Volcanic Mega-Landslides In Tenerife (Canary Islands, Spain)

In the last two decades it has been demonstrated the occurrence of large landslides in volcanic buildings, as well as the influence of these processes in the evolution of volcanic islands. More than 20 paleoland-slides have been described in the Canary Islands. Guimar and La Orotava valleys, in Tenerife island, originated by megalandslides some hundreds of thousands years ago, are two exceptional examples because of their geomorphological features and the identification of the subaquatic landslided deposits in the ocean floor and in the interior of the underground galleries excavated in the island. In spite of their importance and the acceptance of the occurrence of these instability processes by the scientific community, only few investigations have been carried out to analyse and to explain these processes under the geomechanical point of view. The authors are developing a research project, supported by the Geological Survey of Spain and the Commission for Science and Technology of Spain, being the main objective to explain why and how these megalandslides took place, which were the mechanisms, the influencing and triggering factors and their role. Detailed studies on characterization of volcanic rock materials involved in the landslides, geological evolution, morphological reconstruction, geophysical data interpretation, laboratory tests, age determinations, etc. have been or are currently being carried out in order to prepare the geological, hydrogeological and geomechanical models for the analysis and evaluation of the influence of the different factors affecting the stability and mechanical behaviour, to verify the current hypothesis on La Orotava and Guimar large valleys generation and to explain the mechanisms of the megalandslides in volcanic buildings slopes.