JNTU
JNTU B.Tech III GENERAL GEOLOGY Previous Question Paper (August/September - 2021 - R18)
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Main
Write in detail about the origin, classification and mitigation of earthquakes.
Answer
An earthquake is the sudden shaking of the Earth's surface caused by the rapid release of energy in the lithosphere, which generates seismic waves.
Origin: Earthquakes primarily originate from the movement of tectonic plates along fault lines. When stress accumulates in rocks beyond their elastic limit, they undergo brittle failure, causing a sudden displacement. The point of origin within the Earth is the hypocenter (or focus), and the point directly above it on the surface is the epicenter. Energy is released as seismic waves, categorized as P-waves (primary), S-waves (secondary), and surface waves (Love and Rayleigh waves).
Classification: Earthquakes are classified based on several criteria:
- Based on Depth: Shallow-focus (0–70 km), intermediate-focus (70–300 km), and deep-focus (>300 km).
- Based on Cause: Tectonic (most common), volcanic (associated with magma movement), collapse (due to underground caverns or mines), and anthropogenic (induced by human activities like reservoir filling or fracking).
- Based on Magnitude/Intensity: Measured using the Richter Scale (magnitude based on energy release) or the Modified Mercalli Intensity Scale (based on observed damage and human perception).
Mitigation: Reducing the impact of earthquakes involves both structural and non-structural measures:
- Building Codes: Implementing strict seismic-resistant building designs, such as base isolation systems, cross-bracing, and the use of ductile materials like reinforced concrete and steel.
- Land-Use Planning: Conducting seismic microzonation studies to identify high-risk fault zones and restricting critical infrastructure development in these areas.
- Early Warning Systems: Deploying sensor networks to detect P-waves and provide seconds to minutes of warning, allowing for the automatic shutdown of gas lines and power grids.
- Public Awareness: Conducting regular drills, educating the public on safe evacuation procedures, and retrofitting older, vulnerable structures to withstand lateral seismic forces.
Give a detailed description on weathering process of rocks.
Answer
Weathering is the physical disintegration and chemical decomposition of rocks at or near the Earth's surface by atmospheric agents. It is categorized into three main types:
- Physical Weathering (Mechanical): This process involves the breakdown of rocks into smaller fragments without changing their chemical composition. Key mechanisms include thermal expansion and contraction due to temperature fluctuations, frost wedging (expansion of water in cracks upon freezing), and exfoliation (peeling of outer layers due to pressure release).
- Chemical Weathering: This involves chemical reactions that alter the mineral composition of rocks. Common processes include oxidation (reaction with oxygen, e.g., rusting of iron-bearing minerals), carbonation (reaction with carbonic acid to dissolve minerals like calcite), and hydrolysis (reaction with water to form clay minerals from silicates).
- Biological Weathering: This is caused by living organisms. Plant roots exert mechanical pressure by growing into rock fractures, while organic acids produced by decaying vegetation and microorganisms chemically attack rock surfaces.
Give a brief account on soil erosion and conservation.
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What processes are involved in the formation of the landform? Explain briefly.
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What are the geomorphic processes that affect landforms? Discuss in detail.
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Discuss the difference in geomorphology of the eastern coast and western coast in India. What is the main reason of the difference?
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Describe in brief about the types of landforms produced by Rivers.
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Give a detailed account of the geological investigations that are to be carried out to develop coastal Engineering structures.
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Describe the structures and textures of igneous rocks. Give typical examples.
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Explain briefly methods of preparation of organic walled microfossils.
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