We have seen how the old, hard rocks of the Caledonian mountain system form the Scotch Highlands, the Southern Upland of Scotland, the Lake District, Wales, and the Cornwall Peninsula. All alike consist of very ancient rocks, much folded and metamorphosed, which were at one time worn down to a rolling peneplain. Since then they have been uplifted in such a way that in general there is a downward slope of the peneplain from west to east. Thus Ben Nevis, the highest point in Scotland, and Snowden, the highest in Wales, lie close to the west coast, although the most extensive area above 3,000 feet lies east of the center of northern Scotland. A peneplain also extended across the younger rocks of the rest of Great Britain. We have also seen that since its uplift there has been a great amount of erosion, and the softer rocks have been very extensively worn away, especially in the east where they form the vales which are so prominent a feature of England. Nevertheless the old peneplain still remains intact in many places, with the result that all over Great Britain, even in the escarpments that diversify the lowlands, the hills and mountains usually have broad, flat tops. This quality, together with the low temperature, cloudiness, and rain due to their altitude, account for the widespread occurrence of moors, or high, wet, boggy regions.
The Scotch Highlands
Occupying most of Scotland north of latitude 56° on the west and 57° on the east, these Highlands rise abruptly from the sea in the west, but the old peneplain slopes down to a narrow lowland on the east. Seen from a distance the individual mountains of the Highlands have smoothly rounded summits because the surface of the old peneplain still persists. In detail, however, the scenery is very rugged. Not only have the streams cut deep gorges, but the icesheets of successive glaciations have steepened the valley sides, gouged out long, deep hollows that are now filled by lakes or swamps, and carved precipitous cirques higher up. Flat land is so scarce that there is rarely room for more than a few farms. There is not a single town of any importance, except on the lowland close to the sea. The county of Sunderland in the far northwest has only eight people per square mile, and practically all of these are on the coast. About half of the whole region is actually uninhabited and is rarely visited except by shepherds and hunters. The scenery is bleak, though grand. Trees are found only in the more sheltered valleys. Nevertheless, down at the bottoms of the stern valleys some of the lakes and glens are very lovely. Elsewhere, if the slopes do not consist of bare rock or sliding scree, they are largely brown or purple with heather, or else green with grass where the shepherds get rid of the heather in order to have more food for their sheep. So wet are the Highlands and so cool that they are almost wholly covered with moors. If it were not for the sheep that feed on these drizzly moors the Scotch Highlands would be almost completely uninhabited except in the summer when tourists abound in the more picturesque valleys, and in the fall when hunters from England flock northward for deer and grouse.