An analysis of the morphological, geological and structural features of Teide stratovolcano, Tenerife Rodrigo del Potro a,b , Harry Pinkerton a, ⁎, Marcel Hürlimann c a Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK b Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apdo. 86-3000, Heredia, Costa Rica c Geotechnical Engineering and Geosciences Department, Technical University of Catalonia (UPC), Jordi Girona 1-3 (D2),08034 Barcelona, Spain abstract article info Article history: Received 1 July 2008 Accepted 14 December 2008 Available online 1 January 2009 Keywords: Teide Tenerife volcanic evolution volcaniclastic deposits A combined field, GIS and modelling study has given us new insights into the evolution and morphology of Teide stratovolcano in the central part of Tenerife. Central to our analysis was an investigation of the nature and development of a number of enigmatic morphological features, including two large ‘bulges’ at mid-elevation in the north-western and east–north-eastern flanks. This entailed a detailed analysis of high resolution digital elevation data, coupled with new photogeological, geological and geomorpholo- gical surveys which were examined using GIS. Our geological investigations reveal that widespread deposits on the steep northern flanks of the edifice were volcaniclastic deposits. These formed during the collapse of incandescent lava flow fronts and, possibly, domes and lobes. Careful examination of other deposits on the lower north-western flank has shown that they formed during magma–water interactions. Detailed analysis has revealed the presence of small coulée eruption vents, abrupt terminations to lava flows and vertical scarps. We were also able to confirm the presence of two nested gräben, along which there has been extensive hydrothermal alteration. Finite element modelling of the basement beneath Teide and structural stability suggest that the Teide edifice was emplaced on the headwall of the Icod island flank collapse. We conclude that the two bulges are flank vents, similar to Pico Viejo, although on a smaller scale. The presence of these flank vents suggests that conduit blockage has probably been more common than previously estimated on Teide. We suggest that future hazard mitigation measures should take into account the potential for large flank vents forming during future eruptions, the possibility of explosive activity from the central edifice, and pyroclastic density currents in front of advancing flows on the flanks of Teide. © 2009 Elsevier B.V. All rights reserved. 1. Introduction While our knowledge of the geology of the island of Tenerife has improved markedly over the past decades, geological investigations of Teide volcano areless advanced. Until recently, studies of Teide were carried out as part of investigations of larger areas (Carracedo, 1994, 1999; Martí et al., 1994; Ancochea et al., 1999). More recent mapping, geochemical and petrological investigations on Teide by Ablay and Martí (2000) form the basis of our current understanding of the structure and evolution of the Teide–Pico Viejo complex. The only other geological detailed investigation of part of Teide was by Pérez- Torrado et al. (2004) who studied a small locality on the north- western flank. Although a number of geophysical investigations have been carried out in the Las Cañadas Caldera (e.g. Ablay and Kearey, 2000; Pous et al., 2002), these have not extended to the Teide edifice. Outstanding problems on the evolution and morphology of the Teide edifice include the significance and mode of formation of enigmatic morphological features on the edifice. These include large ‘bulges’ at mid-elevation which are apparent on both topographic and slope maps of the edifice. Other features identified on aerial photographs that cannot be interpreted without detailed field- work include eruption vents, abrupt terminations to lava flows, vertical scarps, and hydrothermally altered areas. To fully under- stand the formation of these features, an improved knowledge of the structural stability of the edifice and the volcanological evolution of the volcano are required. To achieve this, we used GIS to analyse data from high resolution aerial photographs and digital eleva- tion models in combination with detailed field investigations and numerical models. In addition to improving our understanding of the structure and evolution of Teide edifice, the present study aims to provide data on potential hazards on Teide. This was stimulated by a significant increase in seismic activity on Tenerife in 2004 (García et al., 2006; Gottsmann et al., 2006). Journal of Volcanology and Geothermal Research 181 (2009) 89–105 ⁎ Corresponding author. Tel.: +44 1524593912; fax: +44 1524593985. E-mail address: h.pinkerton@lancaster.ac.uk (H. Pinkerton). 0377-0273/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jvolgeores.2008.12.013 Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores