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Q21. Cirques are landforms created by the geological action of:
Cirques are bowl-shaped depressions formed by glacial erosion at the head of a valley. Rivers form V-shaped valleys.
Q22. Clay minerals and Fe-oxide minerals are best detected using which Thematic Mapper (TM) band ratios?
Clay exhibits absorption in band 7 and reflectance in band 5 (High 5/7). Iron oxide absorbs in band 1 and reflects in band 3 (High 3/1).
Q23. Both strength and plasticity of a rock increase with the:
Confining pressure increases the strength (resistance to fracture) and ductility (plasticity) of rocks by inhibiting crack propagation.
Q24. The velocity discontinuity between the upper crust and the lower crust is known as:
Conrad separates Upper (Felsic) and Lower (Mafic) crust. Moho separates Crust/Mantle. Gutenberg separates Mantle/Core.
Q25. The first continental red beds appeared in which Eon?
Continental red beds (oxidized iron sediments) signify the presence of free atmospheric oxygen, which accumulated significantly during the Great Oxidation Event in the early Proterozoic.
Q26. The hardest oxide mineral in the Mohs' scale of hardness is:
Corundum (Al2O3) has a hardness of 9. Note that Diamond (10) is a native element, not an oxide. Topaz (8) is a silicate.
Q27. In a metamorphic terrain, crenulations at the hinge zone of a fold along with the development of axial plane foliation is evidence of:
Crenulation occurs when an earlier foliation is folded by a later deformation event, proving multiple phases.
Q28. Amongst the following, which one will have the highest P-wave velocity?
Diamond has an extremely high bulk modulus and shear modulus, resulting in a P-wave velocity of approximately 18 km/s, far higher than common rocks.
Q29. Choose the correct option where both organisms do NOT secrete CaCO3.
Diatoms and Radiolaria both build skeletons out of Silica (Opaline Silica), not Calcium Carbonate.
Q30. Structure contours of a bedding plane at 100 m interval are spaced such that the horizontal equivalent is also 100 m. The dip is:
Dip is calculated as tan(dip) = Vertical Interval / Horizontal Equivalent. tan(dip) = 100/100 = 1. Therefore, dip = 45 degrees.