UPSC Mains 2025 GS1 Q14: model answer
Give a geographical explanation of the distribution of off-shore oil reserves of the world. How are they different from the on-shore occurrences of oil reserves ?
What the question wants
Explain why offshore oil occurs where it does (sedimentary basins on continental margins), name the main regions, then compare with onshore deposits.
How to structure it
Intro: oil formation. Body: geological controls; regions; comparison table of offshore vs onshore. Conclusion.
- 1Geological controls
- 2Regions
- 3Comparison table of offshore vs onshore
Model answer
Petroleum forms from marine organic matter buried in sedimentary rocks, cooked over millions of years, then trapped by impermeable layers in anticlines, faults or salt domes.
| Basis | Offshore | Onshore |
|---|---|---|
| Setting | Continental shelves, passive margins, deltas | Interior sedimentary basins, old seas |
| Examples | North Sea, Gulf of Mexico, Mumbai High, KG basin | Ghawar (Saudi), Texas, Assam, Barmer |
| Cost and risk | High: platforms, deep water, spills | Lower; easier access |
| Law | UNCLOS EEZ and shelf rights | National land law |
Why offshore reserves are where they are
- Continental shelves and passive margins: thick sediments from rivers built up over time (Gulf of Mexico from the Mississippi, Niger Delta).
- Rift basins and old seas: North Sea, Persian Gulf.
- Salt tectonics: pre-salt reservoirs off Brazil (Santos basin) and West Africa, formed when the Atlantic opened.
- India: Mumbai High on the western shelf; Krishna–Godavari basin on the east coast.
Main regions: Persian Gulf, Gulf of Mexico, North Sea, Gulf of Guinea, Brazil, Caspian, South China Sea, Arctic shelf (emerging).
Offshore vs onshore
- Setting: offshore on continental margins under water; onshore in interior basins and old seas now land (Arabian Peninsula, Texas, Assam, Barmer).
- Depth and cost: offshore needs platforms and deep-water rigs, so costs and risks are higher.
- Environmental risk: spills spread fast (Deepwater Horizon, 2010).
- Ownership: offshore rights follow UNCLOS EEZ and shelf rules and can create disputes (South China Sea).
- Age of fields: many onshore fields are mature; new discoveries are mostly offshore and deep water.
Geology decides where oil is; technology and law decide what is worth extracting.
Keywords, cases and data to drop in
sedimentary basins continental shelf salt domes pre-salt Brazil Mumbai High KG basin UNCLOS EEZ Deepwater Horizon
Where most answers lose marks
- Listing regions without explaining the geology.
- Skipping the second part on onshore differences.
- Treating offshore oil as formed differently from onshore oil (formation is the same; setting differs).
Fresh examples from current affairs
Domestic Tourism Expenditure Survey 2025-26: pilgrimage tops overnight trips
MoSPI released the Domestic Tourism Expenditure Survey, July 2025 to June 2026, on 23 September 2026. Pilgrimage and religious travel made up 48% of overnight trips over the last 365 days. Uttar Pradesh had the highest share of visitor-trips, 15.7%. Business trips had the highest average spend per trip, Rs. 5,949.
UPSC angle: Prelims: which agency runs DTES (NSO, MoSPI).
23 Sep 2026
56 critical and strategic mineral blocks auctioned so far
The Mines Ministry said on 23 June 2026 that recent auctions took critical and strategic mineral blocks successfully auctioned by the Centre to 56 out of 88 unique blocks (over 63%). The Seventh Tranche auctioned 10 blocks, a first for Gujarat, Uttarakhand and Telangana. Exploration Licence blocks auctioned reached 11, newly covering Arunachal Pradesh, Uttar Pradesh and Odisha.
UPSC angle: Prelims: critical minerals list, auction powers.
23 Jun 2026
India–UK Critical Minerals Global Supply Chain Observatory launched
India's Mines Minister and the UK Foreign Secretary launched the India–UK Critical Minerals Global Supply Chain Observatory in New Delhi on 4 June 2026. Built by TEXMiN, IIT (ISM) Dhanbad and the University of Cambridge, it is a data platform to monitor global critical mineral supply chains and flag risks. It supports the National Critical Mineral Mission.
UPSC angle: Prelims: critical minerals partnerships.
4 Jun 2026
Coal production starts at Urtan and Dhirauli mines in MP
Coal production began at Urtan (Anuppur, MP) on 15 May 2026 and Dhirauli (Singrauli, MP) on 17 May 2026. Urtan (JMS Mining) is the first underground mine to start under commercial coal auctions. Dhirauli is allocated to Mahan Energen Limited. The Ministry frames both as boosts to domestic coal supply.
UPSC angle: Prelims: coalfields of MP.
19 May 2026Learn the concept
Question text as printed in the official UPSC question paper: https://www.upsc.gov.in/sites/default/files/GENERAL-STUDIES-PAPER%20I-QP-CSM-25-010925.pdf The model answer is original Battle IAS work; use it to learn structure, not to memorise.