Santa and his reindeers experience the effects of submarine slope failure.
Click image to start movie (animated gif; 1.8 MB).
Distinct Element Method model of a cohesionless (dry or normally pressured) slope. The entire model is tilted by five degrees by changing the direction of gravitational acceleration. Particles that are moving above the initial slope surface are deleted and new particles are added in regular intervals if space permits to do so (red and white layers). This syn-deformational erosion and sedimentation assures that the system stays in an unstable state. The central part of the particle model rests on a frictionless plate (red line underneath Santa and his reindeers); adjacent areas have a frictional base. The length of the free-slip area relative to the layer thickness is greater than a critical length, resulting in slope failure. This critical length can be determined by computing the transition length from an active to a passive Rankine stress state, i.e. upslope normal faulting and downslope reverse faulting, respectively. For cohesionless, dry or normally pressured slopes, the critical length to layer thickness ratio is entirely determined by the internal friction angle of the layer and the slope angle; density, water depth and gravitational acceleration all cancel out.