Some for centuries...
Boing :
It's a massive underground coal fire that's been smoldering beneath the town of Centralia, Pennsylvania ever since 1962:
The town sits on top of a rich vein of coal, and the fire has defied every attempt to extinguish it. National awareness of Centralia's unending environmental catastrophe came in 1981 when a 12-year-old boy fell into a 150-foot hole that suddenly appeared in his back yard. Most residents were relocated in 1984, and in 1992 the entire town was condemned. Most buildings were torn down, creating the Centralia that can still be seen today: a network of streets running through empty fields and, increasingly, new growth forest. As of 2007, Centralia had nine residents.
Then Dylan told me about a similar, and even more dramatic, subterranean fire that's been burning for almost as long under the Karakum desert of Turkmenistan (pictured above). Locals call it the "Gates of Hell":
The hole is the outcome not of nature but of an industrial accident. In 1971 a Soviet drilling rig accidentally punched into a massive underground natural gas cavern, causing the ground to collapse and the entire drilling rig to fall in. Having punctured a pocket of gas, poisonous fumes began leaking from the hole at an alarming rate. To head off a potential environmental catastrophe, the Soviets set the hole alight. The crater hasn't stopped burning since.
Turns out, these sorts of mine fires can stay lit for a very long time. One burned in the city of Zwickau, Germany from 1476 to 1860. Another coal fire in Germany, at a place called Brennender Berg (Burning Mountain), has been smoking continually since 1688!
Read more VIA - Joshua a freelance science journalist Boing Boing.