Geology 2021 Paper I 50 marks 150 words Compulsory Explain

Q1

Answer the following questions in about 150 words each: (a) Explain what is ring of fire? How many plates and geographic areas are associated with ring of fire? (10 marks) (b) What is Geographic Information System (GIS)? Explain the concepts, components and functions of GIS. (10 marks) (c) Discuss stereoscopy and its advantages in aerial photo interpretation. Add a note on elements of photo interpretation. (10 marks) (d) What is stereographic projection in structural geology? Discuss its types, nomenclature and different types of geological plotting technique in a stereonet. (10 marks) (e) Discuss stress and strain ellipsoids using neat diagrams. (10 marks)

हिंदी में प्रश्न पढ़ें

निम्नलिखित में से प्रत्येक प्रश्न का लगभग 150 शब्दों में उत्तर लिखिए : (a) अग्नि वलय (रिंग ऑफ फायर) क्या है, व्याख्या कीजिए । अग्नि वलय के साथ कितनी स्थलमंडलीय प्लेटें और भौगोलिक क्षेत्र संबद्ध हैं ? (10 अंक) (b) भौगोलिक सूचना तंत्र (जी. आई. एस.) क्या है ? भौगोलिक सूचना तंत्र की संकल्पना, घटक तथा कार्यों का वर्णन करें । (10 अंक) (c) त्रिविम (स्टीरियोस्कोपी) और उसकी वायव फोटो व्याख्या की उपयोगिता पर चर्चा करें । फोटो व्याख्या (फोटो इंटरप्रिटेशन) के तत्वों पर एक टिप्पणी कीजिए । (10 अंक) (d) संरचनात्मक भूविज्ञान में त्रिविम प्रक्षेपण क्या है ? इनके प्रकार नामपद्धति और विभिन्न प्रकार की भूवैज्ञानिक आलेखन तकनीक (प्लॉटिंग टैक्निक) की एक त्रिविमजाल (स्टीरियोनेट) में चर्चा कीजिए । (10 अंक) (e) स्वच्छ आरेखों का उपयोग करके प्रतिबल और तनाव दीर्घवृत्ताभों पर चर्चा कीजिए । (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 concise, structured responses of ~150 words each. Begin with (a) Ring of Fire—define it as a circum-Pacific belt of volcanoes and earthquakes, mention ~7 major plates (Pacific, Nazca, Cocos, Juan de Fuca, North American, Eurasian, Indo-Australian) and key geographic areas (Andes, Central America, Mexico, western USA, Aleutians, Japan, Philippines, Indonesia, New Zealand). For (b) GIS, define it as a computer-based system for capturing, storing, analyzing and displaying spatial data; cover components (hardware, software, data, people, methods) and functions (data input, management, analysis, output). For (c) stereoscopy, explain binocular vision for 3D perception, advantages (height measurement, terrain visualization, feature identification), and elements of photo interpretation (tone, texture, shape, size, pattern, shadow, site, association). For (d) stereographic projection, define it as representing 3D orientations on a 2D plane; cover types (equal-angle Wulff net vs. equal-area Schmidt net), nomenclature (primitive, great circles, small circles, poles), and plotting techniques (β-diagram, π-diagram, contouring). For (e) stress and strain ellipsoids, define stress ellipsoid (three principal stresses σ1>σ2>σ3) and strain ellipsoid (X≥Y≥Z axes), with neat labeled diagrams showing prolate/oblate forms. Allocate ~3 minutes per part with 30-35 words per minute.

Key points expected

  • (a) Ring of Fire: Definition as Pacific seismic-volcanic belt; ~7 plates involved; geographic extent from Chile to Alaska to SE Asia
  • (b) GIS: Definition as spatial data management system; five components (hardware, software, data, people, methods); core functions (capture, storage, query, analysis, visualization)
  • (c) Stereoscopy: Principle of binocular parallax for 3D vision; advantages in photo interpretation (relief perception, height estimation, feature discrimination); eight elements of interpretation (tone, texture, shape, size, pattern, shadow, site, association)
  • (d) Stereographic projection: Definition as lower hemisphere projection onto horizontal plane; Wulff (equal-angle) vs. Schmidt (equal-area) nets; nomenclature (primitive circle, great circles, small circles, poles, pi-points); plotting methods (great circle, pole, β-diagram for lineations, π-diagram for foliations, density contouring)
  • (e) Stress and strain ellipsoids: Stress ellipsoid with σ1, σ2, σ3 principal axes; strain ellipsoid with X, Y, Z axes (maximum, intermediate, minimum strain); prolate (cigar) vs. oblate (pancake) shapes; relationship to deformation regimes

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Precise definitions across all parts: Ring of Fire correctly identified as subduction-driven Pacific belt (not just volcanoes); GIS distinguished from simple cartography; stereoscopy explained via parallax principle; stereographic projection correctly as lower hemisphere projection (not arbitrary section); stress/strain ellipsoids with correct principal axis relationships and deformation symmetryGenerally correct definitions with minor errors—e.g., Ring of Fire described vaguely as 'volcanic area,' GIS conflated with GPS, stereoscopy as merely '3D viewing,' stereonet as 'geological graph,' ellipsoids mentioned without principal axis hierarchyFundamental conceptual errors: Ring of Fire attributed to hotspots or rifting; GIS defined as 'geographical information'; stereoscopy confused with spectrometry; stereonet described as map projection; stress and strain used interchangeably without distinction
Diagram / cross-section20%10For (a): neat Pacific-centered sketch showing plate boundaries and volcanic arcs; for (d): correctly drawn lower hemisphere stereonet with primitive circle, great circles, small circles, and plotted structural data; for (e): labeled 3D stress ellipsoid (σ1≥σ2≥σ3) and strain ellipsoid (X≥Y≥Z) with prolate/oblate variants; diagrams integrated with textBasic sketches present but incomplete—Ring of Fire as rough circle without plate labels; stereonet as simple circle without grid; ellipsoids as 2D ellipses without 3D perspective or principal axis labels; diagrams mentioned but not executedMissing or incorrect diagrams; stereonet drawn as upper hemisphere or arbitrary circle; ellipsoids confused with Mohr circles; no visual representation despite 'neat diagrams' instruction in (e); diagrams contradict textual explanation
Field evidence15%7.5Specific field applications: for (a) cites Andean-type margins vs. Mariana-type arcs; for (c) mentions actual aerial photo scales (1:50,000, 1:25,000) and terrain correlation; for (d) references field measurement techniques (compass-clinometer data reduction); for (e) connects ellipsoids to natural strain markers (deformed pebbles, reduction spots, boudinage)Generic field references without specificity—'field geologists use these tools' or 'structures can be measured'; mentions that aerial photos are used in mapping without scale or technique details; strain markers mentioned without examplesNo field connection; purely theoretical treatment; confuses remote sensing with field observation; stereonet presented as abstract exercise without geological application; stress-strain as classroom physics without rock deformation context
Quantitative reasoning20%10Numerical precision where applicable: for (a) ~40,000 km circumference, 75% of world's volcanoes, 90% of earthquakes; for (b) mention of raster/vector data resolution, coordinate systems (UTM, lat-long); for (c) parallax formula (h=H·d/p) or mention of photo scale and flying height; for (d) angular relationships on stereonet; for (e) strain ratios (X/Y, Y/Z) and Flinn diagram parametersOccasional numbers without context—'thousands of volcanoes,' 'high resolution,' 'some plates'; mentions that GIS handles quantitative data without specifics; strain 'measured' without ratios or parametersNo quantitative content; avoids all numbers; qualitative descriptions only; 'very large,' 'many,' 'high' as substitutes; no appreciation that stereonet is angular measurement tool or that strain ellipsoid embodies finite strain ratios
Indian / economic relevance20%10Indian context throughout: for (a) Andaman-Nicobar subduction zone as Ring of Fire extension, 2004 tsunami; for (b) Indian GIS applications (Bhuvan, NATMO, mineral exploration, groundwater mapping); for (c) Indian aerial survey organizations (Survey of India, NRSC Hyderabad); for (d) structural analysis in Indian ore deposits (Kolar gold, Singhbhum shear zone); for (e) Himalayan strain studies, plate convergence rates (~5 cm/yr India-Asia)Brief Indian mention—'GIS is used in India' or 'Himalayas have earthquakes'; NRSC or Bhuvan named without function; Indian examples appended as afterthought rather than integratedNo Indian or economic context; exclusively foreign examples (San Andreas, Yellowstone, USGS); misses opportunity to cite India's Ring of Fire proximity, domestic GIS infrastructure, or economic mineral/structural geology applications

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