Which Numbered Feature on This Figure Is Critical to Enable

Multiple Choice

Which numbered feature on this figure is critical to enable a rock slide to start?

A) 1,a linear or curved scar marking where the slide pulled away from the hill
B) 2,small fractures within the sliding block
C) 3,layers,fractures,or some other discontinuity inclined downslope
D) 4,the front of the slide,where it overruns the land surface
E) 5,a valley or other open space in front of the slide