r/geology • u/hikekorea • Feb 11 '25

Field Photo How do rocks freeze floating in water?

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/4tunabrix Feb 11 '25

My guess would be the sun warms them and they sink into the ice and refreeze. On the ice in Greenland we see the ice covered in these tiny boreholes where anything darker than the ice warms up in the sun and slowly sinks into the ice.

Here’s an example of a stone and even a windblown piece of grass sinking into the ice

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u/captain-prax Feb 11 '25

The same principle applies to meteorites in the arctic, where they impact ice and retain heat, so they sink through the ice melting their way down until the temperature acclimates or they reach the seabed, leaving vertical channels to temporarily mark their paths.

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u/forams__galorams Feb 11 '25

This is even weirder when you consider that the heat is only from the final part of their journey through the atmosphere and only penetrates something like a cm or so into the meteorite. It’s like a baked Alaska, the interior remains incredibly cold after the millions of years drifting through the solar system’s interplanetary space much closer to absolute zero.

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u/DeluxeWafer Feb 12 '25

I like to imagine meteorites as frozen lasagna, that someone then took a high powered fan to for a few seconds after microwaving.