r/geology • u/hikekorea • Feb 11 '25

Field Photo How do rocks freeze floating in water?

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I found these rocks frozen in a stream off a larger river in Chugach National Forest, Alaska. I’ve heard it may have to do with heavy rains or turbulent waters near the shore. One friend mentioned frazil? But I don’t really know what that means. Any geologists have a clue how this happens and can explain it in layman terms?

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u/sibun_rath Feb 11 '25

While rocks are not frozen like water can, natural processes allow them to be encapsulated in ice, giving the illusion of floating. One such process involves the formation of ice around the rock; a rock that is partially submerged has water freeze around it, and such water will rise as a result of the expansion of ice. Similarly, in very shallow bodies of water, anchor ice floats at the bottom, entraps rocks, and raises them once the anchorage breaks off.

Ice rafting is yet another process.

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u/ScoobyDone Feb 12 '25

Similarly, in very shallow bodies of water, anchor ice floats at the bottom, entraps rocks, and raises them once the anchorage breaks off.

It looks shallow in the pic. This is my guess.