UPSC Prelims 2011 · Question 37 of 100
UPSC Prelims 2011 question on Brahmaputra U Turn Syntaxial Bend
- ExamUPSC CSE
- Year2011
- PaperGeneral Studies Paper I
- SubjectGeography
- TopicGeomorphology
- DifficultyMedium
- TypeDirect
The Brahmaputra, Irrawaddy 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
Show answer
Answer: B. Syntaxis bending of geologically young Himalayas
Verdict
Correct Answer: Syntaxial bending of geologically young Himalayas
Analysis
The sharp “U-turn” of the Brahmaputra around Namcha Barwa is due to the syntaxial bending of the geologically young Himalayas.
The Himalayas are young fold mountains formed due to the collision of the Indian Plate with the Eurasian Plate. At both ends, the Himalayan ranges take sharp bends, known as syntaxial bends.
The eastern syntaxial bend occurs near Namcha Barwa, where the Brahmaputra, known as the Tsangpo in Tibet, takes a sharp turn and enters India as the Siang or Dihang in Arunachal Pradesh.
This bend is not simply due to uplift. Uplift explains the rise of the Himalayas, but syntaxial bending explains the sharp horizontal turn of the mountain ranges and the river course.
Extra UPSC info
The western syntaxial bend is near Nanga Parbat.
The eastern syntaxial bend is near Namcha Barwa.
The Brahmaputra is an antecedent river, meaning it existed before the Himalayas were fully uplifted.
It cuts deep gorges through the Himalayas, including the Yarlung Tsangpo Grand Canyon.
In Tibet, it is called Tsangpo; in Arunachal Pradesh, Siang/Dihang; in Assam, Brahmaputra; and in Bangladesh, Jamuna.
How to crack it
The Brahmaputra’s sharp U-turn near Namcha Barwa is best explained by the syntaxial bending of the young Himalayan ranges, not merely by uplift or general tectonic disturbance.