Abstract

We analyze the role of low-strength materials in the potential structural instability related to volcano spreading at the active Teide stratovolcano (Tenerife, Canary Islands). To study the low-strength materials we took advantage of a network of large tunnels within the volcano, excavated for water supply, which allows the in situ inspection and reconstruction of both volcano and substratum structure. We identified two factors which are potentially important to Teide’s instability: 1) a dipping low-strength substratum breccia layer; and 2) a hydrothermally-altered weak core inside the volcano. Despite we do not find clear structural evidence for volcano substratum spreading, both Teide topographic shape and the summit faulting are features similar to those accepted as examples of volcano flank spreading over a weak core. The detected asymmetric deformation of the edifice makes the north flank of Teide a strong candidate for a potential failure