Eternal Flame Falls

The Eternal Flame Falls is a small waterfall located in the Shale Creek Preserve, a section of Chestnut Ridge Park in Western New York. A small grotto at the waterfall's base emits natural gas, which can be lit to produce a small flame. 

 This flame is visible nearly year round, although it can be extinguished and must occasionally be re-lit. The Eternal Flame Falls were featured in the book Secret Places by Bruce Kershner.

The researchers also noted the presence of numerous other 'micro seeps' in the area of the falls. By comparing the gas emitted by these seeps with gas from wells in the area, they determined that the gasses originate from Rhinestreet Shale approximately 400 meters (1,300 ft) below the surface. Tectonic activity likely opened faults in the shale, allowing the gas to reach the surface.

Typically, shale must be hot (around 100 °C [212 °F]) for its carbon structures to break down and form smaller natural gas molecules. However, the shale from which Eternal Flame Falls draws its gas is much cooler, in addition to being younger and shallower than typical gas-bearing shale.  

Sources : Wikipedia & Google Images