What are Tsunamis? How and where are they formed? What are their consequences? Explain with examples.
Approach · directive: “what / how / explain”
What it asks · Define tsunamis, explain their causes and the regions where they occur, and describe their effects, with examples.
The question has 3 parts — answer each
- Define tsunamis
- Explain how they are formed (causes and mechanism) and where (regions)
- Explain their consequences, with examples
Open with · A tsunami is a series of very long-wavelength sea waves caused by the sudden displacement of a large volume of water; small in the open ocean, it rises to great heights near the coast.
Cover
- Causes: undersea megathrust earthquakes that lift the sea floor; submarine landslides; volcanic eruptions (Krakatoa 1883, Hunga Tonga 2022); rarely, meteorite impacts.
- Mechanism: waves travel at jet-like speed in deep water; as depth falls near shore they slow and pile up (shoaling).
- Where: mostly the Pacific Ring of Fire; the Sunda trench and Makran subduction zone threaten the Indian Ocean and Arabian Sea.
- Examples: 2004 Indian Ocean tsunami (Sumatra–Andaman earthquake) hit Tamil Nadu and the Andamans; 2011 Tohoku tsunami triggered the Fukushima nuclear accident.
- Consequences: deaths and displacement, salinised farmland and aquifers, destroyed boats and fishing livelihoods, damaged mangroves and reefs, altered coastlines.
- Response: early warning, evacuation drills, coastal shelterbelts and mangroves; UNESCO-IOC 'Tsunami Ready' communities.
Close with · Tsunamis cannot be prevented, but losses can — through early warning, community preparedness and nature-based coastal defences.
Add value (verified)
- India's Tsunami Early Warning Centre at INCOIS, Hyderabad, set up after the 2004 tsunami, has been operational since 15 October 2007. PARLIAMENT QUESTION: Performance of early warning systems — PIB (Ministry of Earth Sciences), 12 Feb 2026 ↗“Operational since 15 October 2007, the centre uses advanced real-time seismic and sea level monitoring, computing and communication systems to detect tsunamigenic earthquakes within 10 minutes and issues tsunami advisories as per SOPs.”
Question: UPSC's CS (Main) 2025, GS Paper I — paper ↗. Approach: Minimalist IAS, checked 30 Sept 2026 (how we verify) — UPSC publishes no model answers. ·
Model answer · 220 words (UPSC limit 150) · Minimalist IAS
A tsunami is a series of very long-wavelength sea waves generated when a large volume of water is suddenly displaced; barely noticeable in the open ocean, it rears up to great heights on reaching the shore.
How they form
- Chief cause: undersea megathrust earthquakes at subduction zones that abruptly lift or drop the sea floor — the 2004 Sumatra–Andaman and 2011 Tohoku earthquakes.
- Other triggers: submarine landslides, volcanic eruptions (Krakatoa 1883, Hunga Tonga 2022) and, rarely, meteorite impacts.
- Mechanism: in deep water the waves race at jet-aircraft speed with low height; as depth falls near the coast they slow, bunch up and grow (shoaling).
Where
- Mainly the Pacific Ring of Fire; in the Indian Ocean, the Sunda trench threatens India's east coast and the Makran subduction zone its west coast.
Consequences
- Human: mass deaths and displacement — the 2004 tsunami devastated Tamil Nadu and the Andaman and Nicobar Islands.
- Economic and environmental: boats, ports and fishing livelihoods destroyed; farmland and aquifers salinised; mangroves, reefs and coastlines altered.
- Cascading hazards: the 2011 Tohoku tsunami triggered the Fukushima nuclear accident.
Reducing losses
- INCOIS's Tsunami Early Warning Centre, operational since 2007, detects tsunamigenic quakes within minutes; evacuation drills, shelterbelts and mangroves; UNESCO-IOC 'Tsunami Ready' communities.
Tsunamis cannot be prevented, but their toll can — through early warning, prepared communities and nature-based coastal defence.
Written by Minimalist IAS from facts checked at source (how we verify) — a little fuller than exam length, so every part of the question is covered; in the hall, keep the structure and trim the detail. UPSC publishes no model answers: compare your structure and coverage with this, then write your own.