Any type and size of rock fragment that is forcibly ejected from the volcano and travels an airborne path during an eruption (including ash, bombs, and scoria)
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}