Analysis of the frequency-size relationship of explosive volcanic eruptions for the past 2000 years reveals that the time-averaged eruptive mass flux of tephra from subaerial explosive eruptions is 3¿104 kg s-1. This mass flux corresponds to a thermal energy release of 4¿1010 W. Half of the long-term (>103 year) mass and thermal energy release from explosive volcanic eruptions is accounted for by eruptions of >10 km3 of tephra. ¿ American Geophysical Union 1995