Morphology of pillow-hollow and quilted-cover bedforms in Lake Geneva, Switzerland
Extensive areas of the bottom of Lake Geneva are covered with bedforms that have been referred to as pillow-hollows and quilted-cover pattern by prior observers, as well as with sediment waves and trenches. These structures are decimeter to meter scale. A large dataset of video recording and stereographic camera imagery of the lake bottom was recently acquired during a campaign with the Russian MIR submersibles. We present a classification of the different types of sediment structures with a focus on distinctive morphological characters. The variations in the observed lake-bottom structures reveal a continuous range of morphologies between the aforementioned bedforms. Although the role of the bottom-dwelling Burbot fish in at least maintaining the bottom landscape has been suggested in previous studies, the origin of the observed bedforms is unclear. On the basis of our preliminary observations, other candidate mechanisms are briefly mentioned, including bottom currents generated by internal waves. Understanding the formation and evolution of lake-bottom morphology is important since the transport pathways of lake sediment condition to a large extent the fluxes and cycle of pollutants.