This tiny hexagonal snowflake is beautiful with its geometry, but if you look a little closer, you’ll find some elusive clues to how bubbles form inside of a snowflake. This little gem is one I have been searching for, because it tells so very much about snowflake formation!
There are two primary ways that bubbles can form in a snowflake: one, simply put, is that the center part of an outgrowing crystal facet grows slower than the edges, creating a “cavity” inside. If environmental variables change for more rapid growth, this is sealed off into a bubble. This is how I always understood bubbles to form, but there is another way… and this alternative method explains a great deal.
Snowflakes will grow with thinner sections of their plates, often appearing somewhat “wrinkled” with waves of different thickness. We see that just outside of the center here. These areas actually “fill in” as the snowflake grows. Well after the footprint of the snowflake has grown beyond these features, they continue to evolve and grow. With a physics model that I cannot explain on a molecular level, during this internal thickening, bubbles will form just below the surface.
I have an idea how this might happen. If the “valleys” of the thin section of the snowflake increase thickness to the same profile as the rest of the crystal, the outer edge can become more like a canyon wall than a river bed. That near-90-degree angle might change things. If you have a sharp angle, water molecules might be more inclined to attach to that point, and potentially grow out as a “ceiling” over top of the canyon below. This would trap air inside, forming bubbles. Because these bubbles would be very thin and very close to the surface of the snowflake, it could evoke the colours we sometimes see due to thin film optical interference.
And moreover, this can happen multiple times, in “waves” or “layers”! On the left and upper right, just beyond the existing “ceiling” growth, we see bubbles already trapped in the layer of ice underneath it. This “canyon wall” concept could also potentially explain how small speckles of bubbles form, as the majority of a thinner layer would fill in until only a few pockets remain, that get covered over. If you have a keen eye, in the lower left, you can see some bubbles forming in the remaining valleys as they are being filled in.
Shot with a Lumix S1R and the Canon MP-E 65mm F/2.8 1x-5x macro lens, focus stacked and shot entirely handheld. Such moments are fleeting, and when a snowflake like this presents itself I need to act quickly. All images were shot in the span of a minute, and for a subject only 1mm in diameter, there is a treasure trove of discovery. It’s the reason I still head out and photograph snowflakes at every opportunity!
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