Subject: Physical Geography

Answer:

The Theory of Continental Drift, proposed by Alfred Wegener in 1912, suggests that continents were once joined together in a single landmass called Pangaea before breaking apart and drifting to their present positions through horizontal movements across the ocean floor.

Key Components of Continental Drift Theory

• The theory proposes that the earth's crust is made up of lighter Sial (Silicon + Aluminum) and denser Sima (Silicon + Magnesium) layers.
• The continents (Sial) float and move horizontally over the denser oceanic crust (Sima).
• The movement is attributed to forces like pole-fleeing force and tidal force.

Evidence Supporting Continental Drift

Geological Evidence

• Matching Rock Types: Similar rock formations and mountain chains found across separated continents (e.g., Appalachian Mountains in North America and Caledonian Mountains in Scotland).
• Glacial Deposits: Presence of ancient glacial deposits in currently warm regions like Africa, South America, and India.

Biological Evidence

• Similar Fossil Distribution: Identical fossil plants (Glossopteris) found across different continents.
• Distribution of Living Species: Similar species found in widely separated regions suggesting previous connections.

Geometrical Evidence

• Jigsaw Fit: The coastlines of continents, especially South America and Africa, fit together like puzzle pieces.
• Continental Shelf: Similar continental shelf structures across separated landmasses.

Contemporary Evidence

• Plate Movement Measurements: The Indian Plate moves northeast at 5 cm per year, while the Eurasian Plate moves north at 2 cm per year.
• Paleomagnetism: Study of magnetic properties in rocks indicating their formation at different latitudes.

Today, the Theory of Continental Drift has evolved into the more comprehensive Plate Tectonic Theory, supported by modern technologies like GPS tracking and satellite measurements, providing real-time evidence of continental movement and validation of Wegener's revolutionary concept.