UPSC Mains Answer PYQ 2023: Geology Paper 1 (Section- B) | Geology Optional Notes for UPSC PDF Download

Note: These sample answers provide a brief overview of the topic. You may add or reduce information as you see fit, depending on your understanding.

Section - B

Q5: Answer the following questions in about 150 words each: (10x5=50)
(a) Enumerate the different types of siwalik fauna and discuss their palaeoecology.   (10 Marks)
Ans: 
Introduction: 
The Siwalik Hills in northern India contain rich fossil deposits representing the Siwalik fauna, which lived during the Miocene and Pliocene epochs.

Types of Siwalik Fauna:

• Mammals:
  Examples: Sivatherium, Stegodon, Hipparion, Ramapithecus (an early hominid ancestor).

• Reptiles:
  Examples: Crocodiles, turtles, snakes, and various types of lizards.

• Birds:
  Examples: Large flightless birds like Gastornis and smaller avian species.

• Amphibians and Fishes:
  Examples: Various species of amphibians and fish adapted to wetland environments.

Palaeoecology:

1. Terrestrial Environment: The Siwalik fauna indicates a diverse range of terrestrial habitats, including forests, grasslands, and wetlands.

2. Habitat Preferences:

• Species like Stegodon and Sivatherium suggest a mix of wooded and grassy environments.
• Presence of crocodiles and turtles implies the existence of wetlands or rivers.

3. Climate Inference: The presence of different species adapted to various ecological niches suggests a mosaic of environments, possibly influenced by seasonal changes.

4. Biodiversity Patterns: The Siwalik fauna showcases a wide range of mammals, indicating a region of high biodiversity and species richness.

Conclusion: 
The Siwalik fauna provides invaluable insights into the ancient ecosystems of the Miocene and Pliocene epochs. It helps reconstruct the palaeoenvironment and understand the ecological interactions of various species during that time.

(b) Define fossil and give examples of two index fossils each from Palaeozoic, Mesozoic and Cenozoic Era and indicate the age of those index fossils.    (10 Marks)
Ans: 
Definition of Fossil: A fossil is the remains or traces of a once-living organism preserved in rocks or sediments.

Index Fossils:
1. Palaeozoic Era:

• Trilobites: Example - Phacops rana, indicative of the Devonian Period (416 to 359 million years ago).
• Ammonoids: Example - Goniatites, characteristic of the Carboniferous Period (359 to 299 million years ago).

2. Mesozoic Era:

• Dinosaurs: Example - Tyrannosaurus rex, indicative of the Late Cretaceous Period (145 to 66 million years ago).
• Ammonites: Example - Baculites, prevalent in the Late Cretaceous Period.

3. Cenozoic Era:

• Foraminifera: Example - Globigerina, widely used in dating marine sediments of the Cenozoic Era.
• Mammals: Example - Equus (genus containing horses), useful in dating Quaternary deposits (2.58 million years ago to present).

Conclusion: 
Index fossils serve as key indicators of specific geological time periods. They play a crucial role in relative dating and correlating rock layers across different regions.

(c) Describe the lithology, palaeoenvironment and age of Krol Formation.      (10 Marks)
Ans: 
Lithology:

• The Krol Formation consists of conglomerates, sandstones, and shale.
• It contains sedimentary rocks with variable grain sizes, indicating deposition in different environments.

Palaeoenvironment:

• The Krol Formation represents a fluvial environment with evidence of alluvial fans, braided rivers, and associated deposits.
• It suggests a dynamic landscape with significant erosion and sediment transport.

Age:

• The Krol Formation is believed to be of Proterozoic age, possibly dating back to the Late Neoproterozoic era, around 750 to 560 million years ago.

Conclusion: 
The Krol Formation provides insights into the geological history of the region, offering clues about ancient environments and the processes that shaped the landscape during the Proterozoic Era.

(d) Briefly discuss the water-bearing properties of rocks.    (10 Marks)
Ans: 
Porosity:

• Porosity refers to the percentage of open space (pores) in a rock. It determines a rock's capacity to hold water.
• Example: Sandstone typically has high porosity due to its well-connected pore spaces.

Permeability:

• Permeability measures a rock's ability to transmit fluids through its pores. It depends on the connectivity of the pore spaces.
• Example: Well-sorted, rounded sandstone has high permeability.

Aquifers and Aquitards:

• Aquifers are permeable rock layers that can store and transmit water (e.g., sandstone).
• Aquitards are less permeable layers that hinder the flow of water (e.g., clay layers).

Groundwater Flow:

• Water moves through interconnected pore spaces in rocks, driven by gravity.
• The direction and rate of flow depend on porosity, permeability, and hydraulic gradient.

Conclusion: 
The water-bearing properties of rocks are crucial for understanding groundwater movement and availability. They influence the design and management of water resource systems.

(e) What are the engineering properties of rocks that make them suitable for use as building materials ?   (10 Marks)
Ans: 
Strength and Durability:

• Rocks with high compressive strength, like granite and basalt, are suitable for load-bearing structures.
• High resistance to weathering and erosion ensures durability.

Workability:

• Some rocks, like limestone and sandstone, are easily cut, carved, and shaped, making them suitable for intricate architectural details.

Texture and Appearance:

• Fine-grained rocks like marble and slate offer a smooth, elegant finish, ideal for decorative elements.
• Coarser-grained rocks may be preferred for a more natural or rustic appearance.

Dimensional Stability:

• Rocks with low porosity and low water absorption rates are less likely to undergo significant dimensional changes when exposed to moisture.

Conclusion: 
The engineering properties of rocks determine their suitability for specific construction purposes. Considerations like strength, workability, and appearance play a vital role in selecting appropriate building materials.

Q6:
(a) Elucidate an evolutionary trend of Equidae with Indian occurrence.     (20 Marks)
Ans: 
Introduction: 
The Equidae family encompasses modern horses, zebras, and asses. The evolution of Equidae is marked by significant changes in dental morphology and limb structure.

Evolutionary Trend:
1. Early Equidae (Eocene Epoch):

• Dental Morphology: Primitive horse ancestors had bunodont molars adapted for browsing.
• Limb Structure: Multitoed feet with separate toes.

2. Mesohippus (Oligocene Epoch):

• Dental Morphology: Development of hypsodont molars for grazing on tougher vegetation.
• Limb Structure: Reduction of toes, transition towards single hoofed foot.

3. Merychippus (Miocene Epoch):

• Dental Morphology: Further development of hypsodont molars for grazing.
• Limb Structure: Lengthening of limbs, increased cursorial adaptation.

4. Pliohippus (Pliocene Epoch):

• Dental Morphology: Continued adaptation for grazing, high-crowned molars.
• Limb Structure: Further refinement for speed and endurance.

5. Modern Equus (Pleistocene to Present):

• Dental Morphology: High-crowned molars, suitable for grazing on grasses.
• Limb Structure: Adapted for efficient galloping.

Indian Occurrence:

• India has a rich fossil record of Equidae, with discoveries of various genera like Hipparion, Merychippus, and Equus in the Siwalik Hills.
• The Siwalik fossils provide valuable insights into the evolutionary history and adaptations of Equidae in the Indian subcontinent.

Conclusion: 
The evolutionary trend of Equidae showcases the remarkable adaptations that led to the development of modern horses. The Indian fossil record contributes significantly to our understanding of this evolutionary process.

(b) Discuss the pre-cambrian/cambrian boundary with Indian examples.     (15 Marks)
Ans: 
Introduction: 
The Pre-Cambrian/Cambrian boundary represents a significant geological transition, marking the emergence of complex life forms in the fossil record.

Boundary Features:
1. Appearance of Trilobites:

• Trilobites are distinctive marine arthropods that first appear in the Cambrian.
• Indian Example: Trilobite fossils are found in the Cambrian rocks of the Spiti Valley in Himachal Pradesh.

2. Burgess Shale Fauna:

• Burgess Shale in Canada contains exceptionally preserved soft-bodied organisms from the Cambrian.
• Indian Example: While not directly related, the Burgess Shale fauna provides a global perspective on Cambrian life forms.

3. First Hard-Shelled Organisms:

• Cambrian rocks record the first appearance of organisms with mineralized skeletons.
• Indian Example: The Vindhyan Supergroup in India contains fossils of early organisms with mineralized structures.

4. Global Stratigraphic Markers:

• Isotopic and radiometric dating techniques provide precise boundaries for the Pre-Cambrian/Cambrian transition.
• Indian Example: Isotopic studies of rocks in Rajasthan and other regions contribute to the understanding of this boundary.

Conclusion: 
The Pre-Cambrian/Cambrian boundary is a pivotal interval in Earth's history, representing the emergence of complex life forms. Indian geological studies and fossil records contribute to the global understanding of this critical transition.

(c) What is “Rainwater harvesting” ? Describe its technique with neat sketches.    (15 Marks)
Ans: 
Introduction: 
Rainwater harvesting is a method of collecting and storing rainwater for later use, helping to conserve water resources.

Technique:
1. Catchment Surface:

• A catchment surface (usually a roof) is used to collect rainwater.
• Sketch: [Insert Neat Sketch]

2. Gutters and Downpipes:

• Gutters and downpipes direct rainwater from the catchment surface into storage tanks.
• Sketch: [Insert Neat Sketch]

3. Filtration and Storage:

• The collected rainwater is filtered to remove debris and contaminants before being stored in tanks or reservoirs.
• Sketch: [Insert Neat Sketch]

4. Distribution and Use:

• The stored rainwater can be distributed for various purposes like irrigation, household use, or groundwater recharge.
• Sketch: [Insert Neat Sketch]

Benefits:

• Reduces reliance on groundwater and surface water sources.
• Mitigates flooding and erosion.
• Promotes self-sufficiency in water supply, especially in areas with limited access to clean water.

Conclusion: 
Rainwater harvesting is a sustainable water management practice that helps address water scarcity issues. By utilizing simple techniques, communities can make efficient use of a readily available resource.

Q7:
(a) Describe the stratigraphic sequence of Dharwar Supergroup and add a note on its economic importance.    (20 Marks)
Ans: 
Introduction: 
The Dharwar Supergroup is a major geological unit in India, comprising a sequence of rocks that formed during the Archean Eon (about 2.5 to 2.7 billion years ago).

Stratigraphic Sequence:
1. Basement Complex:

• Oldest rocks, including granite and gneiss.
• Dated to around 3 billion years ago.

2. Chitradurga Group:

• Contains metavolcanics, metasediments, and ferruginous quartzites.
• Dated between 2.9 to 2.7 billion years ago.

3. Bababudan Group:

• Dominated by iron ore formations like banded iron formations (BIFs).
• Dated between 2.7 to 2.5 billion years ago.

4. Closepet Granite:

• Intrusive igneous rocks intruding into the older Dharwar rocks.
• Dated around 2.5 billion years ago.

5. Sandur Group:

• Contains banded iron formations, shale, and chert.
• Dated between 2.5 to 2.4 billion years ago.

Economic Importance:
1. Iron Ore Deposits:

• The Dharwar Supergroup is known for its extensive iron ore deposits, particularly in the Sandur Group.
• These deposits are economically significant and have supported the iron and steel industry in India.

2. Gold Mineralization:

• The Dharwar Supergroup hosts gold deposits in areas like Hutti and Kolar in Karnataka.
• These gold mines have historical and economic significance.

3. Granite Resources:

• The Closepet Granite and associated rocks contain valuable granite resources used in construction and as dimension stones.

Conclusion: 
The Dharwar Supergroup is not only of geological interest but also of immense economic importance due to its rich mineral resources, particularly iron ore and gold.

(b) Elucidate the different types of microfossils and add a note on their composition and applications.    (15 Marks)
Ans: 
Introduction: 
Microfossils are microscopic fossils that require a microscope for detailed study. They provide valuable information about ancient environments and biological evolution.

Types of Microfossils:
1. Foraminifera:

• Composition: Single-celled protists with calcareous or siliceous shells.
• Applications: Used in biostratigraphy, paleoenvironmental reconstruction, and petroleum exploration.

2. Diatoms:

• Composition: Single-celled algae with intricate silica shells called frustules.
• Applications: Used in environmental monitoring, paleoclimatology, and oil exploration.

3. Radiolaria:

• Composition: Single-celled protists with intricate siliceous skeletons.
• Applications: Important for biostratigraphy and paleoenvironmental reconstructions.

4. Ostracods:

• Composition: Small, bivalve-like crustaceans with calcareous or chitinous shells.
• Applications: Used in paleoenvironmental and paleoclimate studies.

Composition and Applications:

• Composition: Microfossils are primarily composed of mineralized or organic material, depending on the type. For example, foraminifera have calcareous or agglutinated tests, while diatoms have silica frustules.

• Applications:

  • Biostratigraphy: Microfossils are used to date and correlate rock layers, aiding in geological and paleontological studies.
  • Paleoecology: They provide information about past environments, such as temperature, salinity, and nutrient levels.
  • Petroleum Exploration: Microfossils are used as indicators of potential oil and gas reservoirs.

Conclusion: 
Microfossils play a crucial role in understanding Earth's history and environmental changes. Their composition and applications contribute to a wide range of scientific disciplines.

(c) How does an Earthquake occur ? Describe the construction patterns of earthquake resistant structures.    (15 Marks)
Ans: 
Introduction: 
An earthquake occurs due to the sudden release of energy in the Earth's crust, leading to seismic waves that cause ground shaking.

Earthquake Occurrence:
1. Tectonic Plate Movements:

• Most earthquakes are caused by the movement of tectonic plates along faults.
• Example: The 2010 Haiti earthquake was caused by the movement of the Caribbean and North American plates.

2. Volcanic Activity:

• Earthquakes can occur due to volcanic eruptions and associated magma movements.
• Example: The 1980 Mount St. Helens eruption in the USA triggered seismic activity.

Construction of Resistant Structures:
1. Base Isolation:

• Technique to decouple a building's foundation from the ground motion using flexible bearings or isolators.
• Example: The Tokyo Skytree in Japan utilizes base isolation to withstand earthquakes.

2. Reinforced Concrete and Steel Frames:

• Buildings with reinforced concrete and steel frames provide flexibility and strength during shaking.
• Example: The Taipei 101 tower in Taiwan incorporates advanced engineering to resist earthquakes.

3. Damping Systems:

• Damping devices absorb and dissipate seismic energy, reducing structural movement.
• Example: The Golden Gate Bridge in San Francisco has dampers to enhance earthquake resistance.

4. Bracing and Shear Walls:

• Bracing elements and shear walls provide lateral stability to prevent swaying during an earthquake.
• Example: Many modern skyscrapers incorporate diagonal bracing for added stability.

Conclusion: 
Constructing earthquake-resistant structures is crucial in regions prone to seismic activity. Employing advanced engineering techniques helps safeguard lives and property during earthquakes.

Q8:
(a) Discuss briefly how do chemical, physical and bacteriological properties determine the usability of ground-water.    (20 Marks)
Ans: 
Introduction: 
Groundwater is a crucial natural resource that requires evaluation based on its chemical, physical, and bacteriological properties to ensure its suitability for various purposes.

Determinants of Groundwater Usability:
1. Chemical Properties:

• pH Levels: Determines the acidity or alkalinity of water. For example, water with high acidity may corrode pipes and affect taste.
• Mineral Content: Elevated levels of minerals like iron, manganese, or salts may render water unsuitable for drinking or irrigation.
• Presence of Contaminants: Chemical pollutants, such as heavy metals or pesticides, can make groundwater hazardous.

2. Physical Properties:

• Turbidity: High turbidity indicates the presence of suspended particles, affecting the visual clarity and palatability of water.
• Temperature: Extreme temperatures can affect the suitability of water for certain industrial processes or aquatic ecosystems.
• Odor and Taste: Unpleasant odors or tastes may arise from organic matter or chemical contaminants, impacting usability.

3. Bacteriological Properties:

• Presence of Pathogens: Bacteria, viruses, or parasites in groundwater can pose health risks if consumed without treatment.
• Total Coliform and E. Coli Levels: Indicators of fecal contamination, which can lead to waterborne diseases.

Examples:

• Iron Content: High iron levels in groundwater can lead to iron staining of fixtures and a metallic taste in water.
• High Turbidity: Muddy or cloudy water may not be suitable for drinking without proper treatment.
• Elevated Nitrate Levels: Groundwater contaminated with nitrates from agricultural runoff can pose health risks, especially for infants.

Conclusion:
Evaluating chemical, physical, and bacteriological properties is essential for determining the suitability of groundwater for various uses, including drinking, irrigation, and industrial processes.

(b) Establish the ocean palaeobathymetry using marine fossils with the help of labelled diagram.    (15 Marks)
Ans: 
Introduction: 
Ocean palaeobathymetry is the study of past ocean depths. Marine fossils can provide valuable information about the ancient distribution of marine life, which, in turn, helps reconstruct past ocean depths.

Marine Fossils for Palaeobathymetry:
1. Foraminifera:

• Foraminifera are single-celled protists with calcium carbonate or agglutinated shells.
• Different species live at specific water depths, making them excellent depth indicators.

2. Calcareous Algae:

• Certain types of calcareous algae, like coccolithophores, have depth preferences and can serve as bathymetric indicators.

Palaeobathymetry Diagram:

• A labelled diagram illustrating ocean palaeobathymetry using marine fossils would show the distribution of fossil groups at different water depths.

• The presence of specific foraminifera or calcareous algae at various depths in the sedimentary record would be indicated on the diagram.

• The diagram may also include depth zones, such as the photic zone, mesopelagic zone, and bathyal zone, to show the approximate depths where these fossils were found.

Example:

• Fossilized deep-dwelling foraminifera in a sediment core from the ocean floor indicate that the site was at a greater depth during the period when the organisms lived.

Conclusion: 
Marine fossils are essential tools for understanding past ocean depths and paleoenvironments. They help geologists reconstruct the Earth's geological history and the changing positions of continents and ocean basins.

(c) Discuss the palaeozoic sequence of Kumaun and Garhwal (Tethyan sequence) Himalaya. Add a note on its fossil contents.    (15 Marks)
Ans: 
Introduction:
The Kumaun and Garhwal regions in the Himalayas preserve a rich geological history, particularly from the Palaeozoic era.

Sequence:
1. Precambrian Basement Rocks:

• Granitic and gneissic rocks form the basement of the region, dating back over a billion years.

2. Phanerozoic Cover Sequences:

• Lower Palaeozoic (Cambrian to Silurian): Contains marine sedimentary rocks like limestones, shales, and sandstones with fossils of trilobites, brachiopods, and graptolites.
• Upper Palaeozoic (Devonian to Permian): Includes sedimentary rocks like limestones, sandstones, and shales with fossils of corals, bryozoans, and crinoids.

Fossil Contents:

• Trilobites in Lower Palaeozoic rocks indicate a diverse marine ecosystem.
• Brachiopods, graptolites, and other marine invertebrates are common fossils found in these sequences.

Example: Fossilized trilobite remains in Cambrian rocks of the region provide key insights into the ancient marine environment.

Conclusion:
The Palaeozoic sequence of Kumaun and Garhwal Himalaya reveals a rich fossil record, offering valuable information about the ancient marine ecosystems and geological history of the region.