I spent a couple hours inside an eastern Kentucky coal mine and it made a lasting impression. Those deep underground Appalachian coal mines are an extremely dangerous business. There's a thin line between safe and dead when you're that deep in the Earth, especially in an environment that generates explosive gasses.

Couldn't even come close to standing up in the coal seam we were in. Rode in on our backs in a small, low rail car -- four abreast. The mine opening quickly tapered, to where the ceiling was hardly a foot from our faces. The only time I've ever felt claustrophobic.

When the rail ran out we got on a similar transport with wheels. When that ran out we crawled to where the "continuous miner" was digging the coal. While watching it the ceiling over the machine collapsed. Somewhere I have photos. The company VP's face looked rather shocked.

Continuous Miners

A machine with a large rotating steel drum equipped with tungsten carbide teeth that scrape coal from the seam. Operating in a “room and pillar” system – where the mine is divided into a series of 20-to-30 foot “rooms” or work areas cut into the coalbed – it can mine as much as five tons of coal a minute – more than a miner of the 1920s would produce in an entire day. Continuous miners account for about 45% of underground coal production, and also utilize conveyors to transport the removed coal from the seam.