Often occurs in areas where the rocks are highly fractured, particularly if the fracture surfaces or bedding planes dip downslope. Often triggered by an earthquake. Mudflow Rapid type of mass wasting that involves a flowage of debris containing a large amount of water. Most characteristic of semiarid mountainous regions. Tend to follow canyons and gullies.
Lahars are mudflows on the slopes of volcanoes, often accompanying eruptions.
E.g., Mount St. Helens. Downslope movement of water-saturated soil on hillsides in areas of deep weathering. Moves relatively slowly and may be active for periods ranging from days to years. Imperceptibly slow downslope movement of soil and regolith. Can take place on even gentle slopes and is extremely widespread.