Bingham Canyon, The Mountain That Became a Hole

Somewhere southwest of Salt Lake City, a mountain has been replaced by a hole. Bingham Canyon Mine is the largest man-made excavation in the world, about two and a half miles wide and three-quarters of a mile deep. From the observation deck, the trucks working the terraced pit floor look like toys. Each truck carries a payload of three hundred tons. The pit is so large it has its own weather.

The canyon was first settled by Mormon farmers in eighteen forty-eight, who recognized its grassy bottom as winter pasture. Placer gold was found in eighteen sixty-three, and soldiers from Colonel Connor's Camp Douglas base in Salt Lake City began prospecting. Silver and lead followed, and by the eighteen seventies Bingham Canyon was a raucous mining camp of several thousand people, with saloons and boarding houses serving immigrants from Cornwall, Wales, Greece, Italy, Japan, Finland, and China.

The big transformation came in the early nineteen hundreds, when engineers from Guggenheim's Utah Copper Company recognized that the low-grade porphyry copper ore covering the canyon walls could be profitably extracted by open-pit methods, a new industrial technique. Large-scale open-pit mining began by nineteen oh six. What had been a series of underground shafts became a systematic terraced pit, growing outward and downward year by year. By the mid-twentieth century Bingham Canyon had become the world's largest producer of copper and had supplied enormous quantities of metal for two world wars.

The mine still operates today, now owned by Rio Tinto. It has produced more copper than any other mine in history, over nineteen million tons. It has also produced gold, silver, molybdenum, and, less discussed, more than seven billion tons of waste rock that fills the adjacent valley. The hole keeps getting larger. The mountain is long gone.