GS1 2018 Q6 10 marks 150 words Physical Geography

UPSC Mains 2018 GS1 Q6 — Physical Geography

Define mantle plume and explain its role in plate tectonics. (Answer in 150 words)

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Question Decoded — examiner's intent

Directive verbs
Defineexplain
Scope keywords
mantle plumeroleplate tectonics
Implicit sub-parts
  • Origin and mechanism of a mantle plume (thermal buoyancy)
  • Relationship between plumes and plate driving forces (Slab pull vs. Ridge push vs. Plumes)
  • Impact on lithospheric breakup (Rifting) and hotspots
  • Contrast between plume-related tectonics and standard subduction-cycle tectonics
Common pitfalls
  • Confusing mantle plumes with simple convection cells
  • Focusing only on volcanic hotspots (Hawaii/Reunion) without linking it to 'Plate Tectonics' (motion/breakup)
  • Neglecting to mention the Core-Mantle Boundary (CMB) as the source
  • Failing to draw a diagram illustrating the mushroom head and narrow tail
Dimensions required
GeophysicalGeomorphologicalTectonicCartographic (Diagrammatic)
Marks allocation hint

Allocate 3 marks for a precise definition including the CMB and thermal buoyancy. Spend the remaining 7 marks (approx. 100 words) on the 'role' by detailing rifting, supercontinent cycles, and hotspots, ensuring a labeled diagram is included to save on word count.

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