In geomorphology, a type of dynamic system characterized by the transfer of mass and energy along a chain of component sub-systems, such that the output from one sub-system becomes the input for the adjacent sub-system. An example is the valley glacier, where the inputs of snowfall and rock debris from the slopes above, and potential energy (derived from elevation), are cascaded through a sequence of climatic environments with a progressive reduction in mass and dissipation of energy, the output from the glacier being sediment and water which form the input to the proglacial sub-system.