Listen to part of a lecture in an earth science class.
The professor is discussing an area of the United States called the Copper Basin.
Now, you may not have heard of the Copper Basin. It's in the Eastern United States, in the Tennessee River Valley.
It got its name because settlers discovered copper there in 1843.
And soon afterwards, it supported one of the largest metal mining operations in America.
At one time, four mining companies employed 2500 workers in the Copper Basin.
For that time period, it was a huge operation.
Well, this mining operation turned the Copper Basin into a desert.
In the 1840s, when mining operations started, it was a dense green forest.
But in the 1940s, 100 years later, it was as barren as the moon.
Efforts to reclaim the land and restore the basin to the fertile valley it once was...well, actually, those efforts are still ongoing.
It's been a long and tedious process.
In fact, it was many years before any results were seen.
Copper mining had gone on there for more than 90 years! The damage couldn't be reversed overnight.
Although I should mention that by 1996, the water in one of the rivers flowing through the basin was clean enough that it was the site of the Olympic white water kayaking competition.
And that river is still used now for recreation.
But...anyway...let's analyze the problem.
It wasn't the mining itself that caused such massive destruction.
It was what happened after the copper ore was extracted from the mines. It was a process called heap roasting.
Copper ore contains sulfur. And heap roasting was a way to burn away the sulfur in the copper, so they'd be left with something closer to pure copper.
Well, in the process, large vats of raw copper ore are burned slowly, for two or three months actually, to lower the sulfur content.