Shapes of granular surfaces

We present experimental and theoretical studies of the shape of heaps. In the simplest case one has a cone with an angle of repose. A simple 1d model is presented and solved analytically to obtain this angle from the properties of individual grains. This model is generalized to take into account segregation of different types of particles, in particular the spectacular stratification patterns. Using translational invariance one can calculate the deviations from a linear shape and obtains logarithmic tails which have also been evidenced experimentally either for heaps on a flat table or in a 2d silo. Experiments give in addition the dependence of the tails on the flux and energy of incoming grains and on the width of the silo. We will also discuss the rounding of the top of a heap and the shape of dunes, i.e. the effects of wind.