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Mystery Photo

12-5-18 mystery photo2 _U1A2595The icing over of ponds has begun as a result of the recent cold weather. Holes are appearing in the (thin) ice of some ponds.  How do you think these one-to-three-foot holes are formed? Responses may be submitted by going to the Naturally Curious blog site ( and scrolling down to “Comments.”  The answer will be revealed on Friday, 12/7/18.

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41 responses

  1. I saw similar holes on a Rt 14 pond south of Barre and wondered the same thing. I saw some ducks nearby and wondered if it was their work.

    December 5, 2018 at 8:33 am

  2. Jodi Santana


    December 5, 2018 at 8:37 am

  3. Katharine Preston

    Beavers pushing up through the thin ice for air (last chances!) (I learned that from you!)

    December 5, 2018 at 8:58 am

  4. Alice Pratt

    Is there a warmer spring under the ice?

    December 5, 2018 at 9:01 am

  5. Stein

    A gas “burp” from decomposing plant material?
    A spring causing the water there to move and therefore not freeze?

    December 5, 2018 at 9:02 am

  6. nbjaquay


    December 5, 2018 at 9:03 am

  7. Sam

    Seeing as there are no tracks leading to or from the holes, I suspect that the ice has not frozen in those spots yet due to an upwelling of warmer water.

    December 5, 2018 at 9:04 am

  8. Marilyn

    I always thought they were the result of springs in those areas.

    December 5, 2018 at 9:04 am

  9. Walter Harris

    I think they are caused by underwater springs bubbling up to the surface and disrupting the surrounding surface from freezing.

    December 5, 2018 at 9:09 am

  10. I’m going to guess that they’re beaver holes. Great puzzle!

    December 5, 2018 at 9:17 am

  11. Jill Oneglia


    December 5, 2018 at 9:23 am

  12. Clyde Jenne

    Beavers or muskrats.

    December 5, 2018 at 9:31 am

  13. Brooke Beaird

    Relatively warm water from springs?

    December 5, 2018 at 9:39 am

  14. Rocks just below the surface

    December 5, 2018 at 9:44 am

  15. Peter Hollinger


    December 5, 2018 at 9:47 am

  16. Noël K.

    beaver breathing holes?or otter fishing. We often have a pair of otter that pass thru our nearby pond (which also has resident beaver)when it ices up and again at spring break up. They seem to like fishing off the ice.

    December 5, 2018 at 9:52 am

  17. Laura

    We always thought they were caused by the springs that fed our pond. Friday we’ll finally know!

    December 5, 2018 at 10:02 am

  18. Joan

    Perhaps the same pond Katrinkavt refers to on Rt.e 14 in Williamstown, I saw +/- 6 otters on the ice recently, and similar-looking holes in the ice. So I’ll guess otters too.

    December 5, 2018 at 10:18 am

  19. JJ

    Most years, on my pond, it is the otters. I have had many beavers but never seen them poke up through the holes. I’m sure they do, as would the muskrats.

    December 5, 2018 at 10:26 am

  20. Kathryn

    The photographer just before you is now taking pictures of winter’s underwater life?

    December 5, 2018 at 11:14 am

  21. I also suspect beavers.

    December 5, 2018 at 11:15 am

  22. Giant Turkeys running across the ice!

    December 5, 2018 at 11:43 am

  23. peg emerson

    snapping turtle farts

    December 5, 2018 at 12:13 pm

  24. dp

    My daughter and I were debating that very question a few days ago. My theory is that pieces of debris such as a leaf absorb heat and create a thin spot where water can well up as heavy fresh slow pushes the ices down, aided perhaps by the impact of methane bubbles rising from the bottom. Or kids throwing rocks.

    December 5, 2018 at 12:46 pm

  25. Phyl Newbeck

    These are gas holes which are often caused by vegetation below the ice or by springs.

    December 5, 2018 at 1:59 pm

  26. Lee Attix

    Natural springs below the surface cause the holes to form.

    December 5, 2018 at 2:31 pm

  27. Bill on the hill

    Beaver and or muskrats? My pond has (4) natural springs that consistently leave their
    circular shapes in the ice above, I don’t recall them ever leaving holes in the ice however.
    On the other hand, depth of the spring may have a different effect with respect to its upward strength.
    I await with bated breath once again Mary! 🙂

    December 5, 2018 at 4:22 pm

  28. I’ve seen these spider-like patterns a lot over the years. I’ve thought they might be caused by the top part of the ice melting (due to warmer air temperatures) and draining into holes in the ice. Since ice is less dense than water, water tends to sink while ice floats–if there is a way for the water to get below the ice, rather than to sit on top of the ice, it will do so. As the water drains, it will erode/melt channels in the same way that water drains on the land, and the pattern looks just like the pattern of brooks and rivers on a watershed. Even a very small hole would work to start the process—as water flows down through it, it will melt/erode, enlarging the hole.
    I don’t know what would cause the initial tiny holes to form in the first place. Maybe just water sitting atop the ice, and melting itself a hole–perhaps when water pools where there are irregularities in the ice. Since water is denser at 32 F than it is a few degrees above (densest at 39 F, I think) then water cooled by the ice in those pools will tend to rise, while water warmed a few degrees by the air will sink, putting it in contact with the ice.
    Curious to see if that’s close, and the rest of the story. If it is correct, I’m curious to see how it can be explained with fewer words….

    December 5, 2018 at 4:35 pm

    • Karen McCarthy Eger

      Could it start with just some dark bit of debris on top of the ice, sun melting the ice right there as a darker something absorbs the heat?

      December 14, 2018 at 9:14 pm

  29. ann


    December 5, 2018 at 7:20 pm

  30. Birdlady

    Springs coming up through the ice

    December 5, 2018 at 7:57 pm

  31. Is it flooding? More water enters the pond and the ice pulls away at weak areas?

    December 5, 2018 at 9:28 pm

  32. Kathy Schillemat


    December 5, 2018 at 9:41 pm

  33. Sandy Gmur

    I think it is either beavers or river otters:-)

    December 6, 2018 at 2:59 pm

  34. A.f.Brown

    Springs are the only thing you’re going to be seeing this way

    December 6, 2018 at 4:33 pm

  35. Rachel Stern

    Hi Mary,Wondering if you can answer a question.  I saw beaver marks on a stump of a tree, fresh and there was a trail on the wood chips to the pond nearby, and in the distance is an old beaver lodge.  1.  Why is there a trail of wood chips to the water’s edge?2. There was oil nearby the shore and I wondered if it could be from the beaver’s oil glands marking territory that got washed into the pond with the rain?  Love to hear your thoughts.  Thanks, Rachel

    December 7, 2018 at 10:30 am

    • Hi Rachel,
      The only thing I can think is that the beavers were hauling the tree to their winter supply pile under the ice, though that would be highly unusual this time of year. Perhaps they stopped now and then to eat some bark, thereby depositing wood chips as they dragged the tree? You don’t say whether or not you saw the tree itself that they chewed down. Very odd signs!
      I’ve never seen any sign of their castoreum in the water. Their scent mounds, on which they rub it, are often adjacent to the water, so it’s not inconceivable that some was washed off the mound into the water. But as a rule, they aren’t marking at this time of year, so my guess would be it wasn’t castoreum causing the oil slick.

      December 7, 2018 at 1:43 pm

      • Cindy

        After a beaver brings down a tree, it “sections” it into manageable pieces. So every 4’ or so is another small pile of chips. Maybe moving the sections dragged the piles into a bit of a path. Or maybe it had to cut smaller sections to fit down an ice hole? If it was just stopping to eat, there wouldn’t be chips, right? Just sticks with no bark. So many interesting mysteries to decipher! Thanks Mary, for being such a great resource!

        December 7, 2018 at 5:51 pm

  36. Karen Eger

    I missed the answer to this one and really am curious as I see this every year and know the pond well and can’t imagine there are so many springs. Could you send a link to the answer please?

    Karen Eger

    Sent from my iPad


    December 10, 2018 at 7:16 pm

    • Hi Karen,
      The true answer is that I don’t know for sure. Possibly springs are the origin of such openings, as many people have observed them, but certainly otters take advantage of them, if they don’t actually make them themselves! If you read all the comments on this post, you’ll know as much as I do about the formation of these holes!

      December 10, 2018 at 8:02 pm

      • Karen McCarthy Eger

        Ah…I occasionally see an otter in this pond but not so often, beavers never though I am sure they pass through. I call these Ice Brittle Stars after the echinoderms.

        December 14, 2018 at 9:09 pm

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