Turquoise Ice

Today was another winter walk in the tundra that is Minnesota in January. It happened to be the frozen falls at Minnehaha today. There is still a single stream coming over the top that trickles down the slope of what becomes a mammoth cauliflower iceberg over the course of our fierce winters. I have seen it year after year.

However this year I am taking notice of the particular shade of the ice mounds. I have seen an earlier article about the incredible Turquoise Ice Shards at Lake Baikal in the Siberian glacial area of Russia. There, because of the pureness of the water, the depth of the lake and the wild winds that whip into their season - it creates dams of literal turquoise blocks that are more gemlike than liquid. It was formed as a rift valley where the underlying plates of the Amurian and North China faults shifted and pulled away from each other leaving a huge chasm. It continues to shift to the point of adding a 1/2 inch to the Lake each year. It is also home to huge biodiversity because of hydrothermal vents at its bottom which release heat from the earth's core and high levels of oxygen. Because of this purity, the water freezes into a unique blue shade. These shards of ice are called "hummocks."

 

So I know our Minnesota rivers are not nearly as pure and perfect. But I was asking the question of how we are also able to see those beautiful shades of lavender, seafoam and aquamarine? The answer was easy to a scientist, but somewhat lost on me and my understanding of light rays and the spectrum of color absorption! In simple terms; Water, like other matter absorbs light and the color reflected back is perceived by our eyes to be a shade of blue. Somehow in the process of freezing into both snow and ice, the water becomes fragmented (as in a snowflake) and scatters back light to us which then appears in shades of white rather than the absorbed blue. Even in smooth ice cube trays, there are enough bubbles that it no longer reads to us as blue anymore. BUT, as ice becomes thicker and more dense, it obviously becomes heavy as well. As the pressure squeezes out those imperfections, it allows the light transmissions to begin again, and thus starts to show those magical shades of blue.

This is what are noticed on Lake Baikal and any large glaciers that you see in the polar caps. We are just given a very rare glimpse of these tones in the gift of a frozen waterfall here in Minnesota. And now you know more.