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Q111. Given the present understanding, identify the correct sequence of impacts that adversely affect the marine fish harvests.
Historically, over-exploitation (overfishing) has been the primary driver of marine harvest collapse, followed by coastal pollution, broad climate change impacts, and cyclical events like El Nino.
Q112. In order to have the same value of the surface acceleration due to gravity as on Earth, a planet twice its radius must have a mean relative density of:
Gravity g is proportional to Radius * Density. If the radius is doubled, the density must be halved to keep gravity identical. Earth's relative density is ~5.5, so the planet's density must be 5.5 / 2 = 2.75.
Q113. Compared to basalts, granites are:
Granites are felsic rocks (density ~2.7 g/cc) and typically paramagnetic (low magnetism), whereas basalts are mafic (density ~3.0 g/cc) and often contain magnetite.
Q114. Two minerals, A and B, which do not show solution behaviour (at atomic scales) have melting temperatures 1200°C and 1000°C, respectively, at one atmospheric pressure. If they are physically mixed, the temperature of melting of the mixture will be around:
For a mechanical mixture of two minerals that form a eutectic system, the melting point of the mixture (the eutectic temperature) is always lower than the melting point of either pure end-member.
Q115. Where do you find rocks of ferromagnetic character in the Earth?
Ferromagnetism disappears above the Curie temperature (~580°C for magnetite). Only the crust is cool enough to sustain ferromagnetic minerals.
Q116. Which one of the following structures is an example of ductile deformation?
Faults, fractures, and joints all represent brittle failure, where the rock breaks. Folds represent ductile (plastic) deformation, where the rock bends permanently without breaking.
Q117. Which one of the following represents the correct ascending order of appearance in geological history of the Earth?
Evolutionary timeline: Fishes appeared first (Ordovician/Silurian), followed by Amphibians (Devonian), Reptiles (Carboniferous), and finally Mammals (Triassic).
Q118. On a rotating spheroidal Earth, its gravity field increases from the equator to the poles. On a non-rotating spheroidal Earth, the gravity field:
Even without rotation (centrifugal force), a spheroidal Earth is oblate. The poles are physically closer to the center of mass than the equator, so gravitational attraction (GM/r^2) remains stronger at the poles.
Q119. Which of the following isotope ratios get significantly fractionated during evaporation of sea water?
Evaporation heavily fractionates light isotopes from heavy ones. The lighter 16O isotope evaporates much more readily than the heavier 18O, strongly fractionating the oxygen ratio.
Q120. Entrainment of air into cumulus clouds results in:
Entrainment mixes dry environmental air into the cloud. This forces cloud droplets to evaporate, which absorbs latent heat, cools the parcel, and consequently decreases its buoyant uplift.