1. n. [Geology]

The pore pressure of rocks that is considered normal in areas in which the change in pressure per unit of depth is equivalent to hydrostatic pressure. The normal hydrostatic pressure gradient for freshwater is 0.433 pounds per square inch per foot (psi/ft), or 9.792 kilopascals per meter (kPa/m), and 0.465 psi/ft for water with 100,000 ppm total dissolved solids (a typical Gulf Coast water), or 10.516 kPa/m.

See: abnormal pressure,  formation pressure,  geostatic pressure,  hydraulic head,  hydrostatic pressure,  lithostatic pressure,  pore,  pore pressure,  pressure gradient,  underpressure,  virgin pressure