Geology 2022 Paper I 50 marks Discuss

Q2

(a) Discuss in detail the notion of 'continental drift' and the theories of plate tectonics as they relate to palaeogeography. (20 marks) (b) Explain the principles of aerial photography and how it is classified. (15 marks) (c) Illustrate and describe the linear structures of deformed rocks. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) 'महाद्वीपीय विस्थापन' की अवधारणा तथा प्लेट विवर्तनिकी के सिद्धांतों की पुराभौगोलिक संबंधों के संदर्भ में विस्तार से चर्चा कीजिए। (20 अंक) (b) वायव फोटोग्राफी के सिद्धांतों की व्याख्या करते हुए इसके वर्गीकरण पर प्रकाश डालिए। (15 अंक) (c) विक्षिप्त शैलों की रेखीय संरचना का सचित्र वर्णन कीजिए। (15 अंक)

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Directive word: Discuss

This question asks you to discuss. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

See our UPSC directive words guide for a full breakdown of how to respond to each command word.

How this answer will be evaluated

Approach

The directive 'discuss' for part (a) demands a critical, multi-faceted examination with evidence, while parts (b) and (c) require 'explain' and 'illustrate' respectively. Allocate approximately 40% of time/words to part (a) given its 20 marks, covering Wegener's continental drift, seafloor spreading, and palaeogeographic reconstructions; 30% each to part (b) on aerial photography principles/classification and part (c) on linear structures with diagrams. Structure: brief introduction linking all three to structural geology and remote sensing → systematic treatment of each sub-part with diagrams → conclusion on integrated applications in mineral exploration and tectonic studies.

Key points expected

  • Part (a): Wegener's continental drift evidence (jigsaw fit, fossil correlation, palaeoclimatic indicators); mantle convection and slab pull as driving mechanisms; Wilson cycle and supercontinent cycles (Rodinia, Gondwana, Pangea); palaeomagnetic evidence from Indian Deccan Traps and Apparent Polar Wander Paths
  • Part (a): Critical evaluation of plate tectonic boundaries (divergent, convergent, transform) with Indian examples: Himalaya collision zone, Indo-Australian plate boundary, Andaman-Nicobar subduction
  • Part (b): Principles: stereoscopic vision, parallax, scale and resolution, overlap requirements; classification by platform (terrestrial, aerial, space), by tilt (vertical, oblique), by film/sensor (panchromatic, infrared, false colour), and by scale (large, medium, small)
  • Part (b): Applications in India: GSI's aerial surveys for mineral targeting, Landsat/IRS satellite data for lineament mapping in Dharwar craton, Bhuvan portal integration
  • Part (c): Linear structures: primary (bedding, flow cleavage) versus secondary (fold axes, intersection lineations, mineral lineations, mullions, boudin axes); tectonic significance as strain markers and kinematic indicators
  • Part (c): Indian field examples: E-W trending lineaments in Singhbhum shear zone, N-S trending Aravalli fold belt lineations, Kerala khondalite belt mineral lineations indicating transport direction

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Demonstrates precise understanding of plate tectonic mechanisms (slab pull vs ridge push), correctly distinguishes between true continental drift and modern plate tectonics, accurately defines aerial photography parameters (focal length, flying height relationships), and correctly classifies linear structures by origin (tectonic vs sedimentary) with proper use of structural geology terminologyShows basic familiarity with continental drift and plate tectonics but conflates mechanisms or omits key differences; describes aerial photography generally without technical precision; lists linear structures without clear genetic classification or confuses lineation typesFundamental misconceptions: treats continental drift and plate tectonics as identical, confuses aerial photography with photogeology/remote sensing without distinction, or misidentifies linear structures as planar structures; significant terminological errors
Diagram / cross-section25%12.5Provides at least 4 high-quality diagrams: for (a) a labelled cross-section of Himalayan collision zone showing suture zones and plate vectors, plus a Pangea reconstruction map; for (b) a stereoscopic pair diagram showing parallax geometry; for (c) block diagrams showing intersection lineations on fold limbs and stereonet projections of lineation measurements; all properly labelled with scale and orientationIncludes 2-3 diagrams with basic labelling; may show a generic plate boundary or simple fold-lineation sketch without specific Indian examples; stereoscopic geometry poorly explained; missing stereonet or block diagram for part (c)Single diagram or none; poorly executed sketches without labels; diagrams contradict text description; missing essential illustrations for parts (b) and (c) where visual explanation is critical
Field evidence20%10Cites specific Indian geological evidence: for (a) matching of Permian Gondwana flora between India and Antarctica, Seychelles-India rift evidence, Deccan plume track; for (b) specific GSI aerial survey campaigns (e.g., Hutti-Maski gold belt); for (c) documented lineation measurements from Singhbhum shear zone or Aravalli-Delhi fold belt with reference to published GSI memoirsMentions general field evidence without specific Indian localities; references 'Himalayan collision' or 'Dharwar craton' without precise structural details; no citation of actual survey data or published measurementsNo field evidence cited; relies entirely on theoretical description; or invents non-existent field examples; confuses global examples with Indian geology
Quantitative reasoning15%7.5Includes quantitative elements: plate velocities (cm/year ranges for Indian plate motion), aerial photography scale calculations (1:50,000 vs 1:10,000 implications), stereoscopic parallax formulas, or lineation orientation data with trend/plunge measurements; references radiometric dating constraints for Gondwana breakup (ca. 130 Ma for India-Madagascar separation)Mentions quantitative concepts qualitatively (e.g., 'fast-moving Indian plate') without numerical values; aware that scale affects resolution but no calculations; acknowledges dating but no specific agesNo quantitative treatment; avoids all numerical aspects of the question; or provides incorrect/implausible figures without units
Indian / economic relevance15%7.5Explicitly connects to Indian economic geology: plate tectonics controls on Himalayan metallogeny (Cu-Au porphyries), Malani igneous suite rift-related mineralization; aerial photography applications in GSI's mineral exploration targeting (kimberlite pipes, base metals); linear structure mapping for groundwater (fracture aquifers in hard rock terrain) and hydrocarbon traps (Cambay basin fault trends)Brief mention of Indian applications without economic linkage; notes GSI uses aerial photography but not for what purpose; mentions lineaments control mineralization without specific commodity examplesNo Indian context; treats question as purely academic with no reference to GSI, Indian stratigraphy, or domestic economic applications; or provides irrelevant foreign examples exclusively

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