A critical summary regarding the spatial and genetic relationship between ripples, dunes and draas developed on ergs in presented. It is proposed that these aeolian bedforms follow a geometrical fractal arrangement at different scales, in response to the chaotic atmospheric circulation system responsible for their origin. A geometrical model is presented to describe the relation between number of features, its average dimension and the fractal dimension for the set This relation may be useful for describing and representing actual geomorphic features giben their relative dimensions and numbers. It is also discussed the possibility that such features may reflect a statistically fractal development in time. If this is the case, it would be possible to predict, on a wide time scale, the future development of ergs or, going back in time, to set a geochronology for them.
