Comment on “Reconstructing the architectural evolution of volcanic islands from combined K/Ar, morphologic, tectonic, and magnetic data: The Faial Island example (Azores)” by Hildenbrand et al. (2012) [J. Volcanol. Geotherm. Res. 241–242 (2012) 39–48

Abstract

Hildenbrand et al. (2012) have presented a model for the geological evolution of Faial Island. In their interpretation, the oldest volcanic system extended much further than the present-day eastern part of the subaerial island, with a ridge-like morphology, into the Faial–S. Jorge channel. Furthermore, the western side of the system was suggested to have been later destroyed by mass-wasting. Based on now extensive multibeam bathymetry collected surrounding Faial Island, we find no evidence supporting such interpretations. The geometry of the shelf edge suggests that a near-circular edifice occupied the eastern part of the present-day subaerial island. In addition, the submarine morphology does not show massive mass-wasting deposits around the base of the edifice. Rather, bathymetric gradients and morphology suggest that the submarine slopes were formed from volcanic emplacements or from material displaced in only small-scale mass-movements or sedimentary flows, and have not failed catastrophically. Evidence that a ridge-like feature extended into the Faial–S. Jorge channel is also lacking. These observations highlight the potentially valuable information that sonar data can provide to evaluating ocean island evolution from the more limited extend of outcrops on land.