A body of rock with characteristics that are the same. Typically the facies is a unit of rock that was formed under conditions reflecting a specific emplacement process e.g., a single?lava flow, an ash-flow tuff, a lahar
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}