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Q141. The P-wave velocity of the earth's mantle at the Mohorovicic discontinuity is approximately:
The Mohorovicic discontinuity (Moho) represents the crust-mantle boundary where P-wave velocity jumps sharply to about 8.0-8.1 km/s.
Q142. The number of hydrous minerals in the Moh's scale of hardness is:
The Mohs scale contains two hydrous minerals: Gypsum (CaSO4ยท2H2O) and Talc (Mg3Si4O10(OH)2).
Q143. Which of the following time boundaries correspond(s) to major mass extinction events?
The Permian-Triassic extinction (The Great Dying) was the most severe, eliminating ~96% of marine species. Cretaceous-Paleogene is also a mass extinction.
Q144. The reflection coefficient at the interface between two layers of resistivities 9 ohm-m and 1 ohm-m respectively is (magnitude):
The reflection coefficient magnitude is |(P2 - P1)/(P2 + P1)| = |(1 - 9)/(1 + 9)| = |-8/10| = 0.8.
Q145. In Mohs' scale of hardness, how many minerals are of silicate composition?
The silicate minerals on Mohs scale are: Talc (1), Orthoclase (6), Quartz (7), and Topaz (8). The others are sulfates, carbonates, oxides, etc.
Q146. Factors governing the inclination of the slip face of ripples:
The slip face (lee side) maintains the Angle of Repose, which is determined by the internal friction angle of the sediment grains.
Q147. In a region, given the palaeomagnetic inclination (I), the palaeolatitude (lambda) can be calculated using the formula:
The standard dipole equation relating inclination (I) to latitude (lambda) is tan(I) = 2 * tan(lambda).
Q148. Which marine environment is indicated by the benthic foraminifera Quinqueloculina, Ammonia, and Elphidium?
These genera are characteristic of shallow, high-energy Shelf or coastal lagoon environments. They do not inhabit deep ocean (Abyssal/Hadal) zones.
Q149. Why do Li, Be, and B have low cosmic abundance?
These light elements are consumed by nuclear fusion reactions (proton capture) in stellar interiors, a process called astration.
Q150. Factors reducing landslide failure
They increase resisting forces