UPSC Static Quiz – Geography : 26 March 2026

Solution: C

The International Astronomical Union (IAU), through its Resolution B5 adopted in 2006, formally defined the category of “dwarf planets” to distinguish them from classical planets and smaller Solar System bodies.

According to this resolution, a dwarf planet must satisfy four specific conditions, out of which three must be fulfilled and one explicitly not fulfilled:

• Statement 1 is correct: A dwarf planet must be in orbit around the Sun. This condition differentiates dwarf planets from exoplanetary bodies or free-floating objects.
• Statement 2 is correct: A dwarf planet must not be a satellite. This excludes large moons such as Ganymede or Titan, even though they may be spherical and massive.
• Statement 3 is incorrect: A dwarf planet does not clear the neighborhood around its orbit. Clearing the orbital neighbourhood is a defining requirement for a full-fledged planet, not for a dwarf planet. The failure to meet this criterion is precisely why bodies like Pluto were reclassified.
• Statement 4 is correct: The body must have sufficient mass for its self-gravity to overcome rigid body forces, allowing it to achieve a nearly round shape, known as hydrostatic equilibrium. This criterion separates dwarf planets from irregularly shaped asteroids.

Solution: D

• Differential Weathering:This occurs when different parts of a rock mass or different rock layers weather at different rates due to variations in mineral composition or structure (joints/cracks).
• Inselbergs:These are isolated hills or ridges rising abruptly from a plain (e.g., Uluru). They are remnant masses of hard rock that resisted weathering and erosion while the surrounding softer plains were lowered.
• Mushroom Rocks:Common in deserts, these form when wind abrasion (and weathering) erodes the softer lower section of a rock pillar faster than the harder top section, or where moisture creates more weathering at the base.
• Tors:These are piles of exhumed core stones (usually granite) that remain after the surrounding weathered material (regolith) has been stripped away. They form because the jointed areas weathered faster than the solid core blocks.
• All three are products of differential resistance to weathering agents.

Solution: C

• Silver iodide is widely used in cloud seeding because of its unique crystallographic properties rather than any hygroscopic, thermal, or surface-chemical effects. The crystalline lattice of AgI closely resembles that of natural ice, particularly in its hexagonal structure. This similarity allows AgI particles to act as highly efficient ice-nucleating agents in supercooled clouds, where liquid water droplets remain unfrozen below 0 °C due to the absence of suitable nuclei.
• When introduced into such clouds, AgI provides artificial freezing nuclei, triggering the Bergeron–Findeisen process. Ice crystals grow rapidly at the expense of supercooled water droplets because the saturation vapor pressure over ice is lower than over liquid water.
• As these ice crystals grow, they aggregate and eventually fall as snow or melt into rain. Cloud seeding does not significantly alter humidity, heat the cloud, or reduce surface tension; its effectiveness depends on microphysical phase changes driven by ice nucleation under conditionally unstable or moist environments.

Solution: C

• The distinction is based on Visibility.
• Fog:Defined as an obscuration where visibility is reduced to less than 1 km (1000 meters). It creates a significant hazard for aviation and transport.
• Mist:Defined as an obscuration where visibility is between 1 km and 2 km (or simply at least 1000 meters).
• Mist typically involves smaller water droplets and often occurs at lower relative humidity (though still high) compared to the near-saturation of fog.

Solution: D

The Coral Triangle is a specific scientific and conservation designation covering six countries (the “CT6”).

• The CT6 Members: Indonesia, Malaysia, Papua New Guinea, Philippines, Solomon Islands, and Timor-Leste.
• Australia: While Australia possesses the Great Barrier Reef (which borders the Coral Triangle), the Australian continent itself is technically south of the designated Coral Triangle boundary. The Triangle focuses on the archipelagic waters of Southeast Asia and Melanesia.