Final answer:
A negative gravity anomaly suggests a subsurface mass deficit, likely due to lower density materials underground. Gravitational measurements are used to detect such anomalies, providing precise local data on gravitational acceleration.
Step-by-step explanation:
If a gravity anomaly is negative, this generally implies that there is a mass deficit in the underground region relative to the surroundings. Such anomalies can occur due to various geological structures like caverns, lower density sedimentary structures, or extensive deposits of diamagnetic materials, which create a smaller gravitational pull on the surface above these areas.
As gravitational acceleration is affected by the distribution of mass, negative gravity anomalies often indicate materials underground with lower density than the surrounding rock. This can be detected through gravitational measurements, which are sensitive to variations in local geology, including the presence of nearby mountains and different subsurface materials.
Understanding negative gravity anomalies is important for geological and environmental studies, as they aid in mapping underground structures, identifying potential resources, and evaluating seismic risks. Such measurements are often more precise local representations of gravitational acceleration, as they take into account these local geological variations.