Sunday, March 4, 2018

India Physiography Rendition

I came across this physiography rendition of India via Simon Kuestemacher.

The contrast between the Himalaya and the Indo-Gangetic plain is awesome. But I was struck by other features in the Peninsular region.

1) The E-W oriented linear depression in Central India. This is the Narmada rift valley which accommodates the west flowing Narmada river. The rift is part of the Central Indian Tectonic Zone, a wide zone of continental deformation formed in the early -mid Proterozoic (between 2 - 1 billion years ago) during the collision and eventually suturing of the Dharwar and Bundelkhand cratonic blocks.

2) Distinct mountain belts are seen along the eastern margin of India. These comprise the early -mid Proterozoic Eastern Ghats and the Nallamalai fold and thrust belts. The Eastern Ghats are a granulite grade terrain, with evidence of the original sedimentary basins being caught up in multiple cycles of metamorphism and deformation. The Nallamalai fold and thrust belt was a basin on the eastern extremity of the Cuddapah Basin. This terrain is thrust westwards over the Cuddapah's.

3) The Western Ghats, especially the Deccan Volcanic terrain, are revealed as the edge of the dissected plateau. These are not a distinct orogenic belt like those on the eastern margin. Rather, the edge is a retreated fault scarp. The Deccan volcanic plateau once extended further to the west. The separation of India from Seychelles caused the western margin of India to subside along faults that now lie under the Arabian Sea. Erosion has caused the original cliff to retreat eastwards. And some vertical uplift has accentuated the topography of the region.

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