Formation d'une caldera d'érosion et instabilité récurrente d'une île de point chaud : la caldera de Taburiente, La Palma, îles Canaries / Formation of an erosion caldera and recurring instability on a hotspot-generated island: the caldera de Taburiente, La Palma, Canary Islands

Abstract

Abstract The caldera de Taburiente is an erosion caldera caused by backwearing of the walls of a giant landslide embayment that affected the south-west flanks of the island of La Palma 560 ky. ago. This study reconstitutes the geonwrphological evolution of the depression and emphasises the role of lithological and structural factors. Patterns of erosion are guided by the structural configuration, in which uplifted and deeply weathered submarine volcanic materials are overlain by denser subaerial volcanic rocks, and by the geometry of a deep-seated structure, which has been interpreted as an older central collapse caldera. Recurrent instability is a determining factor in the formation of erosion calderas on hotspot-related islands. The construction rates (0,5-2 m/ka) and destruction rates (linear incision: 0,3-3,5 m/ka; headward erosion: 0,7-20 m/ka) estimated in this study provide a time-frame for understanding the stages of growth and decay of volcanic landforms in the Canary Islands.