The Underground Fires That Can Burn for Thousands of Years
Mount Wingen in New South Wales, Australia is commonly known as Burning Mountain, partly for the red regolith that colors its summit, but primarily because an actual fire smolders one hundred feet below its surface, and has done so for at least 6,000 years! This is the oldest-known natural coal fire.
There are a couple good reasons why – for decades – humans have harvested coal to generate energy: it's copious and quite combustible. Over millions of years, simmering heat and crushing pressures transformed dead plant matter into this sedimentary rock, which is composed of carbon and smaller amounts of hydrogen, sulfur, oxygen, and nitrogen. It sometimes only takes a little heat to roil coal into flaming life. Just as this is true when grilling on a summer's day, so is it true within the Earth.
An underground coal bed can ignite from a lightning strike, wildfire, or a mere jostling of the topsoil, enough to permit a slight, but steady stream of oxygen to reach the rocky fuel below. Oxgyen is a highly reactive element, and will oxidize the coal, pilfering electrons and spurring a release of heat. When a fire starts, it can endure for a very long time.
Scientists have unearthed remnants of coal fires that burned millions of years ago, so they've been occurring naturally for some time. Humans, however, have set alight a lot more in a comparatively short timespan. Why? Mining. Explosions, digging, and drilling at mines set numerous coal fires each year, so much so that in 2010, it was estimated that coal fires accounted for as much as 3% of global carbon emissions.
One of the most notable, manmade coal fires has been burning in Centralia, Pennsylvania since 1962. A fire at a landfill in the borough of roughly 1,500 residents somehow triggered a blaze in the coal beds present in the abandoned mines hundreds of feet below the surface. It has since spread over a wide area, opening sinkholes, creating fissures, and causing ominous smoke to rise from the ground in several locations. Centralia was gradually abandoned over the ensuing decades, essentially turning into the coal industry's 'Chernobyl' as the fires still smolder and spread seemingly unabated. They may last for hundreds of years.