Electromagnetic phenomena and electric currents, mostly of natural origin, that are associated with the Earth. Geophysical methods utilize natural and artificial electric currents to explore the properties of the Earth's interior and to search for natural resources (for example, petroleum, water, and minerals). Geoelectricity is sometimes known as terrestrial electricity. All electric currents (natural or artificial, local or worldwide) in the solid Earth are characterized as earth currents. The term telluric currents is reserved for the natural, worldwide electric currents whose origins are almost entirely outside the atmosphere. Geoelectromagnetism is a more comprehensive term than geoelectricity. Time variations of any magnetic field are associated with an electric field that induces electric currents in conducting media such as the Earth.