Eruptive processes leading to the most explosive lava fountain at Etna volcano: The 23 November 2013 episode

The 23 November 2013 lava fountain at Etna volcano was the most explosive of the last 44 episodes that have occurred at Etna in 2011-2013. We infer the total magma volume erupted by thermal images analysis and show that it was characterized by a very high time-averaged-discharge-rate (TADR) of similar to 360 m(3) s(-1), having erupted similar to 1.6 x 10(6) m(3) of dense-rock equivalent magma volume in just 45 min, which is more than 3 times the TADR observed during previous episodes. Two borehole dilatometers confirmed the eruption dynamics inferred from the thermal images. When compared to the other lava fountains, this episode can be considered as the explosive end-member. However, the erupted volume was still comparable to the other lava fountain events. We interpret that the 23 November explosive end-member event was caused by more primitive and gas-rich magma entering the system, as demonstrated by the exceptional height reached by the lava fountain.