Gravity sliding is a ubiquitous process where slopes are high and discontinuities control rock strength. Mutual interlocking of discontinuous rock masses maintains slope stability. If the growth of a crevice at the head of an incipient slide is lateral, then the sliding mass loads the crevice tip that in turn propagates to increase the load. This allows a single crevice to grow and release the interlocking that has maintained stability.
Such an instability mechanism seems to act on a landslide that we recently discovered south of Jerusalem.