Eternal Flame Falls, Waterfall in Chestnut Ridge Park, United States.

Eternal Flame Falls is a waterfall in Orchard Park, New York, that flows roughly nine meters (30 feet) down over dark shale rocks. The water divides into two sections, and at the base sits a small grotto where natural gas emerges from the rock.

The shale layers formed roughly 370 million years ago during the Late Devonian period, when organic material under pressure created gas. The gas continues to seep through cracks in the rock to the surface, feeding the flame behind the waterfall.

The name of this place refers to the persistent fire that visitors can see behind the falling water throughout the year. Hikers often carry lighters or matches to relight the flame when it goes out.

The path to the rock formation covers roughly 800 meters (half a mile) through the forest and ends with a steep staircase leading down to the creek. Sturdy footwear is advisable, as the route can be wet or muddy depending on the season.

The gas that feeds the flame emerges at the surface in few places on Earth as directly as it does here. Scientists from a university in Indiana studied the phenomenon to better understand the geological conditions.