Mount Etna, Europe’s largest volcano, puffs up rings of gas

Mount Etna, Europe’s largest active volcano, puffed out a string of near-perfect rings over the weekend - prompting comparisons to smoke rings, or a fleet of giant flying saucers floating gently into the blue sky.

Etna formed the“volcanic vortex rings,” as they are known to scientists, through the rapid release of gas and vapors from a newly formed crater.

“The rings look pretty much like the ‘smoke rings’ produced by an able smoker,” Boris Behncke, a volcanologist at the Italian National Institute of Geophysics and Volcanology’s Etna observatory, said Monday in an email.

He explained that the rings were formed by magma - molten rock with gas - bubbling beneath a cylindrical vent that opened into a crater that formed on Etna’s surface last week.

“Imagine a very narrow, cylindrical conduit, within which, at a certain depth, there is magma,”Behncke said.“Every so often, a bubble forms at the surface of the magma, bursts, and sends a slug of gas at high speed through that conduit.”

As pulses of gas squeeze up the narrow, circular vent, they take on its ring-like shape - forming the puffs.“You won’t get rings from a more irregular shape of the vent,”Behncke said.

The gas rings are composed of about 80 percent water vapor, with the remaining 20 percent mostly made of sulfur dioxide and carbon dioxide, he said. The water vapor is what gives the rings their white hue, making them resemble smoke rings.

According to Behncke, the rings are not particularly rare phenomena. Etna is “the most prolific volcano on this planet in terms of vapor rings,” he said.