Geophysical methods respond to the physical properties of objects and materials below the surface (rocks, sediments, voids, water, etc.). In applied geophysics active and passive prospecting methods are employed.

Active methods artificially produce an electrical, electromagnetic, or acoustic signal that is transmitted into the ground. Variations in the subsurface interact with and modify these signals according to their specific physical properties, producing an altered return signal that is measured by instrumentation at the surface. Resistivity methods inject an electrical current, soil conductivity meters transmit radio energy, and ground penetrating radar sends a microwave pulse; in each case the instrumentation measures a response to these actions.

Passive methods detect variations within the natural fields of the earth. They include magnetic and gravitational fields, and certain native electrical properties within the soil. Magnetometry is the principal passive method employed in archaeo-geophysics.

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