One of the most important drivers of the movement of landforms is movement of the geology underlying the landform. Tectonic uplift provides the initial elevation that is then eroded away by the landforming processes discussed in following chapters. These tectonic forcings observed at and near the land surface are largely driven by interactions between the crust and the underlying mantle. The flow processes in the mantle lift, tilt, warp and translate the overlying geology and the land surface responds accordingly. It is these latter land surface responses that are our primary interest in this book, but to understand them fully we do need to understand how the mantle drives them (even if we don’t model the mantle explicitly, that being the primary domain of the field of geodynamics). Our focus will not be on how the mantle drives the landforms but how the mantle responds to landform changes, and how that in turn influences the landform evolution into the future: i.e. the interaction between the landforms and the crust-mantle system.