Q3
(a) Elucidate the types of glacier and illustrate the erosional and depositional features produced by the valley-glaciers. (20 marks) (b) Discuss the origin, composition and classification of meteorites. (15 marks) (c) What is a rock cleavage ? Describe the different types of rock cleavages with the help of neat diagrams. (15 marks)
हिंदी में प्रश्न पढ़ें
(a) हिमनद के प्रकारों पर प्रकाश डालिए तथा घाटी-हिमनद द्वारा निर्मित अपरदन एवं निक्षेपण लक्षणों को उदाहरण दे कर समझाइए । (20 अंक) (b) उल्कापिंडों की उत्पत्ति, संरचना और वर्गीकरण की विवेचना कीजिए । (15 अंक) (c) शैल विदलन क्या है ? स्पष्ट आरेखों की सहायता से विभिन्न प्रकार के शैल विदलनों का वर्णन कीजिए । (15 अंक)
Directive word: Elucidate
This question asks you to elucidate. 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 'elucidate' demands clear, illuminating explanation with examples. For part (a) carrying 20 marks, allocate ~40% word budget covering glacier classification first, then detailed erosional-depositional features with diagrams. Part (b) on meteorites (15 marks) requires ~30% coverage discussing cosmic origin, mineral/metal composition, and three-class system. Part (c) on rock cleavage (15 marks) needs ~30% with definition, genetic classification (fracture/slippage/flow cleavage), and labeled diagrams. Structure: brief intro → systematic part-wise treatment → integrated conclusion on geological processes.
Key points expected
- Part (a): Classification of glaciers into valley/alpine, continental ice sheets, piedmont, cirque glaciers; erosional features (cirques, arêtes, horns, U-shaped valleys, roche moutonnée, striations) and depositional features (moraines—terminal, lateral, medial, ground; drumlins; eskers; outwash plains)
- Part (a): Clear distinction between valley glacier and ice sheet mechanics; explanation of plucking and abrasion as erosion mechanisms
- Part (b): Origin from asteroid belt disruption, cometary debris, lunar/martian ejection; composition—metallic (Fe-Ni), stony (silicates), stony-iron; classification system (chondrites, achondrites, irons, stony-irons) with diagnostic features
- Part (c): Definition of rock cleavage as planar fabric allowing splitting; genetic types—fracture/joint cleavage, slippage/flow cleavage (slaty, schistose, gneissic); relationship to metamorphic grade and stress orientation
- Part (c): Distinction between cleavage and bedding; explanation of how cleavage develops perpendicular to maximum shortening direction
Evaluation rubric
| Dimension | Weight | Max marks | Excellent | Average | Poor |
|---|---|---|---|---|---|
| Concept correctness | 25% | 12.5 | Precise definitions: for (a) correctly distinguishes warm-based vs cold-based glacier dynamics and erosion mechanisms; for (b) accurately describes chondrules, Widmanstätten patterns, and differentiation between meteorite classes; for (c) correctly explains cleavage as tectonic fabric element distinct from primary bedding, with proper genetic mechanisms | Basic definitions present but confuses glacier types or conflates cleavage types; meteorite classification incomplete or with errors in composition; minor conceptual errors in erosion-deposition processes | Major misconceptions: confuses cleavage with stratification, misidentifies meteorite origins as terrestrial, or fundamentally misunderstands glacial erosion as solely water-based; significant factual errors across parts |
| Diagram / cross-section | 25% | 12.5 | Neat, labeled diagrams for (a) showing U-valley cross-section with cirque, arête, horn, roche moutonnée profile, and moraine types; for (c) illustrating cleavage-bedding relationships, and three cleavage types with stress arrows; proper use of geological symbols and scale | Diagrams present but poorly labeled, missing key features, or lacking scale; cleavage diagrams show fabric without orientation relationships; glacial features sketched without process indication | Absent or unintelligible diagrams; scribbled sketches without labels; diagrams contradict text description; no attempt at illustrating 3D geometry of cleavage or glacial landforms |
| Field evidence | 15% | 7.5 | Cites specific Indian examples: for (a) Gangotri glacier, Siachen glacier features, Ladakh glacial landforms, or Pleistocene glacial evidence in Kashmir/Himachal; for (c) cleavage in Himalayan metamorphics (Darjeeling schists, Sikkim gneisses); references actual field criteria for identification | Generic mention of Himalayan glaciers or metamorphic rocks without specific localities; field identification criteria mentioned but not linked to Indian examples; international examples substituted where Indian ones exist | No field examples; purely theoretical treatment; incorrect attribution of features (e.g., citing Vindhyan cleavage in unmetamorphosed rocks); confusion between field observation and laboratory data |
| Quantitative reasoning | 15% | 7.5 | Includes quantitative aspects: for (a) approximate glacier velocities (cm/day to m/year), erosion rates (mm/year), or dimensions of typical landforms; for (b) meteorite fall statistics, mass distribution, or cosmic ray exposure ages; for (c) strain ratios or angular relationships between cleavage and fold axes | Mentions numerical ranges approximately but without precision; qualitative treatment dominates; numbers cited without units or context | No quantitative data; avoids all numerical aspects; incorrect orders of magnitude (e.g., glacier erosion as meters per year); confusion between absolute and relative dating in meteorite context |
| Indian / economic relevance | 20% | 10 | Strong Indian relevance: for (a) Himalayan glacier monitoring for water security (Ganga, Indus, Brahmaputra), GSI glacial studies, climate change impacts on Indian rivers; for (b) meteorite finds in India (Nedagolla, Haripura, Shergotty), meteoritic iron in ancient Indian metallurgy; for (c) economic significance of cleavage in slate/quarrying industry (Rajasthan, Haryana), dam site geology, tunneling hazards | Brief mention of Himalayan water resources or slate industry without elaboration; generic statement on meteorite research; misses connection between cleavage and engineering geology applications in Indian infrastructure | No Indian context; completely misses economic dimensions; irrelevant international focus; fails to connect geological concepts to GS&Mains syllabus requirements on Indian economic geography |
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