Conditions favouring catastrophic landslides on Tenerife (Canary Islands)

Catastrophic failures of volcano flanks represent one of the most hazardous geological phenomena. These immense mass movements originate either by increasing the destabilizing forces (driving forces) or by reducing the strength of the materials involved, or both. The study of large volcanic landslides on Tenerife suggests that the presence of weak residual soils (palaeosols) in combination with the pre-existence of deep, narrow canyons created by fluvial erosion, have played a fundamental role in the initiation of large-scale sector collapses of the volcanic edifice, regardless of the triggering mechanism considered. Residual soils strongly reduce the material strength during undrained loading, while pre-existing canyons control the lateral limits of the landslide. The existence of a wet climate in some sectors of the island favours these circumstances.