This paper introduces Ocelet, a domain specific language and simulation tool for modelling changes in geographical landscapes. It is characterised by the use of interaction graphs (graphs with interaction functions on their edges) to represent the system as composed of processes, each involving several entities distributed in space that are in interaction with each other. Entities are the vertices of the graphs, and interactions are the edges on which (interaction) functions can be applied to make the system change through time. Examples are given to illustrate the generic disposition of the simulation approach to model and study changing geographical setups.