geophysics: The study of the physical properties of the earth -- structure, composition, and development -- such as magnetism, radioactivity, vulcanism, etc. Its applications to archaeology have been to provide dating methods (geochronology) and techniques for exploration (magnetometer and resistivity survey). Some dating techniques, e.g. palaeomagnetism, are based on geophysical properties of the earth. It is a subdiscipline of both geology and physics.