To the south east of the Sambre-and-Meuse furrow, geological history gave rise to an intricate pattern of rock type distributions and marked differences in landscape and relief, often within relatively small areas. Periods of mountain building followed by periods of erosion have also had a profound influence on the landscape. Along the river Meuse, limestone from the Dinantian (Carboniferous) alternates with schists and sandstones from the Westphalian (Carboniferous). The Condroz landscape is characterized by an alternation of crests (called locally ‘tiges’ or ‘tiennes’) and depressions (called locally ‘chavées’) which run southwest to northeast. On the anticlines of the crests, the micaceous sandstones from the Famennian (Higher Devonian) are relatively resistant to erosion. The synclines of the depressions are made of calcareous stones from the Dinantian (Carboniferous) that are much softer and susceptible to erosion. Schists of the Famennian are characteristics of the Fagnes to the west of the river Meuse and of the Famenne to the east of the river. Since these schists are relatively soft (frost sensitivity), erosion created a depression in these two regions. The soils of the Famenne depression are made of silt-clay formations deriving from schists from the Frasnian and mostly from the Famennian (both from Higher Devonian). These formations produced wet and nutrient-poor soils. The southern strip of the Famenne, the ‘Calestienne’, is made of Devonian limestone. To the southeast, the Lower Devonian schists and sandstones outcrop in the Ardenne anticlinorium. There is no limestone in Ardenne.