A sequence of events which have generally been repeated throughout geologic time over the continents of the globe is well illustrated in the Hudson Valley. In the diagrams, northwest is to the left, southeast to the right. A. In a shallow inland seaway thousands of feet of sediment accumulated during the Palaeozoic era. B. Mountain building at the end of the Palaeozoic era produced a series of folds and thrust faults. A general uplifting brought a large mass above sea level. C. Followings long period of erosion, a peneplain was produced. Then faulting in the Triassic produced gently tilted blocks. D. Second long period of erosion resulting in another peneplain. E. The region today owes its relief to different rates of removal of the various kinds of rocks. Strahler, 1960, p. 296.