This picture is taken from the top section of a waterfall on the Hepste river. It can be clearly seen the hard wearing millstone grit rock in sections on the side showing where the water has eroded away the much softer shale or mud stone from in between. This leaving the gaps between the seperate layers of millstone. This softer rock being exposed and eroded by the waters action has coursed the collapse of rocks in the section of the waterfalls gorge.