DI CRESCENZO G. & SANTO A.
Analisi geomorfologica delle frane da scorrimento – colata rapida in depositi piroclastici della Penisola Sorrentina (Campania) – Geomorphological analysis of the rapid earth flowsin the pyroclastic deposits of the Surrentine peninsula (Campania, Italy)
Pages 57-72
Abstract
The main aim of this paper is to focus the role of the geomorphological and stratigraphical analysis in the study of rapid earth flows which interest pyroclastic deposits. The geomorphological and stratigraphical analysis of the main rapid earth flows which took place in Surrentine Peninsula during January 1997, together with the collection of historical data of ancient landslides and the stratigraphical identification of paleolandslides along the main slopes of the area, let us to collect some important observations. First of all, on the basis of their morphology, two main kinds of rapid earth flows have been distinguished: «canalized» and «uncanalized». The first one, being the most fluid and having the highest velocity, shows the biggest hazard. The stratigraphical analysis of pyroclastic deposits in the sliding portion of the main slide-rapid earth flows has shown that significant pumiceous levels are always present at the base, or within, the sliding plane. These levels play an important role both as sliding plane and for their water content. The geomorphological analysis of the main slopes interested by these landslides has pointed out that the difference of level between the top and the foot of the slope and the dip of the slope are proportional to the invasion capacity of the landslide body. The same relationship exists between the thickness of the pumiceous levels and the invasion capacity. The collection of the data of the dip of the «crown zone» and of the «sliding zone» of 15 rapid earth flows show that a 30° degree value seems to be a good treshold value in the delimitation of the area that could be potentially instable. All these data are foundamental data both for the mapping of the «hazard zones» and for the modelling of the mechanism of slope failure.