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UPSC 2018 GS-I · 10 marks · 150 words

Define mantle plume and explain its role in plate tectonics.

What “Explain” demands

set out how or why something works, with the mechanism made explicit.

The characteristic failure: stating that it works without showing how.

What a top answer must contain

These are the checkable specifics from the marking standard for this question — the actual case, committee, datum or thinker, not an instruction to “give examples”.

  • Definition: a narrow upwelling column of abnormally hot rock rising from the core-mantle boundary, largely independent of plate motion
  • Hotspots and tracks: Hawaii-Emperor chain and its bend, Reunion plume and the Deccan Traps, Iceland on a ridge
  • Role: intraplate volcanism plate tectonics alone cannot explain; large igneous provinces; possible plume-driven continental rifting
  • Indian relevance: Reunion hotspot and Deccan volcanism at the K-Pg boundary; Laccadive-Chagos ridge as the track
  • Scientific caution a strong answer adds: plume hypothesis (Morgan 1971) is contested; some argue shallow-mantle explanations

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