Question

The Brahmaputra, Irrawady and Mekong rivers originate in Tibet and flow through narrow and parallel mountain ranges in their upper reaches. Of these rivers, Brahmaputra makes a "U" turn in its course to flow into India. This "U" turn is due to
1. Uplift of folded Himalayan series
2. Syntaxial bending of geologically young Himalayas
3. Geo-tectonic disturbance in the tertiary folded mountain chains
4. Both (a) and (b) above

Answer 1

Correct Answer - Option 2 : Syntaxial bending of geologically young Himalayas

The correct answer is Option 2.

• Brahmaputra river originates under the name of Siang or Dihang, from the Chemayungdung glacier of the Kailash range near the Mansarovar lake.
• It enters India west of Sadiya town in Arunachal Pradesh.
• Tributaries: Dibang, Lohit, Siang, Burhi Dihing, Tista, and Dhansari
• The Brahmaputra Valley has an average width of about 80 Km.
• The main river of the valley, Brahmaputra is one of the largest rivers in the world and rank fifth with respect to its average discharge.
• Namcha Barwa is a mountain peak in Tibetian Himalaya with a height of 7757 meters.
• The Tsangpo - Brahmaputra river takes a U-turn on reaching the Namcha Barwa and enters India in Arunachal Pradesh through a gorge.
• The Himalayas extend in the east-west direction from the Indus gorge in the west to the Brahmaputra gorge in the east.
• The gently arching ranges of the Himalayan mountains on their Western and Eastern extremities are sharply bent southward in deep Knee-bend flexures that are called syntaxial bends.
• The western syntaxial bend occurs near the Nanga Parbat and the eastern syntaxial bend occurs near the Namche Barwa.
• This is also one of the reasons for the U-turn of the Brahmaputra. Hence, statement 2 is correct.