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“The ring is very similar to the ‘smoke ring’ created by people who are able to smoke,” Boris Behnke, a volcanologist at Italy’s National Institute of Geophysics and Volcanology’s Etna Observatory, said in an email on Monday.
He explained that these rings were formed by magma (gas-filled lava) bubbling beneath a cylindrical vent that opened toward a crater that formed on Etna’s surface last week.
“Imagine a very narrow cylindrical channel, and at a certain depth there is magma,” Behnke says. “Sometimes bubbles form on the surface of the magma, which burst, sending a mass of gas through the conduit at high velocity.”
When a pulse of gas compresses a narrow circular vent, it takes on a ring-like shape and forms a puff. “No more irregularly shaped vents will produce rings,” he said.
He said the gas ring is made up of about 80 percent water vapor, with the remaining 20 percent mainly made up of sulfur dioxide and carbon dioxide. It is the water vapor that gives the ring its white hue, resembling a smoke ring.
Mount Etna first erupted about 500,000 years ago. Since then, he has frequently dazzled tourists and Sicilians with its lava flows, including a lava fountain that reached nearly a mile high in 2015.
Its volcanic activity also caused severe disruption and damage, releasing dangerous ash clouds that forced the closure of nearby airports and covered villages in ash. In 1979, an explosion in the fluke crater killed nine tourists, but fatalities are rare. In an explosion in the 17th century, Etna buried the town of Nicolosi, destroyed much of the city of Catania, and shot lava into the ocean 29 miles away from her.
Behnke said the ring is not an unusual phenomenon. Mount Etna is “the most prolific volcano on Earth in terms of steam rings,” he says.
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