Lahars - John Seach
(Volcanic Debris and Water Flow)

A lahar is a flow of volcanic debris and water which deposits as a poorly sorted mass. Lahars are the second most dangerous type of volcanic event after pyroclastic flows. The mixture of water and debris creates a viscous and abrasive mixture.
Lahars are only produced at volcanoes. Non-volcanic flows are called Debris Flows. A mudflow is a fine similar to a lahar but consists of fine grained sediment.