Using our knowledge about convective processes and the heat flow estimated by Reynolds and Cassen (1979), we find for the outer Gailiean satellites that the mean temperature within the convecting ice crust is about 180¿ K. The time scale of convection, thought to be a measure of a period of tectonic activity, is of order 5 million years and the velocities of order of 1--20 cm per year depending on the thickness of the convecting layers (50--1000 km). The thickness of the conducting upper layer is estimated to be of order 30 km. Due to low temperatures T at the surface and strong dependence of the viscosity on T, the time scale of smaller topographic features is estimated after Johnson and McGetchin (1973) to be of order from several hundred million years to several billion years. It is proposed that comparatively short tectonic processes, repeating every few million years, may serve as an erosion factor in shaping the form of the surfaces.