Needle Ice

Needle Ice

I went up to Indian River Falls today and noticed a number of small streams that were still flowing with little ice (while others, sometimes larger streams, were frozen solid). I think the free flowing water must have come out of the ground at a temperature well above freezing and a flow rate such that, despite the cold temperatures, the stream stayed relatively ice free for a while. On one such stream I noticed what were probably the largest needle ice formations I have ever seen. They were at least 6-9 inches tall and seemed to have grown out of the silt/clay that made up part of the stream bed. It was interesting to see the clear layering. I am guessing they represent a cycle of night/day or warmer/cooler, but I am not sure.

I’m not sure how these ice formations are created, but a little internet research indicated that it involves hydrostatic pressure from ground water pushing up the ice. It’s unclear to me why/how that action would be working in this case, since the surface water is right next to the ice formations.

About matt goff

I am an aspiring naturalist who seeks to learn all that I can about the more-than-human aspects of this place that is my home.
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1 Response to Needle Ice

  1. Bob says:

    Hi Matt,
    Cool. Yeah, I’d only seen the needle ice in Sitka until this past fall when I saw some up here in Fairbanks but I think it generally forms when there’s a combination of high soil moisture content and organic / silty soil pretty much like that bank. It’s kind of like frost heave where the water moves to the freezing front but since the soils in Sitka are so fine and also saturated most of the time all that water wicks up to the ground surface pretty easily. With the super cold temperatures last week the heat flux out of the ground was really high, driving the extreme growth.

    When they talk about pingos (they look like a volcano but are all ice) they talk about open and closed systems. Open ones have a nearby groundwater source and closed ones usually form in old, drained, lake depressions. The ice at this stream seems like open system needle ice with the water source so close. That’s pretty cool.

    A science writer from UAF wrote a book a couple years ago about permafrost and frozen ground. I haven’t read it but I hear it’s pretty interesting.
    Neil Davis Permafrost Book

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