I’m at a conference today so not as thorough post as usual but no less amazing. As gases rise from the bottom of Abraham lake, Alberta Canada they are trapped by clear ice. The flattened parts of the bubbles show that the ice formed in different places at various times - top down. The bubbles would encounter these layers and spread out, once a new layer of ice forms below, the bubbles form a new flat spot below the first.
Another great example can be seen here.