These ghostly hoops have been spotted above volcanic events around the world. But how they form has long been a mystery.

Mount Etna has erupted on Monday, sending a kilometres-high plume of ash into the sky and sending tourists fleeing from the popular World Heritage area. Italy’s National Institute of Geophysics and ...

Tours are returning to the slopes of Mount Etna after its largest eruption in four years sent tourists fleeing from a vast column of gas and ash on Monday. After footage of the dramatic eruption ...

Italy's Mount Etna produced a spectacularly explosive eruption Monday morning, sending a ripple of reddish clouds down from its summit. The soaring ash rose to form a mushroom cloud high above Etna, ...