Hohentwiel, a volcanic neck on the outskirts of Singen, southern Germany. During the Pleistocene Epoch, a large piedmont glacier repeatedly advanced from the Alps towards this area. In this view the ice flow was from right (East) to left (West). The neck resisted glacial erosion better than the pyroclastic deposits around it. Till was deposited preferentially on the lee side of the neck, forming the gentle slope on the left. Photo J. Alean 2006.