Non-eruptive geological hazards of dormant volcanoes: Sao Miguel, Azores Perigos geologicos nao eruptivos en vulcoes adormecidos: Sao Miguel, Acores

São Miguel Island presents a diversity of geological hazards that are related to non-eruptive processes. Frequent seismic swarms and destructive earthquakes, of volcanic and tectonically-related origin, have been recorded on the Island since it was settled in the 15th century. Large areas of volcanic edifices of Sete Cidades, Fogo and Furnas are unstable. Steep slopes, unconsolidated and poorly consolidated materials, such as volcaniclastic deposits occasionally weathered by hydrothermal activity, play an important role in landslide activity. Slope instability is mainly triggered by intense rainfall, but also by seismic activity, sea and fluvial erosion and/or anthropogenic activity. Volcano degassing represents a major risk during anomalous gas release and a continuous menace for the public health