Fluid Dynamics of an Eruption Column

From the photographer: “A lot can be learned from observing a volcanic eruption. A simple shot of a few minutes is enough to highlight various scientific elements as shown by this image and this timelapse of a sequence of the eruption of the Etna volcano which occurred on 10 February 2022. From the video, made with 16 frames, it is possible to admire the formation of the column of ashes and lava driven by the powerful energy of the volcano. The copious emission of ash gives rise to two lightning bolts: one at the base of the eruption and a second inside the cloud. They are electrical phenomena due to the electrostatic charge that accumulates through the collision of eruptive dust particles. Two forces, in parallel action, define the upward motion of the eruption: the thrust linked to the internal pressure of the volcano and the temperature difference that tends to accompany the masses of hotter air upwards. At the same time, the weight of the ash and the cooling of the temperature combine with the upward motion, triggering vortices that act from top to bottom and appear distributed throughout the cloud structure.

By composing the shots in a static way, however, the final photograph is a sort of fluid-dynamic imprint that shows the direction followed by the individual portions of the cloud, almost as if to recall the trajectory of individual elements of a theoretical simulation. Thanks to it, it is possible to isolate different components of motion: the upward component, the direction of the wind which acts from east to west, the clockwise rotation of the column and finally the radial dispersion of dust in the highest layers of the atmosphere. And the sky, enchanted by the volcanic flows, cannot help but dance in sync with its stars that pirouette around the polar.”

Technical details:
Canon 6d, Canon 8-15mm, f/4, 30 sec, iso 640, 16 shots