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Q21. The rock-type used to build the walls of the Red Fort in Delhi is
The Red Fort is famous for being built with red sandstone.
Q22. A coarse-grained igneous rock consists of 55% olivine, 25% augite and 20% enstatite. According to the IUGS classification, the rock is
The rock is ultramafic (>90% mafic minerals). With >40% olivine, it's a peridotite. Containing both clinopyroxene (augite) and orthopyroxene (enstatite) in significant amounts places it in the Lherzolite field.
Q23. The angle of inclination of the remanent magnetization of a volcanic rock measured at a location is 45°. The magnetic latitude of the location of the volcanic rock at the time of its magnetization is _________ °N. [round off to 1 decimal place]
Tan(Inclination) = 2 * Tan(Latitude). Tan(45) = 1. 1 = 2 * Tan(Lat). Tan(Lat) = 0.5. Lat = arctan(0.5) approx 26.56 degrees.
Q24. Assuming the rate of rotation of the Earth is 7.27 * 10^-5 radians/s and the radius of Earth is 6371 km, the centrifugal acceleration at 60 degrees latitude for a spherically rotating Earth is ______ * 10^-3 m/s2. [round off to 1 decimal place]
Centrifugal acceleration a = w^2 * R * cos(latitude). w = 7.27e-5, R = 6.371e6 m, lat = 60. a = (7.27e-5)^2 * 6.371e6 * 0.5 = 5.285e-9 * 3.1855e6 = 0.01683 m/s^2 = 16.8 * 10^-3 m/s^2.
Q25. The difference in arrival times of P- and S-waves generated by an earthquake and recorded at a seismological station is one second. Assuming a homogeneous and isotropic Earth, a P-wave velocity (VP) of 3 km/s, the ratio of P- to S-wave velocities (VP/VS) of 2.0, the distance between the station and the hypocenter is __________km. [round off to 1 decimal place]
Given Vp/Vs = 2, Vs = Vp/2 = 1.5 km/s. Time difference T = D/Vs - D/Vp = 1. D(1/1.5 - 1/3) = 1. D(2/3 - 1/3) = 1. D(1/3) = 1. D = 3 km.
Q26. Choose the CORRECT statement(s) on seismic wave propagation in an elastic isotropic medium.
P-waves are longitudinal (polarized in propagation direction). S-waves are transverse. Rayleigh waves show retrograde elliptical particle motion. Love waves are polarized horizontally (transverse).
Q27. Which one of the following is a mafic volcanic rock?
Basalt is a mafic volcanic rock. Dacite and Rhyolite are felsic; Trachyte is intermediate/alkaline.
Q28. How many independent elastic parameters are needed to describe a homogenous isotropic material?
An isotropic linear elastic material requires only 2 independent parameters (e.g., Young's Modulus and Poisson's ratio) to describe its elasticity.
Q29. For a productive alluvial aquifer with hydraulic conductivity = 105 m/day and hydraulic gradient = 0.01, the flow rate is _________ m/day. [round off to 2 decimal places]
Darcy's law gives the specific discharge (Darcy velocity) q = K * i. Calculation: 105 * 0.01 = 1.05 m/day.
Q30. The average bulk density of a fully saturated sandstone reservoir with a fractional porosity of 0.23 is ______ g/cc. [round off to 2 decimal places] [Assume matrix density for sandstone = 2.63 g/cc and fluid density = 1.05 g/cc]
Bulk density = (1 - porosity) * matrix_density + (porosity * fluid_density). Calculation: (0.77 * 2.63) + (0.23 * 1.05) = 2.0251 + 0.2415 = 2.2666. Rounded to 2 decimal places: 2.27.