Walking in the United Kingdom the scrambling suddenly becomes much more serious. In Britain, the term "mountaineering" tends to be reserved for technical climbing on mountains, or for serious domestic hillwalking, especially in winter, with additional equipment such as ice axe and crampons, or for routes requiring rock-climbing skills and a rope, such as the traverse of the Cuillin ridge, on the Scottish island of Skye. The British Mountaineering Council provides more information on this topic. Navigation and map-reading are essential hillwalking skills on high ground and mountains, due to the variability of British and Irish weather and the risk of rain, low cloud, fog
Geology of Skye Part of the magma chambers for the volcanoes are exposed at the surface as major intrusions of gabbro and granite. These coarse-grained igneous rocks are relatively resistant to erosion and now form the Cuillin hills. The Black Cuillin are formed of gabbro, which erodes to form the characteristically jagged outlines, although this is in large part due to the many minor intrusions, such as dykes and cone sheets that cut the gabbro. The Red Hills are formed of granite and have a more rounded topography. All pre-Quaternary rock types on the island are affected by a major swarm of dykes,