Pristine snow on our mountain peaks is ideally always white, but thanks to climate and other factors in this wild world, sometimes we get patches of snow on our slopes that are brown, or even red. Ever wondered how a layer in the middle of the snowpack got its sandy color, or what the pink pockets of snow you find in spring and summer are? 

This past winter in particular saw a significant layer of sandy brown snow in our snowpack. Skiing in Horseshoe Bowl in early spring, I noticed that the snow wasn’t exactly white. These layers of dirty snow occur when wind transports sand and dust from other parts of the West, like southern Utah and other parts of the Colorado Plateau. When areas of the West get dried out or remain uncovered with snow, even in winter, the wind, rather than transporting snow, transports tiny specks of earth that have become so parched that they can’t remain as homogenous parts of the soil. Drought across the Colorado River Basin only exacerbates this problem as the West becomes more arid. 

When these layers of dirty snow occur in our snowpack, they cause the snow to melt much more quickly. Rather than remaining solid white and reflecting back all of the UV rays, the snow absorbs some of the rays thanks to the darker particles on the snow surface. That added heat absorption makes the snow affected by this dust layer melt more rapidly. There was about a week-long period at the end of March and early April of this year when warm temperatures combined with that nasty layer of dirty snow collaborated in a vicious melt cycle. That compounded warming made the snow soggy, even at elevations above 12,000 feet. Of course, snow can still melt quickly even without these dark particles on the surface, but the particles certainly cause our seasonal snowpack to disappear much faster. 

There’s more than dust, sand and dirt particles that you’ll find up high in the Alpine, especially as we transition to summer’s warmer temperatures. It’s not uncommon to find small patches of pink or red snow, especially in late spring and summer. The pink snow, or “watermelon snow” as it’s often called, is actually a type of algae. Chlamydomonas nivalis likes to grow in cool but not quite freezing temps and is found in melting snow in the High Country. Recent studies indicate that wind may play a part in algae growth too, especially in the intermountain west. Algae needs some sort of nutrient to grow and flourish, and it’s not getting that from the snow itself. Some of the nutrients that support the algae growth may come from rocks under the snow surface. But other nutrients, nitrogen in particular, may be carried in with the wind, and at least in part come from fertilizers used in other parts of the West.  

This watermelon snow may look like a tasty treat, but it’s not great to consume and can cause digestive issues in humans. The red snow will eventually melt and end up in our watershed. Chlamydomonas nivalis can linger in temperatures up to the low 80s, meaning it will remain in the water once the snow melts, potentially causing other issues in the water supply for both humans and wild animals. Either way, whether the snow is a rusty brown from dust or bright red from algal blooms, like yellow snow, you can appreciate the colors, but it’s not good to eat it. 

Stasia Stockwell is a Breckenridge local and avid backcountry skier. A true mountain dweller, she feels most at home in the Alpine. She writes primarily for the outdoor adventure realm, with the desire to connect readers from all backgrounds with nature in a meaningful way