The dynamics of coastal landslides: insights from laboratory experiments and theoretical analyses

Laboratory experiments have been carried out to study the dynamics of landslides commencing sub-aerially and ending inside a water basin. A comparison between experiments with and without water shows differences in the final deposits. In the subaqueous experiments the grains did not spread out from the mass in the same way as in the subaerial movement. It is suggested that air can be trapped inside the mass which, released during the final stage of the underwater mass propagation, modifies the buoyancy forces. Other effects observed during the air to water transition include the "jumping" and "tilting" of grains. It is concluded that the air to water transition plays a key role in the dynamics of combined subaerial/subaqueous landslides. The information obtained from the experiments may also be useful in the consideration of tsunami generation and the sedimentological analyses of landslide deposits.