Spahill is the eastern part of the SAC and forms part of an escarpment which connects the Slieveardagh Hills with the Castlecomer Plateau. Spahill is mostly limestone which is exposed in ledges and flat sheets and Clomantagh Hill has a geology which is quite similar to that of Spahill but the summit has an exposure of the overlying sandstone, this looks different from the limestone as it appears as low rocks. The different exposures of rocks over the sites gives rise to differences in the flora which is important because this variety of natural grassland communities has become rare in Ireland as a result of agricultural intensification.