On 25 May at around 5pm, an eerie black ring of cloud loomed over the town of Tigre in the Buenos Aires province of Argentina. While it remained in the sky for less than a minute, locals were stumped by its brief but hypnotic appearance. And we might say it a lot - and it hurts us for various reasons every time - but the explanation for this strange phenomenon was not aliens. It was a byproduct of zombie-themed fireworks.
Turns out the smoke ring was the result of a fireworks display let off during a performance at the nearby Parque de la Costa amusement park. Rather appropriatey, that performace was called "Zombie Invasion", so we now have a great candidate for how we can signal to each other that there is one in the event that all communication technology fails in the process. The weather conditions on the day made the black ring particularly visible in the sky, against a flat, greyish background of rainclouds.
While it looks super-weird, the black ring phenomenon is actually fairly common. A similar one with a diameter of around 100 metres was seen almost 2 km above the ground in Kazakhstan last April, said to be caused by a nearby factory, and last year, one appeared in the sky above a town in the UK. "A similar black ring caused a sensation last year when British schoolgirl Georgina Heap recorded video of the phenomenon on her smartphone," 9News reports. "'The 'Black Ring of Leamington Spa' was eventually traced to a fireworks test at nearby Warwick Castle, located in the county town of Warwickshire."
Here's some more footage of last week's event: