Distribution of Oceans and Continents Class 11 Solutions 2026-27

Quick Solution. In Chapter 4, the answer key is: (i) (c), (ii) (c), (iii) (d), (iv) (c), and (v) (d).

Concept used. This MCQ set checks direct recall from the chapter: early ideas on continental fit, Wegener's forces, major and minor plates, sea floor spreading evidence, and the Indian plate boundary near the Himalayas.

1. For part (i), NCERT names Abraham Ortelius as the Dutch map maker who first proposed the possibility in 1596. So the answer is option (c).
2. For part (ii), pole-fleeing force is linked with the earth's rotation and its equatorial bulge. So the answer is option (c).
3. For part (iii), Nazca, Arabian, and Philippine plates are minor plates. Antarctica is listed as a major plate with surrounding oceanic plate. So the answer is option (d).
4. For part (iv), fossil distribution was evidence for continental drift. Sea floor spreading used volcanic activity, magnetic stripes, rock age, thin sediments, and earthquake-depth patterns. So the answer is option (c).
5. For part (v), the Himalayan boundary formed by collision of the Indian and Eurasian continental plates. So the answer is option (d).

(i) (c) Abraham Ortelius; (ii) (c) Rotation of the earth; (iii) (d) Antarctica; (iv) (c) Distribution of fossils in different continents; (v) (d) Continent-continent convergence.

Quick Solution. Wegener suggested two forces for continental drift: pole-fleeing force and tidal force.

Concept used. Wegener tried to explain why continents drifted. He connected one force with the earth's rotation and the other with the gravitational pull of the moon and the sun.

1. Wegener said the drifting continents were pushed by pole-fleeing force and tidal force.
2. Pole-fleeing force relates to the rotation of the earth.
3. Earth is not a perfect sphere. It bulges at the equator due to rotation.
4. Tidal force is linked with the attraction of the moon and the sun.
5. This attraction produces tides in oceanic waters.
6. Wegener believed that, over many million years, these forces could move continents.
7. Later scholars rejected these forces as too weak to explain drift.

Wegener suggested pole-fleeing force and tidal force as the two forces responsible for continental drift.

Quick Solution. Convectional currents begin because radioactive elements create thermal differences in the mantle. They continue as hot material rises, spreads, cools, and sinks.

Concept used. Convection is circular movement caused by heating and cooling. In the mantle, hotter material becomes lighter and rises. Cooler material becomes denser and sinks back. Chapter link. In Chapter 4 Distribution of Oceans and Continents, this convectional-current idea explains the force behind plate movement.

1. Radioactive elements inside the earth release heat.
2. This heat creates temperature differences in the mantle.
3. Hotter mantle material becomes less dense and rises toward the surface.
4. Near the upper mantle, the material spreads sideways and begins to cool.
5. On cooling, it becomes denser and sinks into deeper parts again.
6. This repeated rise, spread, cooling, and sinking forms a convection cell.
7. Continuous internal heat maintains these convectional currents over long periods.

Convectional currents are initiated by thermal differences caused by radioactive heat and maintained by repeated rising, spreading, cooling, and sinking of mantle material.

Quick Solution. At a transform boundary, plates slide past each other and crust is neither created nor destroyed. At divergent boundaries crust is created, while at convergent boundaries crust is destroyed.

Concept used. Plate boundaries are classified by what happens to the crust at the plate edge. Creation, destruction, or sideways movement separates the three types.

1. At divergent boundaries, plates move away from each other.
2. New crust is generated at spreading sites, such as the Mid-Atlantic Ridge.
3. At convergent boundaries, plates move toward each other.
4. One plate may dive under another at a subduction zone, so crust is consumed.
5. At transform boundaries, plates slide horizontally past each other.
6. No new crust is formed and no old crust is destroyed at a transform boundary.

Transform boundaries involve horizontal sliding with no crust creation or destruction, unlike divergent boundaries that create crust and convergent boundaries that destroy crust.

Quick Solution. During the formation of the Deccan Traps, the Indian landmass was still close to the equator and moving northward toward Eurasia.

Concept used. The Deccan Traps formed during the northward movement of the Indian plate. NCERT links the lava outpouring with the time when India was south of Asia and still near the equator.

1. India was once a large island separated from Asia by the Tethys Sea.
2. It began its northward journey when Pangaea broke.
3. During this journey, a major lava outpouring formed the Deccan Traps.
4. This began around 60 million years ago and continued for a long period.
5. At that time, the Indian subcontinent was still close to the equator.

The Indian landmass was close to the equator and moving northward when the Deccan Traps formed.

Quick Solution. The main evidences are jig-saw fit of continents, matching rocks across oceans, tillite deposits, placer deposits, and fossil distribution.

Concept used. Continental drift theory says the present continents were once joined and later drifted apart. Evidence must therefore show old connections across present oceans.

1. Jig-saw fit: The Atlantic coastlines of Africa and South America show a remarkable match. Bullard's later computer fit made the match clearer along the 1,000-fathom line.
2. Same-age rocks: Ancient rocks of about 2,000 million years on the Brazil coast match rocks in western Africa.
3. Tillite: Glacial tillite deposits of the Gondwana system occur in India, Africa, Falkland Island, Madagascar, Antarctica, and Australia. This points to a shared glacial past.
4. Placer deposits: Gold deposits on the Ghana coast have source rocks in Brazil. This makes sense if the two areas were once side by side.
5. Fossils: Identical land or freshwater fossils occur across present marine barriers. Mesosaurus fossils in South Africa and Brazil are a strong example.

The evidences are matching continents, same-age rocks, tillite deposits, placer gold deposits, and identical fossils across present oceans.

Quick Solution. Drift theory said continents moved. Plate tectonics says lithospheric plates move, and continents are parts of those moving plates.

Concept used. Drift theory and plate tectonics both explain changing continent positions, but they differ in what moves and how the movement is explained.

1. Alfred Wegener's drift theory proposed that all continents were once joined as Pangaea.
2. It said Pangaea split into Laurasia and Gondwanaland, and the continents then drifted to present positions.
3. Wegener treated continents as the main moving bodies.
4. His suggested forces, pole-fleeing force and tidal force, were not accepted as strong enough.
5. Plate tectonics says the lithosphere is divided into major and minor plates.
6. These plates include both continental and oceanic lithosphere.
7. Plates move as rigid units over the asthenosphere.
8. Plate tectonics also explains divergent, convergent, and transform boundaries, along with sea floor spreading and subduction.

Drift theory focused on moving continents, while plate tectonics explains movement of whole lithospheric plates carrying continents and ocean floors.

Quick Solution. Post-drift discoveries came mainly from ocean-floor mapping and palaeomagnetic studies. They revealed ridges, trenches, young ocean crust, magnetic stripes, thin sediments, and earthquake-depth patterns.

Concept used. Post-drift means discoveries made after Wegener's proposal. These discoveries shifted attention from continents alone to the ocean floor and helped build sea floor spreading and plate tectonics. In Chapter 4 Distribution of Oceans and Continents, this is the bridge from Wegener's drift idea to modern plate tectonics.

1. Ocean-floor mapping after World War II showed submerged mountain ranges and deep trenches.
2. Mid-oceanic ridges were found to be zones of common volcanic activity.
3. Rocks at equal distances on either side of ridge crests showed similar age, composition, and magnetic properties.
4. Rocks near the ridges were the youngest, while age increased away from the crest.
5. Oceanic crust was found to be much younger than continental crust, nowhere older than about 200 million years.
6. Sediments on the ocean floor were unexpectedly thin.
7. Deep trenches had deep-seated earthquakes, while mid-oceanic ridges had shallow earthquake foci.
8. These findings helped Hess propose sea floor spreading and prepared the ground for plate tectonics.

The major discoveries were ocean-floor relief, mid-oceanic volcanic ridges, magnetic stripes, young oceanic crust, thin sediments, trenches, and earthquake-depth patterns.