UPSC Mains Answer Writing
Geography
Compare and contrast the Continental Drift theory, Sea Floor Spreading theory and the Plate Tectonic theory.
Approach
- Brief intro about the evolution of these theories
- Comparision between them
- Conclusion
After various experiments, research and observations, scientists found that there are some regions which undergo some kind of polar events as well as it also undergoes very hot climate over its geological history.
To undergo any climatic variation, there are only two possible reasons -
- Either the continents remain stationary, and the climatic zone shifted. or
- The climatic zones remain stationary, and the continents moved.
Since, Scientists did not find any evidence of shifting of climatic zones (as it depends on Earth's rotation, revolution, tilt and latitudinal extent of the region), many scientists proposed theories to explain these major variations in the Earth's climatic condition.
Three most important theories which described or tried to describe this continental movement are -
Comparison between Continental drift theory, Sea floor spreading theory and Plate tectonic theory are -
Continental drift theory -
- Propounded by - Alfred Wegener
- Explanation of the theory - Continental crust is floating over Oceanic crust
- It explains the movement of continents only
- Forces responsible - Gravitational force, Buoyant force, Tidal force, etc
- Limitations - Forces envisaged were not considered adequate. Also, Continental crust and Oceanic crust are rigid and can't freely float one over another
- Evidences - Fossil evidence, Glacial deposits, Structural evidence
Sea-floor spreading theory -
- Propounded by - Henry Hess
- Explanation of the theory - Oceanic crust is continuously spreading on both sides of the Mid-oceanic ridge
- It explains the movement of Oceanic crust only
- Forces responsible - Convection current in the mantle
- Limitations - It did not explain the movement of the Continental crust
- Evidences - Presence of Mid-oceanic ridges, Rocks of similar properties are found at equidistant from the mid-oceanic ridge, Age of rocks increases as we move away from the mid-oceanic ridge
Plate Tectonic theory -
- Propounded by - Morgan and Kenzie & Parker
- Explanation - Lithosphere containing both continental crust and oceanic crust moves over underlying Asthenosphere
- It explains the movement of both continents as well as oceanic crust
- Forces responsible - Convection current, Mantle plumes, etc
- Limitations - It did not explain the formation of earlier mountains, movements of different plates and how they are different from the present one
- Evidences - Seismic waves (Earthquake waves); Presence of Mid-oceanic ridges, trenches, volcanoes at the plate boundary; Formation of mountains; Formation of Red Sea, etc
Among the given three theories, Plate tectonic theory is most accepted. However, the latter two theories also had some relevance. They provided the basis for the development of Plate tectonic theory.
Notes to boost your Preparation
Optional Notes
Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own.
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