Above certain volcanoes, so called "dirty thunderstorms" develop and lightning repeatedly strikes within the clouds of ash spewing from their craters.
It’s a dramatic and rare event that occurs at a few select locations around the world, including in northern Patagonia and Japan. Dirty thunderstorms are caused by the particles of ash, which are ejected through fine cracks in the magma at great speed and become electrically charged. These ash particles create massive, super-charged ash clouds that trigger bolts of lightning.
But while these events happen naturally, they can be difficult to see with the naked eye or be captured on a single camera. It requires special techniques to reveal and portray their true extraordinary nature.
Timelapse photography compresses time to show how the ash cloud builds and spreads very dramatically over many hours, but lightning is difficult to record using timelapse photography, as this footage of the Calbuco eruption reveals.
The strikes are too quick to register. And while long exposure still photographs can capture lightning strikes, they can’t adequately convey the dynamic force of the eruption, since they blur the fast moving ash cloud. “While visual observations including photos and video are very interesting they miss much of the lightning,” states the Encyclopedia of Volcanoes.
So, alongside local cameramen, the BBC Earth crew recorded the Calbuco eruption on multiple cameras in timelapse and ultra high definition (UHD). It was an amazing eruption that made world news, and put on a supreme volcanic lightning show. Our aim was to represent the stunning visual spectacle of an eruption.
We took timelapse images from the Calbuco volcano filmed in early 2015 and the lightning shots were superimposed onto the erupting cloud. The lightning shots were taken by an award-winning Chilean photographer, of a nearby Patagonian volcano, Cordón Caulle four years earlier during its eruption, using long exposure techniques. The Cordón Caulle volcano eruption was a very similar event to the Calbuco volcano this year.
These elements had to be combined to create a series of composite images, showing both the size and scale of a Patagonian volcanic eruption, its ash cloud and the repeated strikes of lightning that can occur within it, over many hours.
According to volcanologist Dr Hugh Tuffen, who worked with the team, this composite sequence "vividly illustrates a little understood process... by putting this together you can see a vivid representation of real events."
By combining local knowledge, expert advice, and state of the art camera and post production techniques we have been able to reveal to audiences the wondrous scale of an epic natural phenomenon.