UPSC Prelims 2001 Q49: Geography – Indian Physical Geography
- (a) 370 million years
- (b) 470 million years
- (c) 570 million years
- (d) 670 million years
Answer: (a) 370 million years
Explanation
Approximate age of the Aravalli Range
| Point | Detail |
|---|---|
| Circulated key | 370 million years |
| What modern dating says | Aravalli rocks and folding are Proterozoic — roughly 1,500 to 2,500 million years |
| Type of mountain | Old fold mountains, now worn down to residual hills |
| Highest point | Guru Shikhar, Mount Abu (1,722 m) |
The Aravallis are among the oldest fold mountains in the world. The key given for this paper is 370 million years, but geologists date the Aravalli and Delhi fold belts to the Proterozoic, well over 1,500 million years ago, so in truth every option is far too young. Among the options, the key marks (a); one third-party key gives (d) 670 million years. In an exam, the safe point is that the Aravallis are the oldest mountains of India.
Answer: (a) 370 million years.
Why each option is right or wrong
- (a) CORRECT. This is the circulated key, though modern dating makes the range much older.
- (b) Incorrect. 470 million years is not the key's figure.
- (c) Incorrect. 570 million years is not the key's figure.
- (d) Incorrect. 670 million years is given by some third-party keys, not the circulated key.
Key point
Aravallis: Gujarat to Delhi, about 700 km; Delhi Ridge is their northern end; Banas, Luni and Sabarmati rise in them.
Remember
Aravallis: India's oldest fold mountains (Proterozoic); key says 370 million years.
Common mistakes
- Thinking the Aravallis are younger than the Himalaya.
- Treating the key's figure as settled geology.
- Mixing up the Aravallis with the Vindhyas (sedimentary, not folded).
Exam tip
Where all options conflict with modern science, note the key and learn the real fact.
Sources
- NCERT Class XI — India: Physical Environment, chapter 'Structure and Physiography' (the Aravalli Range)
- Geological Survey of India — Geology and Mineral Resources of Rajasthan (Miscellaneous Publication 30, Part 12)