Ice Tendrils "Growing" in Clay?

Factual Questions
1

I was taking a walk with Mrs. Hermitian when I noticed something in the clay ditch on the side of the road. It looked like hundreds of little thin tendrils of ice had grown out of the clay. However, it looks like they started growing from slightly below the surface of the clay because there was a 2-4 mm layer of clay on top of them. They were in patches.

I had my digital camera with me, so I took a few pictures of them. See them here

It may be hard to see this from the picture, but they are thick bunches of tiny little ice tubes about 1-1.5 mm thick.
I have two questions.

  1. By what process does this strange formation form?

  2. I saw them at about 6PM. The high for the day was around 42F. It was currently around 38F. How could it have survived the day?

2

I can’t quite tell from those pictures – are those bundles made up of long thin strands of ice, like icicles or something? Or are they something completely different?

If they are icicles, maybe they grew from tiny droplets running down into cracks in the clay and slowly freezing together?

3

Clay minerals (the inorganic part of clay soils) have an extremely complex structure, and will often act as a “template” on which other molecules/crystals will grow. (A good geologist can explain this in better terms than my limited knowledge will permit.) It may very well be that that template capability is what caused the ice crystals to grow as you describe.