Soil-mantled landscapes, like the "Mar de Morros" of southeastern Brazil, are characterized by smooth convex hilltops. These forms have been interpreted as characteristic of well-developed landscapes, as the ones prevailing in most of the tropics nowadays. They have also been used to support the classical idea of dynamic equilibrium, implicity proposed by Gilbert and later extended by Hack.

Although the origin of these convex hillslopes have been attributed to the work of diffusive (slope-dependent) processes like creep, rainsplash and biogenic activity, numerical models have shown that baselevel changes, controlled by the incision rate at the base of the profile, also play a major role on controlling the final hillslope curvature. Besides, it is known that equilibrium profiles may be attained on hillslopes evolving, under constant diffusive processes and incision rates (Bd), for a period of time longer than the hillslope relaxation time. However, some of these numerical experiments suggested that the relaxation times for these convex hilltops, when responding to the typical climatic and tectonic oscillations that have occurred along the Quaternary, may be much longer than the frequency of such oscillations, prevailing these hillslope profiles to attain the dynamic equilibrium condition. Although the diffusion coefficient (D) is a key parameter in diffusion-based models of landscape evolution, few studies have tried to estimate it from field investigations.

This study focus on the geomorphological meaning of the smooth convex hilltops of Magé, Rio de Janeiro, based on field investigations and numerical experiments. Detailed curvature profiles were surveyed on many hillslopes and the ratio Bd/D was later estimated. The results showed that this ratio varies inside a small range, from 25 to 130 (x10^-4 m^-1). Because the incision rate and the diffusion coefficient may vary a couple of orders of magnitude, the results presented here do not allow us to neglect the idea of dynamic equilibrium in this area.