29 April 1988
Vol 240, Issue 4852

About The Cover

St. Kevin Gulch, a mountain stream near Leadville, Colorado, which receives acidic, metal-enriched drainage from an abandoned mine. Hydrous iron oxides impart the bright orange color to the stream; photoreduction of these oxides and dissolved ferric iron causes large increases in dissolved ferrous iron, Fe2+, during the day. See page 637. [Kenneth E. Bencala, U.S. Geological Survey, Menlo Park, CA]