The parent material is one of the fundamental parameters that define the landscape. There are 11 major alluvial plains in the Marche region (picture 5). The alluvial deposits are characterized by recent alluvial materials, four levels of ancient fluvial terraces of Pleistocene. The alluvial material, recent and ancient, is with variable texture, from gravel to clay, but it is always calcareous. In the hilly landscape it is possible to identify Pliocene/Pleistocene materials. They are mainly composed of claystone, mudstone, siltstone, clayey and silty flysch and sometimes conglomeratic flysch and marly limestone (picture 6). In these areas the higher clay fraction explains the severer slope instability, presence of shallow soils on steep slopes, a higher risk of erosion and the manifestation of the vertic characteristic of the soils
Other material is represented by sandy flysch (green area in figure 1.8 b) and c). The behaviour of sandy flysch soils is different from the other flysch soils because the land use is predominantly agro-forestry or forest
In the mountainous areas the parent material is consisting of calcareous rock with hard limestone and marly limestone. Due to the permeability of these types of rocks the river network is practically absent; but on the other hand the groundwater circulation is highly developed. The soils present on these parent materials are generally shallow, the stoniness is high but generally the humus is abundant due to the forest litter.
In the hilly areas calcisols, soils with a significant redistribution of calcium carbonate, are abundant (19 %). Phaeozems (12 %) with shallow horizons and rich in organic matter are typical in pastures and natural vegetation in mountainous areas. Leptosols (8 %), lightly covering rocks, are concentrated in the high mountainous areas of the Sibilini. In the Montefeltro area (mountainous area in Pesaro province) there is a presence of soils with vertic characteristics (1 %) on clayey substrate. Luvisols, soils with a differentiated soil profile and a presence of a clayey alluvial horizon cover also 1 % of the region, province and pedological region.