Fragments ejected explosively from a volcanic vent on an arcuate, ballistic trajectory, much like a cannonball. Typically are found as part ofcinder cones formed over mafic vents
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}