This underground fire has been burning for 6000 years.

In Australia, there is a national park called the Burning Mountain Nature Reserve (Burning Mountain Nature Reserve), four hours' drive from Sydney to the north. As the name says, underground here, a fire is burning and has been burning for thousands of years.

The real name of "Burning Mountain" is Mount Wingen, which means "flame" in the local aboriginal language. If you come to the park-- which is still open to tourists-- you won't see the flames, but you can feel the signs of burning everywhere: the surface is orange with white sinter, yellow sulfate and red iron oxides; the air smells of smoke and sulfur; touch, the ground is hot. In fact, this invisible fire is burning 30 meters below your feet.

This is a kind of "coal seam fire" (coal seam fire), which is formed by the continuous smoldering of underground coal seams. Today, there are thousands of coal seam fires around the world, but Wingen Mountain is by far the longest known to burn. Some researchers estimate that it has been burning for about 6,000 years and is now moving south at a rate of about 1 meter a year.

"No one can tell exactly how big the fire under Flame Mountain has been, you can only speculate." Professor Guillermo Rein of Imperial University of Technology, who came here in 2014, wrote in his travels that although you can't directly see the location of the coal seam fire, you can still find the track of the fire, such as where the newly burned areas are covered with white ash and no plants grow.

"you can see the beautiful eucalyptus forest where the fire hasn't hit yet. However, once the fire in the ground comes through, there will never be any plants alive, not even weeds. " "and when the fire is over, 20 to 30 years later, the forest will grow back," Ryan said. But the flora of the forest has changed-the fire has shaped the vegetation. "

The real Silent Hill

The danger of coal seam fires is that once ignited, such fires are difficult to put out until they spread throughout the coal seam. Although the coal seam fire in Wengen Mountain has been burning for a long time, thanks to the fact that it is far away from residential areas, it does not pose much direct threat to nearby residents. But Centralia, Pennsylvania, is not so lucky.

The town of Centralia, a bustling town of thousands of people, is famous for producing anthracite, but its rich coal resources have repeatedly banned illegal mining activities. Records show that in May 1962, five employees of the fire company were invited to the town to clean up the garbage, which is located next to an abandoned open pit. As usual, the five employees put out the flames after burning the rubbish for a period of time.

What they didn't notice was that the fire from the dump went from the open pit into the crisscross of the underground mine tunnel in the town of Centralia. From that day on, fires broke out frequently in the town. At first, frequent fires did not attract enough attention from the government. However, residents gradually found that the ground began to collapse, and even some residents were nearly swallowed up, and there was a distinct smell of sulfur in the cracks in the ground. In 1979, gas station owner and then mayor John Coddington inserted a dipstick into an underground storage tank. He wanted to check how much gasoline was left, but was shocked to find that the temperature in the tank was as high as nearly 78 degrees Celsius.

At this time, in the deeper smouldering coal seam, the temperature may have reached 1000 ℃. In the town, in addition to the pungent smell and ground collapse, a large number of residents were taken to hospital because of carbon monoxide poisoning. There was nothing people could do about the underground fire, so they had to abandon their former homes. the town of Centralia was completely abandoned and even became the prototype of the game "Silent Hill" (Silent Hill). Today, the coal seam fire here has been burning for nearly 60 years, but the smoke from the underground coal seam still lingers around the town in Silent Hill.

How to ignite the Coal seam Fire

It should be noted that the garbage disposal accident is just one of many speculations about the cause of the coal seam fire in the town of Centralia. As for the fire in Mount Wingen, which has lasted for thousands of years, we are not sure how it started in the first place.

The first record of a coal seam fire in Wingen Mountain was in 1828, when a local farm worker said he had discovered a volcano here. Just a year later, in 1829, geologist Reverend Wilton discovered that the so-called "volcano" was actually coal seam fire. Subsequent measurements show that the fire has moved about 6.5 kilometers, and at the current speed of about one meter a year, it has been burning for at least 6,000 years.

In the local culture, Mount Wingen is a sacred land. According to legend, a brave soldier was caught by the "Evil One" at the bottom of the mountain and lit the whole mountain with a torch. Of course, this is just a legend, which is more likely to be of natural origin than the coalbed fire ignited by human activity in the town of Centralia.

"of course we can't completely rule out human activity (which started the fire), but it's more likely to be caused by natural factors." Ryan explained, "it is possible that the wildfire caused by lightning ignited the exposed coal seam somewhere, or the coal seam 'spontaneous combustion'."

When the coal seam is in a shallow position, it can be exposed to enough oxygen. If it happens to encounter high temperature and plenty of sunshine, the outermost coal will absorb heat and heat up quickly, causing "spontaneous combustion". The study shows that the temperature required for spontaneous combustion of coal with different grades (the content of useful components or minerals in ore) is different, with a maximum of 140 ℃ and a minimum of 35 ℃.

What worries Ryan even more is that with global warming, there may be more coal seam "spontaneous combustion" phenomenon. In turn, coal seam fires will also release a large amount of greenhouse gases, further exacerbating climate change.

These burning coals will not only release greenhouse gases such as carbon dioxide and methane, but also release harmful substances such as carbon monoxide, nitrogen oxides and mercury. At the same time, the raging fire is also engulfing precious fossil energy.

How long will the burning mountain burn?

No one knows how long the coalbed fire at the bottom of Wingen Mountain will burn. We do not know how far the coal seam extends here, nor where it extends. For now at least, the fire here will continue to burn.

"without human interference, this place can burn for thousands of years. The high temperature of the flame will cause the surface to expand and crack, and more oxygen will enter the ground along the cracks to supply the burning of the coal seam fire. " Ryan sighed, "Fire creates chimneys and oxygen channels for itself."

Interestingly, when Ryan visited here in 2014, he noticed that about 20 meters in front of the fire was a small river. Maybe in the next ten years, we can look forward to the change of this fire. "Coal seam fires may break through the surface, bringing obvious flames and higher temperatures, just as they did in 1828 when it was mistaken for a volcano."

"or if the coal seam extends deep, it may go out naturally. It would also be amazing if we could see the fire that had been burning for thousands of years extinguished in our lifetime. "