Violence and Volume: an experimental study of CO2 driven eruptions of Colli Albani

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The Pozzolane Rosse eruption (457 ka) of the Colli Albani volcano complex in Italy was a high volume explosive eruption of foiditic, low viscosity, low SiO2, mafic magma. The composition of the P. Rosse magma was also CO2- and CaO-rich. The volume of this eruption falls outside the range of explosive eruptions on a plot of eruption volume as a function of SiO2 content. Here we will determine the viscosity of foiditic melts for the first time; and also determine the effect of CO2 on the viscosity of these melts.The goal is to obtain an insight into the reason why such a low SiO2 melt erupted with such violence and volume. Such eruptions usually only occur in SiO2–rich magmas, as bubbles can not escape easily from high-viscosity magmas. In general, it would be expected that the viscosity of the foiditic melt was so low that CO2 bubbles would effusively escape.