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Lots of comments about the pinging, cracking, and noises on the ice. That is a sign that the ice is still freezing and expanding. Those noises are a sign that the ice is safe if thick enough. Deer Creek is famous for singing to you all day. Wait till a pressure ridge forms within a few feet of you, then it really gets fun. Sounds like Jordanelle is doing some of hte same things. When it stops popping, pinging and groaning, that is when you need to worry !!!
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I think it's a little more complex than that. Yes, H[#000000][size 1]2[/size][/#000000]0 expands as it changes from liquid to solid. Then, as an ice, it behaves with temperature changes much as other solids/liquids do. As temps drop, it condenses, and as temps rise, it expands. So, daytime rising temps can actually cause the ice to expand, causing great pressure, which can result in the pings and bongs.
One cause of pressures ridges is the day/night expansion/contraction action. Once there is a stable layer of ice on the top of the water, ice crystals forming on the bottom side of that are not what creates the significant lateral pressure. Rather, it is the rising temps during the day expanding the ice, with cooling temps at night contracting the ice, and new ice forming in any cracks. Then, when the ice expands once again due to daytime temps and solar radiation, it has to give somewhere - either at the shore, or by buckling along a ridge. This is why pressure ridges are more pronounced on large bodies where there is more expansion/contraction movement do to scale, or bodies with cliffs on either side where the ice is unable to creep up the shore.
I agree though, singing ice generally is a sign of solid ice. Rotten ice, or ice that can otherwise easily expand into gaps and soft spots will not sing as much, if at all. But, if temps are stable, and ice is stable, it won't sing, but that still doesn't mean it isn't safe.
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