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| | Electrical Methods |
 | | Using electrical methods, one may measure potentials, currents, and electromagnetic fields that occur naturally or are introduced artificially in the ground. |
 | | Variations in the resistivity of earth materials, either vertically or laterally, produce variations in the relations between the applied current and the potential distribution as measured on the surface, and thereby reveal something about the composition, extent, and physical properties of the subsurface materials. |
 | | Since the conduction of current in soil and rock is through the electrolyte contained in the pores, resistivity is governed largely by the porosity, or void ratio, of the material and the geometry of the pores. |
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