A gravity survey is a geophysical method used to measure variations in the Earth's gravitational field. By detecting these variations, scientists can infer the presence of different geological structures, such as minerals, oil, or natural gas. The survey involves using sensitive instruments called gravimeters to record gravitational pull at various locations. These measurements help geologists and engineers understand subsurface features and can guide exploration efforts. Gravity surveys are often used in mining, petroleum exploration, and environmental studies to assess the potential for resource extraction or to monitor changes in the Earth's crust.