Note on Penck and Brückner's diagram of the fluvio-glacial series

In their classical studies on the Alpine glaciation Penck and Brückner gave a small blockdiagram to illustrate the arrangement and shape of the deposits at the lower end of a former glacier: the fluvioglacial series. This diagram has been reproduced in so many text-books, that it may be worth-while pointing out a fault in its construction. The case represented by the authors is that of two terminal amphitheatres lying within eachother (fig. 1) 1). The manner in which the outer moraine with its fluvio-glacial fan of sediments is drawn in on top of the inner moraine proves it to be the younger of the two. In this case the glacier must have ridden over the inner circle, thereby destroying its ridge; but in the drawing this ridge is represented as having been left perfectly intact. On the glacier receding again the material of the older moraine would be found buried under the newer deposits, and only one frontal moraine would be left (fig. 2, A).