
Pen-y-Ghent is made up of a millstone grit top upon a bed of carboniferous limestone.[8] The summit acts as a watershed with water flowing east into the River Skirfare and on through to the Humber Estuary, and water flowing west dropping into the River Ribble, to ultimately flow into the Irish Sea.[9] The distinctive rakes that adorn the hillside (particularly on the western edge of Pen-y-Ghent) were revealed during a great storm in July 1881. The ferocity of the water cascading down the hillside removed the topsoil and revealed the rakes beneath.