Eruption 4 : When solid, liquid, or gaseous volcanic materials are ejected into the Earth's atmosphere or surface by volcanic activity. Eruptions may occur as quiet lava flows or violent explosive events
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}