Friday, November 7, 2008

Ice Breccia?

I found a little ice while driving into the field the other day, and being the first one on the road in the early morning, all the ice was intact from the overnight freeze.
This frozen pond was easy enough to go around, although I did manage to crack the ice a little while just barely skirting the right side.
This larger puddle was an entirely different story. The puddle straddles the entire road, and going off to either side would require driving into deep mud. The picture above shows what the muddy puddle looked like after I went right through the middle of it. I couldn't really see the thin coating of brownish ice over this pond, until I drove into it and heard it cracking (although it was cold, I had the window down). Some intact ice was left in a few places around the edge, notably on the far side.
The broken, angular ice fragments swirled around the muddy, somewhat turbulent water of the puddle - in an irregular to sub-circular, mostly clockwise, fashion. [The water wasn't at all turbulent, but just barely flowing beneath the ice, until I drove through and stirred things up.]
Then, some of the ice fragments washed towards shore on the side closest to me, forming a kind of ice breccia with angular ice fragments in a very fine-grained, muddy matrix. While out in the water, the fragments are matrix-supported. As they pile up on shore, they are more like a clast-supported breccia, but the watery matrix is gone, and the fragments are just resting on each other and on the grainy, muddy substrate, waiting for the sun to melt them.

The ice was all gone when I came back through later in the day.

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