 2,000 million years	Brazil coast and western Australia
   3. Earliest marine deposits of Jurassic age	Coastlines of South America and Africa

   How many of the pairs given above are correctly matched?

   1. AOnly one
   2. BOnly two
   3. CAll three
   4. DNone
5. 5.

   With reference to the force for drifting suggested by Wegener, consider the following statements:
   1. He suggested the pole-fleeing force and the tidal force.
   2. The pole-fleeing force relates to the revolution of the earth around the sun.
   3. Most scholars considered these forces to be totally inadequate.
   Which of the statements given above are correct?

   1. A1 and 2 only
   2. B2 and 3 only
   3. C1 and 3 only
   4. D1, 2 and 3
6. 6.

   Who first discussed, in the 1930s, the possibility of convection currents in the mantle generated by radioactive elements?

   1. AAlfred Wegener
   2. BHarry Hess
   3. CMcKenzie and Parker
   4. DArthur Holmes
7. 7.

   Consider the following facts revealed by ocean floor mapping and palaeomagnetic studies:
   1. Rocks closer to the mid-oceanic ridges have normal polarity and are the youngest.
   2. The age of rocks in the oceanic crust is nowhere more than 200 million years.
   3. The sediments on the ocean floor are unexpectedly thick.
   4. Rocks equidistant on either side of the crest show remarkable similarities in chemical composition and magnetic properties.
   How many of the above statements are correct?

   1. AOnly one
   2. BOnly two
   3. COnly three
   4. DAll four
8. 8.

   Consider the following statements:
   Statement-I: Hess maintained that oceanic crust sinks down and gets consumed at the oceanic trenches.
   Statement-II: The spreading of one ocean does not cause the shrinking of another.
   Which one of the following is correct in respect of the above statements?

   1. ABoth Statement-I and Statement-II are correct and Statement-II explains Statement-I
   2. BBoth Statement-I and Statement-II are correct and Statement-II does not explain Statement-I
   3. CStatement-I is correct but Statement-II is incorrect
   4. DStatement-I is incorrect but Statement-II is correct
9. 9.

   With reference to plate boundaries, consider the following statements:
   1. At transform boundaries, crust is destroyed as one plate dives under another.
   2. The best-known example of a divergent boundary is the Himalayas.
   Which of the statements given above is/are correct?

   1. A1 only
   2. B2 only
   3. CBoth 1 and 2
   4. DNeither 1 nor 2
10. 10.

    Which one of the following has the fastest rate of plate movement?

    1. AThe Arctic Ridge
    2. BThe Mid-Atlantic Ridge
    3. CThe East Pacific Rise near Easter Island
    4. DThe Chagos Archipelago spreading site
11. 11.

    With reference to the boundaries of the Indian plate, consider the following statements:
    1. Its northern boundary along the Himalayas is a continent–continent convergence.
    2. Its western margin follows the Kirthar Mountain of Pakistan.
    3. The boundary between the Indian and Antarctic plates is a transform boundary.
    Which of the statements given above is/are correct?

    1. A1 only
    2. B1 and 2 only
    3. C2 and 3 only
    4. D1, 2 and 3
12. 12.

    Consider the following events in the movement of the Indian plate:
    1. Outpouring of lava began forming the Deccan Traps
    2. India collided with Asia
    3. India started its northward journey
    4. The subcontinent was located as far south as 50°S latitude
    Which one of the following is the correct chronological sequence of the above events?

    1. A3–4–1–2
    2. B4–3–1–2
    3. C3–1–4–2
    4. D4–3–2–1
13. 13.

    With reference to the theory of plate tectonics, consider the following statements:
    1. It was put forward in 1967 by McKenzie and Parker and, independently, by Morgan.
    2. According to it, it is the continents that move, not the plates.
    Which of the statements given above is/are correct?

    1. A1 only
    2. B2 only
    3. CBoth 1 and 2
    4. DNeither 1 nor 2
14. 14.

    Consider the following plates:
    1. Pacific plate
    2. Nazca plate
    3. Arabian plate
    4. India-Australia-New Zealand plate
    5. Cocos plate
    How many of the above are minor plates?

    1. AOnly two
    2. BOnly three
    3. COnly four
    4. DAll five
15. 15.

    Consider the following statements:
    1. Abyssal plains lie between the continental shore and the continental shelf.
    2. Earthquakes along the Alpine-Himalayan belt generally have shallow foci.
    Which of the statements given above is/are correct?

    1. A1 only
    2. B2 only
    3. CBoth 1 and 2
    4. DNeither 1 nor 2

1. 1.

   UPSC 2014

   Which of the following phenomena might have influenced the evolution of organisms?
   1. Continental drift
   2. Glacial cycles
   Select the correct answer using the code given below.

   1. A1 only
   2. B2 only
   3. CBoth 1 and 2
   4. DNeither 1 nor 2
2. 2.

   UPSC 2026

   Which of the following statements with reference to Lake Turkana is/are correct ?
   1. It is the largest desert lake in the world.
   2. The lake is situated in South Sudan along the eastern fringe of the Sahara desert.
   3. The lake is listed as a UNESCO World Heritage Site and is also referred to as the ‘Jade Sea’.
   Select the answer using the code given below :

   1. A1 only
   2. B1 and 3 only
   3. C2 and 3 only
   4. D1, 2 and 3
3. 3.

   UPSC 2025

   Which of the following are the evidences of the phenomenon of continental drift?
   I. The belt of ancient rocks from Brazil coast matches with those from Western Africa.
   II. The gold deposits of Ghana are derived from the Brazil plateau when the two continents lay side by side.
   III. The Gondwana system of sediments from India is known to have its counterparts in six different landmasses of the Southern Hemisphere.
   Select the correct answer using the code given below.

   1. AI and III only
   2. BI and II only
   3. CI, II and III
   4. DII and III only
4. 4.

   UPSC 1995

   The palaeomagnetic results obtained from India indicate that in the past, the Indian land mass has moved

   1. Anorthward
   2. Bsouthward
   3. Ceastward
   4. Dwestward
5. 5.

   UPSC 1995

   The Indian subcontinent was originally part of a huge land mass called

   1. AJurassic Land Mass
   2. BAryavarta
   3. CIndiana
   4. DGondwana Continent
6. 6.

   UPSC 2018

   Consider the following statements :
   1. The Earth’s magnetic field has reversed every few hundred thousand years.
   2. When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
   3. When living organisms originated, they modified the early atmosphere of the Earth.
   Which of the statements given above is/are correct ?

   1. A1 only
   2. B2 and 3 only
   3. C1 and 3 only
   4. D1, 2 and 3