Volcanic soils and landslides: a case study of the island of Ischia (southern Italy) and its relationship with other Campania events

摘要: Abstract. An integrated investigation was carried out on the volcanic soils involved in landslide phenomena that occurred 2006 at Mt. Vezzi island of Ischia (southern Italy). Chemical (soil pH, organic carbon content, exchangeable cations and cation exchange capacity, electrical conductivity, Na adsorption ratio Al, Fe Si forms), physical (particle pore size distribution, structure), hydrological water retention, saturated unsaturated hydraulic conductivity), mineralogical micromorphological analyses were for three soil profiles selected two main head scarps. The studied showed a substantial abrupt discontinuity all properties interface with buried fine ash layer (namely, 2C horizon), only marginally sliding surface phenomena. When compared to overlying horizons, (i) grey is almost pumice free, silt content increasing by 20 %; (ii) ks values 1 order magnitude lower; (iii) distribution concentrated into small (15–30 μm modal class) pores characterised very low percolation threshold (approximately 15–25 μm); (iv) presence expandable clay minerals; (v) complex. Most these indicated lower permeability horizon ones. Nevertheless, it possible assume this be an impeding vertical fluxes identification thin (6.5 mm) finely stratified layer, top 2C, hydromorphic features (e.g. / Mn concretions) within layer. Although Vezzi's environment has many common those other Campania debris-mudflows high gradient, north-facing slope, similar forestry, origin parent material), results study suggest more complex relationship between landslides emphasise role discontinuities as noteworthy predisposing factors.