The main force that causes all mass movements is gravity. Gravity pulls objects towards the centre of the Earth, and this force can cause objects to move downhill. Other factors that can contribute to mass movements include:

- Water: Water can help to lubricate the surface of the ground, making it easier for objects to move.

- Wind: Wind can exert a force on objects, pushing them in a particular direction.

- Earthquakes: Earthquakes can cause the ground to shake, which can destabilize objects and cause them to move.

- Volcanic activity: Volcanic eruptions can produce large amounts of ash and debris, which can flow downhill.

Mass movements can be a major hazard to human life and property. They can destroy homes, roads, and bridges, and they can also cause injuries or death.