About the reason that the hole is in that particular location, I think a better explanation is that a plane passed through the cloud. These are known as “hole-punch clouds". As to the reason that a plane would produce the ice: the passing of the plane’s wings, body, and (if present) propellors, through the air produce a region in which the air expands. The expansion produces cooling, and the already plenty supercooled droplets are pushed below the homogeneous freezing temperature of -40 C. Hence, some freeze. The frozen ones grow rapidly at the expense of the remaining drops, and fall out. 

Hi Bev,
That is an interesting observation. I can only guess about the angular nature. If there had been fingers such as those in the top images, the melting from the center may proceed along nearly straight fronts between the fingers. For example, in the top image, there are 7 main fingers, so if the melting fronts were straightish between fingers, the shape would be a 7-sided figure. If two fingers are very close, the fronts may join, making it 6-sided.

Just a guess. I may have seen something like this in the past. Will keep my eyes open for it. Thanks for asking–

Jon

I have a roundish pond on which the melting pattern of several days is a definite trapezoid. In a larger of my ponds, the thawing is also angular. Why? It seems that it might follow the shape of the pond…but aside from that, WHY would these thaw in ANGULAR patterns?

I have photographed and video’s an ice vase that I found in an old shower floor that was in the bed of my truck. I had never seen anything like it and this afternoon I had some time indoors so found Your website.

Oh and I too put a small twig down into the vase.

Mine too was triangular.

How do I send you the video and photos?

https://www.reddit.com/r/bprogramming/comments/bky0is/the_sixfold_nature_of_snow/

Looking at this posting, now 7 years after I wrote it, it might look like the plots are from the NY Times article. They aren’t. I spent quite a bit of time making them.

My point was that if one looks at the data, the picture is not as grim as the newspaper articles suggests. Also, note that the snow coverage instead has an increasing trend in the early winter. Also, obviously, the trends in smaller regions may be quite different than those of all of N. America, as I plotted here.

Thanks a lot, Jim.
Prof. Lewin sure has the mad scientist look about him now.

I did not know about the term “cat ice” for the ice on these “crunchy” puddles. The 1901 book excerpt that is briefly shown in that video gives the definition, but does not mention why cat is in the term. Online, the Merriam-Webster dictionary also gives the term “shell ice", and one twitter poster (@RobGMacfarlane) writes that the ice is just thick enough to “support a cat” and hence the term.

About that Prof. Lewin video, if you look to it for an explanation, then you can better use your time elsewhere–you will find no explanation there of any freezing phenomena.

Just thought I should tip you off to the reason for some extra recent traffic – a challenge issued by Professor Lewin, with this page listed as a providing a very good explanation. https://www.youtube.com/watch?v=B1QbNmCPgE0&ab_channel=LecturesbyWalterLewin.Theywillmakeyou%E2%99%A5Physics.

Hi Sarah,
If you have a chance, send a photo of the supraglacial pond case, and I’ll ask Charlie. He might have done some subsequent research on these.
In these cases, it seems very likely that water flow came through the ice at the center and flowed outward slowly. The case at the bottom with the viscous fingering likely involved faster flow.
But like most of these ice-pattern phenomena, close and detailed observations are hard.

Jon

I am wondering if you or your peers have made any progress on the concentric circles on snow covered ponds. I am seeing the same thing on glaicers (small ponds on glaicers) and wondered how these concentric rings form. In the center of the pond (center of all the rings), we also see a small smooth concave-up bulge, like the slush accumulated in a upward facing dimple in the middle. Pressure? Slow upflow from waters below under pressure? Thoughts?

Hi Karel,
About your 1st question:
Does all clear ice (not slush) separate or split as vertical candles or pencils?

I have not seen polycrystalline ice that splits apart like this. Sea ice might, but I have not played around with sea ice. The reason sea ice might do this is that the salt in the water does not enter the ice, and tends to collect in long vertical channels called brine pockets.

About your 2nd question:
Or is there a difference in small grains and large grains?

The grains will depend on the ice history and the way it originally formed. Often, researchers just look at slices of the ice and thus get knowledge only of a cross-section. It would be interesting to know the 3-dimensional structure of the grains.

About your 3rd question:
Most ice formed from freezing has air bubbles. And there can be a lot of stress in the ice around the bubble. So this might lead to grains. I don’t know any more about it though.

(Sorry about the delay in this reply. I was having some trouble with the system.)

Does all clear ice (not slush) sepatate or split as vertical candles or pencils? Or is there a difference in small grains and large grains? And what about air bubbles?

Hi Madison.

Hair ice forms like needle ice in the ground: water from inside flows to the surface and freezes. I tried to explain this above and below the diagram–let me know what aspect of the explanation is unclear.

The reason that the hairs are thinner is thought to be due to the thinner channels of water in the plants.

And the reason the hairs don’t clump into a solid mass, like clumped spaghetti is not clear. Some researchers recently argued that a fungus in the wood keeps the hairs from clumping.

Jon

But why does it happen

Nice to hear, David.

I suppose many have wondered, but only for a minute.

The frozen puddles have other interesting features, and thus more things yet to wonder about. It never ends.

About that last question and mystery in the last photo, I think I now have the solution.

Thank you for answering this puzzle for me! As a kid, I too loved breaking the hollow ice on puddles and always wondered how they formed that way.

Thanks Ray.

I’ve never heard of Zooniverse, but I look forward to checking out your link.

Hi,
I came across similar dendritic patterns on Eskimo Lakes ice whilst browsing Google Maps https://www.google.de/maps/@69.509159,-131.539675,971m/data=!3m1!1e3 and have started a discussion on Zooniverse Planet Four terrains https://www.zooniverse.org/projects/mschwamb/planet-four-terrains/talk/9/192678?comment=329756&page=1 . I would appreciate your comments.

Hi Mark,

If you ever get an image of the Russian and Korean editions, please post!

It is nice to see these other languages and have a reminder that the book is spreading…

Jon

Wow, Dennis, those are fantastic patterns and great photos – thanks for the link!

Many people seem to think that the curvy ice patterns only form on glass. But it only requires a thin film of water. This is why I call it “film frost". In addition to the cases of concrete and plastic shown above, I’ve also seen it on wood. I don’t recall ever seeing it on rock, or if I have, never as startling as the formations you photographed.

Jon