of Devonian rocks on Anglesey too. Carboniferous The Carboniferous period is represented by extensive outcrops across South Wales from the Wye Valley in the east, through the South Wales Coalfield, the Vale of Glamorgan and Gower westwards to southern Pembrokeshire. There are less extensive areas in northeast Wales and along the north coast into Anglesey where similarly aged rocks characterize the landscape. The sequence includes Carboniferous Limestone at its base, followed by coarse sandstones (The ‘Millstone Grit’ of the north and the ‘Twrch Sandstone’ of the south), then mudstones and finally the Coal Measures which comprise a thick succession of mudstones, sandstones and of course coal seams. Limestone Though mid Wales lay above sea level during Carboniferous times, shallow tropical seas extended across much of north and south Wales and it was in these environments that a succession of types of limestone were deposited. The limestone gives rise to impressive cliffed landscapes both on the coast as at the Great Orme in the north and at St Govan's Head and the Gower Peninsula in the south, and inland at the escarpments of Eglwyseg Mountain near Llangollen and Llangattock hillside in the Usk Valley. Karst landscapes characterize the limestone outcrop and, particularly along the ‘north crop’ of the South Wales Coalfield basin, where the limestone is shallowly buried beneath adjacent sandstones, extensive development of solution hollows has taken place. Namurian sequence The Namurian age mudstones and sandstones which overlie/succeed the limestone give rise to rugged landscapes; typically either poorly drained moorland or else wooded gorges as in the Waterfall Country of southern Powys. Coal Measures Landscapes developed over Coal Measures rocks are extensively altered by man, as the coal and iron found within this thick sequence of rocks have long been economically important, particularly since the Industrial Revolution. The former coalfields of Flintshire, Denbighshire and South Wales are witness to this period. In South Wales, the Coal Measures are overlain by the thick sandstones of the Pennant Measures which often provides craggy edges to the plateau which has been deeply dissected to form the South Wales Valleys. The Pennant Sandstone is widely used as a building stone. A major geological feature of the Upper Carboniferous sub-period in South Wales is the South Wales Coalfield syncline. The rocks comprising this important area were laid down during the Westphalian Age approximately 314-308 million years ago (Ma), when climatic conditions were equatorial. This Westphalian