Coal seam fires can burn for a long, long time, if there's enough coal there to fuel it. One of the longest-burning coal seam fires is at Burning Mountain in New South Wales, Australia. It has been burning, very slowly, for at least 6,000 years, reported ABC Science. Another long-burning coal fire is in Centralia, Penn., where the coal has been smoldering since 1962. Here, the Morwell fire starts to lose steam around March 3.