SCIENTIFIC AMERICAN - It was a cloudy July afternoon in Alaska's Kobuk Valley National Park, part of the biggest stretch of protected wilderness in the U.S. We were 95 kilometers (60 miles) from the nearest village and 400 kilometers from the road system. Nature doesn't get any more unspoiled. But the stream flowing past our feet looked polluted. The streambed was orange, as if the rocks had been stained with carrot juice. The surface glistened with a gasolinelike rainbow sheen. “This is bad stuff,” said Patrick Sullivan, an ecologist at the University of Alaska Anchorage.
Less than a dozen meters away the stream flowed into the Salmon River, a ribbon of swift channels and shimmering rapids that winds south from the snow-dimpled dun peaks of the Brooks Range. This is the last frontier in the state known as “the last frontier,” a 1,000-kilometer line of pyramidlike slopes that wall off the northern portion of Alaska from the gray, wind-raked Arctic Coast.
This past summer a researcher spotted two orange streams while flying from British Columbia to the Northwest Territories. “Almost certainly it is happening in other parts of the Arctic,” said Timothy Lyons, a geochemist at the University of California, Riverside, who's been working with Dial and Sullivan.