Precambrian 1 : All geologic time before the Paleozoic era. This includes about 90% of all geologic time and spans the time from the beginning of the earth to 543 million years ago. (GSA 1999 Geologic Timescale)
U.S. Department of the Interior, U.S. Geological Survey, US Geological Society (USGS), Glossary of Volcano and Related Terminology, USGS/Cascades Volcano Observatory, Vancouver, Washington, USA 2006. http://vulcan.wr.usgs.gov/Glossary/volcano_termino logy.html, (ND/ Volc Sci - Amer) {493}