what did the russians do to make this?
BTW there is a coal fire in Centralia Pennsylvania that has been burning underground for over 50 years I think.
There is no way to put it out except to trench out and extinguish every sinlge thing
A tire fire is another example- it creates its own oxygen and so you can’t put it out very easily
“The fiery pit was the result of a simple miscalculation by Soviet scientists in 1971 after their boring equipment suddenly drilled through into an underground cavern and a deep sinkhole formed. Fearing that the crater would emit poisonous gases, the scientists took the decision to set it alight, thinking that the gas would burn out quickly and this would cause the flames to go out”
From Wikipedia:
The site was identified by Soviet scientists in 1971. It was thought to be a substantial oil field site. The scientists set up a drilling rig and camp nearby, and started drilling operations to assess the quantity of gas reserve available at the site. As the Soviets were pleased with the success of finding the gas resources, they started storing the gas. The ground beneath the drilling rig and camp collapsed into a wide crater and disappeared. No lives were lost in the incident. Large quantities of methane gas were released, however, creating an environmental problem and posing a potential danger to the people of the nearby villages.
Fearing the further release of poisonous gases from the cavern, the scientists decided to burn it off. They thought that it would be safer to burn it than to extract it from underground through expensive methods. At that time, expectations were that the gas would burn out within a few weeks, but has continued to burn more than four decades after it was set on fire.