Largest steam rings

The active volcano Mount Etna, Sicily, is the tallest and most active volcano in Europe. A complex physical process is causing it to emit huge steam rings, similar to more familiar smoke rings. The steam rings of Mount Etna are around 200 m 650 ft across and can last up to around 10 minutes, as they slowly drift upwards to a height of up to 1000 m 3,300 ft above the volcanic vent. The rings are thought to be due to unusual geometric conditions in the shape of the volcanic vent that produces them. Major volcanic activity could alter the shape of the vent and prevent further steam ring formation.