Earth, Electrical conductivity

The electrical conductivity at the Earth's surface is extremely variable and is largely dominated by the presence of water. Laboratory measurements, for example, show that the conductivity of seawater is close to four siemens per metre (S/m; or a resistivity of 0.23 ohm-metre), whereas dry rock exhibits conductivities in the range 10-11 to 10-9 siemens per metre. When water is present