[link to www.wired.com]
BY ERIK KLEMETTI 04.16.1312:54 PM
... Now Etna has produced these “smoke” rings before, but it is always impressive when it does as they seem so perfectly formed. Other volcanoes have produced them as well, including Eyjafjallajokull during its 2010 activity. Not much is known about exactly how these rings form, but it could be related to brief explosions in a confined vent that allows for that “puff”, which then expands into a ring. Be sure to check out the great video (with sound)
from Dr. Boris Behncke from the April 11-12 paroxysm at Etna — definitely a spectacular view of strombolian explosions in the New Southeast Crater.