Final answer:
The normal lithostatic pressure gradient is around 22.6 MPa/km, which is caused by the weight of overlying rocks and increases consistently with depth.
Step-by-step explanation:
The normal lithostatic pressure gradient is approximately 22.6 MPa per kilometer of depth (more simply about 1 kilogram-force per square centimeter per 100 meters of depth). This pressure is a result of the weight of the overlying rock and is thought of as the stress exerted by the rocks above a certain depth. The lithostatic pressure increases consistently with depth, and it's important to differentiate between this type of pressure and fluid pressures, which may vary with fluid densities.