UPSC Prelims 2011 Q97: Geography – Indian Physical Geography
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
- (a) uplift of folded Himalayan series
- (b) syntaxis bending of geologically young Himalayas
- (c) geo - tectonic disturbance in the tertiary folded mountain chains
- (d) Both (a) and (b) above
Answer: (b) syntaxis bending of geologically young Himalayas
Explanation
Why the Brahmaputra makes its famous "U" turn
The Brahmaputra, after flowing through Tibet, dramatically changes direction before entering India.
| Option | Verdict | Reason |
|---|---|---|
| (a) Uplift of folded Himalayan series | Incorrect | Uplift alone does not specifically explain the sharp bending pattern; it's part of a broader tectonic process, but not the precise named mechanism |
| (b) Syntaxis bending of geologically young Himalayas | Correct | The Namche Barwa syntaxis — a sharp structural bend in the young, geologically active Himalayan ranges — forces the river into its dramatic "U" turn |
| (c) Geo-tectonic disturbance in tertiary folded mountain chains | Incorrect | This is a vaguer, broader description that doesn't specifically name the real mechanism (syntaxis bending) |
| (d) Both (a) and (b) | Incorrect | Since (b) alone is the precise, correct mechanism, combining it with the vaguer (a) is not the standard answer |
The Brahmaputra's "U" turn:
| Point | Detail |
|---|---|
| Location | Near the Namche Barwa massif, eastern Himalayas |
| Mechanism | Syntaxis bending of the young Himalayan ranges |
| Result | River turns sharply to flow into India (as the Siang/Brahmaputra) |
Answer: (b) syntaxis bending of geologically young Himalayas.
Why each option is right or wrong
- (a) Incorrect. General uplift doesn't specifically capture the sharp bending mechanism involved.
- (b) CORRECT. The syntaxis bend of the young Himalayas (near Namche Barwa) is the precise, documented mechanism behind the river's 'U' turn.
- (c) Incorrect. This is a vaguer description that doesn't name the specific syntaxis mechanism.
- (d) Incorrect. Since (b) alone is the precise correct answer, combining it with the less specific (a) is not standard.
Key point
The Brahmaputra's 'U' turn is caused by SYNTAXIS BENDING of the geologically young Himalayas near the Namche Barwa massif — a specific structural mechanism, not just general uplift.
Remember
Brahmaputra's 'U' turn into India: caused by syntaxis bending of the young Himalayas near Namche Barwa.
Common mistakes
- Picking a vaguer, general tectonic description over the specific named mechanism (syntaxis bending).
- Not knowing the Namche Barwa location as the site of this dramatic river bend.
- Combining a correct and an imprecise option, when only the precise one is the standard answer.
Exam tip
Brahmaputra's famous 'U' turn = syntaxis bending near Namche Barwa, a specific Himalayan structural feature. Prefer the precise mechanism over vague uplift language.
Sources
- NCERT Class XI Geography — India: Physical Environment — Structure and Physiography
- Encyclopaedia Britannica — Brahmaputra River