Onshore and offshore geomorphological features of the El Golfo debris avalanche (El Hierro, Canary Islands)

Abstract

This study shows an onshore-offshore morpho-structural characterization of the El Golfo flank collapse and debris avalanche on El Hierro (Canary Islands, Spain). Erosive and depositional features have been identified based on: LIDAR topography and geology from water galleries (onshore); and high-resolution 3.5 kHz and multichannel seismic reflection profiles, and multibeam data (offshore). The onshore headwall scarp shows a non-continuous profile formed by two semi-circular amphitheatres and extends offshore by a smooth chute. The chute ends at about 3000–3200 m water depth in the distal depositional area. Multichannel seismic profiles show two major subunits of chaotic reflectors in the debris avalanche deposits. Results suggest that the El Golfo debris avalanche event likely took place in multiple stages. Consequently, we suggest that the multistaged nature of El Golfo debris avalanche greatly reduces the tsunamigenic potential of these flank collapses.