Influence on the landscape
Whin Sill at Walltown 
Whin Sill at Sewingshields Crags © BGSThe Devonian lavas and granitic rocks form the massive rounded hills of the Cheviot massif, much of which lies above 300 metres, with the highest point on The Cheviot at 815 metres. The valleys are deep with steepsided convex slopes. The rocks are not well exposed, except in the valley bottoms and on the tors, which characterise the hilltops on the granite, and where the volcanic rocks have been metamorphosed in contact with the granite. Crags are few, though notable exceptions are Bizzle Crags and Hen Hole to the north and west of The Cheviot respectively. In the eastern half of the massif, the drainage pattern that has developed on the igneous rocks is relatively simple and the density of streams is low. This contrasts markedly with that on the western side where the drainage pattern is intricate and dense. The wide, strikingly linear valley of the Harthope Burn has been carved along a major fault through the massif.
The lavas of the Cottonshope Volcanic Formation are marked by small, dark-coloured craggy outcrops which contrast with the surrounding outcrops of Dinantian sedimentary rocks. Small, long-abandoned quarries mark the outcrops. Because of their very small surface outcrop these rocks have only a modest effect of the district’s landscape.
The Whin Sill-swarm is one of the best known features of Northumberland geology and is responsible for some of the county’s finest, and most distinctive scenery. The north-facing cliffs, with the long, gentle southerly slopes, provided the Roman civil engineers with a natural defensive site for the construction of Hadrian’s Wall. The massive, hard and resistant columnar-jointed dolerite imparts a distinctive character to these outcrops, which contrasts strikingly with the generally lower ridges and crags (cuestas) formed by parallel outcrops of Carboniferous sandstone and limestone.
The Great Whin Sill was formerly worked on a large scale in quarries at Walltown and Cawfields. Landscaping of the former site has significantly lessened its visual impact as a man-made feature. In contrast, the profile of Cawfields Quarry stands as an obvious interruption to the line of Whin Sill crags. Both quarries offer opportunities to appreciate the nature of the Whin Sill and its role in creating the distinctive landscape of the Hadrian’s Wall country. The crags at Steel Rigg and elsewhere are popular rock climbing localities. East and north of Sewingshields the Whin Sill outcrops are locally concealed beneath spreads of superficial deposits. However, steep escarpments with bare crags of dolerite can be seen at Teppermoor Hill, around Gunnerton Nick and in the Swinburne, Thockrington, Sweethope, Bavington, Fontburn and Kyloe areas. Large working quarries at Keepershield, Barrasford, Swinburne, Divethill, Howick and Longhoughton are conspicuous features in the local landscape, though their visual impact is subject to strict planning and environmental constraints. There are also abandoned quarries at Thockrington, West Whelpington, Ward’s Hill and Ewesley.
Neither the Carboniferous, nor the Cainozoic dykes make any significant impact on the district’s landscape; small long-abandoned quarries are still visible in the Acklington Dyke near Cartington.
