Mountain-encircled Esthwaite Water in the Lake District of northwestern England.Tom Wright/FPG
The Cambrian Mountains, which form the core of Wales, are clearly defined by the sea except on the eastern side, where a sharp break of slope often marks the transition to the English lowlands. Cycles of erosion have repeatedly worn down the ancient and austere surfaces. Many topographic features derive from glacial processes, and some of the most striking scenery stems largely from former volcanism. The mountain areas above 2,000 feet (610 metres) are most extensive in North Wales. These include Snowdonia—named for Snowdon (Yr Wyddfa), the highest point in Wales, with an elevation of 3,560 feet (1,085 metres)—and its southeastern extensions, Cader Idris and Berwyn. With the exception of Plynlimon and the Radnor Forest, central Wales lacks similar high areas, but the monadnocks of South Wales—notably the Black Mountains and the Brecon Beacons—stand out in solitary splendour above the upland surfaces. There are three such surfaces: a high plateau of 1,700 to 1,800 feet (520 to 550 metres); a middle peneplain, or worn-down surface, of 1,200 to 1,600 feet (370 to 490 metres); and a low peneplain of 700 to 1,100 feet (210 to 340 metres). These smooth, rounded, grass-covered moorlands present a remarkably even skyline. Below 700 feet (210 metres) lies a further series of former wave-cut surfaces. Several valleys radiate from the highland core to the coastal regions. In the west these lowlands have provided a haven for traditional Welsh culture, but the deeply penetrating eastern valleys have channeled English culture into the highland. A more extensive lowland—physically and structurally an extension of the English lowlands—borders the Bristol Channel in the southeast. The irregularities of the 600-mile (970-km) Welsh coast show differing adjustments to the pounding attack of the sea.
Coastline, Pembrokeshire Coast National Park, Wales.James P. Rowan
The South West—England’s largest peninsula—has six conspicuous uplands: Exmoor, where Dunkery Beacon reaches an elevation of 1,704 feet (519 metres); the wild, granite uplands of Dartmoor, which reach 2,038 feet (621 metres) at High Willhays; Bodmin Moor; Hensbarrow; Carn Brea; and the Penwith upland that forms the spectacular extremity of Land’s End. Granite reappears above the sea in the Isles of Scilly, 28 miles (45 km) farther southwest. Despite the variation in elevation, the landscape in the South West, like that of so many other parts of the United Kingdom, has a quite marked uniformity of summit heights, with a high series occurring between 1,000 and 1,400 feet (300 and 430 metres), a middle group between 700 and 1,000 feet (210 and 300 metres), and coastal plateaus ranging between 200 and 400 feet (60 and 120 metres). A network of deep, narrow valleys alternates with flat-topped, steplike areas rising inland. The South West derives much of its renowned physical attraction from its peninsular nature; with both dramatic headlands and magnificent drowned estuaries created by sea-level changes, the coastline is unsurpassed for its diversity.
Exmoor National Park, West Somerset, EnglandHeather-covered hills in Exmoor National Park, West Somerset, England.A.F. Kersting
The lowland zone
Gauged by the 700-foot (210-metre) contour line, the lowland zone starts around the Solway Firth in the northwest, with a strip of low-lying ground extending up the fault-directed Vale of Eden (the valley of the River Eden). Southward the narrow coastal plain bordering the Lake District broadens into the flat, glacial-drift-covered Lancashire and Cheshire plains, with their slow-flowing rivers. East of the Pennine ridge the lowlands are continuous, except for the limestone plateau north of the River Tees and, to the south, the North York Moors, with large exposed tracts that have elevations of more than 1,400 feet (430 metres). West of the North York Moors lies the wide Vale of York, which merges with the east Midland plain to the south. The younger rocks of the Midlands terminate at the edge of the Cambrian Mountains to the west. The lowland continues southward along the flat landscapes bordering the lower River Severn, becomes constricted by the complex Bristol-Mendip upland, and opens out once more into the extensive and flat plain of Somerset. The eastern horizon of much of the Midland plain is the scarp face of the Cotswolds, part of the discontinuous outcrop of limestones and sandstones that arcs from the Dorset coast in southern England as far as the Cleveland Hills on the north coast of Yorkshire. The more massive limestones and sandstones give rise to noble 1,000-foot (300-metre) escarpments, yet the dip slope is frequently of such a low angle that the countryside resembles a dissected plateau, passing gradually on to the clay vales of Oxford, White Horse, Lincoln, and Pickering. The flat, often reclaimed landscapes of the once-marshy Fens are also underlain by these clays, and the next scarp, the western-facing chalk outcrop (cuesta), undergoes several marked directional changes in the vicinity of the Wash, a shallow arm of the North Sea.
The chalk scarp is a more conspicuous and continuous feature than the sandstone and limestone outcrops farther west. It begins in the north with the open rolling country known as the Yorkshire Wolds, where elevations of 750 feet (230 metres) occur. It is breached by the River Humber and then continues in the Lincolnshire Wolds. East of the Fens the scarp is very low, barely attaining 150 feet (45 metres), but it then rises gradually to the 807-foot (246-metre) Ivinghoe Beacon in the attractive Chiltern Hills. Several wind gaps, or former river courses, interrupt the scarp, and the River Thames actually cuts through it in the Goring Gap. Where the dip slope of the chalk is almost horizontal, as in the open Salisbury Plain, the landscape forms a large dissected plateau with an elevation of 350 to 500 feet (110 to 150 metres). The main valleys contain rivers, while the other valleys remain dry.
Chalk cliffs of Flamborough Head on the North Sea, East Riding of Yorkshire, northern England.© Martin Priestley/Getty Images
The chalk outcrop continues into Dorset, but in the south the chalk has been folded along west-to-east lines. Downfolds, subsequently filled in by geologically recent sands and clays, now floor the London and Hampshire basins. The former, an asymmetrical synclinal (or structurally downwarped) lowland rimmed by chalk, is occupied mainly by gravel terraces and valley-side benches and has relatively little floodplain; the latter is similarly cradled by a girdle of chalk, but the southern rim, or monocline, has been cut by the sea in two places to form the scenic Isle of Wight.
Between these two synclinal areas rises the anticlinal, or structurally upwarped, dome of the Weald of Kent and Sussex. The arch of this vast geologic upfold has long since been eroded away, and the bounding chalk escarpments of the North and South Downs are therefore inward-facing and enclose a concentric series of exposed clay vales and sandstone ridges. On the coast the waters of the English Channel have undermined and eroded the upfold to produce a dazzling succession of chalk cliffs facing the European mainland, 21 miles (34 km) distant at the Strait of Dover, the narrowest part of the English Channel. Drainage
River SevernRiver Severn at Shrewsbury, Shropshire, Eng.Chris Bayley
River Dee River Dee, near Braemar, Scotland.Deus ExThe main drainage divide in Great Britain runs from north to south, keeping well to the west until the basin of the River Severn. Westward-flowing streams empty into the Atlantic Ocean or Irish Sea over relatively short distances. The Clyde in Scotland, the Eden and Mersey in northwestern England, and the Dee, Teifi, and Tywi in Wales are the only significant westward-flowing rivers north of the Severn estuary. The drainage complex that debouches into the Severn estuary covers a large part of Wales and the South West and West Midlands of England. To the south the Avon (flowing through Bristol) and the Parret watershed extend somewhat to the east, but subsequently, with the exception of the Taw and Torridge valleys, they run very close to the western coast in Devon and Cornwall.