GeoGraph - photograph every grid square

Southern buttress on Rhinog Fawr

Looking up steeply at the south face of Rhinog Fawr. Geologically, the Rhinogydd are part of the Harlech dome formation, a wide anticline (strata folded upward) from the Cambrian period which was originally overlaid by the same later Ordovician rock that can be found both on Snowdon and Cadair Idris. This Ordovician material has been eroded away after the Harlech dome formed, leaving the Cambrian sediment exposed. Water, frost and residual stress result in cracking, and the hillsides of the Rhinogydd are covered in rocks of all sizes.