Lahar Flow From La Soufrière Volcano. 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. | Mikey Hutchinson

Progression of the 19 January 2002 lahar front in the Curah Lengkong river, Semeru volcano, Indonesia. Channel is 25 m across. Credit: Franck Lavigne (distributed via imaggeo.egu.eu). Un #lahar é una colata di fango formata da materiale piroclastico che defluisce verso il basso nei bordi un vulcano. Video caricato dall'European Geosciences Union. | Scienze della Terra

One of the most tragic volcanic events of the 20th century occurred in Colombia in 1985, when an eruption of Nevado del Ruiz generated lahars that swept down river valleys and destroyed communities in its path. With little warning, the volcano began erupting on the afternoon of November 13, 1985. Ash and muddy rain began to fall. Communities were alerted but no formal decision was made to evacuate. Later that evening, a stronger eruption produced pyroclastic flows and surges that mixed with snow

Mount St. Helens erupted #onthisday in 1980. Hear the harrowing stories of the people who were there in Make It Out Alive: https://bitly.com/3dryeH0 | Smithsonian Channel Aviation Nation