ABSTRACT:

The failure mechanisms that could originate the mega paleo-rockslides of Güímar and La Orotava in Tenerife (Canary Islands) are analyzed, based on the geomechanical site investigations carried out on the pre-failure volcanic materials of Tenerife island flanks. Geological and geomorphological modelling and geomechanical characterization of the materials are presented. Hyaloclastites rocks are forming the submarine substratum of the island edifice presenting a highly deformable behaviour. Preliminary stability analyses have suggested potential failure surfaces in the hyloclastites rocks.

1 INTRODUCTION

More than 20 mega rockslides have been described in Canary Islands (Acosta et al., 2005). The resulting slided masses, deposited on the ocean floor, cover areas of thousands of square kilometers (350–2600 km2) and volumes of hundreds of cubic kilometers (80–650 km3). These paleo-landslides have been considered as one of the largest known in the world by their volume. Güímar and La Orotava valleys in Tenerife were originated by mega rockslides. Both constitute exceptional examples due to their geomorphological features and the fact that the slided deposits have been identified in the ocean floor and inside the galleries excavated in the island (Navarro & Coello, 1989). In spite of their importance, only few investigations have been carried out to analyze these processes under a geomechanical point of view. The authors are carrying out detailed studies on the geomechanical properties of the materials involved, including in situ testing and geophysical surveys, to evaluate the instability processes of the volcanic islands flanks (Ferrer et al., 2007, 2008). This paper presents the preliminary results of the site investigation carried out on the submarine materials formed by hyaloclastites and the role of these rocks on the stability of the volcanic edifice of Tenerife.

2 GÜÍMAR AND LA OROTAVA ROCKSLIDES

Güímar and La Orotava valleys are 9–12 km wide.

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