Volcano Watch: Colorful plumes — can we see volcanic gases?

CHRISTOPH KERN/U.S. Geological Survey

A volcanic gas cloud over the lower East Rift Zone on May 19. In this picture, the sun is illuminating the volcanic gas plume from behind. The plume appears orange in color, as the blue component of the sunlight has been preferentially removed by scattering on tiny sulfate aerosols. This looks a bit like a sunset, but note that the meteorological clouds below the volcanic plume do not show this discoloration.

ALLAN LERNER/U.S. Geological Survey volunteer

Fissure 8 on June 5. The sun is behind the observer taking this photo, making the plume appear bluish because of sunlight being scattered by tiny sulfate aerosols. The gas plume is against a very dark cloud background so no backlighting is affecting the plume view.

*NOTE: This week’s Volcano Watch article was submitted Sunday, June 17. Volcano Watch normally appears every Sunday in the Tribune-Herald.