The collision that assembled Britain at the end of the Silurian (see A history of the plate tectonics of Britain (part 1): Britain assembled – oceans, collisions and the making of a geological patchwork) did not mark the end of tectonic influence on the landscape. Instead, it marked the beginning of a new phase – one that is often less intuitively grasped, but just as important. Mountain belts are temporary features. Once continental collision ceases, thickened crust becomes gravitationally unstable. Erosion strips material from the surface, while extension and faulting affect the deep roots of the orogen. The geological record that follows is not one of rising peaks, but of collapse, subsidence and redistribution.