 The site covers .The Rhosydd Llanpumsaint site is notable for geomorphological features which in turn support special biological features.The site - field and peatland - has on its west side numerous oval depressions of up to diameter thought to have been formed by mineral pillers under permafrost ice which have collapsed on the retreat of the ice, to leave an undulating surface the depressions of which have become sediment and peat filled.