If you watch the first few shots of this video with the sound off, you might be forgiven for thinking it was about volcanoes. It certainly looks like a thin trail of lava cascading off the side of a cliff. But the reality is almost more awesome. If you're in the right place on a perfectly clear day in February, at just the right time of evening—and if the snow melt has been active enough—you can watch the water flowing over Yosemite National Park's Horsetail Falls turn bright orange-red.
Fascinatingly, this phenomenon bears a coincidental resemblance to a man-made Yosemite attraction that happened every summer between 1872 and 1968. Unlike the Horsetail Falls, the Yosemite Firefall really was fire—embers from a bonfire pushed over the side of a cliff to create a glowing cascade. I wondered, watching this video, whether the Firefall had been inspired by the natural "Firefall" at Horsetail Falls. Surprisingly, that doesn't seem to be the case. Instead, the Firefall started when guests at a privately owned lodge began paying the lodge-owner's sons to get their father to push embers from the family's outdoor fire over the cliff at the end of the night.
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.