On the way up, there is a hut with a lovely geological model of the area. The lower part of the valley is on Ordivician mudstones which erode more easily.
The highest part is made of volcanic rock.
The falls photographed seem to lie on a fault where magma has got in producing an intrusive igneous rock called microdiorite. This was very hot and has baked the surrounding rock - making metamorphic rock. The result is a harder rock that is more resistant to wear than the surrounding mudstones so there is a step down which the Falls proceed. The model is a wonderful explanation of the landscape.
