In 1903, the eastern slope of Turtle Mountain (Alberta) was affected
by a 30 M m3-rockslide named Frank Slide that resulted in more than
70 casualties. Assuming that the main discontinuity sets, including
bedding, control part of the slope morphology, the structural features
of Turtle Mountain were investigated using a digital elevation model
(DEM). Using new landscape analysis techniques, we have identified
three main joint and fault sets. These results are in agreement with
those sets identified through field observations. Landscape analysis
techniques, using a DEM, confirm and refine the most recent geology
model of the Frank Slide. The rockslide was initiated along bedding
and a fault at the base of the slope and propagated up slope by a
regressive process following a surface composed of pre-existing discontinuities.
The DEM analysis also permits the identification of important geological
structures along the 1903 slide scar.
Based on the so called Sloping Local Base Level (SLBL) an estimation
was made of the present unstable volumes in the main scar delimited
by the cracks, and around the south area of the scar (South Peak).
The SLBL is a method permitting a geometric interpretation of the
failure surface based on a DEM.
Finally we propose a failure mechanism permitting the progressive
failure of the rock mass that considers gentle dipping wedges (30°).
The prisms or wedges defined by two discontinuity sets permit the
creation of a failure surface by progressive failure. Such structures
are more commonly observed in recent rockslides. This method is efficient
and is recommended as a preliminary analysis prior to field investigation.