New data structure for visual simulation of 3D terrains is introduced. The representation is inspired by real geological measurements and presents good trade-off between commonly used inexpensive, but inaccurate, height fields and memory demanding voxel representation. The representation is based on horizontal stratified layers consisting of one material. The layers are captured in some positions of the landscape that is discretized into 2D array. We demonstrate that the classical algorithm simulating thermal erosion can run on this representation and we can even simulate some new properties. The simulation has been done on artificial as well as on real data.