Wildfires. Landslides and Mudslides Landslides occur when masses of rock, earth or debris move down a slope. Mudslides, also known as debris flows or mudflows, are a common type of fast-moving landslide that tends to flow in channels.andslides are caused by disturbances in the natural stability of a slope. They can happen after heavy rains, droughts, earthquakes or volcanic eruptions. Mudslides develop when water rapidly collects in the ground and results in a surge of water-soaked rock, earth and debris.