Coal is a readily combustible rock of carbon and hydrocarbons that is found all across the United States. Due to its combustive properties and relative abundance, burning coal has been and still is a substantial fraction of the US energy market. However, also due its combustive properties, coal veins and mines tend to, well, catch fire. Lewis and Clark reported seeing burning veins of coal in 1805 when they were exploring the Missouri River in what is now central North Dakota. Maybe you have heard of the still burning mine fire in Centralia, Pennsylvania where a strip mine has been burning since 1962 and could continue to burn for over 250 years. Abandoned coal mines that catch fire are serious health, safety, and environmental hazards that the US government has been trying to address for decades.