General term for magma (molten rock) that has been erupted onto the surface of the Earth and maintains its integrity as a fluid or viscous mass, rather than exploding into fragments
U.S. Geological Survey, U.S. Department of the Interior, Volcano Hazards Program, Glossary, Washington, DC, USA 2011. http://volcanoes.usgs.gov/vsc/glossary/alluvium.ht ml, (ND/ Volc Emr - Amer) {795}