Dinamica degli "avalanching glaciers": il caso del seracco della Punta S. Matteo (Ghiacciaio dei Forni, Valtellina, Italia)

Avalanching glaciers may be affected by periodic or occasional falls of ice (by breaking-off mechanism) giving rise to tragic events. These events have been rising the interest in the instability of avalanching glaciers. This contribution comes into this context. In summer 2003 a big fracture was observed on the North wall of Punta S. Matteo (Forni Glacier, Ortles-Cevedale Group, Italy). As this phenomenon developed a big unstable ice-mass, starting form May 2005, it was decided to survey Monte S. Matteo avalanching glacier (whose fall could involve the West sector of Forni Glacier thus representing an actual hazard for climbers, tourists, skiers and trekkers). The monitoring campaign consisted in collecting photographs (from May 2005 to March 2007) and in surveying the ice mass by total station (from July 2005 to November 2005). In addition, in May 2005 a laser scanner surveys was performed. The collected photographs made it possible to draw the evolution of this unstable ice-mass. Data acquired with total station permitted to calculate displacement, velocities and flow direction of the unstable ice-mass. The laser scanner survey permitted to calculate the volume of the unstable ice-mass. Furthermore the role of air temperature conditions in the ice-mass evolution was also investigated.