Mass movement

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Mass movement:

Mass movement is the downslope movement of rock, soil, or mud, under the influence of gravity. Rainfall is usually a trigger but the scale of mass movement is determined by the extent of the weathering.

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Rock fall:

Bare, well-jointed rocks re prone to freeze-thaw weathering, which results in the rocks losing contact with the cliff face and falling to the bottom of the cliff. The fallen rocks collect at the bottom as a scree slope.

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Sliding:

Slides happen along a straight line of weakness such as a fault or bedding plane. They occur on steep cliffs previously weakened by weathering. Heavy rain infiltrates the soil and percolates own into the rock. The heavy, saturated rock now slips along this straight plane, maintaining contact the whole way. It starts by tearing away the vegetation at the top, then slides down the lubricated plane

Rock slides are when large pieces of rock slide down the cliff along a straight slip plane.

Mud slides are wet, rapid, and tend to occur on steep slopes. Vegetation is sparse and so mud cannot be held in place.

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Slumping:

Slumping is the movement of material along a concave (curved) slip plane, material rotates into the cliff face as it slips. It occurs when a permeable material (e.g. gravel) sits on an impermeable material (e.g. clay). In heavy rainfall, the permeable material becomes saturated and the increased weight causes a slip plane to develop. The permeable material moves along this plane under gravity to the bottom of the cliff.