In July 2006, approximately 2 million m3 of massive limestone began
to move on the east flank of the Eiger in central Switzerland. For
more than two years after the initial failure, the rock mass moved
at rates of up to 70 cm per day. A detailed analysis of the structures
and velocities of the different moving blocks was conducted with
the aid of terrestrial laser scanning. The moving rock mass included
a rear block that subsided, pushing a frontal block forward. Movement
directions were controlled by discontinuity sets that formed wedges
bounded on one side by sub-vertical bedding planes. The instability
was, until recently, buttressed by a glacier. Slope observations
and results of continuum and discontinuum modeling indicate that
the structure of the rock mass and topography were the main causes
of the instability. Progressive weathering and mechanical fatigue
of the rock mass appear to have led to the failure. A dynamic analytical
model further indicates that the rockslide was primarily controlled
by a reduction in the strength of discontinuities, the effects of
ice deformation, and ? to a limited extent ? groundwater flow. This
study shows that realistic and simple instability models can be constructed
for rock-slope failures if high-resolution data are available.