Sicilian volcano is blowing smoke rings in the sky. What are volcanic vortex rings?

Subject: Geography

Section: Physical geography

Context:

Since last week, Mount Etna, the largest volcano in Europe, and among the world’s most active and iconic volcanoes, has been sending up almost perfect rings of smoke into the air.

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The rings are a rare phenomenon that scientists refer to as volcanic vortex rings, which are produced roughly in the same way as the smoke rings that some cigarette smokers are able to blow out of their mouths.
Etna is in almost constant activity, and has seen, since the year 1600, at least 60 flank eruptions and many more summit eruptions.
In recent years, summit eruptions have occurred in 2006, 2007-08, on two occasions in 2012, in 2018, and 2021; flank eruptions have taken place in 2001, 2002-03, 2004-05, and 2008-09.

About Mount Etna:

Mount Etna, which is sometimes referred to simply as Etna, is an active volcano on the east coast of Sicily, the largest island in the Mediterranean Sea, lying just off the toe of the Italian “boot”.
Etna’s peak is the highest in Italy south of the Alps, and it is Europe’s largest and one of the most active volcanoes.
Etna’s summit has five craters, which are responsible for most of the volcano’s eruptions.
There are also “flank” eruptions that occur out of 300-odd vents of varying sizes along the slopes of the mountain.
Etna has been a World Heritage Site since 2013.
According to UNESCO, the volcano’s eruptive history can be traced back 500,000 years. At least 2,700 years of this activity has been documented.

What are volcanic vortex rings?

Vortex rings are generated when gas, predominantly water vapor, is released rapidly through a vent in the crater.
The rings are produced by the explosion of gas bubbles within a narrow conduit, which shoots the gas at high speed toward the surface.
The vent that has opened up in Etna’s crater is almost perfectly circular, so the rings that have been seen above the mountain since April 2 are also circular.
The phenomenon was first observed at Etna and Vesuvius in Italy in 1724, and has been documented in an engraved plate from 1755.
In more recent times, volcanic vortex rings have been observed at volcanoes such as Redoubt in Alaska, Tungurahua in Ecuador, Pacaya in Guatemala, Eyjafjallajökull and Hekla in Iceland, Stromboli in Italy, Aso and Sakurajima in Japan, Yasur in Vanuatu, Whakaari in New Zealand, and Momotombo in Nicaragua.

The volcanic smoke rings were produced in the same way as dolphins blow bubble rings.
They compress the water in their mouths, and using their tongue they push it out of their mouths and create such a pressure that it forms a ring.
The rings can remain in the air for up to 10 minutes, but tend to disintegrate quickly if conditions are windy and turbulent.