Morphological and structural analysis in the Anaga offshore massif, Canary Islands: fractures and debris avalanches relationships

Abstract

As part of the 'National Hydrographic and Oceanographic Research Plan for the Spanish Exclusive Economic Zone', multibeam bathymetry and seismic reflection profiles were obtained in the Canary Islands aboard the R/V Hespérides. The submarine flanks of the Anaga offshore extension of Tenerife Island are here studied to analyze its geomorphology. In the north sector of the Anaga submarine massif, the extension of the Anaga Debris Avalanche has been mapped for the first time, and a volume of 36 km 3 was calculated. The relationship between the Anaga and Orotava Debris Avalanches is also described. Faulting has been recognized as a key process for the occurrence of debris avalanches and the growth of volcanic lineaments. Moreover, faulting affects previous structures and the channelling of debris flows. Structural analysis shows the typical radial pattern of an oceanic island. In addition, a NE-SW dominant direction of faulting was obtained, consistent with the Tenerife Island structural trend seen in the Anaga Massif and Cordillera Dorsal. NW-SE and E-W are two other main trends seen in the area. Special interest is manifest in two long faults: 'Santa Cruz Fault' bounds the southern edge of Anaga offshore Massif with a length of 50 km and a direction that changes from NE-SW to almost E-W. The Güimar Debris Avalanche was probably channeled by this fault. The 'Guayotá Fault' was recognized in several seismic profiles with a N-S direction that changes towards NW-SE at its southern end. This fault affects the more recent sediments with a vertical offset of 25-30 m, along 60 km. It has been interpreted as a transpressive strike-slip fault.

Geological evolution of the volcanic island La Gomera, Canary Islands, from analysis of its geomorphology

“…8 and 10) also could be related to these avalanches. Similar reentrants have been ascribed to such processes on the insular apron of Gran Canaria (Funk and Schmincke, 1998) and Tenerife (Llanes et al, 2003). Is it geologically feasible that a feature created by the collapse of a volcanic structure 9.4-8.7 Ma could have survived to the present without having been eradicated by latter geologic events?…”

“…8). Similar features on the shelves of Gran Canaria and Tenerife have been related to landslides (Funck and Schmincke, 1998;Llanes et al, 2003).…”

“…In the last decades multibeam mapping has increased our possibilities to identify offshore landslide deposits, as well as other features, making it possible to link morphological processes onshore and offshore, leading to more precise interpretations. The Canary Islands have been the object of several generalized and detailed offshore studies, and numerous landslides have been mapped around the islands (Watts and Masson, 1995;Masson, 1996;Urgeles et al, 1997;Teide Group, 1997;Funck and Schmincke, 1998;Urgeles et al, 1999;Krastel et al, 2001;Gee et al, 2001b;Masson et al, 2002;Acosta et al, 2003;Llanes et al, 2003).…”