Underground Fires - The Fire Below
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Underground Fires

Earth Burns Below Our Feet

(Published in The EarthSphere Blog. Cover image: Fire Below by WM House; ArcheanArt)

Several years ago, I traveled to the Four Corners region of the Southwestern USA to participate in a geological field trip. We broke from our schedule one hot August afternoon to hike into the middle of nowhere and view an oddity. Perched on the side of a scrubby rock-strewn hill was a blacked hole with heat and the occasional wisp of smoke pouring out. The trip leaders stopped our group about 20 feet from the hole and explained that from there forward, the temperatures below the ground exceeded 1,000 degrees F. If the ground surface gave way, we would be dead before we had a chance to scream. The fire had been burning for decades.

Coal burns, and when coal seams catch on fire, the burn eventually moves underground, where it smolders in a low oxygen environment and follows the coals seam deeper into the earth. These types of underground fires are not necessarily a result of human activity, and they often form by natural means. Surface wildfires and lightning strikes can ignite the initial fire.

The Australian Burning Mountain Nature Reserve, located several hours north of Sydney, contains an underground fire smoldering some 30 meters below the surface. The burn zone is estimated to be about 10 meters in diameter, with temperatures reaching 1,832 Fahrenheit. Burning Mountain’s formal name is Mount Wingen, and the mountain has been on fire for over 6,000 years.

No one knows how Burning Mountain initially caught on fire, but natural causes are the most likely culprit. However, people can also be the instigators of these underground fires.

Burning Coal Seams

The town of Centralia, Pennsylvania, began a descent into hell about 60 years ago when a coal seam beneath the town caught fire. The fire initially started when the city tried to clean up a garbage dump by burning it over. But the fire escaped underground into abandoned coal mines. From 1962 to 1980, state and federal agencies tried in vain to put the fire out, but finally they gave up and started relocating the town’s residents.

As this underground fire burns, holes open up in the earth’s surface, letting poisonous gases vent into the atmosphere. Hellish fire pits gobble up trees, roads, and houses. The Centralia fires have burned for 58 years and could continue burning for another 250 years before consuming all of the local coal.

The Centralia experience is not unique. Around the globe, thousands of these hidden, underground fires burn out of control. The basic chemistry behind underground fires is densely packed, flammable organic material that ignites at the surface and then creeps underground, where a low oxygen environment lets the fire smolder and simmer for decades or even centuries. In places like Burning Mountain, heat from the fire causes the rocks above to crack and form chimneys for exhaust fumes to escape and fresh oxygen to enter and keep the fire burning.

Regardless of whether natural or human causes started the fire, the escaping exhaust fumes deliver a constant stream of greenhouse gases to the atmosphere, and the fires have proven almost impossible to extinguish.

The Zombie Fires of Siberia

The basic physics and chemistry behind coal fires also apply to zombie fires. Instead of coal, the zombie fires burn peat. Peat is normally associated with bogs and wetlands. In the northern latitudes, peat deposits develop under cool, damp conditions where bacterial decay is inhibited, leaving the soil rich with organic carbon.

But when peat or other organic-rich soils dry out, the preserved carbon can ignite and burn. Wet peatlands within boreal forests are usually natural fire breaks. However, when the peatlands dry out, they become zones of fire propagation, not fire breaks.

Over the past several years, record high temperatures in Siberia have dried out the forests, forest soils, and peat bogs of the region, resulting in massive wildfires. If conditions are dry enough, then highly organic soils below a wildfire will also start to burn, and the fire can make its way underground and maintain a long, slow burn. These Siberian underground fires smolder throughout the winter, and when warm weather returns the fire resurfaces, seemingly rising from the dead, to start new wildfires.

As global temperatures rise, the peatlands around the edge of the Arctic are drying out and increasingly exposed to wildfires and associated zombie fires. The ability of coal and peat to smolder below ground for decades or even centuries will generate a new wave of environmental problems for the Arctic. The Siberian carbon bomb is ticking, and zombie underground fires will only hasten its massive release of greenhouse gases.

Related Reads:

Wildfires And Zombie Fires (by WM House; ArcheanWeb)

A Rise in Greenhouse Gases Beyond Our Control — The Siberian Carbon Bomb (by WM House; Medium)

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This Mysterious Fire in Australia Has Been Burning For at Least 6,000 Years(by Fiona MacDonald; Science Alert)

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.