A lahar (English pronunciation: /lhr/) is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley. The term is a shortened version of "berlahar" which originated in the Javanese language of Indonesia. "Lahar" is an Indonesian word that describes volcanic mudflows or debris flows. Lahars have the consistency, viscosity and approximately the same density of concrete: fluid when moving, then solid when stopped. Lahars can be huge: the Osceola lahar produced 5,600 years ago by Mount Rainier in Washington produced a wall of mud 140 metres (460ft) deep in the White River canyon and covered an area of over 330 square kilometres (130sqmi) for a total volume of 2.3 cubic kilometres (0.55cumi), and can bulldoze through virtually any structure in its path. A lahar is capable of carving its own pathway, making the prediction of its course difficult. A Lahar quickly loses...
