Question

Variation of Bouguer anomaly obtained along a profile after applying all the necessary corrections is due to:

• A. topographic undulation above the datum plane.
• B. increase in densities of crustal rocks with depth.
• C. lateral density variations.
• D. vertical density contrast across Moho.

Hint:

Bouguer anomalies are primarily used to detect subsurface density contrasts laterally, useful in mineral and petroleum exploration.

Answer 1

The Correct Option is C

Step 1: Recall Bouguer anomaly concept. The Bouguer anomaly is obtained after correcting gravity data for: - latitude, - free-air effect, - Bouguer slab correction (due to elevation), - terrain correction. Thus, Bouguer anomaly reflects mass distribution beneath the surface.

Step 2: What remains after corrections? Once all standard corrections are applied, the residual variations are due to density differences in subsurface rocks (not surface topography or elevation).

Step 3: Interpret options. - (A) Topographic undulation → already corrected. - (B) Increase in densities with depth → general trend, not anomaly cause. - (C) Lateral density variations → correct, causes gravity highs and lows. - (D) Moho contrast → large-scale regional feature, but not local Bouguer anomaly variation.

Final Answer: \[ \boxed{\text{lateral density variations}} \]