Evolutionary development and volume balance calculations of the Ana Slide in the Eivissa Channel, Western Mediterranean

Submarine landslides are widespread phenomena on continental slopes and act as prime sediment transport processes between shallow and deep marine regions. In addition, they pose significant risk to coastal communities worldwide. Within this study, we focus on the Ana Slide, a relatively small landslide with areal extent of 4.7 km² located at water depth between 635 – 905 m on the eastern slopes of the Eivissa Channel, western Mediterranean. Predominant sediment types are high-water content, carbonate-dominated hemipelagic deposits susceptible to high pore pressures and liquefaction. The Ana Slide is completely covered by very-high resolution bathymetric and 3D seismic data and additional legacy data, what allows us to perform detailed kinematic analysis of the landslide evolutionary development.
The Ana Slide is characterised by three landslide domains: the 1) evacuational or headwall domain, 2) translational domain, and 3) accumulational or toe domain. While the headwall domain demonstrates classic features of material evacuation and poses as the exclusive source of material within the landslide process, the translational domain is characterised by extensive in-situ remnant blocks which were unaffected during failure. Instead, landslide material from the evacuational domain moved up and over the translational domain. The toe domain exhibits extensive chaotic seismic facies with compressional ridges throughout the deposit and imprinted onto the seafloor. 
Even though the toe domain is characterised by extensive chaotic seismic facies, its volume differs significantly from the volume of the evacuated material. Thus, we conclude that the chaotic seismic facies does not represent landslide material. Instead, the in-situ sediment underwent a range of soft-sediment deformation processes. We propose two mechanisms responsible for this deformation: loading- and shearing-induced soft-sediment deformation resulting from rapid deposition of overburden material. Under consideration of the likely elevated pore pressure and liquefaction potential of deposits, these mechanisms lead to the destruction and disturbance of internal reflections.
Our analysis demonstrates the difficulties in distinguishing between actually failed landslide material and deformed but not translated sediment, which may well lead to erroneous landslide volume estimations. Our new model of the evolutionary development of the Ana Slide may well hold for many other submarine landslides globally, the volumes of which could be significantly overestimated.