Geology 2023 Paper II 50 marks 150 words Compulsory Explain

Q5

Answer the following questions in about 150 words each: (a) Explain the process of manganese nodules formation and give their major occurrences in the world. (10 marks) (b) Describe the formation of replacement textures in ore minerals and give the criterion of their recognition. (10 marks) (c) Explain the Kriging method for estimating ore reserve. (10 marks) (d) Discuss environmental impacts of urbanization and their mitigations with special reference to land and water. (10 marks) (e) How does coordination number depend on the ratio of ionic radii in a crystal? (10 marks)

हिंदी में प्रश्न पढ़ें

निम्नलिखित में से प्रत्येक प्रश्न का उत्तर लगभग 150 शब्दों में दीजिए : (a) मैंगनीज पिंडों के निर्माण की प्रक्रिया की व्याख्या कीजिए और ये विश्व में प्रमुखता से कहाँ-कहाँ पाये जाते हैं, बताइए। (10 अंक) (b) अयस्क खनिजों में प्रतिस्थापन बनावट के निर्माण का वर्णन कीजिए तथा उनकी पहचान के मानक दीजिए। (10 अंक) (c) खनिज भंडार का आकलन करने के लिए क्रिगिंग विधि का वर्णन कीजिए। (10 अंक) (d) भूमि और जल के विशेष संदर्भ में शहरीकरण से पर्यावरण पर पड़ने वाले प्रभावों एवं उनके प्रशमन (मिटिगेशन) पर चर्चा कीजिए। (10 अंक) (e) स्फटिक में समन्वयांक किस प्रकार आयनिक त्रिज्या के अनुपात पर निर्भर करता है? (10 अंक)

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Directive word: Explain

This question asks you to explain. 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

This multi-part question requires explaining five distinct geological concepts in approximately 150 words each. Allocate roughly equal time (~6 minutes) and words (~30) per sub-part since all carry equal marks. For (a), explain hydrogenous/diagenetic formation and cite Clarion-Clipperton Zone; for (b), describe pseudomorphic replacement and residual textures; for (c), outline Kriging's weighted moving average and variogram application; for (d), discuss impervious surfaces, groundwater depletion, and rainwater harvesting; for (e), explain radius ratio rules with critical values (0.155, 0.225, 0.414, 0.732). Use diagrams for (b) and (e) to maximize marks.

Key points expected

  • (a) Manganese nodules: hydrogenous precipitation from seawater, diagenetic remobilization from sediment; nuclei of volcanic debris/fossil fragments; major occurrences in Clarion-Clipperton Zone (Pacific), Indian Ocean nodule fields, Peru Basin
  • (b) Replacement textures: dissolution-precipitation mechanism, volume-for-volume substitution; pseudomorphs, atoll textures, relict cores; recognition criteria: preservation of original crystal outlines, cross-cutting relationships, compositional zoning
  • (c) Kriging method: geostatistical interpolation using weighted moving averages; variogram modeling for spatial correlation; ordinary/simple/universal Kriging variants; advantage of minimizing estimation variance
  • (d) Urbanization impacts: impervious surfaces reducing infiltration, heat island effect, groundwater over-extraction, contamination; mitigations: rainwater harvesting (Chennai model), permeable pavements, SUDS, aquifer recharge
  • (e) Coordination number: radius ratio r⁺/r⁻ determines stable coordination; critical values—3-fold (0.155), 4-fold (0.225), 6-fold (0.414), 8-fold (0.732); geometric packing constraints, Pauling's rules

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Accurately explains all five processes: for (a) distinguishes hydrogenous vs. diagenetic nodule formation; for (b) correctly identifies dissolution-precipitation as replacement mechanism; for (c) precisely defines Kriging as BLUE estimator; for (d) links specific urban processes to land/water impacts; for (e) applies correct radius ratio limits with geometric reasoningDescribes most processes correctly but confuses mechanisms (e.g., conflates hydrogenous with hydrothermal for nodules) or omits key distinctions; Kriging explanation vague; radius ratio values approximateFundamental errors: describes nodules as hydrothermal vents products, misidentifies replacement as magmatic, confuses Kriging with inverse distance weighting, or states incorrect radius ratio critical values
Diagram / cross-section15%7.5Includes labeled diagrams for (b) showing pseudomorph/atoll textures with mineral phases indicated, and for (e) illustrating coordination polyhedra (tetrahedron, octahedron, cube) with ionic radii relationships; diagram for (a) showing nodule structure with concentric layersSimple sketch for one sub-part (typically radius ratio or replacement texture) without proper labeling or incomplete polyhedra; mentions diagrams but doesn't executeNo diagrams despite clear visual components; or diagrams completely unlabeled, misleading, or irrelevant to the processes described
Field evidence20%10Cites specific occurrences: for (a) Clarion-Clipperton Zone, Indian Ocean polymetallic nodule fields; for (b) classic examples like chrysotile after olivine, malachite after azurite; for (d) Indian cities—Chennai groundwater crisis, Bengaluru lake encroachment; for (c) mentions GSI/MECL reserve estimation applicationsGeneral references to 'deep sea' or 'Indian Ocean' without specificity; replacement examples generic; urban impacts described without Indian case studiesNo field locations cited; or incorrect associations (e.g., nodules from Red Sea brines, replacement textures from igneous cumulates only)
Quantitative reasoning20%10For (e), precisely states radius ratio critical values (0.155, 0.225, 0.414, 0.732) with coordination numbers; for (c), explains variogram parameters (nugget, sill, range) mathematically; for (d), cites quantitative data (e.g., Chennai's 40% groundwater depletion, impervious surface percentages)Mentions radius ratio concept without exact values; describes Kriging qualitatively without variogram mathematics; urban impacts described without numerical backingNo quantitative content where clearly required; incorrect radius ratio values; confuses statistical parameters or omits mathematical basis entirely
Indian / economic relevance20%10Highlights India's strategic interest: for (a) India's deep-sea mining license in Central Indian Ocean Basin (CIOB), NIOT's 'Varaha' collector; for (c) GSI/MECL applications for Indian ore deposits; for (d) Smart Cities Mission, AMRUT, Chennai/Bengaluru water management; connects to critical minerals securityBrief mention of Indian Ocean nodules or generic reference to 'Indian urbanization' without specific policies, programs, or institutional involvementNo Indian context; treats all examples as foreign-only (e.g., only Clarion-Clipperton, only Western cities); misses opportunity to demonstrate awareness of India's economic geology priorities

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