Until then, isn't speculation fun?

Mike,
I wasn't speculating on the composition of the disappearing chunks; I agree they're probably ice.

I was speculating on the source of the disappearing chunks; that maybe they were scrapped off from the part that you're now talking about.

As I said, "I'm wondering if the scraped white surfaces are the exposed top of a large mass of ice...."
That is the part you're talking about isn't it; the large flat surfaces at the top of the trenches?
The ones where I said, "That left-handed semi-circular area near the top of the left trench looks more like wetted soil...."
Do you see what I'm trying to describe?
...also....
Do you see the "moved" pebble?

confused

Pyrolysis creates reduced carbon! ...Time for the next step in our evolutionary symbiosis with fire.