Which survey measures density variations to detect kimberlite or lamproite?

• A. Aerial photography
• B. Magnetic surveys
• C. Gravity surveys
• D. Seismic surveys

Answer: (C)

Gravity surveys are used to map density differences in the subsurface. Kimberlite and lamproite bodies often have a different density (and sometimes porosity) compared with surrounding crustal rocks, so they create detectable gravity anomalies. By measuring tiny variations in the Earth's gravity field, geophysicists can infer where such density contrasts occur and pinpoint possible buried pipes, then drill for confirmation.

Aerial photography shows surface features, magnetic surveys map magnetic properties, and seismic surveys measure how sound waves move through rocks (elastic properties). None of these directly measure density variations the way gravity surveys do, which is why gravity is the best choice for detecting kimberlite or lamproite.