photo #5440713

This unusual ring of cloud, likely with ash particles mixed in, is known as a volcanic vortex ring. It was spotted by Andrea Libero Carbone (Member 46,943) over Mount Etna, Sicily, Italy. The active volcano is currently producing several rings like this a day from a vent in its Bocca Nuova crater. A volcanic vortex ring is created when small gas bubbles join together in the magma far below the surface and rush up the vent’s conduit as a single ‘slug’ of pressurised gases that bursts from the vent into the surrounding air. If the shape of the channel is straight enough to allow the slug to pick up enough speed, and if its vent is circular enough, the friction at the channel sides makes the rising gases form a spinning ring as they emerge. The low pressure within this ring-shaped vortex can cool the gases enough for some of the water vapour among them to condense into droplets of cloud. Volcanic emissions often contain ash, onto whose tiny particles the water droplets form. The volcanic vortex ring appears brown or grey when there is a lot of ash present. It looks white like Andrea’s when it’s mostly just made of water droplets.