Here on New Zealand"s rugged South Island, the waters of Lake Tekapo display such striking electric-blue colors because of glacial silt flowing into the lake, carried by the braided Godley and Macauley Rivers, seen at the bottom of our image. These rivers are themselves fed by the melted waters of glaciers in the nearby Southern Alps. As these active glaciers slowly bulldoze the mountainsides, they pulverize rocks along valley floors and walls. All that grinding eventually produces a fine-grained powder of silt, sometimes called glacial flour. Meltwater picks up the silt, carrying it downstream and into lakes like Tekapo. The particles are so light and fine, they"re slow to sink to the bottom, remaining suspended in the water column instead.
© Sophie Dover/Getty Images
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