Important MCQ of Geology

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Sedimentary Texture

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Texture of Sedimentary Rocks in Detail The texture of sedimentary rocks describes the physical characteristics of the sediment grains that compose the rock, including grain size, shape, sorting, packing, fabric, matrix, and cementation. The texture provides important clues about the rock's depositional environment, transport history, and diagenetic changes. Below is an in-depth discussion of each aspect. 1. Grain Size Grain size refers to the diameter of the individual sediment particles. It is one of the most critical parameters in classifying sedimentary rocks. The Wentworth Scale is widely used to classify grains by size: Wentworth Grain Size Scale Key Interpretations: Coarse-grained rocks (gravel, pebbles, cobbles, boulders) → High-energy environments (rivers, glaciers, debris flows). Medium-grained rocks (sandstones) → Moderate-energy environments (beaches, rivers, wind-blown dunes). Fine-grained rocks (siltstones, shales, mudstones) → Low-energy enviro...
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Seismic Zones of India

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India lies at the convergence of the Indian Plate and the Eurasian Plate, which makes it geologically active. This tectonic movement is the primary reason for earthquakes. To minimize the impact of earthquakes, the country is divided into seismic zones based on the following factors: 1. Plate Tectonics: The collision of the Indian Plate with the Eurasian Plate forms the Himalayan range, leading to intense seismic activity in northern and northeastern regions. The peninsular region, though relatively stable, has faults that occasionally lead to earthquakes. 2. Historical Earthquake Data: Zones are identified based on past earthquakes, their magnitudes, and the areas affected. 3. Risk Management: Zoning helps in designing earthquake-resistant infrastructure to mitigate damage and loss of life in high-risk areas. India is divided into four seismic zones based on the likelihood and intensity of earthquakes, ranging from Zone II (low risk) to Zone V (very high risk). These zones are determi...
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Minerals : Classification and Physical properties

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Mineral is a naturally occurring, homogeneous inorganic compound having fixed chemical composition and atomic structure formed due to inorganic processes of the Earth. Classification of Rock forming Minerals These are mainly of two types I Silicates Silicates again subdivided into 1. Ferromagnesian minerals i)  Olivine group of minerals ii) Pyroxene group of minerals iii) Amphibole group of minerals iv) Biotite 2. Non Ferromagnesian minerals i)  Feldspar group of minerals ii) Quartz group of minerals iii) Muscovite II Non Silicates Oxides Sulphides Sulphates Carbonates Physical Properties of Minerals Minerals are identified on the basis of following physical properties 1. Colour 2. Streak 3. Lustre 4. Fracture 5. Cleavage 6. Hardness 7. Specific Gravity 8. Form and structure  1. Colour The colour of a mineral depends on the absorption of some and reflectance of other of the coloured rays which constitute the white light. 2. Streak Streak of a miner...
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