During the ice age, underground water remained frozen while surface water melted. This forced the flow of meltwater over the surface and formed valleys and waterfalls. When the water could again flow underground, these features remained as dry valleys, cliffs and gorges. The formation of Watlowes Valley in the Yorkshire Dales is explained in terms of surface drainage acting on a frozen landscape as the ice retreated at the end of the last ice age. The relict waterfall at Malham Cove is also visited. Aerial shots of Gordale Scar accompany the explanation of its formation as a meltwater channel.
Students could produce annotated diagrams explaining the formation of gorges and dry valleys. This can be cross referred with glacial features in other areas and upper course river features.