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The Peninsular Block
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- The N boundary of the Peninsular Block – line running from Kachchh along the western flank of the Aravali Range near Delhi and then roughly parallel to the Yamuna and the Ganga as far as the Rajmahal Hills and the Ganga delta.
- Karbi Anglong +Meghalaya Plateau in the northeast and Rajasthan in the west are also extensions of this block.
- The north- eastern parts are separated by the Malda fault in West Bengal from the Chotanagpur plateau.
- In Rajasthan, the desert and other desert–like features overlay this block.
- The Peninsula is formed by a great complex of very ancient gneisses and granites
- Due to Indo-Australian Plate- vertical movements and block faulting
- Examples- Rift valleys of the Narmada, the Tapi and the Mahanadi and the Satpura block mountains
- The Peninsula mostly consists of relict and residual mountains like the Aravali hills, the Nallamala hills, the Javadi hills, the Velikonda hills, the Palkonda range and the Mahendragiri hills, etc.
- The river valleys here are shallow with low gradients.
- Most of the east flowing rivers form deltas before entering into the Bay of Bengal.
- Examples- Mahanadi, the Krishna, the Kaveri and the Godavari
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The Himalayas And Other Peninsular Mountains
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- The Himalayas along with other peninsular mountains are young, weak and flexible in their geological structure unlike the rigid and stable Peninsular Block.
- Consequently, they are still subjected to the interplay of exogenic and endogenic forces, resulting in the development of faults, folds and thrust plains.
- These mountains are tectonic in origin, dissected by fast-flowing rivers which are in their youthful stage.
- gorges, V-shaped valleys, rapids, waterfalls
The approximate length of the Great Himalayan range, also known as the central axial range, is 2,500 km from east to west, and their width varies between 160-400 km from north to south
Bhotia‘s- These are nomadic groups who migrate to Bugyals (the summer grasslands in the higher reaches) during summer months and return to the valleys during winters.
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Indo-Ganga-Brahmaputa Plain
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- The 3rd geological division of India comprises the plains formed by the river Indus, the Ganga and the Brahmaputra
- Originally, it was a geo-synclinal depression which attained its maximum development during the third phase of the Himalayan mountain formation approximately about 64 million years ago.
- Since then, it has been gradually filled by the sediments brought by the Himalayan and Peninsular rivers.
- Average depth- 1,000-2,000m.
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[Image: Geographic Region of India]