Three mechanisms transport electric charge through earth materials:
Ions move through pore water (dominant in most rocks).
Notice how the large, slow positive (+) and negative (-) ions migrate through the fluid-filled pores.
Electrons move through conductive minerals (metals, graphite).
Tiny electrons (e⁻) zip rapidly through a continuous solid vein of conductive mineral.
Polarization effects (important for SIP).
Charges do not flow continuously. Instead, molecules polarize (stretch and align) in response to the field.