What leaves behind crescent-shaped scars on a hillside and  may be caused by a layer of slippery, wet clay underneath the rock and soil on a hillside?
shearing
creep
slide
slump
Slump is the sudden movement of large blocks of rock and soil down a slope. You can see how it happens in Figure below . All the material moves together in big chunks. Slump may be caused by a layer of slippery, wet clay underneath the rock and soil on a hillside. Or it may occur when a river undercuts a slope. Slump leaves behind crescent-shaped scars on the hillside.