The agent of erosion for creep is gravity. Creep is the slow, continuous, downslope movement of soil and rock due to the pull of gravity. It occurs when the shear stress (the force per unit area that is applied parallel to the slope) exceeds the shear strength (the ability of the soil or rock to resist shear stress) of the material. Creep can be caused by a variety of factors, including the weight of the material itself, the presence of water or other fluids in the material, and temperature variations.