Rainfall can lead to mass movement through three different mechanisms. Often these mechanisms do not act alone. The saturation of soil materials increases the weight of slope materials which then leads to greater gravitational force. Saturation of soil materials can reduce the cohesive bonds between individual soil particles resulting in the reduction of the internal strength of the hillslope. Lastly, the presence of bedding planes in the hillslope material can cause material above a particular below ground level to slide along a surface lubricated by percolating moisture.
Earthquakes are another common mechanism that can trigger mass movement.
The seismic waves produced by earthquakes vibrate slope materials. This vibration can lead to failure by increasing the downward stress or by decreasing the internal strength of the hillslope sediments through particle movement. Water, Sediment Transport, and Hillslopes Rainsplash is a microscale process that can be quite effective in moving material on slopes. The impact of rain droplets on the soil surface often detaches individual grains of soil moving them some distance from their source. On flat surfaces, the effect of rain drop impact is to redistribute the material without any net transport in a particular direction.