BharatNotes Tsunami
noun (plural tsunamis or tsunami)Usage in a UPSC answer
In the aftermath of the 2004 Indian Ocean tsunami, India institutionalised a dedicated early-warning system under INCOIS, recognising that disaster management must shift from reactive relief to anticipatory, technology-driven preparedness.
Synonyms
Antonyms
Word Family
tsunamis (n pl), mega-tsunami (n), paleo-tsunami (n), tsunamigenic (adj)
Root
Japanese tsu (津) = harbour; nami (波) = wave; compound tsunami (津波) = harbour wave; entered English 1890s
Etymology
Borrowed from Japanese tsunami (津波), from tsu (津, "harbour") + nami (波, "wave"), literally "harbour wave"; the term entered English in the 1890s, with the earliest recorded usage in 1896.
Memory Hook
Break it as "tsu-nami" = the Japanese "harbour (tsu) wave (nami)" — picture a giant wave swallowing a harbour, the very scene the word was coined to describe.
How This Word Works in UPSC Writing
A series of very long waves generated by the sudden displacement of a water column, usually by a submarine earthquake. The physics explains why it is so dangerous. Because its wavelength runs to hundreds of kilometres, far exceeding even the deepest ocean, a tsunami behaves as a shallow-water wave everywhere, so its speed depends on depth alone and reaches the speed of a jet aircraft in the open sea. There its height may be under a metre and a ship will not notice it passing. As it nears the coast the depth falls, the wave slows, and the energy compresses into a shorter and far taller wave. This is precisely why warning systems rely on deep-ocean pressure sensors rather than coastal observation, and why an unusual withdrawal of the sea, the arriving trough, is a warning to move inland. India established the Indian Tsunami Early Warning Centre at INCOIS, Hyderabad, after the disaster of 26-Dec-2004.
Don’t Confuse It With
A tsunami is generated by displacement of the water column through a submarine earthquake, landslide or volcanic eruption. Tidal wave is a misnomer for it, since tides arise from gravitational attraction and have nothing to do with it. A storm surge is driven by cyclonic wind and low pressure, so it is meteorological rather than seismic in origin. A seiche is a standing oscillation in an enclosed water body. Run-up is the height above sea level the water reaches inland, and it is run-up rather than offshore wave height that determines the damage.
Hindi Meaning
सुनामी; ज्वारीय लहर is the popular but inaccurate rendering.
Common Questions
- Why is a tsunami barely noticeable in the open ocean?
- In deep water its energy is spread through a wavelength of hundreds of kilometres, so its height is very small; the wave only rises steeply as it slows in shallow coastal water.
- What is the difference between a tsunami and a storm surge?
- A tsunami is caused by the seismic displacement of water, while a storm surge is the wind and low-pressure driven rise of sea level accompanying a cyclone.
Seen in UPSC Question Papers
- Prelims 2015 — Disaster Management
- Mains 2017 · GS3 · 15 marks — Disaster Management
Real UPSC previous-year questions whose text uses “Tsunami” — proof this word earns its place on your list.
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