The upland areas of Britain are the areas of Devonian and Carboniferous rocks folded in the Hercynian earth-movements. Sandstones and limestones, disposed in simple structures, are the principal rock types. The relief, therefore, typically has a pattern, whether it be high-level plateau as in the Pennines, low coastal plateau as in Caithness and the Orkneys, or high escarpment as in the Brecon Beacons, the Black Mountains and the hills inland from Brora in Sutherland. Compared with the highlands the signs of glaciation are far less pronounced. Mantles of drift are common enough and seem to intensify the smoothness of many of the hillsides, but there are, for example, few indisputable corries: the soft rounded forms that occur could be spring-heads, or corries badly preserved in not particularly resistant rocks, or spring-heads modified by snow-patches. Although many parts of the Old Red Sandstone produce acidic, impermeable and infertile soils, the more marly sections form fertile lowland, while the Carboniferous Limestone adds a type of relief, soil and vegetation almost absent from highland Britain. Regional differences occur within the uplands, but the essence of the relief is comparative simplicity of structure allied to a relief of bold cuestas and plateaux.
The Pennines are typical of the high plateaux of upland Britain. Slight dips and great lithological differences both between the major divisions of the Carboniferous rocks and within the Yoredale facies of the Carboniferous Limestone ensure the prevalence of structural surfaces. Whether these surfaces are truly structural or structures approximately stripped by erosion is not fundamental in a general review of this type, for the net result is the same, the dominance of the landscape by tabular relief. In addition, the Carboniferous Limestone is unique in possessing the clearest and most complete karst features in Britain and these are nowhere better developed than in parts of the Pennines, notably around Ingleborough.
Plateau at a much lower elevation is to be found in the coastal areas of Caithness and in the Orkneys, where the rocks responsible for it are the closely bedded Devonian Caithness Flags. A more monotonous scenery than that of parts of inland Caithness would be difficult to imagine, but the coast, where marine erosion has exerted its full effect on jointed and faulted horizontal rocks to produce vertical cliffs and spectacular stacks and inlets, is magnificent.
Where a simple regional dip affects the rocks, striking escarpments and dip slopes, such as those of the Brecon Beacons and Black Mountains, occur. These are impressive features, the crests of the escarpments reaching nearly to 3,000 ft in the former and to 2,500 ft in the latter upland. In form they are magnified versions of the cuestas of lowland Britain, but, apart from the question of scale, they differ from these in the number of steps and scars caused by hard beds, and in the dull colours of their acid moorland vegetation. To the south the Pennant series of grits and sandstones is a very important relief-forming unit in the synclinal upland of the South Wales coalfield: it is responsible for the moorland plateau between the industrial valleys and for a high escarpment overlooking the dissected vale developed on Lower Coal Measures in the northern part of the region.