____________occur(s)when a semicoherent mass of material moves downslope on a failure surface.

Question

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Slumps occur when a semicoherent mass of material moves downslope on a failure surface. Slumps typically occur in cohesive soils and can result in the formation of a curved scarp at the top of the slump and a straight boundary at the bottom.

Avalanches (A) are a rapid movement of snow or ice down a mountainside. 
Creep (C) refers to the slow downhill movement of soil and rock due to gravity. 
Solifluction (D) is a type of creep specific to permafrost areas where the soil thaws during the summer and moves downslope.

____________Occur(s)when a Semicoherent Mass of Material Moves Downslope on a Failure