Northern Black Forest
Geologically, the dominant rock of the Northern Black Forest is bunter sandstone, although in the deeply incised west its gneiss bedrock reaches the surface. Granites (e.g. Forbach granite) and porphyries have intruded forming crags and tors. The highland regions of the Northern Black Forest are among the regions of the German Central Uplands with the heaviest rainfall (up to 2,200 mm per annum). Its most important rivers are the Murg, Nagold, Enz, Alb, Acher, Rench, Oos and the upper reaches of the Wolf.