A lahar is a type of mudflow or landslide composed of pyroclastic material and water that flows down from a volcano, typically along a river valley. The term "lahar" originated in the Javanese language of Indonesia. Description Lahars can be best described as volcanic mudflows. They may not necessarily be caused by volcanic activity, but at the very least do originate from some type of volcanism. Lahars have the consistency of concrete: fluid when moving, then solid when stopped. Lahars can be… (More on Lahars)