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Q41. Surface salinity of the equatorial ocean is low because of:
The equator lies along the Intertropical Convergence Zone (ITCZ), characterized by intense heating, rising air, and massive amounts of rainfall. This excess fresh precipitation dilutes the surface salinity.
Q42. Mass balance of a glacier with upward moving equilibrium line altitude (ELA) is:
The ELA divides the accumulation zone from the ablation (melting) zone. An upward-moving ELA means the melting zone is expanding while the accumulation zone is shrinking, resulting in a net loss of ice (negative mass balance).
Q43. Which of the following represents the oldest record of metazoan soft bodied animals?
The Ediacaran fauna (late Proterozoic, ~600 Ma) represents the earliest widely accepted fossil record of multicellular, macroscopic, soft-bodied organisms.
Q44. The biosphere is to a large extent protected from cosmic ray bombardment from outer space. This is due to the presence of:
The Earth's magnetosphere deflects the highly energetic, charged particles of cosmic rays and the solar wind, protecting the atmosphere and biosphere from harmful radiation.
Q45. Two rock masses E and P of identical chemical compositions and physical properties simultaneously acquired thermoremanent magnetism (TRM) at the magnetic equator and pole, respectively. The TRM of P is then:
The Earth's magnetic field at the poles is twice as strong as at the equator and is oriented vertically (normal) compared to the horizontal field at the equator. TRM acquisition is directly proportional to these external field vectors.
Q46. Compared to the Earth, the Moon has a lower average density, because the Moon:
The Earth has a massive iron core (~33% of mass), whereas the Moon's core is very small (~1-2% of mass), significantly lowering its average density.
Q47. The least kinetic energy is required to move:
The dissolved load consists of chemical ions fully in solution. They move passively with the water flow and require virtually zero kinetic or turbulent energy to remain in transport.
Q48. The temperature attained by the atmosphere by isobaric cooling to saturation is known as:
The dew point is strictly defined as the temperature to which a parcel of air must be cooled at constant pressure (isobaric cooling) for its water vapor to condense into liquid.
Q49. Which of the following sets represents mechanical layering of the Earth from the surface to the centre?
The Crust/Mantle/Core classification represents compositional layering. The Lithosphere/Asthenosphere/Mesosphere classification represents mechanical (rheological) layering based on physical properties.
Q50. What is the typical Rayleigh number for the onset of convection?
The critical Rayleigh number represents the threshold where buoyancy forces overcome viscous drag, initiating convection. For fluid layers, this critical value is typically on the order of 10^3 (e.g., 1708 for rigid boundaries).