Large landslides triggered by caldera collapse events in Tenerife, Canary Islands

Landsliding is a significant process on volcanic edifices, with individual events exceeding several cubic kilometres in volume. The causes of such mas s movements and their relationship with volcanic activity are still poorly understood. Landslide events are an important factor in the evolution of vo lcanic islands such as Tenerife, where vertical and lateral collapses have occurred repeatedly. Subaerial and submarine processes related to landslide events strongly influence the morphology of the island. On Tenerife there are three very big valleys, Guimar, La Orotava and Iced, that have been cre ated by large landslide events with ages ranging from Upper Pliocene to Mid dle Pleistocene. The landslides affect the northern flanks of the island an d the slopes of a large central volcanic edifice, the Las Canadas volcano, which is truncated by the Las Canadas caldera, a multicyclic collapse depre ssion, formed between 1.02 and 0.17 Ma. We have focused our studies on the potential for caldera collapse events to trigger large scale landslides. Th e available geological and morphological information has been incorporated inta numerical models, which simulate the destabilising effects of a calder a collapse episode. The results of the numerical modelling indicate that pr ocesses associated with caldera collapse events can overcome the stabilisin g forces on the volcano flank and trigger landslides. We propose that calde ra collapse events may have triggered large landslides on the slopes of the Las Canadas volcano. (C) 1999 Elsevier Science Ltd. All rights reserved.