A vocabulary of landscape — a landscape of words
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watermelon snow
Watermelon snow is old summer snowfield stained pink or red by a green alga that carries a red pigment as a sunscreen. Walking on it leaves pink footprints, and it smells faintly sweet, which is where the name comes from. It grows in the meltwater film between the crystals and reaches enormous densities on high snow in late summer.
Etymology
The English name is for the color and the smell together, and eating it is not advised. The phenomenon has been recorded for a very long time: Aristotle described red snow, and John Ross’s Arctic expedition of 1818 brought back samples of what the London newspapers called crimson snow, which caused a considerable stir before anyone knew what it was.
Notes
The organism spends most of the year as a dormant cell in the snowpack and germinates when meltwater arrives, growing a red carotenoid coat that protects it from ultraviolet at altitude. The red also absorbs sunlight, which warms the surface it sits on, so the alga accelerates the melting of the snowfield it depends on, which is one of the tidier feedback loops in nature.