The process that causes mud to move quickly down the side of a hill is called a mudslide. Mudslide occurs when a large mass of mud, water and debris becomes dislodged from a slope and flows rapidly downhill. It is a type of mass movement that can cause significant damage to infrastructure, property and life. Mudslides are often caused by heavy rainfall or snowmelt that saturates the ground, making it unstable. Other factors that can contribute to mudslides include steep slopes, lack of vegetation, and earthquakes.