Long Term Ground Deformation in Volcanic Islands: Tenerife and La Palma, Canaries

Abstract

Canary Islands form a volcanic archipelago with 7 major islands with a long-standing history of volcanic activity that began more than 40 million years ago More than a dozen eruptions have occurred on the islands of Tenerife, Lanzarote, and La Palma since the 16 th century. We used several geodetic techniques in order to achieve ground deformation on those islands. We propose that the measured deformation is directly related to gravitational sinking of the intrusive core the island into a weak lithosphere. We favour this thesis, relative to that of spreading, because neither the published data on the geology of Tenerife show evidence of compressional structures around the base of the island nor the GPS data indicate significant radial displacements, which would have been present in the case of spreading. In adition, given that the crust has been inflected under the mass of Tenerife, following Borgia (1994), we propose that the volcanic edifice is in a state of compression, which, in some volcanoes, has in the past been associated with hazardous explosive eruptions