Cuillin in colour, particularly in the shade, but when in sunlight the Black Cuillin can appear grey to brown in colour. The main ridge forms a narrow crest, with steep cliffs and scree slopes. The ridge is about 14 km long (measured from Gars-behinn in the south to Sgùrr nan Gillean in the northeast), and curves in an irregular semi-circle around Loch Coruisk, which lies at the heart of the range. The highest point of the Cuillin, and of the Isle of Skye, is Sgùrr Alasdair in the Black Cuillin at 992 m (3,255 ft). The Red Cuillin are mainly composed
Cheviot Hills they are separated from the Cheviot Hills by the Tyne Gap, part of which lies within the southern extent of the Northumberland National Park. The Cheviot Hills are primarily associated with geological activity from approximately 480 to 360 million years ago, when the continents of Avalonia and Laurentia collided, resulting in extensive volcanic activity (the Caledonian orogeny) which created a granite outcrop surrounded by lava flows. The area enjoys a general right to roam under both the English Countryside and Rights of Way Act 2000 and the Scottish Land Reform (Scotland) Act 2003. The Southern Cheviots include the Otterburn Training