Rifting, recurrent landsliding and Miocene structural reorganization on NW-Tenerife (Canary Islands)

We studied mechanisms of structural destabilization of ocean island flanks by considering the linkage between volcano construction and volcano destruction, exemplified by the composite Teno shield volcano on Tenerife (Canary Islands). During growth, Tenerife episodically experienced giant landslides, genetically associated with rifting and preferentially located between two arms of a three-armed rift system. The deeply eroded late Miocene Teno massif allows insights into the rifting processes, the failure mechanisms and related structures. The semicircular geometry of palaeo-scarps and fracture systems, breccia deposits and the local dike swarm reconfigurations delineate two clear landslide scarp regions. Following an earlier collapse of the older Los Gigantes Formation to the north, the rocks around the scarp became fractured and intruded by dikes. Substantial lava infill and enduring dike emplacement increased the load on the weak scarp and forced the flank to creep again, finally resulting in the collapse of the younger Carrizales Formation. Once more, the changing stress field caused deformation of the nearby rocks, a fracture belt formed around the scarp and dikes intruded into new (concentric) directions. The outline, size and direction of the second failed flank of Teno very much resembles the first collapse. We suggest structural clues concerning mechanisms of recurrent volcano flank failure, verifying the concept that volcano flanks that have failed are prone to collapse again with similar dimensions.