Yosemite’s 740-meter-high Horsetail Falls glow fiery red for a couple of weeks each year in February. It’s not lava, but a play of light that happens at sunset. The warm sunlight strikes the falls in such a peculiar trajectory that it colors them red. For the phenomenon to occur, there must be favorable weather conditions: there must be no clouds or mist to admire them and above all a mild climate is necessary, otherwise the falls could freeze.
