Ice Lake – September 18, 2019

Over the last week, we’ve been climbing peaks in the Elk Mountains and San Juan Mountains of Colorado for the Summits, Songs and Science project. Crisp mountain air and spectacular mountain vistas greeted us. Perhaps the most stunning sight of all? The gorgeous “Ice Lake” nearby the town of Silverton, in southern Colorado.

This lake is an out-of-this-world blue color. No filters have been applied to these photos. No dyes have been added to the water. So, what makes this lake such a vibrant blue? Take a look in your pantry for some flour. Feel it between your fingers. It’s really fine material, right? Erosion in the mountains from freeze-thaw processes as well as by glaciers grinding down rocks over thousands of years, can form similar very fine material out in nature, called “rock flour.”

These rock flour particles are so small that they can remain suspended in lake water pretty easily (versus settling out). When sunlight hits the water with these suspended particles, the particles reflect very strongly in the blue wavelength range of the electromagnetic spectrum. The color of a lake can appear different from one day to the next or even from hour to hour, as we witnessed. The intensity or brilliance of the color varies depending on the lighting conditions, meaning, even the most colorful lake is not going to look very spectacular on an extremely gloomy or cloudy day. There needs to be sunlight! The angle of the sunlight hitting the water and the angle of viewing also have an effect on the color. Often you’ll notice how much more vivid a lake looks when viewed from above.

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