THE UNITED KINGDOM United Kingdom, comprising the two large islands of Great Britain and Ireland, along with about 5,000 smaller islands lying off their shores, stands upon the continental platform, off the north west coast of Europe. As indicated in the previous chapter, the geographical and geological characteristics of the region are exceed ingly varied and complex. The north and west of Great Britain consist in the main of mountainous land built up of older rocks, while the south and east are generally lowlands, in which the younger formations prevail. As these differences in physical structure have had a great influence upon the economic development of the whole country, a more detailed examination of them is necessary.
Scotland may be divided into three great physical regions—the Northern Highlands, the Central Lowlands, and the Southern Uplands. The Central Lowlands, which separate the first of these regions from the last, consist of a great rift valley, caused by two lines of fracture, one running limn Stonehaven in the east to the mouth of the Clyde in the west, and the other from Dunbar in the east to Girvan in the west. The Northern Highlands, which have an average elevation of about 1,500 feet, are in the main a great dissected tableland, probably formed of Cambrian rocks, which have been completely altered by metamorphic action. In the Outer Hebrides and on the west coast, ancient ArcIman rocks and pre-Cambrian sandstones appear ; in the central part of the High lands there are considerable areas of intrusive granite, and in the Inner Hebrides extensive volcanic outpourings of Tertiary age. In Caithness in the extreme north, and along the eastern margin of the Highlands as far as the mouth of the Moray Firth, there is a low-lying coastal sill of varying width, formed mainly of Old Red Sandstone. This lowland area broadens out in north-east Scotland, but is there composed in the main of rocks similar to those of the Highlands. The Southern Uplands consist of Silurian rocks, and, like the Northern Highlands, their structure is that of a dissected tableland, but their average height is less, and probably does not exceed 1,000 feet. The Central Lowlands, which have been let down between these two ancient masses, and folded in the process, are generally covered with Old Red Sandstone and Carboniferous rocks, except in the upland districts, which owe their formation to volcanic matter ejected in Carboniferous times.
England is divided into two very different physical regions by a height of land known as the oolitic escarpment, which extends from Portland Island, by the Cotswolds, to the North Yorkshire Moors. To the north and west of this escarpment lie the great
Palaeozoic areas of the country, while to the south and east of it are the Secondary and Tertiary formations. The Palmozoic areas —the Pennine Range, the Lake District, the Welsh Upland, and the peninsula of Devon and Cornwall—are united by the Central Plain, which lies between them and the oolitic escarpment. The Pennine range was built up of folded Carboniferous rocks,—Moun taM Limestone, Millstone Grit, and Coal Measures,—but denu dation has removed the Coal Measures, and in many places the Millstone Grit, from the upper parts of the range. The Coal Measures, however, appear on both flanks, in Lancashire on the west, and in Northumberland and Durham, Yorkshire, Derbyshire, and Nottinghamshire on the east. The Lake District is a dome shaped uplift, formed of Silurian and igneous rocks, with a band of Coal Measures along the north-west coast. The Welsh Upland is a dissected plateau of Cambrian and Silurian rocks, strengthened in places by intrusive igneous material. In the south, in a'synclinal trough in the Silurian rock, there are areas of Old Red Sandstone and Carboniferous rocks within the last of which lies the coal basin of South Wales. The peninsula of Devon and Cornwall consists of a synclinal trough in the Old Red Sandstone, which appears in the north along the Bristol Channel, and in the south along the English Channel where there are also considerable areas of intrusive granitic rocks. The country between these outcrops of Old Red Sandstone is covered with lower Carboniferous rocks, which, however, do not contain coal. The Central Plain, which connects these various upland regions, is composed in the main of Permian, Triassic, and Liassic rocks, though in some parts of the south the Coal Measures come to the surface. From the oolitic escarpment, which bounds the Central Plain, the land slopes gently away eastwards and southwards across the Jurassic belt to the foot of the Cretaceous escarpment, which runs from the Dorset Downs, by the Marlborough Downs, the Chilterns, the East Anglian Heights, and the Lincoln shire and Yorkshire Wolds, to Flamborough Head. This escarpment bounds the chalk country which extends eastward and southward until it is overlaid by the Tertiary gravels and clays of the London and Hampshire basins.