Gravity surveys are geophysical methods used to measure variations in the Earth's gravitational field. These variations can indicate the presence of different geological structures, such as minerals, oil, or natural gas. By analyzing the data collected from these surveys, scientists can infer the density and distribution of subsurface materials. During a gravity survey, sensitive instruments called gravimeters are used to detect tiny changes in gravity at various locations. The data is then processed to create maps that help geologists and engineers understand the underlying geology, which is essential for resource exploration and environmental studies.