The dynamics of soil development and erosion is studied through a stochastic soil mass balance in which the soil production by bedrock weathering is expressed as a state-dependent deterministic function, while the erosion by landslides is modeled as a marked Poisson process. For a range of values of the parameters the dynamics is bistable and the noise drives the transitions from a state to another through a potential barrier. The rates of such a transition are analytically estimated and their dependence on the system parameters is briefly discussed. ¿ 2001 American Geophysical Union