the sun is illuminating the volcanic gas plume from behind
Detailed Description
LERZ Fissure 8 on June 5, 2018 - The sun is behind the observer taking this photo, making the plume appear bluish due to sunlight scattering by tiny sulfate aerosols. The gas plume is against a very dark cloud background, so that no backlighting is affecting the plume view.
Sources/Usage
Public Domain.