India: relief, rivers & drainage

Answer: (a) Bengaluru

Bengaluru lies at about 77.6 degrees east, only about 0.4 degrees from Delhi at 77.2 degrees east, so it is the closest in longitude. Hyderabad, Nagpur and Pune lie further east or west of that line.

• ✓ (a) Delhi is at 77.20 E and Bengaluru at 77.58 E, a gap of about 0.4 degrees. Bengaluru is almost directly south of Delhi.
• ✗ (b) Hyderabad is at 78.47 E, about 1.3 degrees east of Delhi.
• ✗ (c) Nagpur is at 79.12 E, about 1.9 degrees east of Delhi.
• ✗ (d) Pune is at 73.85 E, about 3.4 degrees west of Delhi, the farthest of the four.

Remember · Delhi (77.2 E) and Bengaluru (77.6 E) are almost on the same meridian; Pune (73.9 E) is well to the west.

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) Kodaikanal (Tamil Nadu)

Kodaikanal Lake is the artificial one: it is a star-shaped lake dug in 1863 in the hill town of Kodaikanal, Tamil Nadu. Kolleru and Renuka are described as natural in their Ramsar information sheets, and the district administration lists Nainital's Naini Lake under natural scenic beauty, with no source calling it man-made.

• ✓ (a) Tamil Nadu Tourism describes it as a star-shaped artificial lake, built in 1863 under the Collector of Madurai, Sir Vere Henry Levinge.
• ✗ (b) The Ramsar information sheet calls Kolleru a natural eutrophic lake between the Godavari and Krishna river basins, working as a natural flood-balancing reservoir.
• ✗ (c) The Nainital district administration lists Naini Lake under 'Natural / Scenic beauty' and notes that the Skanda Purana already refers to Nainital as Tri-Rishi-Sarovar; none of the sources describes it as built. Since Kodaikanal is the artificial lake, this option does not fit.
• ✗ (d) The Ramsar information sheet describes Renuka as a natural wetland in the Western Himalayas that has survived natural calamities and tectonic upheavals.

Remember · Kodaikanal Lake (TN) is man-made (1863); Kolleru and Renuka are natural wetlands (Ramsar sheets), and Naini Lake is listed as natural scenic beauty.

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (b) 2 and 3 only

Heavy sand mining harms groundwater in two ways: it can pollute it and it can pull the water-table down. It does not lower river salinity; near the coast it makes salt-water intrusion more likely.

• ✗ 1. Removing sand deepens the channel and weakens natural barriers, so salt water can enter aquifers; UNEP lists 'salination of aquifers' as a result of sand extraction. Salinity goes up, not down.
• ✓ 2. The sand layer filters water that seeps into the ground. The MoEFCC guidelines say mining can pollute groundwater by thinning this filter material, especially over recharge fissures.
• ✓ 3. Mining lowers the riverbed and river level, and groundwater in the adjoining flood plain drains towards it, so the water-table falls. The guidelines record this as a listed effect.

Remember · Heavy riverbed sand mining lowers the water-table, weakens the sand filter that protects groundwater, and raises salt intrusion risk near the coast.

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) 1 only

Only statement 1 is correct: Barren Island, in the Andaman Sea, is India's only active volcano. It lies north-east of Port Blair, not east of Great Nicobar, and it has erupted again after 1991, most recently in 2017 as of the exam.

• ✓ 1. NCERT calls Barren Island, in the Andaman and Nicobar Islands, the only active volcano in India.
• ✗ 2. The island is about 138 km north-east of Port Blair (now Sri Vijaya Puram), the capital of the Andaman and Nicobar Islands. Great Nicobar is at the far southern end of the island chain, much farther away.
• ✗ 3. The volcano did not stay quiet after 1991; the Ministry of Tourism's page says it last erupted in 2017.

Remember · Barren Island, about 138 km north-east of Port Blair, is India's only active volcano and has erupted as recently as 2017.

📘 Read it in NCERT: Class 11 India: Physical Environment, Ch 2 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error