Bob Maysmor was climbing Villarrica volcano in the Andes of southern Chile when a ring appeared in the sky. This volcano has active vents, one of which created this volcanic vortex ring. It consists of a mix of volcanic ash and cloud, and it results from the volcano’s hot gasses taking on a particular kind of spin.

Gas bubbles in the magma far below the surface join together and start to travel up the vent’s conduit as a single ‘slug’ of pressurised gases, which eventually bursts from the vent into the surrounding air. A ring can appear when the channel has a circular shape and is straight enough for the slug to pick up speed. Friction at the sides of the channel causes the gases to slow down at the edges but not in the middle, setting up a ring-shaped vortex as the gasses emerge. Low pressure within this vortex can cool the gases enough for the water vapour within to condense, often onto any particles of volcanic ash, and appear as a cloud ring. Villarrica volcano is named after the town below, and the name translates to ‘place of wealth’ in English. Makes sense, therefore, that Bob’s volcanic vortex ring appears to have a cloudy diamond attached.