A series of astounding images of a 'dirty thunderstorm', captured by volcano film-maker Marc Szeglat earlier this month, show the earth’s power at its most terrifying and breath-taking.
Dirty thunderstorms are a rare phenomenon, associated with large volcanic eruptions.
But unusually and perhaps uniquely, they occur regularly at Sakurajima volcano in Japan, one of the most active volcanoes in the world.
On his latest filming expedition, Mr Szeglat was thrilled to witness one of the volcano’s dramatic eruptions and lightning displays.
“The term ‘dirty thunderstorm’ means lightning in an eruption cloud from a volcano,” explains the German film-maker, who has been travelling to active volcanoes for almost 20 years.
“Sakurajima is the only volcano I know that has frequent lightning in daily eruptions,” he says. But why that happens so often here is unclear.
“In a normal thunderstorm ice crystals collide and generate electric charges, which results in lightning. In an eruption cloud ash particles collide instead of ice crystals.”
To get his extraordinary images of the erupting volcano, Mr Szeglat and a friend waited for the moment the lightning struck in the volcano’s eruption column, while anticipating the shockwave and sound emitted from the huge eruption.
“There was a delay of several seconds between seeing the eruption and the arrival of the shockwave and sound. These seconds were very exciting. I didn’t know how strong the shockwave would be.
“Sometimes the shockwaves are so strong, that they can shake the tripod and camera by the pressure.
“In this case I felt the breath of wind from the interior of the earth like an extremely brief squall [a sudden strong wind].
“After that, my friend Martin and I laughed out loud, and were very happy.”
The lightning seen during the explosive eruption of Iceland’s Eyjafjallajökull volcano in spring 2010 may have been another example of a dirty thunderstorm. An explosive eruption happens when gas becomes trapped in magma, and pressure builds until the magma erupts explosively out of the volcano.
From 11 to 20 May 2010, experts reported intense lightning activity in the volcano’s plume, including sparks at the base of the massive plume and large thunderbolts.