The nonstationary deformation of an infinite thin elastic plate that is symmetrically loaded and floats on a highly viscous liquid is characterized by two similarity parameters and the shape of the load. The first similarity parameter is proportional to the rigidity of the plate and inversely proportional to the fourth power of the radial extent of the load. The second is proportional to the radial extent of the load raised to three halves and inversely proportional to the viscosity of the liquid. The equations describing the deformation of the plate and the motion of the liquid are solved analytically and applied to the rebound of Fennoscandia since the Weichselian glaciation. The corresponding interpretation of uplift data of the lithosphere in Scandinavia implies that the ice cap did not cover the southern part of Scandinavia. Moreover, the calculated flexural stresses of the lithosphere in Sweden are small in those regions where no weak earthquakes occur. ¿ 1999 American Geophysical Union