Etna makes almost perfect circles in the sky, a very rare phenomenon. The phenomenon, quite rare, occurs when gas bubbles rise along the magma chamber along conduits and explode.
Volcanologist Boris Behncke, who works at the National Institute of Geophysics and Volcanology (INGV) in Catania, points out that since April 2, Etna has been breaking all records by emitting “unprecedented quantities of gas rings”. The gas must escape from a circular or slightly crushed area, without too many irregularities, which would destroy the gas.