Shallow flank deformation at Cumbre Vieja volcano (Canary Islands): Implications on the stability of steep-sided volcano flanks at oceanic islands

Abstract

Volcano flank instability has been recognized at many volcanoes around the globe. Structural, morphological, geodetic and geophysical evidence supports the continuous deformation of their flanks. While identification of instability has been recognized in well-documented examples, until recently the initial stages of such processes have been difficult to capture. Using a combination of geological, geodetic and geophysical data analysis, we study the stability of the Cumbre Vieja. New descending radar interferometric data, covering a volcanologically quiet period between 1992 and 2008 at Cumbre Vieja, indicate movement away from the satellite on the western volcano flank. Using an inversion of stacked velocity maps, we determine the geometry and slip for a near-horizontal dislocation beneath the western flank of Cumbre Vieja. Our ground deformation modelling results (position and depth) are in agreement with a low-density anomaly constrained by gravity data. The previously undetected intereruptive ground deformation at Cumbre Vieja volcano flanks was explained as an indicator of a kinematic passive response model of the flank, where the flanks were mobilized only during periods of magmatic activity (shallow dike intrusions) and remained stable and undeformed during intereruptive periods. Here, we present new results indicating that active creeping stress release due to gravitational loading is also a dominant deformation mechanism for (current) intereruptive periods at Cumbre Vieja, which would contribute positively to the stabilization of the edifice and reduce the associated hazard related to the volcano flank dynamics. This study at Cumbre Vieja can be considered as a prototype for similar volcanoes around the Macaronesian islands group (e.g., Fogo, Teide, El Hierro, Pico) and elsewhere.