The geometry of sediment fill within oceanic trenches will always tend toward dynamic equilibrium, such that there is no net sediment flux in or out of the system. By assuming a steady state trench wedge geometry, an unknown parameter such as sedimentation rate or subduction rate can be determined if the other controlling parameters are known. The application of such a simple technique is of particular use in the deep marine realm where process rates are particularly difficult to measure directly. However, trench systems that have been drilled yield present-day sedimentation rate values that are typically an order of magnitude less than those predicted by the geometrical model, suggesting that modern trench systems are currently decreasing in size following a dramatic decrease in sediment supply at the end of the last cold climatic period. Furthermore, for large accretionary complexes to have been built, average Cenozoic trench sedimentation rates must have been far greater than those observed today.