Palaeomagnetism and Sea Floor Spreading I Geography Optional I UPSC PYQs

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Q.”Evidences from palaeomagnetism and sea floor spreading have validated that continents and ocean basins have never been stationary." Elucidate with suitable diagrams. (20 marks / 2023)
The theory of plate tectonics, which describes the large-scale movement of Earth's lithosphere, is supported by various lines of evidence. Two key pieces of evidence are paleomagnetism and sea floor spreading. These concepts have demonstrated that continents and ocean basins are not stationary, but rather in constant motion.
Paleomagnetism is the study of the record of Earth's magnetic field in rocks, sediment, and archaeological materials.
1. Magnetic Stripes on the Ocean Floor : When new oceanic crust forms at mid-ocean ridges, it records the Earth's magnetic field. This process creates symmetrical patterns of magnetic stripes on either side of the ridge, corresponding to periods of normal and reversed magnetic polarity.
2. Polar Wandering Curves : The paths that indicate the historical positions of the magnetic poles relative to different continents can be constructed. When the polar wandering paths of different continents are compared, they show that continents have moved relative to each other and to the poles.
Sea floor spreading is the process by which new oceanic crust is formed at mid-ocean ridges and slowly moves away from the ridge, creating new ocean floor.
1. Age of Oceanic Crust : The age of the ocean floor increases with distance from mid-ocean ridges. Radiometric dating of basaltic rock samples reveals that rocks are youngest near the ridges and oldest near the continents.
2. Heat Flow and Earthquakes : Higher heat flow is observed near mid-ocean ridges, where new crust is being formed. Additionally, the pattern of earthquakes along mid-ocean ridges and transform faults supports the idea of plates moving apart and sliding past each other.
The symmetrical patterns of magnetic stripes on the ocean floor, the ages of oceanic crust, and polar wandering curves all support the theory of plate tectonics, demonstrating that Earth's lithosphere is in constant motion. These findings have revolutionized our understanding of Earth's dynamic nature and the processes shaping its surface.
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