UPSC Static Quiz – Geography : 10 April 2026

Solution: A

• Statement-I describes the observable structure of the solar system: a rocky core and a gassy exterior.
• Statement-II provides the standard “Nebular Hypothesis” explanation. In the inner disk (inside the “Frost Line” or “Snow Line,” approx 2.7 AU), it was too hot for hydrogen compounds (water, ammonia, methane) to freeze. Only rocks and metals could condense. Furthermore, the young Sun went through a “T-Tauri” phase with intense solar wind, which blew away the light hydrogen/helium gas envelopes that the small inner planets tried to accumulate. In the outer solar system, it was cold enough for ices to form, allowing cores to grow massive enough (10x Earth mass) to gravitationally trap the hydrogen/helium gas before the solar wind could strip it away.

Solution: B

• The description refers to Metamorphism, specifically regional metamorphism where rocks are subjected to directed pressure and heat (short of melting).
• The alignment of platy minerals (like mica) perpendicular to the direction of stress creates a layered or banded appearance known as foliation.
• Differentiation:
  • Igneous rocks form from melting (magma).
  • Sedimentary rocks form from lithification (compaction/cementation) and typically show bedding, not stress-induced foliation.
  • Non-foliated metamorphic rocks (like marble) lack the banding described.

Solution: A

• A radiation inversion typically forms on clear, calm winter nights when the ground loses heat rapidly through longwave radiation. As the surface cools, the air in contact with it also cools, becoming denser and remaining trapped near the ground, while relatively warmer air overlies it. This creates a temperature profile in which temperature increases with height, a classic inversion condition. Calm or very light winds are a crucial prerequisite for this process. When wind speeds exceed roughly 8–10 knots, mechanical turbulence is generated in the lower atmosphere. This turbulence continuously mixes the colder surface air with the warmer air above, disrupting the stratified temperature structure necessary for inversion formation.

Solution: C

• Statement 1 is correct:Igneous rocks are solidified directly from magma (molten mantle/crust material). Since the Earth started as a molten mass, the first solid crust was igneous. Thus, they are called “Primary Rocks”.
• Statement 2 is incorrect:The rock cycle is not a rigid one-way street. Sedimentary rocks can be subducted into the mantle at tectonic plate boundaries. There, they melt to become magma, which then cools to form igneous rock. They do not strictly have to become metamorphic first, although that is a common intermediate step.
• Statement 3 is correct:Any rock type (Igneous, Metamorphic, or Sedimentary) exposed at the surface is subject to weathering and erosion. A metamorphic rock like Gneiss can weather into sediments, which then lithify to form sedimentary rock.

Solution: B

• Statement-I is correct: Photochemical smog (Los Angeles type) requires sunlight to react with Nitrogen Oxides (NOx) and Volatile Organic Compounds (VOCs) to create Ozone and PAN. It thrives in dry, sunny heat.
• Statement-II is correct: Classical smog (London type) is sulfurous. It forms from burning coal (sulfur) in humid, foggy, cold weather.
• Both statements are factually true descriptions of different phenomena. However, Statement II does not explain Statement I. They are contrasting types of smog.