An Arctic fox lopes over snowy ground in Prudhoe Bay in an image shot before 1977 when oil wells began to sprout up across Alaska's North Slope. Today, Prudhoe Bay is considered the largest oil field in North America and the 18th largest field in the world, though output has fallen by 75 percent since its peak in 1987.

(Photograph shot on assignment for, but not published in, "Will Oil and Tundra Mix?" October 1971, National Geographic magazine)