A significant eruption is classified as one that meets at least one of the following criteria: caused fatalities, caused moderate damage (approximately $1 million or more), Volcanic Explosivity Index (VEI) of 6 or greater, generated a tsunami, or was associated with a significant earthquake.
This dataset is from http://www.ngdc.noaa.gov/nndc/servlet/ShowDatasets?dataset=102557&search_look=50&display_look=5 http://www.ngdc.noaa.gov/docucomp/page?xml=NOAA/NESDIS/NGDC/MGG/Hazards/iso/xml/G10147.xml&view=getDataView&header=none