Numerical and approximate solutions for lithospheric thickening and thinning

Lithospheric thickness, surface heat flow and subsidence are calculated numerically as functions of time since the formation of oceanic lithosphere at a ridge crest. These numerical results confirm the validity of a previously derived approximate solution to the same problem. A numerical solution is also calculated for lithospheric thinning due to a sudden increase of heat flux into the base of the lithosphere. With this solution as a standard, an approximate solution is derived which can accurately predict thickness, heat flow, and uplift as functions of time. Lithospheric thinning and surface uplift begin immediately with the increase of heat flux at depth, but the increase in surface heat flow begins 20–40 m.y. later.