Instability of oceanic volcanic edifices: Examples of sector collapse, debris avalanches, and debris flows from Gran Canaria (Canary Islands)

Abstract

We review different types of mass transfer (landslides, debris avalanches, debris flows, turbidites) generated throughout the evolution of a long-lived volcanic island (Gran Canaria) from its emergence at ca. 16 Ma to the present. The choice of Gran Canaria is based on its unique characteristics in that the various types of downslope mass transfer are not only documented by acoustic methods and bathymetry, but also by lithology (ODP Leg 157 drilling and land deposits). The intermittent mass transfer caused by edifice instability and direct volcanic processes (pyroclastic flows) represents by far the greatest contribution of mass to the depot centers peripheral to the island, as contrasted with steady erosion. We speculate on the impact of long-term trade wind directions as major factors in deeply eroding and thus weakening the northern slopes and therefore preferentially localizing sector collapses on the windward sides of the islands.