Which factor is present in every form of mass movement?

Mass movement is the downhill movement of rock or soil under gravity, so it requires a slope steep enough for the material to move. The angle of repose is the steepest angle at which loose material remains stable; when a slope exceeds it, mass movement can occur. Water saturation, deforestation, and ground shaking can trigger or worsen some events, but they are not present in every form.

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