Volcanic ash frozen within a glacier mill

Glacier mill (or moulin), Breiðamerkurjökull, Southern Iceland (February 2014). At the end of the polar winter, the subglacial rivers dig their way through the Europe's largest glacier and reveal sinuous ice caves. The mineral lights of the cave oscillate between the blue of the pure ice, the white of the fresh snow and the black of the volcanic ash trapped within a glacier mill.