Weathering and neoformation of allophane, imogolite and halloysite in volcanic ash soils have been studied extensively in humid climates but little data are available on these soils in arid and semi-arid conditions. Weathering and soil formation under semi-arid conditions on acid pyroclastics have been investigated in two profiles, both at the micr...
Calcareous, neutral and acid red soils, red lateritic soils, latosols and lateritic soils sensu lato are defined on the basis of their mineralogical composition and profile development. Their geographical distribution is discussed. Their origin is interpreted, considering successively palaeoclimates and continental drifts, tectonic movements and la...
