Development and Emplacement of the Ana Slide, Eivissa Channel, Western
Mediterranean Sea
Abstract
Submarine landslides can destroy seafloor infrastructure and generate
devastating tsunamis, but in spite of decades of research into the
functioning of submarine landslides there are still numerous open
questions in particular how different phases of sliding influence each
other. Here, we re-analyse the Ana Slide - a relatively small
(<1 km3) landslide in the Balearic Islands, which is unique
because it is completely imaged by high-resolution 3D seismic data. The
Ana Slide comprises three domains: (i) a source area that is almost
completely evacuated with evidence of headscarp retrogression; (ii) an
adjacent downslope translational domain representing a bypass zone for
the material that was mobilized in the source area, and (iii) the
deposit formed by the mobilized material, which accumulated downslope in
a sink area. Isochron maps show deep chaotic seismic units underneath
the thickest deposits. We infer that rapid deposition of the landslide
material deformed the underlying sediments. A thin stratified
sedimentary unit between three lobes shows that the Ana Slide evolved in
two failure stages separated by several tens of thousands of years. This
illustrates the danger of over-estimating the volume of mobilized
material and under-estimating the complexity even of relatively simple
slope failures without high-quality seismic data.