mudflow

thumb|Mailboxes caught in a mudflow following the May 1980 Mount St. Helens volcanic eruption.

A mudflow, also known as mudslide or mud flow, is a form of mass wasting involving fast-moving flow of debris and dirt that has become liquified by the addition of water. Such flows can move at speeds ranging from . Mudflows contain a significant proportion of clay, which makes them more fluid than debris flows, allowing them to travel farther and across lower slope angles. Both types of flow are generally mixtures of particles with a wide range of sizes, which typically become sorted by size upon deposition.