Thousands of migrating snow geese have died in Butte after they made contact with toxic runoff from a former mine, officials have confirmed: This was no ordinary pond, however. It was the 700-acre Berkeley Pit, a former mine now submerged in water as acidic as distilled vinegar. From 1955 until operations ceased in 1982, miners extracted nearly 300 million tons of copper ore from the pit. They left behind an immense crevasse, which filled with water 900 feet deep.

Concentrated within the floodwater are arsenic, cadmium, cobalt, copper, iron, zinc and other inorganic compounds. After it was abandoned, the pit became a federally managed Superfund site. It also became a tourist destination, where visitors observe the mine’s toxic, reddish water for an admission fee of $2. And microorganisms able to survive in the pit became an object of scientific study. READ MORE