Moment of Science: “Mountain of Seven Colors” dazzles in Peruvian Andes

High in the Andes Mountains lies one of the most colorful geological features you’ll ever see. This week, we’re taking you to the Montaña de Siete Colores, or the Mountain of Seven Colors.

As with most aptly-named features, the striking hues of this mountain, dubbed “Vinicunca,” stand out immediately, with marine sediments being chiefly responsible.

Over millions of years, different materials were deposited and stacked on top of one another as ocean waters churned above, and those stratified layers were thrust upward to form mountains as the South American and Nazca tectonic plates converged.

Going color by color, iron oxide is the key to unlock those vivid reds in clays and other rocks, just like metallic rust. The white comes from calcium carbonate, the same stuff that leads to white-sand tropical beaches, often from broken-down sandstone and quartz and other organic material. Yellow adds some sulfurous minerals into that calcium carbonate mix.

Green comes from a magnesium and iron mixture in a metamorphic rock called “phyllite” and brown rounds it all out with “fanglomerates,” the result of mountain streams slowing down and dropping off all the material it picked up on the way down.

You’ve probably picked up that erosion is a big player here, with the layers gradually worn away by wind and water through the years and millennia and epochs. Those colors really come out after a rainstorm, with the exposed bits eventually oxidizing and revealing more of the rock, though a dry mountainside is still mighty impressive.

As with many natural features, however, the balance of protection and tourism is a delicate one. Vinicunca was mostly ice-covered until the mid-2010s, and often cloud-covered as the peak lies some 16,000+ feet above sea level. Spending only the last decade or so hosting visitors has led to quick-built trails carving every which way, and faster degradation through trampling, erosion, and other mass movements.

Still, if you ever find yourself near Cusco, Peru, it might be worth the trek a couple hours out of town to, as our National Park Service once put it, “take only pictures, and leave only footprints”... as few as possible, if you can help it.

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