Final answer:
Rotational Slump Failures typically occur in soil or weathered rock masses, often due to saturation from rainfall, earthquake stresses, or volcanic activity, which destabilize the slopes and trigger a sliding movement along a curved surface.
Step-by-step explanation:
Rotational Slump Failures commonly occur in C) Soil or weathered rock masses. These types of movements typically involve a rotation of material along a curved surface. The factors leading to such failures often include saturation of the slope material due to heavy rainfall, which can also cause over-steepened slopes, or earthquake-induced stresses in the slope material. Earthquakes of magnitude 4.0 and greater have been known to trigger landslides, contributing to these failures. Additionally, volcanic eruptions can lead to instability in slopes by producing loose ash deposits and subsequent debris flows. Excessive accumulation of water or snow, excessive weight from stockpiled materials, and human-made structures can also increase the stress on weak slopes, prompting a slump.