Centralia, Pa. is a pretty famous place — mostly because it's been on fire continuously since 1962. But even if you've read about it before, do you know the science behind its slow (and steady) inferno?
The latest video in the American Chemical Society's Reactions series explains why coal mines have a tendency to burn (and burn, and burn some more) in a way that's very different from fires that destroy towns in the traditional way.
Coal burns slowly and evenly — which makes it great for grilling but not so great when it's fueling a subterranean fire. Once fire makes its way into a coal seam (no one is sure exactly how this happened in Centralia, but it might have been wayward flames from the intentional burning of a landfill) the burn can creep its way through, slowly expanding until it exhausts its carbon fuel source. In Centralia's case, that could take another 250 years or so.
And that's nothing: Coal mine fires happen frequently around the world, especially places that still heavily rely on coal for fuel, such as China. But coal in the ground can also ignite naturally — without humans digging mines and setting them on fire — as coal is exposed to heat and oxygen through tiny fissures in the ground, and one such underground fire in Australia is thought to be at least 6,000 years old (and counting).
Centralia hasn't turned into some molten hellscape because of its underground fire. But all but a handful of its residents have left because burning coal has some nasty side effects: sulfuric fumes, dangerous levels of carbon monoxide, and sinkholes, which form as the coal turns to ash and creates large pockets of space in the ground.
In the 1990s, Pennsylvania invoked eminent domain to persuade Centralian holdouts — ones who hadn't taken an earlier buyout — to vamoose for their own safety. But a 2013 legal battle ended with the last remaining residents getting permission to live out the rest of their lives in the town. Once those residents have passed away, the town will essentially cease to exist — it's actually already had its Zip code revoked by the United States Postal Service.
Apparently that whole “neither snow nor rain nor heat nor gloom of night” thing doesn't extend to 53-year-long subterranean coal fires.