An internationally agreed system of units, which is abbreviated as SI for "Systme International d'Unit's", and is recommended for use in all scientific and technical fields (NBS, 1981). The international system of units is comprised of 7 base units: (1) length in meter (m), (2) mass in kilogram (kg), (3) time in second (s), (4) electric current in ampere (A), (5) thermodynamic temperature in kelvin (K), (6) amount of substance in mole (mol), and (7) luminous intensity in candela (cd). It also has a number of derived and supplementary units. Some derived units with special names are: frequency in hertz (Hz), force in newton (N), pressure or stress in pascal (Pa), energy, work, or quantity of heat in joule (J), power in watt (W), electric charge in coulomb (C), and electric potential in volt (V). See Lide (2002) and NBS (1981) for a detailed review of SI and conversion factors. interplate Interplate pertains to processes between lithospheric plates (See: lithosphere)