New formulae for estimating lava flow volumes at Mt. Etna Volcano, Sicily

A new data set of Etna lava flows erupted since 1868 has been compiled from eight topographic maps of the volcano published at intervals since then. V olumes of 59 flows or groups of flows were measured from topographic differ ence maps. Most of these volumes are likely to be considerably more accurat e than those published previously. We cut the number of flow volumes down t o 25 by selecting those examples for which the volume of an individual erup tion could be derived with the highest accuracy. This refined data set was searched for high correlations between flow volume and more directly measur able parameters. Only two parameters showed a correlation coefficient of 70 % or greater: planimetric flow area A (70%) and duration of the eruption D (79%). If only short duration (<18 days) flows were used, flow length cubed , L-3, had a correlation coefficient of 98%. Using combinations of measured parameters, much more significant correlations with volume were found. Dh had a correlation coefficient of 90% (h is the hydrostatic head of magma ab ove the vent), and AW/E, 92% (where W is mean width and E is the degree of topographic enclosure), and a combination of the two root DhAW/E, 97%. Thes e latter formulae were used to derive volumes of all eruptions back to 1868 to compare with those from the complete data set. Values determined from t he formulae were, on average, lower by 16% (Dh), 7% (AW/E), and 19% (root D hAW/E).