At the top of a mountain in southwest Turkey, the ground spits fire. Known as the Flames of Chimaera, they have burned for millenniums.

Local myth long held that these fires were the breath of a monster — part goat, part snake, part lion. Today we know the fuel for this flaming mountaintop is gas escaping from deep within the earth. But it doesn’t come from the decay of ancient plant, algae or animal life, like fossil fuels. Instead, this gas comes from a chemical reaction inside rocks. And a series of studies published by a group of international scientists known as the Deep Carbon Observatory is showing that this source of gas is more common on our planet than previously known.

“We have discovered these unusual types of methane in many, many sites. It’s not a rare phenomenon,” said Giuseppe Etiope, a member of the group who helped discover the cause of the flames of Chimaera in 2014.

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Over the past decade, the observatory’s community of scientists has found hundreds of gas deposits in more than 20 countries and several spots at the bottom of the sea that are similar to the Flames of Chimaera. And they’ve learned that the recipe for these gas emissions is far more complex than previously thought.