When natural gas from deep underground reserves escapes from cracks in the rock, it can spontaneously combust for thousands of years.
The eternal flame behind the waterfall in Chestnut Ridge County Park. Image: World Atlas
According to Giuseppe Etiope, a geologist at the National Institute of Geophysics and Volcanology in Rome, Italy, the eternal fire can be considered a special case of gas leakage from deep underground reserves. Gas leaks occur when naturally occurring underground flammable gases, primarily methane, ethane and propane, move to the surface from pressurized reserves through cracks or holes in rocks. In special cases, when gas reaches the ground with a high enough methane concentration, it can spontaneously combust. Fueled by continuous gas emissions, some fires can burn for thousands of years, hence the name eternal flames, according to National Geographic.
Etiope estimates there are fewer than 50 eternal flames globally, often found near oil wells. They exist in countries including the US, Romania, Italy, Turkey, Iraq, Azerbaijan, Taiwan, China, India and Australia. Some may have evolved over thousands or tens of thousands of years, even a million years ago.
A famous fire lies below a 9.8 m waterfall in Chestnut Ridge District Park in New York. This flame is about 7.6 – 20 cm high, depending on the weather and season. “It shines behind the curtain of falling water,” describes Arndt Schimmelmann, an Earth scientist at Indiana University. Etiope also shared that this is the most beautiful natural eternal flame he has ever seen.
Even though some have burned for millennia, the eternal flame can be extinguished. “The name ‘eternal fire’ is misleading because geological history shows that nothing exists forever on Earth,” Schimmelmann said. Some fires may be extinguished by rainwater, depending on the intensity of the gas leak and ground conditions, after which they may spontaneously re-ignite.
At Chestnut Ridge, splashing water into a small cave can extinguish a fire. “I myself have done that several times when taking gas samples for geochemical analysis. Rekindling the fire without being drenched by water from the waterfall is always a big challenge,” Schimmelmann shared. In fact, this fire may disappear due to natural erosion as the waterfall recedes. Losing the shelter of the cave will cause the fire to go out frequently even if the gas flow is not interrupted.
Geological hydrocarbon leaks, including eternal flames, are sources of natural greenhouse gases such as methane and photochemical pollutants such as ethane and propane. The Chestnut Ridge fire releases about a kilogram of methane per day. There are so few eternal flames that their environmental impact is quite small compared to the thousands of gas leaks globally. Gas drilling can extinguish nearby eternal fires by lowering the pressure of the gas fields that fuel them. The eternal flame in Chestnut Ridge Park exists today because no drilling activity has taken place in that area.