The structural evolution and giant landslides of La Palma, Canary Islands

Abstract

The island of La Palma, in the western Canary Archipelago, is formed by a partially dismantled and eroded Plio-Pleistocene strato-shield volcano (Taburiente/Cumbre Nueva) that is overlapped and elongated to the south by an active rift-centred volcano - Cumbre Vieja. Stratigraphic measurements were used to systematically profile the basal part of the giant Quaternary landslide escarpments that form prominent morphological features on the island. An exhumed detachment fault was discovered in the process. The escarpments, which are 45 km in perimeter and up to 1 km high, are interpreted in the light of this discovery to have developed by synchronous lateral collapses that were preceded by a geologically significant period of gravitational spreading. The detachment occupies the position of what has been classified in contemporary studies as an erosional unconformity, separating an uplifted Pliocene seamount from the subaerial volcanic successions forming the Taburiente/Cumbre Nueva strato-shield. The Cumbre Nueva Detachment, as it is named herein, together with the overlying pyroclast-rich collapse breccias (herein named the Tenerra Collapse Breccia), have not been the subject of any previous academic studies. Both of these units are separated by the detachment plane which geometrically emulates the domal topography of the seamount basement. Together they provide an opportunity to increase our understanding of the geometry and mechanisms of giant landslides on La Palma, past and future. The present study is unique in that it describes field kinematic evidence for the development and exhumation of a low angle fault zone that penetrates the exhumed intrusive core of an isolated volcano. Such data are rare in volcanic environments , irrespective of the wealth of observations of exhumed detachments in continental/orogenic environments. By investigating the newly discovered detachment and toreva remnants and by evaluating the structural and bathymetric data around La Palma, this doctorate has four main objectives that fundamentally focus upon three major sector collapses.