 The sandstones have been quarried in places such as at Allt Lom.The area was overrun by ice during the last ice age and evidence of this is seen in the glacial till which is spread across this undulating plateau and the occasional erratic block of sandstone.Traeth Mawr and Traeth Bach, two rock hollows towards the south-western end of the common are now filled with peat, core sections of which have proved valuable in unravelling the climatic and vegetational history of this area over the last 10,000 years.Walkers can freely access the entire common as it is open access land, though horseriders and mountain-bikers are restricted to the minor roads, restricted byways and bridleways which criss-cross this area.