Tephra 06 : Material ejected into the air during a volcanic eruption. The particles can be as small as volcanic ash or as large as boulders and blocks, tens of feet in diameter
National Atlas of the United States, Geologic Hazards (Article with illustration), US Department of the Interior, USA 2011. http://www.nationalatlas.gov/articles/geology/a_ge ohazards.html, (ND/ Erthq - Amer) {138}