Here you see clear, blue ice – “skaters’ ice” – forming on the WoodenBoat School’s lily pond yesterday. Watching ice form day by day in ponds and streams is a little more interesting than watching paint dry.
For example, there is the fact that ice can float. Most liquid substances get heavier as they change into solids. Yet, if I correctly understand the process, water molecules get lighter by spreading out (becoming less dense) as water freezes. If this didn’t happen in our ponds and lakes, the water would freeze from the bottom up, not the top down, and ponds and lakes could become solid, which would not be good for fish and other living things.
In our faster-moving streams, generally, the running water apparently gets colder by mixing with itself and the cold air, which leads to the formation of ice, including a form of early ice called frazil. Frazil ice is made of small, randomly-shaped ice crystals that easily stick to each other, to the edges of streams and rocks, and to other objects within the water:
If the temperatures remain low, the frazil ice (and perhaps other ices) will grow out and eventually could form an ice tunnel that encases the stream. (Images taken in Brooklin, Maine, on December 26, 2022.)