A lahar is a violent 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.
A lahar travels down a river valley in Guatemala near the Santa Maria volcano, 1989
Excavated 9th century Sambisari Hindu temple near Yogyakarta in Java, Indonesia. The temple was buried 6.5 metres under the lahar volcanic debris accumulated from centuries of Mount Merapi eruptions.
Mudline left behind on trees on the banks of the Muddy River after the 1980 eruption of Mount St. Helens showing the height of the lahar
The aftermath of a lahar from the 1982 eruption of Galunggung, Indonesia
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 3 meters/minute to 5 meters/second. 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.
Mailboxes caught in a mudflow following the May 1980 Mount St. Helens volcanic eruption.
The Mameyes mudflow disaster, in barrio Tibes, Ponce, Puerto Rico, was caused by heavy rainfall from Tropical Storm Isabel in 1985. The mudflow destroyed more than 100 homes and claimed an estimated 300 lives.
