The Continental Drift Theory (CDT), proposed by Alfred Wegener in 1912, posits that the continents were once part of a supercontinent called Pangaea and have since drifted apart to their current locations. Several lines of evidence support this theory:
1. Fit of the Continents:
The coastlines of continents, particularly those on opposite sides of the Atlantic Ocean, appear to fit together like pieces of a jigsaw puzzle.
- Example: The eastern coast of South America fits closely with the western coast of Africa. This suggests that these continents were once joined.
2. Fossil Evidence:
Identical fossils of plants and animals have been found on continents now separated by vast oceans.
- Glossopteris: Fossils of this extinct plant, a fern-like species, have been found in South America, Africa, Antarctica, India, and Australia, indicating these continents were once connected.
- Mesosaurus: Fossils of this freshwater reptile have been found in both South America and Africa. It is unlikely that this species could have crossed the Atlantic Ocean, suggesting the continents were once joined.
3. Geological Evidence:
Similar rock formations and mountain ranges are found on continents that are now far apart.
- Mountain Ranges: The Appalachian Mountains in North America are geologically similar to the Caledonian Mountains in Scotland and Scandinavia, suggesting these regions were once part of the same landmass.
- Rock Strata: Identical rock layers and structures, such as those found in the Karoo strata of South Africa and the Santa Catarina system in Brazil, support the idea of connected continents.
4. Climatic Evidence:
Evidence of past climates found in now disparate regions indicates the continents were once positioned differently.
- Glacial Deposits: Evidence of ancient glaciation, such as striations and tillites, is found in present-day India, South America, Africa, and Australia. These continents must have been located closer to the South Pole in the past to support extensive glaciation.
- Coal Deposits: Large coal beds in Antarctica indicate that this region once had a tropical climate, suggesting it was previously located closer to the equator.
5. Paleontological Evidence:
The distribution of certain fossil species suggests that continents were once connected.
- Lystrosaurus: Fossils of this land reptile have been found in Africa, India, and Antarctica, indicating these landmasses were once connected.
- Cynognathus: This mammal-like reptile’s fossils are found in South America and Africa, supporting the idea of a connected Gondwana.
6. Paleomagnetic Evidence:
The study of the Earth’s past magnetic field recorded in rocks (paleomagnetism) provides evidence for continental drift.
- Magnetic Alignment: Rocks of the same age from different continents show different magnetic alignments, suggesting the continents were once aligned differently and have since moved.
- Polar Wandering: The apparent movement of the magnetic poles, known as polar wandering, can be better explained by the movement of continents rather than the poles themselves.
7. Distribution of Natural Resources:
The locations of certain mineral and fossil fuel deposits align better with the theory of continental drift.
- Coal Beds: The presence of coal beds in regions such as North America, Europe, and Asia suggests these areas were once part of a single, vast swampy region.
- Oil Deposits: Similar oil reserves found in West Africa and South America suggest these areas were once connected.
8. Sea-Floor Spreading:
Although this evidence was developed after Wegener’s time, it strongly supports the idea of moving continents.
- Mid-Atlantic Ridge: The discovery of the Mid-Atlantic Ridge and the process of sea-floor spreading provide a mechanism for the movement of continents. New oceanic crust is formed at divergent boundaries, pushing continents apart.
- Age of Oceanic Crust: The age of the ocean floor increases with distance from mid-ocean ridges, supporting the idea that new crust is continuously being formed and pushing older crust away.
9. Matching Geological Structures:
Specific geological formations match across continents that are now separated by oceans.
- Cape Fold Belt and Sierra de la Ventana: The Cape Fold Belt in South Africa matches geological structures found in the Sierra de la Ventana in Argentina, suggesting these areas were once connected.
Conclusion:
The evidence supporting the Continental Drift Theory comes from multiple scientific disciplines, including geology, paleontology, climatology, and oceanography. The theory provides a cohesive explanation for the distribution of continents, fossil species, rock formations, and climatic evidence observed around the world. The subsequent development of Plate Tectonics Theory has provided a detailed mechanism for continental drift, reinforcing Wegener’s pioneering ideas.
