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Q91. The characteristic properties of a continental tropical airmass are:
Continental tropical (cT) air masses originate over hot, arid landmasses (like the Sahara desert). They are characterized by high temperatures, very low humidity, and instability at low levels.
Q92. The optically active substance that undermines the remote estimation of chlorophyll most is:
Coloured Dissolved Organic Matter (CDOM) strongly absorbs light in the blue wavelength region, which overlaps with the absorption spectrum of chlorophyll, confusing satellite sensors.
Q93. If there is no change in the mean sea level, the submerged coast will:
Coastal processes continue regardless of sea level. Headlands will retreat due to wave erosion, while bays will prograde due to sediment deposition, eventually straightening the coast.
Q94. The largest single contributor to the planetary albedo of the Earth is:
Clouds reflect approximately 20-25% of incoming solar radiation back to space, making them the most significant contributor to Earth's overall albedo.
Q95. Climbing ripple cross laminations form by movement of medium to very fine sand in:
Climbing ripples (or ripple-drift cross-lamination) occur when there is an abundance of sediment falling out of suspension (surplus) while the current is moving in the lower flow regime, causing ripples to build upward over each other.
Q96. A mineral showing about 13 wt% volatiles in its chemical analysis is:
Chlorite is a highly hydrated phyllosilicate mineral, typically containing 12-13% water (volatiles) by weight. Pyroxenes are anhydrous, and amphibole/biotite contain far less water.
Q97. Suppose an ore of Cu contains 20% chalcopyrite by mass. What is the minimum tonnage of the ore desirable if at least 1000 tons of Cu needs to be extracted? (Atomic mass: Cu=63.55, Fe=55.85, S=32.06)
Chalcopyrite is CuFeS2 (Molar mass = 183.52). Cu fraction in chalcopyrite = 63.55/183.52 = 0.346. Since the ore is 20% chalcopyrite, Cu fraction in ore = 0.20 * 0.346 = 0.0692. Tonnage needed = 1000 / 0.0692 = 14,439 tons.
Q98. The effects of a calcrete layer are: (A) Protects underlying weathered material. (B) Prevents infiltration of rainwater to underlying layers. (C) Helps in soil formation beneath. (D) Accelerates chemical weathering beneath.
Calcrete is a hardpan of calcium carbonate. It acts as an impermeable cap, protecting the soil beneath from erosion but also preventing water infiltration, which halts further chemical weathering beneath it.
Q99. Two sedimentary layers of infinite horizontal extension sit one over the other. Layer 1: top=2000m, thickness=1000m, density contrast = 0.4 g/cc. Layer 2: top=3000m, thickness=1000m, density contrast = -0.4 g/cc. The total gravity anomaly on surface is (mGal):
Bouguer gravity of an infinite slab depends only on thickness and density contrast, not depth. Gravity = 2 * pi * G * p * t. Since thickness is equal but density contrast is exactly opposite, they cancel out to 0.
Q100. Attenuation in the amplitude of body and surface waves respectively, with distance r from source is proportional to:
Body waves expand spherically in three dimensions, so amplitude attenuates as 1/r. Surface waves expand cylindrically in two dimensions along the surface, attenuating much slower at 1/sqrt(r).