Pico Volcano Flank Landslides and Hazard Implications: Preliminary Results

In the Pico volcano (Pico Island, Azores) flank, there is evidence of 8 major landslides that were the object of back analysis using the Generalized Limit Equilibrium method. The analyses yielded a close range of strength parameters for a safety factor equal to 1, with c′ = 10 kPa and average friction angle, ϕ′ = 40.1° (38.7–41.1°), for wet conditions, and similar values for the dry condition pseudo-static analysis, with c′ = 10 kPa and average ϕ′ = 40.2° (39.0–40.9°). The landslide’s shadow angle varied between 31.7 and 34.0° and showed no relation with the landslide’s scar elevation or planimetric area. Considering the numerous tension cracks at the upper part of the southern flank of the Pico volcano and the steep down-slope angle, there is the possibility of a large landslide developing and the debris travelling down to the S. Caetano cliff crest and village. These preliminary results suggest that this problem requires further studies to prevent or minimize the possible related hazards.