THE ROLE OF VOLCANIC AND ANTHROPOGENIC ACTIVITIES IN CONTROLLING THE EROSION PROCESSES AT VULCANO ISLAND (ITALY)

The paper describes the erosion processes acting at La Fossa cone (Vulcano Island, Italy). La Fossa cone is a stratovolcano made up of pyroclastic deposits and lavas covered by tuffs from the last eruption, dated 1888-90. Its flanks are affected by intense water erosion phenomena leading to the formation of denudation surfaces due to sheet erosion, rills, gullies and small canyons. As a consequence of very intense rainfalls, episodic debris flows occur along main gullies and canyons. Fumarolic activity plays an important role in the control of erosion processes, being both an obstacle for the growth of vegetation and a weathering factor. The GIS analysis and comparison of geo-referenced maps and aerial photos highlighted the influence of man-made structures on erosion processes, with particular reference to deep modifications in the natural stream network induced by buildings and roads. The combined effects of volcanic and anthropogenic activities, together with the additional role played by the strong inter-annual variability of rainfall amounts and intensities, give rise to significant changes in water erosion rates. A total volume of 5,700 m3 of volcanic products eroded between the years 1980 and 2008 from the upper portion of La Fossa cone has been estimated by GIS analysis.