I've seen twice the (sortof) inverse of this.
A power station cooling plume rising, disappearing (becoming invisible due to temps or whatever), then turning back into a plume about the clear layer.
There are only two ways that I can think of to improve these pictures.
First, at the very bottom of the plume is Osama bin Laden's present hide-out, and,
Second, that's a nuke going off over it, not a "mere" volcanic eruption...