Global Volcanism Program | Image GVP-01719
Lahars are water-saturated mixtures of volcanic debris that sweep down volcanoes and onto valley floors far beyond. These lahars from the 1982 eruption of Galunggung volcano on the Indonesian island of Java caused extensive damage to houses and croplands. Lahars can remain a hazard long after an eruption ends, when heavy rainfall redistributes deposits produced by the eruption.
Photo by Robin Holcomb, 1983 (U.S. Geological Survey).