Q. What are Tsunamis? How and where are they formed? What are their Consequences? Explain with examples.
Possible Introductions
Definition-based intro
Tsunamis are long, high sea waves caused by sudden displacement of a large volume of water, usually triggered by undersea earthquakes, volcanic eruptions, or landslides.
Etymology intro
The word Tsunami comes from Japanese, meaning “harbor waves”, reflecting the devastation these waves cause upon reaching shallow coasts.
Fact-based intro
According to UNESCO-IOC, over 58 tsunamis occurred between 2000–2020, killing more than 250,000 people worldwide, making them one of the deadliest coastal hazards.
Main Body
1. What are Tsunamis?
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- Seismic sea waves generated by sudden displacement of ocean water.
- Wavelengths up to 200 km, speeds of 700–900 km/h, but low amplitude in deep ocean → become destructive only near coasts.
2. How are they Formed?
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- Undersea Earthquakes (subduction zones): Most common cause. Example: 2004 Indian Ocean tsunami (Mw 9.1 earthquake off Sumatra).
- Volcanic Eruptions: Displacement of water due to eruptions/collapses. Example: Krakatoa eruption (1883) in Indonesia.
- Submarine Landslides / Rockfalls: Sudden mass movement underwater. Example: 1958 Lituya Bay mega-tsunami (Alaska).
- Glacial Calving / Meteor Impacts: Rare but possible.
Where? Primarily in tectonically active regions, especially Pacific Ring of Fire, Indian Ocean subduction zones, and Mediterranean seismic zones.
3. Consequences of Tsunamis
(a) Ecological Consequences
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- Coastal ecosystems destroyed: mangroves, coral reefs, estuaries.
- Salinisation of soils & aquifers → loss of agriculture. Example: After 2004 tsunami, paddy fields in Tamil Nadu became saline.
(b) Economic Consequences
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- Loss of infrastructure: ports, roads, fisheries.
- Collapse of tourism industries in island nations (e.g., Maldives, Sri Lanka).
- Rehabilitation costs in billions of dollars.
(c) Social & Human Consequences
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- High fatalities due to lack of early warning.
- Displacement and long-term trauma.
- Spread of epidemics due to contaminated water. Example: 2004 tsunami killed ~2.3 lakh people across 14 countries.
(d) Geopolitical Consequences
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- International humanitarian responses (2004 led to creation of Indian Ocean Tsunami Warning System, 2006).
- Climate migrants in Pacific islands due to recurrent tidal hazards.
Diagram (Text Suggestion)
Flowchart: Trigger (Earthquake/Volcano) → Water displacement → Wave propagation → Amplification near coast → Destruction.
Map: Mark tsunami-prone regions (Pacific Ring of Fire, Andaman-Sumatra trench, Japan coasts).
Possible Conclusions
Balanced
Tsunamis are natural hazards with devastating consequences, but their impact can be minimized through early warning systems, coastal planning, and community preparedness.
Policy-linked
India’s establishment of the Indian National Centre for Ocean Information Services (INCOIS), Hyderabad has strengthened tsunami warning and reduced vulnerability.
Forward-looking
With climate change intensifying coastal risks, integrated coastal zone management, ecosystem restoration (mangroves as bio-shields), and international cooperation are vital for resilience.
