The relative dating of layers of rocks is aided by more then a principle of stratigraphy. Nevertheless, there is one that may be considered the main basic principle utilised to aid on this task - the Law of Superposition, which indicates that, when in undisturbed strata, the oldest rock layer lays at the bottom, whereas the youngest rock layer lays at the top. All other layers that may exist in between follow this same pattern of old to young from bottom to top.