A creature out of Deep Space Nine? Alien roadways? Actually these are local pictures I took in the Marsh Lake area Yukon, of structures in lake ice last spring. A rare combination of crystal clear ice, a shallow, and variably coloured lake bottom, and a bright sunlight reflection set the stage for this unique environment of surreal dimensional ice phenomena.
Ice, by definition is a rock–forming mineral. As amorphous water freezes from the top down in a lake environment; atoms are re-organized more efficiently into a crystalline form. (Ice.)
The jagged ribbon-like 3-D polygonal structures are a result of snow on the surface of a frozen lake gelling to ice during a warming period in the spring. Bubbles of air within these “ribbons” give them a stunning dimensional appearance in sunlight.
So how does one explain these bizarre features! The closest common analogy that most people may relate to are mud cracks, like the desiccation mud cracks that you would see in a thin layer of mud drying up from a puddle on a street. Polygonal patterns form from the shrinkage of silt and clay as the water evaporates out of the mud. In the case of ice, the reverse process occurs. That is, instead of a contraction “cell” as in drying mud, with water freezing to ice, you get an expansion cell.
When you get a thickness of snow on top of lake ice and a good, warm spell as we experienced last spring, the snow melts down to a thin layer of water on top of the lake ice during the day and, if it’s cold enough, will freeze during the night creating these polygonal features. Where these ice expansion cells meet, there may be a phase change to water momentarily because of the local compression force forming these jagged ribbon-like boundaries between the polygons.
As any good ol’ Canadian hockey player knows, gliding over ice is achieved when the pressure, or compressive force from the metal skate blade momentarily causes the atoms to rearrange into a water phase. So the hockey player is actually gliding on a thin layer of water that quickly freezes over again.
Also, air bubbles can be trapped in this water phase boundary before it freezes again, adding a magical silvery dimensional effect, especially when the sun comes out!
The upper thin layer of ice that was once snow cover, not the bottom layer of lake ice, clearly contains these dimensional jagged ribbon-like features.
As a “rock reader,” I have seen a similar feature observed in limestone rocks known as “stylolites.” In rocks, these jagged pressure-solution features are created by litho static compression, or typically the force from the weight of overlying rock stratigraphy and associated fluid movement dissolving material along the stylolite surfaces. Not quite the same, but similar.
I invite you to come to the Yukon Arts Centre and see more of these bizarre and artistic photos at the Last Ice Show, coming to YAC’s community gallery this summer.