Eruption dynamics of the 23 February 2013 event at Mt. Etna

Abstract

Volcanic activity atMt. Etna in the last decade hasmostly beenmanifested by sequences of short paroxysmal episodes characterised by powerful lava fountains and high eruption columns. On the 23 February 2013, an exceptionally intense episode occurred at the New South-East Crater, producing a fountain N800 m high (among the highest ever recorded at Etna) and a ~9 km eruption column that dispersed ash N400 kmfromthe vent. Textural and petrographic analyses of lapilli revealed that magma erupted during the high-intensity phase is characterised by lowmicrolite contents (b7 area%), high vesicularity (76–83%), and high vesicle number densities (6–8.2 × 106 cm−3). The short-lived initial Strombolian explosions removed viscous magma from the conduit, enabling the rapid ascent of gas-rich, microlite-poor magma and the eruption of an 800 mhigh fountain and 9 kmhigh eruption column. For the 23 February eruption, the high vesicularity and lowmicrolite content of the pyroclasts support the hypothesis that volatile-rich magma was the driver of the high intensity lava fountain. This eruptive event, along with three other recent events at Etna over the last 15 years, can be defined as subplinian based on eruption rate and column height, but also generated incandescent 800–1000 m fountains. For these reasons, we propose to term this event, and others at Etna characterised by similar eruption features and parameters, as subplinian fountaining events.