This website is made to help students prepare for their competitive exams with ease and confidence.
Q121. For earthquakes of magnitudes 6 and 7, the seismic wave amplitudes are A6 and A7. Which is true?
Richter magnitude is logarithmic base-10 for amplitude. A magnitude increase of 1 corresponds to 10x amplitude. (Note: Energy increases by ~32x).
Q122. On a photo-scale of 1:40,000, a square shaped open cast coal mine of 1 sq. km area would have an image area of (in sq. cm):
Scale ratio is 1/40,000. Area scale is (1/40,000)^2. 1 sq km = 10^10 sq cm. Image Area = 10^10 / 16*10^8 = 6.25 sq cm.
Q123. Which one of the following geophysical methods can provide information on deep Earth structures (of the order of 1000 km) with highest resolution?
Seismic tomography uses earthquake waves to image deep Earth structures with much higher resolution than potential field methods (gravity/magnetic).
Q124. Which logging technique is most suitable to detect a shale layer sandwiched between two sandstone layers?
Shale contains naturally radioactive elements (K, U, Th), resulting in a high Gamma Ray count compared to clean sandstone.
Q125. The following gamma ray (GR) log data are recorded: GR log = 30 API, Max GR = 45 API, Min GR = 20 API. What is the fraction of shale?
Shale fraction (Vsh) is calculated as (GR_log - GR_min) / (GR_max - GR_min). Calculation: (30 - 20) / (45 - 20) = 10 / 25 = 0.4.
Q126. Which one of the following parent-daughter systems has the longest half life?
Sm-147 has a half-life of approx 106 billion years. Rb-87 is ~49 billion years. K-40 is ~1.25 billion years.
Q127. Select the option that lists oxide minerals only.
Spinel (MgAl2O4), Corundum (Al2O3), and Rutile (TiO2) are all oxides. Olivine is a silicate; Galena is a sulfide; Fluorite is a halide.
Q128. The metamorphic facies diagnostic of a subduction zone is:
Subduction zones create unique High-Pressure/Low-Temperature conditions, which lead to the formation of Blueschist facies rocks.
Q129. It takes approximately how many seconds for sunlight to reach the Earth?
Sunlight takes about 8 minutes and 20 seconds to travel the distance from the Sun to the Earth.
Q130. The S-wave shadow zone of the Earth ranges from:
S-waves cannot travel through the liquid outer core, creating a shadow zone from 103 degrees on one side to 103 degrees on the other (effectively 103-180).