Acidic fog drifts over the dormant volcanoes of Kruzof Island in southeast Alaska. The pH of this fog was measured at 3.9, which is about as acidic as orange juice. The source of the acidity is thought to be the oxidation of natural hydrocarbon and sulfide gases emitted by regional forest, bog, and marine ecosystems. This photograph was taken at 11:00 p.m. on 1 July 1986.
Image courtesy of Lee Klinger/UCAR