The Eternal Flame Falls is a small waterfall which is located in the Shale Creek Preserve, a part of the Chestnut Ridge Park in Western region of New York. There is a small grotto at the base of the waterfall emitting natural gas, which could be lit for producing a small flame. This flame is reportedly visible all the year round, even if it can be extinguished and occasionally re-lit.
These Eternal Flame Falls were first featured in a book called Secret Places by Bruce Kershner. It was considered an "obscure" attraction in the region, but with the recent media attention and improvements for an access, there are now increased number of visitors.
Source of gas:
According to Geologists from Indiana University Bloomington as well as Italy's National Institute of Geophysics and Volcanology who had studied Eternal Flame Falls in 2013 it enabled a better understanding as to how natural gas which is emitted from naturally occurring hydrocarbon seeps contributes to greenhouse gases in the earth's atmosphere. They discovered that the 'macro seep' at these Eternal Flame Falls had greater concentrations of ethane and propane and approximately close to one kilogram of methane per day.
The gasses were found to originate from the Rhinestreet Shale, located approximately 400 meters (1,300 ft) below this surface. Tectonic activity is believed to have opened the faults in the shale, which allowed the gas to reach the surface.