Discuss how the changes in shape and sizes of continents and ocean basins of the planet take place due to tectonic movements of the crustal masses. (Answer in 250 words)

Introduction

The Earth’s lithosphere is divided into several tectonic plates that move slowly over the semi-molten asthenosphere. According to the Plate Tectonics, these crustal movements continuously modify the shape and size of continents and ocean basins through processes such as divergence, convergence, and lateral displacement.

Tectonic Processes Responsible for Changes

(In the exam, a small diagram showing divergent, convergent and transform boundaries can be drawn.)

1. Divergent Plate Boundaries (Seafloor Spreading)

• Plates move apart and magma rises to create new oceanic crust.

• Causes widening of oceans and formation of mid-ocean ridges.

• Example: Expansion of the Atlantic Ocean due to seafloor spreading along the Mid-Atlantic Ridge.

2. Convergent Plate Boundaries (Subduction and Collision)

• One plate subducts beneath another, forming trenches and volcanic arcs, which reshape ocean basins.

• Continental collisions create fold mountains and alter continental boundaries.

• Example: Formation of the Himalayas due to collision of the Indian and Eurasian plates.

3. Transform Plate Boundaries

• Plates slide past each other, causing faulting and earthquakes that modify crustal structures and landscapes.

4. Continental Drift and Supercontinent Cycles

• Earlier supercontinents like Pangaea fragmented into present continents, changing the configuration of oceans and landmasses over geological time.

Conclusion

Thus, tectonic movements continuously reshape the Earth’s surface by creating new crust, destroying old crust, and rearranging continents and oceans. These dynamic processes explain the evolving geography of the planet over millions of years.