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Q81. Which one of the following statements is CORRECT regarding shoreline movement?
Forced regression occurs when relative sea level falls, forcing the shoreline to move seaward. Transgression is landward movement.
Q82. Which one of the following rocks has the highest magnetic susceptibility value?
Gabbro is a mafic igneous rock often containing magnetite, giving it much higher susceptibility than sedimentary or metamorphic rocks like limestone/quartzite.
Q83. Which of the following logging techniques is best suited to estimate the shaliness of hydrocarbon reservoirs?
Gamma Ray logs measure natural radioactivity. Shales are naturally radioactive (due to K, U, Th), so high Gamma readings indicate shale.
Q84. Which of the following rocks contributes the highest amount of radioactive heat in the earth's crust?
Granite contains high concentrations of incompatible radioactive elements like Uranium (U), Thorium (Th), and Potassium (K) compared to mafic rocks.
Q85. Choose the correct pair of plutonic rock and its volcanic equivalent.
Granite is a felsic plutonic rock, and its volcanic (extrusive) equivalent with the same composition is Rhyolite.
Q86. Which geophysical method is most suitable for exploring a horizontally stratified graphite deposit at 50 m depth?
Graphite is a highly conductive mineral, making Electromagnetic (EM) methods the most effective tool for detection.
Q87. The acceleration due to gravity 'g' is maximum at:
Gravity is strongest at the poles because the Earth is an oblate spheroid (flattened at poles), so the surface is closer to the center of mass.
Q88. As compared to large earthquakes, small earthquakes are:
Gutenberg-Richter law states small quakes are much more frequent. Small magnitude implies a smaller rupture area and shorter slip displacement.
Q89. If a radioactive isotope has a decay constant of 1.55 x 10^-10 year^-1, its half-life (in years) would be:
Half-life (t1/2) = 0.693 / decay constant. 0.693 / (1.55 x 10^-10) = 4.47 x 10^9 years.
Q90. Which one of the following options is arranged in the CORRECT increasing order of Vicker's micro-hardness?
Hardness: Galena (2.5) < Chalcopyrite (3.5-4) < Sphalerite (3.5-4, harder) < Magnetite (5.5-6.5).