Courtesy of Jessica Ball at Magma Cum Laude:
That’s right – it’s under a waterfall! The flame is sheltered just enough that it doesn’t go out very often (although it’s always a good idea to bring a lighter along if you’re going to visit). Gas wells in this area are generally drilled into the Medina Group (a collection of sandsones and shales, which you can see exposed in the base of Niagara Falls to the north), but the seep itself is in the Hanover Shale, which apparently also has a bit of gas in it.
There’s much more to that post, including some more lovely photographs, so do make sure you go. And, incidentally, who wants to take a road trip with me?