Distribution of Oceans and Continents | Class 11 Geography Notes

Evidence in Support of the Continental Drift

Several lines of evidence support the Continental Drift theory, demonstrating that continents were once joined and have since drifted apart. One of the most striking evidences is the 'jigsaw fit' of the continents, especially the matching coastlines of Africa and South America. Bullard (1964) used computer mapping to fit the continental margins at the 1,000-fathom line, which showed an almost perfect fit. Radiometric dating has revealed that ancient rocks of about 2,000 million years on the Brazilian coast match those on the western coast of Africa. The earliest marine deposits along these coasts are Jurassic in age, indicating the ocean did not exist before that time. Tillite, a sedimentary rock formed from glacial deposits, is found in India and has counterparts in Africa, Madagascar, Antarctica, Australia, and the Falkland Islands, indicating these landmasses were once connected. Placer deposits of gold found in Ghana, with no local source rock, are believed to have originated from Brazil when the continents were joined. Fossil evidence, such as the Mesosaurus reptile found only in South Africa and Brazil, and the distribution of Lemurs in India, Madagascar, and Africa, further supports the theory. These fossils could not have crossed oceans, implying land connections in the past.

📊 Diagram: No specific diagram in this section but references the jigsaw fit concept illustrated in earlier figures.

🧪 Activity: Compare the coastlines of South America and Africa on a map to observe the jigsaw fit.

🔗 Connection: Introduces the forces proposed for continental movement, leading to the next section.