Mount Etna in Sicily has been blowing spectacular ‘smoke rings’ into the sky since Wednesday. The volcano, which towers over the historic port city of Catania, is the largest in Europe and one of the most active in the world. It is a designated UNESCO World Heritage Site. The ‘volcanic vortex rings’, a rare phenomenon that is generated by the combination of rapid gas release and the vent shape, spewed out of a new crater that opened on Tuesday on Etna’s summit. Boris Behncke, volcanologist at the National Institute of Geophysics and Volcanology in Catania Boris, explained in a Facebook post th…