On account of the recent cold spell, I went up the hill behind us in search of a glazed-over pond. Ponds can have interesting freezing patterns and, if the ice is thick enough, a little excitement. I've never seen these ponds freeze, but then again, I've never thought it likely enough to warrant a visit in winter. The first two ponds I visited (technically, man-made reservoirs for flooding the rice fields) had ice only over a small section at one end. I had better luck with with a drained pond. This 'pond' looked more like a dirty mud pit, but I saw evidence of ice on one side. So, ignoring the warning signs (more on that later), I walked down and around to the icy end. From eye-level, and even from a crouch, this ice looked like snow.

But except for the holes that exposed the dirt underneath and the twiggy matter on top, the surface was smooth and level, like that of a glazed pond or puddle.  Indeed, a partially glazed-over pond is probably what it had been. The whiteness was due to some fuzzy growth underneath that I could see in the large gaps (see the image below).

Though I couldn't discern the type of growth by eye, my camera revealed it to be hoar frost. The image below shows that some of the hoar crystals were fairly large.

The bottom-right inset of the above image shows that one can see through the clear surface glaze to the white hoar underneath. When I broke off a small piece and flipped it over, I saw that some of the hoar consisted of aligned plates in the plane of the surface glaze.

Slightly uphill from the hoar, the white hoar glaze vanished, revealing only frozen soil. The soil was a little porous, with numerous small holes. Amongst the small holes were larger ones.

The larger holes looked like animal tracks, but it seemed odd for tracks to go so deep at only the toe and pad depressions, so I wasn't sure they were tracks. But nearby, I saw two unmistakable prints, pointing in the opposite direction.

How could such deep prints form? And why were there only two in this spot? I often see puzzling formations in frozen ground, particularly ground with some open water. On my earliest icespotting outings a few years ago, I would puzzle over glazed puddles that seemed to drain suddenly overnight yet still have water for new glaze on the following nights. I found the likely culprit in the library - in an article in Nature from the 70s. In the article, the author, who lived just a bit north of me, reported on how water would drain from puddles overnight, only to reappear during the day. He suggested that the water would flow underground, and uphill to the base of ice columns that pushed up from the soil. I noticed that my drained-overnight puddles would usually lie between such soil ice-columns, but during the day, the ice columns would melt and the puddles refill with water, despite a lack of rain. In my mud-pond, some soil-ice columns were not far from the snow-frost and pawprints.

So I think the author hit on an important, widespread process. It doesn't completely explain the snow-frost and oddly deep pawprints, but it might be a good start.

While I  explored some other icy things on the mud-pond, I ventured out to the middle. Suddenly, the glaze over the mud gave way, leaving me knee-deep in  grey clayish muck. I eased my way back on top of the glaze and gingerly went back to the edge, leaving my own two strange 'pawprints' in the middle. Thinking of the warning signs, I felt a little silly. But still, I'm glad I checked the place out.

- JN