This is Horsetail Fall. On most days, it is a beautiful waterfall in Yosemite Valley. But once a year, if the sky is clear and the snowmelt abundant enough to pour water down the cliff, it lights up like a stream of fiery lava.
The New York Times reports that photographers have been chasing the elusive firefall since 1973:
The photographer and mountain climber Galen Rowell was driving through the park after a winter climb when he spotted the light catching in Horsetail Fall. He rushed across the valley and took what is believed to be the first image of the illuminated waterfall. …
For decades, photographers showed up here in winter, hoping to catch the same trick of light but never sure when it might occur. Then in 2009, Michael Frye, author of “The Photographer’s Guide to Yosemite,” used video from four Yosemite webcams to determine the optimal window for the firefall, which he now pegs from Feb. 16-23.
And so photographers trek to the park in that brief window to catch the red, streaming falls, with beautiful results:
Recipe for a Perfect Photo: Clear Sky, Sunset and Water, The New York Times.