How do the density variations of subsurface masses express themselves?
The answer to this question is particularly important for geophysical exploration of natural resources, such as oil, gas, minerals, etc. However, gravity maps also help to delineate and understand active crustal fault regions, contour the “topography” of the ocean bottom, and help to monitor ocean currents.
In each case, the spatial variations of gravity are a direct consequence of subsurface mass variations. Understanding these varia tions and how they change in time is also extremely important in regions of active volcanoes where subsurface mass changes is one of the warning signals for an imminent eruption