Soils of the detachment crowns of Ischia landslides (Italy)

Abstract

This paper represents a pedological contribution on the understanding of the soils of the detachment crowns of the landslides occurred in Ischia on April 30th 2006 at Monte di Vezzi. Such contribution is relevant considering that the material mobilised by the landslides is mainly composed of soils with various degree of pedogenesis and very few rock fragments. The study has been conducted on two soil profiles sampled on two representative detachment crowns. The main outcome of the chemical, physical and mineralogical analysis is: (i) presence of relevant morphological, chemical and physical vertical discontinuities in the soil profiles, (ii) absence of crystalline clay minerals and low content of poorly ordered clay minerals, like allophane, imogolite and ferrihydrite, (iii) high content in primary glass. The studied soils are somehow different from the typical Andosols reported in the detachment crowns of other Campania catastrophic landslides (Sarno, Quindici, etc.) and their classification, according to WRB, ranges from Vitric Andosols to Cambic Regosols. Anyway, Ischia landslides, as well as the other Campania landslides, present both natural vertical discontinuities and anthropic/natural horizontal discontinuities of the soil cover that surely contributed to the initiation mechanisms of these landslides. The main findings of this work emphasise both (i) the need for further works on genesis (geological/pedological) and function of the observed discontinuities and (ii) the need for an ecosystem management caring for any natural and anthropic discontinuities of the soil cover.