A rare event was caught on camera over the weekend at Italy's Mount Etna, the most active stratovolcano in the world. The Sicilian volcano was seen spewing rare and nearly perfectly circular volcanic vortex bubbles – at some points, appearing pink in color against the sky. 

Giuseppe Barbagallo, a member of the South Etna Alpine Guides Group, told Reuters that a new pit crater formed along the volcano within the past week or so. The crater has a "perfect circled mouth," Barbagallo said, helping form the nearly perfectly circular rings of gas and vapor. According to Reuters, many locals are now referring to Etna as "Lady of the Rings" in light of the event. 

"This is a special phenomenon," they said. "We cannot see something like this every day." 

These rings can be traced back to as early as 1724, according to research published last year in Scientific Reports. The paper said that it's unknown what exact physical conditions allow volcanic vortex rings to form. After creating model simulations, scientists learned that the formation of the rings "requires a combination of fast gas release from gas bubbles at the top of the magma conduit and regularity in the shape of the emitting vent." 

Boris Behncke, a volcanologist at the National Institute of Geophysics and Volcanology in Catania, told a local news outlet that Etna produces more volcanic vortex rings than any other volcano on Earth. 

"The Bocca Nuova crater emitted thousands of these rings and it is continuing," Behncke said, according to a translation. 

Behncke tweeted last week that the rings started forming from the crater during the evening of April 2, saying the volcano was emitting "unprecedented quantities" of the rings, saying the next day that it was a "phenomenon never seen like this before." 

"Someone said, 'maybe because we receive so much bad news lately, Etna has decided to do something simply beautiful,'" he tweeted. 

Etna is one of the most active volcanoes, and the last significant activity was recorded last December, according to the Smithsonian Institution National Museum of Natural History's Global Volcanism Program. That activity was recorded from December 20 to 26, when a "swarm" of "light-gray ash emissions rose from Bocca Nuova Crater." There were a couple of crater explosions, resulting in ash plumes, the monitoring program said. 

In:
• Volcano
• Italy
• Mount Etna

Li Cohen

Li Cohen is a social media producer and trending content writer for CBS News.