In the Earth, the relationship between pressure and depth is controlled by the density of the rocks and the gravitational acceleration at each point along the profile. Gravitational acceleration is almost constant through most of the mantle, though it rises slightly close to the core–mantle boundary, and then decreases linearly to zero at the centre of the Earth. The pressure rises to about 100 GPa at the core–mantle boundary and reaches 375 GPa at the centre of the Earth.